Hot Water and air (?) explosion

[robgraham]

this be a mains pressure HW tank with some sort of expansion chamber ? Sounds nasty.

Rob

[Onetap]

Maybe an expansion vessel on a hot water heating system or some part of a steam sterilisation system. The HSE will tell the media when they get around to it.

[cynic]

Many commercial heating systems operate with high temperature hot water systems in excess of atmospheric pressure and above 100 degrees C. To acommodate the expansion and contraction of the fluid within the system during heating cycles a cushion of compressed air or nitrogen is employed. This is in effect a larger version of the ubiquitous expansion vessel found in domestic sealed systems although domestics operate below 100 deg C. To enable maintenance replacement of the diaphragm within the vessel these units often have a jointed access. Purely a guess at this stage but I would say there is a probability of the joint failing and/or the vessel rupturing, thus releasing superheated hot water which would flash immediately into steam. The system should have had safety valves for excess pressure but even at normal working pressures the danger is present. Of course "someone" with the necessary skills and knowledge should have been overseeing the system but those of us who remember Flixborough know that the road to hell is paved with good intentions.