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| Linuo Trunnion Mount Ball Valve |
A trunnion ball valve has additional mechanical anchoring of the ball at the top and the bottom, suitable for larger and higher pressure valves (from Wikipedia). The alternative ball valve design is a "floating" ball valve, where the valve ball is not anchored to the valve body, but rather "floats" in the valve cavity and uses upstream pressure to assist in seating and sealing.
Trunnion ball valves (TMBV) are always more expensive because of their construction and additional seating mechanics. In some situations the size and pressure class dictate use of a TMBV - usually larger size valves and higher pressure classes tend to be TMBV.
TMBV’s are used in more extreme conditions. An example is emergency shutdown valves (ESDV) where the trunnion design combined with metal seats is typically specified. Other extreme duty examples of where TMBV’s are specified are high temperature processes an/or abrasive services. Also, TMBV's are a better choice where fire safe design is an issue, as the TMBV seat is always spring loaded.
Trunnion mounted ball valves tend to give more consistent performance, higher reliability and longer service. They often have a cavity relieving feature, which eliminates the concern about cavity pressure build-up. TMBV torques are lower and more consistent over a range of pressure change (floating ball valves increase in torque with higher pressures).
When "Double Block & Bleed" is required, the only choice are trunnion mounted valves because they are upstream sealing. Double block and bleed is a very important feature in pipeline maintenance. Additionally, in-process cleaning, seat testing and cavity cleaning are possible only in a TMBV.
