Water hammer

Simply install a water hammer arrestor - an air filled chamber, at the valve. Available at your local hardware store.

or change your valve to one that closes slower

Yup, both the water hammer arrestor and the slow closing valve are good ideas.

Another idea (more expensive but still valid) is to use a soft-start/stop motor drive. This thing starts or stops the pump slowly so that the pressure doesn't build up or collapse too rapidly.

We, however, use variable-frequency-drives. It allows us to control the chilled water flow as needed. It also incorporates the soft-start/stop feature.

This way, the valve is only used for isolation during maintenance.

Water hammer usually occurs due to too many bends. If you can modify the piping to reduce the no. of bends this will relieve the system.

The advantage of too many bends is to confuse and rule.

The two sides that must be connected always seem to be on opposite sides of an obstruction. Would replacing the bends with tees and crosses reduce water hammer?

Generally bends are of Radius = 1.5 x Dia of Pipe. In the above case it may solve the problem by using Long Radius Bends where Radius = 3.0 X Dia of Pipe which are available in market. Using Tees or crosses will be of no help since these also cause sudden change of direction in the momentum of water and thus create a hammering effect when a valve is closed.

Water hammer is caused by the sudden stopping of the flow of water (or fluid) due to the valve being closed too suddenly. The mass of the flowing fluid being forced to stop produces a shock wave that can burst pipes and damage other equipment that may be on the pipeline. I've also heard pipes hammer when the pump is direct-line started (ergo: water is forced to move too quickly).

Reducing the number of bends is always a good suggestion but it will not necessarily stop the hammering.

Stick a big loop or bend in the line or an accumulator to absorb the " pulse"

Frank--I investigate waterhammer accidents although I've never heard of one in a chilled water system. The # of bends in the pipe is immaterial. Can you describe where and when the hammer is happening. For example--is it when a pump starts or stops or a valve opens or closes? Does it happen at a high point in the system?

It is something I suspect, could happen on the botton of the pipe in a high rise building, the sudden shut of the valve make the dynamic pressure of the pumped water to suddenly become a static pressure and start a shock wave.

What do you think about that??

here are a couple of methods

1. cut remove the last elbow in the system insert a tee from the open end of the tee start a vertical pipe (an elbow may be necessary) but in an adapter for a larger size pipe make a vertical stand of the larger pipe approx. 18" and cap the top. when you refill the line this will create an air pocket that absorbs most of the shock. If you get hammering again after many months drain the line and start again.

2. replace the last 10 or more feet with new plastic hosing (approved in most states) this stuff needs no elbows or fitting so it is easy to install with the right crimp tool. since there are no corners and the pipe is more flexible than metal it absorbs much of the shock

Thanks a lot pals, Im gathering all valuable info and star laying out a system, Iwill let you know..

I feel the best solution is the one against comment #1 i.e. to provide an air filled chamber near the valve and thus prevent any shock from being transmitted through the piping system.