Progressive Cavity Pump 1

[mech1122]

Hi Everyone,

I would like to ask about progressive cavity pump rotor. Per my client specification it stated Rotating elements shall be balanced per ISO 1940-1 Grade G2.5 but Vendor takes an exception on this requirement due to the design of the equipment.

Is it necessary to balance the rotor of this equipment? your reply is highly appreciated. thanks.

 

[MortenA]

Wouldnt your client have to accept this at the end of the day? (Maybe pr. your recommendation). IMO its a bit risky using a site like this for critical decitions. What will you say if something goes wrong: I asked some - to me unknow people - and they said: Go ahead?

Find somebody how knows and has professional integrity to say what the right decition in your situation would be (and pay him).

Best regards, Morten

 

[TenPenny]

I have many clients who want centrifugal pump rotors/impellers balanced to G1.0, but not a one of them has ever asked to have a PC pump balanced. I'm not sure that it would be possible, practical, or useful to do so.

Considering the rotating speed for a PC pump should be 300 rpm or less, I really don't know why they'd want G2.5. To me, that sounds like someone insisting on a spec without understanding the application of it.

 

[zdas04]

Good advice Morton. I'll go ahead an provide some of that nearly anonymous input, but the OP should take it for what it is worth.

Progressing (NOT "Progressive") Cavity Pumps turn really slowly (80-400 rpm) and will often have slime an clumps on the rotor. Spending any money post-manufacture verifying balance is a true waste of money.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[gilus02]

I have read the post and the responses and a question raised for me. I have seen in API-610 the some different method for coupling balancing like:
- ISO 1940-1 G6.3
- WITH PROPRIETARY CLAMPING DEVICE
- PER ISO 14691
- PER ISO 10441
- API 671

I don't know any criteria for choosing one of them. I assumed the selection is based on experience. You are appreciated if giving me any rules of thumbs!

 

[DubMac]

Good rule of thumb: Don't bother trying to balance a PC pump rotor.

 

[Compositepro]

A PC pump rotor orbits or wobbles around an imaginary axis. It cannot be balanced.

 

[LittleInch]

Mech1122,

Is your client spec just a generic rotating machinery spec or specific to pc pumps?.if the former as i suspect then you have good reasons for ignoring this. When i bought my first PC pump i thought it was the strangest thing i had ever got hold of, but by God it did a great job empting some well head sumps full of sh1t with not even a cough.

IMO, accept the vendor exception.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Pumpsonly]

Not possible to balance a PC pump rotor. It is supported by the stator when rotates.

 

[Artisi]

mech1122, you should advise the client that the manufacturer has taken exception to it but would review their decision based on an engineering justification as to why it is necessary, that should be sufficient to have them (client) wave the requirement.
This way you don't have to ignore the spec or maybe enter into a one-way argument with your client, especially as the spec. will take precedence.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)