JPS61111462A - Pitting corrosion detector - Google Patents

Abstract

PURPOSE:To detect many points efficiently by connecting plural probes and pulsers to a pair of measuring circuits, driving respective pulses successively at a fixed time interval, and synchronously with the driving, connecting respective probes to the measuring circuits successively. CONSTITUTION:When a controller 9 switches both a multiplexer 8 and a circuit 7 to the 1st channel simultaneously and sends a driving signal after very short period (a), a pulser 31 is driven, an ultrasonic wave is radiated from a probe 11 and a pulse wave voltages corresponding to T, S and B echoes are generated and amplified to measure the time between the echoes T and S by a circuit 5 and the time between the echoes S and B by a circuit. After the passage of time tau, the 2nd-n-th channels are successively switched. The time interval tauis expressed by the equation I when the maximum distance between the probe and the periphery of a pipe is dmax and the maximum thickness of the pipe is tmax. Provided that a sound speed in a solution is VL, a sound speed in the pipe body is VS and a constant fixed by the measuring circuits is alpha. Consequently, the number of measuring circuits can be reduced and the pitting corrosion of a pipe line having a large diameter can be detected with a small pitch.

Description

[Detailed description of the invention] [Industrial application field] Ru.

[Conventional technology]

Traditionally, a capsule equipped with a detection device (
A test pig (hereinafter referred to as a test pig according to common usage) is inserted into a pipeline, and the test pig is transported by the fluid flowing inside the pipeline, and is transported along the way.

The on-board inspection equipment detects pitting corrosion, the inspection pig is taken out at the exit of the pipeline, the data is reproduced, and information on pitting corrosion is obtained.
s & Pipetine International
tAspects of the British Ga
s Chtin In5pection 5ervic
e)nIn addition, the detector used is generally one using the leakage flux method as described in the above-mentioned literature.1 For example, Nippon Kokan Giho 1983, N199. p
l[]]9 to 115-' As described in Vibrine Pipe Exploration Device, etc., an ultrasonic thickness meter, an ultrasonic distance meter, etc. are used.

Figure 5 is a block diagram of a conventional pitting corrosion detection device, in which (1) is a probe housed in the inspection vig and emits and receives ultrasonic waves, and (2) is a part of the tube body. (3) is a pulsar that applies pulsed high N and FE to the probe, (
4) is an amplifier that amplifies the received signal from the probe (1);
(5) shows the T pulse that drives the pulser (3) and the probe (
1) A circuit that measures the time between the received S echo and
(6) shows the S echo received by the probe (1) and the B echo 1
The circuit (7) that measures the time between the line and the line is the fluid filled in the line tube.

The conventional pitting corrosion inspection apparatus is constructed as described above, and the waveform obtained at the output side of the amplifier 4 is generally called the I-A scope as shown in FIG. The pulse is a pulse applied by the ζ pulser (3) on the probe (1), and the S echo is reflected from the surface of the tube body (2) and reaches the probe (1) again. Ultrasonic waves are detected by the probe (1), and ultrasonic waves that are reflected by the outer peripheral surface of the tube (2) and reach the probe (1) again are converted into electrical signals. This is a pulse wave.

Now, the distance between the probe (1) and the surface of the tube body (2) is d
.

The thickness of the tube body (2) is t, the time between T pulse and S echo is T, and the time between S echo and S echo is T8.
B and the speed of sound in liquid (7) is V. , assuming that the sound velocity in the tube body (2) is v8.

Therefore, d and t can be obtained respectively.

Here, when pitting corrosion occurs on the tube body (2), d and t are when the pitting corrosion occurs on the inner circumferential surface, and t when it is on the outer circumferential surface.
Since only the pitting corrosion changes, the position and depth of the pitting corrosion can be measured according to the degree of the change.

[Problems that the project is trying to solve]

In the conventional pitting corrosion inspection apparatus as described 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 20 mm at most, so it is necessary to cover the entire circumference of a 1200A pipeline. If you try to explore without
It is necessary to equip more than 180 ultrasonic thickness gauges and ultrasonic distance meters, which is not only a cost issue, but also considering that such a large number of detection devices will be mounted on the VIG and travel inside the pipe. There was a problem that it could not be realized at all.

