Progressive Cavity vs. Screw Pumps

[aspearin1]

Can anyone direct me to a site or illustration to help me visually understand the differences between Progressive Cavity and Screw Pumps? They seem rather similar. Fundamentally, how are they different?

ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee

 

[ruble3]

try this:

http://www.psig.org/papers/2001/0210.pdf

 

[MortenA]

You can also check pumpuniversity at:

http://www.pumpuniversity.com/

On the start page click on the picture of a "disasemblied" pump and then Look under Moineau pumps for progressive cavity and screw pump for .... well screw pumps

A digest would be:

A progressive cavity allways have a fixed part - the stator - This is the "shell" of the pump and is made of some "soft" material such as rubber viton, bunan or other types of rubber. Then there is a rotor - the moving part - made of steel (or another metal). It look somewhat like a corcsrew. When roattetd inside the stator a pocket (cavity) is "pushed forward" (progressively) thus creating the moving force.

A screw pump, consists of two or more screws. The screws mesh with each other, letting the liquid flow through the pofiles of the screws. The screws are eather both driven by external timing gears, or the idler screw is driven by liquid pressure.

The most common screw pump design is with 3 rotating screws with different profiles. The center screw is driven by an external gear, and the two outer screws are driven by the liquid pressure. The screw helixes provides sealing elements, when the pump rotates. The pump relies on the viscosity of the liquid for sealing and for driving the idler screws.

Best regards

Morten