The Complete Steam Guide

What is Water hammer?

Steam lines are insulated mainly to reduce radiation heat loss from pipe surface and also for personal protection. However, even in a well insulated steam line, radiation losses are typically 3%. This means that about 3% of the steam quantity flowing through the pipe condenses in the steam pipe lines. This condensation starts as soon as steam exits the boiler.

Steam and condensate contained in the pipeline travel together. This is two phase flow. Steam occupies the major volume of the pipe and pulls condensate at a velocity equal to itself.

As the condensate gets pulled along with steam at a high velocity, it forms a slug. Water hammer is the phenomenon caused by this slug of condensate that strikes the pipe walls, elbows, pipeline accessories at high velocity. Repeated hammering of this slug of water results in damaged pipelines and pipeline accessories.

Effects of water hammer include

  • Severe mechanical vibrations
  • Heavy leakages from joints
  • Ruptured pipelines
  • Extensive damage to delicate internals of control valves
  • Extensive damage to heat exchangers
  • Cracks in steam trap and valve bodies
  • Valve failures

Waterhammering in the steam system should be immediately addressed to prevent

  • Serious accidents involving plant personnel
  • Damage to pipelines and pipeline accessories including traps and control valves
  • Damage to process equipment (heat exchangers)
  • Recurring failures (direct leaks, gasket ruptures, equipment coil failures, heat exchanger gasket failures and leaks, steam accessories failures) resulting in costly shutdowns and repeated maintenance
  • Excess energy consumption due to higher incidence of leakage losses in the system

Steam carries condensate which is heavy component at velocity equal to its own velocity i.e. 25 M/s (Remember it is equal to 90 Km/hr if expressed in a speed unit we are familiar with- thus, condensate travels at a speed of a really fast car through the pipelines with steam).

Condensate with 160 times the mass density travelling at 10 times its normal velocity will exert 1600 times greater impact! That is Water Hammer!
Thus, water hammer needs to be contained.