Fisher A41 Konfigurationshandbuch
www.Fisher.com
Safety manual for Fisher™A41 Valve
Purpose
This safety manual provides information necessary to design, install, verify and maintain a Safety Instrumented
Function (SIF) utilizing the Fisher A41 valve.
WARNING
This instruction manual supplement is not intended to be used as a stand-alone document. It must be used in conjunction
with the following manual: Fisher A41 High Performance Butterfly Valve Instruction Manual (D500211X012)
Failure to use this instruction manual supplement in conjunction with the above referenced manual could result in personal
injury or property damage. If you have any questions regarding these instructions or need assistance in obtaining any of
these documents, contact your Emerson sales office or Local Business Partner.
Introduction
This manual provides necessary requirements for meeting the IEC 61508 or IEC 61511 functional safety standards.
Figure 1. Fisher A41 Valve
W9269
A41 Valve
June 2017
Instruction Manual Supplement
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Instruction Manual Supplement
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A41 Valve
June 2017
2
Terms and Abbreviations
Safety: Freedom from unacceptable risk of harm.
Functional Safety: The ability of a system to carry out the actions necessary to achieve or to maintain a defined safe
state for the equipment / machinery / plant / apparatus under control of the system.
Basic Safety: The equipment must be designed and manufactured such that it protects against risk of damage to
persons by electrical shock and other hazards and against resulting fire and explosion. The protection must be
effective under all conditions of the nominal operation and under single fault condition.
Safety Assessment: The investigation to arrive at a judgment based on the facts of the safety achieved by
safetyrelated systems.
FailSafe State: State where valve actuator is deenergized and spring is extended.
Fail Safe: Failure that causes the valve to go to the defined failsafe state without a demand from the process.
Fail Dangerous: Failure that does not respond to a demand from the process (i.e. being unable to go to the defined
failsafe state).
Fail Dangerous Undetected: Failure that is dangerous and that is not being diagnosed by automatic stroke testing.
Fail Dangerous Detected: Failure that is dangerous but is detected by automatic stroke testing.
Fail Annunciation Undetected: Failure that does not cause a false trip or prevent the safety function but does cause
loss of an automatic diagnostic and is not detected by another diagnostic.
Fail Annunciation Detected: Failure that does not cause a false trip or prevent the safety function but does cause loss of
an automatic diagnostic or false diagnostic indication.
Fail No Effect: Failure of a component that is part of the safety function but that has no effect on the safety function.
Low Demand Mode: Mode, where the frequency of demands for operation made on a safetyrelated system is no
greater than twice the proof test frequency.
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 safetyrelated systems where Safety Integrity Level 4 has the highest
level of safety integrity and Safety Integrity Level 1 has the lowest.
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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 1556177771,
ISA
D Control System Safety Evaluation and Reliability, 2nd Edition, ISBN 1556176388, ISA
D Safety Instrumented Systems Verification, Practical Probabilistic Calculations, ISBN 1556179099, ISA
Reference Standards
Functional Safety
D IEC 61508: 2000 Functional safety of electrical/electronic/ programmable electronic safetyrelated systems
D ANSI/ISA 84.00.012004 (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 deenergized, the actuator and valve shall move to its failsafe position. Depending on
which configuration is specified fail–closed or failopen, 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.
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The A41 valve is intended to be part of final element subsystem as defined per IEC 61508 and the achieved SIL level of
the designed function must be verified by the designer.
Pressure, Temperature, and Environmental limits
The designer of a SIF must check that the product is rated for use within the expected environmental limits. Refer to
the A41 valve product bulletin for environmental limits.
Application limits
The materials of construction of A41 valves are specified in the product bulletin. A range of materials are available for
various applications. The serial card will indicate what the materials of construction are for a given valve. It is especially
important that the designer check for material compatibility considering onsite chemical contaminants and
environmental conditions. If the A41 valve is used outside of the application limits or with incompatible materials, the
reliability data provided becomes invalid.
