JPS6251411B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time calibrating device for a clock device for a leak detection system in a fluid transport path such as a pipeline as a means of long-distance mass transportation of petroleum products.

Pipelines are an excellent means of transporting petroleum products over long distances in large quantities, both economically and in terms of safety, but they are prone to leakage due to unforeseen accidents (mainly caused by external factors such as civil engineering work) It is necessary to promptly detect this when it occurs. Although various systems for such leak detection have already been developed, this invention relates to a leak detection system using a pressure wave method, so this system will be described below.

A leak at any point in the pipeline causes a sudden drop in pressure that is proportional to the amount of the leak. This wave of sudden, unsteady pressure drop then propagates at a certain speed along the pipeline upward and downstream from the leak point.

This method detects the pressure waves to find the occurrence and location of leaks. Several leak detection methods can be considered by utilizing the characteristics of the pressure wave propagation phenomenon caused by this leak.
Before explaining the detection method, we will discuss the characteristics of the propagation phenomenon.

(b) In a known pipeline, if the physical properties of the fluid (specific weight, bulk modulus) are known, the propagation velocity of the pressure wave can be easily determined from equation (1),
In a uniform fluid, this propagation velocity is approximately constant along the pipeline.

Here, γ: Specific weight of liquid Kg/m ³ E: Young's modulus of pipe Kg/m ² K: Bulk modulus of elasticity Kg/m ² D: Pipe inner diameter m e: Pipe wall thickness m This allows pressure waves to be detected. This shows that the location of the leak can be predicted.

(b) Pressure changes caused by leaks always result in pressure drops. This means that transient phenomena caused by artificial changes in valve and pump operation cause opposite phenomena on the upstream and downstream sides (when pressure increases on one side, pressure decreases on the other side), so pressure fluctuations are caused by leakage. This shows that it is easy to determine whether or not the problem has occurred.

Leakage detection can be performed using the above features. A leakage detection method will be explained with reference to FIG.

FIG. 1 is an explanatory diagram showing the state of pressure waves propagating from a leak point in a pipeline. In the figure, it is assumed that oil is being transported by pipeline 3 from originating tank 1 to destination tank 2, and a leak has occurred at point 4. In addition, ~ represents the measurement points along the pipeline, L ₁ ~ _{L 5}
indicates the distance between the measurement points, and X is the leak point 4
indicates the distance between and the measurement point. In addition, ~ indicates the propagation order of the pressure waves, and _tA to _tF indicate the arrival time of the pressure waves at each measurement point.

Now, a method of detecting a leak location from two measurement points when the pressure wave propagation velocity a is constant over the entire length of the pipeline will be explained. The conditions for this a = constant are (a) when the same type of liquid flows in the pipeline, and (b) when the pipe and the conditions for burying the pipe are the same over the entire length of the line.

If a leak occurs between the measurement points, the pressure wave propagates to the measurement point in the following time: t _D =X/a t _E =(L ₄ -X)/a.

From these two equations, the following equation is given: X=1/2{a(t _D −t _E )+L ₄ } (2). In other words, if we calculate the difference (t _D - t _E ) between the times when pressure waves are detected at two measurement points, we get a,
Since L ₄ is known, the distance X from the measurement point to the leakage point can be found from equation (2).

In this method, the propagation velocity a must be accurately determined in advance, the pressure must be constantly measured, and pressure fluctuations must be detected. Generally, it is suitable when measuring points are provided only at both ends of a relatively short pipeline.
However, in the above method, the propagation velocity must be constant along the entire length of the line, and this method causes errors because it is common for different types of liquids to be transported or for long pipelines to have different pipe conditions. . In such cases, there are methods described below.

As shown in FIG. 1, a large number of measurement points are provided along the line 3, and the pressure is continuously measured at each point. When a leak occurs, the pressure waves propagate in the order of D, E, C, F... as shown in the figure.
The arrival time is t _D , t _E , t _C , t _F ..., so using equation (2), the leakage point is X = 1/2 {a (t _D - t _E ) + L ₄ } . On the other hand, the propagation velocity a is determined by the difference in arrival time between adjacent measurement points, so that a=(L ₃ /t _C −t _D )=(L ₅ /t _E −t _F ), so this average value a _M is _{If you use _}
Only the distance and time measurement errors between measurement points are included.

Now, I have explained in detail the principle of the leak detection system using the pressure wave method, but when using this system,
The leak location is determined by calculation from the time difference between the arrival times of the pressure waves at each measurement point. Now, if the leak detection calculation is to be performed on the pipeline entrance side, for example, if the pipeline distance is short,
The signal from the pressure wave detector installed on the pipeline outlet side is sent directly to the pipeline inlet side,
It is easy to detect the time difference between the arrival times of the pressure waves by inputting the signal to the calculator together with the signal detected by the pressure wave detector on the inlet side, and it is also possible to calculate the location of the leak from the time difference. However, when the distance of the pipeline is long, it is difficult to send the signal from the pressure wave detector at the pipeline outlet directly to the inlet side instantaneously to the extent that the transmission time can be ignored. It is necessary to read the time when the wave was detected and input that time to the calculator on the pipeline entrance side, along with the time when the pressure wave was detected on the entrance side. In this case, it goes without saying that the criteria for time measurement on the pipeline inlet and outlet sides must match.

