JPH03120452A - Detection of corrosion of supporting plate for heat transfer tube of heat exchanger - Google Patents

Abstract

PURPOSE:To measure the length of the remaining sound part of a supporting plate by inserting a radioisotope ray source into a heat transfer tube, inserting a radiation measuring instrument into the other heat transfer tube adjacent to the heat transfer tube and measuring the radiations radiated by the ray source. CONSTITUTION:The radioisotope ray source 2 which is provided at the front end of a hose 4a for coupling and has further a probe 1 for low-frequency eddy current flaw detection via a hose 4b for coupling at the front end thereof is inserted through a water chamber 7 by the hose 4a into the heat transfer tube penetrating through the supporting plate 9 to be measured. A supporting plate signal is generated when the probe 1 arrives at the supporting plate region. The ray source 2 arrives at the center 9a of the supporting plate when the ray source is inserted by the spacing L1 between the ray source 2 and the probe 1 from this position. The radiation measuring instrument 3 constituted in the same manner is inserted into the adjacent heat transfer tube and is similarly positioned. There is a specified relation between the transmission rate of the radiations which are received by the measuring instrument 3 and radiated by the ray source 3 and the length of the remaining sound part of the supporting plate 9 and, therefore, the corroding part 10 at the center 9a can be detected by the radiations received by the measuring instrument 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting corrosion of a heat exchanger tube support plate of a specific heat exchanger using radiation.

[Conventional technology]

In various plants such as chemical plants, a heat exchanger as shown in FIG. 3 is used to exchange heat between fluids of the same type or different types.

In FIG. 3, 11 is a heat exchanger container, and the primary fluid is passed through an inlet nozzle 12 to a water chamber 7a, a heat exchanger tube ga, and an ice chamber 7.
b, is discharged from the outlet nozzle 15 via the heat exchanger tube 8b and the water chamber 7c.

On the other hand, the secondary fluid F1 flows in from the secondary side inlet nozzle 16, exchanges heat while passing through the gap between the heat transfer tubes 8m and 8b, and is discharged from the secondary side specific nozzle 17.

In addition, since there is a partition plate 18 in the center of the container 11 that divides the ice chamber and the heat transfer tube group into two, both the primary fluid and the secondary fluid reciprocate along the entire length of the container 11 for effective heat exchange. be able to.

Generally, the heat exchanger tubes in a heat exchanger are often long, which can cause danger to the heat exchanger tubes, and in the worst case, the heat exchanger tubes may come into contact with each other, making effective heat exchange impossible at that point, or damage may occur.

Various methods have been adopted to prevent this, but the third
A support plate 9 is commonly used to prevent the tubes from coming into contact with each other, as shown in FIGS.

However, depending on the material of the support plate 9 and the chemical properties and temperature of the secondary fluid, corroded portions 10 may occur on the support plate 9 around the heat exchanger tubes as shown in FIG.

The detection method for detecting the corrosion of the support plate 9 was to insert the eddy current probe 21t into the tube interior 22 for flaw detection.

[Problem to be solved by the invention]

The conventional corrosion detection method uses an eddy current flaw detection probe 21. In the following case, it is possible to detect the corroded part 10, but it is impossible to estimate the length Tt of the remaining healthy part.

If the length T of this remaining healthy part becomes smaller (that is, if the corroded part becomes larger), the pipe may be deformed or damaged due to vibration. Therefore, know the length of this T and replace the support plate 9. However, this requirement could not be met using eddy current testing.

The present invention aims to solve the above problems.

[Means to solve the problem]

A heat exchanger heat transfer tube support plate corrosion detection method of the present invention involves inserting a radioisotope source having a positioning eddy current probe and coupled to the tip of a hose into a heat transfer tube passing through a support plate to be measured. , a radiation measuring device having a positioning eddy current flaw detection probe coupled to the tip of the hose is inserted into another heat transfer tube adjacent to the same heat transfer tube, and the radiation measuring device is detected from the radiation emitted by the radioisotope source. is characterized in that the length 't- of the remaining key holding healthy portion of the support plate is measured.

