With the rapid development of China’s economic situation and increasingly fierce competition in the international market, all walks of life are facing severe challenges. How to improve the management level of an enterprise, how to reduce production costs and increase production efficiency become the key to the success or failure of an enterprise. Among them, energy consumption is an important indicator of the production costs of all enterprises, so the correct and rational use of energy has become an important part of business management. Among them, steam is one of the important energy sources for various production companies. Some of them directly participate in chemical reactions, but most of them use their heat energy. Therefore, companies generally think of “steam†before talking about energy saving and consumption reduction. The ordinate and abscissa in the figure are the (water) steam pressure and temperature values, respectively. The curve in the figure is called saturation curve. The point on the curve is the saturated steam parameter value, the upper part of the saturation curve is superheated steam, and the following part is liquid water. In addition, during the long-distance transportation of dry steam, partial condensation may occur due to heat loss, resulting in a decrease in the steam quality and becoming wet steam. When the temperature of steam is under the saturation curve, we cannot call it steam but water. Saturated steam is actually the critical value of the transformation of water molecules from liquid state to gaseous state. Saturated steam changes some of the gaseous water molecules to liquid state due to changes in temperature or pressure. That is, when steam carries part of the water, it is called “wet steamâ€. Completely gaseous water molecules are called "dry steam." (1) Wet steam is a two-phase fluid in terms of attributes, but in the case of low humidity, it can be treated as a single-phase fluid and measured with a general flow meter. Galvanized Steel Plate,Galvanized Steel Sheet Plate,Astm G350 Galvanized Steel Plate,Hot Galvanized Steel Sheet Plate Shandong Yuzhong Steel Co., Ltd. , https://www.cnyzsteel.com
1. Classification and Selection of Instrument for Measuring Steam Flow At present, the instruments for measuring steam flow are mainly divided into two categories: vortex street and differential pressure (mainly orifice plate). The steam flow measurement used the standard orifice flowmeter before the 1980s. However, from the standpoint of the development of flowmeters, orifice flowmeters have a long history and a wide range of applications, and people have the most extensive research on it. Experimental data The most complete, but the use of standard orifice flowmeter to measure the steam flow, it still has some deficiencies: First, the pressure loss is greater; Second, the pressure tube, the three groups of valves and connectors are prone to leakage; Third, The range of measurement is small, usually 3:1. It is easy for the fluctuation of the flow rate to cause the measurement value to be low. The vortex flowmeter has a simple structure, and the transmitter is directly installed on the pipeline to overcome the pipeline leakage phenomenon. In addition, the vortex flowmeter has a low pressure loss, a wide range of measurement, and a measurement range ratio of saturated vapor to 30:1. Therefore, with the maturity of vortex flowmeter measurement technology, the application rate of vortex flowmeters in steam flow detection has been increasing year by year.
Steam is a special medium with saturation and overheating. With the change of working conditions (such as temperature and pressure), superheated steam will often turn into saturated steam (as shown below) 
From the above figure, it can be seen that the temperature and pressure values ​​of the saturated steam are in one-to-one correspondence, that is, when the temperature or pressure of the saturated steam is determined by one of the values, the other value can also be determined. For example: The absolute pressure corresponding to saturated steam at 150°C is 0.476 MPa. The saturated steam with absolute pressure of 0.6 Mpa corresponds to a temperature of 158.94°C. The temperature and pressure of the superheated steam do not correspond to one another. In the figure, the temperature is above the saturation curve. For example: When the steam pressure at 150°C is greater than 0.476Mpa, it is called superheated steam, but the degree of superheat is different. When the pressure equals 0.476 MPa, it is called saturated steam.
2. Temperature and pressure compensation in steam flow metering At present, the unit of China's steam metering record and settlement value is basically the mass flow, ie tons or kilograms. The steam flow meter measurements are all volume flow, which is cubic meters. This requires the steam temperature and pressure to be collected in real time, and the density calculated in the integrator or computer to compensate. The temperature and pressure values ​​of the saturated steam are in one-to-one correspondence, so the density of the saturated steam can be compensated by measuring the pressure alone or measuring the temperature. However, the temperature and pressure of superheated steam do not correspond to one another. The density compensation of superheated steam must simultaneously measure its pressure and temperature. To measure superheated steam, for example, when using a vortex flowmeter, pressure transmitters and temperature sensors should be installed to collect pressure and temperature for compensation calculations (see the following figure). 
(2) Vapors with heavy water will cause a “leak pulse†phenomenon in vortex flowmeters. In more serious cases, vortex flowmeters will have no pulse output at all.
(3) For the normal measurement of vortex flowmeters affected by severe vaporization of water, the common method of treatment is to adequately drain water at the appropriate location upstream of the vortex flowmeter. Reasonably arrange the steam trap to keep the superheat of the steam and make the wet steam dryness as high as possible to ensure normal measurement of the vortex flowmeter.
3. Advantages of vortex flowmeters in steam metering (1) The structure is simple and solid, with no moving parts, high reliability, and long-term operation is very reliable.
(2) It is easy to install and maintain. Unlike differential pressure flowmeters, which are equipped with additional pressure tubes and mounting brackets, installation costs are saved, failure points are reduced, and insulation measures are not taken.
(3) The detection sensor is not in direct contact with the measured medium and has stable performance and long life (for built-in type).
(4) The output is a pulse signal proportional to the flow rate, zero drift, and high accuracy. It can also output (4~20) MA signals as needed.
(5) Wide measuring range with a turndown ratio of 1:10 or higher. This is very useful for some steam metering of users who are very unbalanced with steam.
(6) The pressure loss is small, the operation cost is low, and it has certain energy-saving significance.
4, Vortex flowmeter measurement of the limitations of the analysis of the steam (1) on the straight pipe section of the higher requirements, the general minimum requirements before the straight pipe section in about 15D, after the straight pipe section in about 5D.
(2) Steam hammering can easily damage the probe and vortex generator.
(3) Not suitable for installation where the pipeline is vibrating or has strong interference.
(4) The temperature of the measured medium must not be too high. The maximum temperature cannot be higher than 400 degrees.
(5) The flowmeter with large diameter is now less stable (greater than DN250MM)
The vortex flowmeter overcomes many deficiencies of orifice flowmeters after use, the measurement of saturated steam is more accurate, more stable and easy to maintain. However, it is worth noting that since the aperture plate measurement technology has matured and is supported by corresponding national and international standards, the structure itself is simple, the cost is low, and the high temperature performance and vibration resistance are good. Therefore, for large and medium-sized pipelines, such as DN200mm or more In the pipeline, differential pressure flowmeters are used for orifice plates, especially for high pressure superheated steam. All orifice differential pressure flowmeters are used. For small and medium-sized pipelines, more and more vortex flowmeters are used. In addition, due to the high temperature and vibration of the vortex sensor is very unfavorable to the correct use, in addition to taking the necessary temperature, vibration damping measures, in actual use, should be installed in a small, well-ventilated position. If you find a false signal of interference, stop operation and check the cause to eliminate it. In addition, the fluid flow rate for measuring saturated steam must not be less than 5 m/s. Otherwise, the flow meter value is low. In addition to the above, it should also pay attention to the regular overhaul of steam meters. Because of its long-term exposure to high-temperature, high-pressure steam, it can easily cause damage to parts, corrosion, and clogging of impurities. Therefore, regular maintenance and regular maintenance are required.