TR fire wall forces?

[WWTEng]

Do you consider and blast loads in the design of a fire wall for a transformer?

 

[ScottyUK]

Depends if the wall is for fire segregation or blast protection. I've seen both types - sometimes the choice between fire wall and blast wall is an economic decision based upon factors such as the criticality or capital value of the transformers involved, for example.

 

[Parchie]

Let me add, I haven't seen a transformer break its can when exploding! The last time I remembered, the bolted top plate, housing the HV bushings and the pressure relief device flew off, leaving the secondary porcelain terminals and the damaged core/windings behind. Why does making the walls blast-resistant important?

 

[Power0020]

I am not familiar with the term "blast" wall for transformers as what I have seen before for most of utilities is a "fire" wall. Requirements for that usually comes with oil containment and fire protection (e.g. NFPA 850).

Just to mention, I found somewhere that the TR firewall shall withstand two .44 magnum projectiles....see the link:

http://kafactor.com/content/technic...cal-transformer-fire-explosion-protection.pdf

 

[prc]

In my opinion, the comments in the link article are highly exaggerated. The only item that may blast and damage the nearby transformer is porcelain insulator. I have not seen metal pieces or tank parts flying around during transformer fires or blasts. Today the trend is to go for dry type bushings with silicon rubber housing(RIP- resin impregnated condenser bushing)so that a bushing failure will not cause porcelain blast and initiate a fire. Major transmission utility in India is specifying such RIP bushings up to 1200 kV level in their transformers. Even with porcelain insulator shrapnel, a normal fire wall will dampen the forces so much that the piercing out pieces cannot damage nearby transformer. So a fire wall is sufficient and blast resistant wall may be superfluous.

 

[WWTEng]

Thank you all for the input. I have always thought of these walls as fire walls and not blast walls. In the past I have desgined them for conservative wind load. And to me, these walls should be deemed sacrificial with a good chance that the wall may have to be re-built in case of a large fire.

 

[ausphil]

Does anyone else see the irony of the 4.5kg fire extinguisher in the photo on page 6 of Power0020's attachment?

Ausphil

 

[Parchie]

What's ironic there, if I may ask?
Fire fighters sometimes fail to bring back all their fire fighting appliances after overhauling a fire area!

 

[Power0020]

Good point Ausphil, maybe they carried it as a precaution during investigation after the big fire is over.