[Effect]

In the above, first, a radioisotope source is inserted through a hose into a heat exchanger tube that passes through a support plate to be measured. When the radioisotope source reaches the vicinity of the support plate and the vortex deep wound probe generates a support plate signal, the position 1t of the radioisotope source is finely adjusted to match the center of the support plate.

Next, a radiation measuring device is inserted into the heat exchanger tube adjacent to the heat exchanger tube into which the radioisotope source is inserted. Similar to the radioisotope radiation source described above, when the eddy current flaw detection probe generates a support plate signal, this radiation measuring instrument finely adjusts its position to match the center of the support plate.

When the radioisotope source and the radiation measuring device coincide with the center of the support plate, the radiation measuring device receives the radiation emitted by the radioisotope source.

Since there is a certain relationship between the radiation transmittance rate of the radiation received by the radiation measuring device and the length of the remaining healthy portion of the support plate, the radiation measuring device Measure the length of the remaining healthy part of the support plate from the ratio.

As a result of the above, it has become possible to non-destructively measure the degree of corrosion of the support plates around the heat exchanger heat transfer tubes using radiation, and it has become easier to decide whether to replace the support plates, and corrosion of the support tubes has become possible. It also prevents damage to the heat transfer tubes due to bulges.
It has become easier to maintain the quality of the heat exchanger.

〔Example〕

An embodiment of the present invention will be explained with reference to FIG.

The corrosion detection method of this embodiment shown in FIG. 1 is performed in a heat exchanger having a heat exchanger tube 8 supported by a support plate 9, the tube end of which is inserted into a tube plate 5, seal-welded 6, and communicates with a water chamber 7. A probe 1t for low frequency eddy current flaw detection is provided at the tip of the coupling hose 4a and further connected to the coupling hose 4b.
- The radio isotope source 21 is inserted into the heat exchanger tube 8 of the heat exchanger, and the low frequency vortex direct current deep wound probe 1 is installed at the tip of the coupling hose 4a and further connected to the probe 1 for deep wounds via the coupling hose 4b. A radiation measuring device 3 ft having the above-mentioned radioisotope source 2 is inserted into the heat transfer tube 8 adjacent to the heat transfer W8 into which the radioisotope source 2 is inserted, and the radiation measuring device 3 receives and supports the radiation emitted by the above-mentioned radioisotope source 2. Measure the length of the healthy portion of plate 9.

In the above, first, the radio isotope source 4-2 is inserted into the heat transfer '#8 via the primary side nozzle and the water chamber 7 using the connecting hose 4aK. A low frequency eddy current damage probe 1 is attached to the tip of the radioisotope source ÷ 2 via a coupling hose 4b, and when this probe 1 reaches the pressure in the support plate area, it generates a support plate signal. do.

Because the distance between the radioisotope source 2 and the probe 1 is long, after the probe 1 generates the support plate signal, it becomes even longer, and when it is inserted, the radioisotope source 2
reaches the support plate center 9a. In this case, the insertion and movement of the radioisotope source 2 into the heat exchanger tube 8 is performed automatically or manually by an insertion device (not shown) installed outside the heat exchanger.

Radiation measuring device 30 positioning radio isotope source 2
It is done in the same way. That is, the radiation measuring device 3 is inserted into the heat exchanger tube 8 adjacent to the heat exchanger tube 8 into which the radioisotope source 2 has been inserted, using the coupling hose 4a. Is there a coupling hose 4b at the tip of the radiation measuring device 3? A low frequency eddy current flaw detection probe 1 is attached through the probe 1, and when this probe 1 reaches the support plate region, a full support plate signal is generated. Therefore, as in the case of the radioisotope source 2, if the length is further inserted, the radiation measuring device 3 will also reach the support plate center 9a.

By the above operation, the center of the radioisotope source 2, the center of the radiation measuring device 3, and the center 9a of the support plate 9 are aligned, so that the radiation received by the radiation measuring device 3 causes corrosion at the center 9a of the supporting plate. Part 10 can be detected.

