JPS6117901A - Detection for pig position - Google Patents

Abstract

PURPOSE:To detect the position of a body moving in a tube from the outside of the tube by mounting an alternating magnetic field generating device on the body moving in the tube and detecting an alternating magnetic field leaked out from the tube by a magnetic field detector to detect the position of the body moving in the tube. CONSTITUTION:The magnetic field leaked to the outside of a tube 3 from an alternating magnetic field generator 2 mounted on a pig 1 in the tube 3 is received by a detecting coil 4 and is amplified by an amplifier 5 and indicated on a meter 6. Since a frequency lower than the audio frequency region is used for the purpose of improving the detecting capability, the output of an audio frequency oscillator 7 is subjected to balanced modulation in a balanced modulator 8 by the detecting signal to obtain an audio frequency signal proportional to the leaked magnetic field so that the position of the pig 1 in the tube 3 can be detected by audition, and a receiver 9 is used to detect it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting the position of a cleaning plug in a pig used for internal cleaning of gas pipes, liquid transport pipes, etc.

[Problems to be solved by the prior art and the invention] At present, pigs (pipe P'
3 cleaning plug) is used.

The pig is complementary to the smoke removal brush, and uses air pressure to feed the inside of the pipe to clean the inside of the pipe. need to be detected.

As a detection method, there is a conventional method of emitting microphone p-waves into the pipe, receiving the reflected waves, and detecting the level of the pig by placing it in shallow water at the level of the reflected wave (%).
, No. 122258/1988, Kyuhonsha 8A, attempts to propose a new detection method that uses a magnetic field to detect outside the FC tube.

[Interlayer? ! The present invention detects the pig position by mounting a magnetic field generation source on the pig and detecting it. In this case, it was thought that there would be no detectable material due to its shielding effect.

However, as a result of various studies, the Ministry of the Invention found that a leakage magnetic field can be obtained by using an alternating magnetic field, and the technical explanation of an alternating magnetic field can be lowered to
We obtained the knowledge that the leakage magnetic field necessary for position detection can be obtained by doing so.

Original E! A is based on this knowledge, and Jl! of the alternating magnetic field generated by the 35 magnetizing field generator. The relationship between the i1 wave number and the thickness of the transmission tube wall is as follows.

Now, if the eddy currents generated outside the circle of the tube by the magnetic field generated by the magnetic field generator are IO and Ix, respectively, Iz = Io
...-1...Kan... (υHowever, X is the distance from the inner surface of the tube (mJsp is the depth at which the current value becomes 17e from the inner surface, that is, the depth of penetration of the eddy current in m). The relative permeability coefficient μ is 100 in total, and the resistance band ρ (Ω匍) is 10 [μΩa 硼] = 1i10 (Ωe
m), then p*167(,<m) --・ --・
(8J From this equation, the relationship between the # wave number and the depth of current penetration can be determined. p1 Figure 1 shows this.

The depth at which the current becomes 1/e = 0.1 d8 varies depending on the frequency, and the lower the frequency, the greater the depth of penetration.

For example, if the tube thickness; l) is 4%, the current ratio between the inner surface of the tube and the outer wall of the tube at *16 Hz is 1/e, and the attenuation is 8-68 dB.

Since this eddy current in the outer wall forms a leakage magnetic field, the position of the pig can be detected by detecting the magnetic field outside the tube.

That is, 5 the present invention also uses a magnetic field, and the generating device is a pig K.
This is the most important feature, and in implementation, it is desirable to make the number of cycles of the cross magnetic field as low as possible in order to increase detection sensitivity.

〔Example〕

Figure 2 shows a schematic system diagram of the present invention, in which a cross-magnetized n-generator 2 is mounted on a pig 1, and the magnetic field leaked to the outside of the tube 3 is received by a detection coil (NL, width increaser). Increase the width with container 5.
This is displayed on the device 6, and in order to remove interference signals,
It is effective to use the same i1m or insert a bandpass filter.

In addition, as shown in Figure 1, the reduction of the tube wall can be reduced by %.
In order to improve the detection ability, the output of another audio frequency oscillator 7 is added to the # wave 'e in the audible embodiment.
114i unit 8 for balanced modulation.

Receiver 9 receives an audio frequency signal proportional to the leakage magnetic field.
Alternatively, detection can be performed audibly using a buzzer, etc.

FIG. 3 is a detailed diagram of the rotary iron field generating device 2, which is composed of a transistor Tr1, an oscillating coil Ll@0 capacitor υ, a resistor R1, and a vitreous transistor B.

Figure 1 shows the bond strength of the pig ball detection device, that is, the magnetic field detection device.
gt is suppressed and the beat component F!±P1 of the input signal FJ (detection signal) and F2 is extracted.

Since the P1 component and the μPi component are in a proportional relationship, an output proportional to the leakage magnetic field can be obtained.

Furthermore, in order to make it easier to confirm the leakage magnetic field using the instrument 6 and the receiver υ, it is also effective to intermittent the magnetic field generated by the i-field generator 2 every 0.5 seconds to 1 second over the entire period.

[The fruit of the invention] Previously, it was thought that it was impossible to detect the pig except by using it inside the pipe, but the present invention has made it possible to control the pig from outside the pipe. , its industrial value is great.

4. Explanation of WIJ4i in the drawings Figure 1: A diagram showing the relationship between the frequency of the μ alternating magnetic field and the depth of penetration of the 9-square current, Figure 2: A schematic system diagram of the embodiment of the present invention, Figure 3:
The figure is a circuit diagram of the x magnetic field generator, and the consulting diagram is a circuit diagram of the magnetic field @ field device.

1...Pig 2...Father's magnetic field generator 3
...萱 ◆...Detection coil 5...Amplifier 6...Meter 7...Audio frequency oscillator
8...Balanced modulator 9...Hayabusa receiver No. 1 Diagram 1: tΦλte (example) - Diagram 2 Diagram 6 Diagram procedural amendment (1 volume September 6, 1982)

Claims (1)

[Claims] A method for detecting the position of a pig, characterized in that the pig is equipped with an alternating magnetic field generating device, and the position of the pig is detected by detecting the alternating magnetic field leaking outside the pipe with a magnetic field detecting device.