| http://www.w3.org/ns/prov#value | - A quick opening closure device for a pipeline, vessel, tank or other liquid or gas container comprising: a cylindrical hub; a cylindrical, ellipsoidal domed cap attached to said cylindrical hub by a hinge device; said cylindrical hub and said cylindrical domed cap being of the same diameter; an O-ring gasket between said hub and said cap, said O-ring gasket being located in a groove in said cap; a
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