JPS5818603B2 - Fushiyokusonmodokenshiyutsusouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corrosion wear degree detection device, and in particular, to detect the position of a corrosion wear part on the inner wall of a boiler, heat exchanger pipe, or other hollow pipe.
This invention relates to the configuration of a detection device that is optimal for detecting the degree of corrosion and wear and tear.

In oil refining and other chemical industries, heat exchangers with a large number of tubes are often used, and many of these tubes are in a corrosive atmosphere. It is necessary to confirm its safety, lifespan, etc.

Conventionally, as a nondestructive detection device for such a pipe, there is a method called an eddy current flaw detection method, which is often used for austenitic stainless steel pipes, brass pipes, and the like.

This device uses an excitation coil and a detection coil to detect flaws in pipes based on pulse signals from the detection coil, but the output pulses do not correspond to the depth of the corroded area and there is a limit to detection accuracy. There is.

In addition, the tube material must be made of a non-magnetic material, so there are drawbacks such as the need for magnetic saturation measures for magnetic materials such as steel pipes.

Furthermore, there are tube wall thickness measurement devices that use radiation irradiation.
Disadvantages include that measurement is limited to one direction and that measurement is impossible when tubes are piled up in a bundle.

In addition, recently, inner surface observation using a fiberscope method has been used, but it has drawbacks such as being inefficient and easily overlooked.

In view of this, as a more reliable means of detection, for equipment with a large number of tubes, such as heat exchangers, it is recommended to remove a representative tube and perform a destructive inspection to estimate the state of corrosion and wear and tear on other tubes. This is the current situation.

However, such a sampling inspection is only a guess-based measurement, which is inefficient and uneconomical.

On the other hand, there are methods such as ultrasonic wall thickness method and direct measurement using a depth gauge, but these methods have the disadvantage that they are inefficient and cannot provide highly accurate measurements.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a corrosion damage detection device that does not have the above-mentioned drawbacks.

This invention will be explained below.

First, the measurement principle used in this invention will be described.

As shown in FIGS. 1A and 1B, conductor disks 1゜2 facing each other are arranged perpendicularly to the longitudinal direction of the pipe 3 to be measured and with their circumferential surfaces close to the inner wall of the pipe. While maintaining the distance d between 1 and 2 constant, the tube 3 is moved in the longitudinal direction.

For example, it is moved in the pipe from the 1 position shown in the figure to the ■ position.

Here, the area of each of the conductor disks 1 and 2 is A1
If the inductivity between the conductor disks 1 and 2 is ε, then the conductor disk 1
．． The capacitance C formed between 2 and 2 is as follows.

Therefore, when the conductor disks 1 and 2 are charged with charges of opposite signs, the lines of electric force generated between the two disks are not all straight lines,
An arcuate curve is drawn at the peripheral edge of the disc.

Therefore, the dielectric constant ε differs between an intact position such as the one position shown in the figure and a position such as H where the corroded wear portion 4 is present due to the difference in the pipe inner diameter.

That is, if the dielectric constant at the ■ position is ε1, the dielectric constant at the ■ position is ε2 (\ε1), and the capacitance C1 formed between the conductor disks 1 and 2 at the ■ position is expressed as The capacitance C2 at the position (2) is expressed as follows.

In this case, the dielectric constant at that time is determined by the degree of corrosion damage on the tube wall.

Thus, when the conductor disks 1 and 2 are moved in the longitudinal direction within the tube while keeping the distance d constant, if there is a corroded part on the tube wall, the capacitance generated between these conductors will change. This makes it possible to detect the location of the corroded and worn portion within the pipe, the degree of corrosive wear, and the like.

A device for detecting corrosion and wear of a pipe to be measured based on this principle is shown in FIGS. 2 and 3.

One detection capacitor Cx is formed by winding a pair of opposing conductor pieces 11° and 12 around a cylindrical member 10 made of synthetic resin as an insulator or cemented carbide for protection.

This detection capacitor Cx includes a reference capacitor C8 with a predetermined capacity, a reference inductance coil L1. L2 are connected in series to form an impedance bridge circuit 13.

In this case, the reference capacitor C8 and the reference inductance coils L1 and L2 are both disposed within the cylindrical portion 10 so as not to interfere with each other, and fixed by, for example, molding.

Note that such an impedance bridge circuit may be formed using only a capacitor or a resistor.

Thus, the conductor pieces 1 are wound around both ends of the cylindrical member 10.
1. A side plate 14°15 having a diameter slightly larger than the outer diameter of 12 and slightly smaller than the inner diameter of the tube to be measured 3 is attached, and excitation lead wires are connected from one side plate to a pair of terminals of the bridge circuit 13. 16. Pull out the output lead wire 17 connected to the other pair of terminals of the bridge circuit 13 via the rectifying diode CR.

Thus, the detection probe 18 for detecting corrosion wear
is configured.

Here, an AC power source 20 is connected to the excitation lead wire 16, and a voltmeter 22 is connected to the output lead wire 17 via an amplifier 21.

In this connected state, the detection probe 18 is inserted into the pipe 3 whose degree of corrosion and wear is to be detected and is moved at a constant speed.

