PRESSURE DETECTOR FUNCTIONAL USES Pressure DetectorsPRESSURE DETECTOR FUNCTIONAL USESPressure measurement is a necessary function in the safe and efficient operationof DOE nuclear facilities.EO 1.3 STATE the three functions of pressure measuringinstrumentation.EO 1.4 DESCRIBE the three alternate methods of determiningpressure when the normal pressure sensing devices areinoperable.EO 1.5 STATE the three environmental concerns which canaffect the accuracy and reliability of pressure detectioninstrumentation.PressureDetectorFunctionsAlthough the pressures that are monitored vary slightly depending on the details of facilitydesign, 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 pressuredetectors have audible and visual alarms associated with them when specified preset limits areexceeded. Some pressure detector applications are used as inputs to protective features andcontrol functions.DetectorFailureIf a pressure instrument fails, spare detector elements may be utilized if installed. If sparedetectors 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 voltageor current values across the detector leads and comparing this reading with calibration curves.EnvironmentalConcernsPressure instruments are sensitive to variations in the atmospheric pressure surrounding thedetector. 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 thedetector to change. This will greatly reduce the accuracy of the pressure instrument and shouldbe considered when installing and maintaining these instruments.IC-02 Page 4 Rev. 0
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