Water hammer

[DGrayPPD]

Trying to develop my knowledge on water hammer. Can anyone direct me to an article, book, or give just general knowledge/advice on the subject. I understand what it is. What I'm looking for is:

Ways to spot common piping layouts that are prone to water hammer

Methods used to prevent water hammer

Any examples that anyone may have of experience dealing with water hammer

Thanks for all answers. This is an area I have not dealt with often and would just like to broaden my knowledge and understanding of the subject.

 

[LittleInch]

Ways to spot common piping layouts that are prone to water hammer
Long unsupported lengths or with ability to move sideways or vertical and hit other things


Methods used to prevent water hammer
Prevent movement of pipe and reduce support spacing
Deal with the event causing surge in the first place - reduce valve closure speed, reduce velocity to below 3m/sec, install surge arrestors / relief valves / accumulators.
Sometime you need to close valve to 70-80% then last bit slower.
Flowing to more than one location at the same time.



Any examples that anyone may have of experience dealing with water hammer
normally try and reduce at source

There are lots of resources out there on this subject.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[PEDARRIN2]

Do a "word" search on this site.

This has been discussed a lot.

Valmatic, AWWA, ASCE, have some good information.

Do a google search for "water hammer" "surge protection" and other similar words. There is a lot out there.

 

[BigInch]

High velocities (over 10fps) tend to produce water hammer as do 1/4 turn ball valves.
Small pipe diameter is a typical indicator, as it tends to have those higher velocities.


Reaction to change doesn't stop it

 

[DGrayPPD]

Are there check valves that are better designed for water hammer than others? For instance in a pump discharge you'd want a rapid closing check valve like a swing but could this also be the source of the water hammer?

 

[BigInch]

A check valve is not a source of water hammer. The reason why the flow reversed and the check valve closed might be.

Reaction to change doesn't stop it

 

[LittleInch]

This article isn't bad

http://www.fluidmechanics.co.uk/hydraulic-calculations/water-hammer-2/

and also search joukowsky equation.

The check valve thing is interesting.

Surge or water hammer is a pressure pulse caused by the initiation of the valve closure.

It travels at the speed of sound in the fluid - which can vary, but is normally several hundred m/sec.

The pulse then reflects when it hits something like a pump, check valve or similar and if it arrives back at the valve before the final closure the pressure surge is much reduced.

Hence a fast acting NRV close to the valve which is causing you problems might be good, or it might not.

Avoidance is much better than cure....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Regarding: "Are there check valves that are better designed for water hammer than others? For instance in a pump discharge you'd want a rapid closing check valve like a swing but could this also be the source of the water hammer?"

The silent check valve by valmatic meets this requirement.

http://www.valmatic.com/silentcheck.html

 

[BigInch]

A slowly closing check valve, maybe spring dampened, a counter weight, or a check valve with a hole in it, may avoid or lower water hammer pressures.

Reaction to change doesn't stop it

 

[DGrayPPD]

Thank you all the responses. This helps me greatly!

 

[LittleInch]

A lot of issues are solved by closing the valve just a small bit slower. Solenoid valves are the worst as they close really fast, especially small bore. Then you might need two in parallel and close them a few seconds apart.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.