Positive displacement pumps (PDPs) are fluid pumping devices that provide a constant flow rate by displacing fluids, often viscous and fragile, using cavities designed for suction and discharge. There are various types of PDPs, including reciprocating pumps (which can be piston, plunger, or diaphragm types) and rotary pumps (such as gear, lobe, vane, and screw pumps). PDPs are ideal for high viscosity fluids and applications requiring self-priming, but they may not be suitable for low viscosity fluids or high flow rate scenarios due to slip losses.

1. POSITIVE DISPLACEMENT PUMP(PDPs)
BASIC DEFINITION: A constant flow rate fluid pumping device
use to displace the fluids(usually viscous & fragile) in the direction
of pressure force.
WORKING PRINCIPLE: It operates in such a way that it takes
certain FIXED amount of the fluids and transfer it to desired place
with the use of cavities (in some type) arranged in a manner that
having increasing area at suction side(inlet) and decreasing at
discharging side(outlet).
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2. 𝟐
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3. RECIPROCATING PUMP:
• Its construction includes the air pumping cavity run via motor,
connected with cam with the two set of valves*
 If air pumping is done by piston then it is termed as PISTON PUMP.
 if pumping of air is done via plunger then it is known as PLUNGER PUMP
 If air is pumped through diaphragm then it is called as DIAPHRAGM PUMP.
*valves are of such type that it allows flow only in one direction. Named
commonly as check valve or non-return valve.
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4. PISTON PUMP:
𝟒
𝟐𝟐

5. PLUNGER PUMP: 𝟓
𝟐𝟐

6. DIAGRAGM PUMP: 𝟔
𝟐𝟐

7. 𝟕
𝟐𝟐

8. ROTARY PUMP:
A pump type wherein fluid is transferred via rotating element,
meshing or squeezing the fluid in some pattern.
When meshing is of gears it is called GEAR PUMP.
When meshing is of lobes it is LOBE PUMP.
When meshing is of screws it is SCREW PUMP.
When rotating element contains vanes it is called VANE PUMP
When rotating element contains hose it is PERISTALTIC PUMP
When rotating element contains increasing cavity it is
PROGRESSIVE CAVITY PUMP.
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9. WORKING
PRINCIPLE OF
ROTARY PUMP
PUMP
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10. GEAR PUMP (EXTERNAL & INTERNAL):
CRESCENT
DRIVER
DRIVEN
𝟏𝟎
𝟐𝟐

11. MESHING GEARS
SPUR HELICAL HERRINGBONE
Design Complexity, Cost
Vibration, Chatter
increase
increase
𝟏𝟏
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12. LOBE PUMP: 𝟏𝟐
𝟐𝟐

13. VANE PUMP: 𝟏𝟑
𝟐𝟐

14. PERISTALTIC PUMP: 𝟏𝟒
𝟐𝟐

15. SCREW PUMP: 𝟏𝟓
𝟐𝟐

16. SLANTEDSTRAIGHT 𝟏𝟔
𝟐𝟐

17. PROGRESSIVE CAVITY PUMP: 𝟏𝟕
𝟐𝟐

18. 𝟏𝟖
𝟐𝟐

19. WHY to chose PDPs
• High viscosity fluids
• Flow is regardless of pressure
• Changing viscosity fluids(varies with pressure)
• High Pressure
• Shear Sensitive Liquids
• Self-Primer
• Low flow
• Pumping Slurries
• No shaft seal
𝟏𝟗
𝟐𝟐

20. WHY not to chose PDPs
• Safety or Relief valve is necessary.
• Low viscosity.
• High gpm (gallons per minute).
• High rpm(revolutions per minute).
• Losses occur in form of slip(due to pressure variation).
𝟐𝟎
𝟐𝟐

21. 𝟐𝟏
𝟐𝟐

22. 𝟐𝟐
𝟐𝟐