Two men were killed when the valve they were closing for routine maintenance ruptured and released high temperature steam. One of the flanges had broken away from the main body of the valve.

Examination of the handwheel showed marks consistent with using a pipe wrench as a cheater bar. But the placement and angle of the marks showed that the cheater bar had been used to open the valve, not to close it. The men were closing the valve when it failed. Besides, a cheater bar alone could not have caused the failure.

Metallurgical analysis showed high heat had been applied to where the flange had broken away. Someone had used a welding torch on the bolts which caused the gray iron of the flange to become much more brittle and weak. The crack started there and spread rapidly around the valve.

The workers had not used a torch. Who had and why? The valve had originally been installed and capped for a future expansion of the steam system. Some time later, the same contractors removed the cap and added on to the system. When they used a torch to remove the cap bolt nuts, they set up a time bomb which went off years later.