Centrifugal Monoblock Water Pump
What is a centrifugal Monoblock water pump?
Centrifugal Monoblock water pump uses centrifugal force to move water. The pump has one shaft that runs from the motor to the impeller without a coupling. The shaft transmits power from the motor to the pump. Such a pump is preferred because it reduces energy losses which is common in pumps that use coupling. The pump uses one or more impellers to transfer kinetic energy onto the water. The kinetic energy is then converted into pressure energy needed to carry water to the required location. This type of pump is suitable for daily water transfer applications since it will save on electricity bills. Applications of this pump include mining, irrigation, commercial water supply, construction, and agriculture, among others.
Figure: Centrifugal Monoblock water pump
Components of a centrifugal Monoblock water pump
Motor
This component provides power to run the pump. The motor must be connected to the power supply for the pump to run. It converts electrical energy from the mains supply into mechanical energy. The mechanical energy is needed to run the centrifugal Monoblock pump for water to move to your destination.
Shaft
Centrifugal Monoblock water pump manufacturers machine the shaft from high-strength steel materials to make it able to withstand the high power needed to operate your pump every day. The shaft is a solid mechanical component that transmits mechanical power from the motor into the pump. A bearing on both ends supports the shaft.
Bearings
The bearings are mounted on both ends of the shaft that is on the motor and on the pump. The bearings support the shaft, impellers, and hydraulic loads due to water. The bearings also help reduce friction when the shaft is rotating. Also, by having bearings, the axial shaft movement and lateral deflections are kept within manageable limits.
Impeller
The impeller is a disc with curved vanes. It transfers power from the rotating shaft to the fluid being pumped as the water enters the pump. The water enters the pump and meets the impeller at its center, also known as the eye impeller. Two main types of impellers are the open impeller and the closed impeller.
The open impeller is designed with the blades open on both sides. This impeller does not have a protective cover. It is primarily used in small centrifugal Monoblock water pumps to avoid much stress. The closed impeller is wholly covered on its front end. It offers maximum resistance, and it is prevalent on large-sized water pumps. The closed impeller is preferred because of its ability to reduce axial thrust, which helps enhance bearing service life.
Figure: Centrifugal Monoblock water pump impellers.
Casing
The pump casing is an external shell meant to seal off the pump interior from the outside. Centrifugal Monoblock water pump manufacturers design the casing depending on the type of pump. The work of the casing is to prevent water leakage and keep pressure by sealing the pump interior against the atmosphere. The casing surrounds the pump impeller. The “pump” is contained in the casing. A centrifugal Monoblock water pump casing is for:
- Keeping water pressure in check.
- Allowing installation and removal of the impeller.
- Provide structural support or a structural link to support the pump.
- Keep the pump and motor aligned.
Three main types of casing are the volute casing, vortex casing, and casing with guide blades.
Volute casing. This type of casing has a continuous rise in the flow area. The fluid flow velocity reduces as the flow area increases. The water pressure through the casing increases as the fluid speed decreases. The volute casing is the most common type of casing. It is mainly used in single-stage centrifugal Monoblock water pumps.
Figure: Volute casing.
Vortex casing. This casing is designed with a circular chamber between the impeller and the casing. This casing has the advantage of improving pump efficiency by reducing production eddies during water flow.
Casing with guide blades. A centrifugal Monoblock water pump with a casing with guide blades has an impeller encircled by guide blades. The guide blades are attached to a diffuser ring. Centrifugal Monoblock water pump manufacturers design the guide vanes such that water leaves the impeller and enters the guides without causing shock. The guide vane’s area increases as the water flows to the discharge. This helps to reduce water velocity to increase pressure energy. Most pumps are designed such that the impeller and casing remain concentric.
Figure: Vortex casing and casing with guide blades.
Suction pipe with filter and valve
The suction pipe connects the source of water and the pump. The suction valve regulates the amount of water entering the pump. The strainer filters solid particles contained in the water.
Discharge pipe and valve
The discharge pipe has one end connected to the pump and the other connected to the pipe network. The discharge pipe conveys water from the pump into the piping system. The discharge valve regulates the water leaving the pump into the pipe network.
Figure: Components of a centrifugal Monoblock water pump.
How does a centrifugal Monoblock water pump work?
Before start of pumping process, the pump is filled with water to remove air inside so that atmospheric pressure can force the water to flow. Centrifugal Monoblock water pump operates by rotating the impeller at a very high speed. The rotation of the impeller creates a vacuum in the pump. A vacuum is a state of low pressure relative to atmospheric pressure. Due to the vacuum inside the pump, atmospheric pressure on the water’s surface forces it into the pump via the suction line. The water enters the pump into the center of the impeller. Due to the impeller rotating at a very high speed, the water gains high kinetic energy, which increases flow velocity. As the water moves around the impeller towards the discharge port, its speed reduces while pressure increases. High pressure is used to move the water to the desired destination.
Figure: Working of a centrifugal Monoblock water pump
Types of centrifugal Monoblock water pump
Self-priming centrifugal Monoblock water pump
A self-priming centrifugal Monoblock water pump is a type of pump that is capable of priming itself. This pump is very advantageous in that it relieves the pump operator of filling the pump with water to remove air in the water. When the impeller rotates, it creates a vacuum in the pump. This vacuum draws air into the pump from the suction line. At the same time, the pump creates a ring of water on the pump casing. As such, an effective gas-tight seal is formed that stops air from returning from the discharge port into the suction pipe.
Bubbles of air are trapped in the water on the impeller vanes and then transferred to the discharge port. At the discharge end, the air leaves, and the water returns to the pump reservoir via gravitational force. The water rises the suction pipe slowly as any air is expelled. The process keeps going on until all the air in the pump is replaced by water. Once all the air is removed, the actual pumping process starts, and water is discharged into the piping system. Centrifugal Monoblock water pump manufacturers design the pump such that when it is shut off, a priming chamber retains water for the pump to prime when it is started again.
Figure: Self-priming centrifugal Monoblock water pump.
Submersible centrifugal Monoblock water pump
Submersible centrifugal Monoblock water pump operates while submerged in water. The pump is designed so that the motor and casing are enclosed in an air-tight enclosure that prevents water entrance into the motor. This design helps prevent water from getting into the motor’s electrical components and causing damage. The pump is suitable for use in deep wells that would not be possible with standard centrifugal Monoblock water pumps. The pump has a long power cable allowing the operator to turn it on and off without getting into the deep well. Centrifugal Monoblock water pump manufacturers design the pump with sensors that notify the operator in case of any technical problem.
Figure: Submersible centrifugal Monoblock water pump.
Applications of centrifugal Monoblock water pump
- These pumps are used to move water from deep wells.
- They are used in construction applications to supply water.
- Centrifugal Monoblock water pumps are used in agriculture to provide irrigation water.
- They are used to provide water in firefighting applications.
- They are used to transport sewage.
- Centrifugal Monoblock water pumps are used to provide municipal and domestic water supply.
Advantages of centrifugal Monoblock water pumps
- These pumps are of simple and compact design.
- They are easy to clean and repair.
- Centrifugal Monoblock water pumps are cheap relative to reciprocating pumps.
- They are free of pulsation flow, unlike positive displacement pumps.
- Centrifugal Monoblock water pumps are suitable for fresh and salty water use.
- They are more energy efficient relative to other centrifugal pumps.
- They do not need shaft coupling.
- They are versatile in size to suit various fluid flow rates.
- They are easy to install.
- They have low noise and vibration.
Disadvantages of centrifugal Monoblock water pumps
- These pumps are prone to cavitation.
- The impellers are prone to wear and need to be replaced.
- The pump needs to be primed unless it is self-priming.
Troubleshooting a centrifugal Monoblock water pump
Zero water flow rate at startup
- Air in the suction line or in the pump. Ensure the pump is filled with water since the pump cannot operate if there is air inside.
- The suction lift is too high. Reduce the suction lift or lower the pump.
- The motor direction of rotation is reversed. Ensure the direction of motor rotation is as indicated by an arrow on the pump casing.
- Low motor speed. Check the motor frequency and voltage are as recommended by the centrifugal Monoblock water pump manufacturer. If not, contact an electrician or power company to correct it.
- Clogged strainer, suction valve, or impeller. Check the filter, impeller, or suction valve for blockage and clean off blocking materials.
Water flow reduces
- Leakage through the suction line. Repair the suction line.
- Leakage through shaft seal. Replace the seals.
- Clogged impeller or strainer. Check the impeller and filter and remove any material causing blockage.
Overheating bearings
- Too tight bearing cover. Loosen bearing cover.
- Insufficient lubrication. Lubricate the bearings adequately.
High vibration and noise
- Loose connection between the pump and foundation. Tighten the pump firmly to the foundation.
- Bearings not lubricated. Lubricate bearings adequately.
- Clogged impeller. Disassemble the pump as instructed by the centrifugal Monoblock water pump manufacturer and remove any material blocking on the impeller.
- Bearings are worn out. Replace bearings.
The pump starts but stops pumping water
- The pump is not properly primed. Prime the pump adequately.
- Air pockets in the suction line. Arrange the suction line properly.
- Leakage through the suction line. Repair the suction line.
Summary
A centrifugal Monoblock water pump is designed without a coupling common in other centrifugal pumps. The shaft on the motor connects the pump. This pump design helps reduce power loss and thus makes the pump more economical relative to pumps using shaft coupling. The pump operates by rotating impeller at high speed to create a vacuum inside. Due to this vacuum, water is drawn into the pump from the water tank. The high-speed impellers impart kinetic energy onto the water, increasing its flow velocity. As the fluid proceeds between the impeller and casing towards the discharge, the speed reduces while pressure energy rises. The pressure energy moves the water to the required destination.
Centrifugal Monoblock water pump manufacturers produce various types of pumps, including self-priming and submersible pumps. This pump is used in construction, agriculture, firefighting, and domestic and commercial water supply. The advantages of centrifugal Monoblock water pumps are that they are easy to install, clean, and repair, versatile in size and applications, are cheaper than other pumps, have a simple and compact design, and have low noise and vibration. However, this pump needs to be primed unless it is a self-priming pump.