JPH0227604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the lining thickness on the inner surface of a tube, and more particularly to a method for measuring the lining thickness on the inner surface of a tube by which the lining thickness of a tube in a water-filled state can be measured.

When forming cast iron pipes by centrifugal casting, etc.
Usually, for reasons such as corrosion prevention, a cement mortar layer, a resin mortar layer, or a lining of paint is applied to the inner surface. In order to maintain and manage water-flowing conduits and piping, when investigating the inner lining of the pipe, especially its thickness, conventionally, water flow in the conduit or piping is stopped and the pipe is partially removed. Methods such as direct investigation or investigation using in-duct cameras are used. However, in any case, the system including the pipe must be stopped during that period, which poses a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to make it possible to measure the inner lining thickness of a pipe from the pipe surface while water is flowing through the pipe.

In order to achieve this objective, the present invention installs an ultrasonic probe on the surface of a water-filled iron pipe whose inner surface is lined, emits ultrasonic waves in the radial direction of the pipe, and emits ultrasonic waves from the inner surface of the lining on the opposite side. When detecting the energy loss of reflected waves, it is assumed that the condition of the contact surface between the tube surface and the probe, the physical properties of the water in the tube, the material of the tube, the diameter of the tube, and the material of the lining are constant. At the same time, assuming that the pipe thickness is known, the value of the energy loss based on this is known in advance, the relationship between the lining thickness and the energy loss is determined in advance, and the relationship between the lining thickness and the energy loss is calculated in advance from the detected energy loss value. The determined energy loss value is subtracted and the lining thickness is determined from the difference.

Therefore, if the condition of the contact surface between the tube surface and the probe, the physical properties of the liquid in the tube, the tube material, the tube diameter, and the lining material are constant, the detected reflected wave can be calculated by determining the tube thickness. The energy loss is a function only of the lining thickness, and the inner lining thickness of the pipe can be measured while water is flowing. This not only makes it easier to maintain and manage the pipes and pipes, but also allows for easy maintenance of pipes, linings, and water. Since it deals with the attenuation of ultrasonic waves in three substances, conventionally, ultrasonic waves can only be used as signals reflected from iron parts, but by interposing water, the waves reflected from the inner surface of the lining can be used. can be detected.

Hereinafter, one embodiment of the present invention will be described based on the drawings. In Fig. 1, 1 is a cast iron pipe;
Its inner surface is provided with a lining 2 such as a layer of cement mortar. Water 3 is passed through the tube 1, and an ultrasonic probe 4 is installed on its surface. Figure 2 shows a system diagram, where 4 is the ultrasonic probe shown in Figure 1, 5 is an ultrasonic thickness gauge for measuring the wall thickness of the pipe 1, and 6 is a reflection device used to measure the lining thickness. This is an ultrasonic detector with a cathode ray tube 7 for detecting echoes, and uses the same ultrasonic flaw detector as is. Reference numeral 8 denotes an A/D converter for the reflected wave echo height, and the output from this A/D converter 8 and the ultrasonic thickness meter 5 is processed by a loss energy calculator 9, and the result is displayed on the lining thickness display. 10 and recorder 11.

As shown in FIG. 1, an ultrasonic probe 4 is brought into contact with the surface of a tube 1 through which water 3 is passed, and ultrasonic waves 12 are emitted in the radial direction. Then, ultrasound 1
2 passes through the flesh of tube 1, a part of which passes through the lining 2
and water 3, and the opposite lining surface 1
3, and the reflected wave is detected by the ultrasonic probe 4. The detection signal can be visually observed on the cathode ray tube 7 of the ultrasonic detector 6.

The energy Pr of the reflected wave can be determined by the echo height. That is, the reflected wave suffers an energy loss compared to the emitted wave, and this energy loss is as follows: 1 Energy loss ΔP _t at the contact surface between probe 4 and tube 1 2 Energy loss ΔP _i at the thick part of tube 1 [However, ΔP _i is a function of pipe thickness t _i and pipe material m _i : ΔP _i (t _i , m _i )] 3 Energy loss ΔP _l in lining 2 [However, ΔP _l is a function of lining thickness t _l and lining material m Function with _l : ΔP _l (t _l , m _l )] 4 Consists of energy loss ΔP _w due to water 3, and if the total energy loss is ΔP _r , ΔP _r = ΔP _t + ΔP _i + ΔP _l + ΔP _w ... (i) becomes.

Now, the situation of the contact surface, the physical properties of water (liquid inside the pipe),
Assuming that the pipe material, pipe diameter, and lining material are constant, the change δΔP _r in the total energy loss ΔP _r can be expressed as δΔP _r = δΔP _i (δt _i ) + δΔP _l (δt _l ) (ii). That is, if the relationship between the pipe thickness t _i and the resulting energy loss ΔP _i and the relationship between the lining thickness t _l and the resulting energy loss ΔP _l are known in advance, the change in total energy loss δΔP _r ,
By knowing the pipe thickness δt _i and the pipe thickness δt i , the lining thickness δt _l can be determined.

According to the apparatus shown in FIGS. 1 and 2, the wall thickness of the tube 1 can be measured by using a single probe 4 and the ultrasonic thickness gauge 5, and also the thickness of the tube 1 can be measured by The lining thickness can be easily calculated by calculating the measurement result of the change in total energy loss δΔP _r and the pipe thickness using the calculator 9. Further, the energy loss of the reflected wave can be extracted by the gate analog output of a normal ultrasonic flaw detector used as the ultrasonic detector 6. The gate is set according to the pipe diameter value input in advance.

FIG. 3 shows the measurement results of energy loss depending on the pipe thickness in a ductile cast iron pipe lined with cement mortar, and FIG. 4 shows the measurement results of the energy loss depending on the lining thickness in the same cast iron pipe. From FIG. 4, it is understood that the lining thickness can be measured with an accuracy of 1 mm.

Note that, according to the present invention, it is possible not only to measure the lining thickness and investigate the decrease in the thickness, but also to measure the decrease in the inner diameter of the tube due to deposits inside the tube.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 shows an ultrasonic probe installed on the tube surface, and FIG.
This figure is a system diagram of the measuring device, FIG. 3 is a diagram showing the measurement results of energy loss due to pipe thickness, and FIG. 4 is a diagram showing the measurement results of energy loss due to lining thickness. 1...Pipe, 2...Lining, 3...Water, 4...
...Ultrasonic probe, 6... Ultrasonic detector (ultrasonic flaw detector), 13... Lining surface.

Claims (1)

[Claims] 1. An ultrasonic probe is installed on the surface of a water-filled iron pipe that is lined on the inside, emits ultrasonic waves in the pipe radial direction, and detects the energy loss of reflected waves from the inner surface of the lining on the opposite side. Assume that the condition of the contact surface between the tube surface and the probe, the physical properties of the water in the tube, the tube material, the tube diameter, and the lining material are constant, and the tube thickness is known. As such, the value of energy loss based on these is known in advance, the relationship between lining thickness and energy loss is determined in advance, and the previously determined energy loss value is subtracted from the detected energy loss value. , a method for measuring the inner surface lining thickness of a tube, characterized by determining the lining thickness from the difference.