Record of corredica and wire uni directional / bi - directional and process of change the mode of wire of a record of corredica of uni directional for bi directional and bidirectional for uni - direcionAl

摘要

A gate valve with a port, groove, undercut or other pressure relief means in the gate to facilitate unidirectional sealing when the gate is in one of its closed positions, and bi-directional sealing when the gate is in its other closed position.