5. TRANSPORT AND STORAGE
1. What happens during the transport of chemicalsLarge amounts of chemicals and other products which can cause hazards to human health and harm to the environment are used at places of work.
Industrial production takes place, and raw materials are located, all over the world. Transport is necessaary for products to reach consumers. The transport and storage of dangerous chemicals and goods has increased with technical development and production development.
An accident occuring during the transport of dangerous goods can lead to catastrophic consequences: laws and recommendations have been established to protect the society and the environment. But they can not be effective if you, whether you are an employer, worker, transporter or inspecting authority, do not share the responsibility and follow existing recommendations and guidelines of transport and storage, in order to avoid unnecessary risks.
The hazardous properties of products or chemicals should be clearly stated so that people of all stages of the transport chain are aware of them. This information should always follow the goods so that people can recognize the risks, avoid accidental mishandling and have the right kind of the personal protection at their disposal in case of leakage.
Dangerous goods can be transported without causing unnecessary hazards if handled properly and with care.
1.1 What are dangerous goods?Dangerous goods can be explosive, flammable, toxic, radioactive, corrosive or harmful in some other way to humans, animals or the environment. The environment includes other goods in transport, the transport vehicle, buildings, soil, roads, air, waterways and nature in general.
The empty containers and packages of dangerous goods can present the same hazards as the chemical substance or product they contained and should also be regarded as dangerous goods.
50 per cent of transported goods are dangerousUnited Nations statistics show that half of all goods transported belong to the category of dangerous goods. Petroleum products transported by tankers form a large proportion of all transported goods, but road and railway transport is also significant.
For example, 85% of chlorine, which is one of the very dangerous chemicals, is transported by rail.
Large amounts of other highly dangerous goods, such as hydrochloric acid, sulphuric acid, sulphuric dioxide, nitric acid, phenol and methanol are transported regularly.
Small drains make a riverMajor accidents cause extensive damage but that is not all. We forget easily that small amounts of oil, gasoline, battery acids and refrigerator fluids are released to environment daily. Even small but frequent wastes from ships, households, cars or agriculture increase the load to the environment. For example one litre of oil can, under unfavorable circumstances, spoil 100 000 litres of drinking water. A spill of hydraulic fluid from a truck can lead to environmental damages.
Recommendations and instructions for the handling, storage and transport of dangerous goods must be clear and unambiguous to avoid harmful or dangerous circumstances.
Transport of dangerous goods does not pose under normal conditions a greater danger than any other transported goods if the responsible persons in the transport chain respect the existing recommendations and laws and are beware of the type of the hazards of the cargo.
1.2 Dangerous situationsThere is always a risk of spillage during the transport of hazardous goods. When incompatible substances mix with each other there is a possibility of a chemical reaction, which can produce enough heat to cause fire or explosion and can release dangerous gases. For example, toxic nitrous oxides are formed when ammonium nitrate (in fertilizers) decomposes in a fire. Another example is the toxic gases which fume off when a spillage of concentrated sulphuric acid is absorbed in sawdust.
Spillages are possible in the following situations:
A chemical substance or preparation may be hazardous in itself when it comes into contact with other chemicals including air, water or humidity. For example, when calcium carbide (used in the production of acetylene and pyrotechnics) comes to contact with water, it releases the extremely flammable gas acetylene (used in welding flame) and creates an explosion hazard.
Careful handling is also important because the magnitude of the involved risk is not always obvious. One kilo of a certain chemical poses a hazard, but it is not necessarily true that ten kilos creates a ten fold hazard. The danger could be the same as for one kilo or it could be higher.
The pressure within sealed packages rises in the heat (sunshine), and can lead to uncontrollable reactions.
Changes in temperatures may affect both the qualities of a cargo and its packing material.
The recommendations on package sizes as well as the load size should be respected.
