Tanker Familiarization Course
(IMO Model 1.01 2000 Edition)
The material is arranged under nine main headings:
- Characteristics of cargoes
- Toxicity and other hazards
- Hazard control
- Safety equipment and protection personnel
- Pollution prevention
- Emergency operations
- Cargo equipment
- Cargo operations
The course material reflects the mandatory minimum requirements for officers and ratings as specified in regulation V/1 of the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers, 1995 (STCW 1995).
The texts used as reference throughout the course are:
International Safety Guide for Oil Tankers and Terminals
Captain C. Baptist, Tanker Handbook for Deck Officers
International Chamber of Shipping, Tanker Safety Guide (Chemicals)
M. Grey, Chemical/Parcel Tankers
B. Bengtsson, Sea Transport of Liquid Chemicals in Bulk
ICS/OCIMF/IAPH/INTERTANKO/CEFIC/SIGTTO, Ship/Shore safety Check List Guidelines
International Chamber of Shipping, Tanker Safety Guide (Liquefied Gas)
SIGTTO. Liquefied Gas Handling Principles on Ships and Terminals
R. Ffooks, Gas Carriers
T.W.V.Woolcott, Liquefied Petroleum Gas Tanker Practice
International Convention for the Safety of Life at Sea, 1974 (SOLAS 1974), as amended International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW 1978/1995)
International Convention for the Prevention of Pollution from Ships, 1973/78 (MARPOL)
Regulations for the Prevention of Pollution by Oil (Annex I of MARPOL)
Regulations for the Control of Pollution by Noxious Liquid Substances in Bulk (Annex II of MARPOL)
Regulations for the Prevention of Air Pollution from Ships (Annex VI of MARPOL)
Medical First Aid Guide for Use in Accidents Involving Dangerous Goods
Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (BCH Code), as amended
International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (IBC Code), as amended
Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, as amended (GC Code)
International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, as amended (IGC Code)
Guidelines for the Development of Shipboards Oil Pollution Emergency Plans
And the booklets published by the International Chamber of Shipping:
Safety in Oil Tankers
Safety in Chemical Tankers
Safety in Liquefied Gas Tankers
1.1. THE COURSE
1.1.1 This tanker familiarization course comprises three main parts. These are the basic understanding of the characteristics of oils, chemicals and liquefied gases; personnel safety and pollution prevention; and general shipboard cargo-handling system.
The first part covers the proprieties and associated hazards related to the cargoes.
The second part covers the means and measures to control the hazards and to prevent pollution, for the protection of personnel and the environment.
The third part provides a general overview of cargo-handling equipment and operations on board tankers.
1- The background for and the purpose of the course as:
-the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers, as amended in 1995 (STCW 1995), which contains mandatory minimum requirements for training and qualifications of masters, officers and ratings of tankers
2- this trtaining is divided into two levels:
level 1: a tanker familiarization course, or under an approved seagoing service, for
officers and ratings assigned specific duties and responsibilities related to cargo or cargo equipment on tankers;
level 2: a specialized (advanced) training programme for masters, chief engineer
officers, chief mates, second engineer officers and any person with immediate responsibility for loading, discharging and care in transit or handling of cargo on oil tanker, chemical tanker or gas tanker on which they serve
3- this course covers the requirements for level 1 training required by STCW 1995, Reg. V/1(1.2)
Regulation V/1 STCW-95 Convention provides necessary background, but general view of the requirements for training and qualifications of personnel on tankers is illustrated with the next diagram:
1.1.2 Personnel on tankers should at least have attended an approved shore-based fire-fighting course and the training required by Reg. VI/1 of STCW 1995.
1.1. DEVELOPMENT OF TANKERS
1.2.1 Important stages in the development of tankers and oil shipping
- carriage of oil in barrels in conventional cargo ships
- construction of vessels to carry oil in bulk
- use of longitudinal divisions and transverse bulkhead to form tanks
- location of machinery aft
- increase in size to VLCCs and ULCCs
- transportation of liquefied gas and chemicals in bulk
- pollution problems and explosion/fire hazard leading to international controls
- the development of SOLAS and MARPOL
- increasing use of training to improve safety and reduce pollution
- the STCW Convention and Chapter V of the Convention
- the development of double-hull tankers
- the implementation of the International safety Management (ISM) code
Important stages in the development of bulk chemical shipping
- sea transport of chemicals started with the chemical industries rapid growth in the years after World War Two
- at first chemicals were transported in bottles or drums on dry cargo ships; larger quantities were shipped in bulk in the deep tanks on these ships
- as the world’s demand for chemicals increased, the need for a new type of seagoing ship became evident
- the first chemical tankers were converted war-built American oil tankers (T2 tankers)
- conversion work usually included
adding bulkheads to provide more and smaller tanks
extending the line system
installing additional cargo pumps
- the first conversion of this type was done in 1948 on the R.E. Wilson, of 9073 tons gross tonnage
- in addition to these converted, relatively big chemical carriers, smaller tankers specially designed and constructed for the carriage of “acids” – e.g. sulphuric acid, were built during the early 1950s, the cargo tanks of which were made of special alloy steel, strengthened for cargo densities up to 2.0 kg/1
- in order to carry chemicals of high purity and sensitive to contamination, coating techniques were developed for cargo tanks of mild steel
- the first real chemical tanker specially designed for the carriage of liquid chemicals in bulk was the Norwegian M/T Lind, delivered in 1960; this was the first tanker equipped with stainless-steel cargo tanks
- a modern chemical tanker has a large number of cargo tanks and is designed for carriage of a wide variety of cargoes
- the cargo-tank section on these modern ships is normally divided into some stainless steel tanks and some coated mild-steel tanks, each of which is normally equipped with deepwell pumps and a separate piping system.
Important stages in the development of liquefied gas shipping
- gas shipping began in the late 1920s
- the earliest ships were designed to carry liquefied gas in pressure vessels at ambient temperature
- the first cargoes on the market were butane and propane
- development of refrigeration techniques and metals suitable for low temperature made it possible to carry liquefied gas at temperature lower then ambient
- around 1959, semi-pressurized ships entered the market and liquefied gas was now transported under lower pressure, which was made possible by lowering the temperature
- by 1963, fully refrigerated ships for LPG, LNG and certain chemical gases (such as butadiene) were in service, carrying cargo at atmospheric pressure.
1.2. TYPES OF CARGOES
1.3.1 “Oil” means petroleum in any form, including crude oil, fuel oil, sludge, oil refuse and refined products (Other then petrochemicals).
1.3.2 List of oils:
Asphalt solutions Gasoline blending stocks
Blending stocks Alkylates – fuel
Roofers flux Reformates
Straight run residue Polymer – fuel
Clarified Casinghead (natural)
Crude oil Automotive
Mixtures containing crude oil Aviation
Diesel oil Straight run
Fuel oil no. 4 Fuel oil no. 1(kerosene)
Fuel oil no. 5 Fuel oil no. 1-D
Fuel oil no. 6 Fuel oil no. 2
Residual fuel oil Fuel oil no. 2-D
Transformer oil Jet fuels
Aromatic oil (excluding vegetable oil) JP-1 (kerosene)
Lubricating oils and blending stocks JP-3
Mineral oil JP-4
Motor oil JP-5 (kerosene, heavy)
Penetrating oil Turbo fuel
Spindle oil Kerosene
Turbine oil Mineral spirit
Straight run Solvent
Flashed feed stocks Petroleum
Heartcut distillate oil
1.3.3 Crude petroleum as discharged at the well head is a mixture of a large number of different hydrocarbon molecules
1.3.4 “Hydrocarbons” is the common name for substances composed of only the elements hydrogen and carbon
1.3.5 The composition of petroleum depends on its source
1.3.6 The petroleum remaining after the removal of products such as methane is termed “crude oil”
1.3.7 General arrangement of tankers which carry bulk cargoes of:
1- crude oil Fig. 1.7
2- petroleum products Fig. 1.8
4- ore/oil Fig. 1.9
5- ore/bulk/oil Fig. 1.10-1.11
1.3.8 in general:
1- a chemical tanker is primarily designed for the carriage of dangerous chemicals in bulk
2- these chemicals are listed in the IMO Bulk Chemical Codes, for example:
Sodium hydroxide solution (caustic soda sol.)
Methyl alcohol (methanol)
Toluene diisocyanate (TDI)
Methyl ethyl ketone (MEK)
Carbon tetrachloride (CTC)
Ethylene dichloride (EDC)
3- In addition to the cargoes listed in the Codes, chemical tankers may carry a wide variety of other liquid products which would normally be considered to be unrelated to chemicals, such as:
Animal and vegetable oils
Clean petroleum products and lubricating oils
1.3.9 A chemical tanker may carry dangerous chemicals and all products tanker cargoes, but that a product tanker is limited to carry products and chemicals which are not identified in the Codes as dangerous
1.3.10 Cargoes in chemical tankers may be divided into 4 groups as follows:
2- alcohols and carbohydrates
3- vegetable and animal oils and fats
4- inorganic chemicals
1.3.11 Petrochemicals are organic products derived wholly or partly from crude oil, natural gas or coal
1.3.12 Examples of petrochemicals:
3- intermediates or refined products
1.3.13 The group of alcohols and carbohydrates includes products which may be produced by fermentation, such as:
1.3.14 Vegetable and animal oils and fats are products derived from seeds of plants and from the fat of animals, including fish
1.3.15 Examples of vegetable and animal oils and fats:
1- soya bean oil
2- cottonseed oil
4- lard and lard oil
5- beef and mutton tallow
6- whale oil
7- sardine oil
8- cod oil
1.3.16 Inorganic chemicals are products which are not of organic origin
1.3.17 Examples of inorganic chemicals are:
1- sulphuric acid
2- phosphoric acid
3- nitric acid
4- caustic soda
1.3.18 Most cargoes in chemical tankers belong to the group “petrochemicals”
1.3.19 Chemical tankers may also carry petroleum products such as those normally carried in oil tankers
1.3.20 Chemical tankers may be engaged in “dedicated” or “parcel” trades
1.3.21 Dedicated service usually means that the tanker is dedicated for a certain type of chemicals, transporting the same type of cargo on each voyage
1.3.22 A chemical tanker engaged in parcel service moves a variety small lots of chemicals between a number of ports. Chemical tanker is a cargo ship constructed or adapted and used for the carriage in bulk of any liquid product listed in Chapter 17 of the IBC Code.
Liquefied gas cargo
1.3.23 For economical marine transportation, gas is carried in a liquefied state. As a liquid, the volume to weight ratio at atmospheric pressure is in the range of 650 times less than in the gaseous state. Even so, the relative densities are low and vary between 0.42 (methane) and 0.97 (VCM).
Generally speaking, a liquefied gas is the liquid form of a substance which at ambient temperature and atmospheric pressure would be a gas. Definition: A liquid which has a sturated vapour pressure exceeding 2.8 bar absolute at 37.80C and certain other substances specified in the Gas Codes.
1.3.24 Cargoes transported by gas tankers are listed in IMO’s Gas Carriers Code
Cargo Ship Type
Ammonia, anhydrous 2G/2PG
Butane/propane mixtures 2G/2PG
Chlorine 1 G
Diethyl ether 2G/2PG
Ethane 2 G
Ethyl chloride 2G/2PG
Ethylene 2 G
Ethylene oxide 2G/2PG
Ethylene oxide/propylene oxide mixture
(with ethylene oxide content less than 30% by weight) 2G/2PG
Methane 2 G
Methylacetylene/propadiene mixture 2G/2PG
Methyl bromide 1 G
Methyl chloride 2G/2PG
Nitrogen 3 G
Propylene oxide 2G/2PG
Refrigerant gases 3 G
Sulphur oxide 1 G
Vinyl chloride 2G/2PG
Vinyl ethyl ether 2G/2PG
Vinylidene chloride 2G/2PG
1.3.25 These cargoes can be devided into the following four groups:
1- liquefied natural gas, LNG
2- liquefied petroleum gas, LPG
3- liquefied ethylene gas, LEG
4- chemical gases and certain other substances
1.3.26 LNG is liquefied natural gas from which impurities are removed
1.3.27 The principal constituent of LNG is methane
1.3.28 “Liquefied petroleum gas”-LPG- is a common name for petroleum gases, mainly propane and butane
1.3.29 LPG is produced from two sources:
1- from crude oil processing in refineries, or as a by-product of chemical plants
2- from natural gas streams or from crude oil at or close to production points (wells/platforms)
1.3.30 Liquefied ethylene gas – LEG – is produced by “cracking” of LPG
1.3.31 Chemical gases are a group of liquefied gases produced through a chemical process
1.3.32 Chlorine, ammonia and vinyl chloride monomer (VCM) as examples of chemical gases
1.3.33 Certain other substances in the “borderland” between liquefied gas and chemicals are carried on gas tankers
1.3.34 Acetaldehyde and propylene oxide as examples of such cargoes
1.3.35 The two methods by which gas can be liquefied as:
1- liquefaction by removal of heat
2- liquefaction by pressurizing
1.3.36 Liquefaction of gas cargoes on ships – other than fully pressurized ships – is done by removal of heat
1.3.37 The heat to be removed from the cargo is called “latent heat of condensation”
Gas carrier is a cargo ships constructed or adapted and used for the carriage in bulk of any liquefied gas or other products listed in the table of chapter 19 IGC Code.
1.4 TANKER TERMINOLOGY
The fundamental temperature scale with its zero at absolute zero and expressed either in kelvin or degrees Rankine. One kelvin is equal to one Celsius degree or one centigrade; one Rankine degree is equal to one Fahrenheit degree. To convert Celsius to kelvin, add 273.1 (e.g. 5oC = 278.1oK)
To convert Fahrenheit to Rankine, add 459.6 (e.g. 5oF = 464.6oR)
0oK = 0oR = 273.1oC = -459.6oF
Absolute temperatures are used in most thermdynamic tables, charts and calculations. In the SI system of measurement, Centigrade temperature units (i.e. oC or oK) are used.
The temperature at which the volume of a gas theoretically becomes zero and all thermal
motion ceases. Generally accepted as being -273.16 °C or-459.69 °F.
Absorption oils (scrubbing oil, wash oil)
Generally refer to a moderately high boiling oil distilled from petroleum (i.e., a gas oil) or coal tar, and used for separating desired gases or vapors by dissolving them from some mixture.
Thus, the vapours of natural gasoline are separated from certain natural gases by passage up a tower through which a stream of an absorption oil is passed. Benzene, toluene, and xylene are recovered from coal gas by a similar procedure.
Any chemical compound containing hydrogen, capable of being replaced by positive elements or radicals to form salts. Acid and acid solution turn litmus paper red. They have a pH value from less than 7.0 (neutral) down to 0 (extremely acid). A pH of 2.0 is concentrated acid.
The number of grams of potassium hydroxide neutralized by the free acids present in one gram of oil.
An acid solution with a pH below 7.0 (neutral).
