Drying out Wet Bus Duct

[ee4fire]

Has anyone ever heard of or used a "baking" method to dry out bust duct that had water intrusion? If so, who are the companies that perform this type of work? I do know that manufacturers do not extend their warranties on bus duct that has been "baked" or dried.

 

[mike7330]

http://www.nema.org/stds/water-damaged.cfm

 

[brian john]

The problem with drying busway is.

It can take considerable time.
The dirt that deposits on the insulators and exposed busway (in joints and at openings for switches/ CBs) is a conductor dry it may read acceptable or close to acceptable, with an increase in humidity this dirt can become a conductor.
The steel casing will continue to rust.


I have the NEMA specs in the office I forget what NEMA stance on this is. But most manufactures are in business to sell busway, so accepting drying might be unacceptable.

Having said all this, I have worked with firms that dried busway.
Stripped all switches and buckets.
Dehumidifiers and heat in every electrical closet.
Energized busway at LV with a variac and increased voltage over a period of time as megger readings improved.

I prefer replacing.

 

[hurk27]

The problem with drying busway is.

It can take considerable time.
The dirt that deposits on the insulators and exposed busway (in joints and at openings for switches/ CBs) is a conductor dry it may read acceptable or close to acceptable, with an increase in humidity this dirt can become a conductor.
The steel casing will continue to rust.


I have the NEMA specs in the office I forget what NEMA stance on this is. But most manufactures are in business to sell busway, so accepting drying might be unacceptable.

Having said all this, I have worked with firms that dried busway.
Stripped all switches and buckets.
Dehumidifiers and heat in every electrical closet.
Energized busway at LV with a variac and increased voltage over a period of time as megger readings improved.

I prefer replacing.

We used a welder once to dry out a 250' long buss duct that was soaked when an old metal roof started leaking right into it at first it just blew the 3k amp fuses at night when the plant was shut down, so when we can in on Monday we had no power for the MDPs fed from it, and when we investigated as to why the fuses failed well it was self evident when we walked the duct down and found water all over the place about at the 235' mark of the run, the amount of ruse that ran into the buss is what got the fuses so we had to open that section and clean it out and we had 4 or 5 insulator knobs we had to replace, so our plant EE came up with this idea if a welder can be used to thaw out frozen water pipes in a house or underground, it should work for this, we removed the cables feeding it from the service and bonded A to B together at the east end with a jumper from C to the building steel and took one of our Hobart motor generator welders with a very high amperage capacity (1200 amps) over to the other end and lugged B to C, and bonded the work lead to the building steel and the stinger lead to A to put all three phase in one big series run, with the amperage all the way down we slowly brought it up till the IR thermometer read 150? we kept an eye on it and let it bake for about 4 hours, after that we megged it out, put a large drip pan over the buss at the leak point which had stopped because the storm moved on, and put it back in service, lasted about two years before it just let go and started a ball of arcing that literally burned all the way up to the point of the multiple parallel 1k MCM conductors that just fell apart, funny thing was only one of the three fuses opened in all the arcing, and there was no buss-way anymore all splashed on the floor as melted globs of copper and tin from the casing, all we could do was used welding glasses while manning CO2 extinguishers to put out the little fires that was breaking out from a few stock piles of cardboard stock for shipping box's

 

[brian john]

We were called to a site where a contractor Hi-potted the busway hoping that would dry it out. 64kv on 600 VAC busway.

 

[petersonra]

I think there is a big difference between prolonged submersion and incidental exposure to water.

I am very suspicious of being able to ever reuse something that has spent 2 weeks under water.

Something that had some water drip on and into it is something that can probably be reused in most cases, with possibly some minor repairs.

There is a wide range of situations that span the gap between those I mentioned above. I am not sure there is anyway someone from the outside looking in can tell you what the appropriate solution is.

I am somewhat suspicious of using heat. I would be inclined more toward draining the water out and then rinsing the inards out with IPA, followed by forced air drying. But, that is a lot more work than just applying heat, and may not be all that easy to do in some cases.

 

[jumper]

What is IPA? Google drew a blank.

 

[n1ist]

Isopropyl Alcohol
/mike

 

[weressl]

We were called to a site where a contractor Hi-potted the busway hoping that would dry it out. 64kv on 600 VAC busway.

Perhaps he was trying to fail the bus, so there is no question.:lol:

(Hi-Pot equipment drives no substantial current, which is needed to produce heat. See the examples of welding machine use for that purpose, where voltage low and current high. Exact opposite of Hi-Pot equipment.)

 

[brian john]

I think there is a big difference between prolonged submersion and incidental exposure to water.

I am very suspicious of being able to ever reuse something that has spent 2 weeks under water.

Something that had some water drip on and into it is something that can probably be reused in most cases, with possibly some minor repairs.

There is a wide range of situations that span the gap between those I mentioned above. I am not sure there is anyway someone from the outside looking in can tell you what the appropriate solution is.

