Plunger pump vs Piston pump – Difference between Plunger and Piston

In this articles we will see difference between plunger and piston pump ,working of both types of pumps.

Pumps are used to transfer fluids from one location to another by increasing the pressure of the fluid and supplying the driving force necessary for flow.
Power in form of electrical or steam energy may be transformed into mechanical energy which is used to drive the pump. Part of this mechanical energy is added to the fluid the as work energy and the rest is lost as friction due to inefficiency of the pump and the drive.

The different types of pumps can be classified as

Reciprocating or positive displacement pumps
Rotary positive displacement pumps
Rotary centrifugal pumps

Piston Vs Plunger

A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder wall.

A plunger is a device that is used to release stoppages in plumbing. The tool consists of a rubber cup with an attached stick “shaft”, usually made of wood or plastic. A different bellows-like design also exists, usually constructed of plastic. For the common plunger, the cup is pushed down against the drain opening, and either pressed hard into the drain to force air in, or is pushed down until the rubber cup is flattened, then pulled out, causing a vacuum that attracts material. The intent is to loosen or break up a blockage caused by excessive material in the drain.

Difference Between Plunger pump and Piston Pump:

Piston Pump:

A piston pump is a type of positive displacement pump where the high-pressure seal reciprocates with the piston.
The piston pump consists of a cylinder with a reciprocating piston connected to a rod which passes through a gland at the end of the cylinder. The liquid enters from the suction line through a suction valve and is discharged through a delivery valve. These pumps may be single acting or double acting.
The theoretical delivery of a piston pump is equal to the total swept volume of the cylinders. The actual delivery may be less than the theoretical value with volumetric efficiency greater than 90%.
The piston pump can be directly driven by steam or electric motor.
The piston type pump is comparatively simple in construction and operates with a high efficiency over a wide range of operating conditions. They can handle viscous liquids and develop high pressures.
It can operate against a high head and does not require priming. However, delivery is uneven and presents an uneven load on the driving mechanism.
Since with a well maintained piston pump the volume delivered is accurately known these pumps find use as metering pumps.

Plunger Pump:

A plunger pump is a type of positive displacement pump where the high-pressure seal is stationary and a smooth cylindrical plunger slides through the seal. This makes them different from piston pumps and allows them to be used at higher pressures.
Plunger pumps differ form piston pumps in that they have one or constant diameter plungers reciprocating through packing glands and displacing liquid from cylinders in which there is considerable radial clearance. They are always single acting in the sense that only one end of the plunger is used in pumping the liquid.
Plunger pumps are available with one, two, three, four, five or even more cylinders. Simplex and duplex units are often built in a horizontal design. Those with three or more cylinders are usually of vertical design. The driver may be an electric motor, a steam or gas engine or a steam turbine.