April 2022
Installation, Operation and Maintenance Manual
E-90090007 Rev. 0
6
Section 4: Operation
Operation
Section 4: Operation
4.1
SR Operator
SR type operator contains spring which is located above the piston. Therefore, under spring
stroke, spring force will act on the piston to push the drive rod (1) into fully extended
position. To retract the drive rod (1), pressure is applied through the cylinder ports on the
pedestal assembly (140) to exert force on the drive rod side of the piston (11), pulling the
drive rod (1) into the operator. Upon loss of supply pressure, the operator will fully extend
the drive rod (in other words, valve stem in retraction).
4.2
FS Operator
FS type operator contains a spring that is located below the piston. Therefore, under spring
stroke, spring force will act on the piston to pull the drive rod (1) to fully retracted position.
To extend the drive rod (1), pressure is applied through ports on the end cap
(8) to exert force on the cap side of the piston (11), pushing the drive rod (1) out of the
operator. Upon loss of supply pressure, the operator will fully retract the drive rod (in other
words, valve stem in extension).