JP3442112B2 - On-line correction method of pipeline flow meter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-line correction method of a flow meter measurement value used in a pipeline for leak detection using a transient response calculation method.

[0002]

2. Description of the Related Art As a method of correcting the value of a flow meter used in a pipeline without stopping the operation of the pipeline, when a fluid to be transported is a liquid, a volume measuring method using a pipe prober and an accurate calibration are used. The standard flow meter is installed in series. When the fluid to be transported is gas, a method of using a supersonic nozzle flowmeter as a reference flowmeter in the latter method is known. (Bake
r, CR, “An Introductory Guide To Flow Measuremen
t ”., Mechanical Engineering Publications Limite
d, London, P43.) In the volume measuring method using a pipe prober (Fig. 5), by opening valves A and B and closing valve C, a steady flow passing through the loop part is created, and the sphere is controlled by the sphere control part E. Send it into the loop part. The volume between a and b is divided by the passage time of the sphere passing through the position a and reaching the position b to obtain an accurate flow rate,
The indicated value of the flow meter is corrected based on the flow rate at that time.

On the other hand, in the method (FIG. 6) in which the accurately calibrated reference flowmeter is installed in series, the valves A and B are opened and the valve C is opened.
Is closed to create a steady flow passing through the reference flow meter G, and the reference value of the reference flow meter G is corrected to the positive value of the reference flow meter G.

Even in a pipeline where leak detection is performed using a transient response calculation method, the online correction of the flow meter can be solved by these above-mentioned conventional methods, but the transient response calculation disclosed in the present invention is performed. There is no prior art similar to the law-based online correction method.

[0005]

As described above, in the prior art, it is necessary to always install a large-scale loop piping system including a reference flow meter or a pipe prober for each flow meter to be corrected. There is a problem in that it is necessary to secure and make an investment for installation, and that the reference flow system itself must be calibrated periodically.

It is an object of the present invention to utilize a leak position calculation method, which is one of the functions of a pipeline leak detection method using a transient response calculation method, to constantly perform a large-scale loop piping system including a reference flow meter or a pipe prober. It is to provide a means for performing on-line correction of a flow meter without installing it.

[0007]

According to the present invention described below, the pressure and flow rate at both ends of a pipeline are periodically measured, and the transient response of the pressure and flow rate in the pipeline is calculated in real time to detect leakage. In the pipeline for calculating the leakage position and the leakage position, the diffusion valve V ₁ and the diffusion valve V ₁ for leakage test are provided at different positions in the pipeline.
₂ is installed, (1) the diffusion valve V ₂ is closed, the diffusion valve V ₁ is opened to perform a leak position calculation step 1, and (2) the diffusion valve V ₁ is closed, and the diffusion valve V ₂ And the leakage position calculation in step 1 and (3) the deviation between the leakage detection position and the position of the diffusion valve V _{1 in} step 1 and the deviation between the leakage detection position and the position of the diffusion valve V _{2 in} step 2 It is possible to solve the problem by using the comparison calculation step of calculating the flow rate error at both ends of the pipeline based on the comparison of 1. and the online correction method of the flowmeter at both ends of the pipeline.

[0008]

[Operation] In a pipeline having a plurality of withdrawal points on the way, the pressure and flow rate at the inlet and outlet of the pipeline and the withdrawal flow rate at the withdrawal point on the way are periodically measured to determine the pressure and flow rate in the pipeline. Leak detection method (Wylie, EB, and Streeter, VL, “Fluid Trd” that detects leak and calculates leak position by calculating transient response in real time.
ansients in Systems ”, Prentice-Hall, Inc., P273-
284. etc.) by an inventor of the present invention (Kiuchi, “Detection of Leakage Position by Transient Response Calculation of Pipeline”, The Japan Society of Mechanical Engineers, Vol. 57, No. 541, P3000-). 3007.). The present invention is directed to online correction of the inlet and outlet flowmeters of a pipeline to which such a leak detection method is applied, and further the withdrawal flowmeters on the way.

In the present invention, first, the difference in the middle of the pipeline is
Emission valve V for leak test at two known positions₁ ,
Emission valve for leak test V₂ Set up. However, these emissions
It is not necessary to install a flow meter to measure the quantity. Where the dissipation
Valve V₂ Emission valve V with the valve closed₁ The release valve
V₁ Since the amount of emission from the ₁ 
Emissions from are detected as leaks and leak locations are calculated
(Leakage position calculation step 1). Next, the diffusion valve V₁ Closed
Direct release valve V₂ If the valve is opened, the diffusion valve V₂ Emissions from
Is not measured, the diffusion valve V₂ Leakage from the
And the leak position is calculated (leak position calculator
2).

