July news letter
29th July 2019
SR 2109/159
22nd August 2019

HSE issue safety notice with respect to water hammer

HSE has issued a safety notice to remind operators about condensate induced water hammer, and their responsibilities in terms of the maintenance and operation of steam systems. Three people were injured following a release of steam on a nuclear site. Investigations are ongoing, but early indications suggest a failure in the pressure boundary of the steam system, potentially caused by a water hammer event.

Water hammer is a known vulnerability in steam systems, and is sometimes referred to as ‘Condensate Induced Water Hammer’. It most commonly occurs when steam is introduced into cold pipe-work 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.

Operators should remind themselves about this phenomenon in steam systems 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. 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.