What is Submersible Pump? Definition, Parts, Working, Installation, Maintenance

In this article, we will learn what is submersible pump. along with its definition, parts, working, installation, maintenance, etc. Let’s explore!

What is Submersible Pump? Definition

Submersible pumps are known for completely submerging within a liquid. It has various pumping applications and is widely used to pump the fluid from the low-pressure region to the high-pressure region. These types of pumps have advantages and disadvantages as well. Pumps that are typically used in daily life like well-pumps are submersible.

Definition of Submersible Pump

A submersible pump or electric submersible pump is a widely used electric pump that is fully submerged in water or liquid that needs to be pumped. The electric sealed motor is coupled closely to the pump body.

• These pumps lift liquid from low level to high by converting the motor’s mechanical energy to liquid flow.
• No energy is used to operate because the pump uses the head of the liquid to draw the liquid into the pump, which makes it more efficient.

Submersible Pumps Basics

Submersible pumps are designed to lift liquid to the surface and utilize pressurized fluid from the surface to operate an electric motor. These pumps are being developed for appropriate immersion in various liquids. Because of complete submerging in water, the pump never overheated, and the surrounded water continuously cools the pump and prevents overheating. The motor is surrounded by a tight enclosure usually filled with oil to avoid any electric damage to the motor due to the inflow of liquid.

The larger submersible pumps consist of a sensor between motor and pump that senses the passing of liquid through the water seal and stops the motor from further action until repaired back. Many submersible pumps are designed within the water, just like other water pumps with different types where each has its application.

These pumps are simple, quiet in operation, more efficient, and easy to install. Submersible pumps are used to pump out the liquid from the great depths and in those situations where gravity flow is impossible.

Submersible Pumps History

In ancient times, people used to dig down on earth, scooping out water and mud to reach clean water like it is evident from the ancient wells of Cyprus, two wells located in Israel from the Neolithic period. But with time, people had developed the concept of the good pump. Hence, many changes and progressions happened in the revolutionary development of the pump’s structure, shape, constructions, and operations.

For the first time in America, the oil delivery engineer Armais Sergeevich Arutunoff successfully installed a submersible oil pump in the oil field in 1928. After that, these were frequently used in Europe, but in 1950, wastewater, foul-water, and sewage water pumps were seen in the United States.

Initially, these pumps were installed and operated in mining industries, wells, and shipping, but due to technological modification in the pump’s design, their use is started in oil wells. Improvements in Arutunoff’s pump led to the evolution of many kinds of submersible pumps used in different industries.

How Does Submersible Pump Work?

• In the oil and gas industry, many submersible pumps work on the electric submersible pumping principle (ESP). Here, the motor’s mechanical energy is initially converted to kinetic and then to pressure energy, and due to this conversion of the energy, the water or other liquid is pushed to the surface. Firstly, the water is pumped inside to the pump, and then it is supplied to the outside by impellers.
• These pumps are generally multi-level centrifugal pumps that operate in a vertical position. Through mechanical coupling, the motor’s shaft is connected either to the protector or separator at the bottom side of the pump.
• The ingesting screen allows liquid to move inside. Then, the pump elevates the liquid. This basic principle is used both in mixed flow and radial flow.
• Along the motor’s shaft length, the radial bearing provides radial support to the shaft during high rotational speeds.
• The axial forces that arise in the pump are taken by an optional thrust bearing or protector’s thrust bearing. 
• On the other hand, the hydraulic motor in the hydraulic submersible pump is kept isolated from the liquid in a closed cycle of the liquid. While in the open cycle, the generated liquid is mixed with power liquid at the surface.

Main Parts of Submersible Pump

The main parts of a typical submersible pump include a multistage centrifugal pump, electric motor, intake section or gas separator, seal section, and electric cables. Similarly, additional parts such as check and bleeder valves and surface equipment are installation components, which ensure the securing of cables. These all parts and components are discussed as below:

Multistage Centrifugal Pump

It consists of two parts: the rotating part known as the impellers and the diffuser’s stationary part. Relatively low head or lift is developed by stage due to limited diameter of well, and many stages are stuck together for artificial installation.

