UNITED STATES
DEPARTMENT OF LABOR

The lid of a pressure cooker was captured by the invented strap and was forced against the lip of the filler neck as the belts lowered and pressed against the center of the lid. The separation between the lid and stress bar increased the sealing pressure. The nut and sleeve should have been in one piece, but material failure occurred at the radius where the sleeve was smaller than the diameter of the hot nut. This failure caused skin stress to be concentrated on the form threads of the nut, which stripped, allowing the lid to be lifted 2 to 3 in. The securing bolt and the sleeve were pushed away from the stress bar and byproducts and steam exploded from the cooker. Employee #1 sustained burns and was hospitalized. Coworkers stated that the cookers were never operated at pressures in excess of 90 psi and temperatures of 350 degrees Fahrenheit. At the time of the accident, the cookers were operating at only 50 psi and at a temperature considerably less than 350 degrees Fahrenheit. At 50 psi, there would have been 12,000 lb of pressure against the surface of the lid.