Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
(OP)
Hi,
We have currently purchased one small multistage(16 stages) 50 Hz pump for water service and was asking the Vendor to have a complete rotor balancing for it. However the Vendor replied that they would only balance the shaft, stage impellers with keys (not including the half coupling and suction-first stage impellers) at operating speed (Bal Grade ISO 2.5). They said that the couplings and first stage impellers will be balanced separately at Bal Grade ISO 2.5).
Will it be difficult for OEM's to balance the rotor with the coupling hub and first stage impellers for Vertical Pump Rotors?
Thanks in advance,
Kristian
We have currently purchased one small multistage(16 stages) 50 Hz pump for water service and was asking the Vendor to have a complete rotor balancing for it. However the Vendor replied that they would only balance the shaft, stage impellers with keys (not including the half coupling and suction-first stage impellers) at operating speed (Bal Grade ISO 2.5). They said that the couplings and first stage impellers will be balanced separately at Bal Grade ISO 2.5).
Will it be difficult for OEM's to balance the rotor with the coupling hub and first stage impellers for Vertical Pump Rotors?
Thanks in advance,
Kristian





RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
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.)
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
It it's driver is only 5.5 kW. Cap 5 m3/hr rated head at 93.4 meters. 1450 rpm.
Thanks
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
More likely hydraulic imbalance will be greater than any problems with the rotor balance.
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.)
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
Thanks for the reply. I will consider accepting their proposal in this case.
But is it possible to have also just for my understanding ? I thought it is not possible due to constrains in balancing their balancing machine or something(for the coupling hub and the first stage impeller.
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
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.)
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
The complete note of the Vendor goes like:
"Balancing at balancing speed of the machine during testing. Without coupling and suction impeller. Suction impeller and coupling will be balanced separately. Rotor means pump shaft and stage impellers with keys."
The suction impeller has a different diameter (150 mm) with and the rest of the stage impellers have the same (146 mm).
The stage impellers will not be balanced separately but only together with the shaft and keys. Only the suction impeller and coupling will be balanced individually.
Do you think this is ok? I mean without balancing the stage impellers (only being covered in a balancing with the shaft and the keys).
Thanks
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
If it were 200kw at 2950 rpm it would be understandable.
However what you are
asking / proposing shouldn't be a problem.
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.)
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
Hahaha. Thanks for being gentle on me
It is actually a comment from my Client(Plant Owner), and I being the EPC contractor wanted to accommodate his request as far as possible. Thus I wanted to know if it is possible to begin with and if there really is some merit on doing this.
The pumps are KSB pumps WKB 40/16 Model.
Your replies was so helpful. Thanks
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
Johnny Pellin
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
Mechanical clearances and hydraulic uniformity are the bigger issues.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
Anyway what Artisi suggested seems to me logical. Means for this power range / duty client request could very well be over the top...
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
Regardless, note that API 610 only requires rotor balance on BB pumps, and it should not be applied to vertical pumps. It's not realistic due to the shaft length in most cases. Nobody should be doing that as a standard, or without additional cost, and it's not worth paying for.
Why was rotor balance specified?
RE: Vertical Multistage Pump Rotor Balancing (Without First Stage Impeller)
When it comes to couplings we are always here to help.
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