According to the axial trust handling in the pump, these stages are arranged as floated or fixed impeller pumps. The impellers are free to move in the floater pump, while in a fixed pump, these are fixed to the shaft and can not move freely.

Electric Motor

The submersible electric motor is the rotatory part of the pump that is a two-pole, three-phase induction motor rotating at about 3445-3500 RPM at full load. The windings and laminations of the stator are enclosed in a carbon steel housing. The intermediate bearing supports a series of rotors that constitute a rotating assembly.

The power of the motor depends on the length and number of rotors. The motor which is single-section is about 33 feet lengthy and facilitates proper transportation.

Seal Section

The seal section is designed to perform the following actions:

• To protect the motor from the inflow of fluid.
• To help the bearings trust to carry the developed axial thrust.
• The seal section eliminates the pressure difference across the shaft seals by equalizing the inside pressure in the motor with the wellbore pressure.
• When the unit is operating or shut down, the seal section compensates for the expansion and contraction of motor oil due to cooling and heating.

Moreover, the expansion bag prevents the motor oil from the well fluid. The two mechanical shaft seals eliminate the well fluid along the shaft.

Intake Section

Depending on the excellent condition, it can be a gas separator that plays the role of the suction manifold and feeds the well fluid to the impeller eye. In low-bottom hole-pressure applications, there can be a significant amount of gas that may cause severe effects on pump performance.

In such conditions, the intake section is usually replaced by a gas separator that can remove the well fluid before it enters the pump. As the well fluid passes through the impeller, the centrifugal forces separate the liquid of higher density and throw it to the periphery of the pump while gas gathers at the center in the form of a core. The gas is then moved to the annular space while high-density liquid enters the impeller eye.

Electric Pump Cable

It is composed of multiple wires which transmit the power and can be twisted or laid straight. Electric cable is usually found in the stranded or solid-core wire. These wires are highly flexible and can withstand considerable flexing, and are usually located in applications where the pump cables are tightly routed.

It is composed of galvanized steel and bronze. The installation of the cables in the well depends on the types of insulations it can be installed in wells with temperatures more than 300 F. The pump’s motor determines the number of wires needed to make an electric cable. Like, there will be three wires, two conductors, and a third green ground wire in a two-wire pump motor.

Check and Bleeder Valves

It allows fluid to travel in uni-direction like when the flow is in one direction the check valves prevent the flow in another way. Submersible pump applications require multiple check valves. If there is no check valve, the fluid flow can cause reverse rotation of the unit when the motor is off.

Each application has a check valve installed at the surface just after the pump. The second check valve should be installed less than 21’ above the main pump. The reverse rotation of fluid and speed depends on certain factors depth and size of the tube, type of pump, and tube restrictions. A bleeder valve must be installed with a check valve just above it to eliminate a wet tubing string.

Surface Equipment

Surface equipment consists of the junction box, transformers, and control panel. The control panels are designed to withstand any weather conditions and are available in a different range of sizes. These control panels vary from simple units with magnetic push-button and overload protection to more complexities with ammeter recording, overload and underload signals lights, and devices for automatic remote control.

Safe Installation of Submersible Pump

Installation of a submersible pump is a challenging physical task because the pump, wires, and piping need to be lowered to the depth of the well. The persistent issues associated with the submersible pumps often cause severe problems. Proper installation of pumps is necessary as they are installed in wells, tanks, and pits, and access to them is difficult. Ten complete lessons must be considered during the installation of submersible pumps.

Cautions in Lifting and Lowering the Pump

Lifting or lowering a submersible pump involves two things: a galvanized steel pipe made at home and a well-fitting called pitless adaptor. The half lower part of the adaptor is permanently mounted with the help of a hole bored in the side of the metal well.

