Centrifugal Pump Casing

When selecting a centrifugal pump, it’s important to consider the types of casing available. From volute, double volute and multi-stage styles, this guide will help you understand the advantages and differences of each style so you can make an informed decision.

Volute Casing

Volute casing is widely used for low flow and pressure applications. One noticeable feature of this type of casing is the curved outlet or volute, to improve the efficiency of the pump. It also comes with a variety of impeller designs, making it simple and convenient to customize according to your needs. The volute discharge increases gradually to help make smoother flow around the impeller which reduces wear on the pump. This makes it ideal for many applications including cooling water pumps, hot oil re circulation pumps and de watering tasks.

A volute casing is a type of casing used in centrifugal pumps to convert the kinetic energy of a fluid into potential energy. It is shaped like a spiral or snail shell and is designed to improve the efficiency of the pump. Here are the design, specification, advantages, and capacity range of volute casing:

Design:

The design of the volute casing is critical to the performance of a centrifugal pump. It is designed to create a spiral flow path for the fluid to flow from the impeller to the discharge port. The spiral shape of the casing converts the kinetic energy of the fluid into pressure energy, which is then used to move the fluid through the pump.

Specification:

The specification of the volute casing depends on the specific requirements of the application. It is usually made of cast iron, stainless steel, or other materials that are resistant to corrosion and erosion. The diameter of the casing is designed to match the diameter of the impeller, and the length of the casing is designed to provide the necessary pressure increase.

Advantages:

There are several advantages of using a volute casing in centrifugal pumps, including:

1. Improved efficiency: The spiral shape of the casing helps to convert more of the kinetic energy of the fluid into pressure energy, which improves the overall efficiency of the pump.
2. Reduced turbulence: The spiral flow path created by the casing helps to reduce turbulence in the fluid, which can improve the performance and longevity of the pump.
3. Lower noise levels: The volute casing can help to reduce the noise levels produced by the pump, which is especially important in applications where noise is a concern.
4. Easy to manufacture: The volute casing is relatively simple to manufacture and can be made from a variety of materials, which makes it a cost-effective solution for many applications.

Capacity range:

The capacity range of a volute casing depends on the size and design of the pump. They are commonly used in pumps with capacities ranging from a few liters per minute to several thousand liters per minute. The maximum capacity of a volute casing pump depends on the specific design of the pump and the operating conditions.

Double Volute Casing

Another type of centrifugal pump casing is the double volute casing which features two volutes on the outside of the case. This helps to reduce pressure in the pump, allowing for higher flow rates and increased efficiency. It also reduces radial loads on bearings and seals as there are more volutes distributing these loads evenly throughout the case. Double volute pumps have a wide range of applications in industrial processes and can be used in any situation where very high pressures are required.

A double volute casing is a type of casing used in centrifugal pumps that has two spiral volutes instead of one. It is designed to reduce radial loads on the impeller and improve overall pump efficiency. Here are the design, specification, advantages, capacity range, and calculation formula for double volute casing:

Design:

A double volute casing is designed to reduce the radial loads on the impeller by balancing the hydraulic forces acting on the impeller. The two volutes in the casing are arranged in a symmetrical pattern to reduce the turbulence in the fluid flow. The design also helps to reduce the noise level and vibration of the pump.

Specification:

The specification of the double volute casing depends on the specific requirements of the application. It is typically made of cast iron, stainless steel, or other materials that are resistant to corrosion and erosion. The diameter of the casing is designed to match the diameter of the impeller, and the length of the casing is designed to provide the necessary pressure increase.

Advantages:

There are several advantages of using a double volute casing in centrifugal pumps, including:

1. Improved efficiency: The double volute casing helps to reduce radial loads on the impeller, which improves the overall efficiency of the pump.
2. Reduced turbulence: The symmetrical arrangement of the two volutes helps to reduce turbulence in the fluid, which can improve the performance and longevity of the pump.
3. Lower noise levels: The double volute casing can help to reduce the noise levels produced by the pump, which is especially important in applications where noise is a concern.
4. Increased durability: The reduced radial loads on the impeller can help to increase the durability of the pump, reducing the need for maintenance and repair.

