I need experts to help analyze the reasons for the high vibration of the Roots blower and the short operating life of the coupling.
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The coupling is a single-diaphragm coupling, with a diaphragm spacing of 0.5 mm. It made unusual noises after being in use for a year. The fault symptoms are cracked diaphragms and worn bolt holes. The maximum vibration at the axial position of the positioning bearing is 25 mm/s. After the rotor was replaced during this maintenance, the vibration rate was 15 mm/s; the vertical direction also showed 10 mm/s, while the support bearings had a vibration rate of 5 to 6 mm/s.
Re-center it, and then measure the motor current and vibration
This problem has occurred with the couplings in recent years, not just during this maintenance work.
In recent years, the vibration level has been around 20 mm/s, so the rotor was replaced. After the replacement, the axial vibration of the positioning bearing was still at 15 mm/s, and the vertical vibration was 10 mm/s; the supporting bearing exhibited a vibration level of 5 to 6 mm/s, while the vibration of the machine frame was 8 mm/s.
For diaphragm couplings, the standard configuration consists of two diaphragms; this type of coupling requires less precision regarding the pump’s alignment, as the two diaphragms help to absorb shocks, and it also falls under the category of elastic couplings. In the case of a single-diaphragm coupling structure, it behaves like a rigid coupling; it requires high precision in alignment and has poor shock-absorbing capabilities. Moreover, rotary vane pumps generate more noise and vibration during normal operation compared to centrifugal pumps. Therefore, single-diaphragm couplings are not recommended. It is recommended to use elastic pin couplings.
Regarding the issues raised, it’s necessary to first clarify and sort them out. “It made unusual noises after being in use for a year. ”Was the vibration anomaly caused by component damage that occurred after a year, or has it been like this throughout that year? If it is the former, the vibration caused by the replacement part should be eliminated. If it is the latter, a comprehensive inspection should be carried out. Such as the stress of the anchor connections for the unit rotor, bearings, and corner bolts, as well as inspections of other components. It should be determined whether it is these factors that caused the component damage. Also, are the data you have measured within the normal range? Also, if the bolt holes become worn, it is necessary to replace the coupling and the pin bolts.
It is recommended that you perform dynamic balancing on the rotor! We have made two before
Okay, thank you. I will first discuss the coupling configuration issue with my supervisor; it depends on their decision. Could you also tell me what causes large vibrations?
The phenomenon falls into the former category; after one year of operation, abnormal noises occurred, prompting maintenance and the replacement of the coupling.