While the other half is connected to the black polyethylene pipe that goes down to the well, the top end of the pitless adaptor is threaded, allowing the T-shaped piece of diameter 11/4 steel pipe to be lowered into the well threaded into the pitless adaptor.

The movable portion of the adaptor creates a 90-degree waterproof connection while sliding down. To remove the pump and waterline, the sliding part of the pitless adaptor must be separated up and out of the well, and this action needs a homemade galvanized steel pipe.

This pipe is about six-foot lengthy and has 11/4 diameter with a tee on the top and two handle pieces, into the hole in the top of the pitless adaptor, the bottom end of the tool thread, which allows the pulling it out and up quickly.

Preventing Electrical Accidents and Injuries

It is essential to shut down all energy sources before installation. There is thermal overload protection in many submersible pumps that restarts the overheated pump automatically. It must be ensured that the electric power should be cut before working on the pump.

OSHA reports that about 50,000 injuries are prevented each year by following proper procedures. There is always the risk of falls around the wet wells and other tanks, and proper procedures and measures should be considered while working around wet wells, especially during winters. These methods and procedures include railing, body harness with lanyard, and access cover with nets and cages.

Protection of Wires

One of the reasons that cause the failure of the pump is the improper protection of the pump’s wires. Sometimes, the insulation around the pump wires gets worn due to the movement against the inside of the metal. Because of torque inside the motor, the whole installation moves, and at the end of fifty, hundred, or two hundred feet of pipe, the pump stops and starts hanging.

Over time, the wires of the pump become thin, exposing bare copper and creating a short circuit that causes the non-functioning of the pump.

Another problem is related to motor torque which is caused due to the twisting force of the motor starting. Thread of pipe twists tighter and tighter, wrapping the wires around the poly pipe until it breaks. In the wet environment of the well, there is always the danger of crimp-on wire connections failing and corroding. To prevent this, those wires should be used that occur inside the casing

The length of the wire attached to the motor should be considered; the submersible pump comes to form the factory with a continuous length of the wire. But this length is generally not enough to get to the top of the well. Therefore, it is important to splice additional wires onto the installation before the pump gets down. Still, soldering these wire connections makes good sense.

Prevent Installation of Pump on Loose and Soft Bottom

For the long-term operation of the pump, it is usually advised that the pump must be installed on a base elbow with a rail system. The installation of the submersible pump on a solid mount and foundation is not only good for the long-term health of the pump but is necessary for the long-term operation of the pump.

The rail system helps in the pump’s discharge, and each rail system consists of a rail adapter. The rail adapter is designed so that it slides down the rail and interlock the rail to the base elbow. The base elbow should be anchored securely, and stainless steel anchor, hardware, and rail must be used. An intermediate rail or adapter should be used to keep the rails aligned in those wells where the length is more than 20 feet.

Make sure to take up all the slacks on the pump cord, and they must be restrained tightly to prevent them from being sucked into the pump. The basin and pit must be capable of holding the weight of the pump and rail.

Consideration of Check Valves

Check valves are often overlooked during the installation of the submersible pipes, as check valves allow fluid to travel in one direction and prevent the reverse flow of the fluid. They boost the reliability of the excellent system. Check valves boost the reliability in two ways when spliced into the intake lines.

Firstly, these check valves prevent the reverse flow of the fluid when the motor is not working and thus eliminate the unnecessary physical strains on the pump.

Secondly, the check valves immediately start fluid flow into the tank when the pump starts working. The check valves can not be removed as they contain a flap of the brass inside, which makes a slight clicking noise when they start working. These valves provide a greater flow of fluid than silent spring-activated valves. Before the fluid reaches the pressure tank, these valves must be installed before the pipe enters the house.

Checking of Rotation Before Operating the Pump

Sometimes, the pump is accidentally installed so that the impeller runs backward. It frequently occurs during installing a new pump or motor, changing the stator, or substituting a VFD.