[Means for solving problems]

The pitting corrosion detection device according to the present invention connects a plurality of probes and pulsers to one set of measurement circuits, drives each pulser sequentially at fixed time intervals, and synchronizes with this to drive each probe and pulser. [Function] In this invention, a plurality of pulsers housed in the test pig are sequentially connected to the measurement circuit in an efficient time-sharing manner. The maximum conceivable liquid distance between the probe and the tube, the time for the sound wave to travel back and forth in the tube with the maximum wall thickness, and the sum of the measurement margin time τ2, and the minimum conceivable probe during steady state f. The difference between the time τ1 and the time it takes for the sound wave to travel back and forth along the liquid distance between the tentacle and the tube body (τ2 - τlz) is driven at a constant time interval, and the time τ!
After the lapse of time, the probe of the corresponding channel is connected to the measurement circuit for a time (τ2-τ1). Therefore, the measurement circuit inputs the S-echo and S-echo pulse waveforms from each probe in a time-division manner, and efficiently detects a large number of points with one set of measurement devices.

〔Example〕

FIG. 1 is a block diagram showing a pitting corrosion detection apparatus according to an embodiment of the present invention. In FIG. ing. (7) is a pulsar selection circuit.

(8) is a multiplexer, (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. 7 shows a time chart of the operation of the pitting corrosion detection device configured as described above.

(D-pulsar output is the first channel pulsar (31
) to the probe (11), (D-
The probe outputs are T, S, and B output from the probe (11).
A pulse signal containing pulses, a peak - the multiplexer indicates that the input of the multiplexer (8) is assigned to the first channel when this level is above the second, below.
．． The same applies to the 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 first chip through the multiplexer (8) from the initial state to τ. It is connected to the channel probe (11), and from τ to 2τ, the second channel probe ('h)f is connected, and from 2τ to 3
Up to τ, the probe (13) of the third channel is connected, and in the same way, up to n channels are connected sequentially. Then, when the timing controller (9) switches the first channel multiplexer (8) and the pulser selection circuit (7) to the first channel f at the same time, and sends the pulser drive signal a minute time later than that, the pulser of the first channel (61) is driven to emit ultrasonic waves from the probe (1□), and from the reflected ζ, pulse wave voltages corresponding to T, S, and S echoes are generated from the probe (11), and the multiplexer ( 8) to the amplifying circuit 5 (4), and is sent to the circuit (5) as before.
The time between the T pulse and the S echo is measured, and the circuit (6
) to measure the time between S echoes. Next ζ
After these 7 hours have passed, the timing control circuit (
9) is a multiplexer (8) and a pulser selection circuit (
Switch the force to the second channel, send the pulser drive signal to the pulser (32) a short time after that, and send the pulser drive signal to the probe (12).
The pulse wave voltage from is input to the amplifier (4). below,
The channels are sequentially switched to the 3rd to nth channels every 7 hours. 7 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 circumferential surface of the tube is dmax='iiF's maximum thickness is tmax, then the time 'I'max from when the trigger pulse is emitted until the S-echo is received is: 'I'max.

Therefore, α can be set as a constant with the margin time determined by the measurement circuit 6 In addition, in Fig. 882, three sets of probes (1) and three sets of pulsers (3) are each arranged as shown in Fig. 1. However, it works similarly when n channels are provided.

Next, FIG. 6 shows the four components of a pitting corrosion inspection apparatus composed of such a circuit. In Figure 1, α [ is the outer shell (11) of the test pig that stores the measuring instrument inside and travels inside the pipe, and the outer shell 0
A cup for supporting Q and receiving propulsive force from the fluid, and is made of flexible urethane rubber or the like. A large number of probes (1) are arranged facing the inner circumferential surface of the tube body (2), and the same number of probes (1) are placed inside the outer shell (1). pulsar (3) and a set of measurement circuits (1
2) , (4) to (9) are housed, and further includes a data recording device (16) consisting of a tape recorder etc. and a battery (14).
etc. are stored.

For example, if a 1200A pipeline is to be surveyed at a pitch of 15m in the circumferential direction, 256 probes (1) and pulsars (3) are arranged, and 64 probes are installed in one set of measurement circuit. When scanning is performed by switching between the pulser (1) and the pulser (3), this device is equipped with four sets of measuring circuits (12). Here, if τ = 250 μs, one noun constant circuit (
12) takes 250 minutes to complete measuring all 64 channels.
If μSX64=16 mS and the running speed of the inspection pig α0 is 1 mA, longitudinal inspection can be performed at a pitch of about 16 dragons.

