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  1. #1
    Forum Member
    Join Date
    May 2008
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    Default VCM foam protection

    VCM is not only highly flammable but also a carcinogen. It is stored in a double walled tank that has a capacity of nearly 20000 lbs. Being a gas it is stored as a liquid at -14°C( boiling point at atm pressure). This storage has a dyke wall and also deluge system on the tank.
    Another double walled tank for liquid ethylene of capacity 30000 cubic metres capacity at
    -101.3°C(boiling point of ethylene at atm pressure) is having deluge on the tank wall and also 8 foam generators to the dyke wall.

    I was wondering about this configuration. I asked the safety person and his reply is as follows for the non existance of foam to the VCM dyke:
    It is a double walled tank and there is no need of foam.
    If foam is applied as it is hotter than the liquid VCM it will facilitate vaporisation.

    I am not greatly convinced with this reply so I posted this query.


    I had posted this in the fire fighters forum erroneously

    Vinay


  2. #2
    MembersZone Subscriber
    Join Date
    Dec 2008
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    Great State of Texas
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    120

    Default

    Vinyl chloride monomer or VCM is some seriously nasty stuff. It's actually made by cracking ethylene with chlorine (simplified statement of course). Foam doesn't work all that great and if any is applied, it needs to be alcohol resistant and will only work on small spills.

    Chances are, it'll phase to vapour when it hit's atmosphere anyway and if you have enough of a breach to dump liquid, surround, drown and run because it will eventually find an ignition source and make some seriously bad clouds.

    If it ignites, copious amounts of water are needed and even then, it may not extinguish so letting it burn out is most likely the best option. Direct water application will also cause vapor to release quicker and would make your fire harder to contain. Indirect to cool and contain is the best method. The smoke may contain VCM, hydrogen chloride, carbon monoxide, carbon dioxide and phosgene so be ready to suppress products of combustion. Since it likes water, handle your run off and test it for LEL often.

    Ethylene, on the other hand, isn't as bad but will also vaporize quicker if water is directly applied. Foam would be more effective on Ethylene than VCM since Ethylene is not as likely to absorb it.

    So he/she is right and wrong... Direct application of water on VCM will cause it to vaporize faster and the foam won't work because VCM likes water.

    Be safe, R2

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