Alarm for high vibration levels on the non-driving side of the motor – how to handle it

The Nanyang explosion-proof motor is a large-scale, category 3 motor with rigid support and a solid foundation, featuring a power of 1000 KW and a rotation speed of 2993 rpm/min

Is the vibration at the motor drive end normal? Is the vibration at the non-drive end measured in the vertical direction? Is it a vibration switch or a vibration sensor? Is there a vibration spectrum? As you said, after applying grease, to what level does the vibration decrease? How much more has it increased? What is the vibration level at the motor base? It is recommended to realign the coupling and then check again? Compare with data from debugging

If it is the vibration at the non-driving end of the motor, check for any loose bolts, as such issues can cause vibration. Also, is the bearing not under sufficient stress?

Test the motor alone and compare it with one under load. It is recommended to measure the LQ value to assess the condition of the bearing. If the LQ value is high, it is advisable to replace the bearing; if it remains high even after replacement, then check for alignment issues... Investigate step by step

Check the bearings in the non-driving section

Reply to everyone above: Alignment was checked during shutdown, and it is still within the acceptable range. The virtual angle of the motor was addressed by adding a 0.6mm pad on the right side at the front end; the motor base was also polished to make it smooth. A single test of the motor was then conducted, with a vibration level of 2.7 mm/s at the rear end and 2.5 mm/s at the front end. After operation under load, as the load increased, the horizontal vibration value at the rear end reached the alarm level of 4.0 mm/s (only a remote vibration sensor is installed for the horizontal vibration at the rear end). Some time ago, load-bearing foot adjustments were carried out; the tightness of the anchor bolts only had an effect on the radial vibration levels. Vibrational adjustments were also made to the foundation steel frame using jacks, and the vibration levels decreased in the short term, but after operating for a while they returned to around 4.0 mm/s. Yesterday I replaced the grease in the bearings, and after that the bearing temperature rose to around 75°C, with the vibration levels dropping to about 3.2 mm/s. As the bearing temperature continued to drop, the vibration levels returned to around 4.0 mm/s again. Normally, a value of 4.5 mm/s or less is considered good; the process requirements should be met according to the design values. So we need to discuss the reasons for this, and I would like to hear from everyone if there are any other good solutions.

Around 4 mm/s is actually not considered high. Have you used a handheld vibrator to measure in other directions at the motor drive end and the non-drive end? This device should have been delivered by the manufacturer as a complete unit; what does the manufacturer say?

This post was last edited by Huanghe Gudao on 2019-7-4 at 15:27. According to the standards, a vibration level of 4.0 mm/s is considered good, but this is the value set as the alarm threshold in the design; therefore, it has to be fixed at this level in the manufacturing process. I have already informed the production team that for this motor, a vibration level of below 4.5 mm/s during full-load operation is considered acceptable.

Yes, according to standard ISO10816-1, Appendix B, with a power rating of >300KW, installed on a special frame, it falls under Category III

I believe it’s unnecessary to make mechanical comparisons of vibration standards; if the vibration level rises suddenly, there is definitely a problem with the equipment. As long as the vibration level does not exceed the limit, the current vibration levels will not affect the bearings. It is recommended to run the motor without a load; if the issue persists, replace the motor’s bearings and perform dynamic balancing