Centrifugal pumps are some of the most common types of pumps used in industrial applications all over South Africa because they are designed to be low-maintenance, highly efficient, and simple to operate.

The fact that centrifugal pumps are widely used and trusted by al types of industrial plants doesn’t mean that you will never experience any issues with them. Here is what you need to know about centrifugal pumps, and where they are used. In this blog post by Piper Pumps, we will also explain the most common problems experienced with centrifugal pumps and the solutions to these problems.

What Is A Centrifugal Pump?

A typical centrifugal pump is constructed of a rotary pump shaft with one or more impellers attached to it. A centrifugal pump moves a fluid by means of the transfer of rotational energy from one or more driven rotors that are called impellers.

Fluid enters the rapidly rotating impeller along its axis and is cast out by centrifugal force along its circumference through the impeller's vane tips. As the impellers rotate in sync, the pump converts enough energy to move fluids in the desired direction. There are two different types of centrifugal pumps, namely radial centrifugal pumps and axial centrifugal pumps.

The main difference between radial centrifugal pumps and axial centrifugal pumps is the direction of the fluid flow through the pump. In a radial centrifugal pump, the fluid enters the pump axially and is then directed radially outward by the impeller blades, perpendicular to the shaft.

The flow direction changes from axial to radial as the fluid passes through the impeller, and then exits the pump at a right angle to the shaft. Radial centrifugal pumps are well suited for applications requiring high-pressure or high-head applications, such as in chemical processing, water treatment, or power generation.

In contrast, axial centrifugal pumps direct the fluid flow parallel to the pump shaft axis. The fluid enters and exits the pump in the same direction, with the impeller blades rotating around the shaft to push the fluid through the pump. Axial centrifugal pumps are typically used in applications requiring high flow rates at low to medium pressure, such as in irrigation or cooling water systems.

Overall, the choice between a radial or axial centrifugal pump depends on the specific application requirements, including flow rate, pressure, and fluid properties.

Common Uses For Centrifugal Pumps

Centrifugal pumps are commonly used in various industrial, commercial, and even domestic markets.

Some of these centrifugal pump applications include:

• Food and beverage manufacturing/processing

• Fire protection systems

• Municipal water supply for residential areas

• Sewage and slurry disposal

• Oil and gas industrial operations

• Chemical manufacturing

Common Centrifugal Pump Problems and Solutions

Here are some of the most common centrifugal pump problems and solutions. If your centrifugal pump stops working as it should, we recommend calling a professional from Piper Pumps.

1. Cavitation:

This occurs when the pressure inside the pump drops below the vapour pressure of the liquid, causing bubbles to form. These bubbles then collapse, causing damage to the impeller and reducing the pump's efficiency. The solution to this problem is to increase the pressure in the suction line or to reduce the speed of the pump.

2. Pump Running Dry

Running a centrifugal pump dry, or without sufficient fluid, is a significant problem because it can cause the pump to overheat, damage the impeller, and reduce the pump's efficiency. Centrifugal pumps rely on the fluid being pumped for cooling and lubrication of the impeller and other moving parts.

When there is insufficient fluid, the impeller and other components generate heat due to friction, leading to overheating and potential damage. Additionally, the lack of fluid can cause the impeller to spin faster than its intended speed, leading to premature wear and damage. In extreme cases, running a centrifugal pump dry can cause the impeller to seize or break, leading to costly repairs or replacement.

Therefore, it is crucial to ensure that a centrifugal pump is always operated with sufficient fluid to prevent damage and ensure optimal performance.

• Air in the pump: Make sure that all pipework and the pump are completely filled with liquid.

• Suction lift is too high: Check for any obstructions in the inlet and verify that the static lift is correct.

• Operation reversed: Check the direction of the impeller rotation to ensure it isn’t reversed.

• Incorrect speed: Check the power supply voltage and frequency and confirm that the motor doesn’t have an open phase.

• Clogged parts: Check and clean the valve, impeller, and strainer.

3. Reversed Impeller Rotation

Reversed impeller rotation in a centrifugal pump is a significant problem because it can cause the pump to perform poorly, generate low flow rates, and potentially damage the impeller and other pump components.

Centrifugal pumps are designed to operate with a specific impeller rotation direction that is typically indicated by an arrow on the pump casing. Reversing the impeller rotation can cause the fluid to move in the opposite direction, leading to reduced efficiency and performance. This can also cause the fluid to swirl or vortex, which can lead to cavitation, erosion, and damage to the impeller and other pump components. Additionally, reversed impeller rotation can lead to excessive noise, vibrations, and increased wear on the bearings, potentially causing premature failure.

Therefore, it is essential to ensure that a centrifugal pump's impeller rotation direction is correct before the operation to prevent poor performance and potential damage to the pump.

4. Pump Leakage

Pump leakage in a centrifugal pump is a significant problem because it can lead to reduced efficiency, increased operating costs, and potential safety hazards. Centrifugal pumps rely on seals and gaskets to prevent fluid from leaking out of the pump casing or from the suction and discharge lines. When these seals and gaskets fail or wear out, it can cause fluid to leak out of the pump, leading to reduced flow rates and efficiency.

Additionally, pump leakage can result in increased operating costs due to the loss of product and the need for more frequent maintenance and repair. In some cases, pump leakage can lead to safety hazards, such as slips and falls, fire, or environmental contamination, resulting in potential fines or legal action. Therefore, it is essential to ensure that a centrifugal pump's seals and gaskets are regularly inspected and maintained to prevent pump leakage and ensure optimal performance. If pump leakage is detected, prompt repair or replacement of the faulty components is necessary to prevent further damage and ensure safe and efficient operation.

