sil safety manual - Flowserve Corporation
SIL SAFETY MANUAL
NAF Torex Butterfly Valves NFENDS4142-00-A4 02/15
NAF Torex Butterfly Valves
FCD NFENDS4142-00-A4 05/15
Experience In Motion
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NAF Torex Butterfly Valves NFENDS4142-00-A4 02/15
Contents
1Introduction................................................................................................................... 3
1.1 Scope and purpose of the Safety Manual............................................................ 3
1.2 Skill level required............................................................................................... 3
1.3 Terms, abbreviations and acronyms.................................................................... 3
1.4 Product Support & Service.................................................................................. 4
1.5 Related Documents............................................................................................. 4
1.6 Reference standards............................................................................................ 4
2 Torex Butterfly Valve Description................................................................................... 4
3 Designing a SIF using the Torex Butterfly Valve............................................................. 5
3.1 Safety Function.................................................................................................... 5
3.2 Environmental limits............................................................................................ 5
3.3 Application limits................................................................................................. 5
3.4 Design Verification............................................................................................... 5
3.5 SIL Capability...................................................................................................... 5
3.5.1Systematic Integrity................................................................................... 5
3.5.2Random Integrity....................................................................................... 5
3.5.3Safety Parameters...................................................................................... 6
3.6 Connection of the Torex Butterfly Valve to the SIS Logic Solver.......................... 6
3.7 General Requirements......................................................................................... 6
4 Installation & Commissioning....................................................................................... 6
4.1Installation........................................................................................................... 6
4.2 Physical location and placement.......................................................................... 6
4.3 Pneumatic Connections....................................................................................... 6
5 Operation & Maintenance.............................................................................................. 6
5.1 Proof Test requirement........................................................................................ 6
5.2 Repair and replacement....................................................................................... 7
5.3 Useful life............................................................................................................ 7
5.4 Notification of failures......................................................................................... 7
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NAF Torex Butterfly Valves NFENDS4142-00-A4 02/15
1Introduction
1.1
Scope and purpose of the Safety Manual
This safety manual provides the information necessary to design, install, verify and maintain a Safety Instrumented Function
(SIF) utilizing the Torex Butterfly Valve. This manual provides necessary requirements to enable the integration of the
Torex Butterfly Valve when showing compliance with the IEC 61508 or IEC 61511 functional safety standards.
This Safety Manual indicates all assumptions that have been made on the usage of the Torex Butterfly Valve. If these
assumptions cannot be met by the application, the SIL capability of the Torex Butterfly Valve may be adversely affected.
1.2
Skill level required
System design, installation and commissioning, and repair and maintenance shall be carried out by suitably qualified
personnel.
1.3
Terms, abbreviations and acronyms
Basic Safety
Freedom from unacceptable risk of harm.
BPCS
Basic Process Control System - a system which responds to input signals from the process, its associated equipment, other programmable systems and/or an operator and generates output signals causing the process and its associated equipment to operate in the desired manner but which does not perform any safety instrumented functions with a claimed SIL ≥ 1.
Fail-safe State
State where solenoid valve is de-energized and spring is extended.
Fail Annunciation Detected
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 Undetected 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 Dangerous
Failure that does not respond to a demand from the process (i.e. being unable to go to the fail-safe state).
Fail Dangerous Detected
Failure that is dangerous but is detected as part of partial valve stroke testing.
Fail Dangerous Undetected
Failure that is dangerous and that is not detected as part of partial valve stroke testing.
Fail No Effect
Failure of a component that is part of the safety function but that has no effect on the safety function.
Fail Safe
Failure that causes the valve to go to the defined fail-safe state without a demand from the process.
FMEDA
Functional safety
Failure Modes, Effects and Diagnostics Analysis.
HFT
Hardware Fault Tolerance.
Low demand
Mode of operation, where the frequency of demands for operation made on a safety-
related system is no greater than twice the proof test frequency.
MOC
Management Of Change - specific procedures often done when performing any work activities in compliance with government regulatory authorities.