Across’ cargo tanks
Tanks are usually constructed in sets of three transversely and are numbered from forward, e.g. the foremost three tanks are called ‘One Port’ (1P), ‘One Centre’ (1C), and ‘One Starboard’ (1S). The three tanks as set are known as ‘One Across’ (1X). Thus to separate the cargo in 1X from 2X the master valves (see M.V.) in the lines at the athwartships bulkhead between the tanks must be closed.
Acute toxic effect
The effect on man of a single exposure of short duration to high concentrations of toxic comhound or toxic vapour.
Without transfer of heat. Adiabatic expansion is volume change in a liquid or gas with no heat loss or gain involved.
The condition in which a soil or deposit clings to a surface and cannot be easily removed by normal water flow, flushing,or mechanical means.
A separation area used to maintain adjacent areas at a pressure differential; e.g. an electric motor room airiock on a gas carrier is used to maintain pressure segregation between a gas-dangerous zone on the open weather deck and the pressurized gas-safe motor room.
A fire-fighiting foam effective against many water-soluble cargoes. It is also effective against many non-water-soluble cargoes.
Any compound having marked basic properties. Alkalis and alkaline solutions turn litmus paper blue. They have a pH value above 7.0 (neutral) up to 14.0 (extremely alkaline). These include the oxides and hydroxides of barium, calcium, magnesium, and sodium. Hydroxides are strong alkalis.
An alkali solution with a pH above 7.0 (neutral).
Normal atmosheric temperatures up to the range of 38oC (100oF).
A material whose structure is irregular and formless.
A total loss of feeling and consciousness or the loss of power or feeling over a limited area of skin.
ChemicaIs which produce anaesthesia.
A substance added to a petroleum product to raise its electrical conductivity above 100 picosiemens/metre (pS/m) to prevent accumulation of static electricity.
API gravity scale
A standard scale agreed between the American Petroleum Institute (API), the U.S. Bureau of Standards and the Bureau of Mines in 1921 for measuring the specific gravity of oil expressed in terms of degrees. There is a direct relation between API degrees and the weight of oils. The lower the API degree, the higher the specific gravity and weight of oil. For ex. API @ 60oF=0 : Sp. Gr. 60/60oF= 1.0760 Pounds Per US Gal. @ 60oF=8.962
API @ 60oF=10 : Sp. Gr. 60/60oF= 1.0000 Pounds Per US Gal. @ 60oF=8.328.
Equipment of a design that has been tested and approved by an appropriate authority such as a Government or classification society. The authority should have certified the equipment as safe for use in a specified hazardous atmosphere.
Indicating that the compound is in solution in water.
The condition arising when the blood is deprived of an adequate supply of oxygen, so that loss ousness may follow.
A gas or vapour which, when inhaled, leads to asphyxia.
A form of steel particularly susceptible to chloride ion attack, especially during hydrochloric acid cleaning processes. Non-magnetic steel. Also called stainless steel.
The ignition of a combustible material without initiation by a spark or flame, when the material has been raised to a temperature at which self-sustaining combustion occurs.
Auto-ignition temperature (Autogenous ignition temperature)
The lowest temperature to which a solid, liquid or gas requires to be raised to cause self-sustained combustion without initiation by a spark, flame or other source of ignition.
Avogadro's Hypothesis. Equal volumes of all gases contain equal numbers of molecules under the same conditions of temperature and pressure.
The forceful flushing of system in which the flow is counter-current to the normal operation flow path.
That which is capable of being decomposed by living matter, especially bacteria.
Boiling Liquid Expanding Vapour Explosion. Associated with the mpture under fire conditions of a pressure vessel containing liquefied gas.
Areas of the tank not reached by the tank washing machine water jets.
Oxidized oils; base oils; thickened oils; polymerized oils. Vegetable and animal oils which have been heated and agitated a current of air oxygen. They are partially oxidized, deodorized and polymerized by the treatment, and are increased in density, viscosity and drying power. Important blown oils are castor, linseed, rape, whale and fish oils.
Vapour produced above the surface of a boiling liquid.
The temperature at which the vapour pressure of a liquid is equal to atmospheric pressure. Boiling points, as quoted on the data sheets, are correct at a pressure of 760 mmHg, unless indicated to the contrary.
Some liquids which are mixtures, OR which contain impurities, boil over a range of temperatures known as the boiling range. When this occurs, the range will be stated on the relevant data sheet. The lower temperature is that at which the liquid starts to boil.
The connecting together of metal parts to ensure electrical continuity.
A pump used to increase the discharge pressure from another pump (e.g. a main cargo pump).
Cargo carried in cargo tanks and not shipped in drums, containers or packages.
Liquid petroleum does not burn, petroleum vapor burns. Danger increases according to how quickly the product vaporizes. The lower the temperature at which a petroleum evaporates, the more dangerous it is.
‘Butterfly’ valve type
Automatic valves are often of the ‘butterfly’ type; these are circular valves which turn on a central spindle. When open the plate is parallel to the pipe direction and the oil flows past it; when close the plate turns across the pipe, thus prevention the flow of oil.
The amount of heat necessary to rise one gram of water one degree centigrade at constant pressure of one standard atmosphere.
Canister-type breathing apparatus
A respirator consisting of mask and replaceable canister filter through which toxic air is drawn by the breathing effort of the wearer and the toxic elements are absorbed. A filter dedicated to the specific toxic contaminant gas must be used. May be referred to as "cartridge" or "filter" respirator.
That part of the ship which contains the cargo-containment system, cargo pump and compressor rooms, and includes the full beam deck area over the length of the ship above the cargo containment. Where fitted, cofferdams, ballast or void spaces at the after end of the aftermost hold space or the forward end of the forwardmost hold space are excluded from the cargo area.
The maintaintaining of the cargo quantity without undue loss, of the cargo tank pressure within its n limits, and of the desired cargo temperature.
Cargo containment system
The arrangement for containment of cargo, including, where fitted, a primary and secondary barrier, associated insulation, interbarrier spaces and structure required for the support of elements.
The loading, discharging and transferring of bulk liquid cargo.
Cascade reliquefaction cycle
A process whereby vapour boil-off from cargo tanks is condensed in a cargo condenser in which the coolant is an evaporating refrigerant such as Freon 22. The evaporating refrigerant then passed through a coventional seawater-cooled condenser.
A substance that starts a reaction or changes its speed without being itself chemically changed. A catalyst which reduces the speed of a reaction is known as a negative catalyst.
A substance which by its presence alters the velocity of a reaction and may be recovered unaltered in nature at the end of the reaction.
The prevention of corrosion by electrochemical techniques. On tankers it may be applied either externally to the hull or internally to the surfaces of tanks. At terminals, it is frequently applied to steel piles and fender panels.
Whenused alone, the term usually alludes to caustic soda, sodium hydroxide.
A process occurring within the impeller of a centrifugal pump when pressure at the inlet to the limpeller falls below that of the vapour pressure of the liquid being pumped. Bubbles of vapour which are formed collapse with considerable impulse force in the higher-pressure regions of the impeller. Significant damage can occur to the impeller surfaces.
The European Council of Chemical Industries.
One one-hundredth of a stoke. A stoke is the kinematic unit of viscosity in poises divided by the density of the fluid in grams per cubic centimeter, both measured at the same temperature.
Certified gas-free means that a tank, compartment or container has been tested using an approved testing instrument and proved to be sufficiently free, at the time of the test, of toxic or explosive gases for a specified purpose, such as hot work, by an authorized person (usually a chemist from shore) and that a certificate to this effect has been issued. If an authorized person is not available, the test should be carried out by the Master or his appointed deputy and the certificate will take the form of an entry in the tanker's logbook.
Certificate of Fitness (CoF)
A certificate issued by the Administration of a country confirming that the structure, equipment, fittings, arrangements and materials used in the construction of a gas carrier are in compliance with the relevant IMO Gas Codes. Such certification may be issued on behalf of the Administration by approved Classification Societies.
Chemical absorption detector
An instrument used for the detection of gases or vapours working on the principle of a reaction occuring between the gas being sampled and a chemical agent in the apparatus.
Chronic toxic effect
The cumulative effect on man of prolonged exposures to low concentrations or of int exposures to higher concentrations of a toxic compound or toxic vapour.
Any product carried in commerce hich by its physical or chemical characteristics would not contaminate a following cargo and which can be easily removed by water flushing.
A blend of surface-active agents, emulsifiers and dispersants in a solvent solution used to remove soils from a surface.
A blend of surface-active agents, emulsifiers and dispersants in a water solution to remove soils from a surface.
Oil remaining on the walls of a pipe or on the surfaces of tank interiors after the bulk of has been removed.
Closed gauging system (closed ullaging)
A system whereby the contents of a tank can be measured by means of a device penetrates the tank, but which is part of a closed system and keeps tank contents froi released. Examples are the float-type systems, electronic probe, magnetic probe and sight glass.
Coefficient of cubical expansion
The fractional increase in volume for a 1 °C rise in temperature. The increase is 5/9 of| a 1 °F rise.
The isolating space between two adjacent steel bulkheads or decks. This space may I space or ballast space.
Work which cannot create a source of ignition.
Color shade equivalents
When carrying light distillate cargoes, knowing the approximate color shade equivalents is a valuable guide to the degree of cleanless which must be attained before a light distillate cargo may be loaded. The ideal cleaning of ship’s tanks and lines not cause any color change, or at most, a very minor one in the subsequent cargo to be carried. There are a few kind of color equivalents: T.A.G. ROBINSON, N.P.A. & A.S.T.M., SAYBOLT, etc.
Color sensitive cargoes
e.g. methanol, isopropyl alcohol, styrene monomer, fibre grade ethylene glycol etc.
A ship is designed to carry either petroleum cargoes or dry bulk cargoes.
Combustible-gas detector (explosive meter)
An instrument used to detect combustible hydrocarbon gases, generally using filament of a special metal to oxidize the gas catalytically and measure the gas coik as a percentage of its Lower Flammable Limit. No single instrument is suitab combustible vapours.
Combustible (also referred to as "flammable")
Capable of being ignited and of burning. For the purposes of these guidance notes,^ "combustible" and "flammable" are synonymous.
Combustible gas indicator
An instrument for measuring the comosition of hydrocarbon gas/air mixtures, usually giving the result as a percentage of the lower flammable limit (LFL).
The ability of two or more compounds to exist in close and permanent association.
A substance in which two or more elements are chemically combined, as opposed to a mixture in which elements or compounds are only mechanically intermingled.
The conversion of iron, steel and other alloys and metals into oxides due to theaction of air and water or both. The minor components present in the air or water are important factors in the rate of corrosion and the kind of corrosion products. A minor component such as carbon dioxide in air and water can cause serious corrosion, but contaminants intriduced by all types of air and water pollution usually accelerate corrosion. Salts, as in seawater, are serious causes of corosion. Sulfur in fuel isalso an important source of corrosion, so that removal treatments are common.
Liquids which corrode normal constructional materials at an excessive rate. Usuall cause serious damage to human tissue and to the eyes.
The temperature above which a gas cannot be liquefied by pressure alone.
The pressure of a saturated vapour at the critical temperature, i.e. the pressure) cause liquefaction at that
The study of the behaviour of matter at very low temperatures.
Athwartships tank lines joining the main line are known as crossover lines and the crossover valves separate the main lines from each other as well as separating individuals tanks. Thus 2P can be separated from 2C by a crossover valve. Briefly, master valve separate separates in a fore-and-aft direction and crossovers in the athwartships direction.
The study of the behaviour of matter at very low temperatures.
A bluish discoloration of the skin, particularly about the face and extremities, which usually occurs when the blood is not properly oxygenated by the lungs, and manifests itself particularly in the area of the mouth and ears.
A material formed in such a manner that its structure is arranged in a regular, repeated and interlocked pattern.
Dalton's Law of Partial Pressures
The pressure exerted by a mixture of gases is equal to the sum of the separate pressures which each gas would exert if it alone occupied the whole volume.
An area on a tanker which, for the purposes of the installation and use of electrical equipment, is regarded as dangerous.
Dangerous cargo endorsement
Endorsement to a certificate of competency of a responsible officer for him to serve as such on a dangerous cargo carrier (i.e. oil or chemical or gas carrier).
Atype of centrifugal cargo pump commonly found on gas carriers. The prime mover, usually but not always an electric motor, is flange-mounted on top of the cargo tank and drives, through a long transmission shaft, the pump assembly located in the bottom of the tank. The discharge pipe surrounds the drive shaft and the bearings of the shaft are cooled and lubricated by the liquid being pumped.
A solvent-based or an alkaline water-based cleaner especially effective on heavy petroleum deposits.
A chemical surface active agent which breaks an emulsion, forcing droplets of the dispersed liquid or semi-solid to combine into larger drops which separate into a phase distinct from the original mixture.
The mass per unit volume of a substance at a standard temperature and pressure. In the metric system, measured in grams per cubic centimeter, when it is equal to specific gravity
An accumulation of unwanted materials in a system.
A synthetic cleansing agent resembling soap in its ability to emulsify oil and hold dirt, and containing surfactants which do not precipitate in hard water.
The temperature at which the water vapour present in a gas saturates the gas and begins to condense.
Direct line system
The system is common on VLCCs (very large crude carriers) as it facilitates quick loading and discharging, the cargo being natural unrefined oil. The shorter pipe lengths and the fewer bends ensure that there is less loss of pressure due to pipeline friction during both operations and when discharging the line to a pump provides better suction.
The system is a cheaper to construct than the ring main and require less maintenance. Leaks are minimized as there are fewer washing time is also considerably shortened. However, as there is no circular system lines can be often difficult to wash and simply has to flush lines from the tanks with sea water.
Any product carried in commerce which by its physical or chemical characteristics would contaminate a following cargo unless it is chemically cleaned.
Any materials added to a suspending medium to promote and maintain the separation of the individual, externely fine particles of solids or liquids which are usually of collodial size.
Each of the main tank pipelines has a counter part on deck and loading lines which lead vertically from the deck lines to the tank lines are as known as drop lines. Each main line has one or two drop lines and drop valves control the flow of oil in those lines.
During tank cleaning with a portable tank cleaning-type machine, the cleaning cycles are commenced at the top of the tank and periodically moved down in stages or «drops» at regular intervals of tank depth.
Organic liquids which tend to dry to hard solid upon exposure to air in a relatively short time. Equipment containing these products should be cleaned immediately after discharge.
Dry chemical powder
Aflame-inhibiting powder used in fire fighting.
Organic liquids which tend to dry to a hard solid upon exposure to air in a relatively short time. Equipment containing these products should be cleaned immediately after discharge.
Earthing (also referred to as ‘grounding’)
The electrical connection of equipment to the main body of the earth to ensure that it is at earth potential. On board ship the connection is made to the main metallic structure of the ship, which is at earth potential because of the conductivity of the sea.
A chemical surface active agent which produces a dispersion of one liquid or semi-solid in another in extremely small droplet size and renders the resultant mixture stable for relatively long periods of time.
