Characteristics and scope of application of flow meter for measuring steam

Abstract: The information on the characteristics and scope of application of steam measured by flow meters is provided by excellent flowmeter and flowmeter manufacturers and quotation manufacturers. Steam flow measurement is difficult, mainly because steam is a special medium. With the change of working conditions (such as temperature and pressure), superheated steam is often transformed into saturated steam, forming a vapor-liquid two-phase flow medium. For frequently changing steam in phase flow. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following is the details of the article on the characteristics and application scope of flowmeters to measure steam. Steam flow measurement is difficult, mainly because steam is a special medium. With the change of working conditions (such as temperature and pressure), superheated steam is often transformed into saturated steam, forming a vapor-liquid two-phase flow medium. For the steam whose phase flow changes frequently, there will definitely be a problem of inaccuracy in measuring the gas flow with the current flow meter. The solution to this problem is to maintain the superheat of the steam and reduce the water content of the steam as much as possible, such as strengthening the insulation measures of the steam pipeline and reducing the pressure loss of the steam, so as to improve the accuracy of the measurement. However, these methods cannot completely solve the problem of inaccurate steam flow measurement. However, the fundamental solution to the problem is to develop a flow meter that can measure two-phase flowing media. Five main factors should be considered when selecting a flow meter: the characteristics of the fluid to be measured, the production process, installation conditions, maintenance requirements, and the characteristics of the flow meter. For steam metering, the above five factors should also be considered. Here, we focus on discussing the characteristics, installation conditions, maintenance requirements and several issues that should be paid attention to when choosing a flow meter. At present, the instruments for measuring steam flow mainly include vortex flowmeters, differential pressure flowmeters, shunt rotor flowmeters, Annubar flowmeters, float flowmeters, etc. The vortex flowmeter and orifice flowmeter are mainly discussed here. and elbow flowmeters. Vortex flowmeter Vortex flowmeter is a new type of flowmeter successfully developed based on the principle of Karman vortex, which has developed rapidly since the 1970s. It is one of the alternative products of orifice flowmeter. It has the following characteristics: simple and firm structure, no moving parts; very convenient maintenance, low installation cost; wide measurement range, the range ratio can reach 1:10; small pressure loss, low operating cost; wide application range, gas, liquid Flow can be measured. However, the vortex flowmeter has certain limitations: the vortex flowmeter is a velocity type flowmeter, and the stability of the vortex separation is affected by the flow rate, so it has certain requirements for the straight pipe section, generally 10D in the front and 5D in the rear; When measuring liquid, the upper limit flow rate is limited by pressure loss and cavitation, which is generally 0.5 to 8m/s; when measuring gas, the upper limit flow rate is limited by the change of the compressibility of the medium, and the lower limit flow rate is limited by Reynolds number and sensor sensitivity. 8～25m/s; the stress vortex flowmeter is more sensitive to vibration, so when installing the flowmeter in a pipeline with large vibration, the pipeline must have certain damping measures; the stress vortex flowmeter adopts piezoelectric crystal as the detection sensor , so it is limited by temperature, generally -40 ~ +300 ℃. Orifice flowmeter has a long application history, has international standards, high theoretical accuracy, and is widely used. However, after decades of application, it is found that the orifice flowmeter has the following shortcomings: many factors in the application (design parameters and engineering Inconsistent condition parameters, insufficient upstream straight pipe section, orifice plate and pipeline are not concentric, orifice plate A surface is polluted, acute angle wear, etc.) have a great impact on its measurement accuracy, which increases the measurement error; installation is more troublesome, maintenance and The workload of dismantling and washing is large; the flow range ratio is 1:3, which has large limitations; if the installation is incorrect, steam leakage is likely to occur; the pressure loss is large and the operating cost is high. Elbow flowmeter Elbow flowmeter features: 1. Simple structure and low price. The elbow sensor is actually a 90-degree standard elbow. There is no flow sensor with a simpler structure. With the development of the machining industry and the continuous improvement of industry standardization and standardized management, the standard mechanism for elbow sensors is bent. The quality of the head is getting better and better, and the price is getting lower and lower. 2. Without any additional throttling parts or inserts, it can greatly reduce the power consumption of fluid transportation in the pipeline and save energy, especially for those measuring objects with large systems, large pipe diameters and low pressure heads. A simple example is given below to illustrate. In order to maintain the normal operation of an orifice flowmeter installed in a heating pipeline with a flow rate of thousands of tons per hour, it will consume tens of thousands of kilowatt-hours of electricity in a heating season, equivalent to tens of thousands of yuan. Here we only consider the pressure loss of the orifice flowmeter as a few kilopascals, which far exceeds this value in actual operation. Even with the pressure loss of several kilopascals, the additional operating cost caused by it cannot be ignored. The data given in Table 1 is the current flow range of the main pipeline used in the thermal pipeline network under different pressure losses,The additional power consumption of the circulating pump caused by the orifice flowmeter, power consumption, equivalent to standard coal volume, and coal purchase cost of a single orifice flowmeter in a heating season. 0.35 yuan/kWh, and the standard coal price is calculated at 200 yuan/t. For a medium-sized heating network with a flow rate of 4000m3/h, when the pressure loss of the orifice plate is 30 kPa, only one orifice flowmeter will consume an extra 96,000 kWh of electricity, and the operating cost is 31,200 yuan. For a flow rate of 10,000m3/h The large-scale heating network, the additional power consumption is 240,000 kWh, and the operating cost is 78,000 yuan. The elbow flowmeter has no additional resistance loss. If the elbow flowmeter is used instead of the orifice flowmeter for measurement, the operating cost can be greatly reduced and considerable economic benefits can be obtained; 3. The elbow flowmeter sensor is wear-resistant , not sensitive to trace wear.

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