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【Automatic control school】Flow meter series: Insertion flowmeter
What are the factors that affect the measurement error of the insertion flowmeter
Insertion flowmeter is a new type of flow measurement instrument developed on the basis of pipeline flowmeter.low cost,CanInstallation under pressureand other advantages, available inInstallation without waterTherefore, in some occasions where the installation of pipeline flowmeters is difficult and the installation cost is high, insertion flowmeters are often used to solve the problem of flow measurement, so this measurement method provides a good solution for flow measurement. However, when the insertion flowmeter is used in the field, due to the design defects of the flowmeter itself and the very complex installation conditions on site, the insertion flowmeter cannot achieve accurate and reliable flow measurement.
There are many factors that affect the measurement error of the insertion flowmeter, mainly including
Average Velocity Location
Plug-in sensor structure
Field installation conditions
Insertion flowmeter installation angle
At present, the research work on the insertion flowmeter mainly focuses on these aspects: the influence of the position of the average flow velocity is studied in the literature, and the flow measurement under the position of the average flow velocity is realized; Flow measurement at different insertion angles; the literature studies the structure of the insertion flowmeter, and replaces the impeller blade sensor with a thermal mass sensor to reduce the sensor's disturbance to the flow field and improve the stability of the measurement signal
The literature studies the on-site calibration method of the insertion flowmeter as a standard device, and solves the problem of on-site calibration under certain conditions; the literature studies a flanged pipeline flowmeter, which eliminates the error caused by uneven flow rate distribution. Improved measurement accuracy at low flow rates.
The above research work has well solved some of the key issues affecting the measurement error of the insertion flowmeter, and laid a foundation for the follow-up research to improve the performance of the insertion flowmeter, but none of the above studies have carried out the installation that affects the measurement error of the insertion flowmeter. The study of angle problems,
This problem is one of the key factors affecting the improvement of the flow measurement performance of the insertion flowmeter. Therefore, there are still some shortcomings in the research results, and it is urgent to carry out research on this problem.
Insert Thermal Mass Flow Meter Installation 8 Steps
- Use a torch or sharp cutting tool to hammer into the pipe. The diameter of the pipe opening must be at least Ø 13mm (do not insert the sensor probe into the smaller hole)
2. Remove the burrs on the faucet, the sharp edges may cause the flow distribution disorder and affect the accuracy of the flowmeter;
- Solder the MNPT ½” sleeve (Part No. 1) to the cutout. The correct insertion depth places the centerline of the sensor access hole in the probe at the centerline of the pipe
- Bolt a ½” ball (isolation) valve (Part No. 2) to both ends of the sleeve with FNPT threads. Seal the threaded connections with thread sealant. The lever on the ball valve should be up when the valve is open.
- Insert the sensor probe into the pipe through the ball valve (isolation valve). The correct insertion depth places the sensor at the centerline of the pipe.
6. Calculate the insertion depth of the sensor probe, depth S=A/2+B+C
A = the inner diameter of the pipe
B = pipe thickness
C=The distance from the top of the pipe to the upper end of the nut when the nut is fixed
- Connect the sleeve (Part No. 3) and the ball valve (isolation valve) on the meter, sealing the threaded connection with thread sealant. Tighten the nut (part number 4) with a wrench.
- Orient the flowmeter to ensure that the orientation markings on the probe (part number 5) point in the direction of flow.
Features - Advantages of Inserting Thermal Mass Flow Meters
The following are generally considered to be the main features and benefits of thermal mass flow meters.
Direct mass flow – no separate temperature or pressure transmitter required
High precision and repeatability - precise measurements and extraordinary repeatability
Turndown ratio 100 to 1
Low-End Sensitivity - Measured values down to 0.3Nm/s
Negligible pressure drop - does not impede flow or waste energy
No moving parts - eliminate costly bearing replacements and prevent undetected accuracy changes
Easy installation, can be installed without stopping the flow
Available in Pulse, 4-20mA, RS485 and HART
Flow, total flow, temperature and other display parameters
Site construction requirements
Site construction requirements
1. Before the sensor is installed, the instrument well must be done according to the requirements to ensure the construction safety of the installer and provide suitable installation conditions
2. Before ordering, make statistics of pipeline parameters, material, wall thickness, inner lining, outer circumference, installation point pressure, cable length, etc., to facilitate the production of fixtures
3. AC220V power supply is provided on site for drilling, and carbon steel pipes need to provide professional welding personnel and welding equipment
4. In order to ensure the progress, it is necessary to formulate detailed construction arrangements and cooperation plans, and to connect and coordinate with experienced personnel
5. The installation position of the instrument is determined by the length of the cable, and the longest cable for power supply is 30 meters
(Special installation tools and accurate positioning ensure that the same channel measurement sensor is in a straight line, which is an important measure to ensure long-term measurement accuracy and stability.)