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Carriage of Hydrolysable Cargoes

The transportation of chemicals is technically and logistically different from the transportation of oil and oil products. Chemical tankers are more advanced in many ways. The cargoes may be hazardous and noxious chemicals or such products as edible oils and fats. A common characteristic of these cargoes is that they tend to be high value and require sophisticated handling for safety, health and loss prevention reasons.

Understanding the chemistry behind the carriage of various chemicals is an integral part of Chemical Tanker operations. Cargoes which react with water to form acidic compounds are called hydrolysable cargoes. Examples are Esters (Acetates and phthalates) and chlorinated or brominated materials.

Hydrolysable cargoes must be carried in perfectly dry tanks with moisture content less than 100 ppm (200 ppm for zinc). It is important to vent to eject absorbed/ adsorbed cargo in coating. This must be done prior doing tank cleaning with water. However certain viscous non-volatile products like DOP and Texanol cannot be evaporated by venting and must be cleaned off by warm water immediately after discharge. Since epoxy coating absorbs cargo like a sponge, it means that two successive cargoes are required to be compatible with each other. For example after EDC if you load a cargo containing water, Hydrochloric acid will be formed which will destroy the epoxy coating.

Carriage of Hydrolysable Cargoes formula
Fig : Carriage of Hydrolysable Cargoes chemical composition


Esters can saponify in contact with water at higher temperatures resulting in increased short chain type FFA which can be aggressive to tank coatings. After carriage of Hydrolysable cargoes such as Acetates, the tanks should be ventilated to remove all traces of cargo before any water is introduced.

Chlorinated/ Brominated solvents hydrolyse in presence of water to form Organic and Inorganic acids which damage the paint coating. Shippers must give the moisture content in PPM. Water content should not exceed 100 ppm or 0.01% especially for epoxy. Nitrogen pad is a must to exclude moisture. Chlorinated solvents hydrolyse slowly to acids. Hence it must be ensured that water tank washing is not stopped in an early stage.




Hydrolysis is an oxidation reaction between Chlorinated HC and residual water. Oxidation occurs due to exposure to radiation or the presence of certain catalysts and can be prevented by inhibitors. Hydrolysis is accelerated at higher temperatures.




Vegetable oil and Animal oils have Free Fatty Acids content (FFA). The hydrolysis of edible fats and oils is promoted by the presence of water, particularly at higher temperatures. If hot prewash is carried out, FFA will increase rapidly to a level, which will coagulate the albumen in the Vegetable/Animal oil. This damages the surface of the zinc silicate lining. The breakdown of vegetable and animal oil fats to fatty acids is promoted by the presence of water particularly at higher temperatures. Hydrolysis is also promoted by the action of certain micro-organisms.


Carriage of Hydrolysable Cargoes
Fig : Carriage of Hydrolysable Cargoes


Previous cargoes may also accelerate hydrolysis of edible fats and oils are acids and bases e.g. acetic acid, acetic anhydride, citric acid, fatty acids, phosphoric acid, sulphuric acid, and sodium hydroxide solution. The general loss of quality due to oxidation (increase in peroxide values) or hydrolysis (increase in free fatty acid [FFA] content) during a voyage can be eliminated by , nitrogen-blanketing the tank, especially if the cargo is refined oil to be used directly in the food-chain without re-refining. Hydrolysis affects the flavour (taste, odour) and acidity of the oil, producing hydrolytical rancidity.



We have summarized below some of the special chemical cargoes frequently carried onboard chemical tankers

Handling benzene & methanol safety precautions
Benzene is known as a strong carcinogen and known to cause leukaemia. When handling cargoes with more than Benzene concentration of 0.5%, the Master is to ensure that all personnel involved are aware of the long term hazards. ....

Handling carcinogens requirements for certain chemical cargoes
A carcinogen is a substance that may cause cancer by contact or by inhalation. It is therefore essential that the highest safety precautions are taken when handling these cargoes. Access to deck areas must be restricted to duty personnel only. .....

Handling ACRYLONITRILE safety precautions
ACRYLONITRILE are high value and require sophisticated handling for safety, health and loss prevention reasons. They need careful consideration prior loading , tank coating compatibility, cross compatibility with other cargoes carried, environmental controls if required (inerting). .....

handling ISOCYANATES safety precautions
Isocyanates require sophisticated handling for safety, health and loss prevention reasons. They need careful consideration prior loading , tank coating compatibility, cross compatibility with other cargoes carried, special tank cleaning procedures & environmental controls . .....

handling Sulfuric acid safety precautions
Loading , carrying at sea & discharging of Sulphuric acid involve high risk and require sophisticated handling for safety, health and loss prevention reasons. They need careful consideration prior loading , tank coating compatibility, cross compatibility with other cargoes carried, environmental controls if required (inerting). .....

handling Phenol safety precautions
Phenol are high value and require sophisticated handling for safety, health and loss prevention reasons. They need careful consideration prior loading , tank coating compatibility, cross compatibility with other cargoes carried, environmental controls if required (inerting). .....

Hazards of Phenol - safe handling of Phenol on chemical tankers.
Heating instructions of the Shipper or Owners must be followed to avoid cargo related claims. Sufficient toxic gas measuring tubes must be available before commencement of loading. .....

Marine transportation of Phenol and more safety guideline
The solution of Phenol causes severe chemical burns to the intact skin, which are usually painless. It appears as white wrinkled "dead skin". In case of eye contact, permanent damage to the eye may occur.....

Handling benzene & methanol safety precautions
Benzene is known as a strong carcinogen and known to cause leukaemia. When handling cargoes with more than Benzene concentration of 0.5%, the Master is to ensure that all personnel involved are aware of the long term hazards. .....

Requirements of various grade chemical cargo heating
In a modern chemical tanker in order to maintain product quality, to minimise the potential for discoloration, and to facilitate some liquid cargo transport in a safe manner cargo heating is required. .....

Handling toxic cargoes
There are three common ways that a cargo can be toxic: swallowed (oral toxicity), absorbed through the skin, eyes and mucous membranes (dermal toxicity) or inhalation as a vapour or mist (inhalation toxicity). ....


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

  1. Toxicology and associated hazards onboard chemical tankers
  2. Hazards of vapour given off by a flammable liquid while carrying at sea
  3. Reactivity of various noxious liquid chemicals
  4. Most corrosive chemicals carried onboard chemical tankers
  5. What is putrefaction process of liquid chemicals ?
  6. Specific gravity,Vapour pressure and boiling point,Electrostatic charging & measuring Viscosity
  7. General precautions onboard chemical tankers
  8. Mooring precautions onboard chemical tankers
  9. Berth precautions onboard chemical tankers
  10. Cold weather countermeasures, avoiding electric storms
  11. Restriction on using radio equipments and other mobile devices in cargo working areas
  12. Handling precautions for carcinogens or cyanide-like substances
  13. Means of access (gangways or accommodation ladders) safety precautions
  14. Preparations for hot work and safety precautions
  15. Precautions against static electricity





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



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