PRESSURE DETECTOR FUNCTIONAL USES

PRESSURE DETECTOR FUNCTIONAL USES Pressure Detectors PRESSURE DETECTOR FUNCTIONAL USES Pressure measurement is a necessary function in the safe and efficient operation of DOE nuclear facilities. EO 1.3 STATE the three functions of pressure measuring instrumentation. EO 1.4 DESCRIBE the three alternate methods of determining pressure when the normal pressure sensing devices are inoperable. EO 1.5 STATE the three environmental concerns which can affect the accuracy and reliability of pressure detection instrumentation. Pressure Detector Functions Although the pressures that are monitored vary slightly depending on the details of facility design, all pressure detectors are used to provide up to three basic functions: indication, alarm, and control. Since the fluid system may operate at both saturation and subcooled conditions, accurate pressure indication must be available to maintain proper cooling. Some pressure detectors have audible and visual alarms associated with them when specified preset limits are exceeded. Some pressure detector applications are used as inputs to protective features and control functions. Detector Failure If a pressure instrument fails, spare detector elements may be utilized if installed. If spare detectors are not installed, the pressure may be read at an independent local mechanical gauge, if available, or a precision pressure gauge may be installed in the system at a convenient point. If the detector is functional, it may be possible to obtain pressure readings by measuring voltage or current values across the detector leads and comparing this reading with calibration curves. Environmental Concerns Pressure instruments are sensitive to variations in the atmospheric pressure surrounding the detector. This is especially apparent when the detector is located within an enclosed space. Variations in the pressure surrounding the detector will cause the indicated pressure from the detector to change. This will greatly reduce the accuracy of the pressure instrument and should be considered when installing and maintaining these instruments. IC-02 Page 4 Rev. 0