A substantially permanent mixture of two or more liquids which do not normally dissokve in each other but which are held in suspension, one in the other. The suspension is usually stabilized by small amounts of additional substances knowns an emulsiiers. These modify the surface tension of the droplets to keep them from coalescing. Typical emulsions are milk, mayonnaise and such pharmaceutical preparations as cod-liver oil emulsion. Typical emulsifiers are egg yolk, casein and certain other proteins; soap; and surface active agents such as the quaternary ammonium compounds, sulfonated oils, and polyhydric alcohol esters and ethers.
Specific kinds of soaps include those from tallow, grease, fish oil and resin acids.
Referring to a process which is accompanied by absorption of heat.
Adocument issued by a responsible person permitting entry to a space or compartment during
Thermosetting resins based on the reactivity of the epoxide group.
The reactive epoxies can form a tight cross-linked polymer network, and are characterized by toughness, good adhesion, corrosion and chemical resistance, and good dielectric properties. Since their curing is by condensation, no extraneous or volatile product has to be taken care of, so that large castings can be made without bubbles or voids.
See "Combustible-gas indicator", but sometimes giving the result as a percentage of the lower explosive limit (LEL) or ppm.
Electrical equipment is defined and certified as explosion-proof (flame-proof) when it is enclosed in a case which is capable of withstanding the explosion within it of a hydrocarbon gas/air mixture or other specified flammable gas mixture. It must also prevent the ignition of such a mixture outside the case either by spark or flame from the internal explosion or as a result of the temperature rise of the case following the internal explosion. The equipment must operate at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby.
See “Flammable range”
Referring to a process which is accompanied by evolution of heat.
See "Flammable range".
The change of a liquid into a vapor, not necessarily by boiling. Usually such vapors are called gases.
A natural organic compopund which solidifies at or below 20oC, but otherwise similar to natural oils.
Filling density (for liquefied gases)
The "filling density" is defined as the percent ratio of the weight of the liquid gas in a tank to the weight of water the tank will hold at 15.56 °C (60 °F).
Filling ratio (for liquids)
That volume of a tank, expressed as a percentage of the total volume, which can be safely filled, having regard to the possible expansion of liquid.
The temperature at which a liquid continues to burn when ignited. This is always higher than flash point (20-25oC depend of kind of petroleum products).
A permeable matrix of metal, ceramic or other heat-resisting materials which can cool a deflagration flame and any following combustion products below the temperature required for the ignition of the unreacted flammable gas on the other side of the arrester.
A portable or fitted device incorporating one or more corrosion-resistant wire-woven fabrics of very small mesh used for preventing sparks from entering a tank or vent opening or, fora short time, preventing the passage of flame. (Not to be confused with a flame arrester, see Instructor Manual section 1.4)
Flammable (also referred to as ‘combustible’)
Capable of being ignited and of burning. For the purposes of these guidance notes, the terms "flammable" and "combustible" are synonymous.
It is possible to have a mixture containing so much or so little petroleum vapor that it cannot ignite. Mixtures which have reached these respectively have reached their Upper Flammable Limit (UFL) or Lower Flammable Limit (LFL). (Also known as the Upper or Lower Explosion Limit: UEL or LEL)
Flammable range (also referred to as ‘explosive range’)
The range of hydrocarbon gas concentrations in air between the lower and upper flamrnable (explosive) limits. (UFL-LFL). Mixtures within this range are capable of being ignited and of burning.
Flashlight (also referred to as ‘torch’)
A battery-operated hand lamp. An approved flashlight is one which is approved by a competent authority for use in a flammable atmosphere.
The lowest temperature at which a liquid gives off sufficient gas to form a flammable gas mixture near the surface of the liquid. It is measured in the laboratory in standard apparatus using a prescribed procedure.
Any substance in liquid form
Washing a surface with a forceful flow of a liquid, usually water, to remove loosened material or residual cleaning solutions in precleaning or after cleaning operations.
Foam (also referred to as ‘froth’)
An aerated solution which is used for fire prevention and fire fighting.
Foam concentrate (also referred to as ‘foam compound’)
The full-strength liquid that is received from the supplier, which is diluted and processed to produce foam.
The mixture produced by diluting foam concentrate with water before processing to make
The unrestricted fall of liquid into a tank.
Free flow system
On some VLCCs the main pipeline is not used for discharging. Gate valves are constructed in the tank bulkheads, and when these are opened the stern trim causes the oil to flow the aftermost tanks where direct lines to the cargo pumps are located. This is a very fast methodmof discharging and the tanks are also efficiently drained as the large bulkhead sluice valves permit the oil residue to readily flow aft.
Freezing point (melting point)
The temperatures at which the liquid stale of a substance is in equilibrium with the solid state, i.e. at a higher temperature the solid will melt and at a lower temperature the liquid will solidify. Freezing point and melting point may not always coincide, but they are sufficiently close to enable the difference between them to be ignored for the purpose of this Guide. (See "Supercooling")
This term is used to cover all vapour or vapour/air mixtures.
Gas absorption detector
An instrument used for the detection of gases or vapours which works on the principle of discolouring a chemical agent in the apparatus
The Codes for the Construction and Equipment of ships carrying liquefied gases in bulk, prepared and published by the International Maritime Organization.
Gas-dangerous space or zone
A space or zone within the cargo area which is not arranged or equipped in an approved manner to ensure its atmosphere is at all times maintained in a gas-safe condition, or an enclosed space outside the cargo area through which any piping passes which may contain liquid or gaseous products unless approved arrangements are installed to prevent any escape of product vapour into the atmosphere of that space.
A tank, compartment or container is gas-free when sufficient fresh air has been introduced into itto lower the level of any flammable, toxic, or inert gas to that required fora specific purpose, e.g. hot work, entry, etc.
Acertificate issued by an authorized responsible person confirming that, at the time of testing a lank, compartment or container, it was gas-free for a specific purpose.
The process of eliminating a hazardous or expolosive atmosphere from an enclosed area by ventilation, washing, or chemical cleaning.
A space not designated as a gas-dangerous space.
Gate cargo valve
Many manual valves are of the ‘gate’ type (sometimes known as ‘sluce valve’); a threaded spindle when turned, vertically moves a steel plate which is fitted in groves in the pipeline, thus opening or closing the valve.
Gauze screen (sometimes called "flame screen")
A portable or fitted device incorporating one or more corrosion-resistant wire-woven fabrics of very small mesh used for preventing sparks from entering an open deck hole, or FORA SHORT PERIOD OF TIME preventing the passage of flame, yet permitting the passage of gas.
A halogenated hydrocarbon previously used in fire fighting which inhibited flame propagation.
An articulated pipework arm used in terminals to connect shore pipework to ship manifold.
A general descriptive term for injurious effects on health that may be caused by chemicals.
A hazardous area is one in which vapour may be present continuously or intermittently in sufficient concentrations to create a flammable atmosphere or an atmosphere which is dangerous for personnel.
See "Hazardous area".
A general descriptive term for the danger to the health of personnel presented by soire chemicals.
There are three commonly used units of heat, namely the kilojoule (kJ), kilocalorie (kcal) and the British Thermal Unit (BTU).
The preffered SI unit is the kilojoule. It is the amount of heat, measured in Joules, required to raise the temperature of 1 kilogram of water by 1oC.
Heat of fusion
Quantity of heat required to effect a change of state of a substance from solid to liquid withoit change of temperature. (Latent heat of fusion).
Heat of vaporization
Quantity of heat required to effect a change of state of a substance from liquid to vapoi.' without change of temperature. (Latent heat of vaporization).
Surfaces which are concealed from the direct flow of a cleaning solution and as such do not receive the forceful cleaning effect desired. These areas often have to be spot cleaned.
The space enclosed by the ship's structure in which a cargo containment system is situated,
Work involving sources of ignition or temperature sufficiently high to cause the ignition of a flammable gas mixture. This includes any work requiring the use of welding, burning or soldering equipment, blow torches, some power-driven tools, portable electrical equipment which is not intrinsically safe or contained within an approved explosion-proof housing, sand-blasting equipment, or internal-combustion engines.
A document issued by a responsible person permitting specific hot work to be done during a specific time interval in a defined area.
Mass of water vapour present in unit volume of the atmosphere, usually measured as grams per cubic meter. It may also be expressed in terms of the actual pressure of the water vapour present.
White, snow-like, crystalline substance formed at certain pressures and temperatures by
hydrocarbons containing water.
An additive to certain liquefied gases that is capable of depressing the temperature at which
hydrates begin to form. Typical depressants are methanol, ethanol, isopropyi alcohol, etc.
A gas composed entirely of hydrocarbons.
The decomposition of a compound by the agency of water (H-OH) into two parts, one part then combining with hydrogen (H) from the water and the other part with the hydroxyl (OH).
A gas composed entirely of by hydrocarbons. Hydrocarbons are an organic compounds consisting of Hydrogen and Carbon.
The tendency of a substance to absorb moisture from the air.
International Association of Classification Societies.
International Association of Ports and Harbours.
International Chamber of Shipping.
International Electrotechnical Commission.
The lowest temperature at which combustion (with fire) can occur spontaneously without any heat supply from outside.
International Maritime Organization, the United Nations specialized agency dealing with
A spark of sufficient temperature and energy to ignite a flammable vapour.
A condition in which the oxygen content throughout the atmosphere of a tank has been
reduced to 8% or less by volume by addition of inert gas.
An electrical instrument for detecting the boundary between oil and water.
A gas or a mixture of gases, such as flue gas, containing insufficient oxygen to support the
combustion of hydrocarbons.
Inert gas distribution system
All piping, valves and associated fittings to distribute inert gas from the gas plant to cargo tanks, to vent gases to atmosphere and to protect tanks against excessive pressure or
Inert gas plant
All equipment specially fitted to supply, cool, clean, pressurize, monitor and control delivery of
inert gas to cargo tank systems.
Inert gas system (IGS)
An inert gas plant and inert gas distribution system together with means for preventing bacK-flow of cargo gases to the machinery spaces, fixed and portable measuring instruments and control devices.
The introduction of inert gas into a tank with the object of attaining the inert condition.
The act of introducing a substance into the body via the digestive system.
A chemical to which an inhibitor or additive has been added.
A substance used to prevent any chemical reaction.
A flanged joint incorporating an insulating gasket, sleeves and washers to prevent electrical continuity between pipelines, hose strings or loading arms.
The space between a primary and a secondary barrier of a cargo containment system, whether or not completely or partially occupied by insulation or other material.
An electrical instrument for detecting the boundary between oil and water.
International Association of Independent Tanker Owners.
An electrical circuit or part of a circuit is intrinsically safe if any spark or thermal effect produced normally (i.e. by breaking or closing the circuit) or accidentally (e.g. by short circuit or earth fault) is incapable, under prescribed test conditions, of igniting a prescribed gas mixture.
A liquid which, on direct contact with the eyes or skin, will cause, injury, burns or severe irritation.
A vapour which will cause irritation of the eyes, nose, throat and respiratory tract. Such vapours generally are immediately evident.
International Safety Guide for Oil Tankers and Terminals. Published jointly by ICS, OCIMF andlAPH.
When a gas passes through a series of pressure and/or volume variations without change of temperature, the changes are called "isothermal".
The heat required to cause a change in phase of a substance from solid to liquid (latent heat of fusion) or from liquid to vapour (latent heat of vaporization). These phase changes for single-component systems occur without change of temperature at the melting point and the boiling point respectively.
A liquid which has a saturated vapour pressure exceeding 2.8 bar absolute at 37.8 °C and certain other substances specified in the IMO Codes.
Liquefied Natural Gas, the principal constituent of which is methane.
This term refers to the process of demulsifying and settling a cleaning slop to separate the oil and water phases. After separation, the oil-free water phase is discharged overboard and the oil phase is saved and combined with the new cargo of oil.
The loading of cargo or ballast "over the top" through an open-ended pipe or by means of an open-ended hose entering a tank through a hatch or other deck opening, resulting in the free fall of liquid.
Lower flammable limit (LFL)
The concentration of a hydrocarbon gas in air below which there is insufficient hydrocarbon to support and propagate combustion. Sometimes referred to as "lower explosive limit (LEL)".
Liquefied Petroleum Gas. Mainly propane and butane, and can be shipped separately or as amixture.
Maximum allowable concentration. Expressed in ppm (parts per million). This is a concentration of a certain substance in the air, which is the maximum allowable exposure for working for a normal person without danger.
The time taken for the complete planetary movement through a 360o arc of the cleaning machine.
The steel deck forming the uppermost continuous watertight deck.
Valves in a tanker's piping system immediately adjacent to the ship/shore connecting flanges.
Maximum Allowable Relief Valve Setting of a cargo tank.
Air driven winches attached to shear legs that can be situated over tank cleaning holes or tank lids to lift out the buckets of sludge from tank bottoms.
An each place where a fore-and-aft pipeline passes through a tank bulkhead a valve is fitted in the line. This is known as a master valve and separates tanks served by the same fore=and-aft line.
A heterogeneous combination of elements and/or compounds in unfixed proportion.
The abbreviation for "millimetres of mercury" used as units of pressure.
The volume occupied by one molecular mass in grams (g mole) under specific conditions. For an ideal gas at standard temperature and pressure it is 0.0224 m3
The mass that is numerically equal to the molecular mass. It is most frequently expressed as the gram molecular mass (g mole) but may also be expressed in other mass units, i.e. kg mole. A! the same pressure and temperature the volume of one mole is the same for all perfect gases. It is practical to assume that petroleum gases are "perfect" gases.
The number of moles of any component in a mixture divided by the total number of moles in
Mooring winch brake design capacity
The percentage of the breaking strength (when new) of the mooring rope, or of the wire it carries, at which the winch brake is designed to yield. May be expressed as a percentage or in tonnes.
Mooring winch design heaving capacity
The power of a mooring winch to heave in or put a load on its mooring rope or wire. Usually expressed in tonnes.
The physical removal of loose debris or deposits after primary cleaning operations.
Those surfaces lined with secretion; for example, the inside of the nose, throat, windpipe, lungs and eyes.
Open flames or fires, lighted cigarettes, cigars, pipes or similar smoking materials, any other unconfined sources of ignition, electrical and other equipment liable to cause sparking while in use, and unprotected light bulbs.
A general name for mixtures of certain aromatic hydrocarbons.
A condition of profound insensibility, resembling sleep, in which the unconscious person cai only be roused with great difficulty but is not entirely indifferent to sensory stimuli.
Substances which produce narcosis.
Full strength application of a cleaner.
The chemical process in which a solution is brought to 7 pH by the addition of a counteracting solution.
Natural Gas Liquids. Liquid fractions found in association with natural gas. Ethane, propane, butane, pentane and pentanes plus
Organic liquids which remain fluid on exposure to air.
A metal or alloy which has no iron content.
Petroleum having a flashpoint of 60 °C (140 °F) or above as determined by the closed-cup method of test.
Normal temperature and pressure – a temperature of 0oC and a pressure of 760 mm Hg (sometimes called STP), standard temperature and pressure.
See "Combination carrier".
Oil Companies International Marine Forum.
Stenching compound added to liquefied petroleum gas to provide a distinctive smell. Eiry mercaptan is commonly used for this purpose.
