Submersible Sewage Pump
Submersible Sewage Pump
What is submersible sewage pump?
This is a pump that is used to transport sewage and untreated waste water. This pump is used in municipal waste water treatment as well as private homes and buildings. As the name suggests, this pump operates while it is submerged in the fluid being pumped. As such, submersible sewage pump manufacturers ensure the design is airtight to ensure the waste water cannot get into the electrical components to cause electrical faults. The design of this pump is usually made of strong materials such as stainless steel to ensure they are able to withstand fluid pressure and also resist corrosion. They are also made of plastic material which are reliable in resisting against corrosion. This pump is one of the centrifugal pump as its operation depends on rotation of impellers at very speed. This rotation is meant to suck the fluid into the pump and impart kinetic energy into the fluid. Their design is special as they can allow solids to pass through them without causing blockage.
Figure: Submersible sewage pump
Components of a submersible sewage pump
The motor is the source of power in a submersible sewage pump. The electrical energy to run the motor is transmitted from the mains supply to the pump through an insulated wire cable. The motor operates by converting that electrical energy into mechanical energy. The mechanical energy is needed to rotate pump impellers to create energy needed to transport the sewage.
The shaft is the part that transmits mechanical energy from the motor to the pump impeller. The mechanical energy is transmitted in terms of torque and rotary speed (angular speed).
The impeller is one of the main elements of the pump which is used to enhance fluid flow from the sump to the required destination. It operates by rotating at very high speed which leads to a vacuum in the pump and thus forces fluid to move inside the pump. The impeller then imparts a lot of energy on the fluid while it is rotating at its high speed.
The casing is the component that houses internal parts of the pump like impeller, shaft, seals, and bearings. Submersible sewage pump manufacturers design the casing such that it helps to reduce the fluid’s energy imparted by the impeller while it increases pressure energy at the same time. This pressure energy is the one needed to move the fluid to the required location.
Bearings are used to support the pump and motor shaft rotation. They also help to ensure smooth operation without vibration and noise while keeping the shafts properly aligned. Submersible sewage pump manufacturers design the pump with lubricant storage space inside the pump to ensure the bearings are always lubricated to prevent overheating and premature wear.
This is the part of the pump uses to house all the parts of the pump including the casing. This cover is air tight to ensure no fluid can get into the pump and thus prevents pump malfunction.
How does a submersible sewage pump work?
Submersible sewage pumps operate by pushing the fluid to the surface. The ability to push the fluid is actualized by the electrical motor. The pump is usually fully submerged in the liquid being pumped. When the pump is turned on, motor rotates the impeller at very high speed. This impeller rotation creates a vacuum inside the pump which forces the fluid to enter the pump via the suction port into the impeller eye. The impeller has blades on which the liquid hits when it enters the pump. As the fluid hits the impeller blades, it gets more kinetic energy added into it as it enters the casing. In the casing/diffuser, the kinetic energy is reduced by reducing fluid speed while the pressure energy is increased as it proceeds to the discharge port. With such high pressure energy, the fluid is capable of moving to the desired destination. As such, submersible sewage pumps operate by pushing the fluid to the surface.
Figure: Submersible sewage pump
Types of submersible sewage pumps
Effluent submersible sewage pump
This is one of the most common sewage pump used in small sewage sites. Submersible sewage pump manufacturers design this pump for transporting effluent flowing from septic tank after it has settled to avoid solid particles. Since the solids settle in the septic tank, the effluent has become a relatively clear liquid. As such, the pump will transport the liquid without sewage solids making it operate at higher efficiency and with minimal breakdown.
Solid handling submersible sewage pump
This is a pump designed with features that make it suitable for handling raw sewage. Raw sewage has a lot of solids and thus this special pump is for handling such.
Grinder submersible sewage pump
These blades are meant to cut and grind the solids into small pieces before pumping the sewage. Such type of pump is very reliable as it rarely gets blocked by large sized sewage solids. As such, this pump can be used to transport both effluent and raw sewage. Grinder submersible sewage pumps are designed with cutting and grinding mechanism that ensures the pump is capable of chopping hard solids into tiny pieces. This leads for formation of slurry that is easy to pass through the pump and transporting pipeline. Since the slurry is fine, it becomes very easier to pump at high elevation than with ordinary sewage pumps. As such, this type of submersible sewage pump uses more power and it is also more expensive. Due to the power needs and cost, submersible sewage pump manufacturers recommend this pump for use in commercial and institutional applications. However, despite this pump being made for grinding hard solids, it is recommended for handling only solids from toilets. Using it for other hard solids is likely going to destroy it. Due to this pump being powerful, it can multiple homes or restroom facilities can be connected to be served by one grinder submersible sewage pump which will help reduce the cost of installation and maintenance. Submersible sewage pump manufacturers design some of these pumps with alert system. When the pump malfunctions, the sewage level raises up beyond a particular point which forces the alert system to notify the user to take action. The level of waste water is determined by use of a floats or sensors that come with the pump..
