JPS5822907A - Dimension measuring method of tubular substance - Google Patents

Abstract

PURPOSE:To measure dimensions of an inside diameter with high accuracy, by transmitting and receiving an ultrasonic pulse in 2 point positions of the outside, which are opposed to each other through the axial core of a tubular substance, and measuring the inside diameter dimensions of the tubular substance. CONSTITUTION:Ultrasonic pulse transmitting and receiving probes 2, 3 are provided on separate positions of the outside, which are opposed to each other through the axial core of a steel pipe 1 being a tubular substance. Both the probes 2, 3 are placed in water 4 in order to improve acoustic coupling with the steel pipe 1, and send out an ultrasonic pulse vertically against the steel pipe 1 in the direction as indicated with an arrow. The ultrasonic pulse, at first, is reflected by the outside circumferential surface of the steel pipe 1, and this reflected wave is received by both the probes 2, 3. Subsequently, a reflected pulse from the inside circumferential surface of the steel pipe 1 is received, and a value of the inside diameter of the steel pipe 1 can be known easily by comparing a diagram whose quadrature axis and axis of ordinates show a time of a well-known steel pipe such as an outside diameter D0, an inside diameter d0, thickness t0, t0', etc. and pulse intensity, respectively, with a measured value of a steel pipe to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the inner diameter of a tubular object such as a steel pipe.

Conventionally known methods for measuring the dimensions of tubular objects include, for example, a method of optically measuring the outer diameter using a photodiode array, and a method of measuring the inner thickness using a radiation or ultrasonic wall thickness gauge. Therefore, by using these, the inner diameter dimension of a tubular object can be measured from the outer diameter minus the inner thickness.

However, when measuring the inner diameter using this method, it is necessary to install a device for measuring the outer diameter and a device for measuring wall thickness, which requires a large amount of snow throwing space for the device. A problem arises that makes management troublesome. Furthermore, since two different types of devices are used, when measuring the tubular object while it is being transported, it is very difficult to match the measurement points, resulting in large measurement errors.

This invention was made in view of these problems, and it is possible to reduce the installation space of the equipment involved in measurement, to facilitate management, and to be able to carry the tubular object in the axial direction while measuring it. It is an object of the present invention to provide a method for measuring the dimensions of a tubular object that can measure the inner diameter with high accuracy.

This invention transmits ultrasonic pulses perpendicularly to the axial direction from two points on the top and outside of the tubular object that face each other through the axial center of the tubular object. By receiving the reflected waves and the reflected waves from the inner circumferential surface, the distance between the two transmission points of the ultrasonic pulse measured in advance and the time difference between the transmission time of the ultrasonic pulse and the reception time of each reflected wave can be determined. By measuring the inner diameter of the tubular object, it is possible to ensure that the measurement points of the outer diameter and wall thickness match, and to downsize the device used.

Embodiments of the present invention will be described below with reference to the drawings.

In the figure, reference numeral 1 indicates a steel pipe as a tubular object, which is located at a position opposite to each other through the narrow center of the pipe 1 (-180 different positions in the circumferential direction of the pipe 1) and at a position away from the outside of the steel pipe 1. Probes 2 and 3 for transmitting and receiving ultrasonic pulses are provided, respectively. A measuring device equipped with transmitting/receiving rights, a memory, an arithmetic device, etc. (not shown) is connected to the measuring probe 2.3. Said steel pipe 1
On the outside of the outer periphery of the sound probes 2 and 3,
3, ultrasonic pulses are transmitted directly in the axial direction of the steel pipe 1, as shown by concentrated arrows in the figure.

In this configuration, the ultrasonic pulses transmitted from the measuring probes 2 and 3 to the pipe 1 are first reflected by the outer peripheral surface of the steel pipe 1. In addition, a part of the light strikes the wall of the steel pipe 1 and is reflected by the inner circumferential surface. These reflected waves are received by the measuring probes 2 and 3. If each of these pulse waves is plotted horizontally along the time axis, it will become as shown in FIG. That is, in Figure 2, T is the transmitted pulse of the ultrasonic wave, Sl is the first reflected pulse from the outer circumferential surface of the steel pipe 1, %BI''!eB3 is the first reflected pulse from the inner circumferential surface of the steel pipe 1, respectively.

2nd and 3rd reflected pulses, Sl - tube 10. ) shows the second reflected pulse from the outer peripheral surface.

Before measuring the outer diameter D1, wall thickness t, tl, and inner diameter d of the steel pipe 1, calibration is performed using a steel pipe whose outer diameter and wall thickness are known. That is, the outer diameter is Do and the wall thickness is 10. t0
' steel pipes are used, and the transmitting and receiving surfaces of each probe 2 and 3 and the steel pipe 1 are
The distance go+go' from the outer peripheral surface of the ultrasonic pulse T to the transmission time t8 and the reflection pulse St reception time t! The time difference between (
tt-11) and the propagation velocity vw of ultrasonic waves in water, 2g(go * go') = VW・(tt i+ )
・It is determined by "■.

Then, from the distance @go, go' and the outer diameter DO, the measuring probe 2,
The distance eO between the transmitting and receiving surfaces of 3 is l o ” go + go' + Do
...Measure by ■.

