Method and a device for determining the cross-sectional dimensions of the inner space of elongated, tubular bodies

Abstract

When mapping out the internal cross-sectional dimensions of elongated, tubular bodies, correlated values of the external cross-sectional dimensions and wall thicknesses are measured along measuring lines from the outside of the body and the sum of the wall thicknesses measured along each measuring line is subtracted from the external cross-sectional dimension measured along the same or substantially the same measuring line. This avoids the use of measuring means in the interior of the tubular bodies, whereby the measuring can be carried out much faster and without the danger of injuring the internal surface of the bodies.

Description

The present invention plane. In both the instances mentioned, equipment 9 has to comprise means for storing the measuring result or results obtained first for the brief span of time that corresponds to a revolution through angle α.

It is, of course, possible also in this case to dispense with the storing means, provided that it is possible to tolerate the inaccuracy residing in the circumstance that external diameter and wall thicknesses are not measured along exactly the same measuring line. The angle α, in this case, ought to be rendered as small as possible. The storage means can also be dispensed with in the case where all the measuring means are mounted in the same plane through measuring axis M, that is to say in pairs behind each other in the direction of the measuring axis. Even if this method does not produce entirely accurate measuring results, it will, however, often be possible to employ it with advantage because the deviations of the pipe from the nominal shape frequently vary more uniformly in the longitudinal direction than in the circumferential direction.

Any prior art means with the aid of which it is possible to measure the external cross-dimension and/or wall thickness of a tubular body may be used as measuring means. It is possible to measure the external cross-dimension for instance by means of a direct mechanical scanning, in which case the position of the scanning means is, for example, converted into an electric signal by means of a differential transformer.

When mechanical scanning is employed, damage may be caused to the outer wall of the pipe under unfavourable circumstances. This is avoided by the so-called indirect measuring methods. As an example of these, the capacitative, the pneumatic and the optical measuring method may be mentioned. The last-mentioned one also includes measuring by means of, for example, a laser interferometer.

For measuring wall thicknesses it is, for example, possible to employ the ultrasonic resonance method, the ultrasonic pulse resonance method, the ultrasonic pulse echo method or the inductive method, that is to say a method in which eddy currents are induced. The latter four methods can also be employed for measuring the external cross-dimension and, consequently, one of these methods is expediently used in the case shown in FIG. 1, where external cross-dimensions and wall thicknesses are measured with the same measuring means.

The measuring means may be expediently built into a measuring chamber inside a measuring head that can rotate around the measuring axis. The measuring chamber may possibly be sealed and filled with a liquid.

Claims

1. A method of mapping the cross-sectional dimensions of elongated tubular bodies by the use of measuring means along a measuring line fixed in relation to the measuring means and extending tranversely of the longitudinal axis of a tubular body, the method comprising the steps of: providing relative movement between the tubular body and the measuring means to successively bring the measuring means into positions corresponding to the cross-sectional dimensions to be measured, activating the measuring means to measure along the measuring line the distances from points fixed in relation to the measuring means to the external surface of the tubular body, activating the measuring means to measure the wall thicknesses of the tubular body corresponding to the points of external surface to which the distances were measured, calculating from the measured values thus determined the external cross-dimension of the tubular body by subtracting the distances from said points fixed in relation to said measuring means to said external surface from the distance between said two fixed points, calculating from the measured values thus determined the internal cross-dimension of the tubular body by subtracting the distances from said points fixed in relation to said measuring means to said external surfaces and said wall thicknesses from the distance between said two fixed points, and registering the values thus calculated.

2. A device for mapping the cross-sectional dimensions of elongated tubular bodies, comprising measuring means for the external non-contact measuring of dimensions, said measuring means positioned to measure, along a measuring line which is fixed in relation to the measuring means, the distances from fixed points on said measuring line to the surface of a tubular member intersecting said measuring line as well as the wall thickness of the tubular body in close proximity to the points of intersection, means for providing a relative movement of the tubular body and the measuring means such that the measuring line extends transversely of the longitudinal axis of the tubular body and is successively brought into positions corresponding to the cross-sectional dimensions to be measured, means to activate the measuring means to measure the distance from each of said measuring means to the surface of the tubular body and the wall thicknesses at the positions desired to be measured, means to calculate from the measured values thus obtained fromthe external and internal cross-dimensions of the tubular body, and means to register the values thus calculated.

3. A device as claimed in claim 2, wherein the measuring means are positioned to measure the correlated values of the distances from the fixed points to the surface of the tubular body and the wall thicknesses simultaneously along substantially the same measuring line.

4. A device as claimed in claim 2, further comprising means for briefly storing the measuring values first measured.

5. A device as claimed in claim 2, further comprising means for detecting the mutual angular position of the measuring means and the tubular body.

6. A method of mapping the cross-sectional dimensions of elongated tubular bodies by the use of ultrasonic measuring means located externally of and on diametrically opposite sides of a tubular body and along a measuring line fixed in relation to the measuring means and extending transversely of the longitudinal axis of a tubular body, the method comprising the steps of: providing an energy coupling medium capable of transferring ultrasonic energy; providing relative movement between the tubular body and the measuring means to successively bring the measuring means into positions corresponding to the cross-sectional dimensions to be measured with there being a helical path of relative movement between the tubular body and measuring means; activating the measuring means to impinge ultrasonic energy through said medium in a normal direction on the exterior surface of the tubular member, whereby said energy is reflected back from that exterior surface to the energy producing means to measure along the measuring line the distances from points fixed in relation to the measuring means to the external surface of the tubular body; activating the measuring means to impinge ultrasonic energy through said medium in a normal direction on the interior surface of the tubular member, whereby said energy is reflected back from the interior surface to the energy producing means to measure the wall thicknesses of the tubular body corresponding to the points of external surface to which the distances were measured; and converting the reflected energy into electrical signals, processing said electrical signals into signals proportional to the outside diameter and wall thickness of the tubular member including calculating from the measured values thus determined the external cross-dimension of the tubular body by subtracting the distances from said points fixed in relation to said measuring means to said external surface from the distance between said two fixed points, calculating from the measured values thus determined the internal cross-dimension of the tubular body by subtracting the distances from said points fixed in relation to said measuring means to said external surfaces and said wall thicknesses from the distance between said two fixed points and registering the values thus calculated.