Problems in the application of vortex flowmeter in steam measurement

2020-09-30
 Problems in the application of vortex flowmeter in steam measurement

The measurement of vortex flowmeter includes three important parameters: pressure, temperature, and 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 state of the steam is saturated steam, the amount of steam can be calculated by measuring one of the pressure or temperature and the frequency of the measurement, because the pressure and temperature in the saturated steam have a one-to-one correspondence, and the superheated steam must be at the same time Measure the value of pressure and temperature. The degree of superheat has a greater impact on steam measurement.

Pressure: 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 is 1MPa, the corresponding saturated steam has a saturation temperature of 179 degrees and a density of 5.05kg/ cm3, if the measured pressure is larger than the actual pressure, such as the actual measured 1.11MPa, the density is 5.53 kg/cm3, the corresponding steam volume settlement value will be too large, with a deviation of 10%. For the user, It will cost a lot more. Therefore, in order to prevent such problems from occurring, it is recommended to connect a pressure gauge in parallel at the same measuring point, which requires high accuracy, and compares frequently. When there is a deviation, find the cause in time and find a solution.

Temperature: In superheated steam, the accuracy of temperature is very important. For example: 1.1 MPa superheated steam, the corresponding density at 250 degrees is 4.75 kg/cm3, if the measured temperature is too small, the corresponding density at 210 degrees is 5.24 kg/cm3, which is the time to pay We have to pay 10% more to the steam supplier. Therefore, for situations where the investment is not large and large measurement errors may occur, like pressure, the same installation of a comparison thermometer is of great benefit to timely detection of problems.

Vortex street parameter setting: The vortex street type steam meter automatically calculates the state of the steam according to the parameters and performs settlement, and some requires manual setting. Due to the different conditions, for a vortex street meter, The calculated data has great errors. For example, the steam parameter is 1.1 MPa, the temperature is 250 degrees, it is obviously superheated steam, and the corresponding density is 4.746. If the saturated steam is set, the corresponding saturation temperature is 183 degrees, and the density is 6.131. It is 29% more than the number of superheated steam metering. This number may seem incredible to users, but it does exist in actual situations. Some heating companies are still doing this without the user’s understanding. The interests of consumers.

In the current metering, especially when the number of users decreases in summer, due to the long distance of pipeline transportation, the steam in many places is in the state of unsaturated steam, and the current meter does not distinguish the state of unsaturated steam, according to the saturated steam It is also unreasonable for users to settle accounts, but there is no better solution yet.

Under certain steam parameters, each caliber of the vortex flowmeter has a corresponding maximum flow rate and minimum flow rate. Exceeding the range will cause a great error. It is not appropriate to choose an instrument that is too large or too small. I have done a survey on the option of the meter. In the past, the meter selection was too large and the meter was not used for small flow. Later, the meter option was small, but another problem occurred. The user used the characteristics of the meter to increase the steam consumption intentionally, and found that it exceeded a certain After the flow rate is reached, the steam meter displays the smaller flow value, which causes greater losses. In this case, it is necessary to install a throttling device on the valve position in front of the meter to limit the maximum flow to solve this problem. Therefore, the upper and lower limits of the meter provided by the meter factory must be installed to select the meter.

 


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