KR20180056003A - Gas flow automatic measuring device for flow meter calibration - Google Patents

Abstract

Disclosed is an automatic gas flow rate measuring device for calibrating a flow meter that can improve measurement accuracy of a flow rate through an automatic adjusting manner. The automatic gas flow rate measuring device includes: a first control unit having a regulator for maintaining pressure of a gas at a constant level; a first measuring unit connected to a branched pipe of the first control unit and having a standard for measuring a flow rate of the inflow gas; a second measuring unit connected to a branched pipe of the first measuring unit; a second control unit connected to a branched pipe of the second measuring unit and having a mass flow meter for controlling a quantity of the gas flowing along the pipe per unit time; and a computer for comparing information about the flow rate delivered from the mass flow meter and calculating a calibration value, so that a flow rate measured value of a meter to be calibrated is calibrated.

Description

TECHNICAL FIELD [0001] The present invention relates to an automatic gas flow rate measuring apparatus for a flow meter,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an apparatus for automatically measuring a gas flow rate, and more particularly, to an apparatus for automatically measuring a flow rate of a flowmeter capable of improving the accuracy of a flow rate measurement value through a standard machine and a mass flow controller.

Generally, to measure the flow rate of a gas system, a flow meter mounted on a conduit or the like through which gas flows is used. If the pressure or flow range of the flowmeter is different, an error may occur. To measure the flowmeter correctly, calibrate the flowmeter to the standard condition suitable for the applicable site conditions. In particular, in order to calibrate a gas flow meter, it is necessary to provide a device having a high measurement accuracy and a wide measuring range.

There are bell prover and piston prover as standard equipment for calibrating various flowmeters to standard condition.

Since standard instruments such as Bell Prover and Piston Prowber are based on volumetric methods, bulky and heavy moving measurements are nearly impossible. In addition, there is a problem that it is costly.

In addition, since the measurement range of the flow rate is not so wide, it is necessary to use several standard instruments having different capacities according to the range to be measured.

Accordingly, in order to satisfy the measurement range of the flow rate, several standard machines having different capacities are required, and it is difficult to secure a space for installing the standard machine.

As a related art related to the present invention, there is Korean Patent Laid-Open Publication No. 2003-0082688 (published on October 23, 2003), which discloses a standard flow calibration gas flow meter for a flow meter.

It is an object of the present invention to provide an apparatus for automatically calibrating a flow meter for a flow meter, which can improve the reliability of a device so that it can be used as a standard device for calibrating a flow meter and improve the accuracy of the flow measurement value.

The present invention also relates to an apparatus for automatically calibrating a flow meter for a flow meter, which allows a computer to automatically perform all the processes and control of the apparatus, thereby shortening the time required for the calibration work.

According to an aspect of the present invention, there is provided an apparatus for automatically measuring a flow rate of a flow meter, comprising: a first controller including a regulator for maintaining a pressure of a gas constant; A first measurement unit connected to the branched conduit of the first control unit and including a standard device for measuring a flow rate of the introduced gas; A second measuring unit including an calibrating device connected to a branched pipe of the first measuring unit; A second controller including a mass flow controller connected to the branched pipe of the second measuring unit and controlling the amount of gas moving per unit time moving along the pipe; And a computer for calculating a calibration value by comparing and analyzing the flow rate information of the gas delivered from the mass flow rate controller, wherein the flow rate measurement value of the calibrated instrument is corrected based on the flow rate measurement value of the standard instrument .

The standard may be a laminar flow element.

The first control unit may include a first pressure gauge for measuring a pressure of the pipe passing through the regulator, and a first thermometer for measuring a temperature of the pipe.

The first measurement unit may include a first opening / closing valve located in a conduit coupled to an outlet side of the standard device.

The second measuring unit may include a second opening / closing valve located in a conduit coupled to an outlet side of the calibrating device.

The second control unit may include a third open / close valve located in a conduit coupled to an inlet side of the mass flow controller.

The second control unit includes a second pressure gauge for measuring the pressure of the conduit and a second thermometer for measuring the temperature of the conduit. The second pressure gauge and the second thermometer are connected to the inlet of the third opening / It can be located in the pipeline.

The first measurement unit may include a first ON valve / OFF valve located in a conduit coupled to an inlet side of the standard unit and preventing gas from leaking from the first open / close valve.

The second measuring unit may include a second ON valve / OFF valve located in a conduit coupled to an inlet side of the calibrating device and preventing gas from leaking from the second opening / closing valve.

The flow rate of the gas may range from 20 to 20,000 sccm.

The equation for calculating the flow rate of the gas may satisfy the following equation (1).

