Unit 2 Pump Classification 347l
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Page 1/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
UNITS IN THIS COURSE UNIT 1
PUMP TERMINOLOGY.
UNIT 2
PUMP CLASSIFICATION.
UNIT 3
RECIPROCATING PUMPS.
UNIT 4
ROTARY PUMPS.
UNIT 5
CENTRIFUGAL PUMPS.
Page 2/15
Page 3/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
TABLE OF CONTENTS Para
Page
2.0
COURSE OBJECTIVES
3
2.1
WHY PUMPS ARE USED
4
2.2
PUMP CLASSIFICATION
4
2.3
RECIPROCATING PUMPS
5
2.3.1
Piston Pumps
6
2.3.2
Plunger Pumps
7
2.3.3
Diaphragm Pumps
7
2.4
2.5
2.6
ROTARY PUMPS
8
2.4.1
Gear Pumps
8
2.4.2
Vane Pumps
9
2.4.3
Lobe Pumps
9
CENTRIFUGAL PUMPS
10
2.5.1
Volute Pumps
10
2.5.2
Diff Pumps
11
2.5.3 Turbine Pumps
12
2.5.4
13
Propeller Pumps
IMPELLERS
14
2.7
MULTI-STAGING
15
2.8
INSTALLATION
15
Page 4/15
Page 5/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
2.0
COURSE OBJECTIVES This course describes the different types of pumps commonly found in process plants. The course has five Units. These Units describe the basic terminology of pumps and pumping, the types of reciprocating, rotary and centrifugal pumps, start up of centrifugal pumps, pump problems, and pump control systems. When he has finished the course, the student will be able to: •
Explain the basic terminology of pumps.
•
identify different kinds of pumps and explain their functions.
•
Identify the differences between the main types of reciprocating pumps and explain the end uses of these pumps in process plants.
•
Explain the function of pulsation dampeners.
•
Identify the differences between the main types of rotary pumps and explain the end uses of rotary pumps in process plants.
•
Explain how centrifugal pumps increase pressure.
•
Explain how pump shafts are sealed and how axial and radial thrust are balanced in single stage centrifugal pumps.
•
Explain the reasons for, and the advantages of, multi-stage centrifugal pumps.
•
Explain how axial thrust is balanced in a multi-stage centrifugal pump.
•
Explain how cavitation and vapour lock occur in a centrifugal pump and explain how these problems are overcome.
•
Explain why centrifugal pumps are connected in parallel or in series.
•
Explain the pre-start checks and start-up procedure for centrifugal pumps with electric motor and steam turbine prime movers.
•
Explain the procedure for centrifugal pump changeover.
•
Use pump readings to identify pump problems.
•
Identify and explain pump control systems.
Page 6/15
2.1
WHY PUMPS ARE USED
Page 7/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Pumps are machines which move liquid from one place to another. Pumps work by adding energy to the liquid they are pumping. The liquid being pumped leaves the discharge of the pump with more energy in it than when it entered the pump. The added energy is in the form of pressure, so there is an increase in pressure across the pump. The pump must add enough pressure energy to the liquid to maintain the correct flow rate through the process.
Figure 2-11 A Simple Pumping System Figure 2-1 shows a simple pumping system which draws liquid from a tank and pumps it to a process vessel operating at 100 psig. The discharge pressure of the pump must be sufficient to overcome:
2.2
•
The pressure in the process vessel.
•
The discharge head (the difference in level between the location of the pump and the location of the process vessel).
•
The friction losses in the pipeline.
PUMP CLASSIFICATION Pump classification describes: •
How the pump is built.
•
How the pump moves the liquids through the process.
Page 8/15
Unit No. 2 - Pumps classification Module No. 5 : Pumps
There are two main classifications (groups) of pumps: Page 9/15
•
Positive Displacement (PD) pumps, which are best for high pressures.
•
Centrifugal pumps, which are best for high volumes.
Positive displacement pumps work by trapping a set volume of liquid in a cylinder. Then the liquid is forced out of the pump discharge at higher pressure by the movement of a piston in the cylinder. Centrifugal pumps work by using a centrifugal force to increase the velocity of the liquid. Then the design of the pump casing changes the velocity energy to pressure energy. The liquid is discharged at a higher pressure. Each of the groups above includes a number of different types of pumps which are built for: •
Handling special fluids.
