Centrifugal Pump Working Principle

Centrifugal pump is one kind of the dynamic pump type. This pump is pushing the fluid in a perpendicular direction to the impeller shaft/axis. Different from the axial pump which the fluid output direction is parallel to the axis of the impeller.

Centrifugal pump is composed of an impeller with inlet channel right in the middle. Centrifugal pump impeller have different design with axial pump impeller. Centrifugal pump impeller will create a centrifugal force to push the fluid from the center of the pump (inlet) to the outside of impeller. So, when the impeller rotates by mechanical energy generated by the driving source, fluid flows from the inlet to the outer side of the impeller ahead to the pump casing.



One elementary part of centrifugal pump other than impeller is the pump casing. Centrifugal pump casing have unique design like a snail shell. This snail-shell-shape have function to decreases the fluid flow velocity while impeller rotation speed remains high. The fluid velocity is converted into pressure by this casing so that the fluid can reach its outlet point.

Centrifugal pump has some advantages include smooth operation in pumps, uniform pressure at pump discharge, low cost, and can work at high speeds so that further applications can be connected directly with steam turbines, electric motors, or other driving source. The use of centrifugal pumps in the world reaches 80% because of its suitable use to cope with large amounts of fluid than positive-displacement pumps.

How to Control the Flow of Centrifugal Pump System

Centrifugal pumps become one of the most widely used in the industrial world. Here are some reasons:

  • Strong construction
  • Simple design
  • Low fabrication costs
  • Easy operation
  • Easy-to-manage system controls

The working principle of a centrifugal pump is by transfer of motion energy from the rotation of the driving shaft to the pump impeller thus creating the centrifugal energy transferred to the fluid flowing within it. The flow of centrifugal pump output can be varied both head and discharge values, according to system requirements. Because sometimes the system does not always want the fluid flow always constant at a certain value. This is not possible with positive displacement pumps.

One example is the Boiler Feed Water Pump used in steam power plants. This pump supplies the amount of discharge water flow adjusted to the existing electrical load.

Here are ways to adjust the discharge flow and head output of a centrifugal pump:

Controlling Flow Discharge With Discharge Control Valve

The simplest way to vary the discharge of the pump fluid flow is to use a control valve that can be adjusted for the amount of openings and mounted on the output side of the pump.

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The purpose of using the control valve at the pump outlet is to increase the restriction of the existing fluid flow, so that there is a shift in the system characteristic curve upwards. If the pump operates at a constant rotation, the pump operational point shifts to the pump characteristics curve line toward the lower flow rate.

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The sliding of the system characteristic curve results in the decrease of the system discharge requirement as desired. But on the other hand the need for system head (downstream control valve) actually does not change lower. This results in an excess head or leftover head compensated by a throttling valve system that creates pressure drop.

Advantages:

  • Cheap price
  • Good use on system with load often 100%
  • Good to use on short time operational control
  • It is suitable for pumps with flat characteristic curves

Disadvantages:

  • The pump output pressure is too high
  • The pump efficiency becomes low if it is throttling position
  • Not energy efficient if being throttling position
  • The control system is not good if the excess head is high
  • There is a mechanical load on the valve when throttling position
  • There is a risk of making noise when it is high throttling position

Controlling Flow With Minimum Flow Control Valve

The minimum flow is a line attached parallel to the pump and connects directly or indirectly between the output side of the pump and the inlet side of the pump. In this system the fluid flow of the pump output is divided into two, one direction fixed to the system while the other returns to the inlet side of the pump. In this way we can adjust the flow of fluid into the system by regulating the amount of fluid that passes through the minimum flow, of course with the help of the control valve.

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Through the pump and system characteristics curve we can note that in this way, we can adjust the discharge pump output to the system without having change the pump head value at its operational point. So the excess head value is not as big as if the system only uses the throttling system on the pump output side.

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Advantages:

  • There is no increase in head even if the pump works on partial load.
  • The value of the pump’s output pressure is fixed even if the flow discharge varies.
  • Suitable for use in systems that require low head but high flow.
  • Easy to control if full pump load is required.