The target unknowns are the error (the amount to be corrected) ε ₁ of the inlet flow meter and the error ε ₂ of the outlet flow meter. If these are given correctly, the leakage obtained from the leakage position calculation step 1 The position matches the position of the diffusion valve V ₁ , and similarly, the leakage position obtained from the leakage position calculation step 2 must match the position of the diffusion valve V ₂ . Obtaining such correction amounts ε ₁ and ε ₂ (comparison process of correction amounts)
Is easy because two conditions (leakage position calculation steps 1 and 2) are given to these two unknowns, and the amount ε ₁ to be corrected by the inlet flowmeter and the correction amount of the outlet flowmeter are corrected. The power ε ₂ is detected.

Further, when there are N drawing points in the middle of the pipeline and the drawing amount at the drawing points is measured,
Leakage test is performed by sequentially setting the output of the withdrawal flowmeter to zero, and N conditions are newly generated. As a whole, N + 2 unknowns are given the same number of conditions, so all flowmeters are corrected. The required amount is required.

In this way, a leak test diffusion valve is provided in a pipeline that implements a leak detection method based on transient response calculation, and a pseudo leak test is performed a number of times corresponding to the number of flowmeters to be corrected. Since the position can be calculated, the flow rate at which the actual leak position and the calculated leak position coincide with each other can be calculated, and the correction amount can be determined from the difference between the calculated flow rate and the measurement value of the flow meter.

According to the present invention, by providing the leakage test diffusion valves at two places in the pipeline at most, it is possible to perform online correction of all flowmeters of the pipeline in which the fluid to be transported is gas or liquid. In the case of a gas pipeline, since a diffusion tower is generally installed, this can be substituted. Also, existing withdrawal valves can be substituted for these.
In this diffusion valve, the error that each flow meter has is identified by sequentially repeating opening and closing. Since the calculation formula becomes complicated, each correction amount may be obtained by performing optimization by the linear programming method.

[0014]

The present invention will be described in more detail with reference to the following examples.

FIG. 1 is an explanatory diagram for carrying out the present invention with the simplest pipeline having no drawing point in the middle.

FIG. 2 is an explanatory diagram for carrying out the present invention in a pipeline having one drawing point in the middle.

FIG. 3 is a conceptual diagram of a measuring system and a computing system when the present invention is implemented by a pipeline having N drawing points in the middle.

FIG. 4 is a graph showing the correction amounts of the inlet and outlet flow meters and the objective function obtained by the linear programming method.

An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the configuration of the simplest pipeline to which the above-mentioned leak detection method is applied. In the figure, F ₁ and P ₁ are the flow rate and pressure at the pipeline inlet 1, F
₂ and P ₂ are the flow rate and pressure at the pipeline outlet 2, they are measured periodically, and the transient response calculation is performed with the inlet and outlet pressures P ₁ and P ₂ as boundary conditions. In addition, the calculated flow rate F ₁ c at the inlet and outlet obtained by transient response calculation,
It is assumed that F ₂ c matches the measured values F ₁ and F ₂ within the accuracy range of each flow meter. Where is the entrance 1
A leakage test diffusion valve V is installed at a position X at an arbitrary distance from
It is assumed that the leakage test diffusion valve V is open.
If the discharge flow rate from this diffusion valve V is measured,
Otherwise, the emission will be considered as a leak, so the
The distance from the leak position X to the leak position X is roughly calculated by the following equation.

[0020]

[Equation 1] F: Numerically calculated average flow rate ΔF ₁ : F ₁ -F ₁ c ΔF ₂ : F ₂ c-F ₂ F ₁ c, F ₂ c: Numerically calculated flow rate at inlet and outlet L: L ₁ + L ₂ + L ₃ Therefore, the diffusion valve V ₂ in FIG. 1 is closed and the diffusion valve V ₁ is opened.
In the above condition, F in the formula (1) is represented as F _a, and
Similarly, if ΔF ₁ is expressed as ΔF _1a and ΔF ₂ is expressed as ΔF _2a , the leakage potential is
The following equation for obtaining the position X ₁ is obtained. Therefore, the diffusion valve V ₂ is closed.
The measured values that are obtained when the chain is closed and the diffusion valve V ₁ is opened.
By substituting the calculated value into the following equation, the leakage position X ₁ is calculated.
(Leakage position calculation step 1).

