1、 Instrument Introduction:
Temperature pressure compensation target flowmeterCan measure superheated steam at a pressure of 6.0MPa and 450 ℃; In saturated steam environments, some steam flow rates are too low to be suitable for instruments, and can only be solved by reducing the diameter. This can measure the advantage of low flow rates and can be used without changing the instrument diameter; In boiler steam applications, due to the significant difference in steam consumption between winter and summer, simply changing the target plate can meet the requirements of range conversion without the need to reorder instruments; In steam flow, in some cases, temperature and pressure are constantly changing, and temperature pressure compensation is necessaryintegratedThe target flowmeter can sample the temperature and pressure parameters of steam through sensors, and dynamically compensate for the flow rate based on the IAPWS-IF97 formula of the Water and Steam Properties Association, making steam measurement more accurate.
2、 Structure and working principle:
1. Structure
Temperature pressure compensation target flowmeterIt mainly consists of a measuring tube (housing), a new type of sensor (including flow blocking components), an accumulation display, and an output part. According to different media and working conditions, suitable sensors must be selected. Therefore, providing accurate measurement objects and parameters by users and selecting appropriate sensors by manufacturers are the key to whether the product can measure accurately.
2. Working principle
When the medium flows in the measuring tube, the pressure difference generated by its own kinetic energy passing through the blocking element (target flowmeter) exerts a force on the blocking element, and the magnitude of the force is proportional to the square of the medium flow velocity. Its mathematical expression is as follows:
F=CdAρV2/2
In the formula: the force acting on the F blocking component (kg)
Cd object drag coefficient
The axial projection area of the measuring tube by the A blocking component (mm2)
Medium density under ρ condition (kg/m3)
The average flow velocity of V medium in the measuring tube (m/s)
The force F received by the blocking element (target) is transmitted to the sensor through a rigidly connected transmission element (measuring rod), and the sensor generates a voltage signal output: V=KF
In the formula: V - voltage output by the sensor (mV), K - proportionality constant, F - force acting on the blocking element (target) (kg),
After pre amplification, AD conversion, and computer processing, this voltage signal can obtain the corresponding instantaneous flow rate and cumulative total amount.
3、 Application scope:
Temperature pressure compensation target flowmeterSuitable for high-temperature refining industry, such as diesel, asphalt, tar, C4 fractionation and other high-temperature media environments, it can effectively solve such flow measurement, and can measure medium temperatures up to 450 ℃; In the case of superheated steam, due to the high temperature and pressure of the medium, many instruments are not suitable for such working conditions.
4、 Advantages:
1. Suitable for various pipe diameters: 15-2000mm to larger.
2. Suitable for high and low temperature media: -196 ℃ -+450 ℃. Can accurately measure the flow rate of liquids, gases, vapors, viscous media, and various fluid media under various normal temperature, high temperature, and low temperature conditions.
3. Sensitivity *, capable of measuring ultra-low flow rates, capable of measuring low flow velocities of 0.08m/s.
4. Suitable for high-pressure working conditions: 0-42Mpa.
5. No movable parts, high accuracy.
6. Good repeatability, generally 0.1-0.08%, fast measurement.
7. Accurate measurement, high precision, and total measurement can reach 0.2%.
8. Good anti vibration and anti electromagnetic interference, can be used for dry calibration or weight hanging method.
9. Body material: carbon steel, 304, 316, 316L.
10. Power supply mode: 3.6V lithium battery; 24VDC power supply; Dual power supply: 3.6V lithium battery+24VDC power supply.
5、 Performance indicators:
1. Tested medium: liquid; Gas; steam
2. Nominal diameter pipeline type: 15~300mm clamp type: 15~600mm insert type: 100~2000mm
3. Nominal pressure: 0.6~42MPa
4. Medium temperature: -20 ℃~70 ℃ (normal temperature type); -196 ℃~+450 ℃ (high and low temperature type)
5. Degrees: ± 0.2%, ± 0.5%, ± 1.0%, ± 1.5%, ± 2.5%
6. Range: 1:3, 1:5, 1:10, 1:10 (gas), 1:10 (steam)
7. Compensation type: temperature compensation; Pressure compensation
8. Repeatability: 0.1%~0.08%
9. Power supply: Built in 3.6V lithium battery; External power supply 24VDC; 220VAC (only for split digital display)
10. Output format: On site display reading value; 4-20mA (two-wire system); Pulse; 0~10V; RS232/RS485 (optional)
11. Measurement tube material: carbon steel; 304； 316L; can also be provided according to user requirements
12. Explosion proof mark: intrinsic safety type (ExiallCT4) explosion-proof type (ExiallBT4)
13. Protection level: IP65; IP67
Note: The flange specifications of the flowmeter comply with the GB/T9115.1~9115.4-2000 series standards, and the pipeline type can produce small-diameter flowmeters such as DN6, DN8, DN10 according to user needs.
