Published on 21/08/23 829 Views

Two technicians were re-injecting sealant into a leak-sealing clamp around the 400DN 900# bonnet-to-body flange of motorised valve in the circulating water circuit of the CCR platformer steam generation system. The valve was in the open position with boiler water at 70 barg (1015 psig) and 290 ºC (554 ºF) flowing through it. The bonnet-to-body flange was a ring type joint (RTJ) and the clamp surrounding the joining was originally fitted 2 years before. Soon after the technicians started re-injecting sealant, all 20 of the 1 ½ chrome/moly steel stud bolts securing the bonnet failed catastrophically causing the bonnet-motor assembly to separate from the body with great force. The sudden release of boiler water resulted in a boiling liquid expanding vapour explosion (BLEVE). The two technicians were killed.

Ask yourself and your crew:

How can something like this happen here (e.g. on our site)?
What safety measures (i.e. procedures, controls/barriers) do we have in place to mitigate the risk?
How do we know the risk controls/barriers are working?
What improvements or changes should we make to the procedures, controls/barriers or the way we work?

Original content courtesy of IChemE Safety Centre