Cement truck pressure vessel explosion (Pennsylvania)

Extended teaching case. Aluminum water tank, no doubler plates, regulatory gap (DOT defers to ASME, ASME excludes water tanks, Pennsylvania attorney reads regs and concludes no code applies). Iraq-veteran welder killed during 100 psi over-pressure test repair. Earlier near-miss (leg amputation) had been attributed to a fluke; company responded by building a test cage. Tom got involved through Roger, ex-ASME committee. Hundred thousand similar vehicles on the road; National Board of Pressure Vessel Inspectors says they can't be inspected at that scale.

I had a situation once on cement trucks. They have a 200-gallon tank of water, and they use air pressure from the air brakes — the truck has 55 psi air to run the brakes. In some residential parts of the country it says "air brakes not allowed," because if you've ever heard a truck with air brakes, it's pretty noisy. So you have this 55 psi air, and cement trucks always have people spilling cement, so they carry this 200-gallon tank of water with hoses they can pressurize. About the pressure of your garden hose. They take it, spray off the truck, so they don't get cement caked on it. When they really have a problem they often carry a couple gallons of muriatic acid — HCl, hydrochloric acid — but you'll see corrosion if they don't rinse with water.