Opening XFMR's live

[Brandon Loyd]

We perform a lot of Infrared/PM work at various facilities in California. When working at a hospital yesterday, our customer says he was told by another IR contractor that they would not open any live XFMR's because it was an OSHA violation. I have asked others and the response I recieve is that it is not in violation of FED OSHA or NFPA 70e. I was hoping someone could confirm that this is not in violation of CAL OSHA, as they seem to be more strict in a lot of cases.

 

[roger]

I don't have any idea of what CAL OSHA's rules are but, I can't imagine there being a blanket rule prohibiting opening electrical equipment. If the proper PPE and procedures are followed there should be no problem

If for some reason this was the case your IR people and equipment could be discarded and there would not be any reason to own any meters either.


Roger

 

[j rae]

proper ppe

proper ppe

DEPENDING ON THE VOLTAGE YOU MUST WARE THE PROPER PPE FOR THAT VOLTAGE.

 

[charlie b]

The "proper PPE" is not a function of voltage alone. And please do not type in ALL CAPS. It makes the post harder to read, and is considered impolite, as though you were SHOUTING at us.

 

[zog]

Charlie, sometimes I think we share a brain.

 

[iwire]

Which live work 'exception' applies to looking at a transformer?

Is that troubleshooting?

I think it would be troubleshooting unless it has to be defended in court and then maybe not.

 

[renosteinke]

I think we're missing the elephant in the room.

OK, so they want to look for hot spots with the IR ... I get that, and I can see why shutting the transformer off, even for a moment, would skew the readings. BUT...

The usual indoor transformer has a front panel that you need to rock/tilt a bit to slide off- and that action puts you way too close to the windings for my comfort. I've heard tales of folks who tipped the cover just a tad too much, and got a nice light show. As a result, I consider the removal of such a panel to be absolutely unsafe 'hot,' no matter what you're wearing. Transformers really aren't designed to ever be opened for inspection or servicing. That sheet metal flexes, has sharp edges, and no handles.

This contrasts to the usual padmount PoCo transformer, which has hinged doors protecting the connections. I note that PoCo personnel wear full PPE when they open these doors, even when using a hot-stick as well. I can see such a transformer being inspected.

 

[zog]

I think we're missing the elephant in the room.

OK, so they want to look for hot spots with the IR ... I get that, and I can see why shutting the transformer off, even for a moment, would skew the readings. BUT...

The usual indoor transformer has a front panel that you need to rock/tilt a bit to slide off- and that action puts you way too close to the windings for my comfort. I've heard tales of folks who tipped the cover just a tad too much, and got a nice light show. As a result, I consider the removal of such a panel to be absolutely unsafe 'hot,' no matter what you're wearing. Transformers really aren't designed to ever be opened for inspection or servicing. That sheet metal flexes, has sharp edges, and no handles.

I agree, not to mention the secondary side of a MV/LV transformer and transition section is a blind spot to protective devices and you often find arc flash levels greatly exceeding values where PPE can offer protection. So we have what is likely the greatest hazard (Highest Ei in the system) combined with a very high risk (pulling bolted covers very close to energized parts with so many things that could go wrong). Either skip them, or install IR windows in these sections.

 

[Brandon Loyd]

There are safer ways to remove XFMR covers than what is listed above that I will not spend time on. I am wanting to know if anyone knows of a jurisdiction in California, namely hospitals, that does not allow the removal of XFMR covers live, as a RULE.

 

[renosteinke]

I'm sorry to hear that, Brandon.

I will grant that there are many different transformer designs out there, and some allow you quite easy access to the connections, with little risk of your having an "oops" moment.

Yet, the transformer that comes to mind when I think of an indoor transformer is the gray cube, about half the size of a desk. Those transformers typically have a sheet metal panel thet angles 'in' near the top. To remove this cover you must remove several sheet metal screws, then slide the panel up before you can pull it away from the transformer.
Since the panel lacks any handles or 'stops,' it's quite easy for the panel to slip down- putting the inward sloping part in contact with the windings. Or, when you 'rock' the cover slightly to get it out, that sloped part can easily rotate down into the windings. While I've never tried it, I doubt that the paper and varnish mixed in with the windings are very good protection against that sharp sheet metal edge.

Add to this the rather cramped locations where many transformers are placed, and it's hard to get a helper in there with you.

If you have any suggestions for removing these covers in a safer manner, I'm all ears.

 

[iwire]

If you have any suggestions for removing these covers in a safer manner, I'm all ears.

An IR guy I used to work with would pull the tops off, typically very easy and away from live parts.

Once that was done they could take the IR shots from the top.

 

[renosteinke]

I had not thought of that ... I'll have to look at some of my customers' tranny's today, and see if that can be done.

 

[zog]

Much safer to install IR windows, saves a lot of time in the future for IR scans too. We installed maybe 300 so far this month at various facilities, it is becoming a common solution to this problem.

 

[jdsmith]

I'm reviewing bids for 30 kVA and 75 kVA dry type transformers right now. One of the manufacturers states on the transformer nameplate: "DE-ENERGIZE TRANSFORMER BEFORE REMOVING COVER"