[0021]

[Equation 2] Next, the diffusion valve V ₁ in FIG. 1 is closed, and the diffusion valve V ₂ is opened.
F in the formula (1) in the above state is expressed as F _b, and the same applies hereinafter.
If ΔF ₁ is ΔF _1b and ΔF ₂ is ΔF _2b , the leakage position is
The following equation for obtaining X ₂ is obtained. Therefore, the diffusion valve V ₁ is closed
However, the measured value and the value obtained with the diffusion valve V ₂ open
By substituting the calculated value into the following equation, the leakage position X ₂ is calculated.
(Leakage position calculation step 2).

[0022]

[Equation 3] In the correction amount comparison calculation step, the following calculation is performed to correct the measurement value error of the flow meter. First, the flow rate at the inlet and outlet
Since F _1a , F _1b , F _2a and F _2b are measured values, they include an error. Therefore, the leakage positions X ₁ and X ₂ calculated by the equations (2) and (3) do not match the actual leakage positions of the leakage test diffusion valves V ₁ and V _{2 at} the positions L ₁ and L ₁ + L _2. . Therefore, the error of the measured value F _1a is ε _1a , and the error of the measured value F _2a is ε _2a.
Was corrected in place of the flow rates F _1a and F _{2a in} equation (2)
If the flow rates (F _1a + ε _1a ) and (F _2a + ε _2a ) are used, leakage will occur.
It can be said that the position X ₁ is equal to the position L ₁ . Also, the measured value F _1b
(3) where ε _{1b is} the error of ε _1b and ε _2b is the error of the measured value F _2b
The corrected flow rate (F _1b + ε) instead of the flow rates F _1b and F _2b of
_1b ) and (F _2b + ε _2b ), it can be said that the leakage position X ₂ is equal to the position L ₁ + L ₂ . Therefore, the following equation holds.

From the leakage position calculation step 1,

[0024]

[Equation 4] _{A 1 = F 2 c a -} (F 2a + ε 2a) B 1 = 2 · F a -F 2 c a + F 2a + ε 2a C 1 = F 1a + ε 1a -F 1 c a + F 2 c a -F 2a - from _{ε 2a D 1 = 2 · F} a + F 1a + ε 1a -F 1 c a -F 2 c a + F 2a + ε 2a Similarly leakage position calculation step 2,

[0025]

[Equation 5] A ₂ = F ₂ c _b − (F _2b + ε _2b ) B ₂ = 2 · F _b −F ₂ c _b + F _2b + ε _2b C ₂ = F _1b + ε _1b −F ₁ c _b + F ₂ c _b −F _2b − ε _2b D ₂ = 2 · F _b + F _1b + ε _1b −F ₁ c _b −F ₂ c _b + F _2b + ε _2b Then, these two equations are solved in the comparison calculation step to obtain the correction amounts ε _1a , ε _2a , ε. _1b and ε _2b are obtained.

Next, as another embodiment, a case will be described in which there are a plurality of drawing points in the middle of the pipeline, and the measurement value error of the flowmeter there is corrected at the same time. Applicable. The case where the simplest extraction point is one will be described with reference to FIG. In the figure, a drawing point 1 is installed downstream of the leakage test diffusion valves V ₁ and V ₂ and the drawing flow rate there is measured.

After the leakage position calculation step 1 and the leakage position calculation step 2 are carried out, in the same manner, the diffusion valves V ₁ and V ₂ are closed and the flow rate valve G1 at the extraction point 1 is opened, and measurement is performed there. The leakage position is calculated with the flow rate set to zero. Therefore, the radiation from the extraction point 1 is detected as a leak, and the leak position is calculated (leak position calculation step 3). Therefore, a leak position calculation formula for the extraction point position X ₃ similar to the above-mentioned leak position calculation formulas ( 2 ) and ( 3 ) is obtained, and correction amounts ε ₁ and ε are obtained by solving these 3 formulas simultaneously. ₂ and ε ₃ (correction amount of pull-out point flowmeter) are obtained.

It should be noted here that the above-mentioned leakage position used in the leakage position calculation step 1 and the leakage position calculation step 2
Equation (1) is to be determined in consideration of the pull-out amount measured by pulling vent point. Therefore, the leak position calculation formula
Equation (1) is a modified equation such as the following equation.

[0029]

[Equation 6] F _{1 2 3} , F ₄ : Numerically calculated interval (L ₁ + L ₂ +
L ₃ ) and L ₄ numerically calculated average flow rate Note that the leak position calculation formula in leak position calculation step 1
(2) Leakage position calculation formula in leakage position calculation step 2
Since the modification regarding (3) is the same, the description is omitted.

