） With the increasing development of industrial production, the scale of municipal construction has continued to increase, the diameter of pipelines used in industry, municipal administration, energy facilities, etc. has gradually increased, and throttling equipment (such as orifice plates, venturi tubes ) is used in flow measurement
Not only the pressure loss is too large, but the structure is too large and cumbersome; and the recent emergence of ultrasonic flowmeters, the price is too expensive. In the past two or three decades, plug-in flow meters have simple structure, light weight, and easy installation and maintenance.
The advantages of small pressure loss and low price have attracted people's attention and selection. Its advantage is to estimate the flow rate based on the measurement of only one point (or several points) of the flow rate in the pipeline. The technical staff of Xudong Instrument Factory will introduce the plug-in flowmeter.
The types and advantages and disadvantages.
的种类 First, the type of plug-in flowmeter
The division of flow meters is generally based on principles such as throttling, vortex, electromagnetic, ultrasonic, etc. Most of these meters are installed on the pipeline through flanges. The plug-in flow meter is installed as a pipe
The flow meter is used to estimate the flow rate by measuring the flow velocity at a point (or points) in the pipeline. It can be said that any instrument that can measure the flow rate can become a plug-in flow meter (this article only discusses measuring
），这类流量计目前常用的有： Plug-in flowmeters ), which are currently commonly used:
1. Pitot tube is a classic and relatively accurate flow meter. It was often used for field measurement decades ago. Because of its easy clogging and small output differential pressure, it is rarely used in industrial sites, but it is still often used for calibration.
2. Pito-Venturi tube, also known as double horn tube or double venturi tube, is also based on the principle of pitot tube speed measurement, but the structure adopts acceleration and pressure reduction measures. Under the same flow rate, it can be obtained from pitot tube bigger
Differential pressure, not easy to plug, can withstand high temperatures, but the accuracy is not high.
3. Other flow meters, such as vortex street, turbine, and electromagnetic, can reflect the size of the flow velocity. It can be made into a small measuring head, and the flow rate can be estimated by measuring the flow velocity at a certain point in the pipeline.
优缺点 Advantages and disadvantages of plug-in flowmeter
1. Simple structure, light weight and low manufacturing cost.
2. Low pressure loss and low operating cost, it is an energy-saving instrument.
3. A structure can be used for a variety of calibers (limited to the point speed type), which can reduce the number of user backups.
4. Convenient for packaging, transportation, installation and maintenance.
5. It can be installed and disassembled continuously, avoiding the economic loss caused by the interruption.
6. The flow velocity distribution in the pipeline has too much influence on the measurement accuracy, and the straight pipe section is required to be as long as 30D ~ 50D.
7. The situation on the site is complex, which has a great impact on its application and is difficult to standardize.
8. Accuracy is difficult to improve, and generally can only reach ± (3 ~ 5%).
影响因素 Influencing factors of plug-in flowmeter
The application of the flowmeter has been improved year by year, especially in the measurement of large pipelines. The advantage is that there is no need to make too much explanation. However, there are two factors to pay attention to for plug-in flow meters. Take Annubar flowmeter as an example, the company related
本身经过很深的研究，下面给大家介绍下现场主要影响阿牛巴流量计的两个重要参数： The technicians have studied the Annubar flowmeter itself very deeply on the premise of referring to a large amount of data. Here are two important parameters that affect the Annubar flowmeter on site:
1. Straight pipe length plug-in flow meters should not be unfamiliar to many users. Annubar flow meter is a plug-in meter. It can only measure the flow velocity in the diameter direction of the pipe to estimate the flow rate.
nature. If high accuracy is required, and the straight pipe section cannot meet the design requirements, the velocity distribution in the pipeline cannot be concentric circles symmetrical to the axis, and measuring only a few points in the diameter direction cannot fully reflect the flow of the entire section.
Velocity distribution, therefore, there must be strict requirements on the velocity distribution. The straight pipe section should have a length of 15-25 times the inner diameter of the pipe.
The averaging tube is mostly used for large pipe diameters. It is generally difficult to ensure such a long straight pipe section on the site and it is difficult to improve the accuracy. However, as long as the flow is steady flow, the velocity distribution is stable and does not change with time.
The degree is poor, but the repeatability is still good.
2. The above calculations of the pipe inner diameter all assume that the pipe inner diameter D is accurate. In fact, this is not the case. Few users seriously and accurately measure the pipe inner diameter. According to the international standard IS07145, when the inner diameter cannot be measured, the
The perimeter and the estimated wall thickness determine the inner diameter of the pipe. Of course, it is difficult to determine the inner diameter accurately. In addition. Factors such as corrosion, fouling, and condensate on the inner wall of the pipeline must also be considered. Errors of 1 to 2 mm inside diameter are commonplace. And it affects traffic
The impact of this cannot be ignored.
Those who understand the principle of the plug-in flow meter may easily understand that the plug-in installation method is to indirectly convert the surface measurement into a point measurement and then theoretically convert the pipeline flow.
Sex is conceivable