ISA RP67.04 PT2 : 1994

1 Scope
2 Purpose
3 Definitions
4 Using this recommended practice
5 Preparation for determining instrument channel
      setpoints
      5.1 Diagramming instrument channel layout
      5.2 Identifying design parameters and sources of
             uncertainty
6 Calculating instrument channel uncertainties
      6.1 Uncertainty equations
      6.2 Uncertainty data
      6.3 Calculating total channel uncertainty
7 Establishment of setpoints
      7.1 Setpoint relationships
      7.2 Trip setpoint determination
      7.3 Allowable value
8 Other considerations
      8.1 Correction for setpoints with a single side of
             interest
9 Interfaces
10 Documentation
11 References
      11.1 References used in text
      11.2 Informative references
Appendix A: Glossary
Appendix B: Vessel/reference leg temperature effects on
             differential pressure transmitters used for
             level measurement
Appendix C: Effects on flow measurement accuracy
Appendix D: Insulation resistance effects
Appendix E: Plant specific as found/as left data
Appendix F: Line pressure loss/head pressure effects
Appendix G: RTD accuracy confirmation
Appendix H: Uncertainties associated with digital signal
             processing
Appendix I: Recommendations for inclusion of instrument
             uncertainties during normal operation in the
             allowable value determination
Appendix J: Discussions concerning statistical analysis
Appendix K: Propagation of uncertainty through signal
             conditioning modules
Appendix L: Example of uncertainty/setpoint calculations
             1 - Example calculation - Pressure trip
             2 - Example calculation - Flow trip
             3 - Example calculation - Level trip
             4 - Example calculation - Radiation trip

Gives guidelines for implementing ISA-S67.04 Part 1 in the areas of common assumptions and practices in instrument uncertainty calculations, methodologies, as well as sample equations for calculating total channel uncertainty, equations to estimate uncertainties for common analog and digital modules, methods for determining impact of common encountered effects on instrument uncertainty, sources and interpretation of data for uncertainty calculations, application of instrument channel uncertainty in setpoint determination, discussion of the interface between setpoint determination and plant operating and calibration procedures, and accident analysis, as well as doumentation requirements.