Water valve noise 1

[lurch17]

Suffering extreme noise when closing a 2" ball valve in clean water - 12 psi differential and approximately 15 psig static at the valve inlet. Crazy, it only make noise closing, not opening. So I replaced it with another brand of ball valve (Griswold Soft-touch) - no difference!

The flow is approx 70 gpm with the valve wide open.

Anyone know why it's making so much noise? And what to do about it?

 

[imok2]

Lurch The noise seem to eminate from the following:
The pressure peaks induced by the bubble implosions cause material erosion as well as a loud typical noise. The theoretical approaches to explain how noise develops are based on individual bubbles which implode concentrically
in an infinitely expanded fluid and without affecting each other. The cavitation bubble can then be regarded as an isotropic radiator of zero order (monopole source) which creates in the far field the sound pressurThis is complicated However I urge you to read the following for a possible solution.

http://www.samson.de/pdf_en/l351en.pdf

 

[ChasBean1]

12 psid across the valve alone? Does it need that much?

The drop leaves you with 3 psig at the outlet, which is not enough for minimum pressure in a closed water system. Re-evaluate your need for this DP and your expansion tank charge.

 

[ione]

American Water Worker Association has defined three levels of cavitation:
• Incipient cavitation is the beginning stage of cavitation associated with fluctuating noise
• Constant cavitation is a steady noise coupled with possible valve damages.
• Choked cavitation is the point where the vaporization of the fluid reaches sonic velocity in the valve port.

You have to evaluate your cavitation index S defined as follows

S = (P1-Pv)/(P1-P2)

P1 = upstream pressure
P2 = downstream pressure
Pv = vapour pressure

The lower the cavitation index the higher the likelihood to have cavitation. Valve manufacturers should have graphs showing a safe operating zone for each opening angle. Please consider that water temperature plays a role: the higher the temperature the higher the vapour pressure, the lower the cavitation index.
Generally ball valves are less sensitive to cavitation if compared to plug or butterfly valves, anyway the best choice is represented by special conceived anti-cavitation valve.

 

[lurch17]

Thanks for the valuable info folks - I understand the causes much better and now think I am on a solution path. Will post more details when I have the solution (or not).