Disadvantages:

  • The cost of system construction is more expensive.
  • There is no decrease in power requirements at partial load.
  • There is still an excess head at partial load.
  • In terms of energy needs, this system is not economical.

Controlling Flow With Variation of Speed Rotation

One way to get variation of the flow discharge of centrifugal pump is by varying the speed of the pump rotation. If the pump rotation is changed, the pump characteristic curve will shifted. When the rotation is faster, the curve will shift to the right. Whereas if the rotation is slower, then the curve will shift to the left. The curve shift is parallel to the initial position, so the head and flow rate at each curve point may vary according to the variation of the speed rotation used.

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There are several ways we can use to control the pump in order to have a speed rotation variation:

  1. Using an electric motor that can vary its rotational speed. AC electric motors can be varied in rotational speed by using more magnetic poles on the rotor side. This will increase the cost of production. While on the DC electric motor, simply by changing the volume of the supply voltage so that it can vary the magnitude of rotation.
  2. Using a gearbox system.
  3. Using a belt transmission system with a variable pitch diameter.
  4. Using a hydraulic transmission system.
  5. Using a steam turbine as a rotating driver can be adjusted by adjusting the amount of steam that enters the turbine to move the blades.


Advantages:

  • Can avoid excess head.
  • Smooth pump ignition due to speed inverter.
  • The pump components will last longer.
  • Reduce the effect of hydraulic feed-back.
  • Energy saving.
  • Low electrical load (if using an electric motor) due to the large current low when the pump is turned on.
  • Reduce maintenance costs.

Disadvantages:

  • The cost of the control system is high.

Controlling Flow By Installing Multiple Pumps In Parallel

If several centrifugal pumps are installed in parallel, then the total discharge flow is the sum of the flow rate of all pumps at work. In this way, we can adjust the fluid flow by running a number of pumps simultaneously in accordance with system requirements. The characteristic curve of the pump and the system becomes the reference work for each pump.

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Parallel pump characteristic curve is obtained by summing the fluid flow from several pumps at the same head value. In practice, higher flow rate will also increase the resistance of the system. So, to compensate these obstacles, the operating point of the pump becomes a higher practical pressure value than its theoretical pressure value.

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Advantages:

  • It is suitable for system curve characteristic which has high static head component.
  • Good adaptation on partial load.
  • High system efficiency.
  • Low cost control on the operating system.
  • Reliable operational system.

Disadvantages:

  • Construction costs are high.
  • The operational switching frequency of the pump is high if the system design is not appropriate.
  • Problem with fluctuation of pump inlet pressure.

Axial Pump Working Principle

An axial pump is one kind of the dynamic pump type. This pump serves to push the working fluid in a direction parallel to the axis/shaft impeller. Different from the centrifugal pump which the fluid output direction is perpendicular to the axis of the impeller.

The mechanical energy generated by the driving source is transmitted through the impeller shaft to drive the pump impeller. The impeller rotation gives the axial force to drives the fluid and produce kinetic energy. In some axial pump designs, there is mounted blades at the stator side, forming a diffuser at the pump outlet. Its function is to remove the rotating effect of the working fluid and to convert the kinetic energy contained, into working pressure.

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Axial pumps are used on systems that require high fluid flow discharge, with low head requirement. This type of pump is widely used in irrigation systems, flood prevention pumps, and in steam power plants are used to supply seawater as a cooling medium in condensers.

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Centrifugal vs Axial Pumps Characteristic Curves



Here are some comparison between axial pump with centrifugal pump:

  • As seen from the efficiency curves, centrifugal and axial pumps have almost the same maximum efficiency levels.
  • If the fluid flow decrease, the input power for the centrifugal pump becomes decrease too. But at the axial pump the input power goes up to maximum when the fluid flow stops.
  • The axial pump may cause overload at the motor drive if the flow rate is drastically reduced from its design capacity.
  • Head generated by centrifugal pumps are much higher than axial pumps.
  • On an efficiency curve beyond its maximum efficiency, the axial pump has a lower efficiency level than a centrifugal pump.

