Connecting to tubular copper bus
Connecting to tubular copper bus
(OP)
We have some 3000amp rated, tubular copper bus work. Any suggestion on a good way to cut out a ssection, then put it back in? A splice you might say, between tubular, 3"square x 1/4" thick copper bus.
Can copper bus be "welded" ? If so, what would be the best way? Or should "splice plates" be bolted or welded on all sides, equal to the amp rating?
Or should a piece, manufactured to be just slightly larger then the outside diameter of the bus be fabricated, and then bolted or welded together?
I'd like to hear peoples suggestions.
Let me know if you need anymore info.
HP
Can copper bus be "welded" ? If so, what would be the best way? Or should "splice plates" be bolted or welded on all sides, equal to the amp rating?
Or should a piece, manufactured to be just slightly larger then the outside diameter of the bus be fabricated, and then bolted or welded together?
I'd like to hear peoples suggestions.
Let me know if you need anymore info.
HP






RE: Connecting to tubular copper bus
As for the other details, anything that provides sufficient cross sectional area of copper should work.
RE: Connecting to tubular copper bus
My suggestion would be to contact the OEM, if that is possible. Out of curiosity, why is this "splice" necessary? If it is do to a failure, I would recommend replacing the entire damaged section instead of attempting a repair.
You did not mention the applied voltage of the bus. I would be even more cautious of a field repair of the type you mention if the equipment is rated for medium or high voltage. While it is true 3000 amps is 3000 amps, bus failures in medium and high voltage equipment are far more devastating and costly than low voltage equipment.
As far as the mechanics go, I personally would be more comfortable with bolted connections if I had to make such a call.
Bigbillnky,C.E.F.....(Chief Electrical Flunky)
RE: Connecting to tubular copper bus
You probably know that tubular copper and aluminum bus is often manufactured to Iron Pipe Sizes. Hence the designation, "IPS bus"
If you must weld, check with your favorite refrigeration man. Refrigeration mechanics use a special type of silver solder that will weld copper without flux. It's stronger than copper and has a good wetting action. It is quite easy to use. You're probably going to need a large torch to get 3" IPS bus hot enough, but it's do-able.
If you decide to go with a mechanical joint, the web sites below may be able to supply ready-made, bolt together hardware.
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http://www.dossert.com/products/eproducts.htm
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respectfully
RE: Connecting to tubular copper bus
Wow, Waross, those links are great. I'll check them all out.
I can't see how just soldering this bus would be sufficient. But since you say the solder is actually stronger then the copper, I guess Im wrong. I am partial to a bolt together system, if rated properly.
Replacing the entire run is out of the question, it's a 300' run X 3, 30 off the ground in an enclosed busway
The piece might need to be taken out, to change the way it is fed.
The voltage is 7kv. Bus must be rated to 3000 amps
HP
RE: Connecting to tubular copper bus
RE: Connecting to tubular copper bus
Even though the welding joint is perhaps the most expensive process, this method provide the best results with minimum joint losses, virtually no maintenance and the most important, do not impair the current carrying capacity of the busbar, particularly for high current above 3000 A.
The preferred methods to weld copper busbars is using inert gas process with shielded arc, tungsten or metal inert gas.
COMMENT: Regardless the jointing method selected, the busbar system should have minimum electrical resistance and capable to withstand the maximum mechanical stresses produced by short circuit, wind, snow, seismic and any other load combination.
- Provision for thermal contraction and expansion should be considered in the design to avoid transmission of excessive forces over insulators and other fragile components.
RE: Connecting to tubular copper bus
I understand that the joint used in refrigeration is brazing rather than soldering. I am under the impression that it actually alloys with the copper, and results in an alloy that is stronger than the copper. The name was Silfos or Silflos. It was similar to silver solder but would join copper without the need for flux.
I haven't used it for many years and the formulation may have changed.
The formulation that I used years ago took a higher temperature to melt than it did to form the original joint. The product is probably new and improved now.
I misunderstood you and thought you were trying to connect Rround tubular to 1/4' flat plates. My mistake.
I am with you on the bolt together system. My first choice would be a manufactured, approved connector, IF one is available. Will clearances be a problem or do you have lots of space?
respectfully
RE: Connecting to tubular copper bus
It is used exclusively or joining copper pipe in the refrigeration and airconditioning industry, as well as most general plumbing work. It's main advantage is that the filler rod wicks readily into an overlapping joint, completely filling any voids. It makes a 100% leak proof joint, and is excellent for busbars too, because there will be no invisible voids within the joint.
As you say, it alloys with the copper and makes a corrosion proof joint stronger than the original copper. The silver has very good electrical conductivity, and it also has a suitably high melting point ideal for hot running components.
It is extremely easy to use, no flux being required. Just heat up the cleaned copper parts and apply the filler rod. It runs right into the joint.
RE: Connecting to tubular copper bus
Something you must consider when choosing a repair method is not the thremal rating, but the fault rating of the bar. The mechanical stresses which exist during a major fault are staggeringly large, and will show up any weakness in a joint. Failure of a joint during a major fault will almost certainly turn a recoverable problem into something altogether more serious.
waross' suggestion that a silver brazed joint can be stronger than the parent metal is not inaccurate, but requires tight control of tolerances between components to avoid the gap being filled by weak braze alloy.
Waross: is the 'IPS' you refer to possibly 'IPB', an abbreviation for Isolated Phase Bus? IPB is typically used for very heavy current applications where it is desirable to limit external magnetic field intensity while providing great mechanical strength and virtually guaranteeing that an interphase fault can not occur. The interconnect from a large generator to its associated GSU transformer is a very typical application. IPB essentially comprises of a conductive tubular outer shield mounted co-axially with a central conductor. The shield is grounded and is electrically contiguous throughout its length.
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I don't suffer from insanity. I enjoy it...
RE: Connecting to tubular copper bus
The brazing alloy we are discussing is very user friendly. It has very good wetting action, and very good wicking action. It is silver based and very strong and a good conductor. It does require a high temperature. You need Mapp gas, Air-acetylene or Oxy-acetylene. A propane flame is not hot enough.
A query in the refrigeration forum will probably be productive.
Re; IBP/IPS. If the busbar in question is square, it is not IPS. IPS is aluminum or copper bus manufactured to the same dimensions as listed in the National Pipe Standards for Iron Pipe. It is quite common in North America.
Thanks for the information regarding IPB. Is this a general description for high strength, wide spaced, busbars or are there standards listing the conditions to be met?
respectfully.
RE: Connecting to tubular copper bus
I can definitely see why preventing interphase faults on a large resistance/reactance grounded generator would be important.
RE: Connecting to tubular copper bus
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I don't suffer from insanity. I enjoy it...
RE: Connecting to tubular copper bus
I would be very careful about soldering or using any process which would involve heat to re-insert the piece of bus that you intend to cut out. My concern would be this.
Copper tubing, angle or even wire is "drawn" or heat treated so to speak when it is manufactured. This "heat treatment" or drawing process is what gives copper or any copper alloy its physical strength. Depending on the amount of heat applied to your bus tube during a soldering or welding process, you could very well anneal, or soften the copper and remove a great deal of its strength. Depending on where in the "span" your splice or tap was placed, you may build in a point of mechanical failure which may become evident during a most inopportune time. For this reason, I would strongly consider using a mechanical connection. There is a sytem available which I have seen used on tubular aluminum bus in substations that linemen refer to as "Deutsch" fittings or connections. I believe this system is equally applicable to copper bus. A google search for Deutsch connections will give you results that you may find very interesting.
Regards
RE: Connecting to tubular copper bus