Electric motor vibration analysis...  - Page 1
Forum section: electronics / general

author: Precisiontools
author_rank: Regular Contributor
timestamp: June 07, 2012, 03:39:46 am
content: Anyone here involved in this type of work? Maintaining and preventive maintenance on AC motors in an industrial environment? I've got the basics but want to delve a bit deeper. What's the industry standard with test equipment? What equipment do you use? Test intervals? On-line resources?Thanks in advance

author: Galenbo
author_rank: Super Contributor
timestamp: June 07, 2012, 06:39:31 am
content: We used a portable Schenck Vibrotest for regular non-permanent measurement, on-site, on the customers installation. Sensor was decent, magnetically attached. The machines turned permanent 24/24.Both Horizontal, vertical and axial on each +-200mm bearings. The device was a data collector. It performed FFT on the vibration and stored different results per measurement. RMS, peak, SR.On the office the "results" were automatically stored in a database.The results of 1 Machine said nothing. Comparing data between identical machines also absolutely said nothing. Comparing data of 1 machine, time interval, said sometimes everything.-values of a (later detected) defective machine were often lower than the values of a perfect machine.-values only increased shortly before bearing defect. Seemed to increase exponential.-sometimes the measurements of another bearing than the defective one, increased.-often a measurement was false, this also entered the database.-temperature was a huge variable, made measuremnts completely different.Our conclusion was:We can't rely on conclusions, made with the database. It's good to have a general view, but we can't predict problems. Even when the values are different, maybe it's a wrong measurement, and we still don't know witch bearing causes problems.My personal conclusionis that, when you want it to be relyable, the sensor has to be always-mechanically-attached, (not magnetic ones) and the measurement has to be done permanently. Not only peak, and RMS, butt all the ones. This has to be stored in a local database per machine, so you can see trends, differences winter/summer, some machines have full-load/on/off/standby/reverse operation, this also has to be logged. Also greasing the bearings gives huge temp/vibration differences. So, also log maintenance events.Such complete solution could predict problems.

author: qno
author_rank: Frequent Contributor
timestamp: June 07, 2012, 07:34:39 am
content: Great stuff, very informative, thanks.You still work there. I have been thinking about placing vibration sensors on motors.Do you still work there?

author: EEVblog
author_rank: Unknown
timestamp: June 07, 2012, 08:19:53 am
content: In vibration work, Bruel & Kjær have been the industry leaders for many deacdes:http://www.bksv.com/Very expensive stuff though.Dave.

author: Precisiontools
author_rank: Regular Contributor
timestamp: June 11, 2012, 09:31:44 am
content: Thanks for the replys.

author: Galenbo
author_rank: Super Contributor
timestamp: July 19, 2012, 05:42:04 am
content: Quote from: qno on June 07, 2012, 07:34:39 amNo. This was part of the nicest job I ever had.Then there was more management, other management, "everywhere" management.Mission statement, objective review, efficiency evaluation, more ERP/SAP, ...All the collegues, better/smarter/prettier than me, left. Then I left. 10 months later the company went bankrupt.I guess since then the managers are on a new hunt, for eating/destroying something good&nice..