Curing Water Hammer in Two-Pipe Steam Heating Systems

A steam heating system combines a steam boiler with a distribution system consisting or pipes, valves, and radiators. Steam heating requires more maintenance than hydronic or warm air because of the make-up water flowing into the boiler. Often the boiler water needs water treatment to keep it clean enough to make good steam.

What is water hammer?

Water hammer is often the first sign that a two-pipe steam system has problems. Water hammer occurs when steam drives condensing water into joints or valves. Water hammer makes noise and damages traps and valves.

Water hammer has a number of causes including the following.

  • Excessive condensate due to un-insulated steam pipes, foaming boiler water, or other causes.
  • Water traps like sagging pipes, incorrectly pitched radiators, un-reamed pipes, and poorly designed fittings, such as concentric reducers. All return pipes should slope 1 inch in 20 feet in the direction of condensate flow.
  • Steam leaks through failed steam traps into condensate-return pipes.
  • Incorrect near-boiler piping or inadequate height between the water line and lowest steam-carrying pipe.
  • Boiler is too large for radiation so it makes too much steam and too much condensate.

Steps to reduce water hammer

The solutions to water hammer usually involve improving steam quality, replacing steam traps, insulating pipes, and eliminating low spots in piping. Steam boilers and return piping can become quite dirty over the years. A technician can add soapy water to the boiler while drawing boiler water from various boiler fittings to clean a boiler and its piping. After cleaning, the boiler should make better steam.

All two-pipe radiators should have either steam traps on their discharge or radiator orifices on their supply to prevent steam from finding condensate. Insulate all steam mains with fiberglass pipe insulation to prevent steam from condensing before it arrives at the radiator.

 

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