[Equation 1]

q _m = mass flow rate (kg · s ^-1 )

P ₁ = upstream absolute pressure (Pa)

P ₂ = downstream absolute pressure (Pa)

P = (P ₁ + P ₂ ) / 2 (Pa)

T = absolute temperature of the fluid used (K)

T _N = Standard temperature, 273.15K (K)

ρ _N = standard density of the fluid used (kg · m ^-3 )

η _{( P, T )} = gas kinematic viscosity [Pa · s] under given pressure and temperature conditions,

P _N = standard pressure, 101325 Pa (Pa)

Z _N = gas compression coefficient under standard conditions (-)

Z _{(P, T)} = gas compression coefficient (-) under given pressure and temperature conditions

C _G = experimentally determined correction factor (m ³ )

The apparatus for automatically calibrating a flow meter for a flow meter according to the present invention has a wide range of mass flow controllers (MFCs) in one system, and is excellent in expandability and has a wide flow measuring range. Further, the calibrating device can be calibrated sequentially through the opening / closing operation valve, the labor of the manpower inputted into the calibrating operation can be reduced, and the time of the calibrating operation can be shortened.

In addition, the pressure and temperature inside the pipe can be measured and controlled by a thermometer and a pressure gauge located on the upstream and downstream sides of the apparatus, thereby improving the measurement accuracy by correcting the measured flow rate.

Therefore, the apparatus of the present invention has the following effects in terms of efficiency and stability.

In terms of efficiency, the standard machine is automatically selected according to the measuring point of the calibrator input to the system, and the set point is reached through the PID control, so that the working time is reduced and the nozzle and piping are not replaced do. Thus, it is possible to eliminate an error or an error due to the replacement of the work element.

The pressure and temperature applied to the standard are controlled by monitoring in real time, and the flow rate can be controlled through the valve opening / closing and mass flow controller according to the prescribed algorithm, thus improving the stability of the operation.

1 is a schematic view showing an apparatus for automatically measuring a flow rate of a flowmeter according to the present invention.
2 is a cross-sectional view of an apparatus for automatically measuring a flow rate of a flowmeter according to the present invention.
3 is an algorithm illustrating a flow rate control method of a mass flow controller according to the present invention.
FIG. 4 shows a calibration automation software screen of a computer according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

When the flowmeter is calibrated, it is measured three times at one flow rate, and the process of increasing, decreasing, and increasing at the flow rate is repeated. That is, when measuring five points, it is necessary to readjust the flow rate at least 15 times, and to include the time required to stabilize the signal and the time to record the measurement data.

In addition, since the degree of deviation varies greatly depending on the skill of the measurer, it is desirable to minimize the manpower and deviation to be inputted to the calibration work.

In the present invention, such a calibration operation is automatically performed by a computer, thereby minimizing manpower and deviation in the calibration operation. In addition, it is expected that the correction of the report will be reduced by transmitting the flow measurement value measured in the standard machine directly to the computer, thereby preventing the error from entering the flow measurement value directly.

FIG. 1 is a schematic view showing an apparatus for automatically measuring a flow rate of a flow meter according to the present invention, and FIG. 2 is a sectional view showing an apparatus for automatically measuring a flow rate of a flow meter according to the present invention.

1 and 2, the apparatus for automatically measuring a flow rate of a flow meter of the present invention includes a first control unit 100, a first measurement unit 200, a second measurement unit 300, The first measurement unit 200, the second measurement unit 300, and the second control unit 400. The first control unit 100, the first measurement unit 200, the second measurement unit 300, and the second control unit 400 are examples of devices for measuring the flow rate of the gas, .

1, the description will be made assuming that the direction of the first control unit 100 is the upstream side of the apparatus and the direction of the second control unit 400 is the downstream side of the apparatus, with reference to the second measuring unit 300. [

The first controller 100,

The first control unit 100 includes a regulator 110 that keeps the pressure of the gas flowing into the apparatus constant. The regulator 110 can convert and output the pressure of the fluctuating gas to a required level.

The first control unit 100 further includes a first pressure gauge 130 for measuring the pressure of the channel passing through the regulator 110 and a first thermometer 120 for measuring the temperature of the channel. The first pressure gauge 130 and the first thermometer 120 measure the flow rate of the calibrating device 350 based on the flow rate measurement value of the standard device 250 by measuring the pressure and the temperature of the inlet side channel of the standard device 250 The deviation with respect to the value can be corrected, and the measurement accuracy can be improved.

The length of the first control unit 100 may be about 30 to 40 cm, but is not limited thereto.