6、 Installation instructions:
1. Normal temperature, low temperature, and high temperature flow meters are installed horizontally, vertically, or upside down depending on different working conditions (according to the factory calibration sheet);
2. When the working temperature of the medium is above+300 degrees, users should take insulation measures for the flowmeter housing to prevent thermal radiation damage to the meter head (the working temperature of the meter head is -30 to+70 degrees). Similarly, for media with a working temperature below -100 degrees, anti freezing measures should also be taken;
3. To ensure accurate measurement of the flowmeter, it is required to set up front and rear straight pipe sections;
4. To ensure that the flow meter does not affect the system operation during inspection and replacement, bypass valves (3) and shut-off valves (1, 2) should be installed as much as possible;
5. Vertical installation can be used due to process requirements, and the flow direction of the measured medium can be from bottom to top or from top to bottom, but it should be explained to the supplier when ordering;
6. The diameter of the flowmeter should be as similar as possible to the diameter of the connected pipeline to reduce flow interference and measurement errors;
7. The flowmeter housing must be reliably grounded, and if there is no grounding condition, it should be explained to the manufacturer.
7、 Installation precautions:
1. There should be a straight pipe section before and after the measuring tube, and the diameter of the straight pipe section should be equal to the diameter of the flow meter measuring tube. If the diameters are different, a reducer should be used to connect them so that the inlet diameter is the same. The length of the upstream straight pipe section of the flowmeter is generally not less than 6-20D, determined according to different types of upstream flow resistance components, and the downstream straight pipe section is not less than 3-4D. The flowmeter is usually calibrated in a horizontal position and is generally installed in a horizontal pipeline. When it must be installed in a vertical pipeline, the hanging weight method must be used to calibrate the vertical installation status of the flowmeter, and the fluid direction should be from bottom to top.
2. For the convenience of maintenance and to prevent one-way force when the flowmeter is activated, a bypass pipeline is installed in parallel. A discharge pipe is installed downstream of the flowmeter to facilitate instrument cleaning and blowing. It is more necessary for measuring dirty fluids or media that are prone to solidification and crystallization. The target plate and measuring tube (body) should be installed coaxially. According to previous tests on a certain caliber, if the center of the target plate deviates 1mm from the center of the pipeline, it may cause a deviation of 1% to 2% in the flow coefficient. However, if the deviation is 1mm from the center of the pipeline, the impact is not significant;
3. When installing an explosion-proof target flowmeter, attention should be paid to checking whether there are explosion-proof markings and explosion-proof certificates, and whether the explosion-proof equipment is intact.
4. For small-diameter flow meters, due to the small diameter and relatively heavy weight of the flow meter, additional brackets should be installed to support the flow meter to prevent pipeline deformation or vibration during operation. For large-diameter flow meters, there is no need to install additional brackets.
8、 Precautions for use:
1. Before fluid flow, the downstream valve of the flowmeter should be closed and the upstream valve should be opened to allow fluid to enter the flowmeter section. Then slowly open the downstream valve of the flowmeter and close the bypass valve to allow the fluid to slowly increase. Avoid suddenly opening the valve to impact the target plate and damage the instrument.
2. After long-term operation of the flowmeter, in addition to cleaning the scale on the target plate and measuring tube, the hanging weight method should be used to check whether the characteristics of the force converter have changed. The hanging weight method is to apply a weight gravity in the same direction as the flow at the center of the target plate, adjust the instrument, and apply the force corresponding to the upper limit of the flow meter, which is calculated as F1 according to equation (16.6). Other flow points are added with relevant weights, and the output signal of the instrument is read to check the basic error and linearity of each point. The 'hanging weight method' is described in the product manual or other materials provided by the manufacturer, and can also be referred to.
3. The force exerted by the fluid on the target plate is different from the force exerted by the hanging weight, so the hanging weight method cannot replace real flow calibration. To obtain altitude, necessary real flow calibration is still necessary.