FIG. 2 is a block diagram showing a conventional configuration example of a leakage detection system when the pipeline is long. Refer to the same figure. On the entrance side of the pipeline 3, a pressure wave detector 11, a rate of change calculation circuit 21, a time reading gate 31, a clock device 41, a buffer register 51, a signal receiver 61, a calculation circuit 71, and a display device 81 are provided. , a pressure wave detector 12, a rate of change calculation circuit 22, and a time reading gate 3 are installed on the exit side.
2. A clock device 42, a buffer register 52, and a signal transmitter 62 are provided, and the signal transmitter 62 and receiver 61 are connected by a communication line.

The pressure wave detectors 11 and 12 are devices that detect pressure waves in the pipeline 3 and output signals.

The rate of change calculation circuits 21 and 22 output read gate on signals when the rate of change of the output signal (representing pressure) from the pressure wave detector is equal to or greater than a certain set value. The time reading gates 31 and 32 are reading gates.
When receiving the ON signal, the time of the clock devices 41 and 42 is outputted to the buffer registers 51 and 52. The clock devices 41 and 42 have a built-in time calibration circuit. Buffer registers 51 and 52 temporarily store time. The signal receiver 61 is a signal transmitter 62
receives the transmission of the time temporarily stored in the buffer register 52. Arithmetic circuit 71
The times temporarily stored in the buffer registers 51 and 62 are inputted, and the leak location is calculated by calculating the above equation (2) and displayed on the display device 81.

In order for such a leakage detection system to function properly, as described above, the times of the clock devices 41 and 42 must be correctly synchronized. Therefore,
It is necessary to calibrate the clock devices on the entrance and exit sides according to Japan Standard Time (NHK time signal, for example). In this case, there is a drawback that different people calibrate the time on the clock device at the pipeline inlet and outlet, making it difficult to ensure the accuracy of the time calibration. By the way, if the pressure propagation speed in the pipeline is 1000m/s, if there is an error of 200ms in time calibration, the leakage detection error will be
It can reach up to 200m. In order to avoid this, if you install an automatic time calibration device to ensure accuracy (for example, a high-performance device like that used at broadcasting stations),
This is a very expensive device. Inexpensive time calibration devices are not suitable for use in leak detection systems because they can only be expected to be accurate to the second level at most.

The present invention was made to solve the problems in the prior art as described above, and an object of the present invention is to provide a time calibration device suitable for use in a clock device for a pipeline leak detection system. The aim is to provide this at a relatively low cost.

The gist of the configuration of the present invention is to provide a clock device that includes a numerical value setter for time setting, a digital clock that is set by inputting the numerical value set in the time setting device via a gate circuit, and When signal detection devices that output an output and turn on the gate circuit when detected are provided at both ends of the pipeline, and a signal generation means is provided in the signal line connecting both signal detection devices, and time calibration is required. , the signal generation means generates a signal, and each of the detection devices simultaneously detects the signal, thereby turning on the gate circuit in each of the clock devices and inputting and setting a set numerical value to the digital clock. The point is in the composition.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 4 is a detailed block diagram showing the configuration of the timepiece devices 9, 9a in FIG.

In FIG. 3, a clock device 9 and a signal disconnection detection device 6 are arranged on the pipeline inlet side, and a clock device 9a and a signal disconnection detection device 6a are arranged on the exit side, respectively, and between the two detection devices 6, 6a. A signal generator 8 and a time calibration command switch 7 are connected to the line 5.
are connected as shown. Here, the signal disconnection detection devices 6 and 6a detect contacts 10 and 6a when the signal current flowing through the line 5 drops below a certain set value.
This is a device that generates a contact output by closing 10a. The time calibration command switch 7 is a switch that opens the circuit of the communication line 5 when time calibration of the timepiece devices 9, 9a is performed. In the signal generating device 8, when the switch 7 is closed in the circuit of the communication line 5, the signal disconnection detecting devices 6, 6a are connected to the contacts 10, 10a.
This is a device that supplies a signal current of sufficient magnitude to prevent the contact from closing and producing a contact output.

Please refer to FIG. The clock devices 9 and 9a include a time calibration start switch 91 and a numerical value setter 9 for time setting.
2, a gate circuit 93, an oscillator 94, a digital clock 95, and an output control section 96. When the switch 91 attempts to calibrate the time,
This is a switch that must be turned on in advance. Setting device 92
is a numerical value setter in which the time to be set in the digital clock 95 is input in advance as a numerical value, and is set, for example, as 11:23:15. The gate circuit 93 is a gate circuit that opens when both the output contact 10 and the switch 91 are on, and inputs the setting value set in the setting device 92 to the digital clock 95. The oscillator 94 sends a constant periodic pulse (for example, a 1 ms pulse) to the digital clock 95. The digital clock 95 receives the time set from the time setting numerical value setter 92 via the gate circuit 93 (units of seconds or less are regarded as zero. For example, 11:23
If it is set to 15 seconds, it will be considered as 11:23:15:0000 milliseconds. ), a pulse from the oscillator 94 is added to convert it into time and output. Output control section 96
is a circuit that outputs the time of the digital clock 95 to the outside.