How To Read The Pump And System Characteristic Curve

Theoretical explanation of the pump characteristics curve, you may read the previous article. The pump characteristic curve is influenced by the size and design of the pump, the size of the impeller diameter, as well as the magnitude of the operating rotation. The characteristics of a pump are shown through a head vs flow pump. On this curve also included some information about the associated pump such as BHP, NPSHR, hydraulic efficiency point, and pump power characteristics.

Now lets talk about the system characteristic curve. The system characteristic curve is used to determine which centrifugal pumps will be installed on the system. A fluid flow system can generally be described in a characteristic curve called the system characteristic curve.

Kurva Karakteristik Sistem Aliran Fluida
Characteristic Curve of Fluid Flow System


Like the pump characteristics curve, the system characteristic curve is also the head on vertical axis and the flow at horizontal axis. The head of the system curve is a function of the static head of the system, and its losses. This can be expressed through the following equation:

h = dh + hl

Where:

h = head system
dh = head elevation system / height difference between system inlet and outlet
hl = the head loss of the system

If the loss of the head is greater, such as if the discharge valve system is throttled, will result an increased of head loss. Thus shifted the system characteristic curve upwards. At the start point of this curve, the system head value is not equal to zero, so even if there is no flow in the system the head is equal to the value on the curve.

Cara Memilih Pompa Sentrifugal
How to Select a Centrifugal Pump

 

To determine the exact centrifugal pump used on a system, the pump characteristics curve and system characteristic curves are combined. The meeting point between the two curves is an operational point if the associated pump used on the system. The most optimal operational point is if the meeting point between the two curves is in the BEP (Best Efficiency Point) area.

The pump operating point shall be kept to the highest pump efficiency area as far as possible. Especially the operation of the pump is used on systems that require head variation and large fluid flow, so there will be a shift in the system curve.

What is Pump Characteristic Curve?

Each pump made by the manufacturer has different characteristics in accordance with the function and design of the manufacturer. This pump characteristic curve is influenced by the size and design of the pump, the diameter of the impeller, as well as the speed of its operating rotation. Pump characteristics are shown through a head capacity vs discharge pump curve.

Kurva Performa Pompa
Head-Capacity Curve of Centrifugal Pump

The above characteristic curve of the pump is also known in engineering and industrial world as the Pump Performance Curve.

If a particular pump is kept constant in its rotation speed, then we can shift the performance curve by varying the size of the impeller diameter as below.

Variasi Diameter Impeller

Similarly, if we keep the pump impeller diameter in constant condition, then we vary the speed of the pump rotation, then we can also shift the pump performance curve to the right or left.

Variasi Kecepatan Putaran Pompa



The variation of pump conditions above does seem less prevalent. But in the industrial world it is a common thing. In Steam Power Plant for example, the main pump that supplies water to the boiler must be able to vary the discharge water flow in accordance with the needs of water vapor that will be produced by the boiler. Changes in electrical load then the need for water vapor is also different. The variation of pump rotation speed becomes a reasonable solution for use in this industry.

Additional Components of Pump Characteristics Curves

There are other things we need to know about some of the parameters that are usually included in the pump characteristics curve. The first is the Brake HorsePower (BHP) information required to operate the pump. BHP, also known as pure engine power, is a unit of power designation of a machine before it’s reduced by losses due to system design or other losses.

Informasi BHP Sebuah Pompa
BHP Information On Pump Characteristics Curve

Keep in mind that the BHP information on the pump characteristics curve is for a water fluid that has a specific gravity value = 1. If the pump will be used for another fluid, then the BHP value must be calculated first. For example the fluid to be used is gasoline with a specificity value of 0.72, then the required value of BHP is:

5 bhp x 0,72 = 3,6 bhp

Other information provided with the pump characteristics curve is usually the point of its hydraulic efficiency. Best Efficiency Point (BEP) / hydraulic efficiency is the pump efficiency that has been reduced by losses due to hydraulic effect.

Efisiensi Hidrolik
The Best Hydraulic Efficiency Shown On The Curve

The third parameter is Net Positive Suction Head Required (NPSHR). NPSHR is a pump parameter which the value was obtained from the lab test. The NPSHR is a quantity to indicate the losses of the internal pump. The magnitude is determined by the pump design, its size, and its rotational operation.

