This article aims to hopefully help select a well pump and factors that need to be kept in mind before a well pump is installed. The article tries to provide an easy guide to know the type of well pump commonly used for various displacement of fluids and the basic principle on which the pump functions.
The principle on which a pump function helps to understand the type of pump that a particular fluid should be used to displace.
Before we dwell on the details of well pumps, we need to understand pumps and wells. Wells are excavation or digging made in the ground to extract liquid, especially water from the underground aquifer.
Water is drawn manually or by pumps. Manually it is drawn by containers or buckets or is drawn by animals like oxen and horses. Wells may be unlined or lined with bricks or stone or more recent commissioning.
Pumps are devices that are used to move liquid and sometimes slurries from one place to another. This movement of liquid is achieved by converting electrical energy into hydraulic energy. Well, pumps are mostly used to draw water or to move water from one place to another.
Centrifugal well pump:
Physics behind the centrifugal pump is that it converts rotational kinetic energy to hydrodynamic energy to transport fluid from lower level to higher level. Many types of pf centrifugal pumps depend upon the number of impellers. These are:
Here, there is only one impeller with a simple design and easy maintenance. It is used in pumping services with a high flow to low and moderate total dynamic head (TDH).
There are two impellers operating side by side used for the medium head application.
Three or more impellers are operating for high head service.
Submersible well pumps:
As the name suggests, the pump is submerged in the fluid. This device has a hermetically sealed motor, which is close-coupled to the body of the motor. The pump is fully submerged in the fluid. Water is pushed to the surface by the pump.
This is done by converting rotary energy into kinetic energy then into pressure energy. Water is first pulled into the impeller through rotation, and it is then pushed through the diffuser from where it goes to the surface. Here water pushes the water into the pump, saving energy of the pump.
There are various types of submersible pumps; some common types are:
Bladder well Pumps:
It uses compressed air. It does not come in contact with the liquid and positively displaces the liquid. It is a pneumatically operated pump.
Grinder well Pumps:
It is used for wastewater conveyance. Water from household appliances that use water (toilet, bathtub, washing machine, etc.) flows through the pipes to the pump tank. When the water reaches a certain level, the pump starts and grinds it into slurries. And then pumps it into a septic tank or central sewage system.
Borehole well Pumps:
It is a type of submersible pump used to extract water from underground. It supplies water to farms, households, and industries.
Fountain well Pumps:
These are centrifugal pumps pressure is created by the movement of an impeller. It works like a sump pump.
Utility well Pumps:
These pumps can displace water in large quantities but cannot be used continuously.
Vertical turbine well pump:
Vertical turbine well pumps are centrifugal pumps. These are designed to draw water from underground wells or reservoirs. Impellers of the pump are located at the bottom of the well or reservoir. The electric motor is placed above the ground.
It is connected to the impellers by a long vertical shaft. Though the name has a turbine in it, the turbine has no function in this pump. The vertical turbine pump is run by A.C electric current or by diesel. The shaft is attached to a rotating impeller.
This shaft directs the water to the diffuser bowl. From here, it enters the vertical pipe to the surface. A vertical turbine pump is used at places where submersible cannot be used.
The most common type of submersible pump used is well pumps. It is easy to install and can function in a variety of conditions.
A water well pump is used to extract water from an underground aquifer. The water table may be closer to the surface, or it may be deeper down. For such conditions, different types of well pumps are used. Commonly used well pumps are as follows:
Hand well pump:
These are manually operated. They use human power along with mechanical advantage. Hand well pumps are commonly used in the developing world. The principle used is based on the operation of the piston and positive displacement. These can be fitted on hand-dug well or borewell. These widely prevalent in the developing worlds. Few types commonly used are:
Suction and lift well pump:
Suction is the vertical distance between the pump’s center and the fluid to be pumped. Lift is the distance between the delivery point and the pump. Atmospheric pressure plays an essential part in deciding the depth from which water can be drawn. Water can be lifted following the operator’s ability and the pump to lift the weight in the delivery pipe.
Force well pump:
This is also a manual pump, and it works on the same principle as a suction pump. It is used when water is to be lifted above 7 meters or when water is supplied with force. As the piston attached to the handle is raised, the water is sucked through the lower valve and out through the exit point on the main cylinder’s side.
Siphon well, diaphragm well, deep well direct action, chain well pump
This range of lifts are other types of hand pumps used though not widely because of its less efficiency or high maintenance or becoming obsolete.
Injector well pump or jet driven well pump:
Deep well pump uses two principles of pumps. One is centrifugal pumping, and the other is jet injector using nozzle and venturi assembly. Water is full of a pump and pipe system. Water is thrown outward by the vanes of the spinning impellers.
The injector jet pump is designed to work in tandem with the centrifugal pumping system and injector. The function of the injector is to enhance the pressure capacity of the centrifugal system of the pump. A most common type of jet-driven well pumps are:
Shallow well jet pump:
shallow jet pumps are similar to vertical centrifugal pumps. Shallow jet pumps are positioned above the ground level. It can lift water upto 25 feet only. The shallow jet pump has the same type of working as the centrifugal pump. Only it helps to exert more pressure on it.
Deep-well jet pump:
Deep well jet pump is put down in the well below the water level. This location of the well pump helps to push water to the surface. Suction lifts the water to bring water into the system. Impellers put pressure. This arrangement of the deep well jet pump lifts the water to the surface.
Mechanical well pump or rotary lobe well pump:
Rotary lobe pumps work on the principle of counter-rotation of two pumping elements(rotors) with is placed within a chamber. Rotors are placed on the shafts and are held in place by bearings mounted on the gearbox.
Rotary lobe pumps can be easily cleaned and are easy to maintain. This type of pump is usually used in food and pharma industries because of their ability to pump food and pharma fluids.
Solar-powered well pump:
Solar-powered pump works on power generated by the solar photovoltaic system. Solar energy is converted to electrical energy which is then used to draw water from the pump. Water is drawn from an open well, bore well, pond, stream, canal, etc.
A solar water pumping system is reliable, durable, eco-friendly. The solar-powered pump is also easy to operate and maintain and has a long operating life.
What to consider while choosing a well pump?
Before choosing a pump, various factors are to be kept in mind. These can be summarised as follows:
Process liquid properties:
Following properties of the liquid are to be checked before selecting a pump:
- Liquid viscosity
- Specific gravity
- Vapour pressure
- Solids present & concentration
- Shear sensitive
- Abrasive or Non-abrasive
The material of construction:
Type of liquid to be displaced has to be compatible with the pump’s material. Chemical compatibility has to be determined before selecting a pump.
Central to the function of operation:
If a pump is required to work without any downtime, then the heavy, expensive pump should be used. Whereas, it can be removed after use; then, a less expensive pump can be utilized to save resources and time.
Pump inlet condition:
Pump inlet pressure and liquid vapor pressure is to be considered. It is to be noted that NPSHA exceeds NPSH.
If a pump is to be installed outside, the pump must be made workable in freezing temperatures. If the environment in which a pump is to be placed in hazardous, then necessary precaution is to be made. These are some of the environment the has to be considered before installing a pump.
Availability of power sources:
Pumps are run either on electricity, diesel, compressed air, or hydraulic oil. What is available at cheaper cost at the place of installation need to be considered.
Flow rate and pressure:
Total volume of fluid to be moved and time to displace fluid must be kept in mind. Accordingly, pipe size, static lifts, system equipment, friction loss is calculated.
Thus there are various types of well pumps to displace water or other fluids from one place to another. Various factors stated in the above article should be kept in mind when installing a well pump.