The term positive displacement pump is quite descriptive, because such pumps are designed to displace a more or less fixed volume of fluid during each cycle of operation. The volumetric flow rate is determined by the displacement per cycle of the moving member (either rotating or reciprocating) times the cycle rate (e.g. rpm).
They can be further classified as:
`text(Reciprocating pumps:)`
Pumping takes place by to and fro motion of the piston or diaphragm in the cylinder. It is often used where relatively small quantity of liquid is to be handled and where delivery pressure is quite large.
`text(Piston pump:)` A piston pump is a type of positive displacement pump where the high-pressure seal reciprocates with the piston. The pump has a piston cylinder arrangement. As the piston, goes away after the delivery stoke, low pressure is created in the cylinder which opens the suction valve. On forward stoke, the fluid filled inside the cylinder is compressed which intern opens the delivery valve for the delivery of liquid.
`text(Diaphragm pump:)` uses a combination of the reciprocating action of a rubber, thermoplastic or Teflon diaphragm and suitable non-return check valves to pump a fluid. Sometimes this type of pump is also called a membrane pump.
`text(Rotary pumps:)`
`=>` In rotary pumps, relative movement between rotating elements and the stationary element of the pump cause the pumping action.
`=>` The operation is different from reciprocating pumps, where valves and a piston are integral to the pump.
`=>` They also differ from centrifugal pumps, where high velocity is turned into pressure.
`=>` Rotary pumps are designed so that a continuous seal is maintained between inlet and outlet ports by the action and position of the pumping elements and close running clearances of the pump. Therefore, rotary pumps do not require valve arrangements similar to reciprocating pumps.
`text(Gear pumps:)` 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. The rigid design of the gears and houses allow for very high pressures and the ability to pump highly viscous fluids.
`text(Lobe pump:)` 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. Liquid travels around the interior of the casing in the pockets between the lobes and the casing. Finally, the meshing of the lobes forces liquid through the outlet port under pressure.
`text(Screw Pump:)` These pumps are rotary, positive displacement pumps that can have one or more screws to transfer high or low viscosity fluids along an axis.
Although progressive cavity pumps can be referred to as a single screw pumps, typically screw pumps have two or more intermeshing screws rotating axially clockwise or counterclockwise.
Each screw thread is matched to carry a specific volume of fluid. Screw pumps provide a specific volume with each cycle and can be dependable in metering applications.
`text(Vane pump:)` A rotary vane pump is a positive-displacement pump that consists of vanes mounted to a rotor that rotates inside of a cavity. In some cases, these vanes can be variable length and/or tensioned to maintain contact with the walls as the pump rotates.
`text(Rotary plunger pump:)` The pumping action takes place by rotating rotor and reciprocating plunger. In a rotary plunger rotary pump, the axes of the plungers are perpendicular to the rotational axis of the rotor or at an angle of not less than `45^@` to the axis; the rotor is located eccentrically with respect to the axis of the case.
Suction and forced delivery of the liquid occur with the reciprocating motion of the plungers as a result of centrifugal forces and spring action. Rotary pumps of this type may have as many as 72 plungers arranged in multiple rows, provide a delivery `Q ≤ 400` liters/min, and build up a pumping pressure `ρ ≤ 100 MN//m^2 `.
The term positive displacement pump is quite descriptive, because such pumps are designed to displace a more or less fixed volume of fluid during each cycle of operation. The volumetric flow rate is determined by the displacement per cycle of the moving member (either rotating or reciprocating) times the cycle rate (e.g. rpm).
They can be further classified as:
`text(Reciprocating pumps:)`
Pumping takes place by to and fro motion of the piston or diaphragm in the cylinder. It is often used where relatively small quantity of liquid is to be handled and where delivery pressure is quite large.
`text(Piston pump:)` A piston pump is a type of positive displacement pump where the high-pressure seal reciprocates with the piston. The pump has a piston cylinder arrangement. As the piston, goes away after the delivery stoke, low pressure is created in the cylinder which opens the suction valve. On forward stoke, the fluid filled inside the cylinder is compressed which intern opens the delivery valve for the delivery of liquid.
`text(Diaphragm pump:)` uses a combination of the reciprocating action of a rubber, thermoplastic or Teflon diaphragm and suitable non-return check valves to pump a fluid. Sometimes this type of pump is also called a membrane pump.
`text(Rotary pumps:)`
`=>` In rotary pumps, relative movement between rotating elements and the stationary element of the pump cause the pumping action.
`=>` The operation is different from reciprocating pumps, where valves and a piston are integral to the pump.
`=>` They also differ from centrifugal pumps, where high velocity is turned into pressure.
`=>` Rotary pumps are designed so that a continuous seal is maintained between inlet and outlet ports by the action and position of the pumping elements and close running clearances of the pump. Therefore, rotary pumps do not require valve arrangements similar to reciprocating pumps.
`text(Gear pumps:)` 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. The rigid design of the gears and houses allow for very high pressures and the ability to pump highly viscous fluids.
`text(Lobe pump:)` 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. Liquid travels around the interior of the casing in the pockets between the lobes and the casing. Finally, the meshing of the lobes forces liquid through the outlet port under pressure.
`text(Screw Pump:)` These pumps are rotary, positive displacement pumps that can have one or more screws to transfer high or low viscosity fluids along an axis.
Although progressive cavity pumps can be referred to as a single screw pumps, typically screw pumps have two or more intermeshing screws rotating axially clockwise or counterclockwise.
Each screw thread is matched to carry a specific volume of fluid. Screw pumps provide a specific volume with each cycle and can be dependable in metering applications.
`text(Vane pump:)` A rotary vane pump is a positive-displacement pump that consists of vanes mounted to a rotor that rotates inside of a cavity. In some cases, these vanes can be variable length and/or tensioned to maintain contact with the walls as the pump rotates.
`text(Rotary plunger pump:)` The pumping action takes place by rotating rotor and reciprocating plunger. In a rotary plunger rotary pump, the axes of the plungers are perpendicular to the rotational axis of the rotor or at an angle of not less than `45^@` to the axis; the rotor is located eccentrically with respect to the axis of the case.
Suction and forced delivery of the liquid occur with the reciprocating motion of the plungers as a result of centrifugal forces and spring action. Rotary pumps of this type may have as many as 72 plungers arranged in multiple rows, provide a delivery `Q ≤ 400` liters/min, and build up a pumping pressure `ρ ≤ 100 MN//m^2 `.
