Positive Displacement Pumps (PDPs)

1. Positive Displacement Pumps (PDPs) TEAM RAMAKANTH CE-02,E2 CIVIL ENGINEERING DEPT. RGUIIIT-NUZ NUZVID.

2. POSITIVE DISPLACEMENT PUMP(PDPs) BASIC DEFINITION: A constant flow rate fluid pumping deviceuse to displace the fluids(usually viscous & fragile) in the directionof pressure force. WORKING PRINCIPLE: It operates in such a way that it takescertain FIXED amount of the fluids and transfer it to desired placewith the use of cavities (in some type) arranged in a manner thathaving increasing area at suction side(inlet) and decreasing atdischarging side(outlet)

3. POSITIVE DISPLACEMENT PUMP RECIPROCATING ROTARY GEAR PISTON LOBE PLUNGER VANES DIAPHRAGM PERISTALIC SCREW PROGRESSIVE CAVITY

4. RECIPROCATING PUMPS • 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. • They are commonly named as check valve or non-return valve

5. PISTON PUMP Piston pumps and plunger pumps use a mechanism (typically rotational) to create a reciprocating motion along an axis, which then builds pressure in a cylinder or working barrel to force gas or fluid through the pump. The pressure in the chamber actuates the valves at both the suction and discharge points

6. PLUNGER PUMP Rotary piston and plunger pumps use a crank mechanism to create a reciprocating motion along an axis, which then builds pressure in a cylinder or working barrel to force gas or fluid through the pump. The pressure in the chamber actuates the valves at both the suction and discharge points.

7. DIAPHRAGM PUMPS The most popular type of diaphragm pump is the Air-Operated Diaphragm Pump. These pumps use compressed air as their power supply. They also include two chambers with a diaphragm, inlet check valve and outlet check valve in each chamber.

8. PUMP TYPE AND ITS SPECIAL PURPOSE

9. ROTARY PUMPS: • 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 isPROGRESSIVE CAVITY PUMP .

10. GEAR PUMP • Working; fluid on the inlet side flows into and is trapped between the rotating gear teeth and the housing. The fluid is carried around the outside of the gears to the outlet side of the pump. • Use; A gear pump uses the meshing of gears to pump fluid by displacement. they are one of the most common types of pumps for hydraulic fluid power applications. Gear pumps are also widely used in chemical installations to pump high viscosity fluids. • Advantages ; 1)Capable of handling a wide range of viscosities 2)Less sensitive cavitation 3)Simple to maintain 4)Bi-rotational 5)Self priming 6)Simple to rebuild • Disadvantages; 1)Fluid must be free of abrasives 2)Meshing gears can also be noisy

11. LOBE PUMP • Working; Lobe pumps are similar to external gear pumps in operation in that fluid flows around the interior of the casing.As the lobes come out of mesh, they create expanding volume on the inlet side of the pump. Liquid flows into the cavity and is trapped by the lobes as they rotate • Use; Rotary lobe pumps are non-contacting and have large pumping chambers, allowing them to handle solids such as cherries or olives without damage. they are also used to handle slurries,pastes and a wide variety of other liquids.if wetted,they offer self-priming performance • Advantages; 1)Pass medium solids 2)No metal to metal contact 3)Non-pulsating discharge • Disadvantages; 1)Requires timing gears 2)Require two seals 3)Reduced lift with thin liquids

12. VANE PUMP: Vanes or blades fit within the slots of the impeller. As the rotor rotates (yellow arrow) and fluid enters the pump, centrifugal force, hydraulic pressure, and/or pushrods push the vanes to the walls of the housing. Fluid then exits the discharge port

13. PERISTALTIC PUMP: A rotating shoe or roller passes along the length of the hose or tube totally compressing it and creating a seal between suction & discharge side of the pump, eliminating product slip

14. SCREW PUMP: It uses one or several screws to move fluids or solids along the screw(s) axis

15. PROGRESSIVE CAVITY PUMP: The rotor seals tightly against the stator as it rotates, forming a set of fixed-size cavities in between. The cavities move when the rotor is rotated but their shape or volume does not change. The pumped material is moved inside the cavities

17. 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

18. 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).