How a 4 Lobe in 5 Lobe Pump Functions

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How a 4 Lobe in 5 Lobe Pump Functions

• By Matt Hunt
• Date October 6, 2005

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Definitions

• Discharge/exhaust Exit point of fluid from the
  pump.
• Prime To prime a pump is to maintain or replace
  fluid in the pump when the pump is not
  functioning.
• Pump Device used to impart energy to a fluid in
  order to move it from one point to another.
• Rotary Pump Pumps which consist of a closed
  casing in which gears, lobes, vanes, or screws
  rotate with a minimum of clearance. These
  rotating parts trap the liquid and push it around
  the casing from suction to discharge.
• Suction Entry point of fluid into the pump.
• Vanes Are a mechanism used to optimize the seal
  of the pump. They are mechanically held in their
  slots, and to some extent, free to move outward.
  Centrifugal force keeps the vanes snug against
  the chamber and the other rotating members

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How it works

• The four lobe in five lobe pump has a central
  rotor with 4 lobes. These four lobes act as gear
  teeth that are form fitting to an outer rotor
  with five inner lobes. These two rotors are
  offset yet form fitting. The offset is to trap
  fluid and force it from the suction (or entry)
  and push it to the discharge (or exhaust). The
  lobes are form fitting to ensure that there is no
  back feed (no fluid comes out the suction or in
  through the discharge).
• Most rotary pumps must be primed. If they do not
  have the fluid that is to be pumped in them they
  will be full of air. This results in the pump not
  working as the air flow will not create enough
  pressure to move the less viscous fluid. This can
  easily be avoided with the use of valves. The
  type of valve is dependent on operating pressure
  (high or low) and the properties of the fluid
  being handled such as viscosity, temperature,
  clear or containing suspended solids.

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Advantages

• Consistent flow of fluid resulting in continuous
  pressure versus surges of pressure
• Pass medium solids
• -Easy to maintain and clean, good for the
  food industry
• Less friction (than reciprocating pump) resulting
  in longer lifespan

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Disadvantages

• Reduced lift on low viscosity liquids
• Cannot handle high pressure
• Must have a relief valve on the discharge side of
  the pump
• Must be primed to function

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References

• http//www.tpub.com/content/engine/14105/css/14105
  _53.htm
• http//www.pumpschool.com/principles/lobe.htm
• South Alberta Institute of Technology.
  Correspondence Courses Power Engineering, Section
  3 Third Class Lecture six. Pumps. Calgary Alberta.