Difference Between Reciprocating and Rotary Pump

Reciprocating vs Rotary Pump

Reciprocating and rotary pumps are two types of positive displacement pumps. Essentially, positive displacement pumps enable the movement of fluid from one side of the pump to another using a rotational motion. They are also called constant flow machines because, theoretically speaking, they produce the same flow regardless of the discharge pressure.

Reciprocating and rotary pumps refer to the mechanism used in each type of pump that moves the fluid. In both types of pumps, there is an expanding cavity on the suction side and a decreasing cavity on the discharge side. The volume of liquid is constant in both cases.

In a reciprocating pump, the fluid flows back and forth propelled by a mobile object, usually a piston or diaphragm. The liquid is released when the piston or diaphragm moves. On the other hand, a rotary pump uses one part or several parts to move the fluid in a circular fashion. In each revolution of the pump, the liquid is discharged away from the pump.
A reciprocating pump has a valve which serves as the entrance for the liquid. The valve traps the liquid inside and directs the liquid to a certain area.  A rotary pump, meanwhile, has no valves.

Reciprocating pumps can discharge high-pressure fluids in small intervals. On the other hand, the fluid pressure in a rotary pump needs to be adjusted depending on the amount of fluid. In some instances, there might be a need for a regulator to contain the pressure.

The released liquid from a reciprocating pump has a pulsating manner while the rotary pumps results in a smooth flow of the liquid from the discharge side of the pump.

Reciprocating pumps are divided into three generic classifications based on the number of slides in contact with the liquid and the number of cylinders in the pump. Some examples of reciprocating pumps are plunger pumps, diaphragm pumps, piston displacement pumps, and radial piston pumps. Rotary pumps also have several varieties; gear pumps, screw pumps, rotary vane pumps, and lobe pumps among them.

Rotary pumps are ideal in displacing viscous liquids while reciprocating pumps can handle only viscous liquids.

Rotary pumps are often small, but their size is not a measurement of their efficiency. Rotary pumps are, in fact, very efficient and reliable as they remove air from the lines naturally. Reciprocating pumps are bulkier compared to rotary pumps.

Summary:

1. Positive displacement pumps make it possible for fluid to move from one side to the other side in a rotating fashion. Positive displacement pumps are also called constant flow machines.
2. Both reciprocating pumps and rotary pumps are types of positive displacement pumps. They both use a rotating motion to gain and displace fluids. The designs of both pumps include a large receiving orifice for the suction side and a smaller orifice for the discharge side. In both types of pumps, the volume of liquid is fixed.
3. Reciprocating pumps displace liquid by a backward and forward motion. This motion is in one direction, usually caused by a piston or diaphragm. On the other hand, rotary pumps use a part or parts to make a liquid rotate and displace it after one revolution.
4. Reciprocating pumps can discharge high-pressured liquids in small quantities while rotary pumps need to adjust the fluid pressure.
5. Reciprocating pumps are classified according to the number of slides in contact with the liquid and the number of cylinders in the pump. Plunger pumps, diaphragm pumps, piston displacement pumps, and radial piston pumps are types of reciprocating pumps. Gear pumps, screw pumps, rotary vane pumps, and lobe pumps are some examples of rotary pumps.
6. Reciprocating pumps are bulky; rotary pumps are smaller but highly efficient.

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