PVC Container Design (continued)

Figure 9—This design placed the O-ring between the
end of the male threaded fitting and the inside of the cap.

Schrader Valve

A Schrader tire valve was used to apply pressure during testing. It would be desirable to have a Schrader valve installed on all safety containers. The valve could be used to pressurize the safety container and ensure that it is free of leaks or to relieve the pressure after the container is taken from one elevation to another.

Threads

The threaded polyvinyl chloride (PVC) parts appeared to be stretching when pressure was applied to the safety container. This made the parts hard to loosen even though they had been tightened only by hand. Occasionally the cap had to be opened by two hands or a strap wrench was needed. A silicone lubricant might correct this problem.