Common hazards in handling of chemicals are
Four tons of hot, flammable hydrocarbon leaked out of the a plant while maintenance work was in process. A diesel engine was on in the area. The flammable vapour was sucked into the air inlet and the engine started to race. The driver tried to stop the engine by stopping the the fuel supply (usual way of stopping a diesel engine) but without success as burning material was coming in through the the air inlet. Finally there was a flash-back and the flammable liquid was ignited to a fire.
Another frequent incident is this type:
a tank trailer tipped up because of the rear compartments were emptied first. If it is not possible to keep trailer connected to the truck,s driving unit the front comparments should be filled last and emptied first as the normal support cannot alone prevent the trailer from tipping.
2. Classes of dangerous goodsThe United Nations has published a book collecting the work of the Committee of Experts: Recommendations on the Transport of Dangerous Goods. These recommendations aim to present a basic, practical scheme of provisions that will allow national and international regulations governing various modes of transport to develop within it in a certain uniformity. The aim is to enable effective and successive transport and to ensure the safety of people, property, and the environment.
In these recommendations the goods are given an identification number and are divided into the following classes describing the inherent hazards:
To deal with goods having multiple risks a `subsidiary risk' classification is used together with the principal hazard classification.
Substances and articles belonging to classes 1, 2, 4.1, 4.2, 4.3, 5.2, 6.2 and 7 often have more than one hazardous property and are subject to further restrictions.
These goods may be
|Substance or article||Hazards|
|UN Number||Name and description||Class||Subsidiary risk|
|3017||Organophosphorus pesticides, liquid, flammable, flash-point not less than 23°C (Demeton, Fenthion, Parathion)||6.1||3|
|1396||Aluminium powder, uncoated||4.3|
|1005||Ammonia, solution with water, with more than 50% ammonia||2.3||8|
|1789||Hydrochloric acid, solution||8|
2.1 Class 1. ExplosivesThis class contains articles, preparations, and substances such as ammunition, TNT, dynamite, nitrourea, fireworks.
A transport accident involves acute risk of explosion. The pressure wave can be devastating, and flying splinters may cause great damage.
The heat of the blast can result in a fire.
Some substances in this class have toxic properties, e.g. nitroglycerin (in dynamite) is also classified as toxic and can penetrate through the skin.
Transport of Class 1 articles or substances are subject to many restrictions, including quantity and temperature limits. They may also be incompatible with other goods. For example, dynamite should not go with detonators.
2.2 Class 2. GasesThis class contains
Condensed gases are in a liquid state at relative low pressure. The contents are released as liquids which quickly evaporate forming gas clouds.
The size of the cloud can be considerable; for example, 1 litre of liquified petroleum gas (LPG) forms up to 250 litres of gas. LPG, (propane, butane or a mixture of them, `cooking gas')(Class 2.1); propene (2.1); vinyl chloride (2.1); freons; carbon dioxide (2.2); chlorine (2.3 and 5.1); ammonia (2.3 and 8) are commonly used gases in industry and are transported as condensed gases.
Some condensed gases are stored at very low temperatures. They are transported in well- isolated containers called dewars. These must have a loosely covered opening to avoid dangerous overpressure. They pose special hazards due to their low temperature. For example, splashes of liquified nitrogen can cause frostbite and the gas cloud is an asphyxiant.
In a train accident several tank wagons filled with liquified propane turned over spilling their contents. The propane started to evaporate cooling the surroundings to -43oC, which is the boiling temperature of propane. Several persons in the spill area were frozen to death. With good luck and tight security the highly flammable propane gas did not explode.
An example of a dissolved gas is acetylene (Class 2.1). Acetylene cylinders are filled with inert very porous, non-combustible material which is wetted with acetylene.
Aerosols and small receptacles which contain flammable propellant gases belong to this class.
Substances in Class 2 are assigned to one of three categories based on the primary hazard of the gas.
2.2.1 Class 2.1. Flammable gasesThis category includes those gases that at normal pressure and temperature, as a mixture of 13% or less with air, can ignite from a source of fire such as a spark.