I am somewhat suspicious of using heat. I would be inclined more toward draining the water out and then rinsing the inards out with IPA, followed by forced air drying. But, that is a lot more work than just applying heat, and may not be all that easy to do in some cases.

One of the worse busway explosions I have seen was a drip on a 90 degree elbow. Blew up (vaporized) 30' of busway and blew every 90 degree bend out the full lenght of the run (maybe 8-10). The straight portions meggered OK, but all was replaced.

Hard for the average contractor to dip 285' of 4000 amp busway.

Drying has been used for years, I am not a big proponent of drying, but it seems to work, WELL until it goes boom.

 

[weressl]

I think there is a big difference between prolonged submersion and incidental exposure to water.

I am very suspicious of being able to ever reuse something that has spent 2 weeks under water.

Something that had some water drip on and into it is something that can probably be reused in most cases, with possibly some minor repairs.

There is a wide range of situations that span the gap between those I mentioned above. I am not sure there is anyway someone from the outside looking in can tell you what the appropriate solution is.

I am somewhat suspicious of using heat. I would be inclined more toward draining the water out and then rinsing the inards out with IPA, followed by forced air drying. But, that is a lot more work than just applying heat, and may not be all that easy to do in some cases.

The optimum solution is to remove the buswork, disassemble it and dry it ovens, Megger, then re-assemble it. It may seem lengthy and labor intensive, but it will assure maximum service life and reliability.

In todays manufacturing environments, where competitiveness is assured by lean practices, (maximum) availability is the key.

This may seem costly but IMO it is the best alternative to replacing it with a new bus-duct.

I presume - since the OP does not elaborate on this - that this is a LV <1000V bus duct. MV voltage bus' would have additional considerations to be given.

Older LV sandwich type busducts used to use multiple layers of thin, mika-like sheets between the bars and those would be 'excellent' water-trap. Late manufacturers use either epoxy coated or bare bars, braced and held apart by rigid insulating 'combs'. These would have fever places to retain water. Look for materials in the construction that would absorbe and retain water.

Look for the potential water-traps in any construction and see if you can figure it out what method will remove the water and contaminants with the most assuredness and make your decision accordingly. IPA is a good water repellent/displacer, so is silicone.

 

[ritelec]

Has anyone ever heard of or used a "baking" method to dry out bust duct that had water intrusion? If so, who are the companies that perform this type of work? I do know that manufacturers do not extend their warranties on bus duct that has been "baked" or dried.

Not sure, However, tape recordings in the 70's and 80's became corrupt. I baked a few tapes, .....why not buss bars?????



Cause music can't KILL you or burn a building down............


Depends what what in the water if you wanted to dry things out out reckon.

 

[weressl]

Not sure, However, tape recordings in the 70's and 80's became corrupt. I baked a few tapes, .....why not buss bars?????



Cause music can't KILL you or burn a building down............


Depends what what in the water if you wanted to dry things out out reckon.

Heating is one way to demagnetize items and surely low level magnetization like the ones can be found on tapes can be surely damaged by heating them.

 

[ritelec]

Heating is one way to demagnetize items and surely low level magnetization like the ones can be found on tapes can be surely damaged by heating them.

baking also gets rid of "sticky shed".....(moister in tape binder)..................smoogy...................yukky stuff.

 

[zbang]

baking also gets rid of "sticky shed".....(moister in tape binder)..................smoogy...................yukky stuff.

Yep. 'Baking' is a misnomer, it's really warming the tape to about 150-170degF to drive off the water.

 

[ritelec]

Yep. 'Baking' is a misnomer, it's really warming the tape to about 150-170degF to drive off the water.

Yes, Kiss and a few others had corrupt tape. They had a gent do some baking when this was first happening. He was local to me so I had him do mine as I was first going to attempt in myself............

My songs suk ....but was able to get them digitized into my computer ...... no sticky tape syndrome there............

Just wondering about the "misnomer" word. If something is set in an oven at 150 or 350 for a period of time, is it still not baking.

Maybe the term "baking" just relates to food ?????

 

[hillbilly1]

I quoted replacement of all gear and starters in a water park wave pool, someone in maintenance had shut off the sump pumps when they closed for the winter, when they came back in the spring, the electrical room, which was underground was in 7' of water. The ceiling and walls were black from months of arcing, as the poco transformer remained hot. Another contractor told them they could dry it out, and not have to replace a whole lot of the equipment. Of course we lost that bid because that was much cheaper. The next year they had on the news about an electrical fire in the park. I did not find out where in the park it was, but I had a pretty good guess. :roll:

 

[ritelec]

oh my

 

[brian john]

We had a water park that had a vault with a 150 KVA transformer, they poured the vault in place no opening big enough for the transformer. We replaced all other equipment and cleaned and dried the transformer over the course of 7 days, heaters, dehumidifiers and fans. Megging every 24 hours.