The smallest concentration of gas or vapour, expressed in parts per million (ppm) by volume in air, that most people can detect by smell.
Cleaning surface with a chemical solution in which there is no recirculation or reuse of the solvents.
A system which does nothing to minimize or prevent the escape of vapour from tanks when the contents are being measured.
The introduction of a substance into the body via the mouth.
A chemical reaction that increases the oxygen content of a substance or compound.
A chemical compound produced by the reaction of oxygen with metal; example: Iron Oxide.
An element or compound that is capable of adding oxygen or removing hydrogen; or one that is capable of removing one or more electrons from an atom or group of atoms.
An instrument for determining the percentage of oxygen in a sample of the atmosphere drawn from a tank, pipe or compartment.
An atmosphere containing less than 21% oxygen by volume.
Petroleum or other cargo in drums, packages or other containers.
Filling and maintaining the cargo tank and associated piping system with an inert gas, other gas or vapour, or liquid, which separates the cargo from air.
The pressure exerted by a constituent in a gaseous vapour mixture as if the other constituents were not present. Generally this pressure cannot be measured directly but is obtained by analysis of the gas or vapour and calculation by use of Dalton's Law.
A process of treating a freshly cleaned metal surface to form a protective film or molecular layer which inhibits the rapid rerusting of the surfaces. For stainless steel tanks a layer of chromium oxide is formed by treating the surface with a dilute solution of nitric acid.
Percentage by volume
A method of determining a solution’s strength with respect to the most important constituent. Example: 5% (by volume) acid solution is 5 parts concentrated liquid acid with 95 parts water, giving 100 parts solution.
Percentage by weight
A method of determining a strenghth of a mixture with respect to the weight of the most important constituent. Example: 5% (by weight) SAF-ACID descaling compound solution is 5 parts by weight dry acid with 95 parts by weight water giving 100 parts solution.
A compound that is formed by the chemical combination of cargo liquid or vapour with atmospheric oxygen or oxygen from another source. These compounds may in some cases be highly reactive or unstable and constitute a potential hazard.
Hydrocarbon fuel as used for ignition-type internal combustion engines. In the U.S.A. this is called gasoline or gas.
Crude oil and liquid hydrocarbon products derived from it.
A gas evolved from petroleum. The main constituents of petroleum gases are hydrocarbons, but they may also contain other substances, such as hydrogen sulphide or lead alkyls, as minor constituents.
This can be used as an arbitrary indication of the acidity of a solution. Its practical range isOto 14. pH 7 represents absolute neutrality. A value of 1 represents high acidity (e.g. dilute hydrochloric acid) and 13 represents high alkalinity (e.g. a caustic soda solution).
A very toxic substance which, when absorbed into the human body by ingestion, skin absorption, or inhalation, produces a serious or fatal effect. Notwithstanding the above, corrosive liquids, such as acids (which, due solely to their corrosive nature, can be fatal if ingested), should not be classed as poisons.
A prefix, meaning "many".
The phenomenon whereby the molecules of a particular compound can be made to link together into a larger unit containing anything from two to thousands of molecules, the new unit
being called a polymer. A compound may thereby change from a free-flowing liquid to a viscous one or even to a solid. A great deal of heat may be evolved when this occurs. Polymerization may occur automatically with no outside influence, or it may occur if the compound is heated, or if a catalyst or impurity is added. Polymerization may, under some circumstances, be dangerous.
The lowest temperature at which a petroleum oil will remain fluid.
An insoluble substance which may be formed in a solution as the result of chemical reaction. The precipitate normally settles on the bottom.
Cleaning a system with chemical solution which is returned repeatedly to the area to be treated until the job is completed or the strenghth of the solution is depleted.
The preparation of a surface for a cleaning operation by the removal of loose debris or soils by flushing or mechanical means.
Pressure is defined as force per unit area. There are many units in common use; the prefered SI unit is newtons per square metre, though this is rarely used on ships.
Pressure measuring devices normally read pressures above or below atmospheric (i.e. atmospheric pressure is the chosen zero for that system of units). This pressure is called a gauge pressure.
The absolute pressure is the sum of gauge pressure and atmospheric. Absolute pressures are used in most thermodynamic tables, charts and calculations.
Pressure/vacuum valve (sometimes referred to as P/V valve, breather valve)
A dual-purpose valve commonly incorporated in the cargo tank venting system of tankers, the operation of which, when appropriately set, automatically prevents excessive pressure or vacuum in the tank or tanks concerned. On a tanker, such a valve may be either manually jacked open or by-passed when the vent system must handle large gas flows during loading or gas-freeing.
A sudden increase in the pressure of the liquid in a pipeline, brought about by an abrupt change in flow velocity.
Pressure/vacuum relief valve (P/V valve)
A device which provides for the flow of the small volumes of vapour, air or inert gas mixture caused by thermal variations in a cargo tanks.
Pyrophoric iron sulphide
Iron sulphide that is capable of a rapid exothermic oxidation, with incandescence, when exposed to air which is capable of igniting flammable hydrocarbon gas/air mixtures.
The inner structure designed to contain the cargo when the cargo containment system includes a secondary barrier which will contain the cargo for a time should the primary barrier fail.
The introduction of nitrogen or suitable inert gas or suitable cargo vapour to displace ar existing atmosphere from a containment system.
The introduction of inert gas into a tank that is already in the inert condition, with the object of:
(1) further reducing the existing content; or
(2) reducing the existing hydrocarbon gas content to a level below which combustion cannot be supported if air is subsequently introduced into the tank.
Pyrophoric iron sulphide
Iron sulphide of a rapid exothermic oxidation with incandescence when exposed to air which is capable of igniting flammable hydrocarbon gas/air mixture.
An element or compound that is capable of removing oxygen, or adding hydrogen, or one that is capable of giving electrons to an atom or group of atoms.
Reid vapour pressure (RVP)
The vapour pressure of a liquid determined in a standard manner in the Reid apparatus ata temperature of 100 °F (37.8 °C) and with a ratio of gas to liquid volume of 4:1.
Relative liquid density
The mass of a liquid at a given temperature compared with the mass of an equal volume of fresh water at the same temperature or at a different given temperature (see 8.3.2),
Relative vapour density
The mass of a vapour compared with the mass of an equal volume of air, both at standard conditions of temperature and pressure.
The air passages from nose to lungs inclusive.
Responsible officer (R.O. or RO) (or person)
A person appointed by the employer or the master of the ship and empowered to take all decisions relating to his specific task, having the necessary knowledge and experience for that purpose.
Responsible terminal representative, or Terminal representative
The shore supervisor in charge of all operators and operations at the terminal associated with the handling of products, or his responsible delegate.
Restricted gauging system (also known as "restricted ullage system")
A system employing a device which penetrates the tank and which, when in use, permits a small quantity of cargo vapour or liquid to be exposed to the atmosphere. When not in use, the device is completely closed. The design should ensure that no dangerous escape of tank contents (liquid or spray) can take place in opening the device.
Equipment to assist or restore the breathing of a man overcome by gas or lack of oxygen.
Ring main systems
A pipeline system that makes a complete circuit in a ring formation passing through the wing tanks of the vessle crossover lines through the center tanks to the other side if the main. On vessels with midship’s pumprooms one ring main serves the the fore tanks, and other the after tanks. On ships with an aft pumproom several layouts are common.
See “Responsible officer”
Rock and roll cleaning
The process of cleaning a shipboard tank ith a chemical solution with the only agitation being that of the ship'’ motion in transit.
The phenomenon where the stability of two stratified layers of liquid is disturbed by a change in their relative density resulting in a spontaneous rapid mixing of the layers, accompanied, in the case of liquefied gases, by an increased evolution of vapour.
The product of a chemical reaction involving iron, water and oxygen (air).
The preferential corrosion of an active metal for the sake of protecting a more noble (less reactive) metal. For example, a zinc anode immersed in an electrolyte (seawater) will, by galvanic action, preferentially corrode and thereby protect the adjacent steelwork of a ship's
Safety relief valve
Avalve fitted on a pressure vessel to relieve over-pressure.
Saturated vapour pressure
The pressure at which a vapour is in equilibrium with its liquid at a specified temperature.
The liquid-resisting outer element of a cargo containment system designed to afford temporary containment of a leakage of liquid cargo through the primary barrier and to prevent the lowering of the temperature of the ship's structure to an unsafe level.
Deposit or incrustation which may form on metal as a result of electrolytic or chemical action.
The tendency of a chemical to react with itself, usually resulting in polymerization or decomposition. Self-reaction may be promoted by contamination with small amounts of other materials.
Self-stowing mooring winch
A mooring winch fitted with a drum on which a wire or rope is made fast and automatically stowed.
The body responsible for the operation of a shore installation or shore equipment associated with the handling of chemical cargoes.
SI (Systeme international) units
An internationally accepted coherent system of units, modelled on the metric system, consisting of base units of length (metre), mass (kilogram), time (second), electric current (ampere), thermodynamic temperature (kelvin), luminous intensity (candela) and amount of substance (mole).
Society of International Gas Tanker and Terminal Operators Limited.
A device used to determine the liquid-vapour interface during the ullaging of semi-pressurized and fully pressurized tanks. See "Restricted gauging".
Spent cleaning solutions and soils.
A point to be noted in respect of tank filling levels is that, large prismatic cargo tanks, due to their width and shape, may suffer from substantial sloshing of cargo in heavy rolling conditions. Such tanks, and particularly membrane-type tankswhich have no centre line wash bulkheads, may have prohibited filling levels in order to avoid damage to tank structures or internal fittings. Typical controls on such tanks are a prohibition on all filling levels in the 10 to 80 per cent range.
If an unusual cargo distribution is required and if this involves cargo tanks only being part-filled, then it is usual for the shipmaster to seek further guidance from shipowners. In such cases it is sometimes necessary for the owner to seek confirmation from the ship’s classification society before loading can start.
A mixture of amorphous and/or loose ‘scale-like’ particles which is carried by fluid flow and accumulates at one or more points in a system due to lack of sufficient flow velocity.
International Convention for the Safely of Life at Sea, 1974.
The solubility of a substance in water, at a specified temperature, is the maximum weight of substance which will dissolve in a given weight of water, in the presence of undissolved substance. The value is usually expressed as the number of grams of substance dissolving in 100 grams of water. In the case of liquid dissolving in liquid, the term "miscibility" is often used instead of "solubility". Ethanol dissolves in water at ordinary temperatures in all proportions, and is said to be completely miscible. A hydrocarbon and water, on the other hand, are immiscible. Aniline and water are partially miscible.
These oils are known as emulsifying oils, since they are normally bright, clear oils which, when mixed with water, produce milky emulsions. In some soluble oils the emulsion is so fine that instead of milky solutions in water, amber colored transparent solutions are formed. Typical examples are sodium and potassium petroleum sulfonates.
A fluid chemical which dissolves or solubilizes another material.
Sour crude oil
A crude oil containing appreciable amounts of hydrogen sulphide or mercaptans.
A vapour sample of known composition and concentration that is used to calibrate gas-detection equipment.
Specific gravity (Sp. Gr.)
The ratio of the weight of a substance at a temperature t1, to the weight of an equal volume of fresh water at a temperature t2, where t1 does not necessarily equal t2. Temperature will affect volume; therefore the temperature at which the comparison was made is stated on each data sheet, after the ratio.
e.g., S.G.== 0.982 at 20 °C/15 °C.
"20 °C" referring to the temperature of the substance and "15 °C" referring to the temperature of the water.
The ratio of the thermal capacity of a substance to that of water. For a gas, the specific heatal constant pressure is greater than that at constant volume.
Ignition of a combustible material is termed "spontaneous" if the inherent characteristics of the material cause a heat-producing (exothermic) chemical action, and thus ignition, without exposure to external fire, spark or abnormal heat.
The secondary cleaning of specific soiled areas with the neat application of a solvent followed by water flushing and/or wiping to produce a deposit-free surface.
A system of pipelines, usually 3 or 4 in number, that run from the after pump room straight up through the center tanks and supply block tanks only/
Temporary scaffolding erected in a tank to facilitate a cleaning job for a work crew.
An alloy of iron with 12-20% chromium, and sometimes nickel, which reacts with oxygen in the air to form a cromium oxide, rendering the steel resistant to corrosion by many substances. Such stainless steel is called passivated.
Static accumulator oil
An oil with an electrical conductivity less than 100 picosiemens/metre (pS/m), so that it is capable of retaining a significant electrostatic charge.
The electricity produced on dissimilar materials through physical contact and separation.
Static non-accumulator oil
An oil with an electrical conductivity greater than 100 picosiemens/metre (pS/m), which renders ii incapable of retaining a significant electrostatic charge.
Stern discharge line
Acargo pipeline over the deck to a point terminating at or near the stern of the tanker.
The final operation in pumping bulk liquid from a tank or pipeline.
All cargo main systems have stripping lines, separate from the cargo lines, incorporated into the systems. These are small diameter pipelines, connected to low-capacity pumps, which are used for draining or stripping out the last few centimeters of oil in the tanks. The oil stripped out is pumped to an aft cargo tank, known as the slop tanks, and from there it is pumped ashore by a main cargo pump. The stripping lines and pumps are also used in tank washing operations.
The conversion of a solid direct into a vapour without melting, e.g. naphthalene. The significance of sublimation is that there may be sufficient vapour above the solid for combustion. In such a case the flashpoint may be lower than the freezing point.
A type of centrifugal cargo pump commonly installed on gas carriers and in terminals in the bottom of a cargo tank, i.e. with drive motor, impeller and bearings totally submerged when the tank contains bulk liquid.
This takes place if a liquid drops in temperature below its freezing point without freezing.
A phenomenon generated in a pipeline system when there is any change in the rate of flow of liquid in the line. Surge pressures can be dangerously high if the change of flow rate is too rapid, and the resultant shock waves can damage pumping equipment and cause rupture of pipelines and associated equipment.
Systemic toxic effect
The effect of a substance or its vapour on those parts of the human body with which it is not in contact. This presupposes that absorption has taken place. It is possible for chemicals to be absorbed through skin, lungs or stomach, producing later manifestations which are not a result
of the original direct contact.
Close to each bellmouth is located a valve which controls the flow of oil into and out of the tank. These valves are operated either manually from the deck above or automatically the cargo control room. Manual valves are operated by turning a wheel on a deck stand. Automatic valves are activated by an hydraulic oil pipeline system similar to that which operates the steering gears.
Tank vent system
The piping system and associated valves, installed to prevent over-pressure and excessive vacuum in cargo tanks.
A ship designed to carry liquid petroleum cargo in bulk, including a combination carrier when
being used for this purpose.
Tension winch (automated or self-tensioning mooring system)
A mooring winch fitted with a device which may be set to automatically maintain the tension on a mooring line.
A place where tankers are berthed or moored for the purpose of loading or discharging petroleum cargo.
The person designated by the terminal to take responsibility for an operation or duty.