2.2.2 Class 2.2. Non-flammable, non-toxic gasesIncluded in this category are gases which might replace oxygen and are asphyxiant (nitrogen, carbon dioxide), or which are oxidizing and may contribute to the combustion of other materials more than air does (pure oxygen is an example).
2.2.3 Class 2.3. Toxic gasesGases which are known to be poisonous or corrosive enough to pose a health hazard belong to this category (carbon monoxide, ethylene oxide, hydrogen sulphide, sulphur dioxide and ammonia). Containers with toxic gases should never be loaded or stored together with food or feedstuffs.
Acidic gases can react with alkaline gases to produce heat and smoke, which may create a fire risk.
Some gases have more than one dangerous property. They can be both flammable and toxic (methyl ether) or corrosive and toxic (hydrogen chloride, phosgene, chlorine).
2.3 Class 3. Flammable liquidsA flammable liquid has the ability to give of, at normal temperatures, vapours which are flammable (e.g., benzene, kerosene, toluene, propanol and various organic solvents used in pesticides). This class also covers mixtures of liquids, as well as liquids containing solids in solution or suspension (paints, varnishes, lacquers, etc.). Petroleum products and crude oil also belong to Class 3.
Flammable liquids pose a risk of fire and explosion, and may lead to expensive environmental clean- up operations (accidents at sea to oil tankers).
The flammability of a liquid depends on several characteristic properties.
Flash-point describes the lowest temperature at which a liquid gives off sufficient amount of flammable gas to form a mixture with air which will ignite when a flame or spark is present. If the flash-point is tested to be not more than 60.5°C, the substance belongs to Class 3.
Many flammable liquids can be charged with static electricity, for example, as result of flowing in a pipe. This makes them both combustible and able to create a spark. Containers should have an earth connection in situations such as refilling the cisterns at petrol stations.
Some flammable liquids have more than one dangerous property. Carbon disulphide is both flammable and toxic, and formaldehyde solutions can be both flammable and corrosive.
2.4 Class 4.1. Flammable solidsThis class consists of solids which are readily combustible, those which may cause or contribute to fire through friction, and self-reactive substances. Sulphur, red phosphorus and nitrocellulose films are common hazardous substances in this class. Examples of self-reactive compounds are azocarbamides, benzene sulphohydrazine and diazonium salts. Sawdust, hay and paper are not spontaneously flammable but are in this class because of incompatibility requirements in loading procedures.
When flammable solids are handled there is a possibility of large amounts of dust being released in the air. These mixtures of dust and air can lead to a dust explosion.
Many flammable solids give off hazardous fumes when they are burned. For example, the fumes of burning sulphur or red phosphorous are toxic and corrosive.
The decomposition of self-reactive substances can be initiated by heat, contact with catalytic impurities (acids, bases, heavy metal compounds), friction or impact. Decomposition may result in the emission of toxic gases and vapours. In order to ensure safety during transport, a self-reactive substance may be desensitized using a diluting agent compatible with the substance.
2.5 Class 4.2. Substances liable to spontaneous combustionLinseed oil (used in paints), copra, oily cotton waste, carbon and white phosphorus are examples of substances which can ignite spontaneously when in contact with air.
These substances are liable to act as a source of ignition for other goods and storage structures.
For example, there is a danger of fire if linseed oil spillages are wiped away with rags which then are left to dry in the air. The rags can stay inactive for days before they actually ignite.
2.6 Class 4.3. Substances which in contact with water emit flammable gasesCarbides are among the substances in Class 4.3. An extremely flammable gas, acetylene, is produced by adding water to calcium carbide. When sodium comes into contact with water it gives off hydrogen gas. The reaction is violent and produces enough heat to ignite hydrogen. Hydrogen burns explosively with such a hot flame that metallic material can start to burn.
Aluminium and magnesium powders, zinc dust and some metal hydrides are in this class.
In addition to the dangers of fire and explosion, goods belonging to this class can react with moisture on human skin and cause burns.
