Power Supplies in Aluminium Refineries

Real low voltage--Something like 3VDC--Huge buss bars, 4"x 20" or more-- tons of current. The high current caused unbelievable magnetism--Metal wrist watches wouldn't work and a Copenhagen chew can lid could be tossed and it would fly up and stick to the buss bar.

I worked in a smelter on the Columbia river about 20 years ago(I wasn't an electrician then, but I am now and I am not sure how they work still)--The reason they were here was the surplus of power then, due to the hydroelectric dams.

Essentially there is an anode and cathode and the distance between them dictates the amount of power used(heat generated). The plant was a mile long and had four lines with two rows of pots each.

Occasionally the cathodes would tap out(melt through the masonry and steel)--The molten aluminum would run like water--The temperature would cause the water in the cement to explode, exposing the rebar and the liquid would conduct to ground through it--It was a sight to behold and truly hard to understand what was happening and why.

That sounds like a rather exciting event. Molten metal all over the place and I am sure that the entire line connected to that circuit would go down as a result so there would be strong motivation to isolate the failed pot and get back in business. The actual repair would also be quite involved, concrete repairs and replacing the failed pot. How do you get aluminum off of the floor?

My most exiting experiences occurred in a tire factory. A 350 pound batch of final mix (meaning it had the sulfur added) stuck in the chute and because the mixing process causes the rubber to heat up to 350 degrees F it curred in the chute and they had to shut down all of the mills to get at the chute. It took several hours and the language offended my tender ears.

Another time they were breaking down some natural rubber. One bale had gone rotten in the middle. As they started working it on the mill it heated up and stench was so bad they had to evacuate a section of the plant. If you are a parent imagine a combination of baby burp and a skunk.

I work in a smelter in Missouri. Incoming AC is stepped down in, surprise, step down transformers, then fed into huge rectifiers. Here Semi High Voltage AC power is rectified into low voltage, high amperage DC power. Some of the most modern smelters may run around 1000 volts at 500,000 amps on the circuit. (a potline where the smelting occurs is a giant series circuit) At these line loads, you have to have a huge buss bars for carrying the load, these buss bars are not insulated so heat generated in the buss can be shed and everyone wears di electric insulated boots so they do not get grounded. The magnetic fields are immense and effect tools and methods to do the work. It is actually pretty simple how it all works.

Arc welding was such a joy under those pots--Magnetism would help stick a rod and if you managed to strike an arc, the puddle would scurry off--I was always welding on the primary emissions piping that was under suction and would suck my puddle away from any butt welds. Learned then that an open mind and patience would go a long way.

How many pots in a line?

Thanx - Paul

http://www.ecy.wa.gov/programs/swfa/industrial/ind_permits/AirPermits/GAC_support_document_6-2-04.pdf

I tried to find images but ran out of time--I will look some more later.

I used to work at a company in NJ called Inductotherm which makes furnaces and power supplies to melt aluminum, iron, steel, zinc, and all other sorts of metals. You can go tho their website to see their products at http://www.inductotherm.com. They typically use a silicon vessel in which to melt the aluminum and other non-ferrous materials.

Hope this helps,

Bluezone