SU1682761A1 - Method of inspection of metallic tube geometrical parameters - Google Patents

Abstract

This invention relates to a measurement technique. The goal is to increase the information content of the method for controlling the geometric parameters of a metal pipe by determining not only the diameter and longitudinal thickness variation of the pipe, but also its transverse thickness variation. When implementing the method, current electrodes connected to an AC power source are placed along the pipe surface and an electrical conductive sheath is placed between them, separated by dielectric inserts into longitudinal electrically insulated one from another conductive areas. They place a pair of potential electrodes connected through a switch to a measuring device, such as a voltmeter. The changes in the diameter and longitudinal thickness of the pipe are monitored by the potential difference across the electrodes installed along one longitudinal section of the shell, and the transverse difference in the thickness of the pipe is determined by the potential difference across these electrodes when they are installed on different conductive parts of the core. 1 h. the item of f-ly, 4 ill. cl

Description

The invention relates to a measurement technique and can be used to measure the geometrical parameters of metal pipes during their manufacture.

The purpose of the invention is to increase the informativity of the method of controlling geometric parameters by determining not only the diameter and thickness variation of the walls of metal pipes along their length, but also the thickness variation of the pipes along their perimeter, i.e., providing control of changes in wall thickness in the cross section of the pipe.

FIG. 1 shows a device for implementing the method; in fig. 2 is a section A-A in FIG. one; in fig. 3 and 4 are experimental dependences of the relative change in the measured potential difference A Do and Alls as a function of the diameter D and the thickness S of the pipe walls, respectively.

A device for implementing a method for monitoring geometrical parameters of an electrically conductive pipe contains an AC power supply 1 connected to a pair of current electrodes 2 and 3 installed during the measurement along the outer surface of the pipe 4 being monitored and made in the form of closed rings.

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small air gap from the pipe surface. Between them, an electrically conductive sheath 5 is placed, divided by dielectric inserts 6 along its length into electrically insulated areas.

In this area, during the measurement process, one or several pairs of potential electrodes 7 and 8 connected via a switch 9 to a measuring device, such as an AC voltmeter, are placed.

The method is carried out as follows.

A pair of current electrodes 2 and 3 are placed along the outer surface of the monitored section of the pipe 4, connected to the AC power supply 1, an electrically conductive sheath 5 with a pipe 4 placed inside it is placed and selectively connected to the current electrode 3. The potential electrodes 7 and 8 are placed on the surface of the corresponding electrically conductive part of the shell 5 and the potential difference across them is measured. When potential electrodes 7 and 8 are mounted along the conductive portion of this envelope, the potential difference on them depends on the diameter of the pipe in the monitored section, and consequently, on the pipe thickness thickness along its length. When installing a pair of potential electrodes 7 and 8 on different conductive areas of an external electrically conductive sheath 5 (Fig. 2) around the perimeter of pipe 4, the measured potential difference per pair of potential electrodes 7 and 8 depends on the transverse thickness difference of the pipe.

If pipe 4 has an increase in wall thickness S local around the perimeter, then an increase in electric current in this section of the pipe causes an increase in potential difference in the corresponding section of conductive sheath 5 due to the influence of the capacitive effect between the two conductive bodies flowing around the electric current.

If the pipe has a local increase in diameter D on its section, under the corresponding electrically conductive section of the shell 5, on which potential electrodes 7 and 8 are placed during the measurement, due to the reduction in the gap between these sections, an increase in the potential difference on these electrodes occurs (Fig. 3 ) by enhancing capacitive coupling between them.

As shown in FIG. 3 and 4

functional dependencies between the change in the electric potential drop and the outer diameter D of the pipe or the thickness S of its wall, as experiments have shown, have a different character;

allows to separate the influence of these parameters on the result of measuring the potential difference.

The absence of mechanical contact between the measuring means used in the implementation of this method and the pipe being monitored allows it to be used to control the pipes in the course of their production.

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Claims (2)

1. A method for monitoring the geometrical parameters of a metal pipe, which consists in placing a pair of current electrodes along the outer surface of the pipe, connecting them to an alternating current power source, and using a pair of potential electrodes, measuring the potential difference, which determines the geometrical parameter that is different the fact that, in order to increase the information content of the control by determining the difference in thickness of the pipe also along its perimeter, the controlled pipe is placed in an external electric A shell, separated by dielectric inserts along its length, into electrically insulated sections from one another, places the shell between current electrodes and selectively connects its sections to one of the current electrodes, potential electrodes are placed on the surface of the corresponding section of the shell and by potential difference to them when installed along the wire the outer diameter and thickness of the pipe along its length, and the potential difference across a pair of potential electrodes when they are installed ke in different areas of external The conductive sheath determines the thickness variation of the pipe along its perimeter. 2. Method of claim 1, characterized in that current electrodes made in the form of closed rings are installed with a gap relative to the surface of the pipe. Ј Matt iOl-ff Oi Z SO l OO Z 96 i  iiii N0v / 7F J7 V-v 19IZ891 Mb /, 3t f, 0-0.70, 150№0.25 1