What is Plunger Pump and How Does It Work?

What is Plunger Pump?

A plunger pump is a type of positive displacement pump in which the high-pressure seal is stationary and a smooth cylindrical plunger slides through the seal. This distinguishes them from piston pumps and allows them to be used at higher pressures. This type of pump is often used to pump municipal and industrial wastewater.

Piston pumps, sometimes referred to as piston pumps, have a reciprocating plunger that moves back and forth, forcing fluid through a series of valves. Some simple examples from our everyday life could be a bicycle pump, a spray bottle, or a squirt gun.

Commercially, plunger pumps are commonly used in cleaning, disinfection, pest control, agriculture, and other applications in their electrically powered equipment such as pressure washers, atomizers, and sprayers.

The invention of the plunger pump is attributed to Samuel Morland based on a patent of 1675.

How does Plunger Pump Work?

Piston pump and 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 actuator.

Rotary piston and plunger pumps use a crank mechanism to create a reciprocating motion along an axis, which then builds pressure in a cylinder or power cylinder to force gas or liquid through the pump. The pressure in the chamber operates the valves at both the suction and discharge points.

Piston pumps are used in applications that can range from 70 to 2,070 bar (1,000 to 30,000 psi). Piston pumps are used in low-pressure applications. The volume of fluid discharged is equal to the area of ​​the plunger or piston times its stroke length.

The overall performance of piston pumps and plunger pumps can be calculated from the area of ​​the piston or plunger, the stroke length, the number of pistons or plungers, and the speed of the drive. The power required by the drive is proportional to the pressure and capacity of the pump.

Seals are an essential part of piston pumps and plunger pumps to separate the drive fluid from the fluid handled. A gland or packing is used to seal the connection between the container in which the medium is being transferred and the plunger or piston. A stuffing box can consist of bushings, packing or sealing rings, and stuffing boxes.

The component materials of plunger pumps are selected for wear and contact with the type of medium. Component materials include bronze, brass, steel, stainless steel, iron, nickel alloy, or other materials. For example, plunger pumps used in general service or oil service applications often have an iron cylinder and plunger.

The piston, discharge valves, and suction valves come into contact with the medium being transferred, and the material selection is based on the liquid being transferred. In performance applications where continuous duty plunger pumps are required, all-ceramic plungers can be used when in contact with water and oil, but may not be suitable for use with highly acidic media types.

Differences Between Piston and Plunger Pumps:

Piston Pump	Plunger Pump
A high-pressure seal reciprocates with the piston in the cylinder	The high-pressure seal is stationary. Plunger slides through seal allowing the pump to be used at higher pressures.
Inlet Design Pressure of 8.5psi to 40psi	Inlet design pressure of 60-70psi
Best suited to short duty cycles unless larger pump running slowly	OK for continuous operation when running slowly
Inlet valves mechanically actuated	Requires flooded suction or higher inlet pressure supplied by a booster pump
Output pressure 100-1200psi	Output pressure 100 to 10,000psi

Applications of Plunger Pumps

The plunger pumps have the capability to deliver high pressure. These pumps have the capability to pump heavy substances and high viscous fluids. Due to these features, plunger pumps use for the following applications:

• These pumps use for chemical Injection.
• These pumps also use for odor control and misting
• A plunger pump uses for drill cutting injection
• Use for water cutting
• Use in oil and gas production
• The plunger pumps also use for gas dehydration
• They use for surface preparation
• Plunger pumps also use for urea production
• They use for cleaning applications
• These pumps use for coal liquefaction
• These are used for pressure testing

Advantages of Plunger pump

• It has self-priming capability (self-priming pump) and high efficiency.
• Very high developed/discharge pressure is possible
• Linear capacity control if you are using variable speed
• Leak can be mitigated without shutting down the pump if your company permit you to tighten the packing while the pump is running
• These have the capability to generate more pressure than piston pumps.              
• Flow rate and pressure changes have a very low
• Impact on the performance of the plunger pump.             
• These have the capability to pump abrasives and slurries.             
• These have the capability to move high viscosity and heavy substances.  

Disadvantages of Plunger pump

• Very low flow when compared to centrifugal or axial pump
• Irregular flow cause pulsation
• Prone to cavitation because of acceleration head, especially if the suction pipe is long
• Inherently higher vibration because of reciprocating motion, although the rotational speed is generally lower than dynamic pumps
• These pumps have high operation costs.
• This pump needs high maintenance costs.
• Plunger pumps can’t deliver pulsating free flow.
• These pumps can handle only low flow rate fluids.
• These are bulky and heavy.

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