Thesis (M.Eng.)--Chulalongkorn University, 2000

Measuring instrument calibration is a crucial part in measurement. Apart from using instrument, the operator or working unit has to calibrate this instrument and after calibration, the instrument has to be judged whether it should be used or rejected. Researcher studied the activities in calibration support unit which has responsibility to calibrate measuring instrument in oil and LPG terminal all over country and after calibration, the calibration support unit has to determine that weather the calibrated instrument should be used or not. The instrument in scope of research are pressure transmitter, pressure switch, temperature gauge, temperature element and transmitter, temperature switch, and weight scale. From studied, researcher found that the problems are calibration support unit has problem in permissible error determination, calibrated instrument approval, uncertainty in calibration implementation, calibration activities and calibration report creation, and external calibrator control. Researcher improved the calibration support unit activities by determining standard for instrument permissible error, controlling the master instrument specification, improving calibration and calibration report creation process, and controlling external calibration activities. After improvement the rework decreased 25.2 % and the delay of calibrated instrument approval decreased 53.8%. In addition, the calibration support unit can reduce the cost of quality about 55.4% by increasing cost of conformance 39.2% and decreasing cost of non-conformance 93.1%.