The rotation should not be checked by placing hands in the pump suction because it can cause severe physical injuries. To check the rotation, the professionals run a “bump test.” They quickly turn on and off the pump to check the rotation of the motor and impellers in a bump test.

The rotation of the impellers must be in a counter clockwise direction. To achieve this, a three-phase motor having an electrician switch must be connected to any two power leads to correct the rotation. The pump will always generate the flow of fluid irrespective of the rotation of the impellers. Therefore, the pump must be installed to generate less flow and power.

To Follow Certain Tricks During Lowering of Pump

There are different ways to successfully get the pipe, pump, and wires into the well; getting them in one piece is difficult, but there are certain tricks to do it very quickly.

First of all, the well’s casing is sharp, so to protect the pipes and wires, the sharp burr must be granted. Like, a plywood donut with an inner rounded edge must be used on the top of the well. It will help erase the pressure on the pipe, and the kinking will be avoided easily.

Similarly, the T-handle of the pitless adapter must be put and tied to the end of the poly rope to the safety lug of the pump. Two people should direct the pipe ahead, and the third should direct the top end of the pipe and the T-handle. Tie the end of the rope to the inner of the good cap after mashing the two halves of the adaptor and at the end, fasten the outer well to cover everything.

The Pump Should Not be Lifted With the Help of an Electric Cord

the pump and cable can be damaged when lifted, hanged, or carried by the electrical cord and ultimately can cause shock and burn. Instead of lifting the pump by an electric cord, it can be lifted or hanged by lifting points specially designed for this purpose. Moreover, special chains and gear attached to the specific locations on the pump can be used.

Checking the Fluid Level When the Pump Gets Cool

After becoming hot, the fluid may be under tremendous pressure, and in this case, the plates, covers, gauges, and pipe plugs should not be removed from the overheated pump. Inside the pump, the vapor pressure may cause the ejection of certain parts with great force. The pump must be allowed to cool completely before providing service.

Water-tight Connection

A good pipe must be used well system; for this purpose, black polyethylene pipe is most suitable, but for screw clamps, the pipe needs to be heated and softened with the help of a propane torch before tightening the screw clamps. Two clamps per joint should be used to install the pump safely and use stainless steel ones. Moreover, a small socket wrench or nut driver can also tighten the clamps.

Maintenance of Submersible Pump

to keep it operating and safe, submersible pumps must be maintained regularly. A typical submersible pump lasts for ten years, but it can last more than that with proper maintenance and repair. Moreover, careful treatment of the submersible pump can increase its time duration and durability. The submersible pump needs the following tips to maintain the pump:

Lubrication of Submersible Pump as Directed

Manufacturers give guidelines for the lubrication of pumps and motors, so they should be lubricated as directed by the manufacturers. Everything has a limit, and a pump with a motor should not be lubricated more than the required limit because it will harm the pump’s bearings. Furthermore, Detaching of the cap should be considered before starting the pump.

Regular Checking of the Pump

Usually, caring and maintenance of the submersible pump are generally ignored by people. The pump often runs for an extended period without being checked. These pumps need to be inspected constantly and frequently for long-term working and performance. Inspection of valves, gears, seals, wires, and motors must be done frequently. Thus, it is essential to check the pump constantly.

Inspection of Motor

The motor is one of the essential components of the pump. Therefore, the pump’s motor should also be checked constantly. The contractor or starter need needs to be checked for overheating and arching. Moreover, the motor should be kept far from dust and wind’ dirt. Thus, the submersible pump motor also needs frequent observation and inspection.

Prevention of the Pump

The water or fluid helps in the cooling of the pump. Overheating of pump occurs is due to insufficient supply of fluid in well or a low level of fluid or water inside the well. The same overheating of the pump can be caused when the pump fails. To prevent the pump and the motor from severe damage, the heating of the pump must be checked frequently.

