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Positive Displacement Pumps - Basic Principle
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Positive Displacement Pumps - Basic Principle

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Positive Displacement Pumps - Operation …

Positive Displacement Pumps - Operation

This presentation gives a basic idea of Positive Displacement Pump Basic Principle of Operation.

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  • 1. POSITIVE DISPLACEMENT PUMPS
  • 2. POSITIVE DISPLACEMENT PUMPS PUMP Rotodynamic Positive displacement Centrifugal Rotary Reciprocating Axial flow Mixed flow Gear Piston Lobe Diaphragm Turbine Sliding Vane Screw Plunger
  • 3. POSITIVE DISPLACEMENT PUMPS Positive displacement pumps physically entrap a quantity of liquid at the suction of the pump and push that quantity out the discharge of the pump. A definite volume of liquid is delivered for each cycle of pump operation. The positive displacement pump delivers liquid in separate volumes with no delivery in between, Positive displacement pumps can be grouped into three basic categories based on their design and operation. The three groups are reciprocating pumps, rotary pumps, and diaphragm pumps.
  • 4. POSITIVE DISPLACEMENT PUMPS Principle of Operation: Check valves in the suction and discharge ports allow flow in only one direction. Section Discharge
  • 5. POSITIVE DISPLACEMENT PUMPS Principle of Operation: During the discharge stroke, the piston moves to the right, seating the check valve in the suction line and opening the check valve in the discharge line.
  • 6. POSITIVE DISPLACEMENT PUMPS Principle of Operation: During the suction stroke, the piston moves to the left, causing the check valve in the suction line between the reservoir and the pump cylinder to open and admit water from the reservoir.
  • 7. POSITIVE DISPLACEMENT PUMPS Principle of Operation: The volume of liquid moved by the pump in one cycle (one suction stroke and one discharge stroke) is equal to the change in the liquid volume of the cylinder as the piston moves from its farthest left position to its farthest right position.
  • 8. POSITIVE DISPLACEMENT PUMPS PUMP Rotodynamic Positive displacement Centrifugal Rotary Reciprocating Axial flow Mixed flow Gear Piston Lobe Diaphragm Turbine Sliding Vane Screw Plunger
  • 9. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Reciprocating positive displacement pumps are generally categorized in four ways: 1. Direct-acting or Indirect-acting. 2. Simplex or Duplex . 3. Single-acting or Double-acting . 4. Power pumps.
  • 10. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Direct-Acting and Indirect-Acting Pumps: Direct-acting pumps have a plunger on the liquid (pump) end that is directly driven by the pump rod (also the piston rod or extension thereof) and carries the piston of the power end.
  • 11. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Direct-Acting and Indirect-Acting Pumps: Indirect-acting pumps are driven by means of a beam or linkage connected to and actuated by the power piston rod of a separate reciprocating engine.
  • 12. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Simplex and Duplex Pumps: A simplex pump, sometimes referred to as a single pump, is a pump having a single liquid (pump) cylinder. A duplex pump is the equivalent of two simplex pumps placed side by side on the same foundation.
  • 13. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Simplex and Duplex Pumps: The driving of the pistons of a duplex pump is arranged in such a manner that when one piston is on its upstroke the other piston is on its down stroke, and vice versa. This arrangement doubles the capacity of the duplex pump compared to a simplex pump of comparable design.
  • 14. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Simplex and Duplex Pumps:
  • 15. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Single-Acting and Double-Acting Pumps: A single-acting pump is one that takes a suction, filling the pump cylinder on the stroke in only one direction, called the suction stroke, and then forces the liquid out of the cylinder on the return stroke, called the discharge stroke. A double-acting pump is one that, as it fills one end of the liquid cylinder, is discharging liquid from the other end of the cylinder. On the return stroke, the end of the cylinder just emptied is filled, and the end just filled is emptied.
  • 16. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Single-Acting and Double-Acting Pumps: One possible arrangement for single-acting and doubleacting pumps is shown :
  • 17. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Power Pumps: Power pumps convert rotary motion to low speed reciprocating motion by reduction gearing, a crankshaft, connecting rods and crossheads. Plungers or pistons are driven by the crosshead drives. Rod and piston construction, similar to duplex double-acting steam pumps, is used by the liquid ends of the low pressure, higher capacity units.
  • 18. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Power Pumps: The higher pressure units are normally single-acting plungers, and usually employ three (triplex) plungers. Three or more plungers substantially reduce flow pulsations relative to simplex and even duplex pumps. Power pumps typically have high efficiency and are capable of developing very high pressures. They can be driven by either electric motors or turbines.
