scope:

This recommended practice provides guidance for the implementation of ISA-S67.04.01-2000 (equivalent to ANSI/ISA-S67.04, Part I, 1994) in the following areas:

a) Methodologies, including sample equations to calculate total channel uncertainty

b) Common assumptions and practices in instrument uncertainty calculations

c) Equations for estimating uncertainties for commonly used analog and digital modules

d) Methods to determine the impact of commonly encountered effects on instrument uncertainty

e) Application of instrument channel uncertainty in setpoint determination

f) Sources and interpretation of data for uncertainty calculations

g) Discussion of the interface between setpoint determination and plant operating procedures, calibration procedures, and accident analysis

h) Documentation requirements

Purpose

The purpose of this recommended practice is to present guidelines and examples of methods for the implementation of ISA-S67.04.01-2000 in order to facilitate the performance of instrument uncertainty calculations and setpoint determination for safety-related instrument setpoints in nuclear power plants.