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Exposure to liquefied gas cargo and countermeasures
During cargo operations, the number of personnel allowed on deck forward of the accommodation
must be kept to the minimum. Under normal circumstances they are to be restricted to those persons
directly concerned with the loading/discharging operation.
During all cargo and gas freeing operations the Master is to consider the risk to personnel on deck
encountering a concentration of cargo vapour. If the cargo is particularly hazardous, he is to ensure
that personnel working on deck carry the Emergency Life Support Apparatus.
In vessels carrying Vinyl Chloride Monomer or Propylene Oxide where there is a possibility of vapour of
liquid escaping, all operations such as hose disconnection and cargo sampling will be carried out or
supervised by personnel wearing full CABA and totally enclosed protective clothing.
Action in the Event of Exposure
The action to be taken will depend on whether exposure has resulted in:
a) liquid in the eye
b) liquid on the skin
c) vapour being inhaled
Action in each case is similar for many types of cargo carried in LPG ships, but chemical data sheets
(MSDS’s) must be checked before handling begins.
Decontamination centres and eye wash facilities are provided to assist persons who have been
contaminated by cargo.
a) If liquid has entered the eye, it must be flooded gently with clean water for at least 15 minutes
(30 minutes for ammonia). It will probably be necessary to force the eye open.
b) Skin contact with liquid from most hydrocarbon cargoes will produce immediate FROSTBITE
and remedial action must be rapid and well practised, since medical assistance may not be readily
available. Contaminated clothing must be swiftly removed and the affected area immersed in water.
c) Where vapour inhalation occurs, the victim must be removed upwind to fresh air. If breathing
has stopped mouth-to-mouth resuscitation must be started at once, pending arrival of the 'Resusepac',
if available.
Immediate medical advice and assistance should be sought in all cases of exposure to gas cargoes.
VINYL CHLORIDE MONOMER
Vinyl Chloride Monomer (V.C.M.) is carried as a liquid in certain LPG ships, which have been converted
or built for the purpose.
V.C.M. is a chlorinated hydrocarbon and has flammability limit of 4 – 33% by volume and toxicity
characteristics similar to many cargoes of hydrocarbon origin. In addition, however, long-term
exposure to high concentrations has been linked with a rare form of cancer, the TLV has
therefore been set at 10 ppm – a level well below the bottom of the flammable range. V.C.M. has an
odour threshold of 2000 ppm and therefore smell cannot be relied upon as a means of detection.
It should be noted however, that to date, no cases have been recorded relating to exposure to the
monomer. The only cases have been linked with production processes, and in particular to cleaning of
the autoclaves used in the production of PVC.
Nevertheless, it is policy that exposure levels should not exceed 10 ppm unless suitable protection such
as CABA, ELSA and possible chemical suits are used.
Ships, which are in the VCM trade for all or part of the time, have specialised detection and protective
equipment. In addition, modified emergency procedures have been developed to deal with the
problems, which may arise from the presence of PVC.
Nevertheless, it is policy that exposure levels should not exceed 10 ppm unless suitable protection such
as CABA, ELSA and possible chemical suits are used.
Ships, which are in the VCM trader for all or part of the time, have specialised detection and protective
equipment. In addition, modified emergency procedures have been developed to deal with the
problems, which may arise from the presence of the gas.
PROPYLENE OXIDE
Propylene Oxide (PO) is an eserine with wide flammable limits of 2.8 – 37% by volume. The TLV of this
product is 100 ppm whilst its odour threshold is 10 ppm. Exposure to the liquid or high concentrations
of the vapour can lead to eye burns, skin irritation and blistering, vomiting, lack of co-ordination and
depression.
Air Supply/Air Conditioning
When certain toxic cargoes such as chlorine are carried, the IMO IGC Code requires that a space within
the accommodation is designated as a safe haven or citadel. This maybe the bridge or cargo control
room and is required to accommodate the entire ship’s company and provide an uncontaminated
supply of air for a period of not less than four hours.
Easy access is to be made available from the
open deck and the accommodation via an airlock which has a decontamination shower fitted close by.
It should be noted that when the accommodation air supply/conditioner is on 100% recirculation a
partial vacuum exists. It is important therefore that the double doors to the accommodation are kept
shut in order to avoid gas entering the accommodation.
Related Information:
- The risk of laden voyage
- Safety checklist for gas carrier
- Precautions against sources of ignition
- Matters That Require Attention to Onboard Work
- Maintaining stability by ballasting/ de-ballasting tanks
- Statistic electricity precautions for liquefied gas carriers
Mooring requirements for gas carrier
Means of access to ship - gas carrier guideline
Standards for use of Mobile-phone in gas carrier
Dispersal of Vented Cargo Vapours
Openings in Deckhouses and Superstructures
Engine and Boiler Room Precautions
Cargo Machinery Room Precautions
Ship’s Readiness to Move
Lashing of Movable Articles
Details of various cargo handling equipment onboard
Liquefied gases - Health hazards
Safety equipment
Liquefied gas cargo reactivity
Liquefied gas cargo corrosion
Liquefied gas cargo vapour characteristics
Liquefied gas cargo - low temperature effects
Liquefied gas carrier -monitoring cargo pressure
External links :
-
Types of liquefied gas carriers downloadable product
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