VERSCHLUSS FUR KREISRUNDE OFFNUNGEN MIT GROSSEM DURCHMESSER

摘要

A closure for a large diameter circular opening such as the end of a tubular conduit subjected to internal positive pressure comprises a coaxial cover lid that may be opened only when a pressure relieving venting valve is opened, the cover lid being connected over the opening by screw threaded means of larger diameter than the inside diameter of the opening, and the venting valve having a removable closure cap which impedes removal of the lid until the internal pressure is vented.