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Industrial Electrical-Containment walls around a tank

To the newsgroup:

Has anyone come across this before? At the local refinery where I do some work for they have storage tanks with containment walls just in case there is a leak out of the tank. They could be concrete or mounds of dirt and stone. These were installed long ago. In some cases they have conduits going through the sides of the containment walls for electrical power or instrument signals.They have seals on the conduits for going from one area classification to another area classification to meet the explosion proof requirements. Is there anything out there that could prevent liquid seeping through the conduits going through the containment walls in case of a tank leak? Would the explosion seals be suffient? Any feedback would be greatly appreciated.

Thanks in advance,

Dave

Reply to
DJB
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There are electrical standards that deal specifically with the electrical equipment installed in "hazardous areas" as they are called (the IEC 60xxxx series comes to mind, but I don't know what is applicable in your country.)

To answer your question, the bund wall is there to contain a spill (ie. in an emergency) and is not really designed to contain liquid all the time, so a bit of possible seepage is not usually a problem.

Any conduits going through the bund wall have to be petrochemical-resistant and liquid-tight themselves (some plastics are out) and be sealed using 'Y'-seals - tee-shaped sections of the conduit filled with an epoxy putty filler.

In my experience, electricians usually leave the epoxy out of the 'Y'-seal to make it easier to pull more cores through later on - making the installation an bit dodgy to say the least - but a good inspector should pick this up.

The problem is actually not the liquid only - it's the flammable vapours. Even with the barrier, it is possible to get vapours travelling up the interstices of the cable and causing explosions in supposedly safe areas (like switchrooms).

I hope this helps.

Cameron:-)

Reply to
Cameron Dorrough

petrochemical-resistant

Reply to
Maintech

Personally, I'm not real keen on the typical G.I.W.P./'Y'-seal system you guys use over there for just that reason. That's a job for a plumber - not an electrician! ;-)

Most (all new) installations over here (and indeed, a majority of places outside the USA) use steel-wire armoured cabling and barrier glands instead of the rigid metal conduit system you put up with.

Apart from being flexible, SWA cabling is quicker to install and can be glanded off correctly the first time around. If you need to run another cable later on, pulling the cables through open-ended HDPVC conduit, sealed each end with foam filler to keep the rats out, makes the task far easier than having to remove the epoxy putty from a 'Y'-seal to just 'cause you're short a few cores..

Not many people realise that with conduits starting in a "hazardous area", the "hazardous area" actually exists for the *full length of the conduit* - right up to the barrier - especially if the conduit is underground (and you can't see where it goes). I have seen quite a few safe-area junction boxes blow up in my time, scaring the crap out of the operators nearby... In the petrochem business, a small spark makes a big bang! :-)

Cameron:-)

Reply to
Cameron Dorrough

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