We attempted six time to get the machine to blow. The shed was used to illustrate what might happen to a coffee service area in the case of a machine failure like this.
Things we disabled were. The pressure switch, boiler safety valve, hot water valve and the steam valves. We had to reinforce the element flange as this bent away from the boiler flange at about 15.0bar. All the above leaked as the pressure got higher. The weakest point was the boiler to element seal. The steam valves and hot water valves were forced open by the pressure at 16.0 bar.
Normal safety valve is set at 1.9bar. Boiler is 14.0 liter filled with water to about 65% for this test. The tank exploded at about 21.5bar 218.0 degrees Celsius.
Element fitted was 2850W - it took about 40 minutes from cold to blow the machine at the last attempt.
One thing we did learn was that the machines are built with safety in mind, a lot has to go wrong for them to fail. Please note that different machines might behave differently to this type of test.
