High Pressure Relief Valve Noise 2

[Cee555]

I have a pump aplication that is being tested with a Lewa Plunger Pump, the relief valve pressure is 3200 PSI at 0.32 GPM max. When the system reaches half that flow rate the Relief valve or Relief Valve piping makes a screeching noise? What could be the cause of that noise? The Relief Valve is sized at 1/4" relief.

Cee

 

[MikeHalloran]

Pressure control valves, of the kind that are _intended_ to be flowing much of the time, require internal damping to keep them from making noise.

Absent damping, they work like relaxation oscillators; pressure rises past the threshold, valve opens, relieving the pressure locally. The reduced pressure travels upstream in the protected volume as a rarefaction wave. The reduced pressure causes flow toward the relief valve. With the flow, the local pressure rises above the setpoint, and the cycle repeats.

I.e., the screeching is likely the relief valve opening and closing, rapidly.



Mike Halloran
Pembroke Pines, FL, USA

 

[budt]

Another reason Relief Valves make noise as they pass fluid at pressure is from the expansion of air trapped and compressed in the fluid. This is seen in aeration at the vales outlet since the bubbles have decompressed to atmospheric pressure. The bubbles may be quite small but there are often lots of them.

The above is more evident in thick fluids such as hydraulic oil.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us

 

[Cee555]

I do believe that a pulsation dampner may eliviate this problem. Have never worked with Plunger style pumps before so this is a learning experience for me, thank you both for your advice and shared knowledge. I had no idea a site existed like this, this would have been very usefull to me some two years ago, but thats another story.
Any suggestions on how I might go back to my customer for funds to throw towards some Pulsation Dampners///lol

 

[MikeHalloran]

Funds?

A tee with a vertical leg ending in a cap, with a volume greater than the piston displacement would be an economical start.



Mike Halloran
Pembroke Pines, FL, USA

 

[Cee555]

Thanks Mike by funds I meant money.
We built the units to customer specs. A pulstation dampner was not mentioned but it is now required.

 

[Cee555]

Mike would you know where I can find a diagram of this?

A tee with a vertical leg ending in a cap, with a volume greater than the piston displacement would be an economical start.

 

[MikeHalloran]

Diagram:

= PIPE CAP
|
| trapped air
|
PUMP >>--------+------------------->> LOAD
TEE

The air trapped in the vertical pipe leg works like a spring. The leg absorbs most of the pump output while the pump is discharging, and supplies the load when the pump is not discharging.




Mike Halloran
Pembroke Pines, FL, USA

 

[Cee555]

>^ PRV (air trapped)
^
^ Discharge
^>>>>>>>>>
^
Pump --^-----|
--^-----|
^
^ Suction

This is my diagram as you can see the fluid is coming from the bottom, being discharged through the top of the pump, there is a tee that branches the fluid to the discarge end of the system and as you can see the PRV sits at the top.
Where would I place the Tee Cap as you have constructed?

 

[MikeHalloran]

Replace the tee with a cross, add a short horizontal nipple, an elbow, the vertical leg and cap.


CAP >^ PRV (air trapped)
| ^
| ^ Discharge
+--------^>>>>>>>>>
^
Pump --^-----|
--^-----|
^
^ Suction

It might work better if the positions of the damper leg and PRV on the cross were reversed, i.e., if the pump discharge points directly into the damper.



Mike Halloran
Pembroke Pines, FL, USA

 

[Cee555]

Thank you Mike, at this point I have nothing too lose!!!
What is the science behind this actually?

Ces

 

[MikeHalloran]

The damper functions pretty much like the bag in a bagpipe.

Speaking of bags, one noise damper often found in a hydraulic system is a bladder accumulator, with they nitrogen pressure adjusted to suit.

I didn't suggest that before because you asked for quick & cheap, and because I haven't figured out exactly what you're trying to do.

A word of caution: If the fluid you're pumping is flammable, e.g. hyraulic oil, then the cheap trapped air noise damper would be a really bad idea, and an accumulator of some kind is strongly indicated.






Mike Halloran
Pembroke Pines, FL, USA

 

[Cee555]

Mike that is good to know!!!
The fluid that is being pumped is methanol at 3200PSI max. Without a pulsation dampener the relief valve is opening and closing quite rapidly with the pulsation affect of the plunger pump, a high pitch noise accompanies the slapping, I do believe that the spring is resonating at this high pressure.

 

[MikeHalloran]

Oh-kay. Forget the tee/cap idea.

Trapping air anywhere in that system is not a good idea. [ The essence of the problem is that air plus fuel at 3200 psi plus a small mechanical shock fulfills all the requirements for a Diesel combustion event, i.e., explosion. ]

Instead, you need an accumulator, probably a spring- loaded diaphragm type. Sort of like a Lewa diaphragm pump head but with a spring instead of a drive ram, and no check valves. I'm surprised they don't offer such a thing.

Is the noise present on the customer's installation, or just on your test rig?




Mike Halloran
Pembroke Pines, FL, USA

 

[Cee555]

It's present at the current test stage.
And the pump being used is a Lewa pump, and yes I have just learned that they offer dampners. They could have suggested this much earlier in our design stage, needless to say we are not satisfied with the Lewa Rep. However, we will have to eat up the cost and place a dampner on the discharge of these systems. All avenues have been exhausted, and the project is now well below margin. The branch sounded like a good idea, lol.

 

[abcmex]

Cee555
Lewa has its own literature regarding dampeners and in case of a dosing pump I have seen several applications with dampeners. If the local Lewa rep has not advise you properly contact their Head Office.

A customer specification is not always complete :-(

rgs