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Vacuum implosion

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It was a controlled test to monitor what happens when a vacuum is created inside a tank wagon. 

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Somehow I don't think this one I photted at Pecos, Texas in Sept 2004 was actually controlled!

 

revGATX16992PecosTexasSept2004.jpg

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Yes this sort of thing does happen although I have never seen it happen to a rail tanker before - which is not to say that it cannot happen.

 

Typically you start to pump out a tank (or rail tank wagon).  There should be a mechanism to allow gas (often nitrogen when handling flammable materials) into the tank so that the pressure remains at normal atmospheric pressure.  If that mechanism does not work (someone forgot to open a valve), and if the pump has enough umpff to keep emptying the tank then a vacuum is formed in the tank and the result is as you have seen - sudden and catastrophic implosion.

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We used to live in Penkhull, Stoke, overlooking what was then the Marcroft works. At the time (late 1970s), a large part of the work they carried out was overhauls and repairs on all sorts of tanks. Whilst we'd quite often see examples where something had hit the tank and dented it, I can only think of perhaps one example of an 'imploded' tank.

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In "Oil on the Rails" by Alan Coppin, whilst describing how the 1927 14 ton RCH spec wagon discharged via a bottom outlet stool he mentions how forgetting to open the cap could cause a partial vacuum to cause barrel plates to buckle. He was told that an unofficial repair method was to use hydraulic pressure to reflate it!

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It is quite easy to do with oil tanks. I saw one at a RAF station in Germany where the loco delivered a few tanks of oil, the storeman forgot to release the upper valve lid and gravity did the rest when the lower valve was opened. Red faces and a big bill was the order of the day.

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The same can happen wth covered hoppers the opening of the doors can cause a sudden vacuume and the lid implodes! I believe some of the GBRf biomass hoppers had a similar problem when discharged with the lid closed!

 

The HEA's when converted to CEA's had anti vacuume slots put in the ends in a similer way to the salt PGA's had a pipe added!

 

Mark Saunders

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Wasn't there a tank wagon dumped at Cadishead in the 1980s that had imploded in this way?

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I've seen it done at Aberthaw power station around the 1970s. A bogie oil tank was being emptied, and the staff didn't open the top lid before they started. It collapsed in much the same way as the one in the American picture, but no, it wasn't blown back out again!

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One used to (still can) be able to use vacuum to refill boilers of the externally fired pot variety.

 

At the end of the run blow out the fire and everything started to cool down, this created a vacuum in the boiler.  Opening the boiler level plug, and connecting it's drain pipe to a water supply, would draw water into the boiler, and re fill ready for the next jaunt around the garden, without resorting to  re filling by removing the safety valve and using an old teapot or similar.

 

Of course, if one forgot to close the regulator at the end of a run, the vacuum would be equally adept as sucking the contents of the displacement lubricator back through the regulator.  This would then coat the inside of the boiler with unused steam oil and the rather messy condensate from the bottom of the lubricator.

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Somehow I don't think this one I photted at Pecos, Texas in Sept 2004 was actually controlled!revGATX16992PecosTexasSept2004.jpg

Texas so it might just have melted a bit!

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