Capacity range:

The capacity range of a double volute casing depends on the size and design of the pump. They are commonly used in pumps with capacities ranging from a few liters per minute to several thousand liters per minute. The maximum capacity of a double volute casing pump depends on the specific design of the pump and the operating conditions.

Calculation formula:

The calculation formula for the double volute casing is similar to that of a single volute casing. The head generated by the double volute casing can be calculated using the following formula:

H = (Q^2 / (N^2 x D^4)) x C

Where: H = head generated by the casing (m) Q = flow rate (m^3/s) N = pump speed (rpm) D = impeller diameter (m) C = constant (typically 0.002 to 0.005)

The capacity range and other design specifications can be calculated based on the specific requirements of the application.

Split Case Pump Casing

A split-case centrifugal pump uses a casing that is split longitudinally along a vertical plane running through the center. This allows for quick and easy access for maintenance, operation and inspection of the internal components. The two halves of the case are bolted together to form a single sealed unit. Split-case pumps are usually used in larger applications and can provide optimal performance from the low-to-high capacity range. They also offer higher efficiency compared to other designs due to their larger internal volumes which allow for greater amounts of liquid circulation within the casing.

A split-case pump is a type of centrifugal pump that is designed with a split-casing or double casing, which is separated by a central chamber or suction pipe. The design of the split-case pump casing is intended to make it easier to service and maintain the pump, as well as improve the pump’s efficiency. Here are the design, specification, advantages, capacity flow and head, and calculation formula for split-case pump casing:

Design:

The split-case pump casing is typically made of cast iron or other materials that are resistant to corrosion and erosion. The design of the casing allows it to be split along the vertical plane, making it easier to access the internal parts of the pump for maintenance and repairs. The casing is designed to provide a smooth and stable flow of fluid to the impeller, reducing turbulence and improving the overall efficiency of the pump.

Specification:

The specification of the split-case pump casing depends on the specific requirements of the application. The casing is typically designed to match the diameter of the impeller and provide the necessary pressure increase. The materials used for the casing should be resistant to the fluids being pumped and should be durable enough to withstand the operating conditions.

Advantages:

There are several advantages of using a split-case pump casing, including:

1. Easy maintenance: The split-case design of the casing makes it easy to access the internal parts of the pump for maintenance and repairs.
2. High efficiency: The smooth and stable flow of fluid through the casing reduces turbulence and improves the overall efficiency of the pump.
3. Reduced noise: The design of the casing can help to reduce the noise level produced by the pump.
4. Increased durability: The materials used for the casing are typically resistant to corrosion and erosion, increasing the durability of the pump and reducing the need for maintenance and repair.

Capacity and Head:

The capacity and head of a split-case pump depend on the size and design of the pump. They are commonly used in pumps with capacities ranging from several hundred liters per minute to several thousand liters per minute. The maximum head of a split-case pump depends on the specific design of the pump and the operating conditions.

Calculation Formula:

The head and flow rate generated by the split-case pump casing can be calculated using the following formula:

H = (Q x Hf) / (K x D^2)

Where: H = head generated by the pump (m) Q = flow rate (m^3/s) Hf = head loss due to friction in the pump (m) K = constant related to the specific design of the pump (typically 1.2 to 2.0) D = impeller diameter (m)

The capacity and head of the pump can be calculated based on the specific requirements of the application. The split-case design of the casing can help to improve the efficiency and durability of the pump, making it a popular choice in many applications.

Multi-Stage Pump Casing

Multi-stage centrifugal pump casing is used when higher pressures and flows are required. It consists of two or more impellers which are housed in the same casing but connected by an intermediate chamber known as a diffuser. The diffuser increases the efficiency of the pump by allowing each stage to be working under optimal conditions; this means that pressure can be developed by allowing greater amounts of water to flow from one stage to the next. Multi-stage pumps may also have double volute or split-case designs for added durability and accuracy when pumping highly viscous fluids.