Removing Dirt and Debris after Using

A pure water flush is necessary to eliminate dirt and debris from the pump because the length between the impeller and the diffuser is less in these types of pumps. Similarly, the flow rate of the fluid and the pressure increase in these pumps. So, for the constant working of the pump, a pure water flush is necessary.

Replacement of Damaged Seals and Hoses

Damaged seals and hoses must be replaced immediately with a new one. Use temporary greases to avoid leaks and slips.

 De-rusting of Submersible Pumps

These pumps are in contact with water or other fluid for a long period, and they are prone to be rusted after being used. Pumps are inspected each year to remove the rust, and after this, anti-rust paint is applied to the pump’s products.

Storage of Pump

If there is no use of the pump for a short period, for instance, in winters, these pumps need to be lifted from the well and kept in the place of low humidity or dry environment. Water stains should also be removed to prevent corrosion.

Apart from the above tips, the insulation resistance should be assessed frequently before using the pump. All safeguards should be checked appropriately. Most importantly, the fluid should be recycled if possible.

Applications of Submersible Pump

Different types of submersible pumps have different applications and functions. There are several applications of submersible pumps, but the most important are:

• Used in the deep wells which cause shaft problems.
• These pumps are even installed in those wells where the motors frequently damage.
• In those locations where quiet operation is required, these pumps are used as booster pumps.
• Submersible pumps are even installed where there is less floor space for the unit.
• Sometimes, they are installed horizontally in pipe-like horizontal pipeline booster pumps.

As discussed earlier, applications of pumps depend on the type of the pump. Different types of pumps with their applications are mentioned below:

Single Phase Centrifugal Pumps: These are commonly used worldwide. These pumps work simply, and the impeller rotates on its horizontal axis at about 2500-5000 RPM. These types of pumps are suitable to pump clean liquids.

Multistage Submersible Pumps: With the last stage impeller, these pumps are usually used in high-pressure applications. These pumps are more complex than others, but these pumps are frequently used in medium to large unpressurized reservoirs where high maintenance of medium to long-term operation is required. However, the multistage submersible pumps are not suitable to lift water.

Slurry Pump: These pumps are highly equipped with impellers that are wear-resistant and wear-plates and resistive liners to handle slurries that contain solids and can damage the pump. These types of pumps are found in gas mining industries and reservoirs applications.

Multistage Centrifugal Pumps: These pumps have the highest pressure at the discharge of the first stage impeller. One can find these pumps in reservoirs applications or water supply pumping stations. It is also unsuitable for lifting water but can be used where long-term operation without maintenance is required. Apart from these applications certain things should be kept in mind for submersible pump applications and these are the following:

• All installation materials should be read thoroughly.
• The pump should be examined to check for any visible damage. 
• On the top of the discharge line, a check valve must be installed.
• The manufacturer must be consulted for any questions.
• All instructions, information, and receipts should be kept safely for future use. 

Similarly, these pumps are used in irrigation, wastewater, sewage treatment, and sump pumping to pump liquid in a particular area.

Advantages of Submersible Pump

A submersible pump is a type of pump which is designed to move liquid from one place to another while it is completely submerged in the liquid. Many advantages of a submersible pump can be derived from being submerged in the liquid. This pump is completely sealed so that no liquid can enter inside the pump.

Simple and Portable: These pumps are simple, small, and light, making them portable quickly. Mostly, they have a handle and can be carried to any place without any difficulty.

Pre-primed: As submersible pumps are entirely submerged in the liquid, they are already primed and need no priming, saving a lot of money and costs. The maintenance is generally not mentioned if a pump that needs priming is run in a dry condition.

Usage with Pressure Pumps: Generally, a pressure pump needs a good water supply, and the submersible pump provides water for a pressure cleaner.

Resistive: A submersible pump effectively presents resistance to the damaging effects of submerging in any liquid medium. These pumps are highly resistive to corrosion and abrasion because they are hermetically sealed and made from highly resistive materials, like stainless steel. Moreover, these materials can not be oxidized by oxygen and humidity.

