JPH0493604A - Internal shape detection method for specific inner form pipe - Google Patents

Abstract

PURPOSE:To ensure the accurate detection of the internal shape of a small diameter specific inner form pipe by inserting a light source emitting a small width of slit light into the pipe, picking up the annular image of the slit light with an image pickup means and detecting the internal shape of the pipe from the pickup image. CONSTITUTION:A light source 20 and an image pickup means 30 connected to each other are inserted in a speific inner form pipe 10 for detecting the internal shape thereof. In this state, a light source 20 is caused to emit light. The light, then, progresses in all peripheral directions from an annular slit 22a, and becomes incident to a pipe inside located outside the slit 22a. As a result, a bright annular image appears on the pipe inside, corresponding to the sectional form thereof. The annular image is picked up with an ITV camera 31. Consequently, an image signal outputted from the camera 31 is sent to a camera signal processing section 31a, and the image is visually observed on a monitor 31b connected to the signal processing section 31a. According to the aforesaid construction, the sectional form of the pipe inside outside the annular slit 22a can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting the inner surface shape of a tube with a deformed inner surface in which peaks and valleys are alternately formed in the inner circumferential direction.

[Prior Art] A deformed inner surface tube in which peaks and valleys are alternately formed in the circumferential direction of the inner surface is used, for example, as a heat transfer tube in an ethylene manufacturing plant. Figure 5 shows this internally deformed tube I for heat transfer tubes.
Indicates O. In the figure, 11 is a peak and 12 is a trough.

A heat exchanger tube with a deformed inner surface is usually manufactured by hot extrusion or cold pilger milling, and the material used is Cr11 material, which is difficult to process. Therefore, during manufacturing, there is a risk that the material may not reach the four bottoms of the mandrel, or that the troughs may become shallow due to wear of the mandrel.
Depending on their degree, the inner circumference may be insufficient. This inner circumference determines the heat transfer properties of heat exchanger tubes with irregular inner surfaces! ! Since this is an important quality factor, it is desirable to inspect the entire length of all products.

However, conventionally, for heat exchanger tubes with deformed inner surfaces,
There is no suitable method for detecting the inner surface shape at any position in the axial direction, and it has been impossible to inspect the circumference over the entire length.

[Problem to be solved by the invention]

That is, when detecting the inner surface shape at any position in the axial direction of a tube with an irregular inner surface shape, it is conceivable to use an inner diameter measuring device using a contactor for boat fishing. However, this device was large-scale and could not be inserted into heat exchanger tubes with irregular inner surfaces, which had an inner diameter of only about a few square meters.

Therefore, in the case of heat exchanger tubes with irregular inner surfaces, the inner shape could only be detected at the end face of the product, and the only effective method for detecting the inner shape at any position in the axial direction is to cut the product at that position. There was no such thing.

An object of the present invention is to provide a method for detecting the inner surface shape of an irregularly shaped tube, which can detect the inner surface shape at any position in the axial direction without cutting the tube, even in the case of an irregularly shaped tube with a small inner diameter such as a heat transfer tube. It is in.

[Means for Solving the Problems] The method of the present invention includes a light source that irradiates narrow slit light over the entire inner circumference of a deformed inner tube in which peaks and valleys are alternately formed in the circumferential direction of the inner surface. is inserted, and an annular image of slit light irradiated from the light source to the entire circumference of the inner surface is imaged by an imaging means inserted into the inner surface irregular-shaped tube together with the light source, and the inner surface shape is detected from the image. Become.

[Function] When a narrow slit light beam is applied to the entire circumference of the inner surface of a tube with an irregular inner surface, a brightly shining annular image appears corresponding to the cross-sectional shape of the inner surface.

When this annular image is captured by an imaging means, the inner cross-sectional shape can be detected from the image.

The light source and the imaging means have become more compact due to recent technological advances, and can be fully inserted into tubes with irregular inner diameters such as heat exchanger tubes with small inner diameters.

(Example] Embodiments of the method of the present invention will be described below based on the drawings.

FIG. 1 is a side view schematically showing an example of an optical measurement system for carrying out the method of the present invention, FIG. 2 is a cross-sectional view taken along the line 1-1 in FIG. 1, and FIG. (2) It is a cross-sectional view taken along the line n-n.

The light i1!20 has a cylindrical lamp support 21 with an outer diameter slightly smaller than the inner diameter d of the peak part of the tube 10 with an irregular inner surface.

A cylindrical light shielding body 22 with a closed end is attached to the lamp mounting side of the lamp support 21 . Light shielding body 22
has a slightly smaller diameter than the lamp support 21;
It surrounds the lamp attached to 1. The light shielding body 22 has a narrow annular slot (y)2 over the entire circumference.
2a is provided. The width of the annular sulin 22a is, for example, approximately one inch.

