Partial stroke system meets SIL 3

An FMEDA report has shown the
NETHERLOCKS partial stoke system
FAITH (Fail Action Integrity Test
Handling) to be very reliable, with 0
Fail Safe Detected, Fail Safe
Undetected and Fail Dangerous
Detected conditions recorded from
the tests. For most cases, the FAITH is
suitable for use in SIL3 applications.

The FAITH system makes it
possible to carry out a manuallyinitiated
partial stroke test on ESD
(Emergency Shut Down) valves
during normal operation, without
interrupting process flow. It limits,
with mechanical stops, the angle of
the stroke of the valve-actuator
combination to a set percentage –
ensuring the ESD valve ‘works’,
without actually shutting down the
operation. By operating mechanically
rather than relying on electronic
contacts or signals, reliability and
simplicity is maximised.

An FMEDA (Failure Modes, Effects,
and Diagnostic Analysis) assessment
has been carried out by Exida on
NETHERLOCKS’ FAITH system.