Stainless steel submersible sewage pump
This is a pump made of stainless steel material. This pump is very strong and thus suitable for handling high fluid pressure. The stainless steel material is also resistant to corrosion making the pump safe against corrosive properties of sewage. However, this pump is quite expensive due to high cost of stainless steel material and machining process.
Plastic submersible sewage pump
This is a pump made of plastic material. Plastics are off lightweight due to low density making the pump also light. This pump is also very good for sewage since the plastic material is excellent in corrosion resistance. In addition, this pump is cheaper compared to the metallic ones due to low cost of plastic materials.
Multistage submersible sewage pump
This is submersible sewage pump designed with two or more impellers. These impellers are of the same or different types. This pump is designed with diffusers that help to channel the waste water efficiently into the impeller eye or to the next stage. Submersible sewage pump manufacturers also include a thrust balance device in the pump. This device helps to reduce level of thrust which is very high in multistage pumps due to the multiple impellers oriented in the same direction. This pump operates by having the first impeller feeding the next impeller until the fluid leaves all the impellers into the casing. The number of impellers used in the pump depend on the discharge pressure required. The more the number of impellers the more the output pressure energy and thus the larger the load the pump can work on. However, this pump is more expensive compared to the pump using one impeller.
Single stage submersible sewage pump
This is a submersible sewage pump that operates using one impeller. This is the most commonly used pump. It is preferred because of low initial cost, small in size, and less power consumption, simple in structure, stable in operation, and easy to maintain. However, this pump’s discharge pressure energy is lower compared to the multistage pump type.
Applications of submersible sewage pumps
- They are used to transport raw and effluent sewage.
- They are used in waste water transfer and treatment.
Advantages of submersible sewage pumps
- Submersible sewage pumps are of simple structure.
- It is fully covered making it safe against waste water.
- It is easy to operate.
- It is versatile in size making it suitable for handling various levels of loads.
- Submersible sewage pumps prevent problems arising from cavitation.
- These pumps do not need manual priming since by being submerged in the waste water it gets primed.
- These pumps are able to handle slurries and liquids.
- It operates quietly.
Disadvantages of submersible sewage pumps
- By being submerged deep in the ground makes it hard to inspect and repair the pump.
- If the pump cover integrity drops, it starts leaking. Leakage of waste water into the pump internal parts will damage the pump.
- It is expensive compared to other pumps because of its high strength and water proof integrity.
Troubleshooting submersible sewage pump
Pump does not operate
- Pump power cable is not connected to the power supply or they have poor contact. Check the pump cable connections for tightness.
- Motor overload tripped. Give the pump around 10 minutes and reconnect.
- Motor voltage is very low. Check line voltage is as recommended by submersible sewage pump manufacturer.
- Blocked impeller. Disconnect the power supply and remove the pump from the sump. Then clean materials blocking impeller and volute.
- Damaged bearings. Disconnect the pump power supply and remove the pump from the sump and check for bearings status. Lubricate the bearings and if damaged replace them.
Pump delivers zero liquid or low discharge
- Impeller is loose on the shaft. Remove the pump from sump (disconnect power) and tighten impeller as instructed by the submersible sewage pump manufacturer.
- Damaged or clogged impeller. Clean the casing interior and remove any impeller blockage. If the impeller is damaged replace it.
- Clogged suction line. Remove materials blocking the suction line.
- Discharge pipe blocked. Open the pump and clean off blocking material.
- Inoperative, defective check valve or installed wrongly. Check the check valve and ensure it faces the direction of flow as instructed by the submersible sewage pump manufacturer.
- Improperly sized pump. Replace the pump with larger pump that can manage the required load.
Pump is noisy
- Loose impeller. Disconnect power and remove pump. Tighten the impeller.
- Worn out bearings. Replace bearings.
- Loose shaft coupling. Tighten the shaft coupling.
Pump stops after operating for a short time
- Motor overload tripped. Give the pump 10 minutes to cool and reconnect. If it trips again consult electrician or power company to check the circuit voltage.
- Internal motor defect. Check the motor winding, power cord damaged or open, or defective thermal overload.
- Very high voltage. Call electrician or Power Company to repair the circuit.
- Very low voltage. Check line voltage is as recommended by the submersible sewage pump manufacturer and if not, call electrician to repair.
Submersible sewage pump is a pump designed to operate while it is fully submerged in waste water sump. This pump is designed with air tight cover that ensures no amount of fluid gets into the pump. Any fluid getting inside the pump damages electrical components rendering the pump useless. This pump operates by pushing the fluid to the surface. It uses centrifugal force which is created by the impeller rotating at very high speed. The impeller rotation creates a vacuum in the pump which forces the waste water into the pump. The fluid gets more energy on the impeller. The kinetic energy is then reduced in the casing as the pump tries to increase pressure energy used to move the liquid to the required destination. Submersible sewage pump manufacturers produce various types of pumps which include grinder pumps, solid handling pumps, effluent pumps, stainless steel pumps, plastic pumps, multistage pumps, and single stage pumps among others. Advantages of these pumps are simple structure, easy to operate, safe against waste water, various sizes, operates quietly, and are able to handle slurries.