What is a centfigual screw pump? 3

[cttp2003]

Sir,
Can some expert tell me the difference between centrifugal pump and a centrifugal screw pump?
Thank you.

 

[Scipio]

I've never heard of a 'centrifugal screw pump' before, maybe you mean a 'rotary' screw pump? These differ from centrifugal pumps (which rely on translating kinetic energy into potential energy) in that they are rotary positive displacement devices. That is, they move a fixed volume of fluid by mechanically transporting it from a low pressure to a high pressure.

A good quick comparison would be on IMO's web site,

http://www.imo-pump.com.

They manufacture both screw & centrifugal pumps, and have some useful documents there, for example

http://www.imo-pump.com/brochures/ipgp-02.pdf

which is complete with cross-sectional drawings and a selection chart of applicable services.

Hope that's what you were looking for!

 

[LCCBUR]

Take a look at

http://www.hidrostal.co.uk

 

[Scipio]

Ahh, in that case, forget what I said

 

[cttp2003]

LCCBUR,
Thanks.
What are the advantages and disadvantages between a centrifugal screw pump and a standard submersible pump?
Regards.

 

[25362]

I think the the website brought by LCCBUR is quite explicit, isn't it ?

 

[LCCBUR]

As 25362 said, that website is quite explicit.
It may be interesting to make a search on GOOGLE on the word "hidrostal".
Regards.

 

[longeron]

Is Wemco still associated with Hidrostal?

 

[d23]

cttp2003, all:

I may have missed something here! Do competent engineers go to a single specific pump manufacture (inter-net sales) to determine the correct pump for a given (all) applications? Depending on the manufacture would or could you expect a possible biased opinion? Hummmm

There will be days when a screw pump is better, but centrifugal pumps have their place too!!!!!

 

[dadfap]

LCCBUR,

PCPs, progressive cavity pumps, have a number of advantages over centrifugal pumps
1. They will work with a lower intake pressure
2. To a certain extent they will handle gassy fluids better
3. To a certain extent they will handle entrained solids(sand etc)
4. They can handle viscous fluids better

Disadvantages
1. The elastomer can be problematic at elevated temperatures
2. The elastomer can swell with the gas often leading to rotor sizing problems, although the suppliers are getting better at modeling this
3. They run into head and rate limitations before centrifugals do

As d23 alludes to, any manufacture will steer you in the direction of their product. The few manufacturers that deal in both will give you an honest opinion, after all they will make money from both.

My thoughts

 

[CB2]

Well I did the "google" search and must say the info available is minimal for understanding why the screw centrifugal (Hidrostal) does a unique pumping job in it's niche market. One can only speculate on why more pump manufacturers don't web publish their "stuff".

cttp2003
Some of the +/- of screw centrifugals:
- Will cost more than standard pumps
- Don't think they offer much in special materials of
construction.
- In many cases this pump will be dimentionally larger
and heavier.
- The screw impeller cannot be "trimmed" to meet a
specific hydraulic condition. You pick a pump curve
that may fit, or to get the speed you need use V-belts,
or use a VFD.
- You don't want this pump to run back on the curve
to "shutoff". The screw will present a "positive
displacement" characteristic hydraulically and demand
alot of HP. Similar to a propeller pump at shutoff.
+ Rather steep performance curves.
+ Very good efficiency that I have found to be real.
+ Their biggest claim is very low shear rates and high
solids content slurry pumping. The simple explanation
is that solids in a slurry do not accelerate at the
same rate as the liquid when pumped. This
characteristic is a problem for centrifugal pumps, thus
the big performance derates and 2%-3% solids limits.
The screw part of the screw centrifugal accelerates the
solids "with" the liquid so by the time the slurry gets
to the centrifugal section of the impeller there are
minimal loses. This pump was designed to pump live
fish.

LCCBUR made a good point in bringing up progressive cavity pumps, they would overlap with the screw centrifugal on many applications.

We are having fun.

 

[gunnarhole]

CTTP2003

You might also want to take a look at

http://www.lawrencepumps.com/products.htm

Regards,

Gunnar

 

[TD2K]

I don't know CB2. The comment with "live" fish in quote marks bothers me, maybe it only applies at the inlet to the impeller?



No, I'm not serious.

 

[Berko]

Hidrostal screw centrifugal pumps have the following advantages, which we have found when using them.

1. Can handle sludges upto 13% DS
2. Excellent rag & solids handling
3. Range of CI, SS & high chrome iron(hard) materials of construction.
4. Dry well subs use a self contained oil cooling jacket (won't block like a product recirc jacket)
5. Very Low Shear (shrouded versions of the impeller do pump live fish !)
6. Very low NPSH R (down to less than 1M in some cases)
7. Available as dry 7 wet well submersibles + long & close coupled end suction pumps
8. Externally adjustable conical liner (instead of wear rings) which adjusts both axial & radial impeller clearances
9. Extremely rugged construction, these units are built to last

I hope this helps