What is a sewage pump?
This sewage pump is a pump that is used to remove wastewater from the residential sewage basin and transfer it to the sewer system. A sewage pump is a pump used in residential areas for transferring soft solids of around 2 inches in diameter. The sewage pump works in different modes that is a manual, automatic, or dual mode of operation. During installation, the sewage pump is usually placed at the lowest point on the sewage basin from where it pumps the waste to the septic tank or sewer system.
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How does a sewage work?
Whenever a toilet is flushed or something is washed and that water flows down the sink, sewage (wastewater) is created. In a nutshell, sewage products come from homes, industrial and commercial buildings where water is used in bathrooms and kitchens. The sewage flows through pipes that are attached to toilets, bathtubs, and sinks from where it runs into the sewer system.
Sewage pump Types
Submersible sewage pump
A submersible sewage pump is a pump that can work without directly being dived in the water. The working principle of the submersible sewage pump is the same as that of a general centrifugal pump. Centrifugal pump works by use of its impellers to create a vacuum. Vacuum is a condition in which the pressure in a certain area is lower than the atmospheric pressure. Due to the vacuum in the pump, there will be more energy on the sewage that helps to transport the wastewater. This type of sewage pump consists of three main parts which are impeller, submersible motor, and pump body. The motor shaft and the pump are connected on the same shaft. The pumping part is placed at the lower end of the submersible sewage pump to make maximum use of the suction of the surface sewage. This type of sewage pump is known for its compact structure and convenience in its maintenance and installation making it suitable for conveying sewage to the sewer system and treatment plant. Submersible sewage pump manufacturers use single-blade impeller or double-blade impeller when implementing this type of pump. Either the single-blade or double-blade structure enables a submersible sewage pump to enhance its ability to transfer sewage. Some sewage pump manufacturers make submersible sewage pumps that have shredding or mixing abilities enhancing their potential to handle solid particles. The submersible sewage pump is designed with a seal made of corrosion-resistant and hard material such as tungsten carbide. The submersible sewage pump can be installed by use of two different methods that is by use of mobile free installation or by use of fixed coupling installation method.
Figure 1: Submersible sewage pump with its electrical cable and outlet pipe not connected.
Inline sewage pump
An inline sewage pump is also known as a straight-line pump. These pumps are from the type of pumps known as centrifugal pumps that have their suction and discharge oriented straight to the piping system. In inline sewage pumps, the sewage flow does not change. The inline sewage pumps have a relatively small size which makes them need small floor space compared to other sewage pumps. Inline sewage pump employs the principle of gravity-fed sewage directly from the entry point. Inline sewage pumps combine the characteristic of the basic water pump. However, inline sewage pump manufacturers design this pump in a way that it can drain long fibers and solid particles a principle that makes it suitable for pumping sewage. Inline sewage pump design employs impeller structure and seal that helps to effectively contain solids and fibers being conveyed.
Figure 2: Inline sewage pump structure.
Inline sewage pumps employ centrifugal force when moving fluids from one point to another. Inline sewage pumps are preferred because of their unique design that helps to save space. Inline sewage pumps are commonly used in building applications where space is limited and thus help eradicate drawbacks associated with space. Inline sewage pumps have a lower net positive suction head required (NPSHr). The inline sewage pumps allow components to flow through them with ease as they require less amount of suction pressure. Inline sewage pumps can work at relatively higher temperatures as well as higher pressure because the sewage pump manufacturers make these pumps with the ability to withstand thermal expansion.
Vertical sewage pump
Vertical sewage pump are vertical axis centrifugal pumps or mixed flow pumps with stages of rotating impellers and bowls. The vertical sewage pumps get their power from an AC electric motor or diesel engine. In vertical sewage pumps, several impellers can be used with various configurations with the shaft to enhance high pressure. The vertical sewage pumps work when fluid flows through it at the base via a suction bell. Next it moves to the main stage impeller where it raises the velocity of flow. The medium transported then enters into the diffuser converting the kinetic energy of flow to high-pressure energy.
Figure 3: vertical sewage pump.
Vertical sewage pumps are also known as vertical shaft or vertical column sewage pumps. The vertical sewage pumps are manufactured with their source of power for example motor being separated from the sewage being pumped. Vertical sewage pumps have bearings support that helps to reduce radial forces that could make the pump whip due to rotating force at the shaft end. Some vertical sewage pumps are designed with a single impeller stage to enhance high flow and low-pressure applications. However, in the market, there are vertical sewage pumps that are manufactured with multistage impellers to enhance low flow and high pressure.
Advantages of sewage pump
The inline sewage pumps can be used with high-speed drive systems. Inline sewage pumps can use prime movers that can produce high speed such as electric motors. When the inline sewage pump needs to match some constant operating conditions, then the drive system can be used without the need for costly speed reducers.
Inline sewage pumps are simple to operate. For the inline sewage pumps, an operator who is still in training can operate inline sewage pumps. This is because its construction employs simple making it easy to use and simple to operate. Also, when an inline sewage pump has been operated improperly, it can still work without serious damage, unlike other sewage pumps.
Inline sewage pumps are designed to operate at a certain pressure. The inline sewage manufacturers do make the pumps with a predetermined maximum pressure and according to their design, they cannot exceed this maximum pressure.
Inline sewage pumps are easier to do maintenance. Inline sewage pumps have long intervals of maintenance because it has few parts that experience wear. The design and construction of inline sewage pumps enhance its operation to have a long life span. This happens because it has few moving parts that have been constructed with large tolerance which helps to minimize wear.
Inline sewage pumps require small space. Inline sewage pumps are small in size and thus their installation will as well require small space for installation relative to other sewage pumps.
Inline sewage pumps have few moving parts. Inline sewage pumps are manufactured with few numbers of parts that move relative to each other when compared to other sewage pumps. This reduces the cost of constructing inline sewage pumps as well as the cost of doing repairs.
Submersible sewage pumps are easy and convenient to pump sewage.
Submersible sewage pumps are strong enough to handle solid particles which are inevitable in sewage.
Submersible sewage pumps have high efficiency and save energy which makes them economical for large-scale use.
Submersible sewage pumps are more effective in pumping sewage because they employ the suction method that uses direct pressure to create pressure energy.
Submersible sewage pumps do not need to be primed before their operation.
The flow rate in vertical sewage pumps are known to be stable, even and they can be adjusted easily.
Vertical sewage pumps have few parts that face wear and tear.
Vertical sewage pumps need less space for their installation relative to other pumps.
Vertical sewage pumps can be used to work in fluid with pressure and temperature.
Disadvantages of sewage pump
Some of the sewage pumps need priming for example the inline sewage pumps. These pumps need to be installed in a way that will help them to prime themselves unless the impeller and casing have some fluids.
Sewage pumps with air leakage have low pump capacity. Leakage in sewage pumps reduces the predetermined pressure and thus results in low-pressure energy for transferring the sewage.
Sewage pumps such as inline sewage pumps have specific operating speeds. When the speed of the inline sewage pump needs to be reduced, one is required to have a speed reducing mechanism otherwise it will not be possible to reduce the speed directly on the pump.
Sewage pumps such as the vertical pumps that run on the principle of centrifugal pumps have a risk of running backward. This can happen when the pump is stopped without first closing the discharge line because they are not manufactured with elements that can halt flow in the backward direction.
Some of the sewage pumps have a narrow range of efficiency. The efficiency of the sewage pump depends on the heat capacity. The efficiency becomes high when the pump is working on a range of a short head capacity.
Submersible sewage pumps may experience leakages due to the tear and wear of seals. The wear could as well result in motor corroding. Corrosion of the motor would mean that the pump will fail and thus causing the need for repair.
Submersible sewage pumps when not properly submerged they tend to overheat which could then result in its damage.
Submersible sewage pumps are more technical in their design making them more expensive when compared to non-submersible sewage pumps.
Vertical sewage pumps are sensitive to change their performance according to the fluid viscosity.
Large multistage vertical sewage pumps need barrel and pit which is expensive to build.
Vertical sewage pumps find it difficult to handle components with dissolved gases. This could later damage the pump seal.
Sewage pump application
A sewage pump is manufactured for use in removing water that builds up in basements and then depositing it safely through the sewage system of a building. These pumps are also meant to transport untreated wastewater. Sewage pumps are mostly used in urban wastewater transport. They are also used in private homes and buildings that are not connected to municipal sewers due to the nature of the terrain.
Sewage pump troubleshooting
Just like other machines, pumps do experience technical problems. Some of the criteria’s that can be followed to determine the cause of a technical problem in a sewage pump are:
- Very high total head. In this case, shortening the head and or suction will resolve the problem.
- When casing was not initially full of fluid. In this case, the casing needs to be filled with fluid.
- Damaged impeller. This problem will need to replace the impeller.
- The motor is not wired properly. For this case, the wiring diagram needs to be checked and the wiring corrected accordingly.
- Leakage of air in the suction line. When this problem occurs the suction line needs to be replaced.
- Motor overheating. When the pump is overloaded the motor overheats and consequently it shuts off. This will need the motor load to be checked to ascertain it is according to the manufacturer’s specifications.
- Motor voltage is not matching the voltage power supply. In this case, the wiring diagram needs to be checked against the voltage power supply.
- The pump could have problems due to worn-out mechanical seals. As such, the mechanical seals need to be replaced.
- The pump could not be pumping well due to a loose foundation and this would need to be reinforced.
From this article, it can be seen that sewage pumps as the name suggests are used for transporting sewage to the treatment plant. Sewage pumps have advantages and disadvantages. However, the advantages outweigh the disadvantages by a great margin. A pump is a machine that provides mechanical energy to fluid making it move from one place to another. Sewage pumps are primarily designed to help in transporting sewage from residential areas to the treatment plant. The three sewage pump types considered in this article are the submersible, inline and vertical sewage pumps.