Piston or Plunger Pumps are reciprocating pumps that use a plunger or piston to move media through a cylindrical chamber. The plunger or piston is actuated by a steam powered, pneumatic, hydraulic, or electric drive. Piston pumps and plunger pumps are also called well service or high viscosity pumps.
How do piston pumps work?
Piston pumps or plunger pumps use a cylindrical mechanism to create a reciprocating motion along an axis, which then builds pressure in a cylinder or working barrel to force gas or fluid through the pump.
The pressure in the chamber actuates the valves at both the suction and discharge points.
Plunger pumps are used in applications that could range from 70 to 2070 bars. Piston pumps are used in lower pressure applications.
The volume of the fluid discharged is equal to the area of the plunger or piston. The capacity of the piston pumps and plunger pumps can be calculated with the area of the piston or plunger, the number of pistons or plungers, the displacement of the stroke, and the speed of the drive. The power from the drive is proportional to the capacity of the pump.Seals are an integral part of piston pumps and plunger pumps to separate the power fluid from the media that is being pumped.
A stuffing box or packing is used to seal the joint between the vessel where the media is transferred and the plunger or piston. A stuffing box may be composed of bushings, packing or seal rings, and a gland. Piston pumps and plunger pumps have a number of components that require the choice of materials based upon wear considerations and contact with the media type. Components may have a number of materials used including bronze, brass, steel, stainless steel, iron, nickel alloy, or other material. For example, piston pumps that function in general service or oil service applications may have an iron cylinder and piston with a steel piston rod. The plunger, discharge valves, and suction valves come in contact with the media type transferred; material choices should be considered based on the fluid transferred.
In power applications where continuous duty piston pumps and plunger pumps are needed, solid ceramic plungers may be used when in contact with water and oil, but may not be the appropriate choice for use with highly acidic media types. The difference between piston pumps and plunger pumps as compared to rotary piston pump is the actual mechanism used to transfer the fluid. The piston elements moving along an axis are called axial piston pumps. Rotary piston pumps typically have an internal rotating mechanism that moves the piston.