What is a Positive Displacement Pump
A positive displacement pump (PD Pump) forces fluid to move by trapping a fixed amount of the fluid and forcing (displacing) that trapped volume into the discharge pipe.
The positive displacement pump provides an approximate constant flow at fixed speed, despite changes in the counter pressure.
Positive displacement pumps all pulsate, meaning that their volume flow within a cycle is not constant. The variation in flow and speed leads to pressure fluctuations due to resistance in the pipe system and in valves.
Applications for Positive Displacement Pumps
Positive Displacement pumps are used in industrial, food processing, water treatment, and petrochemical industries. Generally PD Pumps (such as peristaltic or diaphragm pumps) are also ideal for fragile substances such as cell cultures or shear sensitive polymers due to their gentle action.
Classes of Positive Displacement Pumps
Diaphragm Pump Air Operated
An air operated diaphragm pump (also known as a membrane pump) is a type of positive displacement pump that uses compressed air as a power source. The compressed air is shifted from one chamber to the other by a linked shaft that allows the chambers to move simultaneously.
Diaphragm Pump Electric
A Diaphragm Pump driven by an electric motor is a more energy efficient and low maintenance solution as compared to air operated diaphragm pumps. They are ideal for applications that require low pulsation and a smooth flow.
Diaphragm pumps are a class of positive displacement pump.
A gear pump employs a system of meshing of gears to move fluids. Because of the mechanism involved gear pumps qualify as positive displacement pumps. For every revolution the gears in a gear pump make the same amount of fluid is moved.
Due to their design, gear pumps are often used for transporting high viscosity fluids, especially in the chemical industry.
Helical Rotor Pump
The helical rotor pump is a class of positive displacement pump that works by the rotation of a helical rotor pushing discrete quantities of liquids through the pump.
A corkscrew-like action provides a pulse free flow where an accurate flow rate is determined by the rotor speed allowing for the helical rotor pump to also be used as a dosing pump.
Oil & Grease Pump
Oil & Grease Pumps are a class of positive displacement pumps that are designed to handle automotive and equipment fluid pumping requirements including oil and grease in industrial environments.
Peristaltic pumps are a class of positive displacement pumps that used for products that are too corrosive, abrasive or viscous for other pumps. They have no seals, valves or glands and are economical to maintain.
A piston pump is a class of positive displacement pump where the high-pressure seal reciprocates with the piston.
Piston pumps can be used to move liquids or compress gases and can also pump viscous media and media containing solid particles.
Rotary Vane Pump
Rotary vane pumps are simple displacement and positive fixed pumps that are adjustable. They normally produce higher efficiencies compared to gear pumps and are generally utilised for average pressures as high as 18 bars.
They are simply designed to promote efficiency. This makes rotary vane pumps last for long periods of time with very little maintenance. Their simplicity also makes them cost-efficient to repair and purchase.
Self Priming Pump
A Self-Priming pump is a type of pump that is designed to be able to lift fluid from below its suction without the need of a foot valve, or hydraulic column of fluid in the suction line.
The pump operates with the aid of fluid in the pump volute.
Solenoid pumps are a class of positive displacement pump which use a diaphragm and solenoid assembly to displace the fluid into the discharge line.
The solenoid assembly consists of an electromagnet and spring. When current is applied to a solenoid the electromagnetic core moves a diaphragm into the discharge position.