JP2000088561A - Method for detecting running position of pig in conduit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a detecting method in which the position inside a conduit of a pig can be detected by a method wherein pickups are installed in a plurality of places separated at proper distances inside the conduit used to run the pig, a plurality of pieces of running sound data are acquired so as to be compared and the time difference between patterns which agree is found. SOLUTION: Pattern in which respective pieces of running sound data agree, especially patterns of a sound generated at a time when a pig 2 overcomes welding lines 3, are compared, and the time difference between a pickup 6a and a pickup 6b is found. In running sound data which are acquired by the respective pickups 6a, 6b, various noises are contained in addition to a sound in a specific pattern. Even in a sound in a pattern to be detected, the propagation characteristic of a sound which is transmitted along a conduit 1 is different according to a frequency. As a result of various experiments, a sound at a frequency of 200 to 300 Hz is propagated satisfactorily along the conduit 1 regarding running sound data on the pig 2. The attenuation of a sound at the frequency or higher is large, and many noises are contained. Then, when the patterns which agree in the running sound data acquired by the pickups 6a, 6b are compared by using data which is hard to attenuate, they can be compared easily, and a position can be detected precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a running position of a pig in a conduit.

[0002]

2. Description of the Related Art Pigs running in a conduit buried in the ground include an inspection pig for inspecting a defect of the conduit such as corrosion thinning, a cleaning pig for cleaning the conduit, and an inner surface of the conduit. There is a caliper pig for inspecting the shape of the pig, etc., and when these pigs are run in the conduit, it is necessary to grasp the running position of the pig in case the pig should stop.

[0003] In the case of a pipe made of steel pipe, since the welding line protrudes from the inner surface, the sound generated when the pig passes this point propagates to a place several kilometers away. For this reason, conventionally, an acceleration pickup was attached to the launcher for pig introduction and the receiver for derivation of pigs in governor stations, etc.
The pig's position has been monitored by collecting the pig's running sound data and comparing the pattern in the running sound data, especially the sound emitted when the pig crosses the welding line, with the finished drawing of the conduit. For example, see JP-A-8-101172.

On the other hand, the present inventors have collected acceleration sound pickup data at two places by attaching acceleration pickups to both the launcher for introducing the pig and the receiver for deriving the pig in the above-described governor station, etc.
A method has been proposed in which a time difference is obtained by comparing two traveling sound data, and a pig position is calculated from the obtained time difference and a distance between the acceleration pickups. For example, JP-A-8-2
See 33932.

[0005]

However, the collected traveling sound data includes various noises,
Since the propagation characteristics of the traveling sound propagating along the conduit are different for each frequency component, it may be relatively difficult to find the time difference between the respective pickups of the matching patterns in the traveling sound data. An object of the present invention is to solve such a problem.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, pickups are installed at a plurality of locations at appropriate distances along a conduit along which a pig travels to collect a plurality of traveling sound data. In a method of comparing the matching patterns of the respective traveling sound data to determine the time difference in the respective pickups of the matching patterns, and detecting the position in the pipe of the pig by the time difference and the distance between the pickups,
It is proposed that the comparison of the matching patterns be performed on the traveling sound data with the high frequency cut.

In the above configuration, the present invention proposes that the comparison of the matching patterns is performed on the traveling sound data cut off at 300 Hz or more.

Further, the present invention proposes that, in the above-described configuration, comparison of matching patterns is performed by a cross-correlation technique.

According to the present invention, in the above method,
The absolute time,
It is proposed to refer to a characteristic weld seam sound, a characteristic weld seam sound pattern or a middle sound between adjacent pickups.

In the present invention, the pickup can be an acceleration type pickup as in the prior art.

In the present invention, the pickup can be installed on a launcher for introducing the pig into the conduit and a receiver for extracting the pig.

According to the present invention described above, the comparison of the matching patterns is performed by cutting the high-frequency band which is easily attenuated and using the traveling sound data of the low-frequency band which is hardly attenuated. Detection becomes possible.

