JPH058780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for detecting pitting corrosion in a pipeline from the inside of a pipe using ultrasonic waves.

[Prior art]

Conventionally, as a method for detecting pitting corrosion in pipelines installed underground or on the seabed, a capsule equipped with a detection device (hereinafter referred to as an inspection pig according to common usage) is inserted into the pipeline. The test pig is transported by fluid flowing through the pipeline, and along the way, the on-board inspection device detects pitting corrosion.The test pig is taken out at the exit of the pipeline and the data is reproduced to obtain pitting corrosion information. are known (e.g. Pipes & Pipeline
International Aspects of the British Gas
Online Inspection Service). In addition, the detector used is generally one using the leakage magnetic flux method as described in the above-mentioned literature. As described in ``Pipe Exploration Device'', ultrasonic thickness gauges, ultrasonic distance meters, etc. are used.

FIG. 5 is a block diagram of a conventional pitting corrosion detection device. In the figure, 1 is a probe that is attached to a test pig and emits and receives ultrasonic waves, 2 is a partial cross section of the tube body, 3 is a pulser that applies a pulsed high voltage to the probe, and 4 is a probe for the probe. 5 is a circuit that measures the time between the T pulse that drives the pulser 3 and the S echo received by the probe 1; 6 is the probe 1; A circuit for measuring the time between the S echo and the B echo received at 7 is a fluid filled in the pipeline pipe.

A conventional pitting corrosion inspection device is configured as described above.
Normally, the waveform obtained at the output side of the amplifier 4 is
As shown in the figure, the waveform is generally called A scope, and the T pulse is a pulse voltage applied to the probe 1 by the pulser 3, and the S echo is reflected from the surface of the tube body 2 and returns to the probe. The ultrasonic wave that reached the probe 1 is transmitted to the probe 1, and the B echo is the ultrasonic wave that is reflected on the outer peripheral surface of the tube body 2 and reaches the probe 1 again.
This is a pulse wave that is detected and converted into an electrical signal by

Now, the distance between the probe 1 and the surface of the tube 2 is d, the thickness of the tube 2 is t, the time between the T pulse and the S echo is T _TS , and the time between the S echo and the B echo is T TS . The time between them is _TSB , the sound velocity in the liquid 7 _{is VL} , and the tube body 2 is
Letting the sound speed inside be V _S , d=T _TS · V _L /2 ... [1] t = T _SB · V _S /2 ... [2], and d and t can be obtained, respectively.

Here, when pitting corrosion occurs on the tube body 2, if the pitting corrosion occurs on the inner peripheral surface, d and t will change, and if it occurs on the outer peripheral surface, only t will change, so depending on the degree of change. The location and depth of pitting corrosion can be measured using The same applies to abnormal parts such as scratches or irregularities.

[Problem that the invention seeks to solve]

In the case of conventional pitting corrosion inspection equipment as mentioned above,
The diameter of the pipeline to be inspected can reach up to 1200A, and on the other hand, the range that can be inspected with one probe is usually about 20mmφ at most, so the entire circumference of the 1200A pipeline can be covered. If you want to explore, there are over 180 ultrasonic thickness gauges,
It would be necessary to equip the pig with an ultrasonic range finder, which was not only a cost issue, but also a problem that was simply not possible considering that a large number of such detection devices would be mounted on the pig and travel within the pipe.

[Means for solving problems]

The piping abnormality detecting device according to the present invention is a piping abnormality detecting device that is housed in a capsule and travels within the pipeline to detect abnormalities in the pipeline. A plurality of pulsars are connected to a plurality of probes that emit signals, receive their reflected waves, and output them as echo signals, and drive the probes of selected channels. The time for the sound wave to travel back and forth between the pulsar selection circuit that sequentially selects and outputs a pulsar drive signal to drive the pulsar, and the probe and the inner peripheral surface of the pipeline in steady state is τ ₁ , and Assuming the time τ ₂ for the sound wave to travel back and forth between the probe and the outer circumferential surface of the pipeline, the difference in time for the selection signal that drives the pulser corresponding to each probe to travel back and forth through the pipeline (τ ₂ − _{τ 1} ) is _a control signal for sequentially outputting to _the pulsar selection circuit at time _intervals of , a multiplexer that outputs an echo signal from the probe based on the time (τ ₂ − τ ₁ ) of the control signal from the timing controller, and a signal between the selection signal and the echo signal input from the multiplexer. and time measuring means for measuring the time.

