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
condensate.
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
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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