Check valves

[MHMaterials]

Hello,
Could anyone clarify if it's correct to specify swing check valves for larger diameters (up to 24"). We really don't have much pressure or temperature (max 50 bar @ 200C), and we are specifying in water services. I'm affraid of the water hammer it could produce on larger diameters.
Thanks,

 

[BigInch]

No problem with swing check valves in large diameter.

The root cause of water hammer is not closing valves too fast. It is the result of designing your pipelines too small for the flowrates you are trying to put through them.

Quick rules of thumb.
Velocities between 1 and 2 m/s normally do not produce trouble. Velocities greater than 2 m/s should be checked for water hammer sensitivity.
Velocities greater than 3 m/s must be checked.



Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[stanier]

If you have a steep discharge from the pumps to a higher elevation you will likely experience waterhammer with a swing check valve. Suggest you have your system analysed. make sure your check valve supplier provides the VR vs dV/dT so the analyst can model the system correctly.

As BigInch says it is the velocity through the valve that is important. Some "cheapskates" use a check valve the size of the pump discharge nozzle which is generally one or two sizes smaller than the pipe size.

You can find good information from Delft Laboratories or Utah State univeristy on the performance of check valves. ARD Thorley in his book Fluid Tranients in Pipeline Systems covers the modelling of check valves well.

The annulus type of check valve that closes quickly has been proven to eliminate check valve slam. I have reports of 30" swing check valves that made so much noise the operators would not go into the pump room. these were replaced by Noreva non slam check valves and the noise was eliminated.

http://www.noreva.de

Swing check valves are not the best soultion and that is why the tilt check was developed. The best check valve has a short travel and loss mass of moving parts. that is why the tit check is a better valve choice.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[MHMaterials]

Get it, thanks a lot !!!

 

[stanier]

Monicaher80,

I am intrigued when you say this is for water services but the pressure is 50bar @ 200C? What is the application?

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[Opensource]

Monicaher80,

In MSS SP-80-2003 Bronze Gate, Globe, Angle and Check Valves is your answeer.

 

[europipe]

"don't??? have much pressure or temperature (max 50 bar @200C")

Monica, you don´t have valvespecs?
I´m just as curious as mr. Stanier.
Opensource, 50 bar and you use bronze??

 

[BigInch]

Steam hammer from rapid condensation can be much worse and much more dangerous.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[MHMaterials]

Hello all...
Just to answer some of the questions posted.

Stanier: Utility water and desalinated water.
Europipe: We are validating the piping specs.
BigInch: Agree, the damage of the steam hammer is more dangerous.

Thanks for your answers.

 

[stanier]

Monicaher80,

Attached is a rpesentation on check valves that may be of interest.

Check valves for major desalination plants in Australia have usually been by Noreva in super duplex. Some plants have used twin disc types but have experienced noise. Noreva are preferred as they have tested their valves dynamically in Delft Laboratories and internally to get the dV/dt data. Lots of other companies sell "shapes". They have long lost their engineering ability and dont know why things were designed the way they were.

Water utilities generally use tilt check or Noreva non slam here on major pipelines. Those that try and use twin disc or conventional swing check have experienced difficulties, some have not. But that is just luck.

One challenge is that with an aging workforce and reduced maintenance resources things like counterweights and dashpots are just not reliable. In fact when you add a protection cage to the swing check counter weight and a dashpot you can afford a real check valve.

A check valve that helps mitigate pressure transients and protects assets such as apump are as important as a relief valve and should be given the same engineeering respect.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[gustorf]

Monicaher80,
Another rule of thumb for non slamming check valves of whatever design is a reverse velocity of less than 0,2 m/s at a given dv/dt.
Experienced check valve manufacturers should be able to give this figure based on a dv/dt that you will have to provide.