Submersible Grinder Pump
Submersible Grinder pump
What is a submersible grinder pump?
A submersible grinder pump, also called a wastewater machine, contains a powerful integrated grinding mechanism, and it is designed to be fully submerged in the pumped liquid. The submersible grinder pump manufacturers tailor the pump to chop larger solids into smaller pieces, allowing them to pass through the pump without clogging. The grinding mechanism enables the pump to discharge effluents economically and reliably under pressure. One can connect a submersible grinder pump to a holding tank in residence via pipelines. The pump automatically activates when the wastewater in the tank reaches a certain level, grinds the waste into a practical solution, and then discharges it into a septic tank or central sewer. A submersible grinder pump mainly applies to pumping unclean water or effluents, such as wastewater from bathtubs, washing machines, and home toilets. Submersible grinder pumps are also excellent for high-pressure sewage systems, large yards or basements, and locations where the terrain does not allow gravity sewers.
Figure: Submersible grinder pump
Components of a submersible grinder pump
Figure: Components of a submersible grinder pump
The electric motor is the source of mechanical power to run the submersible grinder pump. It comprises stator and motor windings, a commutator, and a shaft sleeve. It works by converting electrical energy to mechanical energy, which helps to drive the pump impeller. An electric motor can be powered using direct current (DC) or alternating current. Submersible grinder pump manufacturers mostly fit the units with hermetically sealed AC induction motors.
The purpose of the motor capacitor is to store electrical energy and releases it to the copper windings, creating an extra boost and increasing the motor torque. The submersible grinder pump manufacturers select a capacitor based on the capacitance, voltage, physical size, frequency, and design temperature.
Pump casing (volute)
The function of the pump casing is to house the pump’s internal components, including the impeller and shaft, shaft seals, etc. It also helps to convert the fluid kinetic energy into a pressure head and to direct the fluid into the discharge connections. In general, submersible grinder pump manufacturers design the units with a volute casing to enhance their efficiency in handling liquids with larger entrained solids and highly viscous ones.
The primary function of mechanical seals is to create a water-tight barrier that helps to reduce leakage between the rotating shaft and the stationary pump casing.
The shaft is a cylindrical solid component made from stainless steel and rides on the bearings. Its primary function is to support the pump impeller.
The impeller contains a series of backward-curved vanes and is usually placed inside the volute and mounted on the pump shaft. Its function is to increase the fluid’s kinetic energy and pressure.
Suction inlet and discharge outlet
The fluid enters the submersible grinder pump through the suction inlet and exits through the discharge outlet.
How does a submersible grinder pump work?
When the submersible grinder pump is started, the pump shaft drives the impeller to rotate at high speed, forcing the liquid pre-filled between the blades to rotate. Under the influence of centrifugal force acting on the impeller, the pumped liquid moves radially and axially outwards from the impeller’s eye into the volute at a very high velocity. In the volute, the pumped liquid decelerates due to the gradually expanding flow path, and some of the kinetic energy converts into a static pressure head. The fluid is then pushed to the surface and directed to the required location via the discharge pipeline.
Figure: How does a submersible grinder pump work?
Types of submersible grinder pumps
Stainless-steel submersible grinder pump
A stainless-steel submersible grinder pump features a fully stainless-steel construction and is designed to operate below the surface of the pumped liquid. All the pump’s components coming into contact with the liquid are made from stainless steel to minimize corrosion. The pump is primarily used in the food industry to reduce food waste into a fine slurry. It is also suitable for handling corrosive and abrasive wastewater.
Figure: Showing the configuration of a stainless-steel submersible grinder pump.
Submersible sewage grinder pump
A submersible sewage grinder pump mainly applies to transporting wastewater containing a high percentage of organic solids. The pump can also effectively handle feculence-containing particles in public facilities and municipal engineering. Submersible grinder pump manufacturers avail the pump with a freestanding design or mounted on a guide rail for fixed installations.
Figure: Showing the configuration of a submersible sewage grinder pump.
Single-suction submersible grinder pump
In a single-suction submersible grinder pump, the fluid enters the pump impeller from one side. A single-suction submersible grinder pump allows the fluid in horizontally and axially and discharges upward and radially. This pump has a more straightforward design and is cheaper than the double-suction counterpart.
Figure: Showing a single-suction submersible grinder pump.
Double-suction submersible grinder pump
A double-suction grinder pump draws the pumped fluid from both ends of the impeller. Submersible grinder pump manufacturers design the unit with two back-to-back impellers, and the liquid from both ends converges into a volute. Double-suction grinder pump is free of axial forces on the impeller and can manage higher flow rates and a higher-pressure head than the single-suction counterpart. It can also last longer because it is less prone to wear and tear caused by the axial thrust of the fluid entering the impeller.
Figure: Showing a double-suction submersible grinder pump.
Applications of a submersible grinder pump
Submersible grinder pumps find uses in a broad scope of applications, such as municipal wastewater, commercial and residential buildings, food processing, high-pressure sewage systems, large yards or basements, water treatment plants, etc. Their main uses include the following:
- Submersible grinder pumps are used to dispose of wastewater from living units and houses in remote settlements where it would be too costly to install a conventional sewer line due to the nature of the terrain or where there are large ground undulations.
