Which one? Gear or Screw? 1

[Sabergg1981]

Hi
I want to know when handling fluids with high viscosity up to 900 which pump is better performance?
Gear pump or screw pump?
Is there any recommendation how to select a suitable pump for viscous fluids? a chart or table based on capacity, head,...?
Best Regards

 

[MortenA]

Have you tried looking at progressive cavity? I know this is not what you ask for but just checking. PG pumps are really good for high viscous non newtonian stuff. They can even be made for food and pharma service. E.g. you can pump margerine

Best regards

Morten

 

[zdas04]

The patent was held by a worker in a peanut butter plant.

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.

 

[micalbrch]

He or she probably meant progressive cavity pumps when asking for screw pump. Eccentric screw pump is a synonym for a progressive cavity pump.

And I agree with MoltonA. A progressive cavity/eccentric screw pump is better than a gear pump for viscous fluids.

 

[TenPenny]

How can anyone determine that a PC pump is the right pump? The viscosity is listed as 900. 900 what? What is the fluid? What's the capacity? What's the required pressure? What's the operation?

Conceivably, the best pump could be a gear, a PC pump, a two screw pump, or a three screw pump. How can anyone jump to conclusions about a PC pump, based on the given information?

 

[micalbrch]

Inspiration.

 

[MortenA]

@Tenpenny: Nobody told anybody to do anything! This is not a free consultancy! I asked if he had thought about using a PC pump. Maybe he already considered this since a screw pump sometime is a PC pump (i don't have English as my mother tongue and directly translated i related the term "srew pump" to another type of pumps). So chill out man (and never expect free consultancy services).

Best regards

Morten

 

[zdas04]

And I just interjected a pointless factoid. Chill.

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.

 

[Sabergg1981]

Our service is fuel oil with viscosity up to 900 cSt. Capacity is about 300 m3/hr and head is about 40m. Max pumping Temperature is 55C.
I am wondering which type of Positive Displacement pump is suitable? Screw or Gear? and Why?
Moreover, i dont know about PC pump? is there any reference about these kind of pump?
Thanks

 

[Sabergg1981]

@ mikalbrch

Can you explain about your resons for selecting eccentric screw pump than a gear one? Are there any criteria about this?

 

[TenPenny]

For Fuel Oil, in a service like this, I'd use a 3 screw pump. You'll need about 125kW or so. It will not be inexpensive, this is a fairly big pump.

A PC pump at this temperature, you'd have to carefully select the elastomer for the stator. As well as the fact that you'll have a hard time finding one that will do the capacity you have listed.

With a 3 screw pump, the fuel oil will lubricate the screws, so as long as it's reasonably clean, you'll get long life.

 

[Sabergg1981]

@ TenPenny

What are the advantages of selecting a 3 screw pump than a gear pump? i think its better to select a gear pump.

 

[micalbrch]

Sabergg1981: My recommendation to use a PC pump more than a gear pumps was the more gentle pumping principle and the lower speed. But for your application a triple screw pump as suggested by TenPenny is for sure the better option.

 

[Sabergg1981]

Can anyone tell me why 3 screw pump is preferred than a gear pump?

 

[TenPenny]

A three screw will generally have longer lifespan, assuming the fluid is relatively clean, as the screws are in rolling contact with each other, as opposed to the sliding contact of the faces of the gear teeth. They will tend to be much quieter, and generally have lower pulsations in the delivery stream.

 

[waross]

Three Screw Pump

http://www.youtube.com/watch?v=BM-vUd9fAbc

Progressive Cavity pump. (PC)

http://www.youtube.com/watch?v=RaFLfSjDIjo&NR=1&feature=endscreen

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[psv1990]

A pump to consider is a diaphram pump. Much more economical and may be better suited to the oil you are pumping.

 

[DubMac]

Is there some reason you are not considering a centrifugal pump for this service? Your discharge head of 40m is quite low and easily handled. In addition, the capacity would require a sizable PD pump spinning fast. Centrifugal would be much less costly option.

One consideration in looking at the screw pumps is the number of mechanical seals you would need. If the manufacturer recommends external bearings, you will have 2 mechanical seals on each shaft.

 

[DubMac]

Ah yes, the viscosity. Forget the centrifugal. Viking gear pumps are used in fuel oil service extensively.