A multi-stage pump is a type of centrifugal pump that consists of two or more impellers mounted on a common shaft within the same pump casing. The pump casing for a multi-stage pump is designed to handle high pressures and deliver high flow rates efficiently. Here are the design, specification, advantages, capacity flow and head, and calculation formula for a multi-stage pump casing:

Design:

The multi-stage pump casing is typically designed to handle high pressures and deliver high flow rates efficiently. The casing is usually made of cast iron, stainless steel, or other materials that are resistant to corrosion and erosion. The casing contains multiple impellers, each of which is designed to increase the pressure of the fluid passing through the pump.

Specification:

The specification of the multi-stage pump casing depends on the specific requirements of the application. The casing is designed to match the diameter of the impellers and provide the necessary pressure increase. The materials used for the casing should be resistant to the fluids being pumped and should be durable enough to withstand the operating conditions.

Advantages:

There are several advantages of using a multi-stage pump casing, including:

1. High efficiency: The multi-stage design of the pump casing allows for a higher efficiency compared to single-stage pumps.
2. High pressure capability: The design of the casing allows it to handle high pressures, making it suitable for applications where high pressure is required.
3. Reduced noise: The design of the casing can help to reduce the noise level produced by the pump.
4. Increased durability: The materials used for the casing are typically resistant to corrosion and erosion, increasing the durability of the pump and reducing the need for maintenance and repair.

Capacity and Head:

The capacity and head of a multi-stage pump depend on the size and design of the pump. They are commonly used in pumps with capacities ranging from several hundred liters per minute to several thousand liters per minute. The maximum head of a multi-stage pump depends on the specific design of the pump and the operating conditions.

Calculation Formula:

The head and flow rate generated by the multi-stage pump casing can be calculated using the following formula:

H = (Q x Hf) / (K x D^2)

Where: H = head generated by the pump (m) Q = flow rate (m^3/s) Hf = head loss due to friction in the pump (m) K = constant related to the specific design of the pump (typically 1.2 to 2.0) D = impeller diameter (m)

The capacity and head of the pump can be calculated based on the specific requirements of the application. The multi-stage design of the casing can help to improve the efficiency and durability of the pump, making it a popular choice in many applications.

Thumb rule for centrifugal pump casing selection

There are several thumb rules for selecting a centrifugal pump casing based on the application and operating conditions. Here are some general guidelines:

1. Material selection: The material of the pump casing should be selected based on the type of fluid being pumped and its temperature. For example, if the fluid is corrosive, the casing should be made of a material that is resistant to corrosion. Similarly, if the fluid is hot, the casing material should be able to withstand high temperatures.
2. Impeller size: The diameter of the impeller is an important consideration when selecting a pump casing. The casing should be designed to accommodate the impeller size and provide sufficient clearance for the fluid to pass through.
3. Operating conditions: The operating conditions of the pump, such as flow rate and pressure, should be considered when selecting a pump casing. The casing should be able to handle the pressure and flow rate requirements of the application.
4. Pump type: Different types of pumps have different casing designs. The type of pump being used should be considered when selecting a pump casing.
5. Efficiency: The design of the casing can impact the efficiency of the pump. A well-designed casing can help to improve the efficiency of the pump and reduce energy consumption.
6. Manufacturer recommendations: It is always advisable to refer to the manufacturer’s recommendations when selecting a pump casing. The manufacturer will be able to provide guidance on the appropriate casing for the specific pump model and application.

These thumb rules can provide a starting point for selecting a centrifugal pump casing, but it is important to consider the specific requirements of the application and consult with a pump expert for optimal pump selection.

Thumb rule for centrifugal pump suction discharge nozzle

Here are some general thumb rules for selecting the suction and discharge nozzle sizes, impeller bearing seals for centrifugal pumps:

1. Suction and discharge nozzle sizes: The suction and discharge nozzle sizes of a centrifugal pump should be selected based on the flow rate and the velocity of the fluid. A good rule of thumb is to keep the velocity of the fluid within the suction nozzle below 3 m/s and below 5 m/s within the discharge nozzle. The diameter of the nozzle can then be calculated using the formula D = Q/V, where D is the diameter of the nozzle, Q is the flow rate, and V is the velocity of the fluid.

It is important to consult with the manufacturer’s recommendations and guidelines when selecting the suction and discharge nozzle sizes and impeller bearing seals for a centrifugal pump. These guidelines can provide a starting point, but the specific requirements of the application should always be considered for optimal pump performance and reliability.