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Modernizing gas metering management through technological progress 1. Overview: Pingdingshan Gas Corporation is a gas supply and sales enterprise that relies primarily on coke oven gas as its source of gas. It serves 110,000 residential customers, as well as over 340 industrial and public utility customers. Its service area covers 29 square kilometers, with an annual gas supply volume of 51 million cubic meters. The distribution station is equipped with eight Feng machines operating in parallel; the gas introduced from the coking company and purified is measured using orifice metering devices at the distribution station before being pressurized and fed into the city’s gas network for use by gas consumers. 2. Proposal of the project: In urban gas supply, the most prominent issue is the trade settlement problem between the gas production plants and the gas companies. According to investigations, many domestic gas companies have significant disputes over the data provided by the suppliers’ metering devices, due to issues such as the humidity and impurity levels of the gas supplied by the gas production plants, which affect measurement accuracy. Our company has a supply-and-demand relationship with the local gas supply plant; since the company began operating in 1984, disputes over measurements have arisen frequently due to issues related to the volume of gas supplied. The reason for this is that the orifice plate measurement devices used by the gas supply plant have low precision, the gas contains high levels of humidity, and there are excessive amounts of impurities such as tar, which make accurate measurement impossible. The orifice plate metering system installed at the distribution station by our company in the early 1990s was capable of accurately measuring the purified gas. However, since this system could not handle the automatic management and printing of various parameters, it was impossible to reproduce or trace back the relevant parameters when there were doubts regarding the measurement results (see Figure 1). Disputes over measurements also often arise when conducting trade settlements based on the measurement data provided by such devices. The higher-level metrology authorities once decided to use the average of the measurement data from both parties’ devices for settling gas transactions. As the measurement differences between the two parties amount to 18–23% per month, the gas company incurs economic losses of up to 1.8 million yuan per year as a result. In order to completely resolve the measurement discrepancies between the parties involved in gas trading and to protect the company from economic losses resulting from such issues, our company brought together technical expertise to address the problems existing in the original metering systems at the distribution stations. After conducting research and evaluations, it was decided to invest 350,000 yuan in integrating modern computer and information engineering technologies with traditional orifice plate flow metering techniques for the process control of gas measurement. This allowed for the full automation of the orifice plate flow metering systems at the company’s distribution stations. The design work for this project began in November 1996, and the renovation was completed and put into operation in September 1997. The upgraded system is named the “Automatic Gas Quantification Metering System” (hereinafter referred to as the “Automatic Metering System”). 3. Introduction to the “Automatic Metering System” 3.1 System Composition The “Automatic Metering System” utilizes Advantech 586 industrial control computers in Taiwan. Its system software is composed of sampling software, calculation software, management software, and communication software; together with flow meters, temperature and pressure sensing and transmission devices, it forms a reliable and precise automatic gas flow metering system. The measurement pipeline consists of three parallel pipes. The sensing elements installed on the control device transmit the collected temperature, pressure, and differential pressure signals via transmission pipes and lines to their respective transmitters, where these signals are converted into 4–20mA current signals. These signals are then converted by the I/V conversion board of the industrial computer into standard 1–5V voltage signals. The signals are further processed by the 779 signal amplification and conditioning board for filtering and amplification, before being sent to the 774 star-shaped expansion board and then to the 711 high-speed data acquisition card. After I/O conversion, the computer performs calculations and displays the results, generating various reports which are transmitted over wired connections to the main control room for display and printing ； After receiving the signal from the transmitter, the multi-channel monitoring device displays various parameters in sequence, indicating changes in these parameters in real time. It also sends signals to the digital controller, which is used to control the automatic opening and closing of the 2nd and 3rd electric butterfly valves installed on the gas distribution pipes, thereby meeting the gas demand during peak and off-peak hours in the urban area (see Figure 2). 3.3 Main functions of the system: (1) Real-time display of parameters such as temperature, pressure, differential pressure, and instantaneous flow rate for each pipeline, along with bar charts and curves. (2) It can automatically print variation reports, daily reports, and monthly reports at scheduled times. (3) It is possible to manually print historical trend charts (graphs) for various parameters. (4) It allows for manual printing of the current parameters, as well as the parameters related to power outages and power restorations, along with the cumulative flow calculated from the average instantaneous flow during power outages, facilitating measurement management. (5) Although the orifice plate flow meters currently used in China incorporate compensation for instantaneous flow, temperature, and pressure, they do not correct certain parameters used in gas measurement such as ε, c, d, β, etc. This results in significant errors. The present measurement system corrects all these parameters, thereby overcoming the limitation of narrow measurement range associated with orifice plate flow meters. (6) All images displayed on the screen can be printed manually. Daily and monthly reports can be stored for one year, while the historical trend charts of various parameters can be kept for three months, facilitating easy retrieval. (7) The multi-channel inspection instrument can display the simultaneous values of temperature, pressure, and differential pressure at any time; the actuators of the pipelines are controlled via a digital regulator to ensure that the component ports operate within the effective measurement range. The system comes in both manual and automatic modes. (8) To prevent metering failures or loss of metering data due to power outages, the system is equipped with one or more UPS units in the power supply system to supply power to the entire system. 