Contoh NPSHR
NPSHR Curve of a Pump


Large NPSHR is affected by the rotation speed of the pump when used on the system. While the pump rotation depends on the design of the system itself. Another case with NPSH whose value is directly influenced by system design. The actual NPSH (Net Positive Suction Head) value must always be higher than this NPSHR value.

The last information on the pump characteristics curve we need to consider is the ability of the pump to lift the water from the inlet side to the outlet. This term we know as the priming lift.

Priming Lift Information

On the curve above, the ability of the pump to lift water from a certain depth at each impeller diameter. This information is very important especially when we choose pump to be used on a deep system.

Axial Pump Components

The axial pump components are not much different from the centrifugal pump. The most noticeable difference is the diffuser design between the centrifugal pump and the axial pump. In accordance with the impeller design, centrifugal pumps are emphasized to generate high head fluid pressure, while axial pumps emphasize high flow fluids. For that, the diffuser design on the centrifugal pump (in this case is the volute casing) is more “extreme” when compared to the diffuser in the axial pump.

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Axial Pump Parts


Based on the image above, here are the main parts of the axial pump:

  1. Pump Inlet. This part becomes the inlet side of the fluid to get into the pump. In a vertical axial pump, the inlet side is funnel-shaped (so-called Suction Bell) in order to reduce the hydraulic head loss.
  2. Impeller. Impeller becomes the main part of this pump. The design is similar to a propeller on a ship. This impeller serves to induce an axial force which is transferred to the working fluid.
  3. Diffuser. The axial pump casing is also like a diffuser-shaped on centrifugal pump. Its function is to lowering the pump speed and raise the working pressure. However, the design is not as extreme as the volute casing of the centrifugal pump, because the increased outlet pressure of the axial pump outlet may cause vibration and reduce the working life of the axial pump. Once again, the main function of axial pump is to achieve high fluid flow, not high fluid pressure.


  4. Shaft. Serves to continue the rotation of the electric motor to the impeller.
  5. Guide Bearing. Serves to hold the position of the shaft to stay on the axis line work. These bearings require a lubrication system that must be maintained to avoid temperature rise.
  6. Stuffing Box. Is a sealing system that serves as a barrier between the shaft with the casing to avoid leakage.

Here is the detailed picture of axial pump parts:

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Parts of Pump Inlet Sides

 

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Parts of Drive-End Side of Pump

 

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Example of Installing a Vertical Axial Pump

 

(Source: fpipumpscanada.com)

Centrifugal Pump Components

Generally, centrifugal pump components are include:

  1. Casing
  2. Impeller
  3. Shaft
  4. Bearing
  5. Clutch
  6. Packing & Seal
  7. Lubrication System

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Pump Casing

The first major component of a centrifugal pump is the pump case. Centrifugal pump casing is designed in the form of a diffuser that surrounds the pump impeller. This diffuser is more commonly known as a volute casing. In accordance with the function diffuser, volute casing serves to reduce the flow rate of fluid into the pump. At the pump outlet, the volute casing is designed to form a funnel that convert kinetic energy into pressure by lowering the speed and raising the pressure, also helping the balance the hydraulic pressure on the pump shaft.

Volute Casing
Volute Casing

 

Impeller

Impeller is the rotating part of the centrifugal pump, which serves to transfer energy from the motor rotation to the pumped fluid by accelerating it from the center of the impeller to the outer side of the impeller.

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Some examples of impeller types

 



The impeller design depends on pressure requirements, flow velocity, and conformance with the system. Impeller becomes the main component affecting pump performance. Modification of impeller design will directly affect the shape of the pump characteristics curve. There are various designs of centrifugal pump impeller, including closed and open type, single flow type, mix flow type, radial type, non-clogging type, single stage type, and multi stage type.

Shaft

The pump shaft is the part that transmits the rotation of the source of motion, such as the electric motor, to the pump. What we need to note is that, on a centrifugal pump working at its best efficiency point, the bending force of the shaft will be perfectly distributed throughout the pump impeller part.

