Re-insulating cracked old insulated bus bars in an MCC - anyone have an idea on how to do this ?

[bdn2004]

This company has an old Allis-Chambers 480V motor control center at their plant. It feeds the most critical loads in the Plant.
The insulated bus bars are cracked and in pieces.

Is there a way to re-do these? Is there a company that someone could recommend ?

 

[waross]

Time to replace the MCC.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[bdn2004]

You must have always worked on government jobs.
Cause small private companies have this philosophy: if it ain't broke don't fix it.

That's the one idea that's already been eliminated.

 

[waross]

Well, compare the the cost of a new MCC with the labour cost of re-insulating.
And then you have an old, patched up MCC with hard to source replacement parts feeding critical loads.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[bdn2004]

You gotta point.

I wondered if they made some kind of a electrically rated heat shrink plastic or thick tape that could be field installed ?

A concern is that the bus bars are spaced too closely together for it to be un-insulated or they would just take the insulation altogether.

 

[FreddyNurk]

What waross said. There are also opportunities to improve the safety and access to cubicles with a new MCC, which wouldn't be possible by patching up old equipment.

EDMS Australia

 

[edison123]

Heat shrink tubes like this?

https://www.galathermo.com/heat_shrink_end_caps/cable_end_sealing_caps/busbar_tubes.html

Muthu

http://www.edison.co.in

 

[che12345]

Dear Mr. bdn2004

" This company has an old Allis-Chambers 480V motor control center at. ..The insulated bus bars are cracked and in pieces...."
As it is a 480V LV MCC, there are numerous possible options to replace/re-insulate the bus bars which are cracked in pieces:
1) (dismantle) all the cracked bars and re-insulate the bars with [heat shrinkable tube]. For LV, it is NOT costly. The tube comes in different sizes. The shrinkage ratio is usually 2:1. It can be easily done at site. No special tools except an industrial heat blower or a blow-torch turned low to yellow flame (low temperature).
2) (dismantle) all the cracked bars and send them to a powder painting shop to [power coat] them to say (>2mm) thickness.
The major problem with 1) and 2) is you have to [dismantle] the bars. This is very laborious and very time consuming. To cut down the down-time, suggest to applied it on cracked bars only.
3) insulate the crack bars with [self-fusing tape]. It is NOT costly and NO special tools required. [Stretch] the self-fusing tape as normal tape around the cracked bar. After some time, the tape (fused up) by itself into a solid surface instead of layers. Advantage, do not require to dismantle the bars. NOT much labour and short down-time. These tapes are no costly.
3. brush a thick (2-3 mm) layer coat of [thick silicon paint] over the cracked bars. Caution: the paint shall be of a type that offers [high electrical resistance] and shall withstand a working temperature >250deg C when cured. Advantage, not costly, low labour cost and short down-time.
4. Caution: After the re-insulation, irrespective of which method chosen; check the (insulation resistance) [shall exceed >>2M ohm ], withstand a high-voltage test of 2kVrms for a duration of 60s.
In addition, an impulse test voltage of 8kVpeak if you have the equipment. Otherwise engage an outside contractor to carry it out; as it is too costly to procure the test set for (very limited usage).

Che Kuan Yau (Singapore)

 

[waross]

One possible solution is to scrap the vertical bars. Repair the insulation on the horizontal bars and use cable drops the the buckets.
Whether this will work depends a lot on the arrangement and spacing of the horizontal bus.
The number of sections and total number of buckets will also be a factor.
I have used cable drops to repair a section that was damaged by a flashover. Think dust and high humidity.
I did not repair the MCC that was saturated by salt water during a hurricane. Too much labour to strip it down and re-assemble it.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

For heat shrink around bars in place there are several options;
3M
Raychem
Zipper Tubing

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[bdn2004]

Wow these are some good answers, thanks!

Btw I got a little more background on the situation: this is a 9 section MCC, feeding the most critical pumps in the Plant. It’s even alternately supplied by a backup emergency generator.
It can’t be down for any extended amount of time or it can result catastrophic losses. The cost of a new MCC is about $75k. Labor another $75k + engineering, etc....$200k ? It helps justify why they just wanna repair it. They’ve already found and installed new retrofit buckets and new electronics that available for these old units.