Threshold limit value (TLV)
Concentration of gases in air to which it is believed personnel may be exposed 8 hours per day or 40 hours per week throughout their working life without adverse effects. The basic TLV is a Time-Weighted Average (TWA) and may be supplemented by a TLV-STEL (Short-Term Exposure Limit) or TLV-C (Ceiling exposure limit, which should not be exceeded even instantaneously).
The operation of completing the loading of a tank to a required ullage.
The introduction of inert gas into a tank which is already in the inert condition, with the object of raising the tank pressure to prevent any ingress of air.
Poisonous to human life.
A liquid which, if ingested or absorbed through the skin, causes bodily harm that maybe severe.
A vapour which, if inhaled, causes bodily harm that may be severe.
True vapour pressure (TVP)
The true vapour pressure of a liquid is the absolute pressure exerted by the gas produced by evaporation from a liquid when gas and liquid are in equilibrium at the prevailing temperature and the gas/liquid ratio is effectively zero.
The depth of the space above the liquid in a tank.
Upper flammable limit (UFL)
The concentration of a hydrocarbon gas in air above which there is insufficient air to support and propagate combustion. Sometimes referred to as "upper explosive limit (UEL)".
A gas below its critical temperature.
The relative weight of the vapour compared with the weight of an equal volume of air at standard conditions of temperature and pressure. Thus vapour density of 2. 9 means that the vapour is 2, 9 times heavier than an equal volume of air, under the same physical conditions.
The pressure exerted by the vapour above the liquid, at a given temperature it is expressed as
Vapour seal system
Special fitted equipment which enables the measuring and sampling of cargoes contained in inerted tanks without reducing the inert gas pressure.
The provision of adequate air flow into or out of confined space containing equipment being cleaned.
The process of air/vapour release to and from cargo tanks.
The property of a liquid which determines its resistance to flow.
An enclosed space in the cargo area that is external to a cargo containment system and which is not a hold space, ballast space, fuel or oil tank, cargo pump or compressor room or any space in normal use by personnel.
A liquid which evaporates readily at ambient temperatures.
Volatile organic compounds (VOC)
Any volatile compound of carbon which participates in atmospheric photochemical reactions. For regulatory purpose this may exclude carbon dioxide, carbon monoxide, carbonic acid, metallic carbides or carbonates, and ammonia carbonate, depending on regulatory body.
Petroleum having a flashpoint below 60 °C (140 °F), as determined by the closed-cup method
The tendency for a liquid to vaporize.
Vessel Specific Manual
A suspension in the atmosphere of very fine droplets of water, usually delivered at a high
pressure through a fog nozzle for use in fire fighting.
A suspension in the atmosphere of water divided into coarse drops by delivery through a
special nozzle for use in fire fighting.
Any petroleum product containing a significant quantity of paraffin as one of its constituents.
A document issued by a responsible person permitting specific work to be done during a
specified period in a defined area.
1.5. RULES AND REGULATIONS
1.5.1 The most important of the rules governing tankers as:
-international rules and regulations:
.1 The International Convention on Standards of Trainin, Certification and Watch keeping for Seafarers (STCW-95)
.2 The International Convention for the Safety of Life at Sea, 1974 (SOLAS 1974)
.3 The International Convention for the Prevention of Pollution from ships, 1973/1978 (MARPOL 73/78)
.4 The International Load Line Convention (ILLC)
.5 Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (BCH Code)
.6 The International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (BCH Code)
.7 Cjde for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (GC Code)
.8 The International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code)
.9 Guidelines for the Development of Shipboard Oil Pollution Emergency Plans (SOPEP)
.10 The International Safety Management Code (ISM Code)
2- national rules and regulations:
Documents 2,3,4,5,6,7,8 and 9 are IMO documents and have been incorporated as such in the national legislation of IMO member states through the world.
3- classification society rules:
Many classification Societies have in fact incorporated the text of the Chemical Tankers Codes and Gas Carriers Codes in their rules and have added specific extra requirements.
1.5.2 Transport of oil, liquid chemicals and liquefied gas by sea bulk is internationally regulated – as regards safety and pollution aspects – through conventions adopted by the International Maritime Organization (IMO).
1.5.3 The convention requirements are supplemented by recommendations, specifications and codes adopted by IMO.
1.5.4 The IMO conventions covering the carriage of oil, chemicals and liquefied gas in bulk are:
1- the International Convention for the Safety of Life at Sea (SOLAS), 1974, as amended
2- the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the 1978 Protocol (MARPOL 73/78), as amended
3- the International Convention for Standards of Training, Certification and Watchkeeping, as amended
1.5.5 All tankers of 500 gross tons and upwards must comply with the International Management Code for safe Operation of Ships and for Pollution Prevention (ISM Code).
1.5.6 The most important codes and standards covering the transport of chemicals are:
1- the Bulk Chemical Codes (BCH and IBC Code)
2- Standards for Procedures and Arrangements (P&A Standards)
1.5.7 The codes and standards covering design, construction and other safety measures for ships carrying liquefied gases in bulk are set out in the IMO’s Gas Carrier Code (IGC Code).
1.5.8 Examples of national rules (In Russia):
Mорской Регистр СудоходстваЖ
- Правила классификации и постройки мщрских судов, Том 1 (464с)
- Правила классификации и постройки мщрских судов, Том 2 (442с)
- Правила по оборудованию морских судов
- Правила по грузоподъемным устройствам морских судов
- Правила о грузовой марке морских судовю
1.5.9 Lists examples of classification society rules.
International control is now described as reasonably tight, as a result of the IMO conventions MARPOL, SOLAS and for training, STCW Convention.
1. CHARACTERISTICS OF CARGOES
1.1. BASIC PHYSICS
2.1.1 Defines the following in simple terms:
1- States of Aggregation
A substance (matter) can present itself to us in three different forms or phenomena. These are called states of aggregation. The three forms are:
a. The solid or crystalline state
There is a strong attraction between the molecules of the substance. Therefore, these molecules are closely together in more or less fixed positions, e.g. in a crystal. A solid substance has its own form and volume.
b. The liquid state
The powers of attraction between the molecules are much smaller, so that the mutual distances are bigger, and the molecules can move with respect to one another. Although there is still a connection, the liquids do not have a form of their own and they are movable; they do have their own volume.
c. The gaseous state
There are hardly any powers of attraction between the molecules which move completely free in respect of one another. They have no form of their own, no volume of their own; a gas completely fills the container in which it is present; therefore so to speak, takes on the form and volume of this container.
The stage of aggregation of a substance depends on pressure and temperature. At high pressures and low temperatures we usually have to do with solid substances; low pressures and high temperatures stimulate the existence of gases. In a pressure-temperature diagram, a so-called phase-diagram, the mutual relations of solid substances, liquid and gas can be represented and the areas defined.
LIQUID = LIQUID AT 20°C VAPOUR
LIQUID NOT LIQUID AT 20°C GAS
2- Melting and sublimation
When heat is supplied to a solid substance, this substance will pass at a certain temperature into the liquid state. This temperature, which remains constant for pure substances as long as solid parts are present, is called the melting point.
The reverse process (the withdrawal of heat from a liquid, whereby the liquid passes into the solid phase) is called solidifying. For pure substances the solidification point or freezing point coincides with the melting point. Mixtures of substances have a melting range=solidification range. Liquids with dissolved, solid impurities have a lower freezing point than the pure liquid (freezing point lowering).
Some substances do not have a melting point at atmospherical pressure, but immediately pass from the solid to the gaseous state. This process is called sublimation.
The temperature at which the vapour pressure of a liquid is equal to atmospheric pressure. Boiling points, as quoted on the data sheets, are correct at a pressure of 760 mm Hg, unless indicated to the contrary.
Examples of boiling point:
-boiling point = 100°C (water) VAPOUR
-boiling point = 56.2°C (acetone) VAPOUR
-boiling point = -0.5°C (butane) GAS
-boiling point = -195.5°C (nitrogen) GAS
3- Liquid density
The density of a liquid is defined as its mass per unit volume and is commonly measured in kilogrammes per cubic decimeter (kg/dm3 ).
Alternatively, liquid density may be quoted in kg/litre or in kg/m3
4- Vapour density
The density of vapour is commonly quoted in units of kilogrammes per cubic metre (kg/m3 ). The density of the saturated vapour increases with increasing temperature. This is because the vapour is in contact with its liquid and as the temperature rises more liquid transfers into the vapour-phase in order to achieve the higher vapour pressure. It results in a considerable increase in mass per unit volume of the vapour space.
1- Vapour pressure
All petroleum products and crude oil are essentially mixtures of a wide range of hydrocarbon compounds. The boiling points of the compounds range from –162oC (methane) to well in excess of +400oC, and the volatility of any particular mixture of compounds depends primarily on the quantities of the more volatile elements. The volatility is characterised by the vapour pressure. When transferring a petroleum product to a gas-free tank it begins to vaporise, that is, it liberates gas into the space above it. This gas has also a tendency to re-dissolve in the liquid. The pressure exerted by this gas is called the equilibrium pressure of the liquid, usually reffered to simply as the vapour pressure.
2- Partial pressure
The individual pressure exerted by a gaseous constituents in a vapour mixture as if the other constituents were not present. The pressure cannot be measured directly but is obtained firstly by analysis of the vapour and then by calculation using Dalton’s Law.
Supposing that 100 m3 of air only consists of 21% (vol.) OXYGEN and 79% (vol.) Nitrogen:
Air 100 m3
21 vol % oxygen
79 vol % nitrogen
Total pressure = 1000 mBAR
partial pressure = 210 mBAR
79 m 3 nitrogen
partial pressure = 790 mBAR
Total volume tank = 100 m3
Volume Liquid = 12.5 m3 (12.5 %)
Volume vapour = 87.5 m3 (87.5%)
Temp. = 20° C, total pressure = 1000 mBAR
pMax toluene at 20° C = 29 mBAR
Partial pressure Toluene vapour = 29 mBAR
Volume % Toluene vapour = 29 x 100/1000 = 2.9 Vol %
The property of a fluid which restricts one layer of the fluid moving over an adjacent layer called viscosity. The unit of viscosity is mPa.s. Water has viscosity 1 mPa.s at 20° C.
8- Pour point
The lowest temperature at which a petroleum oil will remain fluid.
The disorderly motion of the molecules in a liquid is responsible for the phenomenon of diffusion. Due to this disorderly, natural movement, molecules can stiff all through the liquid.
2.1.2 The structure of atoms and molecules.
Atoms are the smallest parts of matter capable of entering into chemical combination.
Atoms can’t be splitterd into smaller components with chemical means.
The smallest particle of substances which still posses all the properties of those substances.
Pure matter consisting of atoms of one kind.
Matter can’t be splitterd into smaller components with chemical means.
Protons = positive electric charge
Neutron = no electric charge
Electron = negative electric charge
No electric charge
Number of protons = number of electrons.
2.1.3 A negatively charged body has an access of electrons
2.1.4 A positively charged body has a shortage of electrons
2.1.5 Similarly charged bodies repel each other and oppositely charged bodies attract each other
2.1.6 Induction and how the induction of an electrode may cause it to become charged
If an uncharged conductor is present in an electrostatic field it has approximately the same voltage as the region it occupies. Furthermore the field causes a movement of charge within the conductor; a charge of one sign is attracted by the field to one end of the conductor and an equal charge of opposite sign is left at the opposite end. Charges separated in this way are known as inducted charges and as long as they are kept separate by the presence of the field they are capable of contributing to an electrostatic charge.
2.1.7 How a charged electrodes may be discharged?
When the two materials, after having been statically charged, are separated, an electric field develops between the positive material and the negative material. The “accumulated” electricity will try to discharge itself in order to neutralize the electric field. An electric field can also develop when an electrically charged material approaches a non-charged material (so called “third electrode”).
2.1.8 A discharge releases enrgy which may a spark.
The neutralize the electrical field (so called “discharge”) often takes place in the form of sparks which, generally, have sufficient energy to ignite explosive vapour/air mixtures.
The principle of electrostatic charging also applies to liquids in motion, (and sometimes also to gases). When a liquid flows through a pipe line, this liquid can be charged (generally, positively) in respect of the pipe line. The effect depends on the electrical conductivity of the liquid; moreover, the effect depends on the nature of the liquid, the diameter and the material of the pipe line, the flow velocity, etc.
2.2. BASIC CHEMISTRY, CHEMICAL ELEMENTS AND GROUPS
2.2.1 explain in simple terms:
In general view:
and their and its
1-chemical symbols and structure
Examples of symbols in chemistry:
(all the symbols are shown in the Periodic table)
COMMON NAME LATIN NAME SYMBOL
Magnesium Magnesium Mg
Oxygen Oxygenium O
Carbon Carbonium C
Hydrogen Hydrogenium H
Nitrogen Nitrogenium N
Sodium Natrium Na
Potassium Kalium K
Phosphor Phosphorum P
Sulpher Sulpherum S
2- “atomic number” and “atomic weight”:
When we say that an atom has a certain mass, it is clear that this mass must have a certain weight. Formerly, people worked with the ratios in weight of one atom in respect of one atom hydrogen (hydrogen being the lightest known atom) but, nowadays, in accordance with the latest agreement, the atomic weights of other atoms are expressed by giving their ratio to that of carbon 12C. One could say: the atomic weight of an element is the number which indicates how many times heavier one atom of that element is as 1/12th of the weight of one atom carbon.
The atomic number is the number of protons in an atom. This value is:
1 for hydrogen
2 for helium
3 for litium
92 for uranium etc.
The number of electrons must equal the number of protons. Mass number of the element gives the average number of protons and neutrons in an atom. Ex.: Potassium:
Atomic number =19
3-the Periodic System and Periodic Table
4- a hydrocarbon molecule:
A molecule of hydrocarbons consist of atoms both carbon (C and hydrocarbon (CH). There are coal, diamonds and graphite in the nature.
We can say that an atom of carbon has “four hands” in readiness to “shake hands”, i.e. so called valent bonds. The valence of an atom is the number of electrons with which an atom will go into chemical combination. Thus:
Carbon + Hydrogen = hydrocarbon
Instead of “hand” a valence sign ¾ is used. An atom of carbon has four valent bonds, and an atom of hydrogen has only one:
¾ C ¾ ¾ H H ¾ C ¾ H
Being one atom of carbon and four atoms of hydrogen “shaked hands” we have a molecule of Methane. This is the lightest molecule of hydrocarbon.
As more carbon atoms (with an appropriate number of linked hydrogen atoms) are used to form the petroleum molecule, so the molecule will become heavier and have a higher boiling temperature at atmospheric pressure.
A simple diagram (below) shows the approximate numbers of carbon atoms forming the petroleum molecules:
Gaseous 20---------------------- ® Solid
1 -------------- 4
---------------------------------------------------------------- ® carbons atoms per molecule
5 ----- Liquid ---- 19
The lightest molecules, METHANE, are stripped off at the well head together with any earthy solids; the remaining petroleum is termed CRUDE OIL. One drop of crude oil consist of about one thousand of hydrocarbons. The process of refining the crude oil will produce a number of FRACTIONS. Each fraction will consist of a range of petroleum molecules, which at atmospheric pressure and temperature will be gaseous, liquid or solid.
