Isolation Flange Kits for Propane/Butane Buried Tanks

[macor]

Hello folks,

Recent Cathodic Protection survey of buried propane and butane tanks indicated that they are underprotection.
After investigation, the CP technicians think that low protection is due to huge current leakage much higher than the design calculation. They recommended to install isolation flange kits to all external pipes connected to the tanks which will prevent leakage and improve CP protection level of the tanks.
I would like to ask you experts in CP, is it acceptable to install the isolating flange kit or not as the fluid inside the tanks is explosive and I found in some NACE books that:
Under no circumstances should an isolating device be installed where an explosive or combustible environment is present.
​
Your advice and explanation of the subject is highly appreciated.

Cheers.

 

[EdStainless]

I believe that the warning has to do with the possibility of a potential difference and hence a risk of spark across the isolation. Think a lightning strike.
I have seen isolation kits that have a kit to tie the two sides together electrically, but with some circuitry to limit the current draw. These are usually a combination of diodes and MOVs.
Do some more research.

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P.E. Metallurgy, Plymouth Tube

 

[brimmer]

Where an explosive or combustible environment is present.... which in your case is only possible if you loose containment / have a leak in the tank. Isolating kits are used on HVP pipelines all the time. Yes, think spark across the isolation, igniting vapor, like if you were in a closed environment.

 

[Ehzin]

As a side note, if arc prevention happens to be required to cover the occurrence of minor flange leaks or due to an ignitable atmosphere from other sources, I believe there are methods to isolate cathodic protection while preventing arcing. Look into SSDs or solid-state decouplers for more info but I think it may solve your CP issue without introducing a fire hazard. If you have any questions I may have a bit more feedback.