Bearing

Pump bearing is to hold (constrain) the position of the rotor relative to the stator in accordance with the type of bearing used. Journal bearing serves to withstand gravity and forces in the direction of that heavy force, and thrust bearings serves to resist the axial force that arises on the pump shaft relative to the pump stator.

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Journal and Thrust Bearing

 



Coupling

Basically the coupling serves to connect two shafts, one of which is the driving shaft and the other is the driven shaft. The coupling used in the pump depends on the system design and the pump itself. The various coupling used in the pump can be rigid coupling, flexible coupling, grid coupling, gear coupling, elastrometic coupling, and disc coupling.

Packing System

The packing system at the pump is to control the fluid leak that may occur on the border between the pumping part (spindle) and the stator. Sealing systems that are widely used in centrifugal pumps are mechanical seals and gland packing.

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Mechanical Seal System

 

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Gland Packing System

 

Lubrication System

The lubrication system at the pump serves to reduce the coefficient of friction between the two surfaces that meet, thus reducing the risk of wear. Lubrication at the pump is mainly used in bearings. The system can be either lub oil or greas type depending on the pump design itself.

Positive Displacement Pumps Classification

Positive displacement pump has more variation than dynamic pump. Generally it is divided into two large groups, rotary pump and reciprocating pump. Both are still divided into various types of pumps again. And here are the pumps:

  1. Positive Displacement Rotary Pump


    This rotary type moves the working fluid through a rotary mechanism by make a vacuum effect so it can suck the working fluid from the inlet side, and move it to the outlet side. If there is air trapped inside the rotary pump, it will naturally discharge the air, thereby reducing the need to vent the air trapped inside the pump manually.

    Here are all kinds of rotary pumps:

    • Internal Gear Pump

    This pump uses two gears as a working fluid driver inside the pump casing. One gear drives and the other becomes driven. The driving gear is inside the driven gear. For more details please see the following picture.

     

    Internal Gear Pump

    And here is the process whereby the working fluid is pumped by this internal gear pump.

     

    Internal Gear Pump Working Principle

    The working fluid enters through the pump inlet toward the outer gear rotated by the inner gear. The fluid moves toward the outlet side as a result of the drive from the outer gear. Furthermore the inner gear goes into the sidelines of the outer gear to push the working fluid to exit through the outlet side of the pump.

    • External Gear Pump

    Same with the internal gear pump, this external gear pump –or typically called gear pump–  also uses two gears as its main component. What distinguishes is that both gears are in parallel positions, and the driving gear is not inside the driven gear.

     

    Gear Pump
    • Screw Pump

    Screw pump was first developed by Archimedes. This why a screw pump also called Archimedes Screw Pump. Single screw rotor was used to move water from the river at lower point to the rice fields for irrigation purposes.

     

    Screw Pump

    The screw pump design has evolved into several types such as twin-rotor, triple-rotor, and 5-rotor. The differences is in the number of the screw. Here is a screw pump video with twin-rotor.

    The working principle of screw pump with multi-rotor is when working fluid entering through the inlet side of the pump, moved by the rotor screw through the sidelines of the outer side. Upon reaching the outlet side, the fluid will be pushed out of the pump.

    • Progressive Cavity Pump

    This type of pump is the development of a screw type pump. The working principle was first introduced by Rene Moineau in the 1930s. The pump consists of both helical rotor and stator, but the stator designed to have a spiral pitch distance which is 2 times larger than the pitch of the rotor. The progressive cavity pump rotor is connected to the shaft driven by an electric motor. Among the shafts with the rotor is connected by flexible coupling which when the shaft rotates, this clutch moves to follow the movement of the rotor and shaft. For more details please note the following animation.

    Progressive Cavity Pump (Source: Wikipedia)

    Spiral design of the rotor and stator form a cavity (cavities) in it, which is when the rotor cavity as if it moved toward the pump outlet. This space is the space to move the working fluid.

