Functional Specification
Section 1:
Functional Specification
The safety function for EL-O-Matic E and P Series pneumatic actuator is defined as follows:
Double-Acting Scenario:
a.
When an unsafe condition is detected in a plant by a process sensor, the
controller, via actuator control system, drives the Actuator to
close
the
shut-down valve, depressurizing (if under pressure) the Opening side of
the actuator and pressurizing the Closing side of the actuator.
b.
When an unsafe condition is detected in a plant by a process sensor, the
controller, via actuator control system drives the Actuator to
open
the
blow-down valve, depressurizing (if under pressure ) the Closing side
of the pneumatic actuator and pressurizing the Opening side of the
pneumatic actuator.
Single-Acting Scenario:
a.
When an unsafe condition is detected in a plant by a process sensor, the
controller, via actuator control system drives the Actuator to rotate with
sufficient torque to move a valve to its fail-safe state when hold-position
air pressure is released.
The EL-O-Matic E and P Series brand Actuator Selection Procedure provides functional
definition with specifics on input variables and performance.
In any case, the choice of the safety function to be implemented is responsibility of the
system integrator.
1
April 2017
SIL Safety Manual
DOC.SILM.EEP.EN Rev. 0
Section 1: Functional Specification