Diagnostic Response Time
The A41 valve does not perform any automatic diagnostic functions by itself and therefore has no diagnostic response
times of its own. However, automatic diagnostics of the final control subsystem may be performed such as Partial
Valve Stroke Testing (PVST). This typically will exercise the valve over a small percentage of its normal travel without
adversely affecting the flow through the valve. If any failures of this PVST are automatically detected and annunciated,
the diagnostic response time will be the PVST interval time. The PVST must be performed 10 times more often than an
expected demand in order for credit to be given for this test. Typically this test could be performed monthly or weekly.
Design Verification
A detailed Failure Mode, Effects, and Diagnostics Analysis (FMEDA) report is available from Emerson. This report details
all failure rates and failure modes as well as the expected lifetime.
The achieved Safety Integrity Level (SIL) of an entire Safety Instrumented Function (SIF) design must be verified by the
designer via a calculation of PFDAVG considering architecture, proof test interval, proof test effectiveness, any
automatic diagnostics, average repair time and the specific failure rates of all products included in the SIF. Each
subsystem must be checked to assure compliance with minimum hardware fault tolerance (HFT) requirements.
When using A41 valves in a redundant configuration, a common cause factor of at least 5% should be included in the
Safety Integrity calculations. This value is dependent on the level of common cause training and maintenance in use at
the end user's facility.
The failure rate data listed the FMEDA report is only valid for the useful lifetime of A41 valves. The failure rates will
increase after this time period. Reliability calculations based on the data listed in the FMEDA report for mission times
beyond the useful lifetime may yield results that are too optimistic, i.e. the calculated Safety Integrity Level will not be
achieved.
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SIL Capability
Systematic Integrity
Figure 2. exida SIL 3 Capable
The product has met manufacturer design process requirements of IEC 61508 Safety Integrity Level 3. These are
intended to achieve sufficient integrity against systematic errors of design by the manufacturer. A Safety
Instrumented Function (SIF) designed with this product must not be used at a SIL level higher than stated without
“prior use” justification by the end user or diverse technology redundancy in the design.
Random Integrity
A41 valves are classified as a Type A device according to IEC 61508, having a hardware fault tolerance of 0. The
complete final element subsystem, with a Fisher butterfly valve as the final control element, will need to be evaluated
to determine the Safe Failure Fraction of the subsystem. If the SFF for the entire final element subsystem is between
60% and 90%, a design can meet SIL 2 @ HFT=0.
Safety Parameters
For detailed failure rate information refer to the Failure Modes, Effects and Diagnostic Analysis Report for the A41
valve.
Connection of the Fisher A41 Valve to the SIS Logic-solver
The final element subsystem (consisting of a positioner, actuator, and A41 valve) is connected to the safety rated logic
solver which is actively performing the Safety Function as well as any automatic diagnostics designed to diagnose
potentially dangerous failures within the A41 valve , actuator and any other final element components, (i.e. Partial
Valve Stroke Test).
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General Requirements
The system's response time shall be less than process safety time. The final control element subsystem needs to be
sized properly to assure that the response time is less than the required process safety time. The A41 valve will move
to its safe state in less than the required SIF's safety time (a typical value is 3 seconds) under the specified conditions.
All SIS components including the A41 valve must be operational before process startup.
The user shall verify that the A41 valve is suitable for use in safety applications.
Personnel performing maintenance and testing on the A41 valve shall be competent to do so.
Results from the proof tests shall be recorded and reviewed periodically.
The useful life of the A41 valve is discussed in the Failure Modes, Effects, and Diagnostic Analysis Report for the Fisher
A41 valve.
Installation and Commissioning
Installation
The Fisher A41 valve must be installed per standard practices outlined in the appropriate instruction manual.
The environment must be checked to verify that environmental conditions do not exceed the ratings.
The A41 valve must be accessible for physical inspection.
Physical Location and Placement
The Fisher A41 valve shall be accessible with sufficient room for the actuator, pneumatic connections, any other
components of the final control element. Provisions shall be made to allow for manual proof testing.
Pneumatic piping to the actuator shall be kept as short and straight as possible to minimize the airflow restrictions and
potential clogging. Long or kinked pneumatic tubes may also increase the valve closure time.
The A41 valve shall be mounted in a low vibration environment. If excessive vibration can be expected special
precautions shall be taken to ensure the integrity of pneumatic connectors or the vibration should be reduced using
appropriate damping mounts.
