Reciprocating pumps are a type of positive displacement pump that uses alternating force and suction – using a piston or diaphragm – to create a steady, pulsing flow, with one or more check valves to regulate and direct flow through the system. The pump chamber is repeatedly expanded and contracted to draw the fluid through an intake valve and force it out through the other end. They are able to generate high pressures.
These pumps range from small, hand-powered pumps, to big pumping systems. Due to the broad range of pumps that are classed as reciprocating pumps, they play an integral role in a number of sectors including private, public, and commercial/industrial sectors in applications such as irrigation, public water supplies, fire safety systems, and where viscous liquids need to be moved.
We look at the most common types of reciprocating pumps below:
Piston pumps
Piston pumps (also known as well service pumps, high-pressure pumps, or high viscosity pumps) use one or more reciprocating pistons to move fluid through a cylindrical chamber which is usually driven by an electric motor, internal combustion engine or another power source through a crankshaft or connecting rod.
These pumps have to contract and expand cavities that move in a reciprocating motion rather than a circular (rotary) motion, alternately drawing the fluid in and then pushing it out under pressure. The periphery of the piston usually has one or more o-rings to seal against the cylinder as the piston moves and check valves on either side of the pumping chamber to stop fluid flowing in the wrong direction.
They can deliver high pressures typically between 50-5,000psi, flow rates between 5-700gpm, and are capable of handling both viscous and solids-containing media.
These pumps can be single acting where the piston moves in both directions to complete a full pumping cycle, or doubling acting where there are two sets of check valves (one on each side of the piston) with fluid on both sides of the piston and a full pumping cycle being completed each time the piston moves from one end to the other.
Piston pumps are commonly used as hydraulic pumps to power heavy machinery or in smaller applications such as paint sprayers. Larger, more robust piston pumps are found in oil production and other industrial applications, with axial and radial style pumps used in high-tech and advanced industrial applications.
Plunger pumps
Plunger pumps operate in the same way as piston pumps, but rather than using pistons, they use plungers to move fluid through a cylindrical chamber, typically driven by electric motors, but steam and hydraulic drives are also used.
These pumps work with the drive moving one or more plungers back and forth inside the cylinder. This cylinder comes with packing rings to prevent the fluid from leaking past the plunger as it moves. At the end of the cylinder, there is a pumping chamber with two check valves located at the inlet and outlet which stop the fluid from reversing direction as it passes through. Fluid is drawn into the chamber as the plunger moves away from it, creating a vacuum, and the fluid is pushed out of the chamber and into the system as the plunger moves toward it.
Plunger pumps can come with one or more plungers and sets of check valves. Where there are two, it is known as a duplex pump; where there are three, it is called a triplex pump; and where there are five, it is known as a quintuple pump. Triplex and quintuple versions are commonly used.
These pumps produce high pressures, and due to the reciprocating plunger they are also capable of producing pulsations, with the fewer plungers in the pump, the higher the pressure pulsations it is able to produce. Many systems include a pulsation dampener at the pump discharge that absorbs pulsations to significantly reduce the pressure pulsations further downstream.
As they can generate high levels of pressure and tend to be sturdily built, they are commonly used in applications where highly viscous or heavy fluids such as oil need to be moved. Smaller, lighter-duty versions are used in applications such as pressure washes.
Diaphragm pumps
Diaphragm pumps use a flexible diaphragm to create a vacuum at the chamber inlet to draw the fluid in, with the volume of the pumping chamber decreasing and forcing the fluid out of the discharge as the diaphragm moves in the opposite direction.
Like piston and plunger pumps, diaphragm pumps have check valves at the inlet and outlet of the pump to prevent the fluid from moving backward.
These pumps are highly reliable as they have no internal parts that rub against each other and contain no sealing or lubricating oils within the pump head which eliminates the chance of oil vapor leakage or contamination of the pumped fluid.
They are highly reliable because they do not include internal parts that rub against each other. They also contain no sealing or lubricating oils within the pumping head, meaning there is no chance of oil vapor leakage or contamination of the handled media