Motor Reliability Statisitcs

[Steventyj]

I am working in a pulp mill and it would be usefull to know if the percentage of failures that we experience due to certain causes, such as bearings, are online with what other plants are experiencing. For example if we had 70% of failures from bearing problems and the rest of the world had on average only 40% of failures caused by bearing problems then we would know to concentrate on breaings to improve reliability. Does anyone know of surveys/research that quantify failure rates?

Thank you,

Steven

 

[jbartos]

Suggestion: This topic appears to be more on a confidential side. It would be better to contact a similar plant chief electrical engineer and share your results on confidential basis. Although, there might be some statistical survey data available.

 

[Shortstub]

Steventyj,

1) Get IEEE Std 500, covering Equipment Relaibility Data for the Nuclear Industry. Although its data base was relatively small, representative data is a good starting point.

2) In the 80's I was involved in a Probabilistic Risk Assessment (PRA) for a very large HPI complex. I'll try to find the data.

3) An article recently appeared in "Maintenance Technology Magazine." Maybe, ithin the last 6 months? (I'm over forty so the memory, and other attributes, are not what they once were). It showed that across the board bearing failures were responsible for about 51% of all motor failures. You might want to check it out. Perhaps the author will reveal failure-rate data by industry.

4) Jbartos's commment has validity. In fact, did you know that IEEE Std 500, was produced by anonymous contributions of raw data?

 

[electricpete]

The IEEE Gold Book (IEEE493), Appendix H has an extensive survey on tabulating motor failures.

One statistic they report among the population they looked at (I can't find the motor-years off-hand but I know it's in there). Induction motor failures broken down as follows:
152 bearing failures
75 winding failures
8 rotor failures
19 Shaft or coupling failures
10 external device failures (?)
40 failures - not categorized.

I would think that for bearings in particular the definition of a failure is tricky. Many bearings are replaced based upon vibration readings on a planned basis without causing an unplanned outage. To me that is in keeping with a strategy of condition-based maintenance. Does it count as a failure?

 

[Shortstub]

Steventyj,

My memory wasn't as good as I thought!

The PRA study covered HV (230kV), MV (15kV) and LV (480V) distribution systems. Included were utility supply, in-plant generation, breakers, transformers, and cables, but no motors.

 

[AussiePete]

Shortstub,
I'm interested in the PRA study as I'm involved in a new installation with HV switchgear, transformers etc. If I could locate areas that need to be inspected better it would be helpful.
Perhaps you could provide me with a link thanks.

 

[Shortstub]

AussiePete,
Latest paper I presented was:

"Probabilistic Risk Assessment of Equipment Safety Systems"

Presented in the "Hazard Prevention Magazine"

The Journal of the System Safety Society, Vol 35, No. 3, 3rd Quarter, 1999. Their website is:

http://www.system-safety.org

The references contained therein were also used in the HPI plant in 1982.

 

[neps3]

Steventyj

There are several artciles written on survey reports. Please obtain this artcile which will give you an idea.

1.
"Assessment of the reliability of motors in utility applications - updated" by PF.Albrecht, JC Appiarius and DK Sharma, IEEE Transactions on Energy Conversion, Vol.EC-1,No 1 March 1986.

2.
Report of large motor reliability survey of industrial and commercial installations Part 1&2 by Motor reliabilit working group IEEE Transactions on industry applications, Vol 1A-21, No 4 July/August 1985.

Regards

 

[jbartos]

Suggestion: A type of motor shaft load has impact on the motor bearing, e.g. crusher motor needs special bearings. The pulp mills tend to have many rolling cylinders; some of them are propelled by motors. A motor with the pulley and belt appears to be the most gentle load transmission on the motor bearings.

 

[Steventyj]

Thanks for all the replies. Of course what really matters is that in a specific plant reliability can be increased, but it is good to have an idea of how you compare to other users.

 

[GusD]

There are several statistycal tables listing electrical motor failures and its related causes.They range for the most part as 50 to 70% failures from bearings,20 to 30% windings and 5 to 10% for other causes.(friendly fire I called 'em)Self induced.
I work with a Reliability/Rotating Equipment group and our experience within our mining operation is probably a 60% /30% /10% for bearings/windings/others.
Relatively speaking,the failures we experience when compared with the large amount of motors we use,it is really small.Our Condition Monitoring efforts ,play a large part on keeping these numbers at a minimum. GusD

 

[Squiggly]

There is a reasonable data base of failure rates of many different types of equipment under different operating conditions at

http://www.weibull.com.

Use of these figures is pretty subjective but I have found this facility extremely useful, particularly if dealing with fairly large populations of similar machines as you probably are in a paper mill.

Regards

Phil Scott

 

[jbartos]

Suggestion: Visit

http://www.ga.com/triga/triga_italy...a Collection and Processing for Romanian .doc

etc. for more info