API 650/620 Tank Secondary Containment Issues

[drials2]

Guys,

I'm running into some resistance when I try to justify why I do not want electrical/process equipment inside the dike walls around tanks. We need a run down cooler to cool some condensate and
"they" want to place these coolers inside the dike. Every site I have worked this has not been done, and looking through API 650 and RP 500 I cannot seem to find a justification to prevent this. Is this practice just a good plant construction rule of thumb or is there a standard I can fall back on? Thanks for your experiences and your input.

DR
Project Manager.

 

[Duwe6]

Site NFPA - putting electrical equipment below the "high water" line* is an unacceptable risk, especially if any of the tanks may contain flammables.

*At Fukushima, the intakes for the emergency diesel generators ended up below the high water mark. Thus started the disaster.

 

[fegenbush]

Can you provide what product is in the tanks? Obviously, water tanks have different restrictions than hydrocarbon tanks.

 

[drials2]

Thanks Duwe6,

Which NFPA standard are you siting? (Also, "they" are banking on Class 1 Div 2 electrical for protectation; as a caveat).

 

[drials2]

Yes, forgive me, it is stabilized crude condensate (light petroleum liquid).

 

[fegenbush]

I believe Duwe6 is citing NFPA 30 - Flammable and Combustible Liquids Code

 

[Duwe6]

With light petroleum, NFPA-30 is exactly right. However, Div 2 may be too lenient - their items may be submerged for hours, if not days. If it was water, NEC - National Electric Code [NFPA-70] would have had to suffice [switch gear & motors under water].

 

[StoneCold]

drials2 Why not elevate the pumps and tank if it needs to be inside the diked area. Code wise I am not sure there is really a rule against it. I have process pumps inside of a methanol containment. To make that situation better we opted for vertical centrifugal pumps so the motors are above the containment, but I don't think that there was a code that said we could not have them on the ground. Just being cautious lead us to put the vertical pumps in.

Regards
StoneColdEngineer

 

[Duwe6]

". . could not have them on the ground"

API & NFPA allow placing motors 'on the ground', just not below hydrocarbon level inside a containment.

BTW, using a vertical-shaft pump and placing the motor above the top of the dike is good engineering -- I'll be stealing that idea. Thanx!