Hi all.

Can anyone advise me how to calculate the pump diffuser pass frequency?

The pump is a multistage boiler feed pump with 5 impeller vanes on the 1st stage and then 7 impeller vanes on the other stages and each diffuser has 11 channels.

Our VA software calculates the diffuser pass frequency as 10 orders for the 5 vane impeller and 21 orders for the 7 vane impeller, but it would be good to know how this is calculated

Thanks
James

James,

There are typically three fundamental frequencies from diffusers:
1) shaft speed x # diffuser-vanes for one impeller vane passing all diffuser vanes
2) shaft speed x # impeller-vanes x # diffuser-vanes for all impeller vanes passing all diffuser vanes
3) shaft speed x # impeller-vanes for all impeller vanes passing one diffuser vane

This would be common for a single stage pump or hydraulic turbine. For multi-stage pumps, there is, or can be, an interaction according to James E. Corley. A good reference that supports your numbers is: "Machinery Malfunction Diagnosis and Correction" by Robert C. Eisenmann on pages 485-486 and Table 10-1.
Your VA software calculates 10xSS and 21xSS, and this corresponds to those in Table 10-1. Anyway, any multiple of shaft speed equal or greater than impeller-pass is an good candidate for pulsation frequencies!

Walt

Further to Walt's reply, the two tables attached may help you. Sources are;

Bolleter, U (1988) Blade-passing tones of centrifugal pumps Vibrations, Vol 4 (3), Sep [ARTICLE]

Corley, JE (1987): Tutorial session on diagnostics of pump vibration problems Proceedings of the 4th International Pump Symposium, Texas A&M University [PAPER]

Makay, E (1993) Be aware of acoustic resonance in pump vane/impeller problems POWER- article

Impeller-diffuser_interaction_(Makay-Bolleter).pdf (44 KB, 56 downloads)

Corley table this time

Impeller-diffuser_interaction_(Corley).pdf (6 KB, 50 downloads)

Hi Walt & Ray

Thank you very much for the information, I will try to research the papers you mentioned

Thanks again
James

Hi Ray,

Thanks again for posting the information.

I will actually be in Victoria in 5 weeks time; we are researching the area…
Where is the best place I can purchase copies of the source material you posted on?


Thanks
James

quote:

Originally posted by Ray Beebe:
Further to Walt's reply, the two tables attached may help you. Sources are;

Bolleter, U (1988) Blade-passing tones of centrifugal pumps Vibrations, Vol 4 (3), Sep [ARTICLE]

Corley, JE (1987): Tutorial session on diagnostics of pump vibration problems Proceedings of the 4th International Pump Symposium, Texas A&M University [PAPER]

Makay, E (1993) Be aware of acoustic resonance in pump vane/impeller problems POWER- article

You may be interested in this thread:

http://maintenanceforums.com/e...891058304#5891058304

There's some discrepancy between the predicted frequencies using Corley's and Foiles' methods.

Steve

Hi Steve,

Thanks for the link to the thread, it’s a very interesting subject. Where could I get a copy of the mentioned papers as I would like to study this further
Regards
James

quote:

Originally posted by Steve Ciesla:
You may be interested in this thread:

http://maintenanceforums.com/e...891058304#5891058304

There's some discrepancy between the predicted frequencies using Corley's and Foiles' methods.

Steve