Names of hydrocarbons are originated accordance with Greek numerals 1,2,3,4,5,6,7,8,9,10 and so on (metha, etha, propa, buta, penta, hexa, hepta, octa, nona, deca and so on) adding –NE:
CH4-METHANE, C2H6-ETHANE, C3H8-PROPANE, C4H10-BUTANE, C5H12PENTANE and so on.
5-chemical elements of acids and basses:
ACID-chemical compound containing hydrogen-ion(s) which can be replaced by metal-ion(s)
HCL + FE ® FE CL2 + H2
HydroCLoric acid = HCL
Sulphuric acid = H2SO4
Nitric acid = HNO3
Phosphoric acid = H3PO4 “H” IN FRONT OF THE FORMULA
ALKALY-chemical compound which neutralize acids
NaOH + HCL ® NaCL + H2O
Sodium hydroxyde = NaOH
Potassium hydroxyde = KOH
Ammonium hydroxyde = NH4OH “OH” AT THE AND OF THE FORMULA
In chemical reactions matter is neither lost or added:
Magnesium + Oxygen forms Magnesium oxide
Mg + O ® MgO
Carbon + 4H ® CH4
2.2.2 examples of chemical reactions
A reaction equation is an indicator how a chemical reaction proceeds. For example, the reaction between iron and sulfur, and the reaction equation is:
Fe + S ® FeS
On the ltft of the ® the atoms which have to react with one another are symbolized, and on the right ® the compound or compounds which has (have) developed from this reaction.
Hydrogen + oxygen results in water. The reaction equation is:
2H + O ® H2O
As oxygen is bivalent and hydrogen is only monovalent, two atoms hydrogen have to react with one atom oxygen to get a molecule water.
2.2.3 The use of the Codes in relation to reactivity of cargoes.
The IBC Code gives no help on the compatibility of cargoes problem, it simply mentioned that cargoes or slops, that dangerously mag react with each other, should be separated by an intervening compartment that not contain a reactive substance.
US Coast Guard has regulated this problem in the Code of Federal Register,46 CFR 150.
The cargoes are divided into chemical groups of families and group number 1-22 represents REACTIVE CHEMICALS, while 30-43 are PRODUCTS that do not react mutually with each other. The missing numbers are reserved for future EXTENSIONS of the Compatibility Chart.
2.2.4 The meaning of the chemical data for a common cargo (as given in the ICS or other Cargo Data Sheets).
ICS (the International Chamber of Shipping) have designed the Cargo Data Sheet (CDS) for any chemical cargo. The Proform of CDS contains the CHEMICAL DATA section: formula, chemical famely, additional information,reactivity with: oxidising agents, acids, alkalis, salt or fresh water, air, other chemicals.
The hydrocarbon structure:
2.2.5 in general:
1-crude petroleum as discharged at the well head is a mixture of about one thousand of different
2-the molecules are termed “light” or “heavy” according to the number of carbon atoms forming
3-very light molecules such as methane, butane and propane tend to be gasseous under normal
4-very heavy molecules such as asphalt and bitumen tend to be solid under normal atmospheric
5-intermediate molecules such as petrol (motor spirit) and diesel oil tend to be liquid under normal
6-very light gaseous molecules such as methane are extracted at the well head
-the petroleum remaining after the removal of products such as methane is termed “crude oil”
7-the petroleum remaining after the removal of products such as methane is termed “crude oil”
8-crude oil is a mixture of hydrocarbons which under normal atmospheric conditions are gaseous,
liquid and solid
9-in an oil refining process termed “distillation”, crude oil is split into a number fractions
10-each petroleum fraction has a range of physical properties specified to itself.
Examples of the products in common use:
methane (industrial gas) ü gaseous at
propane gas (industrial and domestic) ý atmaspheric pressure
butane gas (mainly domestic) þ and temperature
motor spirit (petrol)
gas oil liquid at atmospheric pressure
diesel oil and temperature
heavy fuel oil
greases semi-solid or solid
wax solid at atmospheric
bitumen pressure and temperature.
2.3 PHYSICAL PROPERTIES OF OIL, CHEMICALS AND GASES CARRIED
2.3.1 Define the following in simple terms and explain their practical significance in the tanker trade:
1- Flashpoint the lowest temperature at which a liquid gives off sufficient vapour to form a flammable mixture with air near the surface of the liquid. The flash point temperature is determined by laboratory testing in a prescribed apparatus. There are two methods: either by closed method –in the closed cup (c.c.) or by open method- in the open cup (o.c.)
2- Volatility. The vo;atility (i.e. the tendency of a crude oil or petroleum product to produce mixture of compounds depends primarily on the quantities of the more volatile constituents (i.e. those which a lower boiling point). The volatility is characterized by the vapour pressure. Volatile petroleum has a flashpoint below 60oC (140oF), as determined by he closed-cup method of testing.
3-Saturated vapour pressure-the pressure exerted by the vapour above the liquid, at a given temperature. It is expressed as absolute pressure. Molecules “escaping” from liquid collide with material and produce energy:
collision ® energy = pressure
The volatility is characterised by the vapour pressure, too. The true vapour pressure (TVP) or bubble point vapour pressure is the equilibrium of vapour pressure of a mixture when the gas/liquid ratio is effectively zero.
When transferring a petroleum product to a gas-free tank it begins to vaporise, that is, it liberates gas into the space above it. This gas has also a tendency to re-dissolve in the liquid. The pressure exerted by this gas is called the equilibrium pressure of the liquid, usually referred to as the saturated vapour pressure.
pressure ® vapour pressure ® saturation of vapour
Maximum vapour pressure is called “saturated vapour pressure”.
maximum vapour pressure = atmospheric pressure
Reid vapour pressure (RVP). The vapour pressure of a liquid determined in a standard manner in the Reid apparatus at a temperature of 100oF (37.8oC) and with a ratio of gas to liquid volume of 4:1. It used for comparison purpose only.
4-Vapour pressure/temperature relationship. The vapour pressure of a pure compound depends only upon its temperature. The vapour pressure of a mixture depends both upon its temperature and the volume of the gas space into which vaporization occurs. The highest vapour pressure is possible at any specified temperature. As the temperature of a petroleum mixture increases, its TVP also increases.
5-Influence of pressure on melting and boiling point. Melting point is the temperature at which the states of aggregation is changed from solidifying to melting .
If the TVP exceeds atmospheric pressure, the liquid begins to boil. Boiling point is the temperature at which the vapour pressure on its surface is equal to the
The temperature at which the vapour pressure on its surface
At it’s boiling point a liquid will change-over completely into vapour/gas and temperature remains the same.
Liquid = liquid at 20oC ® vapour
Liquid not liquid at 20oC ® gas
Water: Boiling point = 100oC ®(water) vapour
Acetone: Boiling point = 56.2oC ® (acetone) vapour
Butane: Boiling point = -0.5oC ® (butane) gas
Nitrogen: Boiling point = -195.5oC ® (nitrogen) gas
The temperature at which the states of aggregation is changed from SOLIDIFYING to MELTING.
In the CDS both boiling point and melting point is related with atmospheric pressure = 1013 mbar.
It is also possible to make liquids boil at a lower pressure (e/g/ ley a partial vacuum suction). Consequently, the boiling point belonging to it is lower than the normal boiling point. The same applies to hifher pressure. Therefore, the maximum vapour pressure line is rightly called the ‘boiling line’.
Generally, mixtures of liquids do not have a boiling point, but a boiling range.
The external pressure/melting point relationship is defined with a ‘melting line’. Almost there is no influence of pressure on the melting point. On the P-T diagram, there is a line between Solid (S) and Liquid (L) states of agregation. It is named as ‘melting line’. At the atmospherical pressure (1013 mbar) there is intersection point with the melting line. This point indicates the melting point, which is used for the cargo certificate.
When a petroleum is ignited it is the gas progressively given off by the lliquid which burns as a visible flame. The quantity of gas available to be given off by a petroleum liquid depends on its volatility which is frequently expressed for purposes of comparison in terms of Reid Vapour Pressure RVP). A more informative measure of volatility is the True Vapour Pressure (TVP) but unfortunately this is not easily measured. It is referred to in this guide only in connection with venting problems with very volatile cargoes, such as some crude oils and natural gasolines.
7-Lower flammable/explosive limit (LFL/LEL)
When an inflammable gas (vapour) is mixed with air, an explosive mixture may develop. At very low vapour concentration no explosion takes place. When the vapour concentration is increased, there will be an explosion at a certain critical vapour/air ratio. This is the Lower Explosive Limit (LEL): the lowest concentration at which a gas (vapour) can still just be brought to explosion.
Petroleum gases can be ignited and will burn only when mixed with air in certain proportions. If there is too little petro;eum gas the mixture cannot burn. The concentration of a hydrocarbon gas in air below which there is insufficient hydrocarbon to support and propagate combustion is named as Lower Flammable Limit (LFL)
8-Upper flammable/explosive limit(UFL/UEL)
At very high vapour concentrations (too ‘rich’ mixture) the quantity of oxygen will be too small to maintain the combustion. Consequently, there is also an Upper Explosive Limit (UEL): the highest concentration of which a gas/vapour can still just be brought to explosion.
If there is too little oxygen the mixture petroleum gases/air cannot burn, too. The concentration of a hydrocarbon gas in air above which there is insufficient air to support and propagate combustion is named as Upper Flammable Limit (UFL).
The limiting proportion are expressed as percentage by volume of petroleum gas in air.
There is no real difference between gas and vapour. The liquids falling under the ‘Chemical Codes’ are only those which at 37.8oC (100oF) have a maximum vapour pressure of 2.8 bar.
Both LEL and UEL are usually expressed in volume per cents in air at 20oCCCCCC and 1013 mbar (sometimes in g/m3 or in g/kg of air).
The lowest temperature to which a solid liquid or gas requires to be raised to cause self-sustained combustion witout initiation by a spark, flame or other source of ignition. The auto-ignition temperature of vapours of fuel and lubricating oils are muchlower than those of the vapours from more volatile petroleum liquids. Fuel and lubricating oils are thus more liable to ignite if they are allowed to fall or sprayed on hot surfaces despite the absence of external flame or spark. Care must also be taken to avoid rags soaked in fuel or lubricating oil coming into contact with hot surfaces.
Some fibrous materials when moist with water, or soaked by oils or chemicals, are liable to ignite without the application of heat, due to the gradual build-up of heat by oxidation. For this reason, cotton waste, canvas, bedding or similar absorbent materials in bulk,bales or bundles should not be stowed in close proximity to oil,paint, etc. If such materials should become damp or contaminated, they should be neither dried and cleaned or destroyed.
The accindental mixing of one chemical product with another inside a cargo tank or pipe may result in a vigorous chemical reaction. Binary combinations that generate significant heat or produce gas can be very hazardous to personnel and property.In rare cases the reacton of two components (even though non-hazardous) may produce a product which is significantly more flammable or toxic than the original materials.
Even the water washing of cargo tanks and slop tanks containing residues of certain substances may produce dangerous reactions. Dangerous reactions are polymerisation, autoxidation, mutual reactions between chemicals, etc. In detail see Section 3.5 ‘Reactivity hazards’.
It means a ‘poison’ in the Greak language (toxikon).
Toxicity is the ability of a substance to cause damage to living tissue, impairment of the central nervous system, illness or in extreme cases death when inhaled, ingested or absorbed through the skin.
In detail see Chapter 3 ‘Toxicity and other hazards’.
Corrosion hazards are dangerous to Personnel and to metal. Some liquid cargoes are so corrosive that in contact with the skin will completely or partly destroy living tissue. Less corrosive liquids may only be irritating to the skin but can result in serious damage to the eyes.
Corrosion is the etching or attack of metals on the surface.Corrosion can have different causes and it can present itself in many manifestations.
Consequently, both Personnel and metals have to be protected against activity of corrosion. In detail see Section 3.6 ‘Corrosion hazards’.
2.3.2 there is need for taking cargo samples and for the chemical and physical analysis of cargoes
Immediately after the starting loading, a sample of the cargo must be taken before it enters the ship’s line system. This is usually done by means of draincock just before and or just after the manifold valve. This sample should be checked for any signs of contamination in the shore line.
Although both the cargo systems and the cargo tank have been cleaned and prepared for the cargo, and also nothing that the tank has been inspected and approved by shipper’s representative or surveyor, it is very often the practice to take a sample after a small quantity of the cargo has been loaded into the tank. This sample should be checked for any signs of contamination in the ship’s cargo line.
After completion loading and before beginning of unloading cargo samples have to be taken again. If serious static charges are expected in a loaded cargo you have to wait 30 minutes before sampling. These samples have to be compared against from the shore tank(s) samples to check for any signs of the quality cargo changes.
2.3.3 the properties of oil, chemical and gases carried in bulk, including:
1-the determination of cargo temperature
There are a few models of electronic tape to determine of ullage and cargo temperature simultaneously. Some of them have an integrated microchip to determine of cargo temperature up to nine levels and to calculate of an average the cargo temperature in the tank.
Meanwhile an ordinary ullage tape still is used to determine of cargo temperature by means of thermometer on the end of the tape.
There is a standard procedure to do so. The cargo temperature have to be determined on the level equal 5/12 of sounding. The thermometer have to stay there 10 minutes about.
The determination of cargo temperature have to be completed in the interval from 15 to 20 minutes before commence of sounding/ullaging.
If serious static charges are expected in a loaded cargo never use a nilon and other synthetic tape.
2-the determination of cargo density
Density = mass/volume.
But in the tanker trade the density is determined as:
Density = vacuum factor x litre weight
The litre weight is calculated from the difference in weight between the empty and the full pycnometer in laboratories.
From this litre weight the Specific Gravity can be calculated:
Vacuum factor x litre weight at a certain temperature has to be divided by the density of water at a certain temperature, too.
Specific gravity 15/15oC = vacuum factor x litre weight/0.99913
Specific gravity 15.5/15.5oC = vacuum factor x litre weight/0.99905
Specific gravity 15.6/15/6oC = vacuum factor x litre weight/0.99903
Specific gravity 20/4oC = vacuum factor x litre weight/1
(density of water @ 4oC is max. And equal 1.00000)
All these ‘specific gravity’ are named as ‘Relative Density’ but Specific Gravity 60oF/60oF (Sp.Gr.) is traditional unit in the United Kingdom and in many other related countries).
The density of a product can also be determined with a hydrometer (areometer). The sample in introduced into a glass cylinder and brought to the desired temperature. Then the areometer is imersed in the liquid and the density is read from the areometer on the surface of the liquid.
Practically the density of cargo is determined with an areometer at the actual temperature. There is ASTM – ip Table 53 to convert the obtained density into D15 (kg/l). There are another tables numbers where we need D15 to entry into them. For example, the Table 54 of ASTM – IP give us volume correction factor (V.C.F.) by means D15 and average temperature of cargo. The Table 56 ASTM – IP is used to convert mass to weight-in-air by means of conversion factor.
