Download How a 4 Lobe in 5 Lobe Pump Functions

How a 4 Lobe in 5 Lobe
Pump Functions
By: Matt Hunt
Date: October 6, 2005
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
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.
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
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
References
• http://www.tpub.com/content/engine/14105
/css/14105_53.htm
• http://www.pumpschool.com/principles/lob
e.htm
• South Alberta Institute of Technology.
Correspondence Courses Power
Engineering, Section 3 Third Class
Lecture six. Pumps. Calgary Alberta.