The Best Tutorial On Practical Application And |Types Of Pumps

Types of Pumps

Introduction

In this post on the Types of Pumps, I will explain the following.

1) The primary classification of the pumps.

2) Working principles of all categories of pumps.

3) Each Type of pump with details.

What is Pump?

A pump is a machine for transferring a liquid or gas from one location to another location.

In the process, the pump converts the mechanical energy into the pressure energy of Liquid or gas.

The pump’s primary function is to transfer the Liquid from the lower potential to the higher side.

Classification of Pumps

The Pumps are of two categories.

1. Centrifugal Pumps
2. Positive Displacement Pumps

Centrifugal Pumps

Centrifugal pump works on the principle of centrifugal force. An electric motor or any other source of power rotates the impeller.

The rotating impeller creates a vacuum at its eye. This vacuum sucks the liquid or gas via a suction pipe.

Centrifugal force pushes the liquid or gas outward. Vanes convert the kinetic energy of the flowing fluid into pressure energy due to the shape of the casing.

Subcategories of Centrifugal pumps

As per the flow type, centrifugal pumps are of the following three subcategories.

1) Radial Flow

2) Axial Flow

3) Combination of Radial and mixed flow.

Radial Flow Pumps: — In these pumps, liquid flows in the perpendicular direction to the shaft. These pumps transmit the fluid at high pressure. The flow rate of these pumps is too low.

Axial Flow Pumps;- in the axial flow type pumps, liquid flows parallel to the shaft. The flow rate of their pumps is high, but the pressure is low.

Combination of Radial and mixed flow;- In these types of pumps, liquid flows in a conical pattern. The flow is a mixture of Axial and radial

Positive Displacement Pumps

This type of pump creates a cavity at the suction side. The pump draws the fluid in suction stroke and delivers the fuel at high pressure in discharge stroke.

The delivery of fluid is with a fixed quantity in each stroke.

The everyday use of these pumps is for the process with high pressure and fixed delivery.

These types of pumps are self-priming types.

Categories of Positive Displacement Pumps

These pumps are of following two categories basing on the flow of fluid.

1. Reciprocating;- In this category the basic working principle is expansion and contraction. In the expansion pump draws the fluid through suction and discharges the fluid at higher pressure on the contraction.

The design of these pumps is of following type.

• Piston Pump.
• Plunger pump
• Bladder Pump.
• Diaphragm type pump
• Roller pump.

2. Rotary pump.

In these types of pumps Gear or screw creates the pumping space. The trapped fluid moves along the spaceand displace it to the discharge side.

Rotary pumps are of the following types.

• gear pump
• Screw Pump
• Cavity pump
• Lobe type pump
• Vane pumps

Most popular use is of Gear pump, screw and reciprocating pumps on board ships.

Gear Pump

The gear pump is the category of positive displacement type pump. There are two gears in the gear pump, Drive gear, and driven gear. The direction of rotation of both the gears is opposite to each other.

At the suction side gear, teeth create the suction during their disengaging movement. This process creates a vacuum to suck the fluid. Rotating gears carry the fluid with their rotation along with the casing.

This process transfers the fluid at the pressure on the discharge side. The engagement of gears creates the seal to develop high pressure at the discharge.

Screw Pumps

Screw pumps are self-priming positive displacement pumps. These pumps consist of multi shafts with left and right hand screws.

Shafts rest on ball bearings.

During the rotation of the pump, fuel enters the suction port. Fluid propels along the body, and high-pressure fluid exists out at the discharge outlet.

The movement of fluid is axial along with the screw.

The screw displaces the fluid during its rotation.

Reciprocating Types of Pumps

This type of pump category has the piston and cylinder. The pump cylinder connects with the suction and discharge pipes with non-return valves. The non-return valves are uniflow type.

Connecting rod connects the piston with the crankshaft. The piston rings seal the cylinder.

sub-categories of reciprocating Types of Pumps.

1) Single acting pump

2) Double-acting pumps.

Please refer to the below diagram for a better understanding of the pump function.

1) In the upward stroke, valve 1 closes due to the suction effect.

2) Valve 3 opens due to the pressure effect.

3) Another side of the assembly, valve 4 closes, and valve 2 opens, expelling the pressurized fluid.

During the downward stroke, valve 1 opens, and valve 4 closes, expelling the fluid to discharge. On the other side, valve 3 opens due to the suction effect, and valve 2 closes.

Air vessel reduces the pulsating effect at the discharge.

