Vessel grounding

[DHoffpauir]

Is there a standard that discusses vessel or tank grounding in industrial plants? I am aware that the NEC requires a 25 ohm or less ground path to the grounding electrod. I am trying to convince our MI group that what we have designed is sufficient

 

[rbulsara]

NEC or not, all vessles and tanks (non current carrying) parts should be firmly bonded to the building steel which is turn is inherently grounded. Also bond all vessles and non current carrying metal componnets together.

This is to create a equipotential field to avoid shock hazard, ground for saftey and minimize risk of fire or shock by electrostatic discharge.

I do not think seprate ground rop to individual equipment is the answer, unless this a lone equipment in a remote place.

 

[jbartos]

Suggestion: Minimally, the tank resistance should be low enough to trip the electrical protective devices associated with the tank.

 

[DHoffpauir]

Thanks for the input. I have been researching the web on this subject and I have come across a few standards that are interesting and give reference to tank and vessel bonding and grounding.

NFPA 77 - Static Electricity
NFPA 780 - Lighting
API 2033

 

[DHoffpauir]

Try API 2003 instead.

 

[peebee]

Static charges are usually not the concern here -- static dissipation will occur even with very high ground resistances (megohm range).

Fault current (and sometimes lightning) is usually the main concern, if there's electrical devices on board. Assuming your ground is sized per NEC or local code, you're probably OK. For lightning, check NFPA 780.

Ground straps to building steel or similar are often provided for tanks for additional safety or to ensure static dissipation. #8 copper is often specified, due more to mechanical strength properties than electrical properties. Bigger conductors might be selected in accordance with NEC 250.122 if large electrical devices are mounted to the vessel.

 

[peebee]

Also, check out the IEEE Green Book for LOTS of information on grounding.

 

[busbar]

Although not a chiseled-in-stone ANSI standard or “Code,” chapters 10 and 16 of IAEI/Soares’ Book on Grounding partly deal with non-electrical-equipment grounding and are worth close review.

It pays to be careful that cathodic-protection components are not installed in such a way the metallic-vessel connection to grounding electrode(s) is compromised.