How Often Do I Need to Recalibrate My Ultrasonic Meters; A Series of Life Cycle Studies

摘要

The installed base of multi-path natural gas ultrasonic meters continues to age, some of the oldest meters have been installed for over six years. As time goes on discussions within the industry increasingly focus on the issue of re-calibration. What is the long term stability of a typical meter? How sensitive is the stability to various field conditions? Can diagnostic parameters be monitored to help identify the need for re-calibration? To support such questions this paper presents life cycle studies of various ultrasonic meters. These studies are based on long term performance data from first calibration through operation and re-calibration. Additional value is realized when the data are obtained from both field and laboratory. The first several case studies provide a Southeast Asian perspective. They concern meters that have been initially calibrated, installed in the field and then recalibrated. The analyses integrate field and laboratory data. The cases cover the effects of low pressure operation, temperature variation, cleaning and electronics replacement. Additional case studies involve several different sized meters in use as check standards in a calibration facility. The calibration histories of these meters include tens of thousands of data points. In general the meters are operating under ideal conditions; the analyses of the data indicate the stability under ideal conditions. The check standard history includes some data based on non-ideal conditions. These conditions include variable inlet profiles, variable pressure, and very low velocity. Additional value is realized when these data are included in the analyses.