The trunnion ball valve is a form of quarter-turn valve which uses a hollow, perforated and fixed/supported ball to control flow through it.
A trunnion mounted valve means that the ball is constrained by bearings and is only allowed to rotate, the majority of the hydraulic load to be supported by the System constraints, resulting in low bearing pressure and no shaft fatigue. The line pressure drives the upstream seat against the stationary ball so that the line pressure forces the upstream seat onto the ball to cause it to seal.
The mechanical anchoring of the ball absorbs the thrust from the line pressure, preventing excess friction between the ball and seats, so even at full rated working pressure operating torque remains low. This is particularly advantageous when the ball valve is actuated because it reduces the size of the actuator and hence the overall costs of the valve actuation package.
Advantages of trunnion ball design is the lower operating torque, ease of operation, minimized seat wear (Stem/ball isolation prevents side loading and wear of downstream seats improving performance and service life), superior sealing performance at both high and low pressure (a separate spring mechanism and upstream line pressure is used as the sealing against the stationary ball for low pressure and high pressure m applications).
The trunnion is available for all sizes and for all pressure classes but they are not suitable for throttling purposes.
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Applicable standard range
SIZE : From NPS 1/2 to NPS 24 or From DN 15 to DN 600
CLASS : From ASME 150 to ASME 2500.
Design : API 6D , ASME B16.34 , ISO 17292 , API 608
Inspection & testing : API 598
Marking : MSS SP-25
Rating : ASME B16.34 With possible derating for high temperature based on seat material.
Fugitive emission : ISO 15848
Applicable end finishes
Face to face : ASME B16.10
End to end : Manufacturer standard or ASME B16.10
Socket weld : ASME B16.11
Screwed ends (NPT) : ASME B1.20.1
Flanged ends : ASME B16.5
Butt welding ends : ASME B16.25
1). Standard double block sealing performance.
2). Full die forged structure for all pressure containing parts.
3). Flanged valves are provided with flanged integral with closure member.
4). Standard primary gasket design is OR AED type, secondary emergency seal always provided for fire-safe purpose.
5). High quality stem gasket for reliable tightness and low emission performance.
6). Use of low seat-ball friction materials and surface finish for reliable sealing and long service life.
7). Best-in-Class CV values.
8). Standard split & bolted design for body-closure connection.
9). Low operation torque design.
10). Static conduction spring is used as standard between the stem and the ball (Antic-Static Device).
11). Anti blow-out proof stem design.