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Water hammer

Water hammer occurs when steam is admitted into a cold pipeline. The steam condenses 
producing both water, and a vacuum (when the water seals the pipeline from the steam 
supply). This vacuum causes the water plug to be drawn into the closed end of the pipe with  increasing velocity producing high impact forces on the pipework. This impact force can be  high enough to rupture the pipeline.

Water hammer is avoided by slowly admitting the steam into the cold line, and 
draining/venting the cold line to minimise the vacuum forming, and assist in draining the 
Testing of the boiler water is important to determine that the level of chlorides is within acceptable limits (below 200 ppm) to prevent hard scale 
and pitting   the reserve of boiler chemicals within the boiler water is accepted (P Alk above 100 ppm,  and Phosphate above 20ppm) 

Treatment of the boiler water with chemicals will ensure 
Alkalinity reserve against boiler water space corrosion 
Scale build-up is minimised 
Enough coagulant levels exist to minimise sludge build-up within the boiler 
The strength of the boiler drum is maintained
Boiler problems would be minimised by: 
Reducing the steam load and demand on the aux. boiler to reduce firing temperatures 
Ensuring hotwell feed temperatures are at the recommended 95o C to minimise oxygen 
levels in the feed 
Minimise blowdown of boiler water, whilst ensuring chloride level is not excessive, to 
avoid loss of the boiler chemicals


  1. Any piping system that uses valves to regulate the flow of liquids or steam is susceptible to the phenomena known as "water hammer." When a fluid in motion is forced to abruptly change direction or halt, a pressure surge or high-pressure shockwave results, which travels through the pipe system and causes water hammer.


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