Fisher A41 - Related Literature; Reference Standards; Product Description

Instruction Manual Supplement
D103546X012
A41 Valve
June 2017
3
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).
Related Literature
Hardware Documents:
Fisher A41 Valve Instruction Manual
Instruction Manual:
A41: D500211X012
Guidelines/References:
D Safety Integrity Level Selection – Systematic Methods Including Layer of Protection Analysis, ISBN 1556177771,
ISA
D Control System Safety Evaluation and Reliability, 2nd Edition, ISBN 1556176388, ISA
D Safety Instrumented Systems Verification, Practical Probabilistic Calculations, ISBN 1556179099, ISA
Reference Standards
Functional Safety
D IEC 61508: 2000 Functional safety of electrical/electronic/ programmable electronic safetyrelated systems
D ANSI/ISA 84.00.012004 (IEC 61511 Mod.) Functional Safety – Safety Instrumented Systems for the Process Industry
Sector
Product Description
The Fisher A41 valve features an eccentrically mounted disc with a soft or stainless steel seal ring. Soft seals provide
excellent sealing capabilities in both flow directions. The metal seal ring provides excellent shutoff against pressure
applied in the recommended flow direction for both liquid and gas applications. The NOVEX and Phoenix III metal seals
are available for demanding applications requiring excellent shutoff capabilities. The double D shaft combines with a
variety of power and manual actuators to form a reliable, high-performance valve suitable for many power applications
requiring tight shutoff. It is typically used with other interface components (valve actuator and positioner or solenoid
valve) to provide a final element subsystem for a Safety Instrumented Function (SIF).
Designing a SIF Using Fisher A41 Valves
Safety Function
When the valve's actuator is deenergized, the actuator and valve shall move to its failsafe position. Depending on
which configuration is specified fail–closed or failopen, the actuator will rotate the valve disk to close off the flow path
through the valve body or open the flow path through the valve body.