FIG. 3 shows a system configuration in the case where there are a plurality of (N) extraction points and the flow meter error at each extraction point is corrected.
Shown in. In the figure, T ₁ and T ₂ are the fluid temperatures at the inlet and outlet,
CP is a computer for the system. Leakage position calculation step 1 in consideration of the amount of withdrawal measured at the withdrawal point,
After performing the leakage position calculation step 2, the diffusion valve V ₁ and the diffusion valve V ₂ are closed, and the leakage flow position is obtained at each extraction point by sequentially opening the valves and setting the measured flow rate to zero. Therefore, since a total of N + 2 equations of the correction amounts of the flow rates F ₁ and F _{2 at} the inlet and the outlet and the correction amounts of the N drawing flowmeters are established, all the correction amounts are determined by calculation. However, since the calculation formula becomes complicated, optimization is performed by the linear programming method and each correction amount is obtained. The objective function to be minimized at this time is as follows.

[0031]

## EQU6 ## H = Σ (Xi-Li) ² Xi: Leakage position Li obtained by assuming leakage at the extraction point Gi: The position Σ of the extraction point Gi: the sum of 1 to N.

The graph of FIG. 4 shows changes in the correction amounts of the inlet and outlet flow meters thus obtained and the objective function.

[0033]

As described above, according to the present invention, a leak test diffusion valve is provided in a pipeline that implements a leak detection method by transient response calculation, and a pseudo test is performed as many times as the number of flow meters to be corrected. Since the correction amount of the flow meter can be determined by performing the leak test of, there are the following effects.

(1) It is not necessary to perform correction using a reference flow meter for each flow meter as in the conventional case.

(2) There is no need for a place for installing a pipe prober or a reference flow meter, equipment therefor, and management.

(3) In a pipeline adopting the leak position detection method by transient response calculation, at most two diffusion valves are installed, or if there is a diffusion tower, it is used to modify the calculation software of the computer. It can be implemented.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for carrying out the present invention with the simplest pipeline without a drawing point in the middle.

FIG. 2 is an explanatory diagram for carrying out the present invention in a pipeline having one drawing point in the middle.

FIG. 3 is a conceptual diagram of a measurement system and a calculation system when the present invention is carried out in a pipeline having N drawing points on the way.

FIG. 4 is a graph showing a correction amount and an objective function obtained by a linear programming method.

FIG. 5 is an explanatory diagram showing a correction method by a passage volume measuring method using a pipe prober.

FIG. 6 is an explanatory diagram showing a correction method using a reference flow meter.

[Explanation of symbols]

1 Inlet 2 Outlet X ₁ Position of diffusion valve V ₁ X ₂ Position of diffusion valve V ₂ X ₃ Position of extraction point 1

Claims (2)

(57) [Claims] 1. A pipeline in the middle of which a pressure and a flow rate at both ends of the pipeline are periodically measured, and a transient response of the pressure and the flow rate in the pipeline is calculated in real time to detect a leak and calculate a leak position. At different positions of the leakage valve V ₁ and the leakage valve V ₁ for leakage test
₂ is installed, the diffusion valve V ₂ is closed, the diffusion valve V ₁ is opened to perform a leakage position calculation, and the diffusion valve V ₁ is closed and the diffusion valve V ₂ is opened to a leakage position. Based on the comparison between the leakage detection position and the deviation of the diffusion valve V _{1 in} the step 1 and the deviation of the leakage detection position and the diffusion valve V _{2 in} the step 2, the _two ends of the pipeline are calculated. A comparison calculation process to calculate the flow rate error of, and an online correction method for the flowmeters at both ends of the line consisting of. 2. The pressure at both ends of the pipeline, the flow rate, and the withdrawal flow rate at a plurality of withdrawal points provided in the pipeline are periodically measured, and the transient response of the pressure and flow rate in the pipeline is calculated in real time. The diffusion valve V ₁ and the diffusion valve V ₁ for the leakage test are located at different positions in the pipeline of the pipeline for detecting the leakage and calculating the leakage position.
₂ is installed, the diffusion valve V ₂ is closed, the diffusion valve V ₁ is opened to perform a leakage position calculation, and the diffusion valve V ₁ is closed and the diffusion valve V ₂ is opened to a leakage position. Leak detection in step 1 and step 2 in which calculation is performed, step 3 in which the diffusion valve V ₁ and the diffusion valve V ₂ are closed, and the leak position is calculated by sequentially setting the measured flow rate of the withdrawal flow valve in the middle of the pipeline to zero. Of the position of the diffusion valve V _1, the position of the leakage detection position of step 2 and the position of the diffusion valve V ₂ , and the position of the leakage detection position of step 3 and the position of the extraction flow valve where the measured flow rate is zero. A comparison calculation process that calculates the flowmeter error at both ends of the pipeline and the drawing flowmeter error in the middle of the pipeline based on the deviation comparison. Online correction method for the withdrawal flow meter.