Coffee Machine Boiler Explosion

In 2010 a coffee machine ruptured in a supermarket in Hampshire. Luckily nobody was killed, but the picture above does certainly  indicate the level of forces involved and the possible results of safety mechanisms failing to operate.

There is an excellent discussion on the potential legal pitfalls of operating a coffee machine in the following document.  It discusses who you should employ to test the safety systems on your machine and where the liabilities lie.

Coffee machines should be provided with two safety systems to protect from boiler explosion, in case the normal control system fails.

For a coffee machine with a heat exchanger, the the pressurstat controls the operation of the heater.  Should this fail (contacts welded closed, diaphragm split) then the element will remain powered.  This fault is protected against by a non-self-resetting thermostat (ie you have to take the cover coffee machine and press a button to reset it) and a separate safety valve to release excess pressure to prevent the boiler rupturing.

Alternatively, two separate safety valves may be used as in the Azkoyen Bravo for example (below).


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3 Responses to Coffee Machine Boiler Explosion

  1. Gene Price says:

    Hello Steve,
    I think I have a faulty pressurestat. When I turn on my Gaggia TS, it heats up fine and builds pressure, but when it reaches 1.2 bar, it does not stop as it used to. It continues to build until the thermostat circuit breaker pops. I then have to release pressure (with the steam wand) and get it back down to 1.5 bar or so, and open the top of the machine and reset the circuit breaker. I can regulate pressure by periodically releasing steam from the wand, but I do not think this is safe, and it is a lot of trouble. I am assuming that I need to replace the pressurestat, but I thought I would send a query before undertaking that job to see if there are other possibilities that I can and should check first.

    • admin says:


      Yes it definitely sounds like the Pressostat. I would not continue using it until you have replaced it.


  2. Gene Price says:

    Understood. Any tricks to replacing the pressurestat, or is it pretty straightforward? I replaced my controller, and your instructions were very helpful.


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