Industrial Pump Types Explained: Progressing Cavity, Peristaltic, Centrifugal and More

Torqueflow-Sydex Ltd is pleased to offer the following reference guide to pump types, pumping principles and related information. It draws on the knowledge bank at Torqueflow-Sydex and publicly available reference material, and is intended as a starting point when comparing pumping technologies for your application.

Progressing Cavity Pumps

A progressing cavity pump is a type of positive displacement pump, also known as a progressive cavity pump, eccentric screw pump or cavity pump. It transfers fluid by means of the progress, through the pump, of a sequence of small, fixed-shape, discrete cavities as its rotor is turned. This means the volumetric flow rate is proportional to the rotation rate and only low levels of shear are applied to the pumped fluid. These pumps are therefore ideal for fluid metering and for pumping viscous or shear-sensitive materials. The cavities taper down toward their ends and overlap with their neighbours, so in general no flow pulsing is caused by the arrival of cavities at the outlet.

Rotary Positive Displacement Pumps

Positive displacement rotary pumps move fluid using the principles of rotation. The vacuum created by the rotation of the pump captures and draws in the liquid. Rotary pumps are very efficient because they naturally remove air from the lines, eliminating the need to bleed air from the lines manually.

Reciprocating Positive Displacement Pumps

Reciprocating positive displacement pumps have an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands, and flows out of the discharge as the cavity collapses. The volume is constant for each cycle of operation.

Metering Pumps

A metering or dosing pump moves a precise volume of liquid in a specified time period, providing an accurate flow rate. Delivery of fluids in precise, adjustable flow rates is sometimes called metering. The term is based on the application rather than the exact kind of pump used. Although metering pumps can pump water, they are often used to pump chemicals, solutions or other liquids, and many are rated to pump against high discharge pressures. They are typically made to meter at practically constant flow rates (averaged over time) within a wide range of discharge pressure.

Submersible Pumps

A submersible pump (or electric submersible pump, ESP) has a hermetically sealed motor close-coupled to the pump body, with the whole assembly submerged in the fluid to be pumped. The main advantage is that it prevents pump cavitation, a problem associated with a high elevation difference between the pump and the fluid surface. Submersible pumps push fluid to the surface, as opposed to jet pumps which have to pull fluid.

Gear Pumps

A gear pump uses meshing gears to pump fluid by displacement. They are one of the most common pump types for hydraulic fluid power applications and are also widely used in chemical installations to pump fluids of a certain viscosity. There are two main variations: external gear pumps, which use two external spur gears, and internal gear pumps, which use an external and an internal spur gear. Gear pumps are positive (fixed) displacement, meaning they pump a constant amount of fluid for each revolution. Some gear pumps are designed to function as either a motor or a pump.

Peristaltic Pumps

A peristaltic pump is a type of positive displacement pump used for pumping a variety of fluids. The fluid is contained within a flexible tube fitted inside a circular pump casing. A rotor with a number of rollers, shoes, wipers or lobes attached to its external circumference compresses the flexible tube. As the rotor turns, the part of the tube under compression is pinched closed, forcing the fluid through the tube. As the tube opens to its natural state after the passing of the cam, fluid flow is induced into the pump. This process is called peristalsis and is used in many biological systems, such as the gastrointestinal tract. Typically two or more rollers or wipers occlude the tube, trapping a body of fluid between them which is then transported toward the pump outlet. Peristaltic pumps may run continuously, or be indexed through partial revolutions to deliver smaller amounts of fluid.

Centrifugal Pumps

Centrifugal pumps transport liquids by converting rotational kinetic energy into the hydrodynamic energy of the liquid flow. The rotational energy typically comes from an engine, electric motor or turbine. In the typical simple case, fluid enters the pump impeller along or near the rotating axis, is accelerated by the impeller, and flows radially outward into a diffuser or volute chamber, from where it exits. Common uses include water, sewage, petroleum and petrochemical pumping.

Rotary Lobe Pumps

Rotary lobe pumps can handle solids such as fruit and vegetables, slurries, pastes and a variety of liquids. If wetted, they offer self-priming performance, and their gentle pumping action minimises product degradation. They offer continuous and intermittent reversible flows and can operate dry for brief periods. Flow is relatively independent of changes in process pressure, so output is relatively constant and continuous.

Diaphragm Pumps

A diaphragm pump (also known as a membrane pump, air-operated double diaphragm pump (AODD) or pneumatic diaphragm pump) is a positive displacement pump that uses a combination of the reciprocating action of a rubber, thermoplastic or PTFE diaphragm and suitable valves on either side of the diaphragm — check valves, butterfly valves, flap valves or other shut-off valves — to pump a fluid.

Vane Pumps

A rotary vane pump is a positive displacement pump consisting of vanes mounted to a rotor that rotates inside a cavity. In some designs the vanes are variable length and/or tensioned to maintain contact with the walls as the pump rotates. The simplest vane pump is a circular rotor rotating inside a larger circular cavity, with the centres of the two circles offset, causing eccentricity. The vanes slide into and out of the rotor and seal on all edges, creating vane chambers that do the pumping work. On the intake side the vane chambers increase in volume and fill with fluid forced in by the inlet pressure; on the discharge side the chambers decrease in volume, forcing fluid out of the pump. The action of the vane drives out the same volume of fluid with each rotation.

Chopper Pumps

A chopper pump is a centrifugal pump equipped with a cutting system to facilitate the chopping and maceration of solids present in the pumped liquid. Its main advantage is that it prevents clogging of the pump and adjacent piping, as all solids and stringy materials are macerated by the chopping system. Chopper pumps exist in various configurations, including submersible and dry-installed designs, and are typically equipped with an electric motor to run the impeller and provide torque for the chopping system. Due to their high solids-handling capability, chopper pumps are often used for pumping sewage, sludge, manure slurries and other liquids containing large or tough solids.

Magnetic Drive Pumps

Magnetic drive pumps vary from the traditional pumping style in that the motor is coupled to the pump by magnetic means rather than a direct mechanical shaft. The pump works via a drive magnet driving the pump rotor, which is magnetically coupled to the primary shaft driven by the motor. They are often used where leakage of the pumped fluid poses a risk — for example aggressive fluids in the chemical or nuclear industries. With no direct connection between motor shaft and impeller, no gland is needed and there is no risk of leakage unless the casing is broken. Since the pump shaft is not supported by bearings outside the pump housing, support inside the pump is provided by bushings.

Need help matching a pump type to your application? Contact the Torqueflow-Sydex team on +44 (0)23 8212 8627 or info@sydexpumpuk.com.