Electric Vertical Multistage Pump Manufacturer

Electric Vertical Multistage Pump

What is an electric vertical multistage pump?

An electric vertical multistage pump is a particular category of dynamic rotor pump comprising two or more impellers to pressurize the water in several stages. The impellers can be attached to the same shaft or separate shafts, but for most electric vertical multistage pumps, the impellers are on the same pump shaft. The electric vertical multistage pump manufacturers usually create the devices to be electrically powered using an electric motor and for vertical installations. Electric vertical multistage pumps convert the impeller’s rotational kinetic energy into hydrodynamic energy. They are perfect for water supply at higher pressures, which single pump counterparts of the same size cannot deliver. They are evident in municipal water supply systems, agricultural farmlands, and high-rise buildings. Electric vertical multistage pumps are often preferred because of their excellent performance characteristics, such as high flow rate, abrasive solution compatibility, mixing potential, and relatively simple design. They are also available in different configurations to cater to various applications’ demands.

Figure: Electric vertical multistage pump

Components of electric vertical multistage pump

Electric motor

The electric motor acts as the pump’s prime mover, providing the mechanical power to run the pump. The electric vertical multistage pump uses an AC (alternating current) electric induction motor, usually close-coupled to the pump body.

Pump casing

The primary purpose of the pump casing is to convert the velocity head from the impeller into the static pressure head and guide the flow to the discharge connections. It also houses the pump’s internal components. The electric vertical multistage pump employs a diffusing type of pump casing, which features a series of vanes surrounding the impeller to accept liquid discharge from the impeller. The diffusing pump casing effectively reduces the fluid velocity and converts the kinetic energy into pressure head. The electric vertical multistage manufacturers usually create the pump casing using materials such as cast steel, cast iron, and ductile iron.

Shaft

The shaft is a stainless-steel solid, centrally located within the pump and riding on the bearings. It mainly supports the impeller and connects the rotor assembly to the motor drive shaft.

Coupling

Electric vertical multistage pumps can be either close-coupled or rigidly coupled based on the type of coupling in use. The purpose of the pump coupling is to connect the motor drive shaft to the pump shaft. The coupling can be either a flexible coupling, which allows for minor shaft misalignment or a rigid coupling, which cannot accommodate any shaft misalignment.

Impeller

The function of the impeller is to impart kinetic energy to the pumped liquid and move it through the pump body. The electric vertical multistage pump manufacturers fit the units with closed-type impellers. Such impellers generate high fluid pressure and provide excellent hydrodynamic efficiency. The type of closed impeller can be either a single-suction or double-suction impeller. Generally, an impeller can be made from various materials, including cast steel, ductile cast iron, and alloy steel.

How does an electric vertical multistage pump work?

An electric vertical multistage pump converts the impeller’s rotational kinetic energy into hydrodynamic energy. When the pump starts, the impellers rotate, creating a vacuum inside the casing. The external atmospheric pressure pushes water into the pump casing through the suction port to fill the void. Once the water strikes the first stage impeller, the rotation of the impeller generates a centrifugal force which directs the fluid along the impeller vane and pushes the liquid to the impeller vane’s outer tip, where it enters the diffuser at a very high tangential velocity. The diffuser efficiently reduces the high flow velocity, converts fluid kinetic energy into static pressure head, and guides the liquid to the inlet or eye of the next stage impeller. This process continues until the last stage impeller and diffusing chamber, where the water attains the required pressure and exits the pump through the discharge nozzle.

Types of electric vertical multistage pump

Close-coupled electric vertical multistage pump

A close-coupled electric vertical multistage pump consists of a single shaft connecting the motor to the pump head. The motor bearings support the full rotary load of the shaft during pump operation. This pump mostly suits light duty applications and short operation periods at full motor speed. It is also known as a monobloc electric vertical multistage pump.

Figure: Monoblock electric vertical multistage pump.

Rigidly coupled electric vertical multistage pump

A rigidly coupled electric vertical multistage pump features separate motor and pump shaft, which must be precisely aligned and firmly fixed using a coupling. Each of the shafts has a short sleeve surrounded by a perpendicular flange. A coupling sits on each shaft, so the two flanges line up face to face. A series of screws or bolts then hold the flanges together. This pump is robust and easier to repair.

Figure: Electric vertical multistage pump.

Stainless steel electric vertical multistage pump

The stainless steel electric multistage pump features a fully stainless-steel construction of all the components that come into contact with the pumped liquid. It provides strong resistance against corrosion, making it safe for food industries and handling swimming pool water.

Figure: Stainless steel electric vertical multistage pump.

Applications of electric vertical multistage pumps

Electric vertical multistage pumps cater to industrial, civil, and municipal water supply systems and agricultural and commercial applications. Electric vertical multistage pumps are used for the following:

Electric vertical multistage pumps are used to transport water for different uses in homes and industries.
They are used to supply and circulate water in hot water heating systems.
They are used for firefighting and as boiler feed pumps.
They are used for irrigation in agricultural farms.
They serve as booster pumps in water supply systems.
They also apply to move water in municipal works and water supply systems.
They are used in construction industries to supply water.
They are used in dewatering.

Advantages of electric vertical multistage pump

Electric vertical multistage pumps have high efficiency and can tolerate higher temperatures and pressure.
They have high reliability and are energy efficient.
Electric vertical multistage pumps are easier to install due to their relatively simple engineering and less complex piping network.
They are excellent for high-pressure and temperature applications.
They also deliver a steady and continuous output.
They provide a space-saving design because the motor and service clearance lay above the pump casing; hence less floor space is required for pump installation.
They have low noise and vibration because the vertical shaft is naturally balanced, and the gravitation force does not act against the direction of shaft rotation.
Electric vertical multistage pumps have higher Net Positive Suction Heads (NPSH) than suction pumps.

Disadvantages of electric vertical multistage pump

Electric vertical multistage pumps require vertical clearance for installation and maintenance.
They are vulnerable to corrosion due to seal leakage above the pump casing.
Electric vertical multistage pumps are subject to mechanical seal problems.

The mechanical seals may dry out or fail due to infiltration and accumulation of gases in the seal chamber.

Large pumps (exceeding 25 hp) pose maintenance challenges because one must disconnect the motor and pump head to service the mechanical seals.

Troubleshooting an electric vertical multistage pump

The motor doesn’t run

The pump cables are broken. Inspect and change the wires if necessary.
The circuit breaker is tripping, or the fuse is blown-out. Reset the circuit breaker if necessary. Inspect the pump for a blown fuse and replace it.
There is no power supply to the Control Panel. Ensure the power cables connect per the electric vertical multistage pump manufacturer’s guide.

Zero discharge after startup

The inline pump operation is reversed. Check that the direction of the motor rotation matches the direction of the electric vertical multistage pump manufacturer’s arrow on the pump casing. Reverse the motor polarities.
The pump inlet is blocked. Clear the channel of any obstruction.
The monomeric head is insufficient due to high friction losses exceeding the pump design. Increase pump power to the level recommended by the electric vertical multistage pump manufacturers. Make sure all valves are open, and pipes have the correct diameter.
The impeller or check valves are clogged. Clear any blockage from the impeller and the valves.
There is air in the pump or suction pipework. Electric vertical multistage pumps cannot prime with air on the suction side. Ensure that the pump or pipework is filled with water to drive out the air from the pump system.

The noise level is too high

The pump is working in cavitation. Ensure that the net suction pressure head meets the electric vertical multistage pump manufacturer’s specifications. Be sure to open the suction line valves fully.
Some parts are loosely tightened. Tighten the pump components to the torque level recommended by the electric vertical multistage pump manufacturers.
The pump is working outside the duty range. Ensure the correct duty range according to the electric vertical multistage pump manufacturer’s manual.
Some pump components are excessively worn-out. Inspect the rotor assembly for worn-out bearings or impellers and replace them if necessary.

The noise level is too high

Some pump components are excessively worn-out. Inspect the rotor assembly for worn-out bearings or impellers and replace them if necessary.
The pump is working in cavitation. Ensure that the net suction pressure head meets the electric vertical multistage pump manufacturer’s specifications. Be sure to open the suction line valves fully.
The pump is working outside the duty range. Ensure the correct duty range according to the electric vertical multistage pump manufacturer’s manual.

The pump is vibrating excessively

Some parts are loose. Tighten the pump components to the torque level recommended by the electric vertical multistage pump manufacturers.
There are unbalanced components in the pump. Inspect and rebalance the electric vertical multistage pump components as necessary.
The pump shaft is oblique or unbalanced. Inspect the post, rebalance it as required, or replace it.
The impeller is severely worn out. Inspect and replace the impeller with another one from the electric vertical multistage pump manufacturer if you find it fit.

The pump driver is overloaded

The density and viscosity of the liquid exceed the pump design. Ensure that the electric vertical multistage pump suits the particular application.
Wrong voltage supply. Check that the pump receives the proper voltage following the electric vertical multistage pump manufacturer.
The pump’s speed is too high. Lower the pump speed.
There is mechanical friction within the pump. Inspect the pump assembly for any obstruction or deflection.

Bearing overheating

The coupling alignment is poor. Inspect and align the coupling correctly.
There is excessive grease in the bearing housing. Drain the excess grease. Maintain the oil at the level recommended by the electric vertical multistage pump manufacturers.
The lubricating oil is insufficient or contaminated with dirt. Ensure the oil level matches the electric vertical multistage pump manufacturer’s specifications. Use clean lubricating oil.

Summary

An electric vertical multistage pump is a highly engineered mechanical device consisting of two or more impellers housed in different chambers to pressurize the water in several stages. The impellers can be mounted on the same shaft or separate shafts. However, the impellers ride on the same shaft for most electric vertical multistage pumps. The electric vertical multistage pump manufacturers mainly employ an AC (alternating current) electric induction motor, usually close-coupled to the pump body, to power the pump. Further, they especially design the pump for vertical installations. Electric vertical multistage pumps are perfect for water supply at higher pressures, which single-stage pumps the same size cannot deliver. They cater to various industrial, civil, agricultural, and commercial applications. They are available in stainless steel construction and with a close-coupled or rigidly coupled design. Electric vertical multistage pumps offer many outstanding benefits, including high efficiency, reliability, versatility, excellent Net Positive Suction Head, and relatively simple engineering with direct piping connections.