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Reactivity of noxious liquid chemicals while carrying at sea

A chemical may react in a number of ways; with itself, with water, with air, with other chemicals or with other materials.

Self-reaction: The most common form of self-reaction is polymerisation. Polymerisation generally results in the conversion of gases or liquids into viscous liquids or solids. It may be a slow, natural process which only degrades the product without posing any safety hazards to the ship or the crew, or it may be a rapid, exothermic reaction evolving large amounts of heat and gases.

Heat produced by the process can accelerate it. Such a reaction is called a run-off polymerisation that poses a serious danger to both the ship and its personnel. Products that are susceptible to polymerisation are normally transported with added inhibitors to prevent the onset of the reaction.

chemical tanker navigation at sea
An inhibited cargo certificate should be provided to the ship before a cargo is carried. The action to be taken in case of a polymerisation situation occurring while the cargo is on board should be covered by the ship's emergency contingency plan.

Reaction with water

Certain cargoes react with water in a way that could pose a danger to both the ship and its personnel. Toxic gases may be evolved. The most noticeable examples are the isocyanates; such cargoes are carried under dry and inert condition. Other cargoes react with water in a slow way that poses no safety hazard, but the reaction may produce small amounts of chemicals that can damage equipment or tank materials, or can cause oxygen depletion.

Certain chemical cargoes, mostly ethers and aldehydes, may react with oxygen in air or in the chemical to form unstable oxygen compounds (peroxides) which, if allowed to build up, could cause an explosion. Such cargoes can be either inhibited by an anti-oxidant or carried under inert conditions.

Reaction with other cargoes

Some cargoes react dangerously with one another. Such cargoes should be stowed away from each other (not in adjacent tanks) and prevented from mixing by using separate loading, discharging and venting systems. When planning the cargo stowage, the master must use a recognised compatibility guide to ensure that cargoes stowed adjacent to each other are compatible.

Reaction with other materials

The materials used in construction of the cargo systems must be compatible with the cargo to be carried, and care must be taken to ensure that no incompatible materials are used or introduced during maintenance (e.g. by the material used for replacing gaskets). Some materials may trigger a self-reaction within the product. In other cases, reaction with certain alloys will be non-hazardous to ship or crew, but can impair the commercial quality of the cargo or render it unusable.

Heat adjacent

The maximum temperature of adjacent cargo permitted for each cargo to be loaded shall be obtained from shippers when handling heated cargo. In addition, care shall be taken to avoid indirect heating of adjacent cargoes and bulkheads during hot water washing of adjacent tanks.

Related info

  1. Toxicology and associated hazards onboard chemical tankers

  2. Toxicity is the ability of a substance, when inhaled, ingested, or absorbed by the skin, to cause damage to living tissue, impairment of the central nervous system, severe illness or, in extreme cases, death. The amounts of exposure required to produce these results vary widely with the nature of the substance and the duration of exposure to it. ....

  3. Hazards of vapour given off by a flammable liquid while carrying at sea

  4. Vapour given off by a flammable liquid will burn when ignited provided it is mixed with certain proportions of air, or more accurately with the oxygen in air. But if there is too little or too much vapour compared to the air, so that the vapour-and-air mixture is either too lean or too rich, it will not burn. ....

  5. Reactivity of various noxious liquid chemicals

  6. Self-reaction: The most common form of self-reaction is polymerisation. Polymerisation generally results in the conversion of gases or liquids into viscous liquids or solids. It may be a slow, natural process which only degrades the product without posing any safety hazards to the ship or the crew, or it may be a rapid, exothermic reaction evolving large amounts of heat and gases. .....

  7. Most corrosive chemicals carried onboard chemical tankers

  8. Acids, anhydrides and alkalis are among the most commonly carried corrosive substances. They can rapidly destroy human tissue and cause irreparable damage. They can also corrode normal ship construction materials, and create a safety hazard for a ship.....

  9. Posoning hazards & first aid treatment

  10. The poison is a very toxic substance which when absorbed into the human body by ingestion, skin absorption, or inhalation produces a serious or fatal effect. Poison may enter the human body orally, by inhalation, or by skin contact. After being absorbed by the body it may affect certain organs or give a general poisonous effect. Lately the cancerogene effects of some industrial chemicals have been noticed. This has led to significant reductions of hereto accepted TLV- values in many countries.....
  11. Specific gravity,Vapour pressure and boiling point,Electrostatic charging & measuring Viscosity
  12. Tanks on a Chemical Tanker are normally designed to load cargoes of a higher specific gravity than an oil tanker. Very often the design strength differs between groups of tanks on the same ship. ....

  13. General precautions onboard chemical tankers

  14. Additional precautions for specific cargoes are necessary and should also be incorporated in the ship’s cargo handling procedures....

  15. Mooring precautions onboard chemical tankers

  16. The consequences of a chemical tanker ranging along a jetty or breaking away from a berth could be disastrous, especially during a cargo transfer involving multiple different chemicals. Correct and sufficient mooring is therefore of the utmost importance.

  17. Berth precautions onboard chemical tankers

  18. If an unauthorised craft comes alongside or operates in an area which may create a danger, it should be reported to the port authority and, if necessary, cargo transfer operations should cease. .....

  19. Cold weather countermeasures, avoiding electric storms

  20. During cold weather, precautions should be taken to prevent equipment and systems from freezing. Attention should be given to pneumatic valves and control systems, fire lines and hydrants, steam driven equipment, cargo heating systems, pressure/vacuum valves etc......

  21. Restriction on using radio equipments and other mobile devices in cargo working areas

  22. During medium and high frequency radio transmissions significant energy is radiated, which can create a danger of incendive sparking by inducing an electrical potential in unearthed steelwork.

  23. Securing cargo tank lids and required safety precautions

  24. Improper closing and sealing of cargo tank hatches can be a major cause of cargo contamination. A properly closed and sealed tank hatch/opening will prevent sea water ingress and maintain a positive pressure Nitrogen blanket in the ullage space. ....

  25. Means of access (gangways or accommodation ladders) safety precautions

  26. Emergency towing-off wires ( fire wires) ,Ship’s readiness to move Deckhouses and superstructures safety precautions .....

  27. Precautions against static electricity

  28. Static electricity is generated by friction that occurs between different materials during relative motion. Electrostatic charges can then accumulate in materials which are poor conductors of electricity or which are good conductors but are insulated.....

  29. Cargo tank entry safety precautions

  30. On chemical tankers the entry of personnel into cargo tanks is a more common practice than on oil tankers as a result of the requirement for inspections between grades etc; despite this, it is essential that the necessary checks are conscientiously made and recorded prior to entry in order to ensure the safety of personnel, enclosed space rescue equipment must be made ready for immediate use. .....

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