Transformer Blast Wall question 1

[rand1234]

Good Morning,

I had a question regarding transformer blast walls. Is is permissible to mount conduit or cable tray on the outer sides of a blast wall? And is there a certain clearance from the Iso-Phase bus duct that must be kept? I can't seem to find any standards regarding transformer blast walls (main resource: NEC 2017).

Any help would be much appreciated, thank you.

 

[BJC]

It's not so much the "blast" as the fire. Once the tank is ruptured keep the fire from spreading, control the oil.
Look up Transformer fire walls, Oil containment and control systems and deluge systems. Look at the USACE and BuREC standards.

 

[prc]

The purpose of fire wall, as I understood, is to protect nearby transformers from blasted materials to avoid spread of fire to them. So technically no issue in mounting cable trays near to wall. As regards bus duct, only mechanical clearance for maintenance needs to be considered. Height of fire wall should be same as top of conservator tank and need not be top of the EHV bushing.

 

[xnuke]

During a fire, the outer side of the wall could reach high temperatures, so anything mounted to it could be damaged. Check that the maximum allowable temperature won't be a problem.

I disagree with prc on wall height. Consult NFPA 850 (it's free to view) for recommended fire-rated wall dimensions, including height, which should extend a minimum of 1 ft above the top of the tank and conservator.

This Wikipedia article contains some of the relevant NFPA 850 information.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[prc]

Thank you Xnuke for that info !