question on modification of a moineau type pump
question on modification of a moineau type pump
(OP)
I have read in several studies that a multi-stage progressing cavity pump does not equally share the differential loading. The work done by the first couple of stages is virtually zero, and then the remaining couple increases exponentially. It is almost to the point it is ridiculous to spend the money on the additional stages. Being a subscriber to the "Kaizen theory" about life and making things better, I started to research things a little more.
There are a several solutions regarding this phenomena.
~Solutions such as increasingly less interference between the rotor and stator from the inlet to discharge ends.
~Drilling holes in the rotor complete with check valves to assist in the load equalization.
~Modifying the design so that it becomes a "progressive" cavity, fusto-conical, etc....
I was curious if recirculating a portion of the higher pressure fluid near the final stages of the pump (discharge end) back into the inlet side would serve as a possible option. I'm curious if there would be any positive results by making such a modification.
There are a several solutions regarding this phenomena.
~Solutions such as increasingly less interference between the rotor and stator from the inlet to discharge ends.
~Drilling holes in the rotor complete with check valves to assist in the load equalization.
~Modifying the design so that it becomes a "progressive" cavity, fusto-conical, etc....
I was curious if recirculating a portion of the higher pressure fluid near the final stages of the pump (discharge end) back into the inlet side would serve as a possible option. I'm curious if there would be any positive results by making such a modification.





RE: question on modification of a moineau type pump
Similar modifications are made to centrifugal pumps in order to artificially shift the operating point toward desirable regions, but Moyno pumps are in no way remotely similar to centrifugal pumps, so I would not expect similar results.
I think you'd have to modify the Moyno pump to do what you suggest.
Do not expect any sort of warranty support.
Mike Halloran
Pembroke Pines, FL, USA
RE: question on modification of a moineau type pump
RE: question on modification of a moineau type pump
The Caveman approach to our industry has been more stages = more power...grunt grunt grunt. Sadly the extra stages are merely added dollars with negligible and marginal efficiency for the investment.
Warranty is not of any concern. We get 300 operating hours at best before we repair the stator
RE: question on modification of a moineau type pump
I am quite surprised there isn't a more efficient option oput there, but as you don't say what the fluid is (PC pumps are normally used for abrasive fluids with big stones in it), maybe it is worth it.
The philosophy behind these pumps is a little strange so perhaps some more reading up on them would be useful.
In either situation, I find it difficult to understand how bypassing part of the pump / turbine, is doing any good.
Perhaps a diagram would help?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: question on modification of a moineau type pump
RE: question on modification of a moineau type pump
I'll leave it to others to see if they can understand what problem you're actually trying to solve with the pump design.
RE: question on modification of a moineau type pump
If you are only getting 300 hours operating time before failure, you need a different pump. These pumps are ridiculously expensive to repair.
RE: question on modification of a moineau type pump
I have seen modified profile rotary screw compressors used as motors, they are very efficient. And they work very similar to PC pumps.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: question on modification of a moineau type pump
the application is in a harsh environment (solids/abrasives/temperature/high torque requirements) and it also restricted diametrically. So the PC pump is the best fit for application. Turbines are used as an alternative, however the RPM output is typically too high and gear reduction systems don't provide the reliability or desired torque output.
The idea was to recirculate the increased pressure back into the inlet side. However I have several concerns.
1. The possibility it would go into self-destruct mode by continually recirculating increased pressure, so the Pressure relief valve may prevent that.
2. Is the lower volume of recirculated fluid (approximately 20%), albeit a higher pressure, substantial enough to increase the overall working pressure of the initial stages of the pump?
Here's a rough sketch...The numbers are merely examples.
The thought is to increase the pressure capability of the pump, by improving the work load performed by all the stages, and not just the last few. In theory, this should allow for more differential pressure across the pump and thus shift the torque curve accordingly.
The idea may be totally crazy and not work, that's why I came to the brain trust.
I'm with you BIMR, the extra stages while not a total ruse, it's not worth the added costs. Unfortunately, what I have seen, is that all the vendors know of this phenomena and have spent lots of money studying it. A solution may just not be feasible, and it's just an idiosyncrasy that we have to live with. I'd be happy if I could achieve a 15%-25% improvement. It would be substantial for our application.
RE: question on modification of a moineau type pump
RE: question on modification of a moineau type pump
RE: question on modification of a moineau type pump
Where do you get the fluid for recirculation from? Does your PC motor have an outlet along the casing? Can you point us at some monufactuerers info on the PC motor you are using so we can see the thing?
RE: question on modification of a moineau type pump
In general the reason for additional stages is to inhibit the inevitable "slip" of product from one chamber to the adjacent, lower pressured chamber. Each stage added helps to spread the pressure drop and lower what each stage has to handle.
You can also accomplish the same thing by tightening the clearances between rotor and stator, or hardening the softer stator. But then you encounter wear problems by not allowing the softer stator to "absorb" hard particles as the rotor rolls over it. Also there will be much more expensive machining costs to produce the tighter tolerances and reliability reduction.
This whole idea sounds like a very academic exercise that should remain within academia.
RE: question on modification of a moineau type pump
RE: question on modification of a moineau type pump
If you left off the last 6 stators, you would also have zero flow, from a 10 stator pump.