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This information was sent to us from a friend in the CFA.

The CFA were attending a call recently at Frankston they came across what is an interesting set of circumstances. In the importance of sharing knowledge and experience they have provided some photos to paint the picture (see images below – click on each image for a larger view).

In short, the explosion and damage was as a result of the pressure relief valve on the hot water service storage tank being removed and capped (done most likely as a way of not paying for leaking water form the relief valve instead of replacing it) – you can see the plug in a couple of the tank photos.

Over time and as a result of the pressure not being able to be released the consequence is evident in the other photos. The tank landed around 200 metres from its original position at the back of the house.

No injuries as a result (lucky).

Please feel free to share with others in the interest of public safety.

Hot Water Tank 1 600px Hot Water Tank 2 600px Hot Water Tank 3 600px Hot Water Tank House 1 800px

Learning Outcomes (by Mick Holton)

  • Anything that is sealed can rupture if heated sufficiently.
  • This relationship between temperature and pressure is particularly dangerous when liquids are involved (water, oil and fuels) because a liquid is virtually incompressible and the pressure will build rapidly.
  • This is made more dangerous when flammable liquids are involved (often called a BLEVE)
  • A BLEVE can occur even with non-flammables.
  • With liquids, the pressure will raise the boiling point of the liquid (like a radiator cap on a car). When the pressure vessel ruptures, the liquid will boil and expand very rapidly. That rapid expansion is what we know as an explosion. Have you ever taken the radiator cap of a car only to hear the boiling begin as the pressure is relieved? (this is a dangerous practice).
  • Some other things that can scare the crap out of firefighters as they rupture when heated are:
    • Tailshafts
    • Gas Struts
    • Tyres
    • Shock Absorbers
    • Anything that is fully welded or sealed
  • Don’t forget the classic BLEVE scenarios like LPG gas cylinders and other flammables.

Thanks to the CFA for sharing this information.

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