3.4 The advancement and innovation of the system: Metering devices used in the gas industry for calculating gas supply and demand ； At present, most systems still rely on orifice plates for measurement, secondary instruments for data transmission, conventional instruments for calculations, as well as for display and recording. Even the most advanced measuring devices use microcontrollers only for data processing. Moreover, the design standards for these measurement systems are based on the GB2624—81 standard, resulting in low accuracy levels; compensation and correction of various parameters are inadequate, and it is not possible to carry out automatic management of various parameters or to generate printed reports. Therefore, when trade disputes arise, it is difficult to revert to the original operating conditions, which further hinders the improvement of corporate management levels. This system is more creative and advanced than the original one. It uses industrial computers to perform calculations, manage, and store various parameters and variables, enabling them to be reproduced and retrieved at any time. The entire system carries out compensation calculations for the parameters involved in flow rate calculation, thereby improving the measurement accuracy of the whole system ； Due to the high degree of automation of the system itself, it can automatically control the opening and closing of the valves in the gas supply pipeline. In addition, the system features strong anti-interference measures, excellent resistance to noise interference, and a high reliability level for the measurement data it provides. It also has a remote communication function built-in, allowing all data and reports to be transmitted via wired connections to the company’s main control room, thereby facilitating efficient business management. 3. Scope of application of the 5-system: This system is mainly suitable for trade settlements between gas supply plants and gas companies, especially in cities where there are significant differences between peak and off-peak gas consumption levels. It holds certain value for widespread adoption, and is particularly effective in resolving the disputes that currently exist between gas companies and gas supply plants. Furthermore, this system is also suitable for measuring other gas and steam pipelines, especially for parties whose trade settlement data are often subject to disputes; using this system to resolve such disputes is more appropriate. Since this system incorporates both advanced computer technology and modern communication technologies, its supporting equipment is composed of some of the most advanced technical devices available in China at present. It features a high level of system accuracy and stable performance, delivers accurate data, and has broad prospects for widespread application. 4. Analysis of the operational benefits of the “Automatic Metering System” 4.1 Economic benefits Before the implementation of the “Automatic Metering System”, the average value of measurements taken by both parties was used as the basis for settling gas bills. However, the coking side’s measurements were 18–23% higher than ours on a monthly basis, and their average value was also 11% higher than ours. Assuming an annual gas supply volume of 50 million cubic meters and a purchase price of 0.35 yuan per cubic meter, our side paid an additional 1.8 million yuan in gas purchase costs each year. Since its commissioning, the system has operated normally with all its functions functioning properly. It features a high degree of automation, stable performance, and provides objective and accurate data that facilitates tracing of origins. It has received full recognition from both parties, and its measurement data is recognized as the sole basis for settlement, thereby preventing economic losses for the company due to measurement issues. 4.2 Social Benefits (1) The original device could only be used for basic measurement; it was completely unable to handle the automatic management and printing of various parameters (such as class data, daily reports, monthly reports, historical trend charts, etc.). In the event of disputes, it was difficult to review the original readings, which hindered tracing the origins of such disputes. After the “automatic measurement system” was put into use in 1997, these problems were effectively resolved, measurement discrepancies were avoided, and the relationship between supply and demand parties improved. (2) With the resolution of the measurement problem, all related issues were also resolved accordingly. It turns out that the calculation of gas costs is based on the average value measured by both parties, which results in heavy losses for the gas company. To ensure its normal operation, the company adjusts the prices of household gas sales in order to cover these losses, thereby increasing the burden on consumers. The implementation of an \"automatic metering system\" has helped reduce the company’s losses, and as a result, it has also lowered the economic burden on consumers due to higher gas prices. (3) By adopting advanced technological equipment for measuring devices, our company was able to effectively address a major challenge that commonly arises in the settlement of gas transactions, thereby taking a significant step forward in its measurement work. In December 1997, when the **Technical Supervision Bureau conducted an assessment of our company’s measurement and testing system, the \"automatic measurement system\" received high praise from the experts present. Our company successfully passed the assessment and was recognized as a \"**Qualified Measurement Unit,\" while also being awarded the title of \"**Advanced Measurement Unit.\"