Substation bus · rigid aluminum tube and fittings
Aluminum tube bus and fitting buyers in New York
Rigid tube bus is the most consistently mispriced item in a switchyard cleanout. Sold by weight it is scrap aluminum; measured end to end, with its fittings counted, it is bus that a fabricator can use.
- New York State
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- Reels and cut lengths
- Buyer review
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Tube bus is valued on alloy and temper, nominal size and schedule, length, straightness and the condition of the ends. Fittings such as clamps, terminal pads, expansion joints and supports are worth as much as the tube and are counted separately. A bent, dented or heavily pitted section keeps only its scrap value. Photographs of both ends, the wall thickness and the mill stamp answer most of the questions before anyone drives out.
Alloy, temper and schedule: what the tube actually is
Substation rigid bus is almost always extruded aluminum tube in 6063-T6, ordered to a nominal iron pipe size in Schedule 40 wall. The nominal size is not the outside diameter, which catches people out: 2 in IPS tube measures 2.375 in across, 3 in measures 3.500 in, and 4 in measures 4.500 in. Wall thickness follows the schedule rather than the nominal size, so a 4 in Schedule 40 tube has roughly a quarter inch of wall and a 6 in has a little more.
Temper is the part a buyer asks about first. 6063-T6 is solution heat treated and artificially aged, which is what gives it the strength to span between insulators and resist fault current. 6101-T6 is a higher-conductivity alloy used where ampacity matters more than stiffness. Tube that has been field welded, torch bent or through a fire is no longer T6 in the affected zone: the heat treatment is lost and the strength there falls toward the annealed condition, even though the stamp on the far end still reads T6.
Ampacity and support spacing are two different questions
Ampacity is set by the outside surface area, the finish, the ambient temperature, the permitted temperature rise and whether the sun and wind are counted. A 4 in Schedule 40 tube in still air at a conventional design rise carries on the order of two thousand amps; a 6 in carries roughly half again more; a 2 in is down around a thousand. Published tables differ because the assumptions differ, so the number on the drawing is only valid with the assumptions printed next to it.
Support spacing is a mechanical question and has nothing to do with ampacity. The span between insulators is limited by the cantilever strength of the post insulator, the bending stress in the tube under short-circuit current, and the deflection the designer will accept. Fault force rises with the square of the current and falls with phase spacing, so a yard built for 40 kA may have spans that a 63 kA fault would not tolerate. Typical outdoor spans run from about 8 ft to 20 ft depending on tube size and fault duty.
Welded or clamped, and why it changes what can be sold
A welded bus is made to fit one layout. The tube is cut, bevelled, tacked and welded with a 5356 filler, usually by a qualified welder working to a procedure, and the resulting spool only fits the bay it was built for. Welds also remove the temper locally and are where cracks start if the spool has been lifted by the tube instead of by a sling at the joints. A welded spool is worth more as a complete assembly to somebody rebuilding the same bay, and as scrap otherwise.
Clamped bus is modular, which is why the fittings carry so much of the value. Two-bolt and four-bolt aluminum pad connectors, bus supports, sliding supports, expansion joints, tee and elbow fittings and terminal pads are all reusable if they come off without being cut. The mistake made in almost every cleanout is unbolting nothing and cutting the tube either side of each clamp, which converts a set of fittings into scrap and a set of long tubes into short ones.
Length, straightness and the photographs that settle it
Length decides whether a piece can be re-used, because a bus run is a continuous span and a splice is a joint somebody has to design. Mill stock arrives in 20 ft and 24 ft lengths, and anything close to a full length with clean square ends is directly usable. Straightness is the second filter: a bowed tube changes phase spacing and cannot be pulled straight without inducing stress, and a tube that has been used as a lifting beam or a ramp is no longer bus.
Four photographs answer most of what a buyer needs. One overall shot with a tape along the piece, one of each end showing the cut and the wall, one close-up of the mill stamp or printed legend, and one of any bend showing the outside of the radius, where stretch cracks and orange-peel show first. White powdery corrosion on the surface is normal outdoors; pitting deep enough to catch a fingernail is a wall-thickness question and wants a caliper reading.
- Ends: square saw cut, weld bevel, or crushed in a vice
- Wall thickness measured at the end, not guessed from the nominal size
- Stamps: alloy and temper, heat lot, mill mark, standard
- Pad faces: flat, gouged, or built up with weld
- Bends: outside radius checked for cracks; inside radius for wrinkling
Specification
What a buyer needs to know about this cable
Every row below changes what a lot is worth. If the reel tag is gone, the jacket print and a cut end usually answer most of it.
