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).
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 (1x10
failures per hour)
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.
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.
Instruction Manual Supplement
377 Trip Valve