What is Plunger Pump? | What are the Types of Plunger Pumps?

What is a Plunger Pump?

A plunger pump is a reciprocating pump with a fixed high-pressure seal and a smooth cylindrical plunger that slides over the seal. These two features of the plunge pump make it different from the piston pump.

This pump can produce high pressure than a piston pump. Therefore, it may use for high-pressure applications.

Plunger Pump

The plunger pump and piston pump use contracting and expanding cavities to move fluids. Specifically, they are reciprocating pumps, which have cavities that expand and contract in a reciprocating (back and forth; up and down) motion rather than a circular (rotary) motion. 

A plunger pump is also known as high viscosity pump, high-pressure pump, or high-pressure pump because they provide a high pumping pressure. These pumps can also pump both solid and viscous media. These reciprocating pumps use for pumping industrial and municipal wastewater.

Working of Plunger Pump

A plunger pump has a stationary seal inside the stuffing box instead of a piston. The connecting rod, crankshaft, and plunger are the major components of the plunger pump.

Plunger Pump Working

A plunger pump works in the following way:

  • The plunger of the pump is connected with the crankshaft via a connecting rod. This crankshaft further connects with an electric motor.
  • As the motor provides power to the crankshaft, it converts the rotary motion of the motor into a reciprocating motion. The crankshaft further delivers this power to the plunger via a connecting rod.
  • When the plunger gets reciprocating motion, it starts moving upward and downward inside the cylinder.
  • As the plunger starts moving downward, a vacuum produces inside the pump chamber. Due to this vacuum, a pressure difference produces between the external fluid pressure and the cylinder’s internal fluid pressure.
  • After this, the plunger sucks fluid into the chamber. When it sucks the fluid according to the requirements, the suction valve closes, and the plunger starts moving upward.
  • As the plunger moves upward, the volume of the chamber decreases, and fluid pressurizes.
  • When the internal fluid pressure becomes higher than the delivery tank pressure, the outlet valve opens, and fluid delivers into the delivery tank or other desired location.

Plunger Pump Construction Materials

The materials used to construct the plunger pumps vary according to the application of the pump.

The casing and cylinder materials must have sufficient strength and must hold up adjacent to the operating environment conditions. Materials to get in touch with the pumped media require to resistant for any rust-induced with the liquid.

The materials used in the construction of plunger pumps are discussed below.

  • Stainless steel alloys and steel give safety against rust and chemical, and they have superior tensile powers compared with plastics, equivalent to superior pressure ratings.
  • Cast iron has high scratch resistance, toughness, and tensile strength, corresponding to a high nominal force.
  • Plastic materials are inexpensive and have a wide range of resistance to chemical and rust attacks.
  • Other types of materials used in pump construction mainly include nickel, ceramic, bronze, brass, and aluminum alloys.

Types of Plunger Pumps

The number of cylinders describes the power of the pump. The higher the number of cylinders, the higher will be the fluid pressure.

According to the number of cylinders, the plunger pump has three major types:

1) Simplex Pump

This pump uses only one cylinder for the pressurization of fluid. It also has only one plunger that moves in the cylinder.

simplex pump

2) Duplex Pump

The name of the duplex pump represents that it has two cylinders for pressurizing the fluid. Each cylinder contains a plunger.

duplex pump

3) Multiplex Pump

It has three or more cylinders for the pressurization of the fluid. This plunger pump contains more than two plungers.

triplex plunger pump

Components of Plunger Pump

A plunger pump has the following major components:

  1. Plunger
  2. Suction Valve
  3. Discharge Valve
  4. Cylinder
  5. Seal

1) Plunger

A plunger is a solid component of the pump that reciprocates inside the cylinder. It helps the pump to suck and discharge the fluid. When it moves downward, it sucks fluid inside the pump while it discharges the fluid when it moves upward. It is made of steel, stainless steel or aluminum, etc.

2) Seal

It is a high-pressure seal. It is a stationary component.

3) Inlet Valve

This valve uses to suck the fluid from outside into the cylinder. It is a one-way valve so that fluid can’t go back.

4) Outlet Valve

It is also a one-way valve. The outlet valve uses to discharge the fluid from the pump.

5) Cylinder

A cylinder is also known as a compression chamber. The plunger moves up and down in the cylinder.