In addition, multiple probes are divided into predetermined groups, and when the probes in that group are driven, the probes in each group are separated so that they do not interfere with the probes in other groups. This is the arrangement.

[Operation] In the present invention, when the capsule is housed in a pipeline and travels inside the pipeline, the output timing of the selection signal of the pulsar that drives the plurality of probes arranged around the outer periphery of the capsule is adjusted in a normal state. The time difference between the time τ ₁ for the sound wave to travel back and forth between the probe and the inner surface of the pipeline and the time τ ₂ for the sound wave to travel back and forth between the probe and the outer surface of the pipeline (τ ₂ −τ ₁ )
The pulsers are sequentially outputted to the pulser selection circuit at time intervals of , and the pulsers are sequentially driven to drive the corresponding probes.

Then, the time τ ₁ from the output timing of the selection signal
After the lapse of time (τ ₂ −τ ₁ ), a control signal for inputting the echo signal from the corresponding probe is output to the multiplexer.

The multiplexer then adjusts the control signal time (τ ₂
-τ ₁ ), the echo signal from the probe is output to the time measuring means to measure the time between the selection signal and the echo signal.

〔Example〕

FIG. 1 is a block diagram showing a pitting corrosion detection device according to an embodiment of the present invention. In the figure, 1 to 6
is the same as the conventional device described above, but in this embodiment, n probes 1 and n pulsers 3 are each prepared. 7 is a pulser selection circuit, 8 is a multiplexer, and 9 is a timing control circuit, and the plurality of probes 1 and pulsers 3 are connected to a set of component circuits 4 to 9. Further, FIG. 2 shows an example of a time chart of the operation of the pitting corrosion detection device configured as described above. In the figure, ()-pulsar output is the voltage pulse output from the first channel pulser ₃₁ to the probe ₁₁ , and ()-probe output is the S, B echo output from the probe ₁₁ . and a T pulser from pulser 3 ₁ , ( ) - the multiplexer indicates that the input of multiplexer 8 is assigned to the first channel when this level is on. The same applies to the second, third to nth channels.

In the pitting corrosion detection device configured as described above, the input terminal of the amplifier 4 is connected to the probe ₁ of the first channel via the multiplexer 8 from the initial state to τ. and from τ
For the period up to 2τ, use the second channel probe 1 ₂ ,
~3τ, to the third channel probe ₁₃ ,
Thereafter, connections are sequentially made in the same manner up to n channels.
Then, the timing controller 9 first switches the multiplexer 8 and simultaneously the pulser selection circuit 7 to the first channel, and then sends a pulser drive signal after a minute time a, and the pulser ₃₁ of the first channel is driven and searched. Ultrasonic waves are emitted from _the probe 1 ₁ , and due to their reflection, T, S,
A pulse wave voltage corresponding to the B echo is generated and sent to the amplifier 4 via the multiplexer 8, the time between the T pulse and the S echo is measured in the circuit 5 as in the conventional case, and the time between the T pulse and the S echo is measured in the circuit 6. Measure the time between the echo and the B echo. Next, when the time τ has elapsed, the timing control circuit 9 switches the multiplexer 8 and the pulser selection circuit 7 to the second channel, and after a minute time a, sends the pulser drive signal to the pulser 3 ₂ , and the pulse from the probe 1 ₂ The wave voltage is input to the amplifier 4. Thereafter, the channels are sequentially switched to the third to nth channels every time τ elapses.

This time interval τ may be determined by considering the maximum time required for measurement. That is, if the maximum possible distance between the probe and the inner peripheral surface of the tube is dmax, and the maximum thickness of the tube is _tnax , then B
The time T _nax until the echo is received is T _nax = 2d _nax / V _L + 2t _nax / V _S ... [3], so τ = T _nax + α = 2d _nax / V _L + 2t _nax / V _S +α...[4] However, α may be a constant with a margin time determined by the measurement circuit. Although FIG. 2 shows an example in which three sets of probes 1 and three sets of pulsers 3 are arranged, the same operation can be performed even when an n-channel is provided.