5. Slow Pump Re-Priming

Slow pump re-priming in a centrifugal pump is a significant problem because it can cause downtime, reduced productivity, and potential damage to the pump and other system components.

Centrifugal pumps rely on a continuous supply of fluid to maintain their prime and operate efficiently. However, if the pump loses its prime due to air entering the suction line or other causes, it can take time to re-prime the pump and restart operation. Slow pump re-priming can cause significant downtime and reduce productivity, leading to lost production and revenue.

Additionally, during the re-priming process, the pump may operate in a low-flow or no-flow condition, which can cause cavitation and potential damage to the impeller and other pump components.

Therefore, it is essential to identify the root cause of slow pump re-priming and take corrective action, such as eliminating air leaks in the suction line, ensuring the pump is properly sized and installed, and using automatic priming systems to minimize downtime and reducing the risk of pump damage. Regular maintenance and inspection can also help to identify and address potential re-priming issues before they become significant problems.

6. Debris In The Centrifugal Pump

Debris in a centrifugal pump is a significant problem because it can cause blockages, reduce the pump's efficiency, and potentially damage the impeller and other pump components. Centrifugal pumps are designed to handle fluids containing a certain amount of suspended solids and debris. However, when the debris concentration is too high, it can cause blockages in the pump's suction and discharge lines, reducing the pump's flow rate and efficiency.

Additionally, debris can cause abrasion and erosion of the impeller and other pump components, leading to premature wear and failure. This can cause the pump to generate excessive noise and vibrations, and potentially damage other system components, such as valves and piping. In some cases, the debris can cause the pump to seize or become inoperable, resulting in downtime and costly repairs or replacement.

Therefore, it is essential to ensure that the fluid being pumped is free from excessive debris and that the pump is regularly inspected and maintained to prevent blockages and potential damage.

7. Pump Vibration

Pump vibration in a centrifugal pump can cause significant problems because it can lead to damage, reduced efficiency, and increased operating costs. Vibrations in a pump can be caused by various factors, such as misalignment, worn bearings, unbalanced impellers, or cavitation.

The constant vibration can lead to wear and tear on the pump's components, leading to reduced efficiency and potential failure. Additionally, pump vibration can cause increased wear on the shaft and bearings, leading to increased maintenance and operating costs.

In some cases, excessive vibration can cause damage to other system components, such as pipes or valves, resulting in potential leaks and safety hazards.

Therefore, it is essential to identify the root cause of pump vibration and take corrective action, such as realigning the pump, replacing worn bearings or impellers, or adjusting the pump's operating conditions to prevent excessive vibration. Regular inspection and maintenance can also help to identify and address potential vibration issues before they become significant problems.

8. Pump Seizure

A seizure is when the impeller binds to the volute because of an obstruction. If a seizure occurs, the motor overheats and trips the thermal overload protection device (fuse or breaker). Pump seizure can happen for several reasons, including foreign objects entering the pump, low flow operation, and off-design conditions. Inspect the pump for foreign objects and debris first and then check the impellers and power source.

9. Pump Driver Overload

In centrifugal pumps, overloading occurs when the driving motor draws excess current, which results in much greater than normal power consumption. (Check out our blog article on improving the energy efficiency of your pumps.) Pumps should start with a minimum load with discharge valves open. If the power drawn by the pump increases too much, it may ultimately lead to tripping or overloading of the motor. Here are some things to check for...

• Check that the pump is not operating too far out of optimum range.
• Check for worn or damaged bearings.
  
• Check if an oversized impeller was installed.
• Check for misalignment between the driver and pump.
• Make sure that stationary parts are not coming into contact with rotating parts.
• Check for a bent pump shaft.
• Check if the mechanical seal is putting too much pressure on the seat.

10. Chemical Compatability Issues

Chemical compatibility issues in a centrifugal pump are a significant problem because they can cause corrosion, erosion, and damage to the pump's components, reducing its efficiency and potentially causing leaks or failures. Centrifugal pumps are used to handle various fluids, including corrosive and aggressive chemicals.

However, some chemicals can be incompatible with the materials used in the pump's construction, such as the casing, impeller, seals, and gaskets. When incompatible chemicals come into contact with these materials, they can cause chemical reactions that lead to corrosion, erosion, and other forms of damage, reducing the pump's efficiency and lifespan.

Additionally, chemical compatibility issues can cause leaks, leading to safety hazards, environmental contamination, and potential fines or legal action. Therefore, it is essential to ensure that the materials used in the pump's construction are compatible with the fluid being pumped to prevent chemical reactions and potential damage to the pump and other system components. Regular inspection and maintenance can also help to identify and address any compatibility issues before they cause significant damage.

11. Bearing Overheating

This is another common problem with centrifugal pumps and is easy to diagnose.

Centrifugal pumps should not feel hot to the touch. When they do, this is more often than not a sign of impending trouble and it is something that you want to inspect immediately. 

Piper Pumps offers a wide range of centrifugal pumps that will give your plant the fluid-transfer solutions and services it needs. We offer excellent, low-cost solutions for centrifugal pumps and if your centrifugal pumps aren't operating efficiently, Piper Pumps have the Experts, knowledge and experience to help you.