PFDAVG
Average Probability of Failure on Demand.
PVST
Partial Valve Stroke Test.
Part of the overall safety relating to the process and the BPCS which depends on the correct functioning of the SIS and other protection layers.
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NAF Torex Butterfly Valves NFENDS4142-00-A4 02/15
SFF
Safe Failure Fraction - fraction of the overall random failure rate of a device that results in either a safe failure or a detected dangerous failure.
SIF
Safety Instrumented Function - safety function with a specified SIL which is necessary to achieve functional safety. Typically a set of equipment intended to reduce the risk due to a specified hazard (a safety loop).
SIL
Safety Integrity Level - discrete level (one out of four) for specifying the safety integrity requirements of the safety instrumented functions to be allocated to the safety instrumented
systems. SIL 4 has the highest level of safety integrity; SIL 1 has the lowest.
SIS
Safety Instrumented System - instrumented system used to implement on or more safety
instrumented functions. An SIS is composed of any combination of sensor(s), logic
solver(s), and final element(s).
1.4
Product Support & Service
Please refer to the contact information on the back cover of this document.
1.5
Related Documents
Hardware documents:
Fk 41.42, Torex Butterfly Valve Datasheet
Fi 41.42, Torex Butterfly Valve Maintenance and installation instructions
Guidelines/References:
FMEDA report - NAF 07/07-21 R003
1.6
Reference standards
IEC 61508-2: 2010, Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems
IEC 60654-1:1993-02, second edition, Industrial-process measurement and control equipment – Operating conditions –
Part 1: Climatic condition
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Torex Butterfly Valve Description
The Torex Butterfly Valve is a High-Performance butterfly valve that is available with either metal-to-metal or soft seats.
Due to its unique design and triple offset, it closes extremely tight. It can be used both as a control valve and as a shut-off
valve. This valve can be supplied in either wafer or lugged versions. The valves are also available in other materials e.g.
Carbon steel and Titanium, other stainless steel materials, and in Fire-safe design. Contact NAF for more information.
The valve has:
• triple offset design enables the valve closure to be extremely tight.
• small offset results in low operating torque in all control positions, so that low-torque actuators can be used.
• a special disc profile (segment of a toroid) - a principle which eliminates abrasive sliding action when the disc is opening
and closing - ensures a longer service life.
• a high mean value of seating angle, so that the disc closes without tending to stick in the closed position, virtually eliminates any disk popping when opening the valve.
• PTFE lined bearings. For temperature above 250°C hard chromium stem, direct mounted in the body.
• a one-piece valve body of stainless steel.
• a metallic or soft seat ring. Soft seats of three different materials are available.
• the NAF standard for mounting the actuator, which simplifies installation and results in a compact valve/actuator unit.
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NAF Torex Butterfly Valves NFENDS4142-00-A4 02/15
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Designing a SIF Using the Torex Butterfly Valve
3.1
Safety Function
The safety function for the valve and the additional components in the subsystem is to move the valve to the safe position
(which can be either open or closed as required by the application) within the specified safety time when the system is
tripped.
3.2
Environmental limits
The designer of the SIF must check that the product is rated for use within the expected environmental limits, maximum
working pressure and temperature. Refer to the Torex Butterfly Valve datasheet for this information.
3.3
Application limits
The materials of construction of a Torex Butterfly Valve are specified in the Torex Butterfly Valve datasheet. It is especially
important that the designer of the SIF checks for material compatibility considering on-site chemical contaminants and
air/hydraulic (as appropriate) supply conditions. If the Torex Butterfly Valve is used outside the application limits or with
incompatible materials, the reliability data and predicted SIL capability becomes invalid.
3.4
Design Verification
A detailed Failure Modes, Effects and Diagnostics Analysis (FMEDA) report is available from NAF AB for this product. This
report details all failure rates and failure modes as well as expected lifetime of the product.