The first measuring unit 200,

The first measurement unit 200 includes a standard unit 250, a first ON valve / OFF valve 240, and a first open / close valve 260 connected to a branch pipe of the first control unit 100.

The standard machine 250 measures the flow rate of the incoming gas and corrects the deviation of the calibrated instrument 350 with respect to the flow rate measurement value based on the measured value of the flow rate. The apparatus for automatically calibrating a flowmeter for a flow meter has at least one standard apparatus 250 and may include four or more standard apparatus 250 as shown in FIG. The standard machine 250 is composed of a laminar flow element installed at predetermined intervals, and the standard machine measures the flow rate using the laminar flow element. The laminar flow element converts the flow of the fluid in the channel into a laminar flow in a constant direction without turbulence. Since the flow rate of the fluid forming the laminar flow constantly and without turbulence is constantly proportional to the pressure difference between the upstream and the downstream, precise flow measurement is possible through differential pressure measurement.

A first opening and closing valve 260 is disposed in the conduit connected to the outlet of the standard device 250. The valve 260 may be constituted by one valve 260 per standard device 250. The distance between the standard device 250 and the first opening / closing valve 260 may be about 10 to 20 cm, but is not limited thereto. Referring to FIG. 1, the distance between the standard device 250 of the present invention and the first opening and closing valve 260 is set to 17 cm, and the length of the upstream straight pipe portion is sufficiently secured. The length of the upstream side straight pipe portion may be 4 to 5D depending on the state of the piping and the installation, and the length of the downstream side straight pipe portion may be 5D or more. 4D means 4 times the pipe diameter, and 5D means 5 times the pipe diameter.

A first ON valve / OFF valve 240 is located in a conduit coupled to the inlet of the standard device 250. The valve 240 prevents gas from leaking from the first opening / closing valve 260, Pass the gas through the desired pipeline. The distance between the standard device 250 and the first ON / OFF valve 240 may be approximately 10 to 20 cm, but is not limited thereto. Referring to FIG. 1, the distance between the standard device 250 of the present invention and the first ON valve / OFF valve 240 is 17 cm, thereby ensuring a sufficient length of the upstream straight pipe portion.

In addition, the length of the first measuring unit 200 may be about 30 to 50 cm, but is not limited thereto.

The second measuring unit 300 measures

The second measuring unit 300 includes a calibrating device 350, a second ON valve / OFF valve 340 and a second opening / closing valve 360 connected to the branch pipe of the first measuring unit 200 do.

The calibrating device 350 is compared and analyzed based on the flow measurement value of the standard device 250, and the flow measurement value is calibrated so that the deviation is satisfied within the tolerance. Accordingly, the calibrating device 350 can be calibrated to a standard state corresponding to the use conditions of the site. The calibrating device 350 may be connected to the branch pipe of the first measuring unit 200 and may be calibrated through the second opening / closing valve 360.

As shown in Fig. 1, when eight calibrating devices 350 are provided, they can be calibrated sequentially.

A second opening and closing valve 360 is disposed in a conduit connected to an outlet of the calibrating device 350 and the valve 360 is constituted by one valve 360 per one calibrating device 350 .

OFF valve 340 is disposed in a conduit coupled to the inlet side of the calibrating device 350. The valve 340 prevents the gas from leaking from the second opening and closing valve 360 And pass the gas through the desired pipeline.

Various devices can be connected to the calibrating device 350 included in the second measuring part 300 so that the calibrating device 350 can be moved by separating the lower side plate of the calibrating device 350 . The distance or length between the devices can be adjusted according to the size and structure of the calibrating device 350. The length of the second measuring unit 300 may be about 40 to 50 cm, but is not limited thereto.

The second controller 400,

The second control unit 400 includes a mass flow controller (MFC) 450 and a third open / close valve 460 connected to the branch pipe of the second measurement unit 300.

The mass flow controller 450 is connected to the branched channel of the second measuring unit 300 and adjusts the amount of gas moving per unit time moving along the channel. The measured value of the target flow rate can be reached through the mass flow controller 450.

The third opening and closing valve 460 is located in a conduit connected to the inlet of the mass flow controller 450. The valve 460 is constituted by one valve 460 per one of the mass flow controllers 450. [ .

The second controller 400 further includes a second pressure gauge 430 for measuring the pressure of the conduit and a second thermometer 420 for measuring the temperature of the conduit. The second pressure gauge 430, (420) may be located in a conduit connected to the inlet side of the third opening / closing valve (460).