However, in actual pipelines, the pipe has unevenness, and in order to avoid this, the distance d between the probe (1) and the inner circumferential surface of the pipe must be adjusted by 1 (tmax = 150B).
In addition, the running speed of the inspection pig must be approximately 31/S, and the length and circumferential direction of the
If you want to perform inspection with dish pitch.

The maximum thickness of the pipe is TMA420, assuming that the fluid is water, the speed of sound is 1300 m/s, and the speed of sound inside the pipe is 5.900.
m/g, the number n of probes required for the circumferential inspection pitch IQ*m is 1200 x π/10 = 377 or more, and is necessary for measurement with one probe (1). The time τ is.

Assuming that the measurement margin time is approximately −μS, it is approximately 210 μs when calculated from equation (4). On the other hand, in order to detect 100 pitches in the length direction, each contact must be measured every 3.3 ms since the test pig travels at a speed of 3 m/3.
Therefore, only a maximum of 12 contacts (1) and pulsers 6 can be connected to one set of measurement circuits (12), so 26 measurement circuits (12) are required, and it is impossible to fit inside the outer shell Ql of the inspection big. A problem arises in that ζ cannot be completely stored.

Therefore, in order to solve this problem, the present invention provides a pulser selection circuit (7) and a multiplexer (8).
) is defined as the minimum 1 conceivable switching period τ in steady state, and the time τ1 for the sound wave to travel back and forth in the fluid distance between the probe (1) and the tube body (2), and the maximum conceivable probe in steady state. (1)
and the tube body (2) and the tube body of maximum wall thickness (
2) Difference from the time τ2 for the sound wave to travel back and forth inside (τ2-τ1)
And for a certain channel, τ1 hours before the timing of assigning the input to the multiplexer (8),
The pulser (3) of that channel is driven.

This operation is as shown in FIG. 4 when the operation of the intermediate door to (m+2)th channel among the n channels connected to one set of measurement circuits is performed. Now, taking the ninth channel as an example, after a predetermined time τ1 after the probe (3m) is selectively driven, the multiplexer (8) (thus, the mth channel probe (1ri) It is connected to the amplifier (4), and the connection is cut off after a further (τ2-τl) time has elapsed.

After the 9th channel pulsar (3m) is activated (
After 11 hours, the multiplexer (8) is switched to the (+n+1)th channel, and the same goes for the (+n+1)th channel. rIL+2)..., and then perform !11 operations similar to E. ``This τ1 and τ2 are the minimum possible probe (1) and the inner circumference of the tube in the stationary part, that is, the part where the measurement must be performed. If the distance to the surface is d=, then 2dμ τ1”−111 ………■L Next, the distance between the largest possible probe (1) in the stationary part and the inner peripheral surface of the tube is amax, and the tube body The maximum wall thickness of (2) is tm
ax, that is, tl is the shortest time from driving the probe (1) until the S echo is received, and τ2 is the probe (1)
It is the maximum time from when the is driven until the S echo is received plus the margin time α. And the probe (1
) is connected to the amplifier (4), and if an S echo is detected 75 hours later, and another 74 hours later, then Vsx τ4 t=□ ......■. Now, thinking about the pipeline specifications mentioned above,
Furthermore, set the minimum distance between the probe (1) and the inner peripheral surface of the tube to 12
Considering 0 Tsuru, τ1 = 160μs from formula (■).

(6) From the formula T2= (2D6+(ri”210μ8
(Tl-711: 50 μS. Therefore, the channel can be switched every 50 μS, and compared to the switching method shown in Figure 2, one set of measuring circuits and 66 probes are required. (1), even if a total of 377 probes (1) are required, the number of measurement circuits is only 6, and these circuits can be connected to the outer shell of the inspection vig (if). It can be easily stored inside.

In addition, in carrying out this invention, m channel and (
m+1) channels do not necessarily have to be adjacent to each other,
In fact, if they are physically separated, there will be no interference of sound waves, and stable echo detection will be possible.
) is 1 to 66, then lj 1-2
It will be more effective to drive in the order of 3-45-2-24-46-3...

