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Understanding the Causes of Pump Shaft Breakage

By NTS.

Pump shafts are essential in many industrial and commercial applications, providing the necessary mechanical force to move fluids through pipelines and process systems. However, when a pump shaft breaks, it can cause significant downtime, production losses, and safety risks. In this article, we will explore the common causes of pump shaft breakage and how to prevent it from occurring.

1. Excessive Load 

The most common cause of pump shaft breakage is excessive load. When a pump is overloaded, it places a significant amount of stress on the shaft, causing it to bend, warp, or break. Overloading can be caused by a variety of factors such as a clogged discharge line, worn impeller, or damaged bearings. Proper maintenance, regular inspections, and monitoring of the pump's performance can help prevent overloading.

2. Misalignment 

If the pump and motor are not properly aligned, it can cause stress on the pump shaft and lead to breakage. Misalignment can occur due to improper installation, wear and tear over time, or environmental factors such as temperature fluctuations. Proper alignment should be checked during installation and regularly during maintenance checks.

3. Excessive Vibration

High vibration in a pump can cause repeated cycles of stress and strain on the pump shaft, leading to microscopic cracks that can eventually cause the shaft to fail. Improper alignment or balance of the pump can increase vibrations and stress on the shaft. Other pump components, such as bearings and seals, can also be damaged by high vibration, increasing stress on the pump shaft. To prevent pump shaft breakage due to high vibration, it is important to properly balance and align the pump during installation, perform regular maintenance and inspections, and use vibration monitoring equipment to detect changes in vibration levels.

4. Fatigue 

Over time, a pump shaft may develop microscopic cracks due to repeated stress and vibration. These cracks can eventually lead to a complete break if not addressed. To prevent fatigue failure, it is important to regularly inspect the pump shaft for signs of wear and to replace it if necessary.

5. Corrosion 

If the pump is used to handle corrosive fluids, the shaft may become weakened and more susceptible to breakage over time. The selection of materials for the pump shaft should be based on the type of fluids that it will handle, and should be resistant to corrosion.

6. Material Defects 

In rare cases, the pump shaft may have a manufacturing defect that causes it to break prematurely. Proper inspection and testing of the pump components before and after installation can help to identify and address any manufacturing defects.

 

7. Wrong design or Selection

 

A wrong design can also be a cause of pump shaft breakage. If the pump shaft is not designed or specified to handle the load or conditions of the specific application, it can result in premature failure. This can occur if the pump is incorrectly sized, or if the pump shaft material or design is not appropriate for the fluid being pumped or the operating conditions of the pump.

 

For example, if a pump shaft is designed with insufficient strength or stiffness, it may deform or break under heavy loads or high vibration. Similarly, if a pump shaft is not resistant to corrosion, it may wear down more quickly and become more susceptible to breakage. In these cases, a redesign of the pump or the selection of a more suitable pump shaft material or design may be necessary.

 

To avoid this problem, it is important to consider the specific application requirements when selecting a pump and pump shaft. This includes factors such as the fluid being pumped, the operating conditions, and the required flow rate and pressure. It is also important to work with a qualified engineer or pump specialist to ensure that the pump and pump shaft are designed and specified correctly for the application. Proper testing and inspection of the pump and pump shaft during installation and regular maintenance checks can also help to identify and address any design issues that may contribute to pump shaft breakage.

 

8. Lack of vortex breaker in pump suction

 

The lack of a vortex breaker can also lead to pump shaft breakage. A vortex breaker is a device that is installed in the suction line of a pump to prevent the formation of a vortex or whirlpool at the inlet. Without a vortex breaker, the fluid entering the pump may spin in a circular motion, creating a low-pressure area at the center of the impeller. This low-pressure area can cause the impeller to become unbalanced, leading to excessive vibration and stress on the pump shaft.

Over time, this vibration and stress can cause the pump shaft to fatigue and eventually break. This is especially true if the pump is handling abrasive or corrosive fluids, which can further wear down the pump components and increase the risk of shaft breakage.

To prevent this problem, it is important to install a vortex breaker in the suction line of the pump, especially if the pump is handling abrasive or corrosive fluids. The vortex breaker should be designed and sized appropriately for the specific application, taking into account factors such as the flow rate and pressure of the fluid being pumped, as well as the size and type of the pump.

a condensate pump shaft breakage due to lack of vortex breaker in the suction line
Without a vortex breaker, the condensate water entering the pump suction line was creating vortices, causing the impeller to become unbalanced and leading to excessive vibration and stress on the pump shaft. Over time, the pump shaft fatigued and eventually broke. To prevent future pump shaft breakage, a vortex breaker was installed in the suction line of the condensate pump.
Regular inspection and maintenance of the pump and its components, including the vortex breaker, can also help to identify and address any issues before they lead to pump shaft breakage. If pump shaft breakage still occurs despite the installation of a vortex breaker and regular maintenance, it may be necessary to consult with a qualified engineer or pump specialist to diagnose and resolve the problem.

9. Lacking oil lubrication

The lack of oil lubrication and bearing sticking can lead to pump shaft overload and ultimately breakage. Pump bearings require a continuous supply of oil to lubricate the surfaces and reduce friction and wear. If the oil supply is interrupted or insufficient, the bearings can overheat and seize, causing the pump shaft to become stuck or overloaded.
Over time, this can cause the pump shaft to deform or break due to excessive stress and heat. In addition, the lack of lubrication can also cause the pump shaft to wear down more quickly, reducing its strength and durability.
To prevent this problem, it is important to ensure that the pump bearings are properly lubricated and that the oil supply is adequate for the specific application. This includes regular oil level checks and oil changes as recommended by the pump manufacturer. In addition, it is important to monitor the pump's operating conditions, such as temperature and vibration, to detect any issues with the bearing lubrication and performance.
If a bearing or pump shaft failure does occur due to a lack of lubrication, it may be necessary to replace the damaged components and improve the lubrication system to prevent future failures. This may involve installing a better lubrication system, increasing the oil flow rate, or using higher-quality oil with better lubricating properties.

Regular maintenance and inspection of the pump and its components can also help to detect and address any issues with bearing lubrication and performance before they lead to pump shaft breakage. This can help to prevent costly downtime and repairs, as well as ensure the safe and reliable operation of the pump.

In conclusion, preventing pump shaft breakage requires proper maintenance, regular inspections, and monitoring of the pump's performance. By understanding the common causes of pump shaft breakage and taking steps to prevent it, companies can ensure that their pump systems operate safely and efficiently. Consulting with a qualified engineer or pump specialist may be necessary to diagnose and resolve the problem if pump shaft breakage persists despite maintenance efforts.

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