Next, FIG. 3 shows the configuration of a pitting corrosion inspection apparatus configured with such a circuit. In the figure, 10 is an outer shell of an inspection pig that houses a measuring instrument inside and travels inside the pipe, and 11 is a cup made of flexible urethane rubber that supports the outer shell 10 and receives the propulsive force from the fluid. etc. is formed. A large number of probes 1 are disposed on the rear circumferential surface of the outer shell 10, facing the inner circumferential surface of the tube body 2.
are arranged, and the same number of pulsers 3 as the probes 1 and a set of measuring circuits 12, 4 to 9 are housed inside, and furthermore, a data recording device 13 consisting of a tape recorder etc., a battery 14, etc. are housed. .

For example, if a 1200A pipeline is to be inspected at a pitch of 15mm in the circumferential direction, 256 probes 1 and pulsars 3 are arranged, and 64 probes 1 and pulsars 3 are switched by one set of measurement circuit. In the case of scanning using the same method, four sets of measuring circuits 12 are installed. Here, if τ=250μs, each measurement circuit 1
2 completes measurement of all 64 channels in 250μs
×64=16mS, and the running speed of inspection pig 10 is
If the speed is 1m/S, longitudinal inspection can be performed at a pitch of about 16mm.

However, in actual pipelines, there are unevenness in the pipe, and in order to avoid this, the distance d between the probe 1 and the inner circumferential surface of the pipe must be set to d _nax = 150.
mm, and the running speed of the inspection pig needs to be about 3 m/s, and if you want to perform inspection at a pitch of 10 mm in both the longitudinal and circumferential directions, the maximum thickness of the pipe, t _nax , should be 20 mm, Assuming that the fluid is water, the sound speed is 1500 m/s, and the sound speed inside the tube is 5900 m/s.
Then, the number n of probes required for a circumferential inspection pitch of 10 mm is 1200 x π/10 = 377 or more, and the time τ required for measurement with one probe 1 is: Assuming that the measurement margin time d=4μs,
When calculated from formula [4], it is approximately 210 μs. On the other hand, in order to detect at 10 mm pitch in the length direction, each contact must be measured every 3.3 mS since the test pig travels at a speed of 3 m/s. Therefore, one set of measuring circuits 12
Since only a maximum of 12 contacts 1 and pulsers 3 can be connected to the , 26 measuring circuits 12 are required, which creates a problem that they cannot be accommodated in the outer shell 10 of the test pig.

Therefore, in order to solve this problem, in the present invention, the switching period τ of the pulser selection circuit 7 and the multiplexer 8 is set to _The difference ( _{τ 2} −τ ₁ )
And for a certain channel, the pulser 3 of that channel is driven τ ₁ hour before the timing at which the input to the multiplexer 8 is assigned.

This operation will be explained as the operation of the mth to (n+2)th channels among the n channels connected to one set of measurement circuits, as shown in FIG. 4. Now, taking the m-th channel as an example, after a predetermined time τ ₁ after the pulser 3m is selectively driven, the probe 1m of the m-th channel is connected to the amplifier 4 by the multiplexer 8. The connection is disconnected after a further (τ ₂ −τ ₁ ) time has elapsed.
Then, after (τ ₂ - τ ₁ ) time after the pulser 3m of the m-th channel is driven, the pulser 3 _n+1 of the (m+1)-th channel is driven, and similarly after τ ₁ hour, the multiplexer 8 is activated to the (m+1)-th channel. The same operation is performed sequentially for the (m+2)th channel, and so on.

These τ ₁ and τ ₂ are calculated as follows: In the stationary part, that is, the part where measurement must be performed, assuming that the minimum possible distance between the probe 1 and the inner peripheral surface of the tube is dmm, τ ₁ = 2dmm/V _L ... [5] Next, let d _nax be the maximum possible distance between the probe 1 and the inner peripheral surface of the tube in the steady state, and let t _{nax be} the maximum wall thickness of the tube body 2.
As, τ ₂ = 2d _nax /V _L + 2t _nax /V _S + α ...[6], that is, τ ₁ is the shortest time from driving the probe 1 until the S echo is received, and τ ₂ is probe 1
It is the maximum time from when the B echo is driven until the B echo is received plus the margin time α. Then, suppose that an S echo is detected τ ₃ hours after the probe 1 is connected to the amplifier 4, and a B echo is detected τ ₄ hours later, then d=V _L × (τ ₁ − τ ₃ )/ 2...[7] t=V _S ×τ ₄ /2...[8] Now, considering the specifications of the pipeline mentioned above, and further considering that the minimum distance between the probe 1 and the inner peripheral surface of the pipe is 120 mm, from equation [5], τ ₁ = 160 μs,
From formula [6], τ ₂ = (206 + α) = 210 μs, and (τ ₂
−
τ ₁ )=50 μs. Therefore, channels can be switched every 50 μs, and compared to the switching method shown in Figure 2, it is possible to connect 66 probes 1 to one set of measurement circuits, and a total of 377 probes. Even if the probe 1 is required, the number of measurement circuits may be six, and these circuits can be easily housed within the outer shell 10 of the test pig.