Also, the wall thickness tO+'O' is the reception time t of the reflected pulse S1!
and the reception time t3 of the reflected pulse B1 (ts
ts) and the longitudinal wave propagation velocity v of the ultrasonic pulse in the steel pipe 1
s and 2t (totto') = VS・(ts tt)
...Measure by ■. And known outer/diameter 00%
The wall thickness to obtained by measurement is 10etO゛.

t , 1 and distance IQs wall thickness t o , t Ol
Calibrate.

By measuring the dimensions of the steel pipe 1 to be measured after calibrating in this way, more accurate measurements can be made. As shown in FIG. 3, first, the distance g+rg,' and the wall thickness i1+'l' between the transmitting/receiving surface of the measuring probe 2.3 and the outer peripheral surface of the steel pipe 1 can be measured from the relational expressions (1) and (2) above. and outer diameter D1,
The inner diameter d1 is Dt =io (gt +gx')
... ■dB = DI (tl + tt')
...It can be measured by performing the calculation process of ■.

In this way, the outer diameter DI and wall thickness t of the steel pipe 1 are determined.

By measuring t,' and the inner diameter d, the number of measuring devices installed can be reduced to one, the installation space can be reduced, and equipment management such as guard maintenance and inspection becomes easier. In addition, since the measurement points for the steel pipe 1 can be matched for each measurement of the outer diameter, wall thickness, and inner diameter, errors due to deviation of the measurement points when measuring the steel pipe 1 while being conveyed in the axial direction can be avoided. It is possible to measure dimensions with high precision without any problems.

By the way, when measuring the steel pipe 1 while transporting it in the axial direction, if the steel pipe 1 is transported by self-propelled rotation, that is, by spiral transport, the dimensions of the outer diameter, wall thickness, and inner diameter can be measured at all angles on the outer circumferential surface of the steel pipe 1. This makes it possible to measure the dimensions of the steel pipe 1 more accurately. In this case, if a plurality of pairs of probes are provided around the steel pipe 1, substantially the same effect can be obtained without spirally conveying the steel pipe 1.

By the way, the underwater propagation speed vw of the ultrasonic pulse and the longitudinal wave propagation speed vs in the steel pipe depend on the temperature vW: 0.23°/C
(θ~35C) 1, vs; 0, 0085 excellent/C (0~1
00r), so in order to maintain good measurement accuracy, it is necessary to adequately control the temperature of the stiffness so that the distance g and wall thickness t do not change due to temperature. . Furthermore, if a temperature change occurs, it is necessary to perform temperature correction.

Also, the measurement error is as shown in Figure 4.
It also occurs if the ultrasonic pulses from the tube are not transmitted correctly towards the particulars of the tube.

That is, - the outer diameter of tube 1 is D1, the distance between the vertical line passing through the axis and the transmission line of the ultrasonic pulse is δ, and the elevation angle when looking at the position where the ultrasonic pulse reaches the outer peripheral surface of one tube from the vertical line and the axis If α is α=taa” (2δ/D)
...■, and the deviation Δg of the distance g is Δg=n/2 (1/lhα-1) ...■. For this reason, it is necessary to maintain δ to the required accuracy.

Although the above embodiments have been described using a single tube as the tubular object, it is needless to say that the present invention is not limited to this.

As described in detail above, according to the present invention, ultrasonic pulses are transmitted perpendicularly to the axial direction of the tubular object from two points on the outside of the tubular object that face each other via the axial center of the tubular object. The reflected waves from the outer circumferential surface and the reflected waves from the inner circumferential surface of the tubular object are respectively received, and the distance between the two transmitting points of the ultrasonic pulse and the time of transmitting the ultrasonic pulse are measured in advance. Due to the time lag between the reception of the reflected waves from the outer and inner circumferential surfaces, the inner diameter of the tubular object requires only one unit, and the installation space can be reduced, and the equipment can be easily managed.
Moreover, it is possible to provide a method for measuring the dimensions of a tubular object, which can perform highly accurate inner diameter measurements without errors due to deviations of measurement points even when the tubular objects are conveyed in the axial direction and the inner diameter dimensions are continuously measured.

[Brief explanation of drawings]

The figures show an embodiment of the present invention. Figure 1 is a diagram for explaining dimension measurement during calibration, Figure 2 is a timing diagram showing transmission and reflection timing of ultrasonic pulses, and Figure 3 is a diagram for explaining the measurement of dimensions during calibration. FIG. 4 is a diagram for explaining the dimension measurement of the steel pipe to be measured. FIG. 4 is a diagram for explaining the error caused by the shift in the transmission position of the ultrasonic pulse to the steel pipe. 1... Steel pipe, 2, 3... Ultrasonic pulse transmission/reception probe. Figure 1. Figure 2 t1t2t3 Time-

Claims (1)

[Claims] two outer sides of the tubular object facing each other across the axis of the tubular object;
Transmit an ultrasonic pulse perpendicularly to the axial direction from a point position, and receive reflected waves from the outer circumferential surface and inner circumferential surface of the tubular object, respectively.1. Based on the pre-measured distance between the two transmitting points of the ultrasonic pulse and the time difference between the time of transmitting the ultrasonic pulse and the time of receiving the reflected waves from the outer and inner circumferential surfaces of the tubular object, A method for measuring the dimensions of a tubular object, characterized in that the inner diameter of the object is measured.