High vibration on centrifugal pump

Dear expertise, 

 

I need your suggestion, 

 

I have a case and need your advise.  I have centrifugal pump 2975 rpm,  520 kW. In april 2017, i have a dominant spectrum in 1x and 3x,  1x = 0.673 mm/s,  3x = 1.162 mm/s.  But suddenly when I throttled the valve on 10% opened,  the spectrum becomes 1x = 0.334 and 3x = 5.116 mm/s. Found harmonic 1x motor speed. 

Firstly I thought that is the effect from cavitation.  But i didn't see any raised floor on high frequency.

 

Note : this pump using sleeve bearing on DE and NDE. EC00003

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Original Post

Quote:

"1x and 3x,  1x = 0.673 mm/s,  3x = 1.162............................. the valve on 10% opened,  the spectrum becomes 1x = 0.334 and 3x = 5.116 mm/s."

I would think it would be a 3 blade  impeller and possibly some type of flow problem, causing vanepass and 1x (at times) to be high, even though it does not show a "raised floor" as you mentioned. May be a worn impeller.

Thanks and Have a Great Day,

Ralph

Ralph Stewart posted:

Quote:

"1x and 3x,  1x = 0.673 mm/s,  3x = 1.162............................. the valve on 10% opened,  the spectrum becomes 1x = 0.334 and 3x = 5.116 mm/s."

I would think it would be a 3 blade  impeller and possibly some type of flow problem, causing vanepass and 1x (at times) to be high, even though it does not show a "raised floor" as you mentioned. May be a worn impeller.

Thanks and Have a Great Day,

Ralph

Thank you Ralph,

 

I have just informed by my colleague that the number of blade is 4. I agree with you,  this caused by blade pass or flow problem.

 

Have a great day

 

Krocoo

Ralph Stewart posted:

We have some of these "Amine"  pumps at an oil refiner, and they all show a 3x. I have never seen or heard what the blade count is, but it looks like 3 in our pumps. I think I will ask around next time we are there.

I will attach a spectrum later.

Thanks.

Dear Ralph, 

 

I think so,  that vibration came out from blade pass.  ��

Thank you for your information,  that is really help me. 

abdillah al bandari posted:

is there is any reason why you open valve only at 10%, so basically the pump in good condition if running normally. i agree with Mr Ralph that problem due to flow problem causing vanepass.

Thanks Mr Abdillah

 

We choke the line because noise problem in the vessel when the valve opening is too high. 

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