Development Of Universal Efficient External Tightness Detection Equipment On Domestic Diaphragm Gas Meter

With the rapid development of city modernization and social economy and buildup of environmental protection, city gas becomes one of the major energy sources in 21st century. Diaphragm gas meter is preferable for domestic city gas measuring on account of its veracious, low-cost and durable characteristics. Since the city gas is flammable, explosive and even poisonous, the leakage into air will causes fire, explosion even toxicosis. All diaphragm gas meter manufacturers define external tightness detection as a critical working procedure in their production. Traditional methods for external tightness detection, e.g. U manometer and bubble emission method, can not meet the pipelining inspection for mass production well because of low efficiency, high workload and thermosensitivity. It is urgent to develop a set of universal, efficient and economical external tightness detection equipment to help the company expansion.Air leakage is very common in gas transmission and measuring fields because of the sensitivity to temperature and pressure. Analysis and detection of external tiny leakage of diaphragm gas meter is the emphasis in this paper. The veracity of Pressure Loss Method relys on many factors, e.g. environmental temperature stability, value of the absolute pressure, inspection duration, etc. So tiny leakage can not be detected well and truely in short detecting period, which is the reason for its low efficiency. However, Differential Pressure Method has little influence with the thermostability, and the veracity can be improved by lessening the range and increasing the resolution of the sensor for tiny leakage detection. In this way efficiency can be improved by shorten the detection time. Single-chip microcomputer has powerful function and is economical, which is widely used in many engineering fields for automatic control. We combine the two technologies effectively to develop a set of domestic diaphragm gas meter external tightness detection equipment, and experiments verify that it adapts to the variety of modern production mode with excellent efficiency, reliability and economy. The successful development improves the current work condition and has favorable practicability for company expansion. All in all, this paper brings the following main achievements:1. We found two mathematical models as parallel board clearance leakage and eccentric circle clearance leakage to represent leakage at the locations of output shaft and housing connection respectively. With the analysis of the leakage flux expressions we indicate the key factors of the air leakage control, which is directive for the structural design and manufacturing process control.2. We found the general mathematical model and deduce the regularity that the pressure loss caused by air leakage has exponential relationship with the time. And we calculate the pressure lose limit for diaphragm gas meter external air leakage in this way with condition that leakage rate is constant, which is the basis for the development of this diaphragm gas meter external tightness detection equipment.3. We finish the hardware and work flow design, and verify its compliance with the requirement via experiments, finalize the instruction manual with inspection parameters for various models to supervise production. The equipment has the following key advantages: (a). UNIVERSALITY: clamping fixture is adjustable, adaptable to various models detection via changing parameters via the control panel and simply debugging. (b). ECONOMY: optimize traditional working process to reduce expend and avoid unnecessary waste. (c). EFFICIENCY: multi-workstation and mult-group design improves the inspecting efficiency; lessening sensor's range to get higher resolution to shorten the detecting time improves the efficiency enormously. (d). FACILITY: single-chip microcomputer automatically runs the established program and inspection results are shown on the LEDs, which improves the work load greatly.To be honest, too much attention to the hardware cost during the development impairs the friendliness of the interface and function of data analysis and processing. Personal computer and intelligent simulation softwares can help to improve better, e.g. LabVIEW can improve theinterface and MATLAB can get better data analysis and simulation.