JPH0321841A - Gas leakage estimating device - Google Patents

Abstract

PURPOSE:To estimate a gas leakage per unit time speedily with high accuracy by calculating a leak area according to data in two storage means and current wind direction and wind velocity data and finding a time-averaged density gradient. CONSTITUTION:A coordinate data storage circuit 13 is stored with coordinate data on gas detectors S(S1 - S15) arranged in a plant P. Further, a wind speed and wind direction history storage circuit 11 is stored with the mean wind direction and wind velocity based upon data of an anemometer K in the plane P which are obtained for a longer than a period required for gas to reach detectors S in a no-wind state, and the data are updated in order. Then an arithmetic unit 14 reads data out of the circuits 13 and 14 and calculates a leak area when at least one of the detectors S detects gas exceeding reference density. Further, the time-averaged density gradient is calculated from density signals from the respective detectors S and the gas leakage is calculated from the gradient and leak area.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention is directed to a technique for estimating gas leakage based on signals from a plurality of gas detectors. (Prior art) For example, in a chemical plant where many gas sources are scattered over a wide area, multiple gas detectors are installed at key points to detect the three points where the gas J degree signal is highest in the event of a gas leak. However, a method has been proposed in which the gas leakage area is estimated by proportional calculation based on each detected concentration and the position where the gas detector is installed (Japanese Patent Laid-Open No. 155932/1983). (
Issues to be Solved) It is clear that the location of gas leaks can be calculated theoretically using this method, but when used in extremely large areas such as chemical plants, it is difficult to use gas detectors. Normal 2
Because they are placed at intervals of 0 meters or more and are scattered with various large equipment, there is a problem in that it is impossible to accurately measure the amount of leakage due to the influence of complicated air currents.
The present invention was made in view of these problems, and its purpose is to measure the amount of gas leakage that can estimate the amount of gas leakage as quickly as possible in a wide area regardless of wind direction or wind speed. The goal is to provide equipment. (Means for Solving the Problems) In order to solve such problems, the present invention provides a first storage means that stores coordinate data of a plurality of gas detectors installed in a plant, and a first storage means that stores coordinate data of a plurality of gas detectors installed in a plant. and a second storage means for storing signals from the wind direction and wind speed measuring means in the plant for a longer period of time than it takes for gas to reach the gas detector in a windless state; means for calculating a leakage area by reading data from the first storage means and the second storage means when the above gases are detected; and calculating an average concentration gradient based on concentration signals from each gas detector. The apparatus is equipped with a time-average concentration gradient calculation means and a means for calculating gas leakage N from the time-average concentration gradient and the calculated leakage area. (Function) At the stage when a gas concentration signal is output from one of the gas detectors, the leak area is calculated based on the second storage means and the current wind direction and wind speed data, the time average concentration gradient is obtained, and this and the leak area are calculated. Calculate the leakage jl based on the area of . (Example) The details of the present invention will be explained below based on an illustrated example. FIG. 1 shows an embodiment of the present invention, and reference numeral 1 in the figure is a gas leakage measuring device which is a feature of the present invention.
When the FIT equipment is placed on the site of the plant P, which is located on the site, there are a plurality of gas detectors S1 arranged at ground heights corresponding to the specific gravity of the gas.
Signals from S2, S3, etc.) are input via the scanner 2, signals from the anemometer K are input manually, and the leakage amount and leakage area are output to the display 3. Reference numeral 11 in the figure is a wind direction/wind speed history memory circuit that stores the average wind direction and average wind speed for a certain period of time, for example, 10 seconds, and as shown in Figure 2, it diffuses from at least the leak area to the gas detector S in a calm state. A memory that can store data for the longest time required for gas to diffuse from the intersection of the three gas detectors surrounding the point of interest, or the farthest gas detector from the intersection of the three gas detectors. Good luck! 1, and is configured to store wind direction and wind speed along with time tn while updating the stored data, and output the stored contents in response to a command from an arithmetic unit 14, which will be described later.
Reference numeral 12 is a wind direction and wind speed correction circuit, which previously investigated the wind direction and wind speed in the vicinity where each gas detector S1, S2, S3, etc. is installed with respect to a standard direction, for example, northward wind. The data is stored as shown in FIG.
It is configured to output based on the command from 4. 13 is a coordinate data storage circuit for each gas detector S1,
S2, S3...Coordinate data where Sn is located (
Xi, Y I) (X2, Y2) (X3, Y3) ...
- Store (Xn, Yn) and layout diagrams of plant equipment as needed. 14 is the above-mentioned arithmetic unit, which consists of a microcomputer having a CPU 14a, an M14b, and a RAM 14c, and is connected to each gas detector S1.
, S2, S3, . It is designed to calculate the amount of leakage based on the results. Reference numeral 15 in the figure is an external storage device consisting of a magnetic disk mounted, etc., which includes each gas detector S1, S2, S3, etc., a wind direction/wind speed history circuit 11, a wind direction/wind speed correction circuit 12, and a wind direction/anemometer K. It records the signals from and the estimation calculation process. Next, the operation of the device configured in this way will be explained based on the flowchart shown in Fig. 4.The time-average data of the wind direction and wind speed detected by the wind direction and speed meter K is stored in the wind direction and wind speed history along with the elapsed time. Data that is stored in the circuit 11 and a certain period of time has elapsed since being stored is sequentially updated to the latest data.

