Types Of Pumps

What is the pump ?

• Pump is a mechanical device used to transfer different fluids from one position to another.
• It is a hydraulic device that lifts a fluid from a low to a high level and moves it from a low-pressure area to a high-pressure area.
• A hydrodynamic pump machine is device for converting the energy held by  (mechanical energy) to  fluid into  pressure energy.

• Transfer liquid from source to destination.

What are use of pump ?

• Domestic, commercial, industrial and agricultural services.

• Municipal water and waste water services.

•  20 % of worlds  electrical energy demand.

• 25-30 % energy used in some industries.

Pump terminology :

• Head

• Suction Head

• Delivery Head

• Velocity Head

• Static Head

• Manometric Head

• Water Power

• Shaft Power

• Efficiency Of Pump

Factors which influence the choice of pump for a particular operation :

• The quantity of liquid to be handled.

• The head against which the liquid to be pumped/raised.

• The nature of liquid to be handled (viscosity, clear liquids, suspensions, corrosive nature).

• The nature of power supply.

• The method of operation – continuous or intermittent.

• The flow rate required.

• The pressure on delivery.

• Cost and mechanical efficiency.

Classification Of Pump :

The pump can be classified into two main categories :

1.) Dynamic Pump

2.) Positive displacement pump 

1.) Dynamic Pumps :

• Centrifugal pumps

• Vertical centrifugal pumps

• Horizontal centrifugal pumps

• Submersible pumps

• Fire hydrant system

2.) Positive displacement pump :

• Diaphragm pumps

• Gear pumps

• Lobe pumps

• Piston pumps

1.) Dynamic Pump : 

There are different types of dynamic pumps, some of which will be discussed below, such as centrifugal pumps vertical centrifugal pumps, horizontal centrifugal pumps, submersible pumps and fire hydrant systems.

Centrifugal Pump :

Casing : It is an airtight chamber in which the impeller rotates. It is provided with an inlet
(suction) and outlet (discharge) for the liquid to be pumped. The function of the casing is to
convert the kinetic energy  to pressure energy. 

Type Of Casing : (i) volute type casing and (ii) diffuser type casing. 

Impeller : It is a wheel or rotor that is provided with a series of curved blades or vanes. It is mounted on a shaft which is coupled to an electric motor. The impeller is the heart of the centrifugal pump.

Impeller types :(i) Open impeller (ii) Semi-open impeller (iii) Closed or shrouded impeller. 

Open impeller : The open impeller has the blades fixed to a central hub. Such impellers are suited for pumping liquids containing suspended solids, e.g., paper pulp, sewage, etc.

Closed or shrouded impeller : The closed impeller has the blades held between two supporting plates / shrouds (crown plate and base plate). This impeller provides better guidance for the liquid and is more efficient. This type of impeller is suited for pumping clear liquids (liquids containing no suspended particles, dirts, etc.).

Semi-open impeller : The semi-open impeller has only one plate (base plate) and no crown plate (i.e., it has a
plate on one side of the blades/vanes). Such impellers are suitable for liquids containing some solid particles or dirts. 

For viscous liquids or liquids containing solids, open or semi-open type impellers are used. 

The most efficient impeller is the closed or shrouded type.

Stuffing Box :

• In almost all centrifugal pumps, the rotating shaft that drives the impeller penetrates the pressure boundary of the pump casing. It is important that the pump is designed properly to control the amount of liquid that leaks along the shaft at the point that the shaft penetrates the pump casing.

• Factors considered when choosing a method include the pressure and temperature of the fluid pumped, the size of the pump, and the chemical and physical characteristics of the fluid being pumped.

• One of the simplest types of shaft seal is the stuffing box which is cylindrical space in the pump casing surrounding the shaft.

• Rings of packing material are placed in this space to form a seal to control the rate of leakage along the shaft.

• The packing rings are held in place by a gland which is in turn, held in place by studs with adjusting nuts.

• As the adjusting nuts are tightened, they move the gland in and compress the packing. This axial compression causes the packing to expand radially, forming a tight seal between the rotating shaft and the inside wall of the stuffing box.

• The high speed rotation of the shaft generates a significant amount of heat as it rubs against the packing rings.

•  If no lubrication and cooling are provided to the packing, the temperature of the packing increases to the point where damage occurs to the packing, the pump shaft, and possibly nearby pump bearings.