Although the corroded portion 10/I'i shown in FIG. 1 is uniformly corroded, it is usually not always uniform and is often irregular as shown in FIG. 5.

In this embodiment, the radioisotope source 2 and the measuring instrument 3 are properly positioned at any part of the thickness of the support plate 9, which is positioned based on the support plate signal from the eddy current probe 1. Since they can be placed facing each other, accurate measurement is possible.

Even if the corroded portion 10 exists, the support plate region can be detected by the eddy current probe IK because low frequency waves with high penetrating power are used.

Next, the method of measuring the length of the remaining healthy portion of the support plate using the radiation measuring device 3 will be explained.

FIG. 2 shows the relationship between the length of the remaining healthy portion of the support plate and the radiation transmittance rate.

The vertical axis is the radiation transmission dose rate reaching the radiation measuring device 3, and the horizontal axis is the length of the remaining healthy part of the support plate. T is the case where the support plate is not corroded at all.

In addition, the S curve in the figure shows the change depending on the length of the radiographic line 11' ratio for only the remaining healthy part (density 7.9).
The line shows the change in the radiation transmission rate when a corroded part (density 4) is added.

In actual measurement, it is impossible to measure the Sdh line, and this M curve must be measured.

The length of the remaining healthy portion of the support plate is measured by measuring the radiation transmittance using the radiation measuring device 3, and converting it into the length of the remaining healthy portion using the M curve.

Note that this measurement does not necessarily have to be performed at the center of the support plate, and as long as the center of the radiation source and the center of the measuring device coincide, a certain degree of vertical movement is acceptable.

As a result of the above, it has become possible to non-destructively measure the degree of corrosion of the support plates around the heat transfer tubes of a telethermal heat exchanger using radiation, making it easier to decide whether to replace the support plates and to eliminate the corrosion of the corroded parts of the support tubes. It also prevents damage to the bulging heat transfer tubes.
It has become easier to maintain the quality of the heat exchanger.

〔Effect of the invention〕

A heat exchanger heat exchanger tube support plate corrosion detection method of the present invention involves inserting a radioisotope source having a positioning eddy current flaw detection probe into a heat exchanger tube that passes through a support plate to be measured, and Insert a measuring device on the radiation side with a positioning eddy current flaw detection probe into the heat transfer tube, and determine the length of the remaining healthy part of the support plate from the radiation received by the radiation measuring device. i1i! It has become possible to non-destructively measure the degree of corrosion on the support plates around the heat exchanger heat transfer tubes using t, making it easier to determine whether the support plates should be replaced. Damage was also prevented, making it easier to maintain the quality of the heat exchanger.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, FIG. 2 is a diagram of the relationship between the length of the remaining healthy part and the radiation transmission rate in the above-mentioned embodiment, and FIG. 3 is an explanatory diagram of the structure of a heat exchanger. FIG. 4 is an explanatory diagram of a heat exchanger tube support structure of a heat exchanger, and FIG. 5 is an explanatory diagram of a conventional detection method. DESCRIPTION OF SYMBOLS 1...Eddy current flaw detection probe, 2...Radioisotope source, 3...Radiation measuring instrument, 4a, 4b...Hose for coupling, 5...Tube plate, 6
... seal welding, 7 ... water chamber, 8 ... heat exchanger tube, 9 ... support plate, 9a ... support plate center, 1
0...corroded part.

Claims (1)

[Claims] A radioisotope source that has a positioning eddy current probe and is coupled to the end of the hose is inserted into a heat transfer tube that penetrates the support plate to be measured, and then placed into another heat transfer tube adjacent to the same heat transfer tube for positioning. A radiation measuring device having an eddy current flaw detection probe coupled to the tip of the hose is inserted, and the radiation measuring device measures the length of the remaining healthy portion of the support plate from the radiation emitted by the radioisotope source. Characteristic method for detecting corrosion of heat exchanger tube support plates.