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 the architecture, proof test interval, proof test effectiveness, any automatic
diagnostics, average repair time and the specific failures rates of all equipment included in the SIF. Each subsystem must
be checked to assure compliance with minimum Hardware Fault Tolerance (HFT) requirements. The exida exSILentia™
tool is recommended for this purpose as it contains accurate models for the Torex Butterfly Valve and its failure rates.
When using the Torex Butterfly Valve in a redundant configuration, a common cause factor of at least 5% should be included in the safety integrity calculations.
The failure rate data listed in the FMEDA report is only valid for the useful lifetime of the Torex Butterfly Valve. The failure
rates will increase after this useful lifetime period has expired. Reliability calculations based on the data listed in the
FMEDA report for mission times beyond the lifetime may yield results that are too optimistic, i.e. the calculated SIL will
not be achieved.
3.5
SIL Capability
3.5.1 Systematic Integrity
The Torex Butterfly Valve has met manufacturer design process requirements of Safety Integrity Level (SIL) 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 higher than the statement without “prior use” justification
by the end user, or verification of diverse technology in the design.
3.5.2 Random Integrity
According to IEC 61508 the architectural constraints of an element must be determined. This can be done by following
the 1H approach according to 7.4.4.2 of IEC 61508 or the 2H approach according to 7.4.4.3 of IEC 61508.
The 1H approach involves calculating the SFF for the entire element.
The 2H approach involves assessment of the reliability data for the entire element according to 7.4.4.3.3 of IEC 61508.
The Torex Valve is classified as a device that is part of a Type A element according to IEC 61508, having a hardware fault
tolerance of 0.
The Torex Valve can be classified as a 2H device when the failure rates listed in the FMEDA report are used for the Design
Verification calculations. When 2H data is used for all of the devices in an element, then the element meets the hardware
architectural constraints up to SIL 2 at HFT=0 (or SIL 3 @ HFT=1) per Route 2H. If Route 2H is not applicable for the
entire final element, the architectural constraints will need to be evaluated per Route 1H.
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NAF Torex Butterfly Valves NFENDS4142-00-A4 02/15
When the final element assembly consists of several components additional to Torex Butterfly Valve, the SIL must be
verified for the entire assembly using the failure rates of all components. This analysis must account for architectural
constraints by comparing both SFF and HFT with IEC61508-2, Table 2 if following Route 1H.
3.5.3 Safety Parameters
For detailed failure rate information refer to the FMEDA report for the Torex Butterfly Valve.
3.6
Connection of the Torex Butterfly Valve to the SIS Logic Solver
The Torex Valve should be assembled with an actuator and logic solver where all components are safety rated. The safety
rated logic solver shall actively perform the safety function as well as automatic diagnostics (if any) designed to diagnose
potentially dangerous failures within the Torex Butterfly Valve, (i.e. partial valve stroke test).
3.7
General Requirements
The system and function response time shall be less than the process safety time. The Torex Butterfly Valve will move to
its defined safe state in less than this time with relation to the specific hazard scenario.
All SIS components including the Torex Butterfly Valve must be operational before process start-up.
The User shall verify that the Torex Butterfly Valve is suitable for use in safety applications by confirming the Torex Butterfly Valve nameplate and model number is properly marked.
Personnel performing maintenance and testing on the Torex Butterfly Valve shall first be assessed as being competent to
do so.
Results from periodic proof tests and partial valve stroke tests (if any) shall be recorded and periodically reviewed.
The Torex Butterfly Valve shall not be operated beyond the useful lifetime as listed in paragraph 5.3 without undergoing
overhaul or replacement.
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Installation & Commissioning
4.1
Installation
The Torex Butterfly Valve must be installed per the standard practices outlined in the Maintenance and Installation Instructions.
The environment must be checked to verify that environmental conditions do not exceed the ratings.
The Torex Butterfly Valve must be accessible for physical inspection.
4.2
4.3
Physical location and placement
The Torex Butterfly Valve shall be accessible with sufficient room for pneumatic connections to the actuator and shall
allow for manual proof testing to take place.
