The insulated arm that connects to the CBC operator to the movable blades/contacts on this bolted pressure switch (Manufactured by Pringle) is broken. Due to this the movable blases are not hitting the cam stops properly, this is resulting in the blades not being fully closed on "B" phase.
While the broken arm is not visible in the IR opicture it is obviuos in the real time picture. Center bottom red vertical fiber arm. This is extremly critical not just because of the thermal issue (which will only get worse as time passes, if not repaired). But this is a Main Line Service Disconnect on a 2000 Amp 480/277 VAC service, with NEC required GFP. Should this switch try to open from a GFP operation (or human interface) the results could be devasting.
I agree with Mikesh; I'd also get the Pringle rep out to look at it ahead of time so you could get all of the parts needed to fix it ordered and on site before you schedule your shutdown. You should be able to have the POCO pull their OCP, open this guy, then fix this and get the power restored. Based on what it looks like in the picture, you're probably looking at a 6-8 hour outage. I've had decent luck with our local POCO if I ask the lineman to kill the power first thing on his schedule and come back right before the end of his shift to liven it up again.
I stock Pringle parts and do all repairs in house.
The repair consisted of as noted above opening all downstream loads and a utility outage.
Replacement of defective parts, testing the contact resistance of the power contacts (micro-ohm), testing the GFP and meggering the line and load bus (utility disconnected, downstream loads off and GFP control fuses lifted).
I have the complete report in my office I will have to research this. This particular photo was taken in a FLIR proprietary program and the format was not recognizable by photo bucket (at least I was not able to convert it)
If you have a chance, you can pull images straight from the camera before inserting it into one of the FLIR reporting programs and what you see on the camera is what you will see in the image you pull off of it. Just FYI.
My office is also in Sterling (I don't like a long commute, hence living in the same town). I have actually been by your shop to pick up a ground fault relay and various other parts to repair problems like you found. Is this one of the nightmare to shutdown government/gov. contractor buildings in the region? If so, have fun scheduling the shutdown! Often they don't seem to understand that it's not an IF it fails, but a WHEN it fails issue.
When the customer balks at repairing the switch just explain how many days or weeks they will be out when it fails or their liability exposure should it blow when someone tries to operate it and the lawyer finds out they knew there is a problem. Of course that is assuming the building survives the fire. The hardest part of any of these kinds of discoveries is the amount of time to failure and expressing that to the customer who will naturally want to wait as long as possible (read forever). No one actually know how long the customer can go before there is a deadline.
I generally shrug and tell that it's their call. They can schedule the 8 hour shutdown at their convenience or call me in the middle of the night during their busiest season and we'll start the clock running on their 1-2 week outage...and the estimate that I gave them won't be valid.