2.7 Class 5.1. Oxidizing substancesIn this class are substances such as chlorates, chlorites, nitrates, nitrites, chromic acid and concentrated hydrogen peroxide solution.
These goods should be carefully handled and protected from heat or friction. An oxidizing substance has oxygen bound into its structure. This is liberated by heating and can react with other materials or enhance fire.
Many substances in this class are sensitive to impurities. Concentrated hydrogen peroxide solution begins to decompose if a few rust flakes happen to fall into the container. The reaction starts slowly but accelerates with time. It gives off oxygen which corrodes metallic materials. This can be devastating in transport by rail.
The decomposition of oxidizing goods can also involve liberation of toxic or corrosive gases, such as nitrogen oxides, which can be recognized from their deep brown to yellow brown colour.
2.7.1 Class 5.2. Organic peroxidesThis class covers peroxides of organic compounds. They should never be transported or stored with combustible goods. Special recommendations and provisions apply to some of the peroxides because of their high reactivity. In addition to the hazards of explosive decomposition and fire, they are sensitive to impact or friction. Many peroxides are toxic and some of them can provoke allergic response or damage the eyes.
2.8 Class 6.1. Toxic substancesSubstances in this class are liable either to cause death or serious injury, or to be harmful when swallowed or inhaled or by skin contact. Toxic substances can be gases, solids or liquids. Toxic gases are listed into the Class 2.3.
Examples of substances in this class are cyanides, arsenic compounds, mercury and lead compounds, nicotine, toluidines, chloroform, aniline and organotin compounds.
In order to compare the various risks involved, LD50 (lethal dose to 50%) and LC50 (lethal concentration to 50%) are used to appraise toxic properties. LD50 means the dose, at which half of the animals exposed (in test laboratory) to the poison die, and LC50 means the concentration which kills 50% of the tested animals after being exposed to the substance, usually by inhalation.
There are agreed limits for the levels of toxicity measured in animal tests, with reference to the route of exposure.
The packing group depends on the amount of the chemical and on the different degrees of health hazard that the chemical poses.
Detailed advice about materials and ways of packing can be found in the United Nations Recommendations on the Transport of Dangerous Goods and in national regulations.
2.9 Class 8. Corrosive substancesThe corrosive substances class is a large one. It can be subdivided into acids, bases and other materials.
Examples of acids include hydrochloric acid, sulphuric acid and acetic anhydride. Sodium hydroxide, potassium hydroxide, sodium carbonate and sodium metasilicate are bases or alkalis. Other corrosive substances include antimony pentachloride (textile impregnation), titanium tetrachloride, aluminium chloride and hypochlorites.
The health hazard varies from corrosive to irritating depending on the type and concentration of the active substance.
The corrosiveness of the substace is determined by its pH which measures the level of acidity or alkalinity. The following scale shows how the substance can be classified as corrosive or irritant:
pH 14 very alkaline (caustic soda) 13 12 11 10 9 8 7 neutral (water) 6 5 4 3 2 1 very acidic (nitric acid)The pH value can often be found on the label or in the documents following the substance.
Some countries require that solutions must be classified, because of the corrosive effects, when the pH value is less than 1.5 or greater than 11.5.
The pH of some common substances in dilute water solutions is given below:
|Concentration||Substance||Smell||pH||Effect on skin|
|1%||Hydrochloric acid||sharp||~0.6||Slight feeling|
|1%||Sodium hydroxide(caustic soda)||none||~13.4||Strong|
|Acids and alkalis are normally transported at very high concentrations,
e.g. 90-95% sulphuric acid, 65% nitric acid, 30% hydrochloric acid, 50%
sodium hydroxide and 50% phosphoric acid. At these concentrations the pH
value is not important, the substances are simply very corrosive.
These substances can attack and corrode many materials, for example, clothe, paper and several metals. Decomposition often produces heat and gases, and in some cases extremely flammable hydrogen gas. The choose of a packing material and loading should carefully planned, because it can be some time before the consequences of corrosive effects are visible.