Beside that there is API gravity at 60oF. The Table 3 ASTM-IP is used to convert API gravity to the D15 and Sp. Gr.
The specific gravity and density of a product are also measures for its purity. Litre weight and density are used for quantity determinations.
The specific gravity is the ratio of the mass (in vacuum) of a given volume of a substance at a certain temoerature to the mass (in vacuum) of an equal volume of water at the same or another temperature.
The density is the mass (in vacuum, in gams) in respect of a volume of that substance (in ml) at a given temperature.
The litre weight is the weight in normal air of 1 litre of the product at a given temperature.
3-determination of colour of cargoes and use of color scale
The colour of a product is used as a measure for the quality of that product. The following systems are used:
- Acid wash colour
- ASTM or NPA colour
- F.A.C. colour
- Lovibond colour
- Saybolt colour
- APHA colour.
Acid wash colour method is used for analyzing aromatic hydrocarbons, like toluene and xylene. The acid will remove impurities present in the sample and will discolour. ASTM or NPA methods are used to analyse lubricating oils, diesel fuels, etc. The F.A.C/ colour will be mainly analyzed in animals fats. The molten fat is compared with standard colours numbered 1,3,5,7 etc. Lovibond colour method, generally, is used for analyzing animal and vegetable oils and fats. The colour is determined with a Lovibond Tintometer. Saybolt colour determination is used to measure the colour of refined petroleum products, like aviation gasoline, jet fuels and naphthas. APHA colour is analyzed in water white chemicals and solvents, like methanol, VAM, glycols, etc.
4-determination of flashpoint (F.P.)
The flash point of a substance isthe lowest temperature at which a liquid gives off sufficient vapour to form a flammable mixture with air, which can be ignited and will burn momentarily.
Two methods of analysis are used:
- Flash point open cup (o.c.) method. In this method the test cup used is not covered.
- Flash point closed cup (c.c.) method. In this method the flash point is determined in a cup covered with a lid, the flammable vapours can not escape.
Therefore, flash points determined in a closed cup will always be lower than those of the same products analyzed accordind to the open cup method.
5-test for contamination by hydrocarbons
When a mixture of hydrocarbons and methyl alcohol is diluted with a woter, a milky, cloudy solution develops, which turbidity is caused by the hydrocarbons.
Execution of this test.
1 m2 of the surface of the tank wall is washed with cottonwool and hydrocarbon-free methanol. After each washing, the methanol is transferred from the cottonwool into a Nessler tube by pressing. As soon as this tube is filled with about 15 cm3 methanol, 45 cm3 distilled water is added. The mixture is shaken and must stand for 20 minutes.
Thereupon, the contents of the Nessler tube is compared with a so-called blank tube filled with 60 cm3 distilled water. When the mixture in the sample tube is cloudy or not completely clear, hydrocarbons are still present on the surface of the tank wall. This means that the surface must be washed a second time and tested again.
6-test for contamination by chloride
The principle of the chloride test is that chloride ions together with silver nitrate in the presence of nitric acid form a white precipitate of silver chloride. Silver chloride is insoluble in water and methanol, so that the turbidity which has developed in the test liquid, is a measure for the presence of chloride.
7-test for contamination by water
The principle of the test for contamination by woter is that a special paste is applied on the sounding tape. If the colour of the paste is changed it means that some quantity of water is presenced in the cargo.
3 TOXICITY AND OTHER HAZARDS
3.1 GENERAL CONCEPTS AND EFFECTS OF TOXICITY
Toxicity of cargoes in general
3.1.1 most of the cargoes on tankers have some hazardous properties.
3.1.2 poisoning may occur orally, through inhalation or by skin contact.
3.1.3 poisoning may be acute or chronic.
3.1.4 exposure to oil, chemical or gas can have acute or chronic effects on a person’s health.
3.1.5 “acute” effect is defined as effect of single exposure of short duration to relatively high concentration of vapour.
3.1.6 “chronic” effect is defined as accumulative effect of prolonged exposure to relatively low concentrations of vapour over a long duration of time.
3.1.7 the vapour from some cargoes may have both acute and chronic effects, whilst others may have one or the other more prominent.
3.1.8 what are systemic poisons and irritants? It is non-observance of precautions of measures systematicaly!
3.1.9 The toxicity of a substance is difficult to measure and that it is therefore rated on the basis of studies performed on animals and extrapolated for the human body.
Hazard to human health by oral intake:
LD50 (laboratory mammal):
Highly hazardous………………….. less than 5 mg/kg
Moderately hazardous…………….…………. 5 – 50 mg/kg
Slightly hazardous…………………………... 50 – 500 mg/kg
Practically non-hazardous…………………... 500 – 5000 mg/kg
Non-hazardous……………………………… greater than 5000 mg/kg.
Examples of LD50 (mg/kg):
Hydrocyanic acid 10
3.1.10 def. The terms and explain their significance:
1-threshold limit value (TLV) The time-weighted average concentration of a substance to which workers may be repeatedly exposed, for a normal 8-hour workday or 40-hour workweek, day after day, without adverse effect. (See also Permissible Exposure Limits)
The term TLV has been in use within the industrymfor a number of years and is often expressed as a Time Weighted Average (TWA). The use of the term Permissible Exposure Limit is becoming more commonplace and refers to the maximum exposure to a toxic substance that allowed by an appropriate regulatory body. The PEL is usually expressed as a TWA, normally averaged over an eight hour period, or as a Short Term Exprosure Limit (STEL), normally expressed as a maximum airborne concentration averaged over a 15 minute period. The values are expressed as parts per million (ppm) by volume of gas in air (ISGOTT 16.1).
Aceticacid 10 ppm, Benzene 10 ppb plus skin absorption, Chlorine 1 ppm, Nicotine 0.07 ppm plus skin absorption, n-Pentane 600 ppm, Toluene 100 ppm plus skin absorption.
This is specific concentration of liquid’s vapour when you can feel the odour of that liquid with your nose. For example, PHENOL the odour threshold is 0.05 ppm but ACRYLONITRILE the odour threshold is several hundred ppm varying with individuals.
You have all the time to remember that the absence of smell/odour should never be taken to indicate the absence of gas. METHANE has no odour, for example.
3.1.11 cargoes also may be harmful to the environment
There are five points under which Marpol Convention was developed and adopted:
1- Marine pollutants discharged into the sea are rigorously controlled and are only permitted under the specific condition depending on the type of ships and their tonnage.
2- There are ‘special areas’ where all discharge are controlled or prohibited.
3- Each state is obliged to provide port reception facilities for the reception and treatment of polluting substances.
4- Each master must have on board a special record book which must be kept up to date, specifying all cargo loading and unloading operations.
5- Consequently, the designs of ships, as well as, their equipment must, in the future, satisfy those very specific requirements.
3.2 FIRE HAZARDS
The material relating to fire theory and control need only be a brief review, as all participants will have attended an approved fire-fighting course (regulation V/1 of STCW).
3.2.1 the three essentials necessary for a fire to commence as:
2-flammable material (fuel)
3-source of ignition
Sometimes it is represented as a so called ‘fire treangle’, and also as a ‘fire ring’ having three sectors which are named as a ‘oxygen’. flammable material’ and ‘ignition source’.
3.2.2 when flammable vapour is mixed with oxygen (usually from the atmosphere) an explosive mixture may be produced
3.2.3 the ability of petroleum to generate flammable vapour is a major for starting a fire
3.2.4 The ability to vaporize as volatility
The quantity of gas available to be given off by a petroleum liquid depends on its volatility which is frequently expressed for purposes of comparison in terms of Reid Vapour Pressure (RVP): more
RVP than more higher volatility. As you know the RVP test is related with a standard apparatus and in a closely defined way. RVP is useful for comparing the volatilities of a wide range of petroleum liquids. The volatility (i.e. the tendency of the liquid or petroleum product to produce gas) is characterised by the vapour pressure. There is also a tendency for this gas to re-dissolve in the liquid, and an equilibrium is ultimately reached with a certain amount of gas evenly distributed throughout the space. The True Vapour Pressure (TVP) or bubble point vapour pressure is the equilibrium vapour pressure of a mixture when the gas/liquid ratio is effectively zero. As the temperature of a petroleum mixture increases its TVP also increases and more vapours of liquid is produced.
3.2.5 volatility increases with temperature and reaches a maximum at the boiling temperature of the petroleum
3.2.6 the concentration of hydrocarbon vapour present in air is used to define “flammable range”:
flammable range = UFL – LFL (% by vol.)
3.2.7 the working flammable range of a mixture of petroleum vapour and air can be taken to be from 1% to 10% by volume
so flammable range = 10 – 1 = 9% by vol.
It is because that flammable limits % vol. Hydrocarbon in air are:
Gas: UFL: LFL:
Propane 9.5 2.2
Butane 8.5 1.9
Pentane 7.8 1.5
3.2.8 The flammability diagram
When an inert gas is added to a hydrocarbon gas/air mixture the result is to increase the lower flammable limit hydrocarbon concentration and to decrease the upper flammable limit concentration. These effects are illustrated in Fig. ,which should be regarded only as a guide to the principles involved.
Every point on the diagram represents a hydrocarbon gas/air/inert gas mixture. Hydrocarbon gas/air mixtures without inert gas lie on the line AB. ( pure air is represented by the point A). Points to the left of AB represent mixtures with their oxygen content further reduced by the addition of inert gas.
The LFL and UFL mixtures for hydrocarbon gas in air are represented by the points C and D. As the inert gas content increases, the flammable limit mixtures change as indicated by the lines CE and DE, which finally converge at the point E. Only those mixtures represented by points in the shaded area within the loop CED are capable of burning.
When an inerted mixture, such as that represented by the point F, is diluted by air its composition moves along the line FA and therefore enters the shaded area of flammable mixtures, meanwhile mixture, such as that represented by point H, do not become flammable on dilution. Note that it is possible to move from a mixture such as F to one such as H by dilution with additional inert gas (i.e. purging to remove hydrocarbon gas).
3.2.9 the flashpoint of an oil indicates the lowest temperature as which the oil will give off sufficient hydrocarbon vapour to form a flammable gas mixture with air near the surface of the oil. Therefore, we can say that flash point is also the upper temperature explosive limit only for the many kind of crude oil.
3.2.10 only the vapour from a flammable material will combine with oxygen to produce fire
3.2.11 an explosive mixture may be produced when chemical cargo vapours are mixed with air
An explosion can be described as a sudden, violent event accompained with noise, fire and figh pressure, which has a destructive effect on its surroundings. Explosion can be distinguished as follows:
-physical explosion: a sudden expansion, mostly of a gas, whereby pressure increase can no longer be caught by the (closed) drum (steam boiler explosion, explosion of a cylinder with compressed nitrogen);
-chemical explosion: a rapid, exothermic, chemical reaction, mostly accompanied with temperature and pressure increase and the setting free of gases, whereby energy is supplied by the reaction itself.
3.2.12 corrosive liquids can become flammable and produce flammable gases when in contact with certain materials
HYDROGEN GAS (H2) is EXPLOSIVE e.g.!
3.2.13 a mixture of vapour and air will only ignite and burn if its composition is within the “flammable range”
3.2.14 within the flammable/explosive range, if a heat source is introduced, then it will result in a fire
3.2.15 the sources of ignition as:
Minimum energy for ignition of H.C. in air is 0.2 mJ (= 2 Watt x 0.0001 sec.)
Sources of ignition are:
-liquid in air
-stable substances 400 – 600 oC
-octane 220 oC
-thermite-reaction Al ON Fe2O3
3.2.16 static electricity can arise when two dissimilar materials (solids, liquids or gases) come in contact and charge separation occurs at the interface
When two different materials, suited for the purpose, are brought into contact with each other in a certain way, an electric charge will develop in each of the materials. These charges are of the same size, but is positive and negative: so, the sum of both charges is nil. These electric charges, which stay behind on the material, are called static electrical charges, and we are here dealing with the phenomenon of static electricity. This in contrast with the best-known form of electricity which expresses itself in electric currents in conductive materials. When these materials are separated, an electric field develops between the positive material and the negative material. The ‘accumulated’ electricity will try to discharge itself in order to neutralize the electric field. An electric field can also develop when an electrically charged material approaches a non-charged material.
Discharge often takes place in the form of sparks which, generally, have sufficient energy to ignite explosive vapour/air mixtures.
3.2.17 static electricity can cause sparks capable of igniting flammable mixture
3.2.18 list causes of electrostatic charge generation as:
1-flow of liquids through pipes or filters
2-setting of solids or immiscible liquids through a liquid
3-ejection of particles or droples from a nozzle
4-splashing or agitation of a liquid against a solid surface
5-vigorous rubbing together and subsequent separation of certain synthetic polymers
Person and objects:
- walking over poorly conductive surface
- charged clouds (fog)
- touching of charged objects
- pure gases - NO
- particles or droplets - YES
o sandstorms, hail
o solid CO2 in carbondioxide
- depending on:
waterdroplets in H.C.
solid particles (rust, sludge etc.)
3.2.19 some tanker operations can give rise to electrostatic charge generation
3.2.20 examples of such tanker operations:
- cargo pumping
- cargo tank cleaning
- cargo tank steaming, etc.
3.2.21 certain cargoes are accumulators of static electricity because of their low conductivity
Light destillates: Pure Hydrocarbons 10-3 pS/m, Xylene 10-2 pS/m, Toluene 1 pS/m, benzene 5 pS/m, heptane 7 pS/m;
Propane 50 pS/m
Crude oill – from 103 pS/m up to 105 pS/m
Acetone 105 pS/m
Butanol 106 pS/m
3.2.22 the three essentials necessary for a fire to commence, stated in 3.2.1 above, may be represented by the side of a triangle, and the complete triangle represents a fire or an explosion
3.2.23 the way to prevent a fire is to prevent the formation of such a triangle
3.2.24 the removal of any side of the fire of the fire triangle will extinguish the fire
3.2.25 removal of the flammable material is usuall not possible with petroleum in bulk
3.2.26 it is essential to keep ignition sources away from cargo area, where flammable vapours are likely to be present
3.2.27 it is essential to avoide the entry of flammable vapours into areas where ignition sources are present, such as living accomodation, engine-room, galley, etc.
3.2.28 The use of inert gas in cargo tanks can reduce the oxygen content below that necessary to produce a flammable mixture
If content of oxygen is reduced flammable range is reduced, too.
3.2.29 Starving a gas fire by stopping the source of gas leak may be the most effective way to control a gas fire
3.2.30 Covering the surface of a flammable material with a blanket of inert material will prevent oxygen from making contact with the vapours from the flammable material
3.2.31 Water in sufficient quantity can provide cooling
3.2.32 Compared with oil and other hydrocarbons, some liquid chemicals have unusual properties with regard to fire-fighting procedures
3.2.33 cargo properties reffered to under objective 3.2.32:
with oxyding agents
with salt or fresh water
with other chemicals.
