Force
– Two Piece Trunnion
Mounted Ball Valve
Document Number:
Revision:
Release Date:
EDC 514
A
05/09/2022
IOM: Installation, Operation and Maintenance Manual
7/43
Cavity
Body
Ball
Seat Retainer
Line
2.4
Self
-
relieving seat
mechanism
Seal is made on the upstream side by the seat retainer whose seat spring pushes the seat against
the ball at fully closed position. In case the line fluid trapped in the body cavity evaporates and
causes excessive rise in the cavity pressure, especially when the cavity pressure exceeds the line
pressure, the seat will move slightly away from the ball surface to relieve the excessive cavity
pressure into the pipeline.
2.5
Fire safe ball design
When the seats are decomposed or deteriorated by a plant fire, the edge of the metal seat
retainer preloaded by the seat spring comes into contact with the ball to shut off the line fluid to
minimize internal leakage through the valve bore.
Before exposure to fire After exposure to fire
2.6
Drain port
The valve has the block and bleed structure that allows a valve or other types of connections to
be installed at the drain port through which the fluid in the cavity can be discharged.
2.7
Pressure Temperature Chart
The selection of sealing material is the end user’s responsibility and dependent upon the medium
passing through valve, valve working temperature, pressure, and velocity of flow. As the Pressure-
temperature rating varies according to different valve working conditions, the following Pressure-
temperature rating value is calculated assuming stable valve working condition.
Body
O-Ring
Seat
Ball
Line
Seat Retainer
Flexible Graphite
Body
Ball
Line
Metal
‐
to
‐
Metal Contact