If gas leaks from a certain facility under such conditions, the leaked gas will be affected by the surrounding airflow and dissipate. [When the influence of wind is greater than the gas diffusion speed] Set @L
When the gas leaking from the tube (FIG. 5) reaches the first gas detector Sa located in the downstream direction, the gas detector Sa outputs a signal proportional to the gas concentration. As a result, the arithmetic unit 14 calculates the coordinates (
Xa, V'a) are read out from the coordinate data storage circuit 12, and at the same time, based on the data of the wind direction and speed anemometer K and the wind direction and wind speed history storage circuit 11, it is determined whether there is a wind influence. In this case, since the influence of the wind cannot be ignored, the wind direction and wind speed history memory circuit 11 is accessed, and past wind direction and wind speed data that have not been stored there are sequentially read out. At this time, a signal is output (if the position of the gas detector Sa is in a place where airflow is easily disturbed due to the influence of equipment, etc., the signal from the wind direction and wind speed history memory circuit 11 is corrected by the correction circuit 12. Then, the air flow paths P1, P2, P3, etc. from the point of leak occurrence to the gas detector Sa are calculated. Pressure marks (Xb, Yb) (X
c, Yc) (Xd.Yd) 8 coordinate data storage times wA13
The coordinates of a circle M having these coordinates on its circumference are calculated, and this circle M is displayed on the display 3 as a leakage area. This (from this, the second and third positions located outside this circle M)
Not only can the leakage area M be immediately notified to the operator without waiting for the gas detection signal from the first gas detector, but also the conventional method is based only on the wind at the time when the signal is output from the first gas detector. This means that the leakage area can be estimated with much higher accuracy than the previous estimation method. When the leak gas diffusion area expands over time and a signal is output from the second gas detector, the air flow path up to the detection point is calculated based on the same process as described above, and this path and the first Estimating the leakage area is performed while taking into account the coordinates (Xa.Ya) of the gas detector Sa that detected the gas. In other words, the leaked gas air mass spreads over time due to diffusion, and the area of the estimation target area increases, resulting in a lack of accuracy in estimating the leakage area. Therefore, the coordinates of the gas detector Sa that first detected the gas (X a
．． While respecting the first estimation result based on Y a), the second, third, etc. detectors S, Sc, etc.
... is used as supplementary data to perform estimation calculations.

