Twin Screw Sanitary Pumps; What are They and When Would You Use One?

September 20, 2013
Twin Screw Pump

Twin Screw Pump

The use of sanitary twin screw pumps in the sanitary process industry is on the rise.  The main suppliers of these pumps are Axiflow and Bornemann.  Many people don’t know much about these pumps, how they work, and when they should be applied. Sanitary twin screw pumps operate by using two contact-free inter-meshing screws enclosed in a pump housing.

They are available with C Face mounting options and generally don’t require a gear reducer.  They can be close coupled with the motor connected directly to the input shaft.  The pumps are bi-directional and have no real wear parts except for the mechanical seal.

Sanitary twin screw pumps offer these benefits:

  • Virtually no pulsation
  • Low shear, twin screw pumps also handle large solids very well
  • Low NPSH requirements
  • Twin screw pumps are multiphase pumps and are excellent at pumping products with entrained air
  • Dual Duty- Properly sized, sanitary twin screw pumps can also serve as a CIP pump, eliminating a second CIP pump, and bypass piping and a significant amount of I/O
  • Twin screw pumps can run dry (with proper seal quench)

Like any tool, sanitary twin screw pumps have to be applied properly.  They are not right for every application.  Here are some of the drawbacks.

  • Cost:  These are expensive pumps.  In applications where a diaphragm or lobe pump is already working well, a twin screw pump is not cost effective.
  • To accomplish both process and CIP applications, you will need a larger motor than you would expect. A good rule of thumb is they will use the same horsepower motor as your CIP supply pump.  If you can eliminate adding a CIP feed pump this may make sense.  If you already have a functioning CIP system it may not.

Like most good tools, sanitary twin screw pumps have to be applied properly.  If you have NPSH issues, entrained air in your product, are pumping large solids or are concerned about line pulsation the sanitary twin screw pump might be something worth exploring.
Holland Applied Technologies