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What is putrefaction process of liquid chemicals while transporting at sea ?

Most animal and vegetable oils undergo decomposition over time, a natural process known as putrefaction (going off), that generates obnoxious and toxic vapours and depletes the oxygen in the tank. Tanks that have contained such products must be carefully ventilated and the atmosphere tested prior to tank entry .

It must not be assumed that all vapours produced by cargoes liable to putrefaction will in fact be due to putrefaction; some may not be obvious, either through smell or appearance of the cargo. Carbon monoxide (CO), for instance, is colourless and odourless and can be produced when a vegetable or animal oil is overheated.


Coconut and vegetable oils hazards

In addition to putrefaction, the above types of oil can have hazards associated with the production of Carbon Monoxide (CO). These dangers are heightened during heating and the final stages of discharge when CO levels have been known to reach in excess of 3,000ppm. As a result, it is essential that before entering a tank for either “squeezing” the last remaining cargo or for tank cleaning that the following precautions are taken.

The atmosphere of the tanks is to be monitored regularly throughout discharge for the presence of CO. Temperatures should also be taken as excessive temperatures will assist in the production of CO. The eight-hour safe exposure limit for CO is given as 25ppm. Accordingly, a detector, capable of measuring these limits, must be available on board. Full enclosed space entry procedures as detailed in the SEM must also be followed with additional checks made for CO. Failure to follow these precautions can result in fatalities.








Related Info

Carriage of inhibited flammable chemical products in cargo tanks
In certain conditions of heat, pressure and in the presence of Oxygen, some chemical cargo types can become viscous and possibly solid and dense in nature. This self reaction can cause some cargoes , especially in the presence of high temperatures and Oxygen, to begin an exothermic reaction, becoming self heating and rapidly expanding which may result in possibly disastrous consequences for the vessel.

Cargo sampling safety precautions
Cargo samples are evidence of the condition of the product during the various phases of transport (storage at terminal, arriving on board, loading, passage, discharging). This procedure describes sample-taking procedures and the legal background. Suitable PPE is to be worn when taking samples. Sample bottle to be flushed prior collecting sample. .....

Cargo segregation requirement for chemical tankers
In the case of two or more liquid chemical cargoes which react with one another in a hazardous manner, segregation must be done The product data sheets, together with the BCH/IBC Codes are to be studies carefully to determine the compatibility restrictions when carrying different groups of cargoes.

How to avoid solidification in cargo tanks ?
Solidification in the cargo tanks can occur when solidifying cargoes are stowed adjacent to “cold cargoes” or cold ballast water in adjacent spaces.

Cargo compatibility and reactivity of various chemical cargo
Transporting of dangerous and noxious liquid chemicals in bulk involved various risk factors. Between some chemicals violent reactions may occur if the chemicals are mixed in certain proportions. The result may possibly be an eruption and tank rupture. Such an occurrance must be prevented. Water may also have to be considered in this respect.

Determining presence of contaminants in chemical cargo
To maintain product quality onboard modern chemical tankers any contaminants in the cargo need to be observed. Following guideline may be useful determining various product contaminants in noxious liquid chemicals.



How to test tank atmosphere and cargo condition

Chemical tanker familiarization training for newly joined crew member

Pumps operation parameters - risk of cargo pump overload or underload

Risk & hazards of chemical contamination onboard

Cargo hoses handling ,connection and use

Control & operation of centrifugal pumps

How to test a tank environment prior entry ?

How to determine the level of a liquid in a chemical tank



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