The second pressure gauge 430 and the second thermometer 420 measure the pressure and the temperature of the inlet side conduit of the mass flow controller 450 and measure the pressure and temperature of the conduit on the basis of the measured flow rate of the standard device 250 350 can be calibrated with respect to the flow measurement value, and the measurement accuracy can be improved.

The length of the second control unit 400 may be about 40 to 50 cm, but is not limited thereto.

Further, the height of the apparatus for automatically measuring the flow rate of the flowmeter of the present invention is approximately But it is not limited thereto.

The apparatus for automatically measuring a flow rate of a flow meter of the present invention includes a computer (FIG. 4) for calculating a calibration value by comparing and analyzing flow information of a gas delivered from the mass flow controller 450. The information includes pressure, temperature, flow range, etc. of the gas flow rate.

As soon as the measured flow measurements are transferred to the computer, the computer reads the measured pressure and temperature signals from the standard flow meter 250 and then analyzes the deviation to the flow measurement values, Value to be reached. As described above, the computer automatically initializes and controls the apparatus section, thereby reducing the variability of the deviation, which has changed according to the skill of the measurer. In addition, it is possible to shorten the workforce to 3 ~ 8 minutes compared to 20 ~ 40 minutes which is the time of the existing calibration work.

The measurement principle of the standard device 250 of the present invention is a measurement method using a differential pressure, and when the flow rate is out of range, a pressure higher than a pressure acceptable to the standard device 250 may be applied. Accordingly, when the allowable pressure is exceeded, the pipeline is blocked through the first opening / closing valve 260 to protect the standard device 250.

The flow rate range of the gas (air, N _2, etc.) measured by the apparatus for measuring flow rate of a flow meter for calibration of the present invention may be 20-20000 sccm. If it is less than 20 sccm, there is a problem that measurement is impossible since the measurement range of the standard machine 250 deviates by a small amount. Conversely, when the pressure exceeds 20000 sccm, the pressure exceeding the allowable pressure may be applied to the standard unit 250 as described above.

The equation for calculating the flow rate of the gas may satisfy the following equation (1).

[Equation 1]

q _m = mass flow ^{(kg · s -1), P} 1 = absolute upstream pressure (Pa), P ₂ = downstream absolute pressure (Pa), P = (P 1 + P 2) / 2 (Pa), T = absolute temperature of the fluid used (K), T _N = standard _{temperature, 273.15K (K), ρ N} = standard density of the fluid used ^{(kg · m -3), η} (P, T) = a given pressure and under the temperature condition the gas dynamic viscosity _{[Pa · s], P N} = standard _{pressure, 101325Pa (Pa), Z N} = gas compressibility factor under normal conditions, _{(-), Z (P,} T) = a given pressure and temperature conditions, (-), C _G = experimentally determined correction factor (m ³ )

[Table 1]

E-05 means 10 ^{- 5} , and E-09 means 10 ^{- 9} .

Solving Equation 1 with reference to Table 1, q _m = 328373 (365838 - 290907) - 1.293 - 273.15 - 1 - 2.57 占 (E-09) / 273 - 1.0918 17.19 占 101325. Solving the right equation gives a value of 4.04Х (E-05), which is the mass flow rate of the gas.

Referring to FIG. 3, the flow rate control method of the mass flow controller 450 of the present invention is a PID (proportional-integral-differential) control method, and is a proportional integral differential control method.

This is an automatic control method for reaching the set point, and the error is calculated by comparing the mass flow rate value measured at the standard machine 250 with the set point value, and then the control value is determined based on the error. The related expression is as follows.

[Formula 2]

Manipulated variable (u) = K _p × deviation + K _i × cumulative value of deviation + K _d × difference with previous deviation

K _p = proportional gain, K _i = integral gain, K _d = differential gain

The K _p is a proportional gain multiplied by the error signal, which has the effect of reducing the working time. The K _i is obtained by integrating the error signal. And has an effect of eliminating the error of the steady state with the integral gain multiplied. K _d is a differential gain multiplied by the differential value of the error signal, which has the effect of improving the stability of the system. Improving the performance of a mass flow controller using this PID control method depends on how the gain values are determined.

The mass flow controller 450 of the present invention is operated by a 0 to 5V electrical signal, and the manipulated variable u is 0 to 5V. In the case of using the mass flow controller 450 in the range of 2000 sccm, the flow rate of 0 sccm is measured at 0 V and the flow rate in the range of 2000 sccm at 5 V is measured.

In the PID control, based on the cumulative value of the deviation and deviation, and the variation of the deviation, The manipulated variable is determined. When approaching the target value using only the deviation, a "residual deviation" occurs as the manipulated variable becomes smaller. In order to eliminate such "residual deviation ", an integral operation for eliminating the deviation is required by accumulating minute residual deviations temporally to increase the manipulated variable.

