Expansion vessel failure is very common . The expansion vessel consists of a metal tank inside which there is an elastic rubber membrane that separates air (or another inert gas) from the water in the installation.

This elastic membrane has to be expanding and contracting all the time. Every time the heating is turned on, the glass must absorb the expansion. That is why it is a replacement subject to a lot of fatigue.

It is possible that there is a specific increase in pressure in the circuit that would cause the membrane of the expansion vessel to rupture, but if it were not very weak, before rupture, the safety valve “should” jump.

The failure of the expansion vessel should be the constant evacuation of water through the installation's safety valve. In installations with a wall-mounted boiler, the safety valve is routed with a transparent tube under the boiler itself. In diesel or aerothermal installations, the safety valve should be close to the vessel itself.