TANK CALIBRATION PROBLEMS

With the startup of a new facility and additions to another facility, a number of new tanks were calibrated. The calibration process could not be automated and required manual collection of the data. Several problems were encountered during the calibrations resulting in poor data and problems in estimating the calibration equations due to excessive variability both within a calibration run and between calibration runs. Because of the problems encountered, several tanks had to be recalibrated. The results of both good and poor calibration runs are presented. The poor results were due to several causes, including poor procedures, incomplete data collection, and creative implementation of the procedures. The results demonstrate how the residuals or lack of fit of the model can be used to identify problems. As a result of the problems, a checklist was developed as a guide in writing calibration procedures to ensure all the necessary data are collected and recorded accurately, the procedures are followed as written, and the appropriate personnel approve the procedures. The checklist is used as a supplement to the ANSI tank calibration standard.