The light fi 20 is supported concentrically by a stay 23 in front of the imaging means 30 with the light shielding body 22 side facing the imaging means 30.

The imaging means 30 includes an ITV camera 31.

The ITV camera 31 is a cylindrical body having an outer diameter slightly smaller than the inner diameter d of the peak of the internally irregularly shaped tube IO, and a plurality of plate-shaped guides 32 are radially attached to the outer peripheral surface of the ITV camera 31. The guide 32 connects the opposing valleys 12 of the internally deformed tube 10.
The ITV camera 31 is supported concentrically within the tube 1O with a deformed inner surface, and the ITV camera 31 is inserted through the stay 23 into the ITV camera 31.
A light source 20 is supported concentrically in front of a camera 31.

The 1' TV camera 31 is configured to capture and image the entire circumference of the inner surface of the tube located on the outer surface side of the annular ring 22a provided on the light shielding body 22 of the light di20.

The ITV camera 31 includes a camera signal processing section 31a, which will be described later.
, a monitor 31b, and an image processing section 31c are connected.

When carrying out the method of the present invention, the interconnected light #20 and the imaging means 30 are inserted into the tube 10 with a profiled inner surface whose inner surface shape is to be detected. In this state, by emitting light from the lamp provided in the light source 20, the light is emitted into the annular slit z) 22a.
The light comes out in all directions around the slit and hits the inner surface of the tube located on the outer surface side of the annular slit 22a.As a result, a brightly shining annular image corresponding to the cross-sectional shape appears on the inner surface of the tube. Then, by capturing this annular image with the ITV camera 31 of the imaging means 30, the image signal output from the ITV camera 31 is sent to the camera signal processing section 31a, and the monitor 31b connected to the camera signal processing section 31a. By visually observing the image, the cross-sectional shape of the inner surface of the tube located on the outer surface side of the annular slit 22a is detected.

FIG. 4 shows a schematic diagram of the annular image 40 captured by the ITV camera 31. Both the outer contour line and the inner contour line of the annular image 40 match the cross-sectional shape of the inner surface of the tube.

Furthermore, the inner circumference is also determined by processing the image signal of the image processing unit 31CT:lTV camera 31 connected to the camera signal processing unit 31a. That is, the image processing section 31
At c, the image signal for the annular image 4o is differentiated and binarized to extract the outline of the annular image 40, and by specifying the address, the outline of the outline is approximated to a straight line.

In the method of the present invention, while viewing the annular image 40 on the monitor 31b, the light source 20 and the imaging means 30 are
By moving the tube 10 in the axial direction, the inner shape can be visually inspected over the entire length of the inner tube 1O. If a suspicious area is found through visual inspection, the light 120 and the imaging means 30 are stopped at that position, and the image processing unit 31c measures the circumference. By doing this, the inner circumferential length of the tube 10 with a deformed inner surface is inspected over the entire length of the tube.

Although the method of the present invention is effective for measuring the inner surface shape of a straight tube with an irregular inner surface in which the peaks and troughs are parallel to the tube axis, the method of the present invention cannot be applied to a tube with an irregular inner surface in a straight state before twisting. For example, it is also possible to inspect the inner surface shape of a spiral tube with an irregular inner surface.

[Effects of the Invention] As is clear from the above description, the method for detecting the inner surface shape of a tube with an irregular inner surface according to the present invention can be used to detect an irregular inner surface shape of a tube with a small inner diameter, such as a heat exchanger tube, which conventionally could only be detected by cutting the tube. It is possible to accurately detect the inner shape of the tube at any axial position without cutting the tube. Therefore, the inner surface length of the heat exchanger tube can be accurately inspected over its entire length, and its quality can be improved. Furthermore, the inner surface shape of heat exchanger tubes that are frequently installed can be detected, and the state of wear and tear can also be inspected.

[Brief explanation of drawings]

FIG. 1 is a side view schematically showing an example of an optical measurement system for carrying out the method of the present invention, FIG. 2 is a cross-sectional view taken along the arrow 1-11a in FIG. 1, and FIG. 4 is a schematic diagram of an image captured by the imaging means, and 5 is a 1. It is an end view of a heat exchanger tube with a deformed inner surface. 10゜inner deformed tube, 20. light source, 22a - annular slit, 30 - imaging means, 311 TV camera, 40 - annular image; person on the outside

Claims (1)

[Claims] (1) A light source that irradiates the entire inner circumference with narrow slit light is inserted into a deformed inner tube in which peaks and valleys are formed alternately in the inner circumferential direction, and the light source illuminates the entire inner circumference. A method for detecting an inner surface shape of a tube with an irregular inner surface, characterized in that an annular image of the slit light produced by the slit is photographed by an imaging means inserted into the tube with an irregular inner surface along with a light source, and the inner surface shape is detected from the image.