Instruction Manual Supplement |
377 Trip Valve |
D103775X012 |
August 2013 |
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Safety manual for Fisher® 377 Trip Valve for Safety Instrumented System (SIS) Solutions
When the Fisher 377 trip valve is used in a Safety Instrumented System (SIS) the design process should follow a safety lifecycle as described in several international standards (IEC61508, ANSI/ISA 84.01, etc.) The following must be thoroughly reviewed and implemented as part of the safety lifecycle. This is in addition to regular installation procedures and warnings listed in the latest version of the Fisher 377 trip valve instruction manual (D200319X012).
WARNING
This instruction manual supplement is not intended to be used as a standalone document. It must be used in conjunction with the following manual:
Fisher 377 Trip Valve Instruction Manual (D200319X012).
Failure to use this instruction manual supplement in conjunction with above referenced manual could result in personal injury or property damage. If you have any questions regarding these instructions or need assistance in obtaining this document, contact your Emerson Process Management sale office.
A. Definitions, Acronyms and Abbreviations
1.FIT Failure In Time (1x109 failures per hour)
2.FMEDA Failure Modes, Effects, and Diagnostics Analysis
3.Low Demand Mode Mode, where the demand interval for operation mode on a safetyrelated system is greater than twice the proof test interval.
4.PFDAVG average Probability of Failure on Demand
5.PVST Partial Valve Stroke Test
6.SIF Safety Instrumented Function
7.SIL Safety Integrity Level
8.SIS Safety Instrumented System
B. Related Literature
1. D200319X012 Fisher 377 Trip Valve (Instruction Manual)
2. Exida FMEDA Report for Fisher 377 Trip Valve Report no. EPM 11/08109 R001
C. Product/ System Properties
1.The product is for control applications where a specific valve/ actuator action is required when supply pressure falls below a specific point. When the supply pressure rises above the trip point, the 377 trip valve automatically resets, allowing the system to return to normal operation.
2.The failsafe state for the 377 trip valve is to move the associated actuator to fail up, lock in the last position, or fail down when the supply pressure falls below the trip point.
www.Fisher.com
377 Trip Valve |
Instruction Manual Supplement |
August 2013 |
D103775X012 |
|
|
3.The 377 trip valve is a Type A device having a hardware fault tolerance of 0 (HFT = 0). The 377 trip valve is limited to a Low Demand Mode of the SIS applications.
4.The 377 trip valve is suitable for use in application to a maximum Safety Integrity Level of 3 (SIL3).
5.The failure rates for the 377 trip valve are listed below. Consult the exida FMEDA report no. EPM11/08109 R001, available from your Emerson Process Management sales office, for a detailed list of the assumptions used in the analysis.
Failure Category |
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Failure Rate (FIT) |
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377D & U |
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377L |
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Fail Safe Detected |
0 |
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0 |
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|
|
|
Fail Safe Undetected |
239 |
|
217 |
|
|
|
|
Fail Dangerous Detected |
0 |
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0 |
|
|
|
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Fail Dangerous Undetected |
379 |
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387 |
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|
|
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No Effect |
603 |
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618 |
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6.Safety Instrumented Function (SIF) design verification must be done for all components in the SIF including the 377 trip valve. The SIF must fulfill the requirements according to the Safety Integrity Level (SIL). Each subsystem must be checked to assure compliance with minimum hardware fault tolerance (HFT) requirements.
7.When using a 377 trip valve in a redundant configuration, a common cause factor of at least 5% should be included in safety integrity calculations.
D. Installation/ Configuration/ Commissioning
1.The 377 trip valve complies with the requirements of ATEX Group II Category 2 Gas and Dust.
2.The ambient temperature capabilities can be 40 to 82_C (40 to 180_F) and 18 to 104_C (0 to 220_F) depending on the elastomeric material selection per 377 instruction manual.
3.The supply pressure will be within 3.8 to 10.3 bar (55 to 150 psig). The supply medium must be clean, dry air that meets the requirements of ISA 7.0.01. A maximum 40 micrometer particle size in the air system is acceptable.
4.The 377 trip valve can be topmounted on a manifold, yokemounted, or bracketmounted to match the application requirements. 377 trip valves are used with all types of piston actuators.
5.A supply regulator, if used, must have a flow capacity greater than the required combined capacity of the trip valve and actuator. A regulator with insufficient capacity may allow supply pressure to droop, which can cause the trip valve to trip again and begin a tripreset cycle.
6.The safety function of the SIF must be tested after installation.
E. Operations, Maintenance and Decommissioning
1.Personnel operating the 377 trip valve and performing maintenance must be competent to do so.
2.Use lockout procedures and select the appropriate maintenance procedures as defined in instruction manual.
3.A conservative approach is taken in estimating the service interval for the 377 trip valve in Safety Instrumented System. For SIS applications, preventive maintenance must be performed on the 377 trip valve at ten year intervals from the date of shipment. If the instrument is exposed to the upper or lower extremes of the environmental limits, the interval for the preventative maintenance may need to be reduced.
4.If air leakage from the 377 trip valve is detected when at steadystate conditions, take immediate corrective action by replacing the 377 trip valve. It is to maintain the intended actuator fail mode upon loss of supply pressure. To ensure continuous improvement and accurate reliability prediction, the user must also work with their local Emerson Process Management service representative to see that all failures are reported.
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