Pipeline pumps come in two forms: vertical and horizontal. Usually, pipeline pumps use a vertical structure and are installed in the middle of the pipeline, with the inlet and outlet in the same parallel position. Pipeline pumps are divided into fluoroplastic pipeline pumps, stainless steel pipeline pumps, and cast iron pipeline pumps. How to solve vibration and faults in the use of vertical pipeline pumps? Here are some examples:
1, Overview of faulty equipment
The vertical pipeline pump motor drives a shaft with a length of 1879.6 millimeters, a shaft diameter of 88.9 millimeters, and a wall thickness of 2.4 millimeters. The number of blades in the impeller is 2. The vertical pump has experienced multiple pump shaft fractures, with the fracture located close to the impeller compression nut. The fault phenomenon is that the initial vibration is high (at 3V and 4V), and the impeller compression nut is loose. Subsequently, adhesive the impeller with epoxy to tighten the nut, which can effectively prevent the nut from loosening. However, many pumps later suffered catastrophic damage due to impeller shaft fractures.
Decided to conduct monitoring analysis: measuring vibration; Assess the severity of vibration; Diagnose potential faults; Propose effective troubleshooting measures.
2, Vibration measurement data and fault analysis
1. The vibration measurement shows that the 3V and 4V measuring points have high vibrations. In the 3V measurement point spectrum, the amplitude of the 2 * RPM frequency 3570rpm component reaches a peak of 16.51mm/s, while the amplitude of the 1 * RPM frequency component is only 4.60mm/s. Attention: The number of blades in this impeller is 2, and the blade passing frequency is BPF=2 * RPM.
2. Hammer impact test results: Use the hammer impact method to test the natural frequency of the motor, shaft, and pump. The natural frequency test spectrum of the 4V measuring point shows that the dominant natural frequency is 3780rpm, which is only 210rpm or 5.9% different from the vibration frequency component 3570rpm=2 * RPM=BPF of the blade passing frequency (BPF) of the pump impeller measured during operation. In addition, there is also the natural vibration frequency of the 2009 rpm shaft protective cover. Due to the natural vibration frequency of 3780rpm being too close to the blade passing frequency of the pump impeller or twice the pump speed frequency of 3570rpm, it is easy to trigger resonance in the pump system. Therefore, the test uses a reinforced pump system to support stiffness and change the system's natural frequency ("frequency modulation") to avoid resonance.
3, Fault handling and effectiveness reinforcement plan
The comparison of vibration measurements before and after reinforcement of the pump system shows that the natural vibration frequency after reinforcement increases to 3960rpm, an increase of 180rpm or 4.8%, effectively staggering it with the BPF=2 * RPM excitation frequency to avoid resonance. The total vibration of the 3V measuring point decreased from a peak of 18.14mm/s to a peak of 5.99mm/s, with a decrease of 67%. The amplitude of the 3570rpm component at a 2 * RPM frequency decreased from a peak of 16.51mm/s to a peak of 4.98mm/s, with a reduction of 70%.