Min. Tank Thickness of Pad Mounted Transformer
Min. Tank Thickness of Pad Mounted Transformer
(OP)
Does any IEEE/ANSI transformer standard state the minimum thickness of a pad mounted transformer tank? Or is any thickness acceptable AS LONG AS the transformer tank meets the pressure withstand requirements?






RE: Min. Tank Thickness of Pad Mounted Transformer
I would **guess** that the pressure (and vacuum) withstand requirements govern the tank thickness.
RE: Min. Tank Thickness of Pad Mounted Transformer
RE: Min. Tank Thickness of Pad Mounted Transformer
There is no direct stipulation of tank thickness we come across.
The view may be to better leave it to the transformer designer taking in to account the transformer dimensions etc. in addition to the vacuum and pressure withstand requirements and I agree with it.
RE: Min. Tank Thickness of Pad Mounted Transformer
A TOC for the probable standards is http://sta
§7.6 Tanks is probably more of a performance-based description [like pressure/vacuum capability] so may be disappointing for specific material thickness.
RE: Min. Tank Thickness of Pad Mounted Transformer
There are several sections of the ASME Code for pressure vessels. These cover different size and pressure ratings. There is a special section for vessels that are subject to external pressure such as vacuum tanks and the tubes in fire tube boilers.
Padmount transformers operate at theoretically low pressures just as long as deliberate overloading is reasonable.
One thing that I have never seen in a padmount transformer is an automatic pressure relief valve but next time I see one open I will look for one.
RE: Min. Tank Thickness of Pad Mounted Transformer
Virtually all transformers have a pressure relief device or PRD fitted. In Europe they are known aften referred to by the brand name 'Qualitrol'. They are normally set to lift at a few PSI above ambient pressure.
The size of the transformer would appear to govern the tank wall thickness: most tanks are slab-sided square designs, not really ideal from the perspective of pressure vessel design. The larger the tank, the thicker it has to be to avoid implosion under vacuum.
An aside on PRDs:
When one of these devices operates, oil is ejected and breaks up into fairly fine droplets. Has anyone ever considered whether this poses a fire or explosion hazard in the presence of an arcing fault? Transformer oil isn't especially flammable as a bulk liquid, but from first-hand experience it burns vigorously when atomised.
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If we learn from our mistakes,
I'm getting a great education!
RE: Min. Tank Thickness of Pad Mounted Transformer
Tank rupture without burning oil can still make a mess.
RE: Min. Tank Thickness of Pad Mounted Transformer
NTPC the largest utility in India specify diversion of oil spill from PRD to the Transformer oil pit below using large dia pipe. This has come from their own experience with a burning transformer in 1980s.
RE: Min. Tank Thickness of Pad Mounted Transformer
RE: Min. Tank Thickness of Pad Mounted Transformer
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RE: Min. Tank Thickness of Pad Mounted Transformer
RE: Min. Tank Thickness of Pad Mounted Transformer
Thanks for that info - someone else has obviously decided that PRD operation poses a threat.
Our site suffered a massive transformer explosion which released several tonnes of oil in the form of mist, vented through the PRDs of the tapchanger and main tank and through the gaping hole created when the 1½" top plate buckled upward over 6" and the end wall deformed a similar distance. The fireball was terrifying even from the other side of plant.
jghrist,
That is an interesting idea, although it probably applies more to welded tanks than those with bolted lids. The transformer in the event noted above burst the bolted seam like tearing cotton, firing M24 bolts like mortar bombs over a significant area. A welded tank might have faired better (or maybe not?).
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If we learn from our mistakes,
I'm getting a great education!
RE: Min. Tank Thickness of Pad Mounted Transformer
jnims, unfortunately I received the image "without caption," so I don't know its story.
RE: Min. Tank Thickness of Pad Mounted Transformer
Like this? http://www.cooperpower.com/FR3/Tranvid.mpeg
RE: Min. Tank Thickness of Pad Mounted Transformer
Steve, you know that is a proven flying-saucer crash event near Drain, OR. The Blue Book boys continue to vehemently deny it.
RE: Min. Tank Thickness of Pad Mounted Transformer
Did anyone notice how the water from the deluge flashed into steam when it touched the hot oil, causing the oil to explode with even more aggression?
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If we learn from our mistakes,
I'm getting a great education!
RE: Min. Tank Thickness of Pad Mounted Transformer
RE: Min. Tank Thickness of Pad Mounted Transformer
In Massachusetts, New Jersey, and the other states that require ASME pressure vessels the requirement applies to forced hot water and low pressure steam systems that use a 15 psi relief valve.
If you want to get insurance then in almost ALL cases you do need an ASME inspected and stamped pressure vessel particularly if your transformer is located indoors or crammed between two buildings.
I will download the mpeg file later.
RE: Min. Tank Thickness of Pad Mounted Transformer
I guess you mean High velosity water sparay system (HVWS) used for fire protection of transformer installations. These include deluge valve, temperature sensors and nozzles.
The nozzles cover the transformer completely (from all sides as well as top) and are laid out in such a way that the fine water sprays forms a blanket over the transformer with burning oil thus cutting off the oxygen supply as well as cooling the transfomer.
The fine spray when it comes in to contact with oil is supposed to form emulsion ("Emulsifier systems" is another name for the HVWS spray systems).
I have not heard of explosion due to water deluge coming in contact with burning oil and I don't think there is any such possibility in a well engineered HVWS fire protection system.
Do you have more info!