•  Stuffing boxes are normally designed to allow a small amount of controlled leakage along the shaft to provide lubrication and cooling to the packing.

•  The leakage rate can be adjusted by tightening and loosening the packing gland.

Packing :

Shaft : Shaft serves to continue the torque from the drive during operation and the seat of the impeller and other rotating parts.

• Shaft is to transmit the torques,
• Support the impeller and other rotating parts,
• Minimum clearance between the rotating and stationary parts

Loads involved are:

• Torque,
• Weight of the parts, and
• Both the radial and axial hydraulic forces

Shaft Sleave : 

Shaft sleeve serves to protect the shaft from erosion, corrosion and wear of the stuffing box. In multi-stage pump can be as leakage joint, internal bearings and inter stage or distance sleeve.

Vane : Vane is blades of the impeller as a place of passage of fluid in the impeller.

Eye of impeller : The eye of impeller is the entrance side of suction direction of impeller.

Discharge Nozzle  :

Advantages of Centrifugal Pump :

1. It is simple in construction.

2. Due to its simplicity of construction, it can be made in a wide range of materials.

3. Low initial cost and simplicity of design.

4. It operates at high speed and hence, can be coupled directly to an electric motor. In general, higher the speed, smaller the pump and motor required for a given duty.

5. It gives a steady delivery / discharge.

6. Lower maintenance (compared to other pumps) costs.

7. It does not get damaged even if the delivery line becomes blocked, or the delivery valve is closed, provided the pump does not run in this condition for a prolonged period.

8. It can handle readily liquids containing high proportions of suspended solids.

9. The centrifugal pump is much smaller than any other type of pump. Therefore, it can be made into a sealed unit with the driving motor and immersed in the suction tank.

Horizontal centrifugal pumps :

Horizontal centrifugal pumps are a type of pump that uses a horizontal shaft and impeller to move fluid. They are commonly used in a wide range of applications, including industrial processes, water treatment, and HVAC systems.

2.) Positive displacement pump :

A positive displacement pump is a type of pump that moves a fixed volume of fluid with each rotation of the pump’s rotor or piston. This type of pump is also known as a constant flow pump or a volumetric pump.

Diaphragm pumps : 

Diaphragm pumps are a type of positive displacement pump that use a flexible diaphragm to separate the pump’s chamber from the discharge chamber. They are commonly used in a wide range of applications, including industrial, chemical, and pharmaceutical processing, as well as in water treatment, oil and gas, and food and beverage industries.

Types of Diaphragm Pumps : 

Air-Operated Diaphragm Pumps: These pumps use compressed air to move the diaphragm.

Electric Diaphragm Pumps: These pumps use an electric motor to move the diaphragm.

Hydraulic Diaphragm Pumps: These pumps use hydraulic fluid to move the diaphragm.

Gear pumps :

Gear pumps are a type of rotating positive displacement pump that produces a consistent flow of fluid with each rotation. They work by trapping fluid within the machinery, both inside and outside the pump’s network, to create a smooth and efficient pumping action. This design enables gear pumps to handle high-pressure applications and pump highly viscous fluids with ease.

One of the key advantages of gear pumps is their lack of valves, which eliminates losses due to friction and high impeller speeds. This makes them well-suited for handling thick, heavy fluids like fuels and grease. However, gear pumps are not designed to handle solids or harsh liquids, and are best used in applications where the fluid is consistent and free of contaminants.

Lobe pumps :

• Lobe pumps are a type of positive displacement pump that use a rotor with lobes to move fluid through a piping system.
• They are commonly used in a variety of industries, including food processing, pharmaceuticals, and chemical processing, due to their ability to handle viscous and abrasive fluids. 
• These pumps can handle highly concentrated fluids and solids without harming them. These pumps may work with gear pumps, except for the vanes that do not touch each other. 
• These are made of stainless steel and are very polished.

Piston pumps :

Piston pumps are a type of positive displacement pump that use a piston to move fluid through a piping system.

They are commonly used in a variety of industries, including oil and gas, chemical processing, and power generation, due to their ability to handle high-pressure and high-flow applications.

A piston pump consists of a cylinder, piston, and valve assembly.

These pumps are often used for water irrigation, scenarios requiring high, reliable pressure and delivery systems for conveying chocolate, pastry, paint, high viscos slurry etc.