Pump Discharge Orifice Noise And Vibration Issue

Dear All,

We are working on cooling water pumping system; we needed to increase capacity of existing cooling water system with available pump which is having high head and low flow. We have installed this pump with orifice and operated in parallel to existing pump. Now with this parallel operation we are facing noise and vibration at downstream of orifice. Data for the pump and orifice is as under

Pump flow; 2650 USGPM

Pump discharge pressure; 12.5 barg.

Pressure at downstream of orifice; 5.7 barg

Orifice size; 3.66-inch

Pipe size: 10-inch

We have gain in capacity with this addition of this high head and low flow pump

If anyone can suggest solution to avoid noise and vibration issue, Please share your thoughts

Regards

Why not remove the orifice, put globe valves in the discharge and throttle as needed.

Discharge piping need to be check. Nozzle load and dynamic stress analysis need to be done. Sometime it happens when the pump is not properly align with suction and discharge piping.

The noise and vibration is very likely to be from the orifice. The drop from 12.5 to 5.7 is in the cavitation regime. Cavitation causes lots of noise and vibration.

The other way, put VFD's on the pump and reduce the pump speed as required to achieve the flow required.  The pressure will just balance out to match the loss in the system and so only the flow needs to be controlled. Presumably if you have a flow transmitter at the common discharge... 

Anyhow, running at a lower speed, at just the required speed to meet the required flow will save energy and since the speed is lower, less wear and tear and less noise as well.

Two orifices in series.

Yup, the other way is for multi hole orifice or multi stage orifice to gradually let down the pressure to reduce the noise and vibration.

I suggested a globe valve because I wasn't sure if there will be further need for throttling in future.

Thanks  thorium90 and 12345656

Is there any way I can calculate the minimum pressure that is occuring at vena contracta and also what is the range for Cavitaion Index.

Is there any software for calulating multi hole oriifce?

Regards

Unfortunately, I'm not an orifice sizing expert. But I used these devices in one of my recent projects. I will PM you separately for the contact.

Thanks to all 

we have resolved the subject issue by providing multi hole orifice.

Regards

Good to know it has been solved.

By the way, there are also multi hole throttling valves as well.

Attached a picture of the valve.

Edited by thorium90, 03 December 2018 - 10:32 AM.

hello,

To add to this thread a paper about multi holes valves .

hope this is helping you and others

Breizh