1. introduction
With the increase of natural gas exploration in China and the increasingly urgent need for urban environmental protection. Urban gasification has become the development trend of major cities in China. Under the influence of the market economy, the measurement work in the transmission and distribution of urban gas directly affects the survival and development of gas management departments, and it is also an important assessment indicator for the work of these departments. Then, in the face of dozens of domestic and foreign gas flow meters of more than a dozen varieties, how to do a good job of measurement work according to various physical properties, flow states, installation requirements, environmental conditions, economical, etc. The premise and foundation are also the immortal subjects studied and discussed by gas measurement departments and professional designers of various cities. As the gas management department, we attach great importance to the measurement and charging of jurisdictional jurisdiction. According to the actual operating conditions, we have chosen to use the RTQ-ZC series smart gas waist wheel flowmeter manufactured by Jiangsu Ruite Instrument Co., Ltd. which is a volumetric flowmeter measuring instrument for civil use. Gas meter closed assessment of the meter. This series of meters not only has all the characteristics of positive displacement flowmeters, but also the perfect combination with its intelligent integrated part to make the flowmeter without the loss of measurement accuracy under the premise of obtaining a wider range ratio, greater fluctuations in residential gas consumption The dry tube measurement is particularly suitable.
2. The working principle and characteristics of the volumetric gas waist wheel flowmeter:
2.1 The working principle of volumetric flowmeter:
Volumetric flowmeter internal design has a certain volume of space, the internal flow of the flowmeter then rotates under the pressure of the inflowing fluid from the inflow port, and with the rotation of the rotor, the fluid flows from the inflow port to the discharge port. During the rotation process, a certain volume space is formed between the rotor and the flow meter housing so that the fluid fills the space with the rotation and the fluid is continuously sent to the discharge port. If the volume of the space is designed and the number of revolutions of the rotor is measured, the amount of volume given by the space can be obtained to obtain the fluid volume flowing through. In addition, based on the number of rotations of the rotor measured per unit time, the instantaneous flow rate can be obtained. This is the measurement principle of the positive displacement flowmeter.
2.2 The working principle of the waist wheel flow meter;
When the fluid under test flows through the flowmeter, the dynamic pressure of the fluid causes a differential pressure between the inlet and outlet to push the rotation of the lumbar wheel (Figure 1).
When the fluid pushes the waist wheel on the D2 shaft counterclockwise, in Fig. 1A, the drive gear connected thereto drives the waist wheel on the D1 uranium to turn clockwise and rotates 90° to become the state of Fig. 1C. The upper waist wheel is driven by the fluid. When the hour hand rotates, the drive gear drives the lower waist wheel to rotate counterclockwise. When the waist wheel rotates 360o, there are four times the effective volume of fluid in the metering chamber to discharge the flowmeter. In this way, the two lumbar wheel exchange drives rotate, and as the lumbar wheel rotates, the fluid continuously exits the flow meter via the metering chamber. The volume of fluid discharged per revolution of the waist wheel is a fixed value. That is, the discharge volume is proportional to the rotation speed of the waist wheel shaft. Through the waist wheel shaft and other transmission mechanisms, the number of rotations is decelerated and transmitted to the integral display section. It is this working principle of the waist wheel flow meter that determines the flow meter as long as the metering chamber with the clearance design, the assembly is reasonable, it will have a higher accuracy and lower start-up flow, this feature in the civilian community Gas metering is extremely important. It not only satisfies the measurement accuracy when the residents use the gas normally, but also overcomes the incompetence of other types of flow juices to the tiny gas volume when the residents use the gas at the low peak.
2.3 RTQ-ZC series gas waist flow meter intelligent integrated part working principle:
As shown in FIG. 2 , the accumulating part detects the number of revolutions of the rotor shaft through the pulse sensor. This pulse signal is amplified by the circuit, and is sent to the microprocessor for counting and processing after the filter is shaped. The computer calculates the value of the input meter factor K and the number of pulses measured. The formula is as follows:
Q=3600×f/K
Q - volumetric flow rate of fluid flow through the meter: m3/h
f - pulse frequency unit: n/s
n - number of pulses
k———meter coefficient unit: n/m3
After the flow value is obtained, it is sent to the LCD driver circuit to drive the LCD to display the instantaneous flow rate of the fluid. At the same time, the Q value is accumulated and stored in the flow meter. The accumulated gas volume measured by the flow meter can be viewed at any time through the function keys.
The integral part uses different methods of inputting different meter coefficients at the five different flow points under the powerful function of the microprocessor to correct the non-linear section of the characteristic curve of the positive displacement flowmeter so that the flow meter can obtain a wide range ratio. The curve comparison is shown in Figure 3:
It can be seen from the characteristic curve that the small flow rate of the characteristic curve of the RTQ-ZC Series Smart Gas Waist Wheel Flowmeter has been significantly improved, which is exactly what we hope to achieve in the residential gas area closed metering.
3. Application of RTQ-ZC Series Smart Gas Waist Wheel Flowmeter in Area Closed Metering:
In order to use the regional closed measurement for civil gas in order to tie in with the work of reducing the gap, it is a feasible move to draw down small accounting units. On the one hand, it can assess the work of the community toll collectors by the difference between the district's total district and sub-tables, and analyze the internal pipeline network operation status; on the other hand, it can grasp the distribution of gas volume of the entire jurisdiction through data analysis, which is beneficial to Rational deployment of gas to ensure that residents use gas.
