September 5, 2019
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Following an incident which is currently under investigation by the Office for Nuclear Regulation where three people were injured following a release of steam, the HSE has issued a safety alert reminding operators of pressure systems involving steam of the phenomenon of condensate induced water hammer.

This phenomenon typically occurs when steam enters cold pipe-work, 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.

If you have such systems the HSE are recommending that you remind yourselves of the phenomenon and ensure suitable measures are taken to prevent the occurrence of such events, including the appropriate operation and maintenance of such systems on their sites. The HSE recommend duty holders consider the 5 point action plan detailed in the Safety Assessment Federation (SAFed) factsheet: FS1 “Potential hazards created by water hammer in steam systems”

This can be downloaded from SAFed’s website at under miscellaneous guidance.

The full safety alert can be found on the HSE’s website at:

Please speak to your normal PIB Risk management contact or get in touch using [email protected]  if you have any questions about safety of pressure systems.