Accidental mixing of different corrosive materials can in some cases lead to violent reactions, which may give off large amounts of gases.
In the case of strong alkalis ther is a latent period before a burning feeling on the skin is experienced. By then the damage is already done. Skin contact with strong acids produces an immediate feeling. Both types of corrosive substances can cause serious skin damages.
Corrosive material in the eyes requires a very rapid and long rinse with water (for at least 15 minutes) and medical attention.
Corrosive substances can also present other hazards. For example, benzyl chloride is both toxic and corrosive, and cyclohexylamine is both corrosive and flammable.
2.10 Class 9. Miscellaneous dangerous substancesThese are substances and articles which during transport present a danger not covered by other classes.
For example magnetic materials can be classified in this category (magnetism may affect the navigation systems of aeroplanes).
PCBs (polychlorinated biphenyls) are placed in Class 9 because they may damage the environment.
Dry ice (solid carbon dioxide) can evaporate, producing asphyxiant fumes, and displace oxygen in the air in confined places such as cargo holds in ships and storage cellars.
Asbestos can damage the lungs. The effect on health is not immediate; the damage appears after many years. Therefore asbestos is not placed in Class 6.1 but in Class 9.
Concentrated formaldehyde solutions are flammable, but if they are diluted with water the flash- point becomes higher than 60.5°C, which is the limit of flammables. The remaining hazards are still present, such as the allergic reactions caused by formaldehyde.
3. Transport and storage of dangerous goodsWhenever dangerous goods are to be for transported certain measures should be taken to ensure that the potential risks are adequately communicated to all who may come into contact with the goods in the course of the transport. This can be accomplished through marking and labelling of packages to indicate the hazards of the consignment, through including relevant information in the transport documents, and by placing placards on the transport units: containers and vehicles.
3.1. Labels, marking, documentsEach package should be marked with the appropriate shipping name, hazard class and UN number, followed by packing group reference (when available), e.g.:
ALLYL ALCOHOL 6.1 UN 1098 ILabelling is based on the classification of dangerous goods into the 9 classes described above.
Detailed instructions on how dangerous goods should be classified and packed are given in international agreements and national provisions.
Labels should be placed on containers and vehicles so that they are clearly visible.
During the transport of dangerous general goods, the appropriate warning labels should be on every single package.
Only one danger class label should normally be fixed on a package. However, if the substance or article presents more than one significant risk, such as fire and poisoning, the package should bear labels indicating important subsidiary risks.
Special labels indicating the transport conditions are:
The documentation for the transport of dangerous goods should contain:
a) Transport document containing
3.2. Vehicle requirementsTransport by road may take place as bulk materials, or in containers and tanks.
The detailed technical requirements for different transport methods are usually given in national regulations.
The transporter should check that the following documents are attached:
3.3. Incompatible dangerous goodsDetailed instructions pertaining to classified dangerous goods may also restrict the transport of specific goods together in the same vehicle, or the minimum distances between two such packages may be given.
Those loading the goods have to rely on the information found on packages and transport documents. Opening of the transport containers or the packages during the transport or intermediate storage is not permitted.
Once the labelling is properly completed, loading personnel can use the attached key symbols to judge how to construct the load according to regulations and in a safe way.
3.4. Limited quantitiesDangerous goods require special treatment, equipment, extra vehicle crews and supervision when stored, handled, parked, and at places of loading and unloading.
Detailed instructions in international and national provisions specify quantity limits for certain dangerous substances. These maximum package quantities can be transported in one transport unit, and not all of the above-mentioned special precautions need to be applied.
Such limits are given in the UN Recommendations on the Transport of Dangerous Goods. They are adapted and more detailed in the European Agreement Concerning the Carriage of Dangerous Goods by Road (ADR).
4. Organizing safetySafety measures should be considered from the request for transport up to the delivery at the end- point, including the cleaning of the vehicle afterwards.
All levels of personnel involved should be well informed and these people should share the responsibility.
