Problems existing in the application of vortex flowmeter in steam metering
2021-04-15
Vortex flowmeter can be used to measure liquid, gas, superheated steam, saturated steam, its unique design structure, so that it can measure high temperature steam, intelligent processor can achieve data change, the use of temperature/pressure automatic compensation and remote communication means, so that its measurement accuracy level and convenience can be greatly improved. Because of these significant advantages, vortex flowmeters are now widely used in petroleum, chemical, metallurgy, electric power, water treatment plants and other industries. Vortex flowmeter as a more common measurement method in steam settlement, its sensor according to the detection methods mainly have thermal, stress, capacitive, etc., of which capacitive has the advantages of strong shock resistance, but the price is high, the use is not common, stress type has the advantages of low price and wide range, but there are also some fatal weaknesses, difficult to overcome. Shanghai Esther Instrument is a professional vortex flowmeter manufacturer, in the long-term production and installation practice has mastered a lot of experience and skills, this article is for the use of stress vortex flowmeter problems, put forward their own views, and learn together. Through the problems existing in the use of vortex flowmeter, this paper analyzes several influencing factors in the measurement of vortex flowmeter, and finds out the solution and improvement measures.
Vortex flowmeter measurement includes three important parameters: pressure, temperature, frequency. Through the measurement of three parameters and the state of the steam, the tonnage of steam is calculated as the basis for settlement.
If the steam is in a state of saturated steam, as long as one of the pressure or temperature and the frequency of measurement can be calculated, because the pressure and temperature in saturated steam are one-to-one corresponding relationship, for superheated steam must measure the value of pressure and temperature at the same time, the level of superheat has a greater impact on the measurement of steam.
Pressure: Because for a certain amount of steam, the higher the steam pressure, the greater the corresponding density, so the greater the steam metering number, when the pressure of 1MPa, the corresponding saturated steam saturation temperature is 179 degrees, the density of 5.05kg/cm3, if the measured pressure is larger than the actual, such as the actual measurement of 1.11MPa, The density is 5.53kg /cm3, the corresponding steam volume settlement value will be larger, the deviation of 10%, for the user, it is necessary to pay a lot of costs. Therefore, in order to prevent the occurrence of such problems, it is recommended to parallel a pressure gauge at the same measuring point, requiring high accuracy, often compare, find the cause in time when there is a deviation, and find out the solution.
Temperature: In superheated steam, the accuracy of temperature is very important. For example: 1.1MPa superheated steam, the corresponding density at 250 degrees is 4.75kg /cm3, if the measured temperature is small, the corresponding density at 210 degrees is 5.24kg /cm3, that is, when we pay the fee, we have to pay 10% more to the steam supply party. Therefore, for cases where the investment is not large and the measurement error may be larger, like pressure, the same installation of a comparative thermometer has greater benefits for timely detection of problems.
Vortex parameter setting: The vortex type steam metering meter can automatically calculate the status of steam according to the parameters and conduct settlement, and some need to be manually set. Due to different states, the calculated data of a vortex meter has great errors. For example, the steam parameter is 1.1MPa pressure, 250 degrees temperature, obviously superheated steam, the corresponding density is 4.746, if the set is saturated steam, and the corresponding saturation temperature is 183 degrees, the density is 6.131, the number measured by saturated steam is 29% more than the number measured by superheated steam, this number may seem incredible to the user. But in the actual situation is there, in the case of users do not understand, some heating companies are still doing so, damaging the interests of consumers.
In the current measurement, especially in the case of the reduction of users in the summer, due to the distance of pipeline transportation, the steam in many places is in the unsaturated steam state, and the current instrument does not distinguish the state of unsaturated steam, according to the saturated steam to settle, it is not reasonable for users, but there is no better solution.
Under certain steam parameters, each diameter of the vortex flowmeter has a corresponding metering maximum flow and minimum flow, out of the range will cause a great error, the instrument selection is too large or too small are not suitable, the author has investigated the options of the internal instrument, the selection of the previous table is too large, small flow will not go to the table, and then the table options are small, but there is a problem, Users use the characteristics of the table, intentionally increase the amount of gas, found that more than a certain flow, the steam meter instead of showing the flow value of the original smaller, resulting in greater loss, in this case, it is necessary to install the throttle device on the valve position in front of the table to limit the maximum flow to solve. Therefore, it is necessary to adhere to the upper and lower limits of the instrument provided by the installation watch factory for table selection.
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