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. 

Greetings team,

1. The pump and motor horizontal set or vertical set up?

2. The values you are showing even 5.116 mm/s is still satisfactory limit after throttling.

3. The rise on impeller vane pass because of stall effect due to throttling  and also see the load drop by throttling from full flow to restricted flow. 

4. Please check the pump max pressure developed when full valve closed and compare with pump capacity pressure and volume ratings.

5. In closed loop system if the discharge valve throttled there will be rise in vibration due to throttle effect and also observe the load should drop.

6. If you wish to operate continuous throttle mode, install a by pass to reduce the flow.

 

Thanks and regards

Chary

chary tatta posted:

Greetings team,

1. The pump and motor horizontal set or vertical set up?

2. The values you are showing even 5.116 mm/s is still satisfactory limit after throttling.

3. The rise on impeller vane pass because of stall effect due to throttling  and also see the load drop by throttling from full flow to restricted flow. 

4. Please check the pump max pressure developed when full valve closed and compare with pump capacity pressure and volume ratings.

5. In closed loop system if the discharge valve throttled there will be rise in vibration due to throttle effect and also observe the load should drop.

6. If you wish to operate continuous throttle mode, install a by pass to reduce the flow.

 

Thanks and regards

Chary

Dear Mr Chary

 

1. The pump in horizontal set up.

 

Thank you very much for your detail solution. I really appreciate it.

 

Onur Gün posted:

Are there any coupling (3- jaw coupling) on this pump-motor?

Mr Onur, 

 

Yes,  the coupling is jaw coupling.  But i can't remember the number of jaw. I will check it when I back on the field. 

Do you think that there is a possibility that 3x caused by the coupling (if the coupling is 3 jaw coupling) ? 

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