Ultrasonic meters for gas; meters for fiscal- and allocation measurement.

摘要

As ultrasonic meters have replaced traditional measurement technologies for the past ten years, the applications have become more demanding. One of the most challenging problems for designers to overcome has been the operation of these meters near large noise sources such as control valves, regulators and -to some extend- also flow conditioners. Being at the forefront of technology both manufacturers and users have taken their part of the problems, but have overcome most of them by sharing their experiences. Now, after gaining more than ten years of operational experiences with thousands of ultrasonic meters installed under a wide range of operating conditions, the time is ripe for a standard sharing the experiences with all others working in the gas measurement industry. In contrast to other standards in this area, this (draft) standard is a truly international standard. It is based on the experience and knowledge of experts from all over the world, experts originating from more than 20 different countries. One of the critical goals was to make this standard open for improvements; something that is especially of importance for a technology where there is still a lot of ongoing research. In order to accomplish this, the standard is written by setting requirements for the performance of ultrasonic meters instead of making demands on the technology. For a user, in the end what counts is the quality of the measurement under operating conditions and the assurance that the meter will maintain its accuracy. Assuring the quality in the field can only be reached by a chain of controlled actions starting at the manufacturing - through calibration - to the installation and practical use in the field. Therefore requirements have been set, not only for the meter performance at the calibration facility alone, but also for all the other parts involved, including the calibration facilities and the care after the installation in the field. Following the standard practice, requirements have been set for: (1) The performance of the meter at the calibration lab (2) The transfer of the quality of the calibration curve to the field (3) The conditions during calibration as well as the quality of the lab (4) The assurance of the quality of the measurement result in the field (5) The operation under field conditions