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Pump discharge line vibration at 100bar

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chiru123pc

chiru123pc

Mechanical
Joined
Dec 9, 2009
Messages
18
Location
IN
Dear Experts,

Please find the attached CII file and Site vedio. The pump discharge line is vibrating heavily before 100bar.

the process parameters are as follows; Design press= 197bar, operating press= 172bar, ope temp = 150deg C.

kindly suggest to avoid the vibration. The model frequency matched to = 6hz, no FIV performed.

Do it require damping type or special type supports?

The secondary steel portals which are exciting to be size to be modified?




Regards
PC
 
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I do not have access to CAESAR II, but I might guess the following from the video since you have not mention about the type of the pump and the fluid.

Either the pump is reciprocating or blower or gear pump the piping natural frequency is matching the pump frequency or multiples which cause the vibration, perhaps the system is resonating. You need to find out the the forcing harmonics of the pump and get away from them at least for 3 harmonics by increasing (most likely) or reducing the stiffness of the piping.
If the fluid is liquid and temperature allows you may need to put a pulsation dampener to the system to eliminate the mechanical and pulsation vibrations.
 
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Dear saplanti,

Thanks for your prompt response. The pump is plunger type and used for flushing water with high pressure.
 
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So you may need a pulsation dampener. Talk to your pump supplier about suitable one which may directly be attached on the pump.
 
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Piston pumps are notorious for inducing vibrations and you need to run this through specialist software for vibration analysis purposes. CII won't hack it.

That software models all the pulsation dampers, pipe supports, compliant supports, fixed supports, elbows, tees etc.

It's a real pain but if you don't you will get destructive vibrations.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Dear saplanti,

Yes the pulsation damper valve is directly mounted on the pump nozzle. Even though when the pressure reaches 100bar more vibration starts.

We adjusted the support span too,but no use.

 
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Dear Littleinch,

Yes you are right.we are trying to contact the vendor sending him the as-built isometric drawings for pulsation study.
 
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Well I hope you get it fixed before it shakes itself to death. They were very violent vibrations you videoed. Normally you can only feel them not see them visibly moving.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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There may be problem in the selection of the dampener, volume, required flow rate, pressure and temperature needs to be considered. You need to talk to the pump supplier about the dampener size and your process conditions. I normally would expect the pulsation is dropped substantially with the adequate volume, perhaps some mechanical vibration would stay up to the 2 or 3 rd support. These supports are to be focussed on taking the vibration and allowing the thermal expansion. Support stiffnesses are to be in accordance with API 674 (you perhaps use API618 and/or API 688 guidance). Sometimes the supports are very flexible and the supports shake with the pipe. It means they do not do the job required. Just go through the supports and check one by one what they do to stop vibration.
 
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