As the plunger produces a cavity inside the cylinder, the external fluid starts entering the cylinder. As the plunger moves up, it reduces the area of the cylinder and pressurizes the fluid.

Applications Of Plunger Pumps

The plunger pump has the ability to transfer viscosity liquids and heavy substances. They have the ability to pump fluid with high pressure. Therefore, these pumps are employed for the below given major applications:

  • The plunger pumps use to pump municipal wastewater
  • They used for pressure testing
  • They operate to inject chemical
  • Used for coal liquefaction
  • Used for cleaning services
  • The plunger pump also uses for urea production
  • They also use to control smell and misting
  • They utilize for surface preparation and dehydration of gas
  • These pumps are also used for water cutting and drill cutting injection
  • Used in oil and gas production

Advantages Of Plunger Pump

  • The plunger pumps have a self-priming capacity.
  • These are highly efficient pumps.
  • These pumps don’t require initial priming.
  • The plunger pumps have the capacity to generate very high pressure. Therefore, they are best suitable for high-pressure applications.
  • In the case of variable speed, it has the capability to control linear capacity.
  • The leakage issues of this pump can be fixed without stopping the operation of the pump.
  • This pump produces more pressure than a piston pump.
  • The pump performance doesn’t affect highly due to changes in the pressure and flow rate.
  • They can easily pump heavy substances and high viscosity fluids.
  • They can easily transfer the abrasives and slurries.             

Disadvantages Of Plunger Pump

  • The plunger pumps have more moving parts than the axial or centrifugal pumps.
  • They have low flow rate than the axial or centrifugal pumps.
  • They don’t have the capability to deliver pulsating free flow.
  • It requires high maintenance and installation costs.
  • This pump has many reciprocating parts. Due to the motion of these parts, they generate extreme vibration.
  • The operating cost of this pump is very high.
  • The plunger pump can only control the low flow rate of liquids.
  • These are heavy pumps.
  • They are bulky.

Differences Between Piston Pump and Plunger Pump

Piston PumpPlunger Pump
The piston pump uses a piston to pump the fluid.The plunger pump uses a plunger to pump the fluid.
It has a high-pressure reciprocating seal that moves forward and backward with a piston inside the cylinder.It has a fixed high-pressure seal.
The pressure of the inlet is from 8.5psi to 40psi.The pressure of the inlet is from 60psi to 70psi.
The pressure of the outlet design is from 100 psi to 1200psiThe pressure of the outlet design is from 100psi to 10,000psi
Force piston pump, lift piston pump, radial piston pump, and axial piston pump are the types of piston pumps.Duplex pump, simplex pump, and multiplex pump are the types of plunger pumps.
These pumps can’t generate as high pressure as plunger pumps.They generate very high pressure.

FAQ Section

Where is the plunger pump used?

Plunger pumps can be found as reliable high-pressure pumps in many industrial applications, for example, in cleaning applications or in process technology in the chemical industry.

What is the function of a Plunger Pump?

Plunger pumps are pumps in which the plunger slides back and forth within a stuffing box, increasing and decreasing the working volume. The plunger of these pumps forces the liquids through a set of valves. Plunger pumps are more suited for higher pressures.

What is a plunger in mechanical?

Plungers are mechanical components for positioning and fixing workpieces. A spring is built into the main body so that the ball or pin at the tip sinks into the body when a load is applied and is returned to its former position by spring force when the load is removed.

What is a compressor plunger?

A long-cemented carbide tool used to produce low-density polyethylene (LDPE) and ethylene-vinyl acetate (EVA) in a petrochemical plant. This product is used as a piston in a high-pressure compressor and requires high compressive strength, wear resistance, and corrosion resistance.

What are the types of Plunger Pumps?

  1. Duplex Pump
  2. Simplex Pump
  3. Multiplex Pump

What is a triplex pump?

A triplex piston pump is a reciprocating positive displacement pump that uses only three pistons. This type of pump is often used for high-pressure applications, e.g., hydraulic systems. Due to its robust design, it is capable of pumping high viscosity fluids and fluids which contain solids.

What is a HEXAPLEX Pump?

The HEXAPLEX pump is a six plunger pump that can give very high pressure. These pumps are well engineered to give the best results according to the industry’s expectations.

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