     

    Progressive Cavity Pump Parts

    Progressive cavity pumps can be used in various types of working fluids, from dilute fluids to high-viscosity fluids. However, this pump does not match the solid particles. For operational purposes, this pump needs to be carried out a priming process as well as discharge of air trapped (venting) in it before operating. It aims to extend the life of the pump.

    • Rotary Lobe Pump and Rotary Piston Pump

    The rotary lobe pump is similar to a gear pump, it’s just using a kind of lobe-shaped rotor. There are two lobe rotor inside the pump casing, which are both driven by a driving source and arranged by gear that is outside the body of the pump so that the rotor rotates in rhythm. The rotation of the rotor gives rise to empty space so that the fluid can enter into it and move to the outlet side. On the outlet side the two rotor lobes meet so close the existing cavity and push the working fluid out through the pump outlet.

    Rotary Lobe Pump


    Rotary piston pump is the development of a rotary lobe pump. The rotary piston pump rotors are designed in such a way that the pump cavity volume becomes wider. In addition to the pump outlet side, the pump rotor no longer “squeezes” the working fluid out as in the rotary lobe pump, but the rotary piston pump rotation shape will push the fluid out to the outlet side of the pump.

     

    Rotary Piston Pump
    • Vane Pump

    This rotary pump uses a cylinder in the rotor section, a spring-mounted cylinder base connected to the pump rotor. The rotor axis is not aligned with the pump casing axis, so that when the rotor rotates, the rotor cylinder will follow the shape of the casing and push the working fluid to the outlet.

    Vane Pump
    • Peristaltic Pump

    The last rotary type is a peristaltic pump. This type of pump uses a working principle similar to the peristaltic movement of the esophagus. This pump uses a kind of elastic hose as a working fluid conduit. The hose is pressed by the rotor with the tip of the roller to form a push motion.

     

    Peristaltic Pump (Source: Wikipedia)

    Peristaltic pumps were initially widely used in laboratories only, but along with the development of rubber technology, current peristaltic pumps can be used for “heavy” materials including solid materials.

  2. Positive Displacement Reciprocating Pump
    The reciprocating pump uses a piston that moves back and forth as its working component, and directs the working fluid flow to only one direction with the help of a check valve. This positive displacement pump has a widespread work cavity during fluid sucking, and will push it by narrowing down the working cavity. With the help of check valve to regulate fluid flow direction, there will be harmonic pumping process.

    The reciprocating pump consists of several types:

    • Piston Pump

    This pump uses a piston to suck and push the working fluid. The number of pistons depends on the manufacturer’s design that adapts to the system requirements. The less number of pistons in the pump, the flow of water out will be more unstable. To obtain a stable fluid flow can be used pressure relief valve or pump with more pistons.

     

    • Plunger Pump

    This type of pump is similar to a piston pump. What distinguishes is not using a piston, the pump that drives the fluid does not fully fill the cylinder room. For more details see the picture of the difference between the piston pump with the following plunger pump.



    • Diaphragm Pumps

    The pump is also similar to the piston pump but the pump component that performs the back and forth motion is the diaphragm connected to the crank of the drive. The diaphragm will move forward and backward to create changes in the space cavity inside the pump. With the help of check valve then the fluid flow of work can occur.

     

    Diaphragm pumps generally operate at lower pressures than piston or plunger pumps. However, because of its unique design, the diaphragm pump can continue to operate even when there is no fluid flowing in it. And automatically when the working fluid is available again, this pump can naturally primed and vented.

    • Swashplate Pump

    The last type of pump we will discuss is a swashplate pump. This pump is the development of the piston pump. Some pistons are arranged parallel to the one end connected with the upright plate, while the other end is connected to the sloping plate. As the pump shaft rotates the parallel piston-piston rotates to produce a movement back and forth. To better understand this type of pump, let’s consider the following animated video.

    What is interesting about this pump is that the fluid flow discharge can be greatly changed. This can be done by altering the angle of the slope of the plate connected to the pump pistons.

Pumps Classification

In general, pumps are classified into two major groups, the dynamic pump and positive displacement pump. These two big groups are divided into few more.

