View Full Version : Cadweld problems
10-16-2007, 11:45 AM
I am wondering if anyone out there is having issues with cadweld? We have been having numerous instances were the molten material is explodeing through the top of the molds in the last 6 months. We have used this system for the past 15 years without these problems. We preheat the molds and wire to remove any moisture. Cadweld is saying that they are not having any issues with there weld material, but it seems to me that is the most likely problem. We had one employee last week get 2nd degree burns on his face from shoting one of these welds.
10-16-2007, 11:07 PM
I ran into the same problem when working in a substation over the summer. I think it was caused from my sweat dripping into the shot while I was loading it. I worked with another apprentice that had the same thing happening to him. Nothing quite like having molten lava exploding out of the mold. We started holding down the lid with a long screwdriver, nobody was burned, and it made every weld just that much more exciting. Good times with ground grid……
I've never liked cadweld. Would much rather just use a wedding band to get the job done.
10-17-2007, 08:36 AM
We have used cadweld for years. In fact did a large station job last fall with lots of shots. As long as the molds were clean and dry had no problems. However as damm_encode said they are VERY sensitive to any moisture, even sweat dripping into the mold or mixing with the shot. We did have a problem years ago with one contractor that the shots were fountaining left and right and I watched them dry and preheat the molds. To make a long story short, found out the shot tubes were sitting outside in a material pile and sucking in moisture from the overnight temperature swings (job was in early spring). Ended up throwing out two opened boxes of shots, got new ones that were stored correctly and had no more problem. Don't know if this may be your problem but worth checking how they are stored.
10-17-2007, 03:21 PM
Is this some kind of thermite weld?
10-18-2007, 08:42 AM
Cadweld is the brand name for the dominant type of thermite weld used in the US. A couple of years ago they got bought out by ERICO, who has introduced some new single use molds and shots. The older system consists of a set of molds sized and grooved to do specific bonds. Examples: would be 2/0 to 2/0 cross, a 2/0 to 4/0 T, 4/0 to 3/4 ground rod etc. etc.. For each mold you make sure it is clean and DRY then lay you cables in and close the mold. Each mold lists the correct sized shot tube for it. The shot tube includes a metal disc set in the bottom of the mold "funnel" directly above the joint then a powder mixture of thermite and powdered copper, and in the very bottom of the tube, so it comes out on top, an extra fine ground mix that is easier to ignite.
If you do everything right you strike the spark step away and ten seconds later you have a permanently welded connection. Use the wrong shot and you just melted the wires away or only made a blob that breaks.
Final thing is the wires get HOT, you can actually see the heat pulse travel down the wire by the annealing color change in the wire. I have seen more than one man get careless and try to move a mold or wire without heavy gloves and burn his hand.
The welds are more expensive then other connectors and take some prep time but are probably the best connections possible. The companies I have worked at used this type connection exclusively for any station project with below earth connections (ground grid). Only occasionally used on the line and then just for things like tie-switches or large three phase breakers/reclosers to establish a ground plane at the base of the pole to operate the equipment. I don't know if they are used much in transmission as I haven't worked transmission.
10-18-2007, 04:35 PM
Thanks for the input fella's. We are storeing them in a conex box on the job site. This has been our practice for years. We do have a large number of new employees working foir us now. This could be a issue with just not being as careful when useing this product.
11-05-2007, 07:20 PM
Never really had any problems with Cadwelds, only real one was when you pour the charge in the mould is make sure the ignition powder is on the top, it can get mixed up if the charges are stored on their sides and bounced around in the back of a vehicle for a while. I used to set it all up and pack sand around the mould especially on old and bent bars as even if the weld leaked a bit it was generally still a servicable conection..
11-16-2007, 08:44 PM
Make sure all the condensation is out of the mold and out of everything. keep a propane torch with you pre-heat the wire, the rod and whatever else. Every component has to be at the same teperature. Throw out the shots that aren't loose, or might have water or condesation. get those toothpaste wire brushes to get rid of that crap in the weld, clean it every shot.
Made great molds 50 below in Wainwright , AK. Can do it anywhere else.
Bl Brnnr, 71, lineman stud taught me, and will never forget.
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