Consulting about high-frequency vibration speed pump issues
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This post was last edited by 156026692 on 2019-3-19 at 20:58. Dear experts, I have several old units here that have been in operation for over 20 years; some of these pumps experience high levels of vibration. The pump maintenance team has done everything necessary to repair or replace components as required, but the vibration levels remain high. I measured it with a spectrum analyzer, and the main component was not the first or second harmonics, but the third harmonic. Therefore, attempting to carry out repairs based on the usual symptoms of imbalance or misalignment will not actually solve the problem. I would like to know: when encountering pump systems with high levels of vibration, where the dominant vibration frequencies are third harmonics, fifth harmonics, and other higher-order harmonics, what approaches do you use to diagnose the issue and find solutions? ? On my end, I have checked and taken care of everything that needs to be checked: the inlet filter, stress inspections at the pump’s inlet and outlet (including re-piping and rewelding of the flanges), pipe supports, anchor bolts, and so on. . . Regarding the process flow, process deviations such as using excessive force for a given task or cavitation and vaporization are also hard to explain (for pumps of the same model connected to the main pipeline via two separate paths leading to the pump inlet, the process flow is relatively simple); one pump operates normally, while the other experiences vibrations of over 4.5, or even 7.1 mm/s (the LQ value of the bearings is normal, so vibration caused by bearing problems can be ruled out). As an aside, due to limited funds for repairs and replacements, there is currently no opportunity or time to purchase new pumps in the short term. I’d like to know if anyone has encountered similar problems with high-frequency vibration speeds in pump systems; thank you all!
This post was last edited by 156026692 on 2019-3-20 08:22: 1 Poor coaxiality; 0.2 blockage in some of the impellers leading to imbalance; 3 Damage or bending of the impellers or shaft; 4 Imbalance of the impellers; 5 Unstable foundation; 6 Worn bearings; 7 Incorrect support for the inlet and outlet pipes; 8 The pump is cavitated and emptied
A rich liquid pump for a desulfurization unit.
Add me on WeChat or send it to my email ahcybf@qq.com so I can take a look. The signature includes contact information.
Is there an inevitable relationship between the number of blades and the high frequency in an 80AY type liquid-rich pump? ? ? If there is indeed a relationship, is it possible to make modifications to improve the excessive vibration? Thank you!
1. Unbalanced mass of the pump shaft 2. Misalignment of the pump shaft 3. Mechanical looseness, cracked base, loose bolts, etc. 4. Bearing failure
The 80AY100 model should have 3 blades, and each blade may generate impact at the blade-cutting position
For general information: The LQ method – a technique for detecting the condition of rolling bearings. Theory and practical measurements related to the inspection of rolling bearings show that fault frequencies in these bearings fall within the high-frequency range. The LQ method involves measuring vibrations in the frequency range of 600 Hz to 10 kHz and applying special processing; all vibrations caused by mechanical faults such as imbalance and misalignment are filtered out by band-pass filters. The LQ method also reflects the bearing lubrication condition; poor lubrication leads to an increase in the LQ value. Machine speed, power, and bearing size have almost no effect on the LQ value. Define two operating states of bearings: good and poor. 1. A bearing in good condition with proper lubrication has an LQ value of 2; in such cases, the bearing should be replaced.
Multiple harmonics arise mainly due to the periodic effects of the structural characteristics of the rotating components; for example, if there are 3 impeller blades, the vibrations will be primarily at the third harmonic. What Superfoam said is correct – the position of the pump’s partition (its shape, size, angle, defects, and wear) should be carefully examined