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Compare Trunnion Mounted Ball Valve With Lug Butterfly Valve 2011-12-12
Trunnion Mounted Ball Valve
Trunnion mounted ball valves are designed for upstream sealing. The load generated by the line fluid on ball is absorbed by the trunnion bearings and is directly transmitted to the valve body, and the upstream seat driven by medium pressure drifts towards the ball to creater reliable sealing. The seat design has a built-in automatic cavity relief mechanism.
Trunnion mounted ball valves have a bottom entry stem design, where the stem is inserted from inside the body. The higher the line pressure, the tighter the seal. An elastomer seal in the form of an o-ring is located at the lower end of the stem, which provides the first level of protection to the atmosphere. Valves are provided with vent and drain connections for venting/draining of the valve cavity. Vent and drain connections can also be used for on-line affirmation of valve sealing.
Lug type valves have threaded inserts at both sides of the valve body. This allows them to be installed into a system using two sets of bolts and NO nuts. The valve is installed between two flanges using a separate set of bolts for each flange. This setup permits either side of the piping system to be disconnected without disturbing the other side.
A lug style butterfly valve used in dead end service generally has a reduced pressure rating. For example a lug type butterfly valve mounted between two flanges has a 150 psi pressure rating. The same valve mounted with one flange, in dead end service, has a 75 psi rating.
If you want to know more about Ball Valve and Butterfly Valve,please enter the following links:Valve Maintenance Manual