Advantages of Centrifugal Types of Pumps

1. Discharge of fluid is with steady flow.
2. These pumps don’t use air vessels for the reduction of pulsating effect.
3. There is no requirement for a relief valve.
4. High discharge flow rate

Disadvantages of centrifugal Types of Pumps

1. Low discharge flow rate.
2. The usage of the pump is only with low viscosity fluids.
3. The problem of high cavitations.

Advantages of Positive displacement Types of Pumps

1. Pumps are self-prime type.
2. Pumps have high discharge head pressure.
3. The usage of the pumps is for high viscosity fluids.

No cavitation problem

1. Pumps are self-prime type.
2. Pumps have high discharge head pressure.
3. The usage of the pumps is for high viscosity fluids.
4. No capitation problem

Disadvantages of Positive displacement -Types of Pumps

1. Unsteady discharge flow
2. It needs an additional component to reduce the pulsating effects.
3. Low discharge flow rate.

Important Guidelines for the Pump maintenance

1. Carry out the greasing of bearings regularly
2. Check and maintain the Lube oil level of mechanical seals.
3. Carry out the tightening of the gland packings carefully in case of any leakage.
4. Replace the gland packings periodically.
5. Check the power drawn by the pump motor in the running condition of the pump.
6. Check the vibration of the pump regularly.
7. Monitor the suction and discharge pressure of the pump while the vessel is on light load and fully loaded condition for the variation of NPSH.
8. Check and tighten the coupling bolts.
9. Clean the filters and strainers in the system line of the pump.

Pump Alignment

In alignment, we align the centreline of the pump with the centreline of the driver.

Alignment is very crucial in the case of the pumps using the rotating seals. A minor misalignment at the power end may cause the frequent failure of seal.

Problems due to misalignment

We are listing below the problems due to the misalignment.

1. Misalignment can cause them to and fro the movement of the seal. To and fro movement of the seal will result in the opening up of the lapped face of the seal.
2. A mechanical seal can’t support the misaligned shaft.
3. There will be severe fretting on the shaft or sleeve.
4. Pump bearing will have excessive loading.
5. The stationary and rotating part of the seal will make contact and will result in damages.
6. Wear rings will have the contact.
7. The shaft will contact with a bushing at the end of the stuffing box.
8. The impeller will have contact with the pump volute/ back plate.

Important Points before the alignment -Types of Pumps

1. The shaft of the pump should be straight and well balanced.
2. Wear rings should be in good condition with correct clearance.
3. Clearance between impeller to volute or back plate should be proper.
4. End the soft foot on Pumpm and driver.
5. Check and end pipe strains on the pump
6. Bearings on the shaft should be in good condition with proper clearance.
7. The mechanical seal should be with proper load on face. The seal should be as closer about the pump bearing.

Stages of Alignment

1. Carry out the levelling of the pump and driver. Without levelling oil, the level will be challenging to maintain the lube oil level.
2. Take many measurements in axial and radial directions to observe the location of the pump concerning the driver.
3. Consider the operating temperatures of the pump and the driver.
4. Add the shims at required points/ foot.

Acceptable methods of alignment

1. Reverse Indicator method;- This method is acceptable. But this method is time-consuming.

• This method is an accurate method for small diameter flanges.
• Axial float doesn’t affect the alignment.
• The use of flexible coupling is possible.
• Rotation of both the shaft is essential.
• Laser alignment method.;- this procedure f alignment is the latest method widely acceptable in industries.
• C and D frame adapter method;- This method is the easiest alignment method. This procedure takes care of thermal expansion problems.

Reason of vibrations in Pump

Listed below re the causes of vibrations in pump

1. Suction starvation
2. Vapour or gas lock in the fluid
3. Gas in suction line.
4. Insufficient Net Positive suction Head
5. Misalignment
6. There will be steady misalignment in centrifugal pumps.
7. Improper clamping of pipe lines
8. Worn out or loose bearings
9. Unbalance in rotating element
10. Bent shaft
11. Vibration transmission from driver
12. Opening and closing period of shutoff valve is not matching with the the pump speed.
13. Vibration in reciprocating pumps
14. Fluid end leaky valves
15. Poor condition of valves
16. Insufficient lubrication i the pump rod, stuffing box and power end of pump.
17. Worn out piston rings
18. Gas or vapours in liquid
19. Over speeding

Conclusion

I hope the post on Types of Pumps would have provided the desired information to reaers.

Good Luck !!