Oxy-acetylene torch to cut and clean scrap metal?

Originally Posted by eesakiwi

I know exactly what you are talking about yunkman. It was a couple of weeks ago when I read about it happening here in NZ.

What happened was a company was emptying a water pipeline, quite a long one & about 6 foot dia.
A worker was doing a inspection in part of the pipe while another worker was cutting it, quite a distance away.
The cutting torch ignited some flammable gases and the person doing the inspection was killed by the pressure blast.

What happened was this. When they 'dewatered' the pipeline, they did not open the top end of the pipeline to free air, the air was entering thru the outlet end.
Now this had caused a suction/vacuum in the pipe, this vacuum sucked in air from around the pipe in several places. Underground.

Unfortuanly underground is where flammable methane and such gases come from, the vacuum sucked some of these gases that were around the pipe, into the pipe and made a explosive gas mixture with the oxygen/air that entered thru the open end.

The gas cutting ignited it and sent a pressure blast up the pipe that hit the inspector and killed her.

More info here, I cannot find the actual inquiry report.

Danger under the streets: The Onehunga blast

The other thing to remember is that oxygen will react with oil/grease etc, explosively. The stream of pure oxygen from the cutting tip is enough to do it.
And tanks, even after they are washed out, will retain fuel etc in seams, a little bit of heat and it evaporates and there's now a explosive mixture.

If washing out a tank, use detergent in the water.

Many years ago in a very large scrap yard while heading to the unloading area fro my heavy melt noticed the yard foreman was about to blow out an injector line on one of the cranes using pure oxygen from the cutting torch.



I said hey Bob you mind waiting until I leave the yard before blow that injector line, when he asked me why, I told him he shouild read the warning on the oxyen guages.