[When the influence of wind can be ignored] When the gas from the leak point (Fig. 6) diffuses and reaches the first gas detector Sa, a signal proportional to the gas concentration is output from the gas detector Sa. As a result, the W controller 14 reads the coordinates (Xa.Ya) of the detector Sa that outputs the signal from the coordinate data storage circuit 12, and at the same time, the wind direction and speed meter K
, and the data of the wind direction/wind speed history storage circuit 11 {based on which the past and present wind shadows g are determined. In this case, since the wind speed signal from the anemometer K and the wind speed in the wind direction and speed history storage circuit 11 are extremely small, it is determined that there is no influence from the wind. Therefore, the leaked gas does not flow into the airflow, but spreads in all directions around the leak area L, and reaches the gas detector Sa closest to the leak area L (Fig. 6). The arithmetic unit 1fl4 has four gas detectors Sb. Sc%Sd, Se! Select C and its coordinates (
Xb, Yb) (Xc, Yc)...(Xe, Ye)7
: Read out. Next, the coordinates of an area M' passing approximately at the midpoint between the detector Sa that detected the gas and the other detectors Sb, Sc, . . . Se are calculated, and this area M' is displayed on the display 3 as a leakage area. indicate. This allows the leak area to be displayed without waiting for signals from the second and third gas detectors. If the leakage scum spreads over time and other gas detectors Sd, Se... sequentially output detection signals,
Read the coordinates of the gas detector outputting the highest concentration signal, and display the area centered on these coordinates and passing through the midpoints of the nearest other detectors surrounding it. In this way, by estimating the leakage area with the wind speed at zero, it is possible to perform highly accurate estimation by eliminating errors caused by large fluctuations in wind direction data that tend to occur especially when weak winds are blowing. Can be done. [Calculation of S leakage amount] In the process of estimating the leakage area through the process described above, when the leakage progresses and the gas reaches multiple gas detectors, instantaneous concentration changes are calculated based on the gas concentration signal. Calculate the concentration gradient at the coordinate point, that is, the time-averaged concentration gradient, based on the value that is averaged over time. In other words, by using Sakagami's diffusion equation or Sutton's diffusion equation, which describes the process by which a gas nodule existing in the atmosphere diffuses,
For convenience, a method can be used in which the concentration at two concentration detection points and the distance M between the detection points are used as parameters, and the gas concentration at an arbitrary position between the two points is proportionally divided by the Nth root of the distance. Among the gases at arbitrary points obtained in this way, regions Z1 and z2 are calculated and displayed at a constant concentration level, for example, in steps of 100 ppm (Fig. 7), and at a certain concentration level, for example, 100 ppm. , calculate the area of the area surrounded by the J4 parallel and estimate the amount of leakage per unit time. [Experimental example] A plurality of gas detectors are placed in the field at intervals, and the test is carried out under certain conditions, for example, at an average wind speed of 0. When gas is discharged at 100 liters/minute under conditions that can be considered as virtually no wind at 1 meter/second or less, the area SO (square meters) surrounded by the 100 ppm isoconcentration curve is calculated, and the relationship between this area and the amount of leakage is calculated. Find the coefficient Q=F (So). Next, the outflow of gas per unit time! (L/min), calculate the area S surrounded by the 1 ooppm isoconcentration curve, and calculate the leakage t as Q=S/SOx 100 (
When the amount of gas leakage was estimated by changing the amount of gas ejected under conditions that can be considered as windless (liters per minute), the results shown in H in Table 1 were obtained. From this, it was found that the above estimation formula can calculate the leakage amount relatively accurately in no-wind conditions (as shown in Table 1 above). On the other hand, when the wind speed increases and becomes impossible to ignore, the peripheral part of the gas mass tends to be blown away by a single piece of wind.
Relational expression Q=S/SO×100×(v+
1) (liter/min) As shown in II to ■ of Table 1, (
We were able to estimate this within the range of 1/2 to 2 times. In this example, the wind speed v is used as is, but the estimation accuracy can be further improved by multiplying it by (aV+1) using a correction coefficient aa depending on the equipment layout, climate, etc. can.

(Effects) As described above, according to the present invention, the first storage means stores the coordinate data of a plurality of gas detectors installed in the plant, and the first storage means stores the coordinate data of a plurality of gas detectors installed in the plant. a second storage means for storing the signal from the wind direction and speed measuring means in the plant for a longer period than it takes for the gas to reach the gas detector; and when at least one of the gas detectors detects a gas having a reference concentration or higher, means for reading data from the first storage means and the second storage means to calculate a leakage area; and average concentration gradient calculation means for calculating a time-average concentration gradient based on concentration signals from each gas detector; Since a means for calculating the gas leakage N from the concentration gradient and the calculated leakage area is provided, the gas leakage ji per unit time can be estimated quickly and with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus showing an embodiment of the present invention;
3 is a schematic diagram showing the data structure of a storage circuit and a correction circuit in the above device, respectively, and FIGS. 4, 5, 6, and 7 are a flowchart and an explanatory diagram showing the operation of the above device. P...Brushite Sa, Sb, Sc...Gas detector K...Wind direction and speed meter

Claims (2)

[Claims] (1) A first storage means storing coordinate data of a plurality of gas detectors installed in the plant, and sequentially updating the data,
a second storage means for storing signals from the wind direction and speed measuring means in the plant for a longer period than required for gas to reach the gas detector in a windless state; and at least one of the gas detectors detects gas having a reference concentration or higher. means for calculating a leakage area by reading data from the first storage means and the second storage means, and a time-average concentration gradient for calculating a time-average concentration gradient based on concentration signals from each gas detector. A gas leakage amount estimating device comprising a calculation means and a means for calculating a gas leakage amount from the time average concentration gradient and the calculated leakage area. (2) A first storage means storing coordinate data of a plurality of gas detectors installed in the plant, and sequentially updating the data,
a second storage means for storing signals from the wind direction and speed measuring means in the plant for a longer period than required for gas to reach the gas detector in a windless state; and at least one of the gas detectors detects gas having a reference concentration or higher. means for calculating a leakage area by reading data from the first storage means and the second storage means, and a time-average concentration gradient for calculating a time-average concentration gradient based on concentration signals from each gas detector. a calculation means, a means for calculating a gas leakage amount from the average concentration gradient and the calculated leakage area, and a means for multiplying the calculated leakage amount by (aV+1) (where a is a constant) when the wind speed is V. Gas leakage amount estimation device.