SU1767456A1 - Device for checking continuity of insulating coating of metal objects - Google Patents

Abstract

Use: The invention relates to electric-spark flaw detection and can be used to control the integrity of insulating coatings of metal objects. Summary of the Invention: By providing an automatic voltage variation on the device probe depending on the coating thickness by introducing an outer mechanically connected probe of the thickness of the coating thickness and the interface unit to the voltage control unit, the likelihood of a dielectric coating is reduced and the control is more reliable. The device contains series-connected direct current source 1, voltage converter 3, voltage regulating unit 4, high-voltage generator 5 and probe 6 connected to its output circuit, spark probe detector 7, coating defect indicator 8, coating thickness sensor 18, and node 17 mates 1 il.

Description

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WITH

The invention relates to electric spark detection and can be used to control the continuity of insulating (dielectric) coatings of metal objects.

The purpose of the present invention is to increase the reliability of monitoring the continuity of coatings and reducing the likelihood of their electrical breakdown during the monitoring process.

The invention is explained using the functional diagram of the device shown in the drawing.

The device contains a power source 1, to which a voltage converter 3 is connected through switch 2, to its output through voltage regulating unit 4, an high-voltage generator 5 is connected, to the output circuit of which a probe 6 (in this case, a ring) is connected and an electric detector 7 a sample, to the output of which a coating defect indication unit 8 is connected,

The high voltage generator 5 contains a high voltage pulse transformer 9, a storage capacitor 10, a current limiting element 1T and a thyristor 12, the control electrode of which is connected to the output of the pulse generator 13.

The coating control unit 14 comprises a control transistor 14 and resistors 15 and 16 in its base and emitter circuits, which are used to stabilize the operation mode of the transistor. The base of the transistor 14 is connected through the junction 17 to the output of the coating thickness sensor 18, which is mechanically connected with the probe 6 and has the ability to move along with it over the surface of the test coating 19 by means of the pull 20 and crosshead 21. The metal base of the test object 22 ( in this case, the pipe) has an electrical

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connection with the output of the high voltage transformer 9, which is carried out directly or through an intermediate link, for example, ground.

The proposed device works as follows.

A probe b and, together with it, a coating thickness sensor 18 are pressed against the controlled coating 19 and are moved along it with a speed limited by the dynamic characteristics of the flaw detector. Before moving the probe 6, the flaw detector is switched on by the switch 2. At the output of the converter 3, a voltage is generated, a certain part of which (see below) is applied to the storage capacitor 10, which is charged to the specified voltage. When the triggering thyristor 12 triggers a pulse from the generator 13 output to the control electrode, the capacitor 10 is discharged from the primary winding of the high-voltage transformer 9, resulting in a high voltage pulse applied between its probe and the base of the test object 22 on its secondary winding. Charging processes And the discharge of the storage capacitor 10 is repeated at intervals determined by the pulse frequency output from the generator 13. Accordingly, at the output of the high-voltage transformer Matora 9 and b is formed on the probe high-voltage pulse voltage with the same pulse repetition frequency.

The voltage across the probe (pulse amplitude) can be expressed by the relation:

)

where Ksch - voltage on the probe 6, kV;

Uc is the voltage across the storage capacitor 10. kV;

n - transformation ratio of Transformat 9;

С - capacitance of storage capacitor 10, microfarad;

Ssch - capacitance probe 6, microfarad.

Under an easily enforceable condition, expressed as: C Sshch.p2

(2)

the ratio / 1 / can be simplified and presented as

looking for Uc.n, (3)

Further, we can write the obvious correlations:

Uc UCT Ue KyctA.RBx. (4)

Ld-Cd T, (5)

where UCT is the voltage at the output of the control unit 4, kV;

1) b - voltage at the base of a 14. kV transistor; Cous is the gain factor of node 17;

1D is the output current of the coating thickness sensor 18, mA;

RBX - input impedance node 17, kOm;

CD is the conversion factor of the sensor 18 for thickness, mA / mm;

T is the thickness of the coating, mm.

From (3), (4) and (5) follows

looking for Kus.KdNVkh.T Kg.T, (6)

where К5 Кус.КдНвх is the total conversion coefficient of the flaw detector, kV / mm.

Consequently, the voltage value on the probe of the proposed electric-spark flaw detector turns out to be proportional to the thickness of the test coating. On the other hand, in order to locate the point of discontinuity in a controlled coating, the condition expressed by the relation: look for En.T, (7)

where Yong is the specific value of the voltage across the probe, normalized in the standard documentation, kV / mm (usually, 4-5 kV / mm);

From (6) and (7) follows

or

(eight)

KЈ - Kus.Kd.RdH - Ec. (9)

Thus, when the easily realizable condition, expressed by the ratio / 9 /, is fulfilled, the value of the electrical voltage of the air gap is automatically set on the probe of the proposed electrospark flaw detector.

between the probe b and the metal base of the test object 22 in the areas of discontinuity of the test coating 19. When such a breakdown occurs, an electrical output is formed at the output of the detector 7

the signal arriving at the input of the display unit 8, where it is recorded as a detected defect in the coating.

With all changes in coating thickness, the direction of the flaw detector probe will automatically change accordingly, remaining at the level of regulatory requirements. This dramatically reduces the likelihood of electrical breakdown of the monitored coating.

The use of the proposed electrospark flaw detector will allow to obtain a significant technical and economic effect by increasing the reliability of monitoring the integrity of the insulation coatings.

Claims (1)

metal objects and reduce the likelihood of their electrical breakdown. Apparatus of the Invention A device for monitoring the continuity of an insulating coating of metal objects, comprising a DC power source, a voltage converter, a voltage control unit