Reciprocating Pumps

Pumps are used to move liquids or slurries. Pumps move liquid from lower pressure to higher pressure, and overcome this difference in pressure by adding energy to the system such as a water system. Pumps are used throughout society for a variety of purposes. Early applications include the use of the water pumps to pump water. Today, pumps are used for irrigation, water supply, gasoline supply, air conditioning systems, refrigeration (usually called a compressor), chemical movement, sewage movement, flood control, marine services, etc.

Reciprocating pump is a positive displacement plunger pump. It is often used where relatively small quantity of liquid is to be handled and where delivery pressure is quite large. Reciprocating pumps are used in high performance liquid chromatography (hplc). There are two general types of reciprocating pumps. The piston pump and the diaphragm pump. These types of pump operate by using a reciprocating piston or diaphragm. The liquid enters a pumping chamber via an inlet valve and is pushed out via an outlet valve by the action of the piston or diaphragm. Reciprocating pumps are generally very efficient and are suitable for very high heads at low flows. This type of pump is self priming as it can draw liquid from a level below the suction flange even if the suction pipe is not evacuated. The pump delivers reliable discharge flows and is often used for metering duties delivering accurate quantities of fluid. The reciprocating pump is not tolerant to solid particles and delivers a highly pulsed flow. If a smooth flow is required then the discharge flow system has to include additional features such as accumulators to provide even flows. Reciprocating pumps designed for delivering high pressures must include methods for releasing excessive fluid pressures. The pumps should include for built in relief valves or relief valves should be included in the fluid circuit which cannot be isolated from the pump. This feature is not required for safety for the air operated diaphragm valve.

A piston pump can be based on a single piston or, more likely, multiple parallel pistons. The pistons are reciprocated using cams or crankshafts. The stroke is generally adjustable. This type of pump can deliver heads of up to 1000 bar. The largest sizes of piston pumps can deliver flows of 40m3 /hr. In practice these pumps are more likely to be used for metering low flow rate fluids at more modest pressures in laboratories and chemical process plants. Piston pumps are not generally suitable for transferring toxic or explosive media. There are two types of diaphragm pumps. The hydraulically operated diaphragm metering pumps and the air actuated type.