Why Pump Shafts Often Break at the Keyway Area

By NTS

Pump shaft failure can lead to significant downtime and repair costs in industrial plants. One of the most common locations for pump shaft failure is at the keyway area. In this article, we will explore the reasons why pump shafts often break at the keyway and what can be done to prevent such failures.

The keyway is a high-stress point (weakest point) on the shaft, where a key is inserted to transmit torque between the shaft and the pump impeller or coupling. During operation, the keyway experiences cyclic loading that creates a bending moment in the shaft, which is concentrated in the keyway area. Over time, this cyclic loading can cause fatigue failure in the shaft material, leading to a fracture at the keyway.

In addition to cyclic loading, other factors can contribute to shaft failure at the keyway. Improper keyway design or installation can lead to stress concentrations or inadequate clearance between the key and keyway. Misalignment or overloading can also cause excessive stress on the shaft, leading to failure.

To prevent pump shaft failure at the keyway, it is important to properly design and install the keyway. The keyway should be wide enough to provide adequate clearance between the key and keyway, and the corners should be chamfered to reduce stress concentrations. The key should also be properly fitted to ensure even load distribution.

Regular inspections and maintenance can help detect any issues before they lead to catastrophic failure. This can include checking for misalignment, wear, or damage to the key or keyway, and ensuring proper lubrication and cooling of the shaft. If any issues are detected, corrective action should be taken promptly to prevent further damage or failure.

In conclusion, pump shaft failure at the keyway area can be a significant issue for industrial plants. Understanding the root causes of such failures and implementing preventive measures can help ensure safe and reliable pump operation. Regular inspections and maintenance are also critical to detecting and addressing any issues before they lead to costly downtime and repairs.