〔Effect of the invention〕

As explained above, this invention connects a plurality of probes and pulsers to a set of measurement circuits, drives each pulser sequentially at fixed time intervals, and synchronizes each probe to the measurement circuit efficiently. By connecting them sequentially in a time-sharing manner, it is possible to reduce the number of measurement circuits and mount a large number of probes and pulsers on the inspection vig, reducing pitting detection in large diameter pipelines. You can get the effect of being able to do it in a pitch.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of an embodiment according to the present invention, Fig. 2 is a timing chart thereof, Fig. 3 is a block diagram of an inspection vig of an embodiment according to the invention, and Fig. 4 is a further improved one. Timing chart showing channel switching,
FIG. 5 is a conventional pitting corrosion detection device, and FIG. 6 is an explanatory diagram of reflected echoes of ultrasonic waves obtained by a probe. In the figure, (1) is the probe, (2) is the tube, and (3) is the PAL! (4) is the amplifier, (5) is the T pulse and S
Time measurement circuit between echoes, (6) is a time measurement circuit between S echoes, (7) is a pulsar selection circuit, (8)
(9) is the multiplexer, (9) is the timing control circuit, (11 is the outer shell of the test vig, (111 is the propulsion cup, (12) is the measurement circuit, (13) is the data recording device, (14) is the test tube 5, Figure 6 □ Procedural amendment written by Kuto Patent Attorney Saburo Dokimura. Spontaneous, Commissioner of the Japan Patent Office, January 18, 1985 1, Case Indication Special Ho 59-232361 No. 2, Title of the invention Pitting corrosion detection device name (412) tI Honkoukan Co., Ltd. 4, agent 6° correction tn statement = ti “Claims” in the specification
(1) Amend the scope of claims as shown in the attached sheet. (2) The Detailed Description of the Invention column is amended as follows. Scope of claims after amendment Attachment (1)
Pitting corrosion in the pipeline is detected by emitting ultrasonic waves from multiple probes housed in a capsule and traveling inside the pipeline and arranged on the outside of the capsule facing the inner pipe joints. In a pitting corrosion detection device 1, a plurality of the probes and pulsers are connected to a set of measurement circuits, and each of the pulsers is driven sequentially at a fixed time interval, and each of the probes and the pulsers are driven synchronously with each other. A pitting corrosion detection device characterized in that a plurality of points can be detected by one set of measuring devices by sequentially connecting the probes to the measuring circuit in a time-sharing manner. (2) The sequential fixed time intervals for driving each of the above pulsars are defined as the maximum liquid distance between the probe and the tubular body and the time for the sound wave to travel back and forth through the tubular body with the maximum wall thickness that can be considered in steady state. The sum τ2 with the measurement margin time. Let the minimum possible liquid distance between the probe and the tube in steady state be the difference between the time τ□ for the sound wave to travel back and forth (τ2i1), and after the time τ1 has elapsed after each pulsar is driven. By connecting the probe of the corresponding channel to the measuring circuit for a time (τ2-τl). 2. The pitting corrosion detection device according to claim 1, wherein said one set of measuring devices is capable of detecting a large number of points.

Claims (2)

[Claims] (1) Pitting corrosion in the pipeline is prevented by emitting ultrasonic waves from a plurality of probes housed in a capsule and traveling inside the pipeline and arranged on the outside of the capsule facing the inner surface of the pipe. In the pitting corrosion detection device, a plurality of the probes and pulsers are connected to one set of measurement circuits, and each of the pulsers is sequentially driven at a fixed time interval, and in synchronization with this, each of the probes is driven. A pitting corrosion detection device characterized in that a large number of points can be detected with one set of measuring devices by sequentially connecting the above measuring circuits in a time-sharing manner. (2) The sequential fixed time intervals for driving each of the above pulsers are defined as the maximum liquid distance between the probe and the tube and the time for the sound wave to travel back and forth through the tube with the maximum wall thickness that can be considered during quantification. The difference (τ_2 - τ_1) between the sum τ_2 of the measurement margin time and the time τ_1 for the sound wave to travel back and forth between the minimum liquid distance between the probe and the tube that can be considered at the time of quantification, and Time (
Claim 1 characterized in that by connecting the probes of channels corresponding to τ_2 - τ_1) to the measuring circuit, it is possible to detect a large number of points with the one set of measuring devices. The pitting corrosion inspection device described in .