Most customers have now started to use ultrasonic meters for natural gas custody transfer metering. As a stand-alone meter, it can give numerous diagnostics information on the performance of the meter, but not enough to determine a benchmark on its performance to a certain reference. This is where external diagnostic would be required to enhance customer's confidence in the overall metering system performance. In this paper, we will focus on these various techniques, and how they are being used.
Before we touched on the field verification using SOS on flow computer, we will highlight some of the recent developments in the improving the performance and diagnostics of ultrasonic metering system. They are:
• Enhanced/Improved Wet Flow Calibrations
• Improved Diagnostic Software
• Incorporate Speed of Sound (SOS) calculation in flow computers for on-line verification
• Remote Diagnostic
We will end with an example and an update on the latest development in AGA-9 [I] Working Group.

Multi-path Ultrasonic Flowmeter (MUF) is receiving much attention because it provides a lot of advantages over other techniques of flow rate measurement. It has no moving parts inside flow passage leading to no pressure loss, and it gives a good accuracy and repeatability for flow rate measurement. The present study describes theoretical, experimental, and computational works to investigate the velocity integration method of MUF, which has five acoustic paths. A weighting factor concept, which is given by a function of the chord locations of acoustic paths, is employed to obtain the flowrate. In theoretical analysis, the power law velocity profiles are assumed for fully developed kerosene and water flow of the flow rate between 40 m³/h and 300 m³/h. Computational analysis using 3-dimensional Navier-Stokes equations is performed to predict the velocity profiles in the flow passage and the results are validated with experimental data. The obtained result shows that for flowrate measurement of 5 paths ultrasonic oil flow meter, the present weighting factor concept gives good accuracy less than ± 0.14 %.

Application of ultrasonic flowmeters for fiscal metering has increased in the oil industry. High accuracy, a long-term reliability and no-moving parts are characteristics that define the ultrasonic meter as an attractive option to be considered in custody transfer and fiscal metering operations. The paper presents an analysis carried out on a metering system composed of two similar five beans ultrasonic meters, 24 inches size, maximum capacity of 8 000 m³/h, installed in series in an oil offloading system on board a FPSO. One of the meters operates as the fiscal meter, and the other as a master meter to run regular calibrations of the fiscal meter. The analysis was developed to evaluate the performance of the fiscal meter during the oil offloadings to tankers and to assess the meter factor drift along a series of provings against the master meter. Results showed that the ultrasonic meter presented high repeatability and good stability of the meter factor, allowing flow measurement uncertainties that fully complied with the requirements for fiscal metering based on the OIML R117 accuracy class 0.3.

To calibrate micro flow sensors and as well flow controllers for liquid handling in bio-medicine diagnoses, a traceable system that considers a weighing approach, virtual piston approach, and a velocity-based approach was proposed at CMS. Firstly, a pneumatic push-and-pull pressure control mechanism for steadily driving fluid was verified and estimated of its measurement uncertainty. The capability of the system depends on weighting of the collection bag, the stability of pressure difference, the time interval and the variation of ambient temperature. Due to the low flowrate, weight of collected fluid was measured within a time interval that was pre-determined to keep required accuracy and uncertainty from potential environmental influences. Tests of liquid flow in channels of different dimensions showed that the present system can measure flowrate from 0.1 mL/min to approximately 10 mL/min with an uncertainty < 1.8 %. Deviation of repeated measurements indicated feasibility of the estimation; and comparison with commercial micro liquid sensors indicated practicability of the weighing method.

A calibration bench was developed and constructed to calibrate domestic water meters, especially for the needs of the water distribution companies. The bench could calibrate up to 6 water meters at the same time in the present version. It was designed to work with water and in normal operation with two reservoirs and a battery of working standards, electromagnetic flowmeters of special grade. The mag meters assure an uncertainty of less than 0,3 %, because they are calibrated on the spot: there is an electronic scale in the circuit of the bench that can be used at any time to calibrate the secondary standards or the metes under test. With this, this bench is almost a "primary" laboratory. A centrifugal pump feeds the constant head level tank and the water in excess turns back to the lower reservoir, assuring that there is no influence of the level of water, or of its oscillation due to the pump movement, in the calibration of the meter. For the highest flow rates, the pump is used in direct connection to the meters under test, with no passage through the upper reservoir. The range of operation is from 2 L/h up to 7500 L/h. The control is totally automated using a PLC and data is stored in an electronic data sheet.