A vertical pump impeller shaft resonances of severe fatigue fracture failure diagnosis

A vertical pump impeller shaft resonances of severe fatigue fracture failure diagnosis - 2019 12 - 14 a length, fault equipment the pump motor drive for 1879. 6 mm, the diameter of axle for 88. 9 mm, wall thickness of 2. 4 mm shaft. Impeller blade number is 2 piece, its structure and layout of the measuring point as shown in figure 1. The vertical pump pump shaft fracture occurred many times, split close to the impeller gland nut. (the failure phenomenon is: start vibration The biggest 3 v and 4 v) , impeller gland nut is loose. Subsequently pressure by using epoxy paste on the impeller nut, can effectively prevent the nut is loose. However, after many pump impeller shaft fracture catastrophic damage. So, decided to conduct monitoring analysis: 1. The determination of vibration; 2. Evaluation of vibration severity; 3. Diagnosis of potential faults; 4. Effective troubleshooting measures are put forward. Second, the vibration measured data and fault analysis of the measured show that the 3 v and 4 v measuring point vibration is the largest. 3 v of the spectrum of measuring point, 2 * 3570 RPM RPM frequency component amplitude for 16. 51 mm/s peak, and 1 * RPM frequency component amplitude just 4. 60 mm/s peak. Note: the number of impeller blade is 2 slices, leaf through frequency BPF = 2 * RPM. By hammering method testing the motor shaft and the natural frequency of vibration of the pump. 4 v to the natural frequency of vibration test spectrum showed that the dominant natural frequency of vibration of 3780 RPM, it and run to the biggest vibration frequency spectrum component of the RPM = 3570 RPM = 2 * blade passing frequency (BPF pump impeller BPF) Only poor 210 RPM or 5. 9%. In addition, there are 2009 RPM shaft cover natural frequency of vibration. Due to the natural frequency of vibration of 3780 RPM is too close to the pump impeller blade by frequency or double frequency 3570 RPM, the rotational speed of pump pump system is easy to arouse resonance. Bearing stiffness test, therefore, reinforcing the pump system, changing the system natural frequency of vibration, 'FM) In order to avoid resonance. Three, fault disposal, the effect of 1 # pump auxiliary support, change its natural frequency of vibration. Reinforcement scheme is shown in figure: the pump system and the vibration measurement comparison shows that the natural frequency of vibration after reinforcement increased to 3960 RPM, raised 180 RPM or 4. 8%, that of the BPF = 2 * RPM excitation frequency stagger effectively and avoid resonance. Total 3 v measuring point vibration from 18. 14 peak reduce to 5 mm/s. 99 mm/s peak, of 67%. 2 * 3570 RPM RPM frequency component amplitude from 16. 51 peak reduced to 4 mm/s. 98 mm/s peak, of 70%. This failure case from rockwell automation ( Xiamen) Co. , LTD. , dalian branch.