Dynamic Pump

Dynamic pump is divided into several kinds, centrifugal pumps, axial pumps, and special-effect pumps. These pumps generate high fluid velocity by converting velocity into pressure through the changes of cross-sectional fluid flow. This type of pump has lower efficiency than positive displacement pump, but has lower cost in maintenance. Dynamic pumps can also operate at high speeds and high flow discharge.

  1. Centrifugal Pump


  2. Centrifugal pump composed of an impeller with inlet channel in the middle. With this design, when the impeller rotates, fluid flows into the pump casing around the impeller as a result of centrifugal force. This casing decreases the fluid flow velocity while impeller rotation speed remains high. The fluid velocity is converted into pressure by the casing so that the fluid can reach its outlet point. Centrifugal pump has some advantages include smooth operation in pumps, uniform pressure at pump discharge, low cost, and can work at high speeds so that further applications can be connected directly with steam turbines or electric motors. The use of centrifugal pumps in the world reaches 80% because of its suitable use to cope with large amounts of fluid than positive-displacement pumps.

    Centrifugal Pump
  3. Axial Pumps
  4. Axial pump is also called propeller pump. This pump produces most of the pressure and lifting force from the propeller. These pumps are widely used in drainage and irrigation systems. Single-stage vertical axial pumps are more commonly used, but sometimes two-stage axial pumps are more economical to implement. Horizontal axial pumps are used for large fluid flow discharge with small pressure and usually involve the siphon effect in the flow.

    Axial Pump
  5. Special-Effect Pump
  6. This type of pump used in industries with certain conditions. This type of pump are jet-eductor, gas lift, hydraulic ram, and electromagnetic.

    Jet-eductor pump is using venturi effect of a convergent-diverging nozzle to convert pressure energy from moving fluid to motion energy to create a low pressure area, than can suck fluid on the suction side.

    Injector Pump

    Gas Lift Pump is a way to lift fluid inside a column by injecting a certain gas causing the drop of hydrostatic weight from the fluid so that the reservoir can lift it to the surface.

    The hydraulic ram pump is a cyclic water pump using hydropower.

    And an electromagnetic pump is a pump that drives metal fluids by using electromagnetic forces.

    Electromagnetic Pump


Positive Displacement Pump

Positive displacement pumps are devided into reciprocating and rotary pumps. The positive displacement pump works by assigning a certain force to the fixed fluid volume from the inlet side to the pump outlet point. The advantages of using this type of pump is that it can produce a larger power density, and also provides fluid displacement that is fixed/stable in every turn.

  1. Reciprocating Pumps
  2. At this type of pump, a certain amount of fluid volume enters the cylinder through the inlet valve at entry step and then pumped out under positive pressure through the valve outlet in a step forward. The fluid coming out of the reciprocating pump, pulsating and can only change when the pumping speed changes. This is because the volume of the inlet side is constant. This type of pump is widely used for pumping sediment and sludge.

    Reciprocating Pump

    Metering Pump is included in the reciprocating pump type. This pump can varied the fluid pressure discharge as needed. Metering pumps typically used to pump additives inserted into a particular fluid stream.

    Metering Pump
  3. Rotary Pump
  4. Is a pump that drives the fluid by using the principle of rotation. The vacuum is formed by the rotation of the pump and then sucks the incoming fluid. The advantage of this type is its high efficiency because it naturally removes air from its flow pipe, and reduces the user’s need to manually remove the air.

    This pump weakness is, because of its natural design, the clearence between the swivel blade and the follower blade should be as small as possible. It’s also has requirement to rotate at low and stable speed. If the pump is working at a very high speed, then the working fluid can eroded the pump blades.

    Rotary pumps can be classified into several types:

    • Gear pumps – a simple rotary pump where the fluid is pressed using two gears.
    Gear Pump
    • Screw pumps – These pumps use two threads that meet and rotate to produce the desired fluid flow.
    Screw Pump
    • Rotary Vane Pump – has the same principle as a scroll compressor, which uses a rotating cylindric rotor to produce a certain fluid pressure.
    Rotary Vane Pump

    More details about the various positive displacement pumps, you can open the following article.