For example, if compressed air is blown from one direction Q, the detection probe 18 will move in the R direction, so the detection probe 18 can be moved over the entire area of the pipe 3.

Alternatively, the spray may be sprayed to one end of the tube, moved, and pulled back with a rope or the like.

When the detection probe 18 moves within the tube in this way,
Since only the capacitance of the detection capacitor CX changes in accordance with the degree of corrosion and wear existing in the tube, the balance of the bridge circuit 13 is lost, and this voltage change is converted to direct current by the diode CR and then amplified by the amplifier 21. It is displayed on the voltmeter 22.

In this way, the state of corrosion and wear inside the pipe can be easily detected.

Here, before detecting corrosion wear, adjust the capacitance or inductance Lt-L2 of the capacitor C5 so that the output voltage is the minimum according to the frequency of the AC power supply 20, etc. By providing unevenness and scanning the inside of the tube with a detection probe to obtain a calibration curve as shown in FIG. 4, reliable measurements can be made during actual detection.

FIG. 4 shows the case where the frequency of the AC power source is 144 KHz, and if a voltage as shown in FIG. 6A is obtained from this calibration curve, it is possible to infer a state of corrosion and wear as shown in FIG. 6B.

Note that in order to improve measurement accuracy, it is better to have a higher frequency of the AC power source.

Further, according to the device of the present invention, since the output voltage of the bridge circuit is converted into direct current and transmitted to a predetermined position, there are few disturbances such as noise, and reliable detection is possible.

In addition, in the above-mentioned device, one detection capacitor is formed on the entire circumferential surface of the cylindrical member that constitutes the detection plug, so it is possible to accurately detect the state of corrosion and wear that exists locally in the pipe. There may be things that cannot be done.

To solve this problem, as shown in FIG. 6, a plurality of detection capacitors 30 are arranged axially symmetrically within the cylinder so that the angular distance between the center angles formed locally is even over the entire surface of the cylindrical member. 33 are provided, and bridge circuits 34 to 36 are constructed corresponding to each of these capacitors.

Therefore, each bridge circuit 34 to
37 is excited, and the output from each bridge circuit is converted into direct current by diodes CR1 to CR4, and then the direct current signals are transmitted and read by voltmeters 39, respectively.

In this way, it is possible to reliably detect the state of corrosion and wear at the position in the pipe facing each of the plurality of capacitors 30 to 33.

On the other hand, in addition to the plurality of capacitors 30 to 33 and bridge circuits 34 to 37, a detection capacitor 40 and a bridge circuit 41 similar to those described above are arranged in parallel, and the overall state of corrosion and wear is detected by a voltmeter 42. You can also do it like this.

In addition, in the above embodiment, the output from each impedance bridge is detected by a voltmeter, but
Actually, this is not necessary, and it is sufficient to detect only the largest output among them.

In such a case, for example, the output of each impedance bridge circuit may be rectified and converted into direct current, and then the maximum voltage may be detected using an OR circuit.

In this case, if the signal is converted to direct current within the detection probe and then transmitted, the wiring for the output signal of the probe can be simplified.

[Brief explanation of drawings]

FIGS. 1A and 1B are diagrams for explaining the measurement principle used in this invention, FIGS. 2 and 3 are diagrams showing embodiments of this invention, and FIGS. FIG. 6 is a diagram showing another embodiment of the present invention. 1.2... Conductor disk, 3... Tube, 4...
... Corrosion wear part, 10 ... Cylindrical member, l
L12...Conductor piece, 13...Bridge circuit, 20...AC power supply, 21...Amplifier, 22...Voltmeter.

Claims (1)

[Scope of Claims] 1. A detection capacitor is provided with a pair of conductors wound around an insulating cylindrical member facing each other so as to be perpendicular to the longitudinal direction inside the pipe to be measured, and this detection capacitor is used as a reference. An impedance bridge circuit is formed by connecting with a capacitor and/or a reference inductance coil, this impedance bridge circuit is fixedly arranged inside to constitute a detection probe corresponding to the tube to be measured, and the impedance bridge circuit is excited with an AC power source. At the same time, the detection probe is moved in the longitudinal direction within the pipe to be measured, and a state of corrosion and wear existing in the pipe to be measured is detected based on a change in the output voltage of the impedance bridge circuit due to this movement. A corrosion and wear detection device featuring: 2. A plurality of pairs of conductors facing each other are arranged so that the angular distance between their center angles is evenly distributed over the entire surface of the cylindrical member of the insulator so that the conductors are perpendicular to the longitudinal direction of the pipe, and A plurality of detection capacitors are arranged axially symmetrically to form a plurality of detection capacitors, and a plurality of impedance bridge circuits are formed corresponding to each of the detection capacitors together with a reference capacitor and/or reference inductance, and each of these impedance bridge circuits is A circuit that is excited by a high-frequency signal is provided, and a rectifier circuit is connected to the output ends of the plurality of impedance bridge circuits so that the output is common, and changes in the output voltage of the impedance bridge circuit are converted into direct current and a predetermined value is set. A corrosion wear degree detection device characterized by transmitting information up to the position.