What is a Plunger Pump? | How does a Plunger Pump work?

A plunger pump is a famous type of 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.  It can produce high pressure than a piston pump. Therefore, it may use for high-pressure applications.

Piston and plunger pumps use a chamber that expands and constricts to suck and pressurize the fluid. Because these are reciprocating pumps, the chamber expands and constricts due to the reciprocating motion of the plunger (upward and downward; back and forth) instead of a circular (rotating) movement.

plunger pump

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.

Red also: Different types of Reciprocating Pumps

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 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 moves 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.

For better understanding, watch the below given video:

Read also: Different types of Pumps

Plunger Pump Construction materials

The materials used in the construction of the plunger pumps vary according to the application of the pump. The cylinder and housing materials must be strong enough to withstand the conditions of the adjacent operating environment. The material that comes into contact with the pumped medium must be resistant to corrosion by the liquid. The most common materials used for the construction of the pump are given below:

  • Cast iron has high scratch resistance, toughness and tensile strength, corresponding to a high nominal force.
  • Steels and stainless-steel alloys are also resistant to oxidation and chemicals. These materials have excellent tensile strength compared to plastics, comparable with higher pressure ratings.
  • 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 aluminium alloys.

What are the 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. Duplex pump
  2. Simplex pump
  3. Triplex plunger pump
  4. Multiplex pump

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. These pumps are used for hand pumps, hot oils, water jetting, steam pumps, and pump jacks etc. 

simplex plunger pump

2) Duplex Plunger Pump

As the name of the duplex pump represents that it has two cylinders for pressurizing the fluid.  Each cylinder contains a plunger.  These pumps use for applications such as bauxite Slurry, hot oil, coal slurry, drilling mud, cement, ore slurry and steam. 

duplex pumps

3) Triplex Plunger Pump

The triplex pump has three cylinders for the fluid compressoion. It has three plungers (one plunger for each cylinder).

triplex plunger pump

4) Multiplex Pump

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

Components of Plunger Pump

A plunger pump has the following major parts:

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

Plunger Pump components

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 discharging the fluid when it moves upward. It is made of steel, stainless steel or aluminium etc.

2) 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 into the cylinder.  As the plunger moves up, it reduces the area of the cylinder and pressurizes the fluid.

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) Seal

It is a high-pressure seal. It is a stationary component of the pump.

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 odour 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 and Disadvantages of Plunger Pump

A plunger pump has the following advantages and disadvantages: 

AdvantagesDisadvantages
These have the capability to generate more pressure than piston pumps.These pumps have high operation costs.
Flow rate and pressure changes have a very low
impact on the performance of the plunger pump.
This pump needs high maintenance costs.
These have the capability to pump abrasives and slurries.Plunger pumps can’t deliver pulsating free flow.
These have the capability to move high viscosity and heavy substances.These pumps can handle only low flow rate fluids.
They have self-priming capability.These are bulky and heavy.

Difference between Piston Pump and Plunger Pump

Plunger PumpPiston Pump
It has a fixed high-pressure seal.It has a high-pressure seal that moves inside the cylinder.
Inlet design pressure of 60psi to 70psiInlet design pressure of 8.5-40psi.
It produces high pressure than a piston pump.Produces less pressure than a plunger pump.
Output pressure is 100psi-10,000psiOutput pressure is between 100psi to 1200psi
It also provides pulsating flow.It delivers pulsating flow.
This pump can produce pressure up to 200MPa.It can produce pressure up to 150 MPa.

FAQ Section

What is a plunger pump used for?

A plunger pump uses to create high pressure for liquid transfer from one place to another.

What is the difference between Plunger Pump and Piston Pump?

The working of a plunger pump is very similar to the piston pump. The major difference is that a plunger pump uses a plunger for fluid transfer instead of a piston.

What are the types of Plunger Pumps?

The major types of the plunger pumps are given below:

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

Do you Know:

  1. What are different types of Pumps?
  2. How does a Centrifugal Pump work?
  3. How does a Condensate Pump work?

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