Ultrasonic flowmeter uses the electronic principle to measure the flow meter. Although it has its own verification procedure, because it has the same usage management mode as the tap water industry measurement, it puts its performance requirements, measurement accuracy, verification cycle, etc. into the cold water meter. In the meantime, it has become more standardized. Since then, the use of large-caliber ultrasonic flowmeters has normative documents in the water industry.
Ultrasonic flowmeter (ultrasonic water meter) Because the measurement principle is different from electromagnetic water meter, its accuracy is different. How to choose an ultrasonic flowmeter with superior performance and precision:
The user flow range is used to determine the type, diameter, temperature, medium, etc. of the ultrasonic flowmeter, especially considering the common flow rate and the starting flow rate. The purpose is to ensure the water supply quantity, accurately measure and reduce the leakage rate. When using the water meter, the user's water meter Commonly used traffic generally cannot exceed the common flow value specified by the product.
Different flow rate to determine the diameter of the flow meter can meet the measurement range.
Different user environments.
Also consider the working pressure, the structure of the flow certificate, the form of the converter (whether bidirectional flow, current, pulse, communication interface, data storage) and the length of the connecting cable.
The performance and accuracy of the ultrasonic flowmeter are selected.
Users can learn more about the peers who are already using the ultrasonic flowmeter, to see the effect of their use, the accuracy of the measurement.
At present, industrial flow measurement generally has problems of large diameter, large flow, small diameter, small flow, high temperature liquid, and gas measurement. This is because the general flowmeter will bring manufacturing and transportation as the diameter of the measuring pipe increases. The difficulty of the above, the advantages of increased cost, increased energy loss, and inconvenient installation, ultrasonic flowmeters can be avoided. The German FLEXIM ultrasonic flowmeter measures diameters from 6mm to 6500 mm, from a few meters wide open channels, culverts to 500m wide rivers.
Selection of measurement types for special industrial and commercial users
At present, there are some special users in the supply of industrial and commercial users. On the one hand, the gas points are more dispersed, and the amount of gas used in a single combustion device is small (generally 2 to 9 m3/h); on the other hand, the total amount of gas used is Very large, there are many problems with the accurate measurement of the natural gas supply of such users. This type of industrial and commercial users have multiple fuel appliances with different gas consumption. Different gas consumption at different time periods brings certain difficulties to the accurate measurement of natural gas. Under the condition of satisfying the maximum gas consumption, it cannot be measured under the condition of small flow. The problem.
1. Case 1: A large shopping and entertainment mall
The mall has 22 gas points distributed on the second, fourth and fifth floors. In order to ensure the accuracy of natural gas measurement, the gas supply system has a master meter (turbine flow meter Q650) and 22 sets of compensation functions. As a metering table, the flow meter usually has a gas consumption of about 400m3/d and a holiday of about 800m3/d. It is found through the data collection that the total number of meters and sub-meters is about 17m3 per day; in the initial 54d. The cumulative gas consumption of the master meter and the minute meter differs by 11511.80 m3.
Second, choose from the type of flow meter
Various flow meters, such as volumetric flowmeters, speedmeters, and differential pressuremeters, have different characteristics. Different flowmeter types have different turndown ratios. The turbine flowmeter has a turndown ratio of 1:20 to 1:30, the Roots flowmeter has a turndown ratio of 1:20 to 1:160, and the film gauge has a turndown ratio of 1: 160 (The error characteristic curves of these three kinds of flow meters are shown in Figure 1), and the appropriate flow meter should be selected according to the actual situation.
By comparing the error characteristics of the above flowmeters, it can be seen that the starting flow of the membrane meter and the Roots flowmeter is small, the initial flow of the turbine meter is relatively large, and the membrane surface exhibits a positive deviation in the small flow state. The Roots flowmeter exhibits a negative deviation. At low flow rates, the gas supply company is more willing to select a membrane meter for metering.