Efficient: This pump does not spend any larger energy to move water from low level to high because it is already submerged inside the liquid medium that needs to be pumped. Thus, the pump does not work hard to lift liquid, which helps its longevity.

Electrical Pump: These pumps are electrical and need only a connection to electricity to run. Mostly, submersible pumps come with long power cards to ensure that you always have access to electric power.

Versatility: These pumps are used for many purposes. Specific pumps operate while they are half-submerged. Similarly, some of them are designed to handle sewage and other solids as well.

Occupying Less Space: Many other pumps usually occupy large space and can cause hindrance during installation, but submersible pump occupies less space, and hence they are space-saving. These types of pumps take no extra space.

Less Noise with Maximum Flow: Since these pumps are completely submerged inside the liquid medium and produce less noise than the pump that operates in the open because the liquid absorbs most of the sound, apart from this, it provides a maximum flow of the liquid.

Safety: Submersible pumps are submerged in the liquid, making it safer and less dangerous to around people. A board over the pump can also conceal it more efficiently.

Disadvantages of Submersible Pumps

Apart from benefits, submersible pumps have a set of drawbacks as well. Even though these pumps provide many benefits, there are still some downsides.

Breaking of the Seals: As it is already clear that these pumps are entirely submerged in the liquid, this can cause a faster seal breakdown than a non-submersible pump. Because they are openly exposed to the water or any other liquid, the seal does not last for a long period.

Overheating: When these pumps are not entirely submerged in the liquid or water, these pumps may overheat, and for this reason, they should constantly be and frequently monitored to make sure that the liquid level does not drop so low to show the pump. Otherwise, there is a chance that the motor burns out or stops working.

Horizontal Operation: Generally, these pumps are entirely submerged to deal with the noise, but this can cause the wearing out of the pump very quickly.

Difficult Access: When needed to be repaired or need other servicing, these pumps would be difficult to reach and would require an experts diver to go down the lake or other crane power to lift the pump to the surface.

Leaking and Ruptures: It is one issue associated with the complete submerging of the pump. Ruptures and leaking gaskets are hard to find due to submerging nature of the pump. If the pump is part of an irrigation system, variations in water flow and pressure caused by any mechanical failure will be repaired by the system itself. But, the issue of repairing the unit is still there as the unit is submerged in the liquid.

Dirt and Debris: The pump can take debris like vegetation, animal wastes, and silt present in liquid or water. The amount of debris can be built to such an extent that it can cause damage to the motor can block the pipe or the heads of the sprinkles that are used.

In addition to debris, some submersible pumps may deal with a high amount of calcium present in any liquid, especially in water that will cause the blockage of the pump and will eventually stop pumping the liquid out of the well.

High Cost: One disadvantage of the submersible pump is that it may cost high compared to other non-submersible pumps. However, when these advantages and disadvantages have been weighed, the advantages of the submersible pumps often win out.

Conclusion

A submersible pump is a device that pumps liquid from the region of low level to high level. Firstly, it is successfully installed in the oil field, and then it has been frequently used worldwide since that time. To operate correctly, it must be entirely submerged within the liquid that needs to be pumped.

In submersible pumps, the motor is closely coupled and these pumps first convert mechanical energy to pressure energy. Primarily, all submersible pumps work on the electric submersible pumping principle. These pumps have components, including the electric motor, centrifugal pump, and seal section.

During installation, different lessons and tips must be followed, such as caution in lifting and lowering the pump, preventing electrical accidents, etc. To maintain the pump’s proper functioning, the pump must be lubricated along with regular checking of the pump. Similarly, the motor must be inspected regularly, and also after regular intervals of time, these pumps need de-rusting.

These pumps have different applications, such as in it is frequently used in the water irrigation system and sewage water treatment system. Moreover, their applications always depend on the type of pump. Along with different advantages of these pumps, such as being easily portable, light, and efficient, these pumps have a set of drawbacks as well, like rusting and being challenging to access.