 

[LionelHutz]

Maybe

http://phnxmfg.com/

can help. They can manufacture almost any shape of insulation you can come up with so they could make you boots and sleeves you can put over the bars.

 

[jraef]

So what is the SCCR of your antique MCC and is it higher than the available fault current? It’s actually a rhetorical question, an MCC still bearing the Allis Chalmers name is too old to have an SCCR, and chances are that over the years, your AFC has increased, possibly beyond the original bus bracing rating and interrupt capacity of those ancient breakers. So my overall point is that once you disassemble that MCC to re-wrap the bus, you may find yourself in a situation of not being able to legally reconnect it under current codes.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[bdn2004]

Jraef,

You can’t legally reconnect it after it’s repaired? Come on now. Who is gonna bust em ? And under what law ? You can’t repair your own equipment ? Just because something is old doesn’t mean it’s junk.

Even stuff built in the 1950s has a short circuit current rating. Get the classic book by Beeman “Industrial Power Systems” written in 1955. There’s a whole chapter on properly rating equipment.

The only time I’ve ever seen something inspected by a government electrical inspector is something that required a building permit from the start.

 

[Parchie]

@bdn2004 (Electrical),

If space permits, I guess it is more cost-effective to install a separate MCC, perhaps a bit smaller than the old one and transfer little by little the critical loads there. You can do the transitions into a new MCC as time and money permits, IMHO. In my other life, I have recommended a total replacement of a cracked 13.8 kV generator busbar inside a bus duct with cable bussing and got the same "NO" response from the higher management. They ultimately did it when the thing failed later

At least, you be assured of a sturdier and newer MCC than the old one! Doing a cost analysis would tell anybody that the old MCC has already paid back it cost as it had served well in the past. The better philosophy is: "it's better late than never!", Not doing anything to remove an dangerous and outmoded equipment may hit the owners badly if ever. Grab all and you may lose all there, just saying!

 

[bdn2004]

Parchie,

I don’t disagree. But again this a privately owned small company. If you wanna know - they make roofing shingles. It’s a hot, grungy, dirty environment. And these old MCCs are all over the place and working satisfactorily.

I’ve read that many NYC cabs have a million miles on em - they’ve obviously found it’s more cost effective to replace engines and transmissions, etc than it is to buy new stuff. Same thing here.

 

[edison123]

As long as the other hardware like bus bars, MCC's etc. are in working condition, it's far cheaper and easier just to replace the bus insulation by any one of the above methods.

Muthu

http://www.edison.co.in

 

[controlsdude]

Problem with replacing pieces on old equipment is when you come to the conclusion in the middle of it that you don't have a certain hardware or insulator, etc.....

Maybe dedicate someone in plant full time to replace or refurbish parts of the MCC. Give them a budget, plan it out and plan it 2x to make sure its covering all the bases. So at end of it the pieces come back to together and it will work when done.

Since you have stated that the motors and sections of these MCCs are always running 24/7.
Do you have a spare section of a MCC to practice on?

 

[SilverfoxUK]

Not much information given about this board. First call is is it fault rated. In the event of a serious short are you expecting these old bars to hold up safely again many 1000s of amps?

Think of the age of the board, is this thing full of asbestos and what not.

This is time to thank your MCC for its valued service and drop it into the dumpster.

Critical services maybe but not a patch on how critical things could get if you recommend bodging it up with gaffer tape. wouldn't fancy being on your side of the table if Health and Safety People were called in.

Time to change!

 

[bdn2004]

Silver.

I recently worked on a very large expansion For a multinational company. The switchgear they purchased for the new plant, they got it used and had it totally re-furnished as new.
They could afford anything.

Why?

The entire rest of the plant has this same switchgear that Square D decided to quit making a few years ago.

And you can get new breakers even from different manufacturers that fit into the gear.

The retrofit business is booming.

Introducing new stuff into your plant lots of times comes with its own new set of issues you never had before.