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Personal safety for working in cargo tanks - Chemical tankers guideline

Entry of personnel into cargo tanks

On chemical tankers entry of personnel into cargo tanks is a more common practice than it is on oil tankers. Chemical tanker operators' instructions often make special allowance for this when describing procedures for entry into cargo tanks. The intention is to avoid causing a comparatively routine event to distract everyone's attention, but equally to ensure that adequate checks are conscientiously made and recorded. It is essential that procedures remain sufficiently stringent to ensure the safety of personnel, but are not so disruptive that busy personnel who are familiar with the work become inclined to disregard them.

Operators may therefore find it expedient to issue additional instructions that achieve those twin aims with regard to cargo tank entry during cargo operations, but insist on a more particular procedure at other times and for unusual entry into other enclosed spaces. It is also essential that the ship's safety management system is robust enough to make certain that instructions are followed.

A system should be in place to indicate which cargo tanks are safe for entry by marking (or tagging) of appropriate tank entry hatches. The marking should be unambiguous, and procedures should be such that absence of the mark will forbid entry.

Restricting the issue of entry permits, such that all cargo tanks which are safe to enter are shown on one entry permit, may be found to simplify the paper administration, avoid overlapping permits and the possibility of confusion as to which permit applies to which tank. If such a system is used there must be rigorous control to ensure cancellation of existing permits, and that the atmospheres of all named tanks are correctly tested at the time of issue so that an effective extension of a period of validity does not occur by default. It will be particularly important that it is supplemented by marking of tank lids with notices indicating which tanks are safe to enter.

Inspection of cargo tanks after cleaning and before loading can require an independent surveyor to enter the tank. All relevant tank entry procedures must be observed .

chemical suit
Fig: Chemical suit

Entry into enclosed spaces separate from the cargo system

On chemical tankers, entry into enclosed spaces separate from the cargo system should be treated with the same extreme caution as on all other ship types, and familiarity with practice in cargo tanks should not be allowed to induce any sense of complacency.

In particular, it is recommended that a permit to enter is always restricted to a single compartment. Preparations for entry should be positively attended to, and pre-positioning of rescue apparatus near the entry point is recommended. No cofferdam, ballast tank, peak tank, fuel or lubricating oil tank, fresh water tank, duct keel not continuously open to a pumproom, void space, access trunk, or any other enclosed space should be entered unless all the precautions are strictly observed.

The principal danger in such spaces is that rusting has depleted the oxygen content of the atmosphere to the point where it cannot support life. However, it is also possible for cargo vapour or inert gas to leak into such spaces and the atmosphere should therefore be checked for both oxygen content and cargo vapour before entry. The IBC Code requires a capability to ventilate all such spaces where cargo or cargo vapour may accumulate.

Work in cargo tanks and other enclosed spaces

While personnel are inside the space, ventilation should be continued and the atmosphere monitored at regular intervals. If personnel begin to feel dizzy or unwell they should leave the space at once.

Frequent atmosphere tests should be made, appropriate to the work in hand or to any change in conditions. In particular, tests should be made before each daily resumption of work. Tests should be so arranged that readings representative of the condition of the entire space are obtained.

It is a normal practice in some trades for personnel to be sent into a cargo tank being drained of animal and vegetable oils or fats, in order to sweep the final traces towards the pump suction. Familiarity with the practice should not obscure the potential dangers of cargo generated vapours or an oxygen deficient atmosphere. Use of a personal alarm should be considered.

Even after a cargo tank has been cleaned, there will always be a possibility of some cargo remaining, which could be a source of further flammable or toxic gas. Special care must therefore be taken whenever a pipeline or equipment in a tank is opened up, and additional tests should be made. If liquid or vapour escapes, the tank should be evacuated and not re-entered until the entire atmosphere has again been found to be safe. When removing sludge, scale or sediment from an enclosed space, periodic gas tests should be undertaken, and continuous ventilation should be maintained throughout the period the space is occupied.

Whenever cargo pumps, pipelines or valves are to be opened, they should first be cleaned and gas freed. Many chemical tankers have individual cargo pumps and pipelines dedicated to each cargo tank. However, ships with fixed cargo lines that are common to several cargo tanks should take further precautions~ to isolate the tank where the work is being done. To avoid inadvertent operation, valves on all pipelines serving the space should be secured.

Hot work in an enclosed space should only be carried out when all applicable regulations and safety requirements have been met and a hot work permit has been issued .

Related info:

Preparations prior allowing personnel into cargo tanks / enclosed spaces

How to rescue injured or unconscious person from enclosed spaces

Tank explosion case study

Pre-cleaning /washing of cargo tanks

Final cleaning of cargo tanks prior loading

Tank cleaning and posoning hazards

Testing of tanks and cargoes

Practical tank cleaning methods for various noxious liquid cargo

Special tank cleaning method

Determining proper tank cleaning by acid wash method

Supervision of all tank cleaning and gas freeing operations

Disposal of tank washings, slops and dirty ballast - safe method

Reference publications

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