Further, when the deviation from the suddenly occurring disturbance is found, and when the deviation is larger than the previous deviation, the differential operation is required to operate the response to the disturbance by increasing the manipulated variable.

For example, the manipulated variable u can be obtained by referring to the equation (2). The manipulated variable u has a value of 0.168 V when K _p = 0.5, K _i = 0.01, K _d = 0.005, deviation = 0.3 V, and last deviation = 1.1 V.

The apparatus for automatically calibrating a flowmeter for measuring flowmeter of the present invention can automatically control the control of the apparatus by the computer, thereby minimizing the difference in flow measurement value and the magnitude of deviation depending on the measurer.

In addition, by analyzing the deviation from the flow target value set by the mass flow controller based on the flow measurement value measured by the standard device, the flow rate of the calibrating device can be calibrated to the standard state, thereby improving the measurement accuracy have.

In addition, there is an advantage that the manufacturing cost of the apparatus is low and the mobility is easy.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is to be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

100:
110: Regulator
120: First thermometer
130: 1st pressure gauge
200: first measuring unit
240: First ON valve / OFF valve
250: Standard equipment
260: first opening / closing valve
300: second measuring unit
340: Second ON / OFF valve
350: Calibrator
360: second opening / closing valve
400: second control section
420: second thermometer
430: 2nd pressure gauge
450: mass flow controller
460: Third open / close operation valve

Claims (11)

1. An apparatus for automatically measuring a flow rate of a gas for sequentially moving a first control unit, a first measurement unit, a second measurement unit, and a second control unit along a channel, comprising:
A first control unit including a regulator for keeping the pressure of the gas constant;
A first measurement unit connected to the branched conduit of the first control unit and including a standard device for measuring a flow rate of the introduced gas;
A second measuring unit including an calibrating device connected to a branched pipe of the first measuring unit;
A second controller including a mass flow controller connected to the branched pipe of the second measuring unit and controlling the amount of gas moving per unit time moving along the pipe; And
And a computer for comparing the flow rate information of the gas delivered from the mass flow controller and calculating a calibration value,
Wherein the flow rate measurement value of the calibrating device is calibrated based on the flow rate measurement value of the standard device.
The method according to claim 1,
Characterized in that the standard is comprised of a laminar flow element.
The method according to claim 1,
The first control unit
A first pressure gauge for measuring a pressure of the pipeline passing through the regulator, and a first thermometer for measuring a temperature of the pipeline.
The method according to claim 1,
Wherein the first measuring unit includes a first opening / closing operation valve located in a conduit coupled to an outlet side of the standard device.
The method according to claim 1,
Wherein the second measurement unit includes a second opening / closing operation valve located in a conduit coupled to an outlet side of the calibrating device.
The method according to claim 1,
Wherein the second control unit includes a third open / close valve positioned in a conduit coupled to an inlet side of the mass flow controller.
The method according to claim 1,
The second control unit includes a second pressure gauge for measuring the pressure of the conduit, and a second thermometer for measuring the temperature of the conduit,
Wherein the second pressure gauge and the second thermometer are located in a conduit connected to an inlet side of the third opening / closing valve.
The method according to claim 1,
The first measuring unit
And a first ON valve / OFF valve located in a conduit connected to an inlet side of the standard device for preventing gas from leaking from the first opening / closing valve.
The method according to claim 1,
The second measuring unit
And a second ON valve / OFF valve located in a conduit connected to an inlet side of the calibrating device to prevent gas from leaking from the second opening / closing valve.
The method according to claim 1,
Wherein the flow rate of the gas is 20 to 20,000 sccm.
The method according to claim 1,
Wherein the equation for calculating the flow rate of the gas satisfies the following equation (1): " (1) "
[Formula 1]

q _m = mass flow rate (kg · s ^-1 )
P ₁ = upstream absolute pressure (Pa)
P ₂ = downstream absolute pressure (Pa)
P = (P ₁ + P ₂ ) / 2 (Pa)
T = absolute temperature of the fluid used (K)
T _N = Standard temperature, 273.15K (K)
ρ _N = standard density of the fluid used (kg · m ^-3 )
η _{( P, T )} = gas kinematic viscosity [Pa · s] under given pressure and temperature conditions,
P _N = standard pressure, 101325 Pa (Pa)
Z _N = gas compression coefficient under standard conditions (-)
Z _{(P, T)} = gas compression coefficient (-) under given pressure and temperature conditions
C _G = experimentally determined correction factor (m ³ )

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