Using Torque Vibration to Detect Cracks in Rotating Machinery Shafts

Using Torque Vibration to Detect Cracks in Rotating Machinery Shafts

Detection of cracks in blades and shafts using torque vibration detection and characterization techniques. Although the initial focus of research was on blade crack detection, it has recently been discovered that the same technology can be applied to shaft crack detection. The basis for this technology is that cracks in either blades or shafts change the characteristics of torque vibration during measurement, thus providing early warnings and tracking the development of defects. Understanding the impact of past accidents in nuclear power plants shows the importance of shaft crack detection.

For example, primary cooling pumps (PCPs) have experienced shaft cracks and subsequent failures, which are often very small or have no warning with current detection technology. Unexpected disconnection of steam generators (SGFPs) in pressurized water reactors or reactor feed pumps (RFPs) in boiling water reactors can cause unit trips and subsequent load reduction. Other pumps have also experienced shaft cracks, such as condensate pumps and centrifugal pumps.

This research project has two main objectives: (1) Demonstrate the feasibility of using torque vibration as a diagnostic method for shaft crack detection and monitoring of rotating machinery in nuclear power plants; (2) Develop a prototype shaft crack detection system for reactor cooling pumps (RCPs). The proposed torque vibration system will be able to discern characteristic changes in torque vibrations that are associated with crack growth. This method is less sensitive than existing crack detection systems to changes in pump rotating components such as seals, oil films, and brackets. Based on laboratory and field applications, this method can automatically measure the integrity of the shaft structure.

Applications of this method include any system with a rotating shaft, such as: reactor coolant pumps, centrifugal charge pumps, condensate and feed water pumps.