Hello From West Texas

[cseaton79]

Hello everybody. My name is Chris. I came across the site searching for an issue we are having with one of our machines. I work for an oil & gas equipment manufacturer. We currently have several machines using plasma. We have 2 beam profilers/cutters w/ Kjellberg plasma. One vessel profiler, again w/ Kjellberg, although we use the alternate oxy/acetylene setup quite often due to material thickness. We also have a few month old pipe profiler w/ 2 Hypertherm units, one for cutting, one for marking. This is the machine with the issue, see below. Lastly, we have an older Sector 10'x40' plasma table(water table type) that we are looking to replace. Mostly likely with an AKS downdraft machine, per our Engineering Manager's research.

I've come here to see if I can get opinions/advice/experience from anyone using an AKS plasma table. Possibly any recommended alternatives to AKS, although the Engineering Manager seems pretty set on using them. Once again we're looking at a 10'x40' downdraft or possibly slightly larger. It will be used for cutting plate parts for structural and pressure vessel assemblies. We also hope to use it for some plate beveling that we currently do on an oxy/acetylene table.

Also, I want to see if anyone has had a similar issue that we are having with our pipe profiler. I will likely repost in the Hypertherm forum, since that is the cutting unit used(Hypertherm Powermax 125), but here is what is happening: The plasma units(cutting and marking) are mounted to a motorized trolley, which has 2 all-metal ball transfer units on either side of the cutting head. The ball transfer units set the height of the torch by resting on the surface of the pipe. Occasionally we get a visible electrical arc from one of the ball transfer units to the pipe surface. This is usually quite a strong arc, enough to remove material from the pipe surface. The worst one actually welded the ball transfer unit load ball to it's own housing. We have contacted the manufacturer twice about this issue and they say to check the insulator rings on the cutting head, which look fine, and to check if our "grounding cables are correctly installed". They have not provided any detail regarding this. When the machine was installed the ground resistance was supposedly checked by the manufacture's own installer and was within spec according to him. We did have our in house electricians replace the ground rod clamp with a better unit for the stranded wire this machine uses, as it had a solid wire clamp originally installed and one of the ground wires was fairly loose in the clamp. This seemed to cure the arcing issue for a couple weeks, but it has returned again. We have not re-tested the ground resistance since changing the clamp, but will soon. Doing some reading here in the Hypertherm forum it was mentioned that typically the grounding rod should not be bonded back to the panel feeding the plasma unit. At least that is how I interpreted it. I will be checking this today to see how the panel is wired.

I am still communicating with the manufacturer about this and I don't necessarily expect to get specifics for this machine's wiring, but I am curious if anyone else has ever had a machine that has had an electrical arc from the machine housing/case/work surface to the work piece itself. Maybe the ball transfer units should insulated from the cutting trolley, but they are currently not, being all metal connected to metal brackets on the metal cutting trolley housing.

Glad to have found the site and look forward to learning more!

[plasmanewbie]

Your problem is over my head and I have no experience with SKS but I wanted to welcome you to site. Hopefully someone else will be of some help.