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Hazards of carrying noxious liquid chemicals at sea and safety practice

Chemical cargoes may present a fire hazard which will be determined by the flashpoint, boiling point, flammability limits and auto-ignition temperature of the product. The marine pollution hazard will be dependent on several factors that include bioaccumulation and the attendant risk to aquatic life or human health. In addition, release into the marine environment may cause damage to living resources, hazard to human health and consequent reduction of amenities. The air pollution hazard posed by release into the atmosphere may categorised by the emergency exposure limit (EEL) of the substance.

chemical tanker navigation at sea

Watch standing personnel must ensure that no one who is smoking approaches or boards the vessel. Smoking on board must only take place in designated smoking areas. The company policy on drugs and alcohol must be strictly enforced.
Modern Chemical tanker underway
Fig: Modern Chemical tanker underway

Parmanent Noictes

Permanent notices complying with international standards should be displayed in conspicuous spaces onboard, indicating prohibited smoking and use of naked lights areas. Enclosed areas that need to be ventilated prior to entering must also be marked.

Temporary Notices and signals

On arrival at a terminal, and throughout the vessel’s stay at anchorage or alongside, temporary notices are to be displayed at the point of access or other conspicuous spaces, in the English language, to indicate the following:


In addition, when hazardous chemicals are being handled a further notice should be displayed stating:

Local national or port regulations may require additional notices which the Master must ensure are complied with. Day and night signal for dangerous cargo as per local regulations and international code flag are to be displayed as appropriate.

Health Hazards

Most of the chemical present more than one hazard to health, for example, it may:
  • Be corrosive
  • Be poisonous
  • Produce toxic vapours
  • Pose an asphyxiation hazard
  • Result in long term damage to eyes or the nervous system
  • Have long term carcinogenic effects.

Personnel Exposure to Chemicals, Noxious Liquids and Fumes

Unplanned exposure of personnel to toxic or corrosive fumes or liquid should always be treated as an emergency and in serious cases the emergency team should be mobilised and the rescue plan put into operation.

First Aid should be administered as documented in the MSDS, however, the Master must evaluate the seriousness of the exposure and, if in doubt, seek further advice regarding treatment.

Officers must be trained in essential Firs Aid measures for the cargoes to be carried. In the event of a serious leakage resulting in large concentrations of fumes, consideration must be given to the organisation of alternative mustering points inside the accommodation in order for personnel to don the Escape Sets located at various work places and in cabins, prior to an orderly evacuation of the vessel, should this be necessary. Regular drills utilising this scenario should be practiced.

Enclosed Spaces

Enclosed spaces like ballast tanks, cofferdams etc in the cargo area may contain flammable or toxic vapours or lack sufficient oxygen and must not be entered without permission from the Master and only if proper ventilation is provided. The Master is responsible for ensuring that the proper Enclosed Space Entry procedures are understood and adhered to. A list of spaces deemed to require Enclosed Space Entry procedures is to posted up for all crew to comply and all such spaces marked.

On vessels capable of carrying toxic, flammable, or oxidising cargoes, special consideration should be given to the construction of the deck areas which may impede air flows from dissipating cargo vapours. There are many such areas on ships but commonly found in the vicinity of butterworth hatches, ullaging points and sampling points. They should be identified and risk assessments conducted to determine the appropriate risk control measures such as warning signs posted and personal gas meters to be worn.

Pollution prevention

It is the responsibility of the Master and the person he delegate to be in charge of cargo operations, including bunkers, to know the applicable international and local pollution prevention regulations and to ensure that they are not violated. Exercises should be held to train personnel in accordance with the Vessel Response Plan and/or the Shipboard Oil Pollution Emergency Response Plan. The Master should ensure that both local and international regulations pertaining to the discharge of ballast water are complied with .

Before any Tank Cleaning takes place, the pollution categories (X,Y,Z or OS) of the cargo residues in the tanks to be washed must be clearly established from one or more of the following sources: Shipping Document, IBC Code and Certificate of Fitness, If any ambiguity exists as to the Pollution Category the Master must seek advice from the Management Office prior to commencement of operations .

P & A Manual

All vessels certified to carry noxious liquid substances are required to have a Procedure and Arrangement Manual (P&A Manual) which is customised to the cargo handling and stowage systems of the individual vessel. Amongst sections concerning the vessel's equipment, arrangements, procedures and performance characteristics, the P & A manual lists those chemicals which the vessel is permitted to carry, relevant restrictions with respect to the pollution category, cargo arrangements together with arrangements for the discharge of residues and tank washing solutions to the sea and shore reception facilities.

Notification of Spillage into the Sea

Any incident, whether accidental or intentional, concerning the discharge of Noxious Liquids into the sea, whether in harbour or at sea, must be reported to the proper authorities, a list of which can be found in the SOPEP manual.

Sea valves and overboard discharge valves in pumprooms

In cargo pumprooms, particular care must be taken to ensure that no leakage of cargo takes place through overboard discharge or sea suction valves when starting or running cargo pumps. Manual valves are to be chained/locked. These valves are to be air pressure tested regularly for integrity and a log entry made. Officers should refer to the ICS/OCIMF Publication “Prevention of Spillages through Cargo Pumproom Sea Valves”.

Deck scuppers

Prior to any cargo operation taking place all deck scuppers are to be plugged and checked for tightness. Careful attention is to be given to keeping scuppers dry and clean. Mechanical type scupper closures are required to be used in USA ports and all ports.

Manifold savealls

Manifold savealls are to be provided under each manifold connection. These are to be kept clean and dry wherever possible, with any cargo spillages being drained at the earliest opportunity. Operational contamination is to be prevented by use of portable collection drums during connection/disconnection.

Following detail pages explain all liquid chemical hazards & precautionary measures while carrying at sea.

  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. .....

Following reference publications provide useful guidance and international regulations for carrying hazardous chemicals at sea.

  • SOLAS (latest consolidated edition)
  • MARPOL – 73/78 (latest consolidated edition)
  • BCH / IBC Code
  • International Safety Guide for Oil Tankers and Terminals (ISGOTT)
  • Tanker Safety Guide (Chemicals)
  • Ship to Ship Transfer Guide (Petroleum)
  • Safety in Oil Tankers
  • Safety in Chemical Tankers
  • IMDG Code
  • Supplement to IMDG Code (Including MFAG and Ems)
  • Clean Seas Guide for Oil Tankers
  • FOSFA (for Oils, Seeds and Fats)
  • Prevention of Oil Spillage through Cargo Pumproom Sea Valves
  • CHRIS Guide (USCG)
  • Chemical Data Guide for Bulk Shipment by Water (Condensed Chris)
  • MSDS for particular cargo carried
  • Chemical Tank Cleaning Guide

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