The incident in question saw three people injured following the release of steam from a non-nuclear heating system. The Office for Nuclear Regulation (ONR) is in the process of investigating the incident, but early reports suggest that there was a failure in the pressure boundary of the steam system, potentially caused by a water hammer event.
Sometimes referred to as ‘Condensate Induced Water Hammer’, the water hammer is a known vulnerability in steam systems. It most commonly occurs when steam is introduced into cold pipework that has not been sufficiently drained. As the steam cools, it turns into condensate which takes up less volume in the pipework than the steam. This produces a vacuum or pocket into which the water rapidly flows, creating an impact against the pipework.
Safety notice
The safety notice aimed at operators of major pressure systems involving steam, including:
The HSE is reminding all duty holders of this phenomenon in steam systems and advising them to ensure suitable measures are taken to prevent the occurrence of such events, including the appropriate operation and maintenance of such systems on their sites.
HSE recommend that the five-point action plan detailed in the Safety Assessment Federation (SAFed) factsheet; ‘potential hazards created by water hammer in steam systems‘ is considered.
This includes taking into account the following:
