Vertical Split Case Centrifugal Pump
Vertical Split Case Centrifugal Pump
What is a vertical split case centrifugal pump?
A vertical split case centrifugal pump is a type of dynamic rotor pump with either single suction or double suction impeller supported between bearings. It contains a pump casing that is split horizontally or vertically to facilitate easier disassembly and maintenance. The design of the split casing depends on the vertical split case centrifugal pump type. Vertical split case centrifugal pump manufacturers usually design the unit for vertical mounting. Vertical split case centrifugal pump suits applications that require higher fluid flow rates than the convectional end suction pumps can provide. It is mainly used with water and relatively thin pumped media. Vertical split case pump manufacturers create these edge-cutting devices to manage a maximum pressure head of 180 meters at a high flow rate of up to 6000 cubic meters per hour. Vertical split case centrifugal pumps are available in various materials such as bronze, cast Iron, cast steel, ductile Iron, and duplex to fit different application requirements.
Figure: Vertical split case centrifugal pump
Components of a vertical split case centrifugal pump
The electric motor is the source of power for the pump. The electric motor can be either an alternating current (AC) or a direct current (DC) motor. The vertical split case centrifugal pump can work using an alternating current motor, either a single-phase or a three-phase induction motor.
The casing is a stationary component housing the rotor assembly and carrying the suction and discharge ports. It contains the liquid and directs the flow into the pump through the suction pipe and out of the pump through the delivery pipe. The pump casing also serves as a pressure containment vessel. The pump casing can be either horizontally split or vertically split casing with double volute to help reduce radial bearing loads.
Figure: Vertically split pump casing.
Vertical split case centrifugal pump manufacturers employ a long coupling for the pump to help with easy pump maintenance. The coupling connects the motor’s driver shaft with the rotating pump shaft to ensure the transfer of mechanical torque to the pump head with minimal losses. The long coupling design allows access to the pump head without removing the motor. It also provides ample space between the pump and motor, which helps to protect the motor from fluid ingress in the case of a seal failure.
The shaft is a rotary mechanical component supported on bearings. Its main functions are to carry the impeller. It is usually coupled with the prime mover. Vertical split case centrifugal pump manufacturers create the shaft from high-grade materials such as stainless steel and alloy steel to withstand corrosion and vibrations during pump operation.
The impeller is the main rotary component in a vertical split case centrifugal pump. It features a series of backward-curved vanes. Its function is to increase the kinetic energy and pressure of the fluid to move through the pump. The vertical split case centrifugal pump uses a closed-type impeller with either a single-suction or double-suction design.
Figure: Showing pump impellers; a) single-suction design and b) double-suction design.
The primary function of the bearings is to support the pump shaft or the rotor assembly and to align them correctly with the fixed ends under the action of radial and axial forces. Additionally, the bearings also help to contain the rotor’s relative motion and minimize the friction between the rotating shaft and the stator.
How does a vertical split case centrifugal pump work?
A vertical split case centrifugal pump works by converting the mechanical energy of an impeller into kinetic and pressure energy of the pumped liquid. When the electric motor starts, the mechanical torque is transferred to the impeller via the pump shaft and the coupling. As the impeller rotates, a vacuum is created inside the pump, allowing the pumped fluid to flow into the pump casing and toward the impeller’s eye due to the external atmospheric pressure. As long as the impeller rotates, more liquid draws into the pump casing, and centrifugal force acting on the impeller blades causes the pumped liquid to move radially outwards, away from the impeller center of rotation, at high tangential velocity. The swirling flow at the exit of the impeller then enters into the diffuser, where the extreme fluid flow speed decreases due to the gradually expanding flow path, and the high-velocity energy converts into a high-pressure head. The pumped liquid then discharges from the vertical split case centrifugal pump at elevated pressure, which allows the fluid to transport to the desired location through the discharge port and delivery pipe connections.
Figure: Working of a vertical split case centrifugal pump.
Types of vertical split case centrifugal pumps
Single-suction vertical split case centrifugal pump
In a single suction vertical split case centrifugal pump, the water flows into the pump inlet, and the whole volume enters the impeller blades only through one side. The centrifugal effect generates fluid pressure as the blades displace the liquid through the pump. It has a robust design and can cost half the price of a comparable double-suction pump.
Figure: Showing the configuration of a single-suction vertical split case centrifugal pump.
Double suction vertical split case centrifugal pump
A double suction vertical split case centrifugal pump has an impeller designed to admit water from both sides of the blades. The double-suction impeller splits the flow inside the pump, sending half of the flow through either eyes or inlets of the impeller. The double suction vertical split case centrifugal pump gives a better Net Positive Suction Head (NPSH) and lower axial thrust. It also lasts longer (30 to 40 years) and allows for higher flows than its single-suction counterpart.
Applications of vertical split case centrifugal pumps
The vertical split case centrifugal pumps are extensively used in various applications in different industries, such as agriculture, mining, municipal wastewater plants, petroleum, chemical, petrochemical, etc. They are used to do the following
- Vertical split case centrifugal pumps are used to pump water at a high flow rate and low to medium pressure in residential and industrial water supply systems.
- They are used as booster pumps in booster stations.
- They are used to pump oil from the oil sump.
- They are used to support fire protection equipment.
- They are used in chemical manufacturing and food processing.
- They are used to handle condensate
Advantages of a vertical split case centrifugal pump
- Vertical split-case centrifugal pumps are space-saving because of their vertical orientation.
- The pump casing is split into two chambers. This helps to increase the suction performance. It also helps balance the hydraulic axial forces, increasing the bearing life and improving reliability.
- They have high reliability and energy efficiency.
- Vertical split case centrifugal pump with double suction impeller can manage extremely high flow rates.
- A vertical split case pump is easy to maintain due to the long coupling between the electric motor and the pump head. The pump head can be accessed without removing the motor.
- The long coupling maintains an adequate space between the motor and the pump head, preventing the pumped fluid from getting into the motor when mechanical seals fail.
- Vertical split-case centrifugal pumps have independent motors and pump shafts, which means that only one of them will need to be replaced if damaged.
- A vertical split case centrifugal pump is more robust and fit for continuous use because the additional bearing assembly in the pump head relieves a significant level of strain from the motor during operation.
- Vertica split case centrifugal pump saves repair/servicing time. The split casing design allows easy dismantling of the rotor assembly without interfering with the pump alignment, saving time during repair or maintenance.
Disadvantages of a vertical split case centrifugal pump
- Vertical split case centrifugal pump cannot pump thicker oils or liquid containing suspended solids.
- They require vertical clearance for installations, which makes them difficult to install and maintain.
- The weight of the pump falls below the volute leading to stress concentration.
- Vertical split-case centrifugal pumps have a limited drive option because they can only be coupled to an electric motor.
Troubleshooting a vertical split case centrifugal pump
The motor doesn’t run
- There is an open circuit in the thermal overload. Allow the vertical split case centrifugal pump to cool, close any open circuit, and restart it.
- The motor is defective. Inspect and replace the motor if it is necessary.
- The motor is poorly installed. Ensure the pump is installed to the vertical split case centrifugal pump manufacturers’ standards
- There is a tripped circuit breaker or a blown-out fuse. Inspect and reset the circuit breaker if necessary. Inspect the pump for a blown-out fuse and replace it.
The pump gives out insufficient discharge
- The impeller or check valve is clogged. Inspect and clear any blockage in the valve or impeller.
- The monomeric head is insufficient due to high friction losses that exceed the pump design. Increase the pump power. Ensure the pipes used in the piping network meet the diameter recommended by the vertical split case centrifugal pump manufacturer.
- The pump is operating in reverse. Ensure that the motor rotates in the direction indicated by the vertical split case centrifugal pump manufacturer using the arrow on the pump casing. Be sure to reverse the motor polarities.
- There is air in the pump or suction pipework. Be sure to fill the pump or piping network with water to drive out the air.
The pump’s driver is overloaded
- The Pump speed is too high. Ensure the pump operates within the speed range specified by the vertical split case centrifugal pump manufacturer.
- Some pump parts are experiencing extreme mechanical friction. Inspect the pump assembly for any deflection or obstruction and correct it.
- Faulty pump motor. Inspect the motor for defects and repair or replace it if necessary.
The pump is experiencing excessive vibration
- The pump impeller is partially clogged. Inspect and clean the impeller.
- The pump shaft is oblique or unbalanced. Inspect the shaft, rebalance it as required, or replace it.
- Some pump components are loosely mounted in the pump body. Tighten any loose parts to the torque level recommended by the vertical split case centrifugal pump manufacturer.
- Some of the vertical split case centrifugal pump’s components are unbalanced. Inspect and rebalance the parts if necessary.
The noise level is too high
- Some foreign materials are present in the vertical split case centrifugal pump. Disassemble the pump and clean it.
- The impeller is damaged or worn out. Inspect and replace the impeller.
- Pump working in cavitation. Check that the suction line valves are fully open.
- The mounting plate and the foundation lack sufficient rigidity. Reinforce the foundation, and mount the vertical split case centrifugal pump tightly.
- The pump is working outside the duty range. Ensure the correct duty range according to the vertical split case centrifugal pump manufacturer’s guide.
A vertical split case centrifugal pump is a dynamic rotor pump consisting of either a single suction or double suction impeller suspending between bearings. Vertical split case centrifugal pump manufacturers usually design the pumps for vertical mounting. The pump casing is split horizontally or vertically to facilitate easier disassembly and maintenance. In addition, the pump uses a long coupling to help with easy pump maintenance. Vertical split case centrifugal pumps are excellent for applications requiring higher fluid flow rates than the convectional end suction pumps can deliver. They are mainly used with water and other low-viscosity liquids. The vertical split case centrifugal pumps are evident in municipal wastewater plants, agricultural farms, and petrochemical, and chemical processing industries. A typical use of the vertical split case centrifugal pump is pumping water at a high flow rate and low to medium pressure in residential and industrial water supply systems. They are easy to maintain, space-saving, highly efficient, and reliable.