The Torex Butterfly Valve shall be mounted in a low vibration environment. If excessive vibration can be expected then
special precautions shall be taken to ensure the integrity of pneumatic connectors or the vibration should be reduced
using appropriate damping mounts.
Pneumatic Connections
Pneumatic piping to the valve actuator shall be kept as short and straight as possible to minimize airflow restrictions and
potential clogging. Long or kinked pneumatic tubes may also increase valve closure time.
Only dry instrument air filtered to 50 micron level or better shall be used.
The process air pressure shall meet the requirements set forth in the actuator installation manual.
The process air capacity shall be sufficient to move the valve within the required time.
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Operation & Maintenance
5.1
Proof Test requirement
During operation, a low demand mode SIF must be proof tested. The objective of proof testing is to detect failures within
the equipment in the SIF that are not detected by any automatic diagnostics of the system. Of main concern are undetected failures that prevent the SIF from performing its function.
Periodic proof tests shall take place at the frequency (or interval) defined by a SIL verification calculation. The proof tests
must be performed more frequently than (or as frequently as) specified in the SIL verification calculation in order to
maintain the required safety integrity of the overall SIF. Results from periodic proof tests and partial valve stroke tests (if
any) shall be recorded and periodically reviewed.
For detailed Proof Test information refer to the FMEDA report for the Torex Butterfly Valve.
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NAF Torex Butterfly Valves NFENDS4142-00-A4 02/15
5.2
Repair and replacement
Repair procedures outlined in the Maintenance and Installation Instructions must be followed.
5.3
Useful life
Based on general field failure data and a low demand mode of operation, a useful life period of approximately 10 to 15
years is expected for the Torex Butterfly Valve.
For high demand mode applications, the useful lifetime of the mechanical parts is limited by the number of cycles. The
useful lifetime of the mechanical parts is > 10,000 full scale cycles or 8 to 10 years, whichever results in the shortest
lifetime.
5.4
Notification of failures
In case of malfunction of the system or SIF, the Torex Butterfly Valve shall be put out of operation and the process shall
be kept in a safe state by other measures.
NAF AB must be informed when the Torex Butterfly Valve is required to be replaced due to failure. The occurred failure
shall be documented and reported to Flowserve NAF representative or directly to NAF AB using the contact details on the
back cover of this safety manual.
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NAF Torex Butterfly Valves NFENDS4142-00-A4 02/15
NAF AB
SE-581 87 Linköping
Sweden
Telephone:+46 13 31 61 00
Facsimile: +46 13 13 60 54
e-mail:[email protected]
Website: www.flowserve.com
www.naf.se
To find your local Flowserve representative
or for more information about Flowserve Corporation, visit
www.flowserve.com.
NFENDS4142-00-A4
Flowserve Corporation has established industry leadership in the design and manufacture of its products. When properly selected, this Flowserve product is designed to
perform its intended function safely during its useful life. However, the purchaser or user of Flowserve products should be aware that Flowserve products might be
used in numerous applications under a wide variety of industrial service conditions. Although Flowserve can (and often does) provide general guidelines, it cannot
provide specific data and warnings for all possible applications. The purchaser/user must therefore assume the ultimate responsibility for the proper sizing and
selection, installation, operation, and maintenance of Flowserve products. The purchaser/user should read and understand the Installation Operation Maintenance
(IOM) instructions included with the product, and train its employees and contractors in the safe use of Flowserve products in connection with the specific application.
While the information and specifications contained in this literature are believed to be accurate, they are supplied for informative purposes only and should not be
considered certified or as a guarantee of satisfactory results by reliance thereon. Nothing contained herein is to be construed as a warranty or guarantee, express or
implied, regarding any matter with respect to this product. Because Flowserve is continually improving and upgrading its product design, the specifications, dimensions
and information contained herein are subject to change without notice. Should any question arise concerning these provisions, the purchaser/user should contact
Flowserve Corporation at any one of its worldwide operations or offices.
© 2014 Flowserve Corporation, Irving, Texas, USA. Flowserve is a registered trademark of Flowserve Corporation.
flowserve.com
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