•
Giving different discharge pressures.
•
Giving different discharge volumes.
•
Handling different liquid temperatures.
The two main types of positive displacement pumps are:
2.3
•
Reciprocating pumps which operate with a reciprocating or straight line motion.
•
Rotary pumps which operate with a rotating or circular motion.
RECIPROCATING PUMPS There are three main types of reciprocating pumps: •
piston pumps,
•
plunger pumps,
•
diaphragm pumps.
Some reciprocating pumps have only one cylinder. Other reciprocating pumps have more than one cylinder working together in parallel. Special words are used to describe these pumps:
Page 10/15
Unit No. 2 - Pumps classification
Simplex -one cylinder.
•
Duplex - two cylinders. A duplex pump is good for large volume.
•
Triplex three cylinders. A triplex pump is good for even larger volume.
Module No. 5 : Pumps
•
Page 11/15
The movement of the piston, plunger or diaphragm from one end of the cylinder to the other is called one pump stroke. Pumps are designed to discharge liquids in two methods: Single acting which means that the liquid is discharged at only one end of the cylinder. Therefore, it takes two strokes of the piston to discharge the liquid. Double acting which means that the liquid is discharged at both ends of the cylinder. Therefore, liquid is discharged on each stroke of the piston.
Figure 2-2 Piston Pumps 2.3.1 Piston Pumps In a piston pump the piston forces the liquid out of the cylinder. A single acting pump uses only one side of the piston to force out the liquid. A double acting pump uses both sides of the piston to force out the liquid.
Page 12/15
2.3.2
Plunger Pumps
Page 13/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Figure 2-3 Plunger Pump In a plunger pump the plunger forces the liquid out of the cylinder. Plunger pumps are only single acting pumps. 2.3.3
Diaphragm Pumps
Figure 2-4 Diaphragm Pump
Page 14/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
In a diaphragm pump the movement of the diaphragm forces the liquid out of the cylinder. Most diaphragm pumps are single acting, but they can be double acting. Diaphragm pumps are good for pumping corrosive or abrasive liquids. 2.4
ROTARY PUMPS Rotary pumps are classed as positive displacement pumps. The three most common types are: Gear pumps. Vane pumps. Lobe pumps.
2.4.1
Gear Pumps In a gear pump the gears do the pumping. Gear pumps may have external or internal gears. In an external gear pump the two gear wheels are meshed together side by side. In an internal gear pump one gear wheel is fitted inside the other.
Figure 2-5 Gear Pumps
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
2.4.2
Vane Pumps
Figure 2-6 Vane Pumps Vane pumps may be sliding vane pumps or swinging vane pumps. This describes the way the vanes are attached to the rotor of the pump. In a sliding vane pump the vanes move in and out of the rotor with the shape of the pump casing. In a swinging vane pump the vanes are attached to the rotor by a hinge. By moving on the hinge the vanes are able to rotate with the shape of the casing. 2.4.3
Lobe Pumps
Figure 2-7 Lobe Pumps Lobe pumps have two specially shaped rotors. The rotors mesh together to move the liquid through the pump. The rotors of a lobe pump may have two or three lobes.
2.5
CENTRIFUGAL PUMPS
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
he four main types of centrifugal pumps are: Volute pumps. Diff pumps Turbine pumps. Propeller pumps. 2.5.1
Volute Pumps
Figure 2-8 Volute Pump Volute pumps are the most common type of centrifugal pump to be found in a process plant. They usually operate without problems and do not require much maintenance.
A volute pump works like this:
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
The liquid being pumped is drawn into the centre (eye) of the impeller. Because the impeller is turning very fast centrifugal force makes the liquid move out to the edge of the impeller. As the liquid moves out to the edge of the impeller its velocity is increased. The liquid is discharged from the impeller into the volute. The shape of the volute changes the velocity energy of the liquid to pressure energy. The liquid is discharged from the pump with higher pressure than when it entered the pump. 2.5.2
Diff Pumps
Figure 2-9 Diff Pump Diff pumps are very efficient. They are used for high capacity, high pressure service. A diff pump works in the same way as a volute pump. In a diff pump the velocity energy is changed to pressure energy as the liquid es through the diff vanes.