Missing detail is not a problem — say what is missing and the review works from photographs.
| Alloy and temper | 6063-T6 is standard; 6101-T6 appears where more strength is wanted; T52 and annealed material also turns up |
|---|---|
| Product standard | ASTM B317 for extruded bus conductor; ASTM B241 for seamless tube; mill certificate names the alloy |
| Sizes | IPS Schedule 40: 2 in, 2.5 in, 3 in, 4 in and 6 in nominal |
| Outside diameter | 2.375, 2.875, 3.500, 4.500 and 6.625 in for those nominals |
| Wall thickness | Approximately 0.154, 0.203, 0.216, 0.237 and 0.280 in for Schedule 40 |
| Mill lengths | 20 ft and 24 ft are the usual stock lengths; 16 ft appears on older orders |
| Joints | TIG welded with 5356 filler, or bolted clamps and pad connectors |
| Finish | Mill finish, sometimes chromate conversion coated; weathering dulls the surface but does not change the alloy |
Constructions
Tube and fittings we review
Rigid bus lots are usually a mixture of full lengths, drops and a bucket of hardware.
Full-length mill stock
Uncut 20 ft or 24 ft tube, often still bundled, from a project that over-ordered or changed layout. The best category, and the only one that can be sold as tube rather than as material.
Field-cut drops and jumpers
Short pieces cut out of a bay during a rebuild. Useful down to a few feet for small stations and jumper work; below that they are scrap with a known alloy.
Welded spools and assemblies
Tube with elbows, tees and pads welded in place. Valued as a complete assembly if the bay layout is known, and on weight if it is not.
Clamps, pads and expansion joints
The highest value per pound in the whole lot. Counted, photographed and sold by type, because a fabricator needs the right fitting more than it needs more tube.
Weathered and pitted tube
Tube that has stood outdoors for years. Surface dulling is cosmetic, deep pitting and chalky white corrosion at the ends are not. Wall thickness decides whether it stays bus.
Copper and bronze bus
Older indoor stations and equipment connections use copper bar and tube. Priced on copper content and weight, not on length, and kept strictly apart from the aluminum.
New York
Rigid bus in the New York market
Outdoor air-insulated switchyards at 69 kV, 115 kV, 138 kV, 230 kV and 345 kV are where aluminum tube bus lives, and New York has a lot of them at every one of those levels. The tube in a 138 kV yard is typically 3 in or 4 in Schedule 40 on post insulators, with 6 in appearing on the heavier 230 kV and 345 kV buses and on transformer connections where the current is highest. Smaller 69 kV yards often run 2 in or 2.5 in.
Two trends feed the supply. Urban stations are being converted to gas-insulated switchgear, which removes the outdoor bus entirely and leaves the tube and fittings looking for a buyer. And yard rebuilds for fault duty or clearance reasons replace bus that is mechanically sound but electrically undersized, which is exactly the material a smaller station can use.
What helps a New York lot move
- Alloy and temper, from the stamp or the mill certificate
- Lengths measured, not estimated, and how many pieces of each
- Count of fittings by type, photographed as a group
- Whether the tube is straight, bowed, dented or bent
- Any welding on the piece, and where
Seller questions
Questions sellers ask
How can I tell 6063 from 6101 if the stamp has gone?
A conductivity meter usually separates them, since 6101-T6 runs at a higher conductivity than 6063-T6, and a hardness check will catch tube that has been annealed by welding or by fire. Both alloys look identical otherwise. If neither test is available, the mill certificate or the original purchase order is the only reliable answer.
Does one bend ruin a length of tube?
Not necessarily, but it changes what the piece is. A shop bend made in the T4 temper and aged afterwards is sound; a bend put into T6 tube in the field thins the outside wall and leaves the material locally unaged. A bend with visible stretch cracks on the outside radius is scrap. A clean bend is worth keeping as a bent piece, not as straight tube.
Do you buy tube with the fittings still bolted on?
Yes, and it is better that way. Cutting the tube either side of a clamp destroys both the fitting and the length. Unbolt the hardware, keep it in a box by type, and leave the tube full length. Fittings are counted and valued separately from the tube.
Is white corrosion on old tube a problem?
Usually it is cosmetic. Aluminum outdoors forms a dull gray-white oxide that protects the metal underneath. What matters is pitting deep enough to reduce the wall, and the chalky build-up that collects where water sits at a joint. A caliper reading at the end settles it.
Can short pieces of tube still be used?
Yes, down to a few feet, for jumper connections, small station buses and equipment taps. Length is only critical where a continuous span is needed. Below a couple of feet the piece is worth its alloy content and not much else, which is still more than mixed aluminum scrap.
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Prefer to talk? 614-715-3047 · saleselectricalbuyers@gmail.com