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 Post subject: Labelling for maintenance condition
PostPosted: Tue Mar 14, 2017 12:07 pm 
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I'm hearing there are upcoming changes to NFPA70B that will require labeling of panels to indicate maintenance condition. Does anyone have specific details of this?


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 Post subject: Re: Labelling for maintenance condition
PostPosted: Wed Mar 15, 2017 11:48 am 
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Location: North Carolina
There was a suggestion in the current version to put stickers on the equipment with dates from the last time it was tested. This is pretty common practice along with the company name and phone number as free advertising to try to ensure repeat business.

The standard I remember really had 3 labels. A "good", a "failed", and a "seviceable with issues" type of label. For instance on a circuit breaker a "serviceable" type of sticker might be used for one where an indicator light is burned out or maybe even for a trip unit out of calibration but where it is tripping too quickly instead of too late.

Remember though that despite how simple it seems, "maintenance condition" is very hard to actually define. A number of standards, especially military standards, have been established to attempt to estimate equipment reliability quantitatively and so far for the most part, these efforts have failed miserably. The best research to date shows that maintenance condition is partly due to the equipment design and manufacturing process, but is equally if not mostly a product of the environment (condition of use). Thus so far the best way to estimate "maintenance condition" is by monitoring the equipment while in service. Unfortunately even that too is a problem because many of the key performance attributes of the equipment are almost impossible to measure in service. The best test for the majority of issues with electrical equipment is visual inspection but since this can be highly subjective, again there's just no good way to do it. I have for instance seen an extremely good visual identification procedure for polymeric insulators put out by EPRI for classifying the maintenance condition of those and it results in a very nonsubjective result. Similarly, the degree of sparking on a commutator for a DC motor is pretty easy to score visually and is very nonsubjective. But outside of a few isolated cases there isn't a good scoring system for electrical equipment in general.


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