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Operation and Maintenance
Suggested Proof Test
The objective of proof testing is to detect failures within the A41 valve that is not detected by any automatic
diagnostics of the system. Of main concern are undetected failures that prevent the Safety Instrumented Function
from performing its intended function.
The frequency of proof testing, or the proof test interval, is to be determined in reliability calculations for the Safety
Instrumented Functions for which A41 valves are applied. The proof tests must be performed more frequently than or
as frequently as specified in the calculation in order to maintain the required Safety Integrity of the Safety
Instrumented Function.
The proof test shown in table 1 is recommended. The results of the proof test should be recorded and any failures that
are detected and that compromise functional safety should be reported to Emerson. The suggested proof test consists
of a full stroke of the A41 valve.
The person(s) performing the proof test of A41 valves should be trained in SIS operations, including bypass
procedures, valve maintenance and company Management of Change procedures. No special tools are required.
Table 1. Recommended Full Stroke Proof Test
Step Action
1Bypass the safety function and take appropriate action to avoid a false trip.
2Interrupt or change the signal/supply to the actuator to force the actuator and valve to perform a full stroke to the FailSafe state and
confirm that the Safe State was achieved and within the correct time.
3Restore the supply/signal to the actuator and confirm that the normal operating state was achieved.
4Inspect the A41 valve and the other final control element components for any leaks, visible damage or contamination.
5Record the test results and any failures in your company's SIF inspection database.
6Remove the bypass and restore normal operation.
Repair and replacement
Repair procedures in the appropriate valve instruction manual must be followed.
Manufacturer Notification
Any failures that are detected and that compromise functional safety should be reported to Emerson. Please contact
your Emerson sales office or Local Business Partner.
Appendix A
Sample Startup Checklist
This appendix provides a Sample Startup Checklist for Fisher A41 valves. A startup checklist will provide guidance
during the final control elements employment.
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Start-Up Checklist
The following checklist may be used as a guide to employ A41 valves in a safety critical SIF compliant to IEC61508.
# Activity Result Verified
By Date
Design
Target Safety Integrity Level and PFDAVG determined
Correct valve mode chosen (Failclosed, Failopen)
Design decision documented
Pneumatic compatibility and suitability verified
SIS logic solver requirements for valve tests defined and documented
Routing of pneumatic connections determined
SIS logic solver requirements for partial stroke tests defined and
documented
Design formally reviewed and suitability formally assessed
Implementation
Physical location appropriate
Pneumatic connections appropriate and according to applicable codes
SIS logic solver valve actuation test implemented
Maintenance instructions for proof test released
Verification and test plan released
Implementation formally reviewed and suitability formally assessed
Verification and Testing
Electrical connections verified and tested
Pneumatic connection verified and tested
SIS logic solver valve actuation test verified
Safety loop function verified
Safety loop timing measured
Bypass function tested
Verification and test results formally reviewed and suitability formally
assessed
Maintenance
Tubing blockage / partial blockage tested
Safety loop function tested
Emerson Automation Solutions
Marshalltown, Iowa 50158 USA
Sorocaba, 18087 Brazil
Cernay, 68700 France
Dubai, United Arab Emirates
Singapore 128461 Singapore
www.Fisher.com
The contents of this publication are presented for informational purposes only, and while every effort has been made to ensure their accuracy, they are not
to be construed as warranties or guarantees, express or implied, regarding the products or services described herein or their use or applicability. All sales are
governed by our terms and conditions, which are available upon request. We reserve the right to modify or improve the designs or specifications of such
products at any time without notice.
E2013, 2017 Fisher Controls International LLC. All rights reserved.
Fisher is a mark owned by one of the companies in the Emerson Automation Solutions business unit of Emerson Electric Co. Emerson Automation Solutions,
Emerson, and the Emerson logo are trademarks and service marks of Emerson Electric Co. All other marks are the property of their respective owners.
Neither Emerson, Emerson Automation Solutions, nor any of their affiliated entities assumes responsibility for the selection, use or maintenance
of any product. Responsibility for proper selection, use, and maintenance of any product remains solely with the purchaser and end user.
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