  • 19. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Power Pumps: They are relatively expensive pumps and can rarely be justified on the basis of efficiency over centrifugal pumps. However, they are frequently justified over steam reciprocating pumps where continuous duty service is needed due to the high steam requirements of direct-acting steam pumps.
  • 20. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Power Pumps: In general, the effective flow rate of reciprocating pumps decreases as the viscosity of the fluid being pumped increases because the speed of the pump must be reduced. In contrast to centrifugal pumps, the differential pressure generated by reciprocating pumps is independent of fluid density. It is dependent entirely on the amount of force exerted on the piston.
  • 21. POSITIVE DISPLACEMENT PUMPS PUMP Rotodynamic Positive displacement Centrifugal Rotary Reciprocating Axial flow Mixed flow Gear Piston Lobe Diaphragm Turbine Sliding Vane Screw Plunger
  • 22. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Piston/Plunger Pump: A tight-fitting piston in a closed cylinder or a loose-fitting plunger acting as a displacer are familiar versions of the common reciprocating pump.
  • 23. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Piston/Plunger Pump: Piston/plunger pumps have the following characteristics: • Capable of almost any pressure, and of large flow capacity. • Capable of almost any pressure, and of large flow capacity.
  • 24. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Piston/Plunger Pump: Piston/plunger pumps have the following characteristics: • • NPSH requirements for these pumps are more complex than for rotary or kinetic pumps due to the pulsed nature of the suction. Are expensive in large sizes. • Easily controlled by stroke adjustment or variable speed.
  • 25. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Piston/Plunger Pump: Advantages include the following: • The ability to develop high pressures in a single stage. • • High reliability. The ability to develop high pressures in a single stage.
  • 26. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Piston/Plunger Pump: Disadvantages include the following: • The necessity of slow speed operation • The necessity of slow speed operation
  • 27. POSITIVE DISPLACEMENT PUMPS PUMP Rotodynamic Positive displacement Centrifugal Rotary Reciprocating Axial flow Mixed flow Gear Piston Lobe Diaphragm Turbine Sliding Vane Screw Plunger
  • 28. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Diaphragm Pump: Fluid is transferred by the pressure of a diaphragm that flexes to form a cavity that is filled by liquid. A diaphragm pump has the following characteristics: •Transfers virtually any liquid. •Designs can handle high temperatures. •Designs can handle high temperatures.
  • 29. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Diaphragm Pump: •Is infinitely adjustable in capacity and discharge pressure by regulating the movement of the diaphragm. •Can be flexed by either an air supply or a reciprocating plunger. •Is used for pumping chemicals, glue, ink, solvents, fat, grease, and dirty water.
  • 30. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Diaphragm Pump: •Is limited to low flow and head application due to the design of the flexible diaphragm.
  • 31. POSITIVE DISPLACEMENT PUMPS PUMP Rotodynamic Positive displacement Centrifugal Rotary Reciprocating Axial flow Mixed flow Gear Piston Lobe Diaphragm Turbine Sliding Vane Screw Plunger Blow case pump
  • 32. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Blow case pump: This is a special configuration of a positive displacement pump . It consists of two pressure chambers that are alternately filled with liquid. When a chamber is filled, air or steam is forced into the chamber.
  • 33. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Blow case pump: This causes the contents to be discharged into the system. The two chambers alternate in this action, resulting in a fairly constant discharge. It is popular for pumping hot condensate. ?Why because there is no heat loss, and flashing liquid can be transferred.
  • 34. POSITIVE DISPLACEMENT PUMPS PUMP Rotodynamic Positive displacement Centrifugal Rotary Reciprocating Axial flow Mixed flow Gear Piston Lobe Diaphragm Turbine Sliding Vane Screw Plunger Blow case pump Open-screw pump
  • 35. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Open-screw pump: This is an example of a pump configuration that does not conform to the classical forms discussed in the preceding sections. An open-screw pump consists of a U-shaped channel into which a rotating screw fits tightly (minimal clearance).
  • 36. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Open-screw pump: Modern forms of this pump are usually quite large. This pump is used extensively in waste water plants for moving contaminated water, and in irrigation channels for lifting large volumes of water.
  • 37. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Open-screw pump: An open-screw pump is well suited for this purpose as there is little chance of down time. The large sizes with closely fitted screws are reasonably efficient.
  • 38. POSITIVE DISPLACEMENT PUMPS :Reciprocating pumps Open-screw pump: One version surrounds the screw within a large tube and the whole assembly is then rotated. All bearings are thus outside of the liquid and there is no liquid leakage.