Positive Displacement Pump Types:And Functions


The positive displacement pump types are can in very little amount of suction forces and in high pressure the positive displacement pump types can expand. Other name constant volume pumps for positive displacement pump types.

Positive displacement pump can be divided in three sections. They are,

Reciprocating pumps classified in three sections they are,

  • Piston pump
  • Plunger pump
  • Diaphragm pump

Rotary pumps classified in three sections they are,

  • Screw
  • Gear
  • Rotary vane
Positive displacement pump types

Linear pumps classified in three sections they are,

  • Peristaltic pump
  • Chain pump
  • Rope pump
positive displacement pump types
Positive displacement pump types Image Credit – Wikimedia Commons

Reciprocating pump:

In the reciprocating displacement pump a part named reciprocating is present and with the help of pump water is lifted. In reciprocating pump the components are attached in it name are valves, exit valve and inlet valve. When the liquid is suction into the pump that time the inlet valve stays open but the exit valve remain close in the other way when the liquid is discharge that time the exit valve is open but the inlet valve remain close.

The reciprocating positive displacement pumps contain one simple or more than one (Quad) cylinder. Most of reciprocating positive displacement pumps number of contains cylinder is double or triple.

The power can be generated manually which is driven by air or steam or by engine that can be driven by belt.

With this reciprocating pump displacement pump heavy viscous liquid such as oil, concrete can lifted to desired place. Where low rate of flow is needed for the high resistance fluid there also this reciprocating pumps are used.

In reciprocating pump the increasing vacuum is present in the end portion of the suction and decreasing vacuum is present in the end portion of the delivery. When the vacuum present in the pump start to expand, fluid start to moves inside of the vacuum in the same way when the vacuum present in the pump start to reduce, fluid start to discharge.

The working principle of the reciprocating pump then we can noticed that when plunger is move toward the direction of right then amount of pump vacuum is increases inside and in this condition fluid is suck . Now when plunger is move toward the direction of left then present fluid inside the pump is pressurized and delivery valve is open at that time and inside fluid is flow out from the vacuum.

Reciprocating pump
Reciprocating pump
Image Credit – Wikimedia Commons

Reciprocating valve classified in purpose of working of piston in two categorized. They are,

Single acting of the reciprocating pump:

In this type of pump only one direction motion is act. Means if suction is happening inside the pump then discharge and piston act in other motion of direction for this reason it is called single acting reciprocating pump.

Double acting of the reciprocating pump:

In this type of pump both direction motion is act at a time. Means if suction is happening inside the pump then discharge and piston can act in same motion of direction for this reason it is called double acting reciprocating pump.

Rotary pump:

One of the most used positive displacement pump type is rotary positive displacement pump. Inside the rotary positive displacement pump a rotary is present to lifted liquid by the help of the pump. Inside the rotary the liquid is moves in rotation motion and the liquid can go through from storage tank to delivery pipe.

Rotary pump
Image Credit – Wikimedia Commons

Linear pump:

The linear pump is one of the most used positive displacement pump. By the help of the tubing the waves are moved of the contraction into liquid. Individual reciprocating parts are continuously compressed in the flexible tubing’s straight parts for moves liquid.The liquid is moves in a direction of linear or straight. In any stationary location the linear pump can be situated. This pump cannot be used in crowded area. The main problem with this linear positive displacement pump is volume and noisy. 

The most used linear pumps are chain pump and rope pump. The application of this pump is in medical, environment, decentralized wastewater treatment, pond aeration and many others.

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Non positive displacement pumps types:

The non positive displacement pump can be defined as the discharge flow rate for a liquid substance in the pump cab be changed depend upon the amount of pressure is applied in the outlet of the pump.

Non positive displacement types are categorized in some sections their names are given below,

Gear pumps:

In the gear positive displacement pump gear is present to moves the liquid substance and liquid is lifted by pump. By the gears of the gear positive displacement pump fluid pressure can be increases.

Gear pump
Gear pump
Image Credit – Wikipedia

In this pump two gears are used to generate the process. One gear is driver which is also known as driver and another one is driven which is known as idler gear.

The liquid substance is goes between the gears the fluid is trapped.  The gears when start to move the liquid substance is moves in a motion inside the gear from suction to end section of discharge suction. The pressure is increases and liquid substance is transform to the particular specified location.

The power gear connects to the shaft with the help of electric motor. The motor is started to rotate and power in generated and by the shaft power is supplied. After that when shaft starts to rotate the motion helps to rotating the idler gear. The power gear and idler gear rotate in the opposite direction to each other.

Vacuum is generating when the both gear start to rotate at the end section of the section side and by the suction valve fluid is suck.

Peristaltic hose pumps:

The peristaltic hose pump cannot use in the domestic purpose. It is so much noisy. The equipment inside the peristaltic hose positive displacement pump is rollers, rotor and flexible tube. This is also used in agriculture, water treatment and medicals.

Peristaltic hose pump
Peristaltic hose pump
Image Credit – Wikipedia

Progressive cavity pumps or helical pumps:

In this type of positive displacement pump the helical rotor is placed and pump is used to lift the water.

The components are carried by the helical pumps are rotor, rubber stator. The helical rotor is rotate inside the helical stator and water is pumped by the cavities.

Piston pumps:

In the piston pump the piston which is placed inside the piston is moves and sucks the liquid which is present in pressurized situation. The piston in the piston positive displacement pump produce vacuum inside the cylinder and liquid is suck into the cylinder by the piston in the stroke of the 1st. After the 1st stroke while the 2nd stroke is acted outlet valve open and pressurized liquid is present in the cylinder that time suction valve remain close while piston is moves inside.

Hand pump and bicycle pump are the common examples of the piston positive displacement pump. Another type of the pump is double acting pump.

Diaphragm pumps:

The diaphragm is used inside the diaphragm positive displacement pump and pump is used to lifting the liquid. Expanding of the membrane of the diaphragm increases the volume of the cylinder and liquid is sucks in another process decreasing of the membrane of the diaphragm decreases the volume of the cylinder and liquid is drain.

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Rotary positive displacement pumps types:

It works in the action of rotating motion of gears that can be goes in the backward or forward motion.

The rotary positive displacement pumps can be classified in general three sections. They are,

Variable displacement pumps types:

It can be explained as the pump which converts the energy mechanical to hydraulic. In a day’s variable positive displacement pumps are used in a wide range in the industrial areas.

The variable positive displacement pumps are classified in two sections. They are,

  • Vane pump
  • Piston pump

Indrani Banerjee

Hi..I am Indrani Banerjee. I completed my bachelor's degree in mechanical engineering. I am an enthusiastic person and I am a person who is positive about every aspect of life. I like to read Books and listen to music. Let's connect through LinkedIn-https://www.linkedin.com/in/indrani-banerjee-2487b4214

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