Corrugated Stainless Steel Tubing

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.

In the 1990s, the gas association was looking for some new way to promote the use of gas, and they wanted a cheaper way than cathodic protection. They came up with this. This is what's called corrugated stainless steel tubing. [Tom produces a length of CSST.] It's got a yellow polyethylene jacket, yellow because it means fuel gas, and it's got ten mil corrugated stainless steel. You can bend this — it's flexible. A plumber can put this in a house nowadays in one day, as opposed to taking black iron pipe which he has to cut to length and thread — that takes three days to install.

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.

The lecture's summative case. Japanese earthquake-driven product, brought to U.S. market via ANSI LC1 (written by Foster Wheeler consultant, approved in Canada first to bypass U.S. bureaucracy), introduced 1997. By 1998, NFPA data shows spike in lightning-induced gas fires. Industry knew by 2001, blamed plumbers' grounding through 2007, eventually developed conductive-jacket version (Gastite) and an inferior six-coulomb competitor. The 2003 Arkansas class action settled; one Texas county banned the product. Tom advised the Massachusetts State Plumbing Board in 2003, leading to the most restrictive state installation requirements in the country.

[Tom holds up a length of corrugated stainless steel tubing.] What I wanted to talk about is corrugated stainless steel tubing. Anyone ever heard of corrugated stainless steel tubing? This is gas tubing. It's fuel gas, originally in yellow, because that's the international code for fuel gas tubing. A plumber goes in a building, or a firefighter goes into a building, and they see yellow tubing — they know it probably carries a flammable gas, sort of a warning.

Is designed to code good enough? The simple answer is, not always. Or as Matt said, sometimes — that's basically the same answer. I don't think I have time to give you the example right now of corrugated stainless steel tubing. Maybe we'll talk about that next time.