North Andover hot isostatic press explosion

10-inch-thick pressure vessel designed for 12-inch critical flaw size; manufacturing errors reduced critical flaw size to half an inch. Catastrophic failure ejected a 16-ton piece a quarter mile, landing in an industrial area at 2 a.m. with no injuries.

If you have something of this toughness, or something at the yield strength of the material along here, you can calculate the critical flaw size, and you'll have something on the order of one — the size of the flaw necessary to cause a brittle catastrophic fracture in good steel is going to be on the order of 1 inch. It could be three inches. I can give you an example. It was a 10-inch-thick pressure vessel, and they thought it was going to be a 12-inch critical flaw size. But because of manufacturing errors, they had a half-inch critical flaw size, and the thing, when it broke catastrophically, was up here in North Andover. It sent a 16-ton piece a quarter mile away, and it landed fortunately in an industrial site at 2 a.m. — no one was around. But some of the neighbors were distraught to think that there were 16-ton missiles that could land in their backyard.

World's largest HIP vessel (200 tons; 17-inch top, 10-inch wall) ruptured at night ~15 years before lecture. 16-ton fragment thrown a quarter mile. Tom and Travelers Insurance investigator first two into the pit by crane. Replacement unit was already 3 months from commissioning — averted a 3-year global gap in capacity for 60-inch aircraft engine rotors. **Cause discussion deferred to next lecture session.**

About 15 years ago — let me give you the preface. The world's largest hot isostatic press was located up here in North Andover, Massachusetts. The cylinder weighed 200 tons. The top was beveled on the side, coming down to save steel. The top was 17 inches thick, the main wall 10 inches thick. It let go one night. One 16-ton piece from this 200-ton vessel — the caps were about 25 tons each and they were just threaded in — one 16-ton piece was found a quarter of a mile away. You guys in the battleship business, that's no big deal — they can lob shells a lot more than a quarter mile. But this was more than they usually do in North Andover.