Ashcroft A Series - N4 Pressure Switch - Manual (Page 3)

A-S ERIES S WITCH S AFETY M ANUAL
I&M009-10210
REV A - 4/19/2013
1.2 Acronyms
FMEDA Failure Modes, Effects and Diagnostic Analysis
HFT Hardware Fault Tolerance
MOC Management of Change. These are specific procedures often
done when performing any work activities in compliance with
government regulatory authorities.
PFDavg Average Probability of Failure on Demand
SFF Safe Failure Fraction, the fraction of the overall failure rate of
a device that results in either a safe fault or a diagnosed
unsafe fault.
SIF Safety Instrumented Function, a set of equipment intended
to reduce the risk due to a specific hazard (a safety loop).
SIL Safety Integrity Level, discrete level (one out of a possible
four) for specifying the safety integrity requirements of the
safety functions to be allocated to the E/E/PE safety-related
systems where Safety Integrity Level 4 has the highest level
of safety integrity and Safety Integrity Level 1 has the lowest.
SIS Safety Instrumented System – Implementation of one or more
Safety Instrumented Functions. A SIS is composed of any
combination of sensor(s), logic solver(s), and final element(s).
1.3 Product Support
Product support can be obtained from:
Ashcroft Inc., 250 East Main St., Stratford Ct. 06614
www.ashcroft.com
(203) 378-8281
1.4 Related Literature
Hardware Documents:
• Ashcroft A-Series Switch Installation, Operation and Maintenance
Instructions
Guidelines/References:
• Safety Integrity Level Selection – Systematic Methods Including Layer of
Protection Analysis, ISBN 1-55617-777-1, ISA
• Control System Safety Evaluation and Reliability, 2nd Edition, ISBN 1-
55617-638-8, ISA
• Safety
Instrumented Systems Verification, Practical Probabilistic
Calculations, ISBN 1-55617-909-9, ISA