Corrugated stainless steel gas tubing lightning fires

Three-generation product evolution. Original yellow jacket: 0.1 coulomb capacity (typical strike is 3–5 coulombs). Black carbon-filled: ~5 coulombs. Perforated aluminum sheet: ~80 coulombs. 200–300 fires/year through the transition. Original product taken off North American market only September 2011.

Another safety-factor bulking-up — I mentioned this the very first day of class. [Tom holds up corrugated stainless steel tubing, then a sample with a hole from a lightning strike.] People never even thought about lightning strikes on these things. They gave you the Ben Franklin lightning protection system. They used to use black iron pipe. If lightning arcs to a black iron pipe, you might melt 10 or 20 or 30 thousandths deep, a little divot, but you won't penetrate, because it's a tenth of an inch thick. The lightning protection code says anything 3/16 of an inch thick is considered self-protecting. Officially this corrugated stainless tubing isn't that thick, but no one had ever seen one perforated by lightning before — well, we get two or three hundred a year that are perforated by lightning.

Japanese-developed corrugated stainless steel tubing with polyethylene coating allows one-day gas plumbing of a new home (vs. three days for black iron pipe) at five dollars/foot. But pinhole "holiday" defects in the coating, while not a problem at 110V, are catastrophic against millions-of-volts lightning bolts. About a hundred home fires per year. The industry denies and admits it; half-a-billion-dollar annual profit keeps the product on market.

In the 1980s, the gas researchers spent a lot of money developing plastic pipe. Gas pipe is supposed to be yellow, so that when people are working on things they know not to cut through the yellow pipe — it could be an explosion. [Tom holds up samples.] This is a piece of polyethylene distribution pipe, welded together, with a yellow stripe to identify it as gas pipe. About the same time in Japan, they developed something called corrugated stainless steel tubing — they put a plastic coating on it, and it's corrugated. Ten thousandths of an inch thick stainless steel. This is great. Well, sort of great. You can plumb a house with this stuff in one day. If you're building a new home, you can put all the gas piping in with this where it would take you three days with black iron pipe — which you have to thread and screw together. The labor savings are dramatic.