[0013]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view conceptually showing the overall configuration to which the method of the present invention is applied. Reference numeral 1 is a conduit such as a gas pipe, 2 is a pig running in the conduit 1, and 3 is a welding line projecting into the conduit 1. Reference numerals 4 and 5 denote a launcher for introducing the pig 2 and a receiver for deriving the pig 2 provided at the governor station, respectively. Pickups, in this case, acceleration pickups 6a and 6b are installed. The pickups 6a and 6b are used for sound propagating along the conduit 1,
That is, an appropriate configuration can be applied as long as one or both of the sound propagating in the conduit 1 and the sound propagating in the fluid in the conduit 1 can be collected. Each pickup 6
The traveling sound data captured by the amplifiers 7a and 7b
Recording device 8 such as DAT (Digital Audio Tape)
a, 8b and processed by the processing device 9. In the processing device 9, the traveling sound data 10 a, captured by the respective pickups 6 a, 6 b and subjected to necessary pre-processing,
10b are compared by a cross-correlation technique. As one of the pre-processes, there is a process of filtering the traveling sound data 10a and 10b to cut a high frequency component, for example, a frequency component of 300 Hz or more. This filtering processing of the traveling sound data can be performed at an appropriate place from the time when the data is captured by the pickups 6a and 6b to the time when the processing apparatus 9 compares the data by the cross-correlation technique. As described above, by comparing the two traveling sound data by the cross-correlation method in the processing device 9, that is, a pattern in which the respective traveling sound data coincide with each other, in particular, a pattern of a sound emitted when the pig 2 crosses the welding line 3 And compare each pickup 6 in this pattern.
The time difference between a and 6b can be obtained. Here, the comparison of the matching patterns can be performed based on the absolute time, the characteristic welding line sound, the characteristic welding line sound pattern, or the intermediate sound of the adjacent pickup. When using a welding line sound or a welding line sound pattern as a reference for comparing matching patterns, by counting the welding line sound in long-time running sound data,
Since the welding line that emits the sound can be specified, the traveling sound data can be sent to the recording position of the welding line sound by the specific welding line and the comparison can be performed. Can be reduced. And
When the time difference Δt is obtained in this manner, from the distance L between the pickups 6a and 6b and the speed V of the sound transmitted along the conduit 1, the pickups 6a and 6a of the pig 2 are calculated by the following equation.
The position between 6b can be determined. Pig position = (L + VΔt) / 2 Note that the sound velocity V is determined by the following equation when the sound detected by the pickups 6a and 6b is transmitted through the conduit 1 itself.
If the fluid has propagated a fluid such as gas in the conduit 1, the speed may be set to that speed.

As described above, the traveling sound data collected by the respective pickups 6a and 6b include various kinds of noises in addition to a specific pattern of sound generated when the pig 2 crosses the welding line 3. In addition, even if the sound has a pattern to be detected, the propagation characteristic of the sound transmitted along the conduit 1 differs depending on the frequency. As a result of various experiments, with respect to the traveling sound data of the pig 2, sounds having a frequency of 200 to 300 Hz propagate well along the conduit 1, but sounds having a frequency higher than 200 Hz have a large attenuation. Also, there is much noise in the higher frequency band. Therefore, in the present invention, as described above, the comparison of the matching patterns in the traveling sound data collected by the two pickups 6a and 6b is based on the low-frequency traveling sound data that cuts the high-frequency region that is easily attenuated and the low-frequency region that is hardly attenuated. This makes it easy to compare patterns, and enables accurate position detection.

[0015]

As described above, the present invention has the following effects. a. Accurate detection of the pig position is possible. For example, even when the pig starts running at a high speed after the pig is stopped on its side, the position can be grasped. b. If the mounting intervals of the plurality of pickups are accurately grasped in advance, a detailed plan drawing of the conduit network is not required for position detection.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram conceptually showing an entire configuration to which a method of the present invention is applied.

[Explanation of symbols]

 Reference Signs List 1 conduit 2 pig 3 welding line 4 introduction launcher 5 extraction receiver 6a, 6b acceleration pickup 7a, 7b amplifier 8a, 8b recording device 9 processing device 10a, 10b running sound data

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F068 AA02 BB08 BB10 BB12 CC00 DD00 DD12 FF00 FF02 HH03 HH04 JJ21 KK16 KK18 LL17 QQ12 QQ18 TT25 2G047 AA07 AB01 BA05 BC02 EA10 GG17 GG36 GG46

Claims (9)

[Claims] 1. A pickup is installed at a plurality of locations at appropriate distances along a conduit along which a pig travels to collect a plurality of traveling sound data, and a comparison is made between patterns in which the traveling sound data match. In the method of determining the time difference between the pickups of the patterns to be picked up and detecting the position in the pipe of the pig based on the time difference and the distance between the pickups, the comparison of the matching patterns is performed on the traveling sound data with the high frequency cut. Method for Detecting Pig Traveling Position in Moving Pipe 2. The method according to claim 1, wherein the comparison of the coincident patterns is performed with respect to the traveling sound data in which the frequency is cut off at 300 Hz or more. 3. The method according to claim 1, wherein the comparison of the coincident patterns is performed by a cross-correlation technique. 4. The pig travel position detecting method according to claim 1, wherein the comparison of the matching patterns is performed based on an absolute time. 5. The method according to claim 1, wherein the comparison of the matching patterns is performed on the basis of a characteristic welding line sound.
Method for detecting running position of pig in conduit as described 6. The method for detecting a running position of a pig in a conduit according to claim 1, wherein the comparison of the matching patterns is performed with reference to a characteristic welding line sound pattern. 7. The method for detecting a running position of a pig in a conduit according to claim 1, wherein the comparison of the matching patterns is performed with reference to an intermediate sound between adjacent pickups. 8. The method according to claim 1, wherein the pickup is an acceleration type pickup. 9. The method according to claim 1, wherein the pickup is provided on a launcher for introducing the pig into the conduit and on a receiver for extracting the pig.