Plug valve equipped with pressure equalization means

A plug valve comprising:

• a valve body having a fluid flow passage therein;
• a ball element having an outer surface and a bore therethrough, said ball element being sealingly received within said valve body for rotation from a valve-closed position in which fluid flow between upstream and downstream portions of said flow passage is blocked to a valve-open position in which said fluid flow is permitted;
• displacement means for rotating said ball element sealingly crossing through said valve body and having a pin, the longitudinal axis of which is substantially perpendicular to said bore;
• and
• means for equalizing pressure between said upstream and downstream portions of said flow passage prior to movement of said ball element from said valve-closed to said valve-open positions, including means communicating pressure between said bore of said ball element and one of said upstream and downstream portions of said flow passage, at least one lateral channel within said ball element connecting said bore with said outer surface, at least one passageway formed within said pin, and a bypass channel formed within said valve body;
• said lateral channel, passageway and bypass channel being arranged to establish pressure communication between said bore and the other of said upstream and downstream portions of said flow passage when said pin is turned by a given angle from an extreme position to bring said lateral channel, said passageway and said bypass channel into alignment;
• and said displacement means acting on said ball element to open said valve only after said pin has turned by said angle.