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The U.S. Navy Public Works Center San Diego (PWCSD) was concerned about the accuracy of various flow meters on steam and compressed air lines serving Naval facilities in San Diego, California. The flow meters had experienced various inconsistencies that had not been resolved prior to July 1993. Pacific Northwest Laboratory, Richland, Washington, evaluated the operation of 10 out of 79 steam and compressed air flow meters at PWCSD. The evaluation was limited to analysis of historical information and review of existing operating procedures. On-site investigation of the flow meters was limited to external observations of the flow-sensing equipment and a check of the flow computer program. PNL did not remove installed sensing equipment (i.e., flow meters or temperature or pressure sensors) to evaluate existing condition or check calibration. Although many of the flow meter errors can be traced to improperly normalized readings and to meters improperly compensated for temperature and pressure, lack of regular maintenance, including proper calibration, was evidenced throughout this study. A strict calibration schedule should be established for all steam and air flow meters, including calibration of the temperature sensor, pressure sensor, and flow turbine. It is recommended that the most crucial flow meters (such as the 10 evaluated in this study) be calibrated yearly. The remaining 69 flow meters could be placed on a staggered, biyearly calibration schedule. Calibration should be done by qualified personnel only. Improper calibration is often worse than no calibration at all. An outside firm is recommended to be contracted with to perform all maintenance and calibration on flow meters at the Naval facilities. Use of an outside firm would better facilitate regular, reliable calibration while removing liability for damaged parts. |
