Ever wondered what the difference was between external gear and rotary vane pumps? Check out this short SlideShare to see the differences between a number of positive displacement pumps, their advantages and disadvantages.

1. A Quick And Dirty Guide To
Rotary Positive Displacement Pumps

2. Rotary pumps, are a popular choice throughout
a vast range of industries.

3. From pumping liquids with high viscosities like
asphalt or honey, or low viscosity liquids like
water or ammonia, a rotary pump can do it all.

4. However, making sure you select the right
pump for your needs is key.

5. In this SlideShare, we are going to discuss the
advantages and disadvantages of a wide
variety of positive displacement pumps.

6. General Industrial Pumps
The types of general industrial pumps that we
will be going over the advantages and
disadvantages are:
– Internal gear pumps (with crescent)
– External gear pumps (spur, helical, herringbone)
– Progressive cavity
– Sliding vane pump
– Rotary lobe pump

7. Internal Gear Pumps
(with Crescent)
Advantages Disadvantages
Only two moving parts. Low speeds usually required.
Only one stuffing box. Medium pressure limitations .
Positive suction, non-pulsating discharge. One bearing runs in product pumped.
Ideal for high viscosity liquids. Overhung load on shaft bearing.
Constant and even discharge regardless of
various pressure conditions.
Available with built in safety relief valve.
Can operate equally well in either direction.
Can be made to operate with one direction of
flow with either rotation.
Low NPSH required.
Easy to maintain.

8. External Gear Pumps
(Spur, helical, herringbone)
Advantages Disadvantages
High speed. Four bushings in liquid area.
Medium pressure. Four stuffing boxes.
No overhung bearing loads. No solids allowed.
Relatively quiet.
Design lends itself to use of a wide
variety of materials.

9. Single Screw Pumps
(Progressive Cavity)
Advantages Disadvantages
High solids allowed. Cannot run dry.
Dry materials. Not for high temperatures (Stator
swells).
High viscosity. Hard to maintain.
Versatile - same pump without changing
clearance. Can be used for water or
syrup.
Expensive parts.
Good for sludge or slurry. More floor space required.
Stuffing box exposed on vacuum.

10. Sliding Vane Pumps
Advantages Disadvantages
Medium capacity. Not good with abrasives.
Medium speed. Not best for viscous liquids.
Thin liquids. Pressure medium.
Sometimes preferred for solvents LPG.
Can be made to provide variable
capacity.
One seal or stuffing box.
Develops good vacuum.

11. Lobe Pumps
(Single, Multiple & Circumferential piston)
Advantages Disadvantages
Pass medium solids. Timing gears required
Rates high acceptance. More space required.
Little galling possibility. Factory service required.
Requires two seals.