- They are also used for grinding industrial food waste into slurry for efficient pumping under water pressure.
- They are used to pump wastewater from various home sources into a central sewer system or septic tank.
- They are used for handling water containing a high percentage of suspended solids.
- Use for pumping wastewater in water treatment plants.
- They are used in factories, construction sites, and commercial facilities for wastewater drainage.
Advantages of a submersible grinder pump
- Submersible grinder pumps have robust construction, providing ease of installation and operation.
- They are non-clogging. The powerful integrated grinding mechanism enables submersible grinder pumps to chop down large solids that could cause clogging or blockage.
- They are self-priming since they operate while fully submerged in the pumped liquid.
- They are highly portable because the motor is close-coupled to the pump head.
- They can easily handle unclean water with suspended larger solids without damage.
- Submersible grinder pumps provide a long service life due to using non-corrosive material for pump construction.
- They have minimal maintenance requirements.
- It is highly energy efficient, reliable and easy to operate.
- They provide cavitation-free operation because they do not generate a spike in pressure as the fluid flow through the pump body.
- They have a high blowdown capacity.
- Ther are of various sizes for small and large flow rates.
Disadvantages of a submersible grinder pump
- Submersible grinder pumps cannot run dry and must always sit below the surface of the pumped liquid. The pump uses the surrounding water to cool the motor, and dry running can damage the pump due to overheating.
- They are prone to unnoticeable wear and tear, which may cause water to leak into the motor, causing pump failure.
- A submersible grinder pump may not wholly drain a holding tank in automatic mode because it must immerse in the pump.
- They are more costly to acquire than surface pumps because the submersible design is a bit more technical.
Troubleshooting a submersible grinder pump
The motor fails to start
- There are shortcomings in the motor wiring. Ensure the power cables connect correctly following the submersible grinder pump manufacturer’s manual.
- The motor is damaged. Disassemble the prime mover and inspect the windings and internal connections. If there are burn marks, the engine is likely blown out and needs replacement.
- The circuit breaker is tipped or fuse blown-out fuse. Inspect and reset the circuit breaker if necessary. Be sure to replace the fuse if it is blown out.
- The centrifugal fuse or capacitor has failed. Check the conditions of the fuse or capacitor and replace them if needed.
- There is a broken power cable. Inspect and change the wire if necessary.
Zero pump discharge
- The impeller is clogged. Clean the pump inside and clear any clogging material from the impeller.
- The pump does not automatically fill with starting liquid. Unblock the suction inlet.
- The discharge pipe is blocked. Disconnect the discharge line, inspect it and remove any blockage.
- The motor is running in reverse. Be sure to reverse the motor polarities. Check that the motor rotation direction matches the direction indicated by the submersible grinder pump manufacturer.
The pump’s flow is unstable
- The bottom valve is leaking. Inspect the bottom valve for leakage and correct or replace it if necessary.
- The power supply is too low, leading to a decrease in pump speed. Inspect the level of the voltage supply and adjust it accordingly.
- The impeller or seal ring is worn-out. Inspect the impeller or seal ring for wear and replace them if you find it fit.
The pump capacity is low
- There is a blockage in the delivery pipe. Inspect and clear any blockage from the delivery pipe.
- The suction inlet or impeller is partially clogged. Remove any build-up material from the filter and the impeller.
- The impeller is worn out. Inspect the impeller for wear and replace it if necessary.
- There is excessive clearance leading to fluid recirculation. Ensure that the impeller is of the correct size following the submersible grinder pump manufacturer’s guide.
The pump fails to develop pressure
- There is a leakage in the mechanical seals. Inspect and replace mechanical seals if needed.
- The pump cannot self-prime. Remove any blockage from the suction inlet so that the initial start-up liquid can freely enter the pump.
- The discharge line is closed, preventing the priming air from exiting the pump. Be sure to open the discharge line.
- There is leakage in the foot valve or check valve. Check the conditions of the valves and replace them if necessary.
The motor is overheating
- The motor is defective. Inspect the motor conditions, repair any fault or replace it if needed.
- There is a voltage spike due to a storm or lightning strike. Install the submersible grinder pump with an external surge protector.
- The pump is not fully submerged during operation. Ensure that the pump sits below the surface of the pumped liquid.
A submersible grinder pump is designed with an integrated grinding mechanism, and it operates below the surface of the pumped liquid. The submersible grinder pump manufacturers develop the edge-cutting unit to chop larger solids into smaller pieces, allowing them to easily pass through the pump without clogging. The grinding mechanism enables the pump to discharge effluents economically and reliably under pressure. Submersible grinder pumps mainly apply to moving wastewater from various sources, such as bathtubs, washing machines, and toilets in homes, to a central sewer or septic tank. They are also used to grind industrial food waste into slurry for efficient pumping under water pressure. They can be found in high-pressure sewage systems, food processing industries, water treatment plants, etc. Submersible grinder pumps are non-clogging, self-priming, and highly energy efficient. Submersible grinder pumps also provide long service life due to corrosion-resistant materials such as stainless steel and cast steel for pump construction.