Safety measures should include organizational, personnel and engineering aspects, and co-operation between operational staff during the transport should be emphasized.
Collaboration between the employer and employees is essential. Collaboration with authorities, such as responsible community and health care institutions and Labour Inspectorate is equally important in order to exchange information and plan for emergencies.
4.1. Organizing safety communicationProper communication within the transport chain is the basis for all other safety measures.
Safety activities are targeted to:
The committee could consider emergency planning and safety education. Ideas from both workers and the employer should be encouraged and discussed.
4.2. Organizing safety measuresTransport order, booking
When accepting a transport order, one should already at that point find out whether the batch contains dangerous goods.
If the batch does or is suspected to contain dangerous goods, the consignor should be reminded of the need to label the goods according to regulations and to prepare documents which include instructions in the local language in case of emergency or spillage.
Some companies have developed checklists of different aspects of information, which the consignor can use to describe the load in order to facilitate the communication between different stages of the transport chain.
If the cargo is transported in a tank-container or as bulk transport, a special check should be made that the vehicle is properly equipped, that proper placards are chosen, that the vehicle and its pipes and connections are empty and clean, and that the protective equipment is intended for those hazards the transported goods can cause (such as provision of the right type of filter for the driver's gas mask).
Before leaving the loading place all documents should be checked. Always remove old documents from the vehicle to avoid any misunderstanding in case of an emergency. See that the documents are completed. If passing through customs, check that the emergency instructions are written in the appropriate languages. The packages and containers should not be broken, and the actual amount should be the same as stated in the documents. Dangerous goods should always be well attached to avoid load movements during transport and they should be loaded away from food and animal feedstuffs. Attach the placard to the vehicle.
Remember grounding to avoid static electricity, and personal protective equipment when loading dangerous goods in/from tank-containers.
A sketch of the load showing where the dangerous goods are situated could save time in unloading.
Unloading and re-transport
A check should be made that the documents are always attached to the goods. To avoid unnecessary risks an intermediate storage should be planned, according to the class to which the goods belong, to avoid contacts between incompatible chemicals. A checklist for re-transport helps the workers in the storage area and enhances safety.
Some dangerous goods must be under surveillance at all times, such as explosives, organic peroxides and toluene sulphonic acid. Some other dangerous goods need limited surveillance while parked in a restricted area or isolated place if the amount exceeds specified quantities.
You should check that loaded dangerous goods have not moved and that the packages/containers are not leaking. If there is a spillage follow cleaning instructions described in the attached documents.
Dangerous goods can be delivered only to the authorized persons and should not be left without surveillance.
Check that the name(s) of the goods and the amounts correspond to those in documents. In the case of liquids being transported in a tank-container, check that connections and pipes are not leaking. Supervise the unloading to avoid an overflow.
Do not forget to give the documents to the receiver of the cargo and remember to remove the placards when they are no longer needed.
4.3. ResponsibilitiesIt is the responsibility of the consignor to see that
Annex 1. Common rules that apply to all types
of transport of dangerous goods
BIBLIOGRAPHYThe training module is based on the Swedish education material:
ARBETARSKYDDSNÄMNDEN, Transport av farligt gods, Sjuhäradsbygdens Tryckeri AB, Boras 1985, ISBN 91-574-1346-0
ARBETARSKYDDSNÄMNDEN, Handbok för vägtransport av farligt gods, Stockholm 1993
ILO, International Labour Organisation, Encyclopedia of Occupational Health and Safety, Vol I - III, Geneva 1983
IPCS, International Programme on Chemical Safety and CEC, Commission of the European Communities, International Chemical Safety Cards
Kletz, T.A., What Went Wrong? Case Histories of Process Plant Disasters, Gulf Publishing Company, Houston 1988
UNITED NATIONS, Transport of Dangerous Goods, 8th Ed., New York 1993
UNITED NATIONS, European Agreement concerning the international carriage of dangerous goods by road (ADR) and protocol of signature, New York 1992