Next, the operation will be explained with reference to FIGS. 3 and 4. With the device according to the invention, the clock device 9,9
When performing the time calibration of a, do the following. The time setting numerical value setters 92 of each clock device installed on the pipeline inlet and outlet sides are respectively set to the desired time. This does not necessarily have to be set according to Japan Standard Time, and may be set to any arbitrary time, for example, 00:00:00. Note that the set numerical values must be the same on the pipeline inlet and outlet sides, but the timing of setting may be arbitrary. Next, the time calibration start switch 9 is activated on each of the pipeline inlet and outlet sides.
Close 1. When the above conditions are met, open the time calibration command switch 7 and disconnect the line 5.
Signal disconnection detection devices 6, 6 on the entrance side and exit side, respectively
a operates to close the contacts 10 and 10a and send the contact output to the clock devices 9 and 9a. Therefore, in the clock devices 9 and 9a, the gate circuit 93 is turned on, the set value of the time setting numerical value setter 92 is set in the digital clock 95, and the clock devices 9 and 9a each start time measurement from the same set time. . In addition, the time calibration start switch 91 is left open when not performing time calibration, and is used to prevent incorrect settings when output is accidentally generated from the contacts 10 and 10a due to, for example, a failure of the signal generator 8 or a disconnection of the line 5. This can be prevented.

Note that the time calibration start switch 91 may be omitted if the signal generator 8 and the line 5 are highly reliable and there is no risk of erroneous setting input. Further, the time calibration command switch 7 and the signal generator 8 may be installed at any location. Further, the time setting numerical value setter 92 may be omitted by using numerical values stored and set in advance by software in the arithmetic device. The signal generated by the signal generator 8 may be in any form, such as a direct current (voltage), an alternating current (voltage), or a high-frequency alternating current signal, and the form does not matter. Therefore, the signal disconnection detection devices 6, 6a may be of any appropriate form as long as they detect a signal disconnection, and for example, an undercurrent relay or the like may be used. Further, here, the signal interruption is detected and used as a trigger signal for the clock installations 9, 9a, but the reverse may be used. That is, the presence of a signal may be detected and used as a trigger signal instead of a signal disconnection.

As described above, the present invention has the advantage that it is possible to provide a device capable of simultaneously calibrating time without time lag in multiple clock devices for a fluid leakage detection system at a relatively low cost. There is.

This invention is applied to a leak detection system using the pressure wave method for oil pipelines, but in addition,
Of course, the present invention is applicable to any system including a plurality of clock devices to be calibrated at the same time.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the state of pressure waves propagating from a leak point in a pipeline, and Figure 2 is an explanatory diagram showing the state of pressure waves propagating from a leak point in a pipeline.
FIG. 3 is a block diagram showing a conventional configuration example of a leakage detection system; FIG. 3 is a block diagram showing a configuration of an embodiment of the present invention; FIG. 4 is a detailed block diagram showing the configuration of a clock device in FIG. 3; It is. Code explanation, 1... Departing tank, 2... Arriving tank,
3... Pipeline, 4... Leak point, 5... Communication line, 6... Signal disconnection detection device, 7... Time calibration command switch, 8... Signal generator, 9... Clock device, 10... Output contact, 11, 12... Pressure wave detector, 21, 22... Rate of change calculator, 31, 3
2... Time reading gate, 41, 42... Clock device, 51, 52... Buffer register, 61...
Signal receiver, 62...Signal transmitter, 71...Arithmetic circuit, 81...Display device, 91...Time calibration start switch, 92...Numeric value setter for time setting, 93
... Gate circuit, 94 ... Oscillator, 95 ... Digital clock, 96 ... Output control section.

Claims (1)

[Claims] 1. Receive propagating waves of fluid pressure changes that occur when a leak occurs in the middle of a fluid transport channel at two points located across the leak point of the transport channel,
A time calibration device for a clock device provided at each of the two points for use in a leakage detection system that detects a leakage location from the difference in reception times, the device including a numerical value setting device for time setting, and a numerical value set in the setting device. In addition to a clock device having a digital clock which is input and set via a gate circuit, a signal detection device is provided at each of the two points to generate an output and turn on the gate circuit when a signal is detected. In addition, a signal generating means is provided in a signal line connecting both signal detecting devices, and when time calibration is desired, the signal generating means generates a signal, and each of the detecting devices simultaneously detects the signal, so that the above-mentioned A time calibrating device for a clock device for a fluid transport channel leak detection system, characterized in that the gate circuit in each clock device is turned on to set a set numerical value in a digital clock.