Twin Screw Pump RPM

Are the pump and motors matched?

ie does the 2900 RPM motor is with its pump and ditto for 1450 RPM pump?

If you want to couple 2900 RPM motor to 1450 RPM pump, it is needless to say you are in for trouble.

(You can run the 2900 RPM pump with 1450RPM motor though with the resultant reduction in flow rate but no other harm)

As far as the pump motor is matched set, it really may not matter much in either, only ensure the pump suited for the application (You are working with highly inflammable liquid) and unless exactly suited to the application, the higher heat generation (consequent to the RPM) may blow things over. But if it is designed for the application I don't see why 2900 RPM system will be as good as the 1450 RPM one (and if not designed the 1450 may be worse).

Twin screw pump does not have any inbuilt gear box for the speed reduction (at least the ones I have come across) since you always select the motor correspondingly and you can always go for VFD if you want the speed control. These are simple positive displacement pumps, where two (or three or more) screws rotate and the helical flutes pump in the fluid.

wot R U talkin bout.

Do not use SMS TXT

The rotation speed of the pump is not as important as the performance curve for that pump at whatever speed. It is the selected performance of the pump that determines the correct rotation speed, not the other way round.

If the flow/pressure characteristic is the same for the two pumps then the rotation speed can be selected on the basis of maintenance preferences, which are secondary to the pump performance.

only the difference will be the flow rate. the screw pump will provide same pressure regardless of the rpm. the greater the rpm, the greater the flow. twin screw pumps do not need gearboxes. it only depends on the size of the pump and the designers choice if he requires reduction or not.

SB

2900 RPM motor makes more noise and the life of bearings and sealings is less ....

As I get your question you are stating that one vendor offered you a certain model twin screw pump for your application with a 2950 rpm driver and another vendor offered you the same model (and exactly the same size?) as the first vendor but driven by a 1450 rpm driver.

Since these are positive displacement pumps one expects double the volume from the higher speed driver assuming everything else is the same. If one is offering a smaller model at the higher speed then it would appear more logical. The slower speed but larger model if offered at the same price would probably be my choice.

Twin screw pumps often have driving gears to synchronize the two screws. I prefer the IMO 3 screw design where you have a center driving screw and two outer driven screws provided there are sufficient lubricating properties of the fluid.

When the pumped fluid is not very lubricating by nature, the synchronizing gears help prevent rotor to rotor hard contact since it is the gears doing the driving and not the screws themselves.

Proper selection has more to do with material, temperature, viscosity, cleanliness of product and available suction conditions. If suction conditions are marginal and temperatures are high a larger casing-slower speed pump would probably be a better selection. For cool lubricating type medium and plenty of suction pressure probably could go either way depending on cost.