Note that in carrying out this invention, the m channel and the (m+1) channel do not necessarily have to be adjacent to each other; rather, it is better to physically separate them so that there is no interference of sound waves and stable echo detection can be achieved. . For example, when connecting a total of 66 channels to one set of measurement circuits, if the physical arrangement order of probe 1 is 1 to 66, then 1-23-45-2-24-46-3...
It will be more effective if it is driven in this order.

In other words, the probes are arranged in the circumferential direction of the capsule with a predetermined interval between them, and are further divided into groups of probes A to C, for example, every 120 degrees.
Within the group, the probes of each group are driven at 120 degree intervals.

Specifically, the first probe of group A, the first probe of group B, and the first probe of group C are driven at the same time.

Further, in this embodiment, pitting corrosion is detected, but the present invention is not limited to pitting corrosion, and abnormal parts such as scratches or irregularities inside the pipe may also be detected.

〔Effect of the invention〕

As described above, according to the present invention, the time τ ₁ for the sound wave to travel back and forth between the probe and the inner peripheral surface of the pipeline is
The time for reciprocating from the outer circumferential surface is τ ₂ , and without waiting for the time for the sound wave to be reflected, the next sound wave is emitted at a time interval of (τ ₂ − τ ₁ ), and the reception timing is set as (τ ₂ - τ ₁ ), the number of measurement circuits is reduced and abnormalities can be detected quickly and with high precision while the capsule travels through the normal location.

In addition, multiple probes are divided into predetermined groups, and when the probes in that group are selected and driven by the pulsar, each probe is Stable echo detection is possible by separating the probes and arranging them in the capsule, and for example, by driving the probes at predetermined positions in each group simultaneously, the detection speed becomes faster.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment according to the present invention, and FIG. 2 is a timing chart thereof.
Fig. 3 is a configuration diagram of an inspection pig according to an embodiment of the present invention, Fig. 4 is a timing chart showing further improved channel switching, Fig. 5 is a conventional pitting corrosion detection device, and Fig. 6 is a probe. FIG. 2 is an explanatory diagram of reflected echoes of ultrasonic waves obtained in FIG. In the figure, 1 is a probe, 2 is a tube body, 3 is a pulser, 4 is an amplifier, 5 is a time measurement circuit between T pulse and S echo, 6 is a time measurement circuit between S echo and B echo, 7 is a pulser selection circuit, 8 is a multiplexer, 9 is a timing control circuit, 1
0 is the outer shell of the inspection pig, 11 is the propulsion cup, 12
13 is a measurement circuit, 13 is a data recording device, and 14 is a battery.

Claims (1)

[Scope of Claims] 1. A piping abnormality detection device that is housed in a capsule and travels within a pipeline to detect abnormalities in the pipeline, including: a device that is disposed around the outer periphery of the capsule and emits sound waves into the pipeline; a plurality of pulsers each connected to a plurality of probes that receive the reflected wave and output it as an echo signal, and drive the probe of a selected channel; A pulsar selection circuit that sequentially selects and outputs a pulsar drive signal to drive the pulsar, and the time τ ₁ for a sound wave to travel back and forth between the probe and the inner peripheral surface of the pipeline in a steady state, and further in a steady state. The time for the sound wave to travel back and _forth between the probe and the outer peripheral surface of the pipeline in ₂ −τ ₁ )
to sequentially output to the pulser selection circuit at time intervals of , and input the echo signal from the corresponding probe during the period of (τ ₂ - τ ₁ ) after time τ ₁ has elapsed from the output timing of the selection signal. a timing controller that outputs a control signal; a multiplexer that outputs an echo signal from the probe based on the time (τ ₂ −τ ₁ ) of the control signal from the timing controller; A piping abnormality detecting device comprising: time measuring means for measuring the time between input echo signals. 2 Divide the plurality of probes into predetermined groups, and separate each probe so that when the probes in that group are driven, there will be no interference with the probes in other groups. 2. The piping abnormality detecting device according to claim 1, wherein the piping abnormality detecting device is arranged in the following manner.