3.3 HEALTH HAZARDS
3.3.1 The hazards to health of:
1-skin contact with liquid petroleum
2-ingestion (swallowing) of liquid petroleum
3-inhalation (breathing) of liquid petroleum
4-inhalation of petroleum vapour
5-compounds of lead contained in the cargo
3.3.2 Describe toxic effect on personnel of skin contact with and ingestion (swallowing) of petroleum liquid and inhalation (breathing) of petroleum vapour
Many petroleum products, especially the more volatile ones, cause skin irritation and remove essential oils from the skin, leading to dermatitis. They are also irritating to the eyes. Certain heavier oils can cause serious skin disorders on repeated and prolonged contact.
Direct contact with petroleum should always be avoided by wearing the appropriate protective equipment, especially impervious gloves and goggles.
The risk of swallowing significant quantities of liquid petroleum during normal tanker and terminal operations is very slight. Petroleum has low oral toxicity to man, but when swallowd it causes acute discomfort and nausea. There is then a possibility that liquid petroleum may be drawn into the lungs during vomiting and this can have serious consequences, especially with higher volatility products such as gasolines and kerosenes.
Breathing of petroleum vapour
The main effect of petroleum gas on personnel is to produce narcosis. The symptoms include headache and eye irritation, with diminished responsibility and dizziness similar to drunkenness. At high concentation these lead to paralysis, insensibility and death.
The human body can tolerate concentations somewhat greater than the TLV for short periods. The following are typical effects at higher concentrations:
0.1% vol. (1,000 ppm)
Irritation of the eyes within one hour.
0.2% vol. (2,000 ppm)
Irritation of the eyes, nose and throat, dizziness and
Unsteadiness within half an hour.
0.7% vol. (7,000 ppm)
Symptoms as of drunkennes within 15 minutes.
1.0% vol. (10,000 ppm)
Rapid onset of ‘drunkenness’ which may lead to unconsciousness and death if exposure continues.
2.0% vol. (20,000 ppm)
Paralysis and death occur very rapidly.
3.3.3 Skin contact with liquid petroleum causes irritation and dermatitis because of the removal of essential natural skin oils
3.3.4 Ingestion of liquid petroleum into the stmach causes acute discomfort and nausea
3.3.5 If the liquid is inhaled into the lungs there is a serious risk of suffocation through interference with the normal oxygen/carbon dioxide transfer taking place during breathing
3.3.6 The liquid ingested will tend to vaporize and the vapour could be inhaled into the lungs
3.3.7 Inhalation of petroleum vapour will produce narcosis, the main symptoms being headache/irritation and dizziness, with very high concentrations leading to paralysis,insensibility and very possible death
3.3.8 The vapours from some chemicals are toxic by inhalation
3.3.9 Some chemicals or their vapours are toxic by absorption through the skin
3.3.10 Effects of explosure involving dangerous chemicals are given in the ICS or other Cargo Data Sheets (CDS)
3.3.11 The action to be taken in an emergency is indicated in the Data Sheets, in the form of “If this happens…do this”
3.3.12 When providing first aid, personnel should be aware of the list of “don’ts”, including:
1-do not attend to victim unless it is safe to do so
2-do not attempt to do more than necessary
3-do not delay in summoning for help and informing the master
4-do not enter the enclosed spaces unless you are a trained member of a rescue team acting upon instruction
3.3.13 All personnel should be familiar with the health data set out in the Data Sheets for the cargoes carried
3.3.14 Remember that cargo vapours in sufficient concentration will exclude oxygen and, even if not toxic, may cause asphyxiation
3.3.15 The oxygen content of air is 21% by volume (21.7%)
3.3.16 The oxygen content in enclosed spaces may become lower
3.3.17 The reasons of oxygen deficiency in an enclosed space could be:
1-an inert atmosphere
2-displaced oxygen due to presence of cargo vapour
3.3.18 In certain wind conditions vented gases may descend down, making the atmosphere on open deck harmful due to:
1-presence of gases in harmful concentration
3.3.19 If harmful conditions on deck exist:
- all non-essential work on deck should cease and
- only essential personnel should remain on deck, taking all appropriate precautions
3.3.20 The symptoms of the effect of oxygen deficiency as asphyxia:
- at levels below about 19%:
o general indisposition
o noises in the ears
- at levels below 16%:
o unconsciousness, and
o if the victim is not removed quickly, permanent brain damage and death will result.
3.3.21 The reliance should not be placed on symptoms for indicating an oxygen-deficient atmosphere
3.3.22 Persons have varying susceptibility to oxygen deficiency but that all will suffer if the oxygen content drops below 16% by volume
3.3.23 If oxygen is less than 21% an atmosphere may be extremely dangerous unless it is known which gas has replaced the oxygen.
Toxicity of inert gas
3.3.24 The main hazard associated with inert gas is its low oxygen content, but that it may also contain toxic gases
3.3.25 The main toxic constituents of inert gas:
- low oxygen content
- carbon monoxide has a TLV – TWA of 50 ppm
- nitrous gases:
o nitrogen monoxide (NO), TLV of 25 ppm (vol.)
o nitrogen dioxide (NO2), TLV of 5 ppm (vol.).
3.4 HAZARDS TO THE ENVIRONMENT
3.4.1 def. “pollution” as inconvenience or damage, caused by human activities, animals, plants and to our environment as a whole, by spreading of hydrocarbons and chemical compounds to air, water or lend
3.4.2 a major oil pollution can harm other industries like fishery, tourism, etc.
3.4.3 crude oil tankers, product tankers and chemical tankers are chiefly responsible for marine pollution
o about 700,000 tonnes a year
o dry docking (30,000 tonnes)
o non- tanker accidents (20,000 tonnes)
3.4.4 cargoes in tankers may be harmful to the environment in different ways:
o blanket the surface interfering with the oxygen exchange between the sea and the atmosphere as result
o blanket the seafloor interfering with growth of marine life as result
o toxic into the sea food
o deposition on tidal mud flats.
3.4.5 most chemicals carried represent a pollution risk:
o damage to living resoutces
o human health harm
o reduction of amenities.
3.4.6 hazards caused to the environment, covering the effect on human and marine life from the release of oil, chemicals or gases
o bioaccumulating substances are liable to produce tainting of seafood
o bioaccumulated to significant extent substances can produce a hazard to aquatic life or human health
o damage to living resources
o hazard to human health by skin and eye contact or inhalation
3.4.7 explain the effect that the specific gravity and solubility of the cargo have on the hazards to the environment in the event of a spilage
o more heavier than sea water substances sinkks
o more lighter than sea water substances floats
o non – soluble floating substances spread on a huge area producing a vapour cloud
o if a fully refrigerated liquid is spilled the rapid evolution of vapour occures
o spillage of a liquid gas from a pressure vessel:
¨ the high pressure at release quickly falls to ambient, and this results in extremely rapid vaporisation. This is called flash evaporation.
3.4.8 the effect of the cargo vapour pressure and atmospheric conditions on the hazards to the environment:
o TVP of different liquid cargoes depends on the ambient temperature: temperature increased ® TVP also increases
o If TVP exceeds atmospheric pressure, the liquid commence to boil, producing vapour – in – air mixtures (vapour cloud)
VAPOUR + AIR ® FLAMMABLE
3.4.9 the dangers arising from a vapour cloud drift as potential fire and health hazards
The dangers arising from a vapour cloud drift as potential fire and health hazards.
Cold liquid can cause frostible onhuman tissue and to the environment.
3.5 REACTIVITY HAZARDS
3.5.1 chemical cargo may react in a number of ways, such as:
1-with itself (self reaction)
4-with another cargo
5-with other materials
3.5.2 examples of each of the above reactions
- polymerisation, for example, is self reaction. (C = C) and (C º C) polymerisation is a chemical reaction whereby two or more molecules of the same substance monomer combine with one another, so that a new compound polymer develops of the same gross composition as the original monomer, however, with a double or multiple molecular weight. Example: n(CH2 =CH2) ® (-CH2-CH2-)n
- the combination of an element with oxygen is called an oxide, and the phenomen which is produced by this oxidized compound an oxidation reaction.
- Autoxidation is a chemical reaction whereby the substance itself produces the oxygen for oxidation. But autoxidation reactions are started by oxygen from the air.
(eg. DIETHYL ETHER and other ETHERS
- some substances can combine with water or can be decomposed by water, as a result of which either a hazardous situation arises or the quality of the product strongly changes, or products develop which cause a corrosion of materials. In this case, contamination with water must be prevented.
(eg. Decomposition with water under the formation of acids.
FATS and GLYCERIDES = = = > fatty acids
- to avoid dangerous chemical reaction between different kinds of cargoes there is the cargo compatibility chart.
- Hazardous chemical reactions with metals can occur with substances which form acetylides with these metals. Acetylides are EXPLOSIVE! Examples: Ethers, Epoxides.
3.5.3 reactivity data of chemicals are given in the ICS or other Cargo Data Sheets:
There is “Handling and storage recomendations” in the CDS, consisting of two parts:
o unsuitable materials, and
o suitable materials
3.5.4 polymerization is the formation of larger molecules as a result of self-reaction
Polymerisation takes place when a single molecule (a monomer) reacts with another molecule of the same substance to form a dimer. This process can continue until a large-chain molecule is formed, possibly having many thousands of individual molecules (a monomer). The process may be catalysed by the presence of oxygen (or other impurities) or by heat transfer during cargo operations.
During the transport the polymerisation reactions have to be prevented to avoid problems such as heat generation, formation of a layer of solid polymer on the innerside of the roof of the cargo tank, formation of solid particles which block the pumps, etc.
3.5.5 the effects of temperature on the reactivity of cargoes and polymerization:
- increasing 10oC ® reactivity of cargoes be doubled
- polymerization: -temperature increases
-toxic gases produces.
3.5.6 the presence of impurities may act as catalysts on the reactivity of cargoes and polymerization
impurities act as “active centres” to start polymerization.
3.5.7 polymerization may, under some circumstances, be dangerous
Polymerization may be catastrophic to the ship, and when transporting such liquids it is important to monitor the temperature of the cargo at certain intervals. A rise in temperature may indicate that a reaction is in progress, and some measures should be taken to bring the situation under control. Such liquids will normally be added an inhibitor and may require inerting, and the shipper should give a clear loading instruction and voyage instruction in relation to control of inhibitor.
3.6 CORROSION HAZARDS
A brief introduction:
- corrosive effects of chemicals on human tissues and on the ship’s equipment and structure are very dangerous!
- some highly corrosive cargoes will require special materials for tank construction and cargo systems.
3.6.1 some cargoes may be corrosive to human tissue and to a ship’s equipment and structure
When handling corrosive liquids especially three danger details should be born in mind:
1 -danger of corrosion of ship or equipment
2 2 –danger of fire
3 –health hazards.
Corrosive products can only be transported in ships equipped with special tank-materials, special coatings and with gaskets used to the purpose.
3.6.2 instructions about the use of protective clothing should be observed (Tanker Safety Guide requirements).
The liquids will when they come in contact with skin or tissue damage or even destroy this. The wounds will be painful and heal slowly. Eyes and mucous membranes are very sensitive to corrosive liquids, so therefore do not neglect the use of protection equipment.
3.6.3 care should be taken to ensure that unsuitable materials are not introduced into the cargo system
Corrosion is the etching or attack of metals on the surface. Corrosion can have different causes:
- a chemical corrosion of metals only occurs at high temperatures, whereby the metal is oxidized by oxygen.
- an electrochemical corrosion of metals occurs at low temperatures under the influence of water (humidity) and oxygen. Cargo and material compatibility see in the CDS (unsuitable or suitable materials)
3.6.4 the effect of concentration and evolution of hydrogen on corrosion
When corrosive liquids attack metal, fumes are evolved which may be flammable or explosive if mixed with air. Especially acids evolve free hydrogen, which is very explosive mixed with air, and do not forget that corrosive liquids themselves may be flammable and may cause auto ignition in saw dust, rags or other materials.
Safe working practices followed to avoid coming in contact with corrosive cargoes and that appropriate protective clothing is used and precautions are taken while handling such cargo.
3.7 HAZARDS FROM LIQUEFIED GAS
o Toxicity (poisoning)
o Asphyxia (sufocation)
o Low temperature (frostible)
o Chemical burns
3.7.1 liquefied gas cargoes are transported at or close to their boiling point
3.7.2 the boiling temperatures of these cargoes range from –162 oC for methane to 0 oC for butane
3.7.3 low temperatures can cause cold burns, which may damage skin and tissue when in direct contact with cold liquid or vapour
health data – cargo liquid (effect on the human body)
3.7.4 these low temperatures can cause brittle fracture if cold cargo comes in sudden contact with metals
3.7.5 liquefied gas cargoes give off vapour readily because they are boiling
3.7.6 cargo vapour can be lammable, toxic or both
3.7.7 cargo vapour in sufficient concentration will exclude oxygen and may cause asphyxiation whether the vapour is toxic or not
In general, such a problem is limited to enclosed spaces. Oxygen deficiency in an enclosed space can occur with any of the following conditions:
o When large quantities of cargo vapour are present
o When large quantities of inert gas or nitrogen are present, and
o Where rusting of internal tank surfaces has taken place.
For the above reasons, it is essential to prohibit entry to any space until an oxygen content of 21 per cent is established.
3.7.8 an explosive mixture may be produced when most cargo vapours are mixed with air
All liquefied gases transported in bulk by sea, with the exception of chlorine, are flammable. The vapours of other liquefied gases are easily ignited. The exception to this is ammonia hich requires much higher ignition energy than the other flammable vapours. Accordingly, fires following ammonia leakage are less likely than with the other cargoes. However, in practice it is usual to consider the possibility of ammonia ignition and to act accordingly.
3.7.9 the vapours from some liquefied gas cargoes are toxic by inhalation
3.7.10 some toxic gases caried in gas tankers can be absorbed into the body through the skin
Toxicity is the ability of a substance to cause damage to living tissue, including impairment of the nervous system. Illness or, in extreme cases, death may occur when a dangerous gas or liquid is breathed, taken orally or absorbed through the skin. (In general, the term ‘toxic’ and ‘poisonous’ can be considered synonymous.)
3.7.11 some gases are caustic and can damage human tissue (the skin, lungs, throat and eyes.) The effect is more known as chemical burns (corrosive/irritant).
Chemical burns can be caused by ammonia, chlorine, ethylene oxide and propylene oxide. The symptoms are similar to burns by fire, except that the product may be absorbed through the skin causing toxic side-effects. Chemical burning is particularly damaging to the eyes.
o A burning pain with redness of the skin
o An irritating rash
o Blistering or loss of skin
o Toxic poisoning.
o Attend first to the eyes and skin
o Wash the eyes throughly for ten minutes with copious amounts of fresh water
o Wash the skin thoroghly for ten minutes with copious amounts of fresh water
o Cover with a sterile dressing.
Otherwise, the treatment is as for burns, details of which are contained in the IMO Medical First Aid Guide.
On some gas carriers deck showers and eye baths are provided for water dousing; their locations should be known.
some cargoes in liquefied gas tankers are reactive and may react in a number of way
Mild carbon steel