2.5.3
Turbine Pumps
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Figure 2-10 Turbine Pump Turbine pumps are small. They are best for low capacity, high pressure service of clean liquids. Because the clearances inside the pump are very close, rapid 'Wear takes place if the pumped liquid contains abrasives. A turbine pump works like this: The impeller vanes travel in a channel in the pump casing. The liquid being pumped is directed to the outside edge of the impeller. The impeller makes the liquid travel in almost a complete circle. As the liquid travels it receives a series of 'pushes' from the impeller vanes. Each push increases the pressure of the liquid.
2.5.4 Propeller Pumps
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Figure 2-11 Propeller Pump
Propeller pumps are small. They are used for low pressure, high capacity service. The pump works in a similar way to the blades of an electric fan or the propellers of an aircraft. The shape of the impellers increases the pressure of the pumped liquid.
2.6
IMPELLERS
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
In a volute pump the device which rotates inside the pump casing to give velocity energy to the liquid is called an impeller.
Figure 2-12 Types of Impellers for Volute Pumps
Open impellers are used to pump liquids that contain small amounts of solids that might block the pump or become trapped between the impeller and the casing Semi-open and semi-closed impellers are used to pump liquids that contain many solid materials. Enclosed impellers are used for liquids which contain only small amounts of solid materials. This type of impeller is the most common and is very efficient.
2.7 MULTI-STAGING
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Centrifugal pump impellers only give a small amount of pressure energy to the liquid. To increase the final pump discharge pressure the impellers are connected together in series on one shaft. This is called multi-staging. If each impeller gives 10 barg of pressure to the liquid and there are 6 impellers in series, the final pump discharge pressure will be 60 barg. Each impeller is called a stage, so the pump described above is a 6 stage pump. Pumps may have many stages from 1 to 60 depending on the process requirements. 2.8
INSTALLATION Centrifugal pumps can be installed horizontally or vertically depending on the process requirements.
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
UNITS IN THIS COURSE UNIT 1
PUMP TERMINOLOGY.
UNIT 2
PUMP CLASSIFICATION.
UNIT 3
RECIPROCATING PUMPS.
UNIT 4
ROTARY PUMPS.
UNIT 5
CENTRIFUGAL PUMPS.
Page 2/15
Page 3/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
TABLE OF CONTENTS Para
Page
2.0
COURSE OBJECTIVES
3
2.1
WHY PUMPS ARE USED
4
2.2
PUMP CLASSIFICATION
4
2.3
RECIPROCATING PUMPS
5
2.3.1
Piston Pumps
6
2.3.2
Plunger Pumps
7
2.3.3
Diaphragm Pumps
7
2.4
2.5
2.6
ROTARY PUMPS
8
2.4.1
Gear Pumps
8
2.4.2
Vane Pumps
9
2.4.3
Lobe Pumps
9
CENTRIFUGAL PUMPS
10
2.5.1
Volute Pumps
10
2.5.2
Diff Pumps
11
2.5.3 Turbine Pumps
12
2.5.4
13
Propeller Pumps
IMPELLERS
14
2.7
MULTI-STAGING
15
2.8
INSTALLATION
15
Page 4/15
Page 5/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
2.0
COURSE OBJECTIVES This course describes the different types of pumps commonly found in process plants. The course has five Units. These Units describe the basic terminology of pumps and pumping, the types of reciprocating, rotary and centrifugal pumps, start up of centrifugal pumps, pump problems, and pump control systems. When he has finished the course, the student will be able to: •
Explain the basic terminology of pumps.
•
identify different kinds of pumps and explain their functions.
•
Identify the differences between the main types of reciprocating pumps and explain the end uses of these pumps in process plants.
•
Explain the function of pulsation dampeners.
•
Identify the differences between the main types of rotary pumps and explain the end uses of rotary pumps in process plants.
•
Explain how centrifugal pumps increase pressure.
•
Explain how pump shafts are sealed and how axial and radial thrust are balanced in single stage centrifugal pumps.
•
Explain the reasons for, and the advantages of, multi-stage centrifugal pumps.
•
Explain how axial thrust is balanced in a multi-stage centrifugal pump.
•
Explain how cavitation and vapour lock occur in a centrifugal pump and explain how these problems are overcome.
•
Explain why centrifugal pumps are connected in parallel or in series.
•
Explain the pre-start checks and start-up procedure for centrifugal pumps with electric motor and steam turbine prime movers.
•
Explain the procedure for centrifugal pump changeover.
•
Use pump readings to identify pump problems.
•
Identify and explain pump control systems.
Page 6/15
2.1
WHY PUMPS ARE USED
Page 7/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Pumps are machines which move liquid from one place to another. Pumps work by adding energy to the liquid they are pumping. The liquid being pumped leaves the discharge of the pump with more energy in it than when it entered the pump. The added energy is in the form of pressure, so there is an increase in pressure across the pump. The pump must add enough pressure energy to the liquid to maintain the correct flow rate through the process.
Figure 2-11 A Simple Pumping System Figure 2-1 shows a simple pumping system which draws liquid from a tank and pumps it to a process vessel operating at 100 psig. The discharge pressure of the pump must be sufficient to overcome:
2.2
•
The pressure in the process vessel.
•
The discharge head (the difference in level between the location of the pump and the location of the process vessel).
•
The friction losses in the pipeline.
PUMP CLASSIFICATION Pump classification describes: •
How the pump is built.
•
How the pump moves the liquids through the process.
Page 8/15
Unit No. 2 - Pumps classification Module No. 5 : Pumps
There are two main classifications (groups) of pumps: Page 9/15
•
Positive Displacement (PD) pumps, which are best for high pressures.
•
Centrifugal pumps, which are best for high volumes.
Positive displacement pumps work by trapping a set volume of liquid in a cylinder. Then the liquid is forced out of the pump discharge at higher pressure by the movement of a piston in the cylinder. Centrifugal pumps work by using a centrifugal force to increase the velocity of the liquid. Then the design of the pump casing changes the velocity energy to pressure energy. The liquid is discharged at a higher pressure. Each of the groups above includes a number of different types of pumps which are built for: •
Handling special fluids.
•
Giving different discharge pressures.
•
Giving different discharge volumes.
•
Handling different liquid temperatures.
The two main types of positive displacement pumps are:
2.3
•
Reciprocating pumps which operate with a reciprocating or straight line motion.
•
Rotary pumps which operate with a rotating or circular motion.
RECIPROCATING PUMPS There are three main types of reciprocating pumps: •
piston pumps,
•
plunger pumps,
•
diaphragm pumps.
Some reciprocating pumps have only one cylinder. Other reciprocating pumps have more than one cylinder working together in parallel. Special words are used to describe these pumps:
Page 10/15
Unit No. 2 - Pumps classification
Simplex -one cylinder.
•
Duplex - two cylinders. A duplex pump is good for large volume.
•
Triplex three cylinders. A triplex pump is good for even larger volume.
Module No. 5 : Pumps
•
Page 11/15
The movement of the piston, plunger or diaphragm from one end of the cylinder to the other is called one pump stroke. Pumps are designed to discharge liquids in two methods: Single acting which means that the liquid is discharged at only one end of the cylinder. Therefore, it takes two strokes of the piston to discharge the liquid. Double acting which means that the liquid is discharged at both ends of the cylinder. Therefore, liquid is discharged on each stroke of the piston.
Figure 2-2 Piston Pumps 2.3.1 Piston Pumps In a piston pump the piston forces the liquid out of the cylinder. A single acting pump uses only one side of the piston to force out the liquid. A double acting pump uses both sides of the piston to force out the liquid.
Page 12/15
2.3.2
Plunger Pumps
Page 13/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Figure 2-3 Plunger Pump In a plunger pump the plunger forces the liquid out of the cylinder. Plunger pumps are only single acting pumps. 2.3.3
Diaphragm Pumps
Figure 2-4 Diaphragm Pump
Page 14/15
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
In a diaphragm pump the movement of the diaphragm forces the liquid out of the cylinder. Most diaphragm pumps are single acting, but they can be double acting. Diaphragm pumps are good for pumping corrosive or abrasive liquids. 2.4
ROTARY PUMPS Rotary pumps are classed as positive displacement pumps. The three most common types are: Gear pumps. Vane pumps. Lobe pumps.
2.4.1
Gear Pumps In a gear pump the gears do the pumping. Gear pumps may have external or internal gears. In an external gear pump the two gear wheels are meshed together side by side. In an internal gear pump one gear wheel is fitted inside the other.
Figure 2-5 Gear Pumps
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
2.4.2
Vane Pumps
Figure 2-6 Vane Pumps Vane pumps may be sliding vane pumps or swinging vane pumps. This describes the way the vanes are attached to the rotor of the pump. In a sliding vane pump the vanes move in and out of the rotor with the shape of the pump casing. In a swinging vane pump the vanes are attached to the rotor by a hinge. By moving on the hinge the vanes are able to rotate with the shape of the casing. 2.4.3
Lobe Pumps
Figure 2-7 Lobe Pumps Lobe pumps have two specially shaped rotors. The rotors mesh together to move the liquid through the pump. The rotors of a lobe pump may have two or three lobes.
2.5
CENTRIFUGAL PUMPS
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
he four main types of centrifugal pumps are: Volute pumps. Diff pumps Turbine pumps. Propeller pumps. 2.5.1
Volute Pumps
Figure 2-8 Volute Pump Volute pumps are the most common type of centrifugal pump to be found in a process plant. They usually operate without problems and do not require much maintenance.
A volute pump works like this:
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
The liquid being pumped is drawn into the centre (eye) of the impeller. Because the impeller is turning very fast centrifugal force makes the liquid move out to the edge of the impeller. As the liquid moves out to the edge of the impeller its velocity is increased. The liquid is discharged from the impeller into the volute. The shape of the volute changes the velocity energy of the liquid to pressure energy. The liquid is discharged from the pump with higher pressure than when it entered the pump. 2.5.2
Diff Pumps
Figure 2-9 Diff Pump Diff pumps are very efficient. They are used for high capacity, high pressure service. A diff pump works in the same way as a volute pump. In a diff pump the velocity energy is changed to pressure energy as the liquid es through the diff vanes.
2.5.3
Turbine Pumps
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Figure 2-10 Turbine Pump Turbine pumps are small. They are best for low capacity, high pressure service of clean liquids. Because the clearances inside the pump are very close, rapid 'Wear takes place if the pumped liquid contains abrasives. A turbine pump works like this: The impeller vanes travel in a channel in the pump casing. The liquid being pumped is directed to the outside edge of the impeller. The impeller makes the liquid travel in almost a complete circle. As the liquid travels it receives a series of 'pushes' from the impeller vanes. Each push increases the pressure of the liquid.
2.5.4 Propeller Pumps
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Figure 2-11 Propeller Pump
Propeller pumps are small. They are used for low pressure, high capacity service. The pump works in a similar way to the blades of an electric fan or the propellers of an aircraft. The shape of the impellers increases the pressure of the pumped liquid.
2.6
IMPELLERS
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
In a volute pump the device which rotates inside the pump casing to give velocity energy to the liquid is called an impeller.
Figure 2-12 Types of Impellers for Volute Pumps
Open impellers are used to pump liquids that contain small amounts of solids that might block the pump or become trapped between the impeller and the casing Semi-open and semi-closed impellers are used to pump liquids that contain many solid materials. Enclosed impellers are used for liquids which contain only small amounts of solid materials. This type of impeller is the most common and is very efficient.
2.7 MULTI-STAGING
Module No. 5 : Pumps
Unit No. 2 - Pumps classification
Centrifugal pump impellers only give a small amount of pressure energy to the liquid. To increase the final pump discharge pressure the impellers are connected together in series on one shaft. This is called multi-staging. If each impeller gives 10 barg of pressure to the liquid and there are 6 impellers in series, the final pump discharge pressure will be 60 barg. Each impeller is called a stage, so the pump described above is a 6 stage pump. Pumps may have many stages from 1 to 60 depending on the process requirements. 2.8
INSTALLATION Centrifugal pumps can be installed horizontally or vertically depending on the process requirements.
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