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Title: The Benefits Of A Fully Self Diagnosing Gas Ultrasonic Meter
Author: John Lansing Koos Van Helden Volker Herrmann
Source: 2009 South East Asia Flow Measurement Conference
Year Published: 2009
Abstract: During the past several years the use of ultrasonic meters (USMs) has gained world-wide acceptance for fiscal applications. The many benefits of USMs have been documented in papers at virtually every major conference. As the cost of gas continues to increase, the significance of knowing that the ultrasonic meter is operating accurately has never been more important. The use of diagnostics to help identify metering issues has been discussed in several papers over the past few years Ref 1, 2 & 12. The traditional method of verifying whether the USM is operating accurately essentially requires using the USMs diagnostic information to help understand the meters health. This has often been referred to as Conditioned Based Maintenance, or CBM for short. Different USM meter designs require different analysis techniques, especially for the velocity profile analysis. For the field technician, it is often difficult to understand all the diagnostic features of each USM meter design. Through the years software has been developed to help determine if the meter is operating correctly or not. However, it is still very difficult to clearly define limits on some of the diagnostic parameters that translate into a quantifiable metering error. This paper will discuss two methods of providing a fully redundant self diagnosing meter. The first is a new CBM concept to assist in determining if the fiscal 4-path USM meter is operating accurately. Rather than relying entirely on the understanding and interpretation of the meters diagnostics, a meter designed with an additional built-in diagnostic path, has been developed. In this paper the meter design will be referred to as the CBM 2Plex 4+1 meter. The second is having a meter which monitors, on a real-time basis, all diagnostic parameters and then reports when one, or more, approach unacceptable values. Traditionally in the past the user would collect log files monthly and analyze them. The problem is that often the technician would overlook a problem and thus it could develop into a significant measurement error. Also, since inspections are often performed on a monthly basis, a problem can develop and it may take a month or more before the user would see this. By monitoring the diagnostics on a real-time basis, combined with the redundancy of an independent, second metering path of the CBM 2Plex 4+1 meter, all aspects of a meters health can be checked and validated without the need for monthly inspections. This not only significantly reduces operation and maintenance (O&M) expenditures, but lowers measurement uncertainty in the field.

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