Community closed measurement features:
1) The use of gas peaks and low peaks is relatively concentrated, and the range of gas flow in the trunk gas into the area is relatively large, requiring a wider range ratio for the total meter.
2) The gas flow at the low peak of the gas is very small, and sometimes it is only the gas consumption of several residents' stoves, which requires the overall table to have a low start-up flow.
3) The residential use is generally a diaphragm type gas meter for civil use. Its measurement accuracy under normal operating conditions is high, and it does not lose gas. It requires a high metering accuracy.
4) After the total meter is installed in the pressure regulator, the indoor installation is basically the same as that of the residential gas, and the volumetric meter and the submeter are all using the volumetric flowmeter to eliminate the different types of flowmeters due to changes in the gas composition to the meter. Difference.
5) Flow meter reconstruction work. Due to the limitations of the original process pipeline and installation space.
There is no requirement for straightforward pipe sections and flexible installation methods for the total table.
Practice has proved that the RTQ-ZC Series Smart Gas Waist Wheel Flowmeter, which is a positive displacement flowmeter, can meet the above requirements. However, special attention should be paid to the measured medium flowing through the positive displacement flowmeter must maintain a certain degree of cleanliness, that is, the flowmeter must be installed before the gas filter, otherwise it will affect the normal operation of the volumetric flowmeter and reliable accuracy guarantee .
Comprehensive investment in reform, average living standards of residential communities, living habits and geographical location of residential communities, community size, and other factors, selected 1045 commercial residential communities in Fenghe Park located in Ketrade Street and Rongrong Xili 3736 in Wangdingdi The households are converted into residential communities and are the most representative pilots in the jurisdictions of the city. The temperament of Fengheyuan Residential Area is natural gas. According to the gas conditions in the past, an RTQ-ZC-300 intelligent gas waist wheel flowmeter was selected. The maximum working flow rate was 300m3/h, and the accuracy was ±1%. The range ratio was 1:60 ( That is, 5-300m3/h), start-up flow rate 3m3/h, top-down-down installation, and gas filter in front of the watch. Rongli moved to the Xili District, where the temperament was natural gas, and an RTQ-ZC-450 Intelligent Gas Waist-wheel Flowmeter was selected based on the previously used gas conditions. The maximum operating flow rate is 450m3/h, the accuracy is ±1%, the measuring range ratio is 1:60 (that is, 7.5-450m3/h), and the opening flow rate is 4.5m3/h. The inlet and outlet flow are installed, and a gas filter is installed in front of the watch. Since its commissioning in May 2000, it has achieved initial success. Taking the report data for the month from July 20, 2000 to August 20, 2000 as an example, the total supply of gas in Fengheyuan Community is 8,520m3, and the sales volume is 7991.5m3. The difference between the sales and sales rate is 6.2%. The gas supply volume was 39830m3, the volume of gas sold was 37318.27m3, and the ratio of sales to sales of 6.31% was up by about 10% compared with the same period last year. In addition, through this method, closed-measurement is more accurate to obtain the supply-and-sales rate of each closed community, which lays a good foundation for improving the management of community operations and charges. On the one hand, it is the humanity in the work of stealing gas, leaks and charges. Gases, etc. can promptly discover and take measures to enable the gas management department to reduce economic losses, and at the same time provide a favorable monitoring means for safe gas supply; on the other hand, it also has rigid assessment indicators for the work of community toll collectors, making them Strengthen work responsibility.
In the case of a large cell size and a high peak flow of the main pipe, it is necessary to take into account both the upper limit flow rate and the low flow rate, which virtually increases the requirement for the total metering ratio of the entry area. For example, suppose that the maximum flow of a residential community into the district trunk is 600 m3/h, and the minimum flow rate is 6 m3/h. This requires that the flowmeter's turndown ratio at this location is 1:100. It is difficult for various flow meters to satisfy this parameter. At this time, we can solve this problem by using two flow meters installed in parallel. In the above situation, two RTQ-ZC-300 Intelligent Gas Waist Wheel Flowmeters are installed in parallel (Figure 4). The single table flow rate is 5-300m3/h ±1% accuracy. Operation, the upper limit of measurement is 600m3/h, that is, it does not exceed the limit of operation, but also to meet the measurement accuracy. When a gas flow meter is turned off when the gas peak is low, the lower limit of measurement for a single operation is 5m3/h, which can meet the measurement requirements of the minimum flow rate. This switching process can be done manually or automatically by electric valves and control circuits.
4. Conclusions and recommendations
4.1 From the above example, it is concluded that the working principle and configuration of the positive displacement flow meter determine that the gas waist wheel flow meter is more suitable for closed measurement in urban residents' use of gas. It works with intelligent integrated display to make this type of flow meter more complete.
4.2 Use RTQ-ZA series intelligent temperature and pressure compensation type intelligent gas waist flow meter under conditions permitting, convert the working flow rate directly to the standard (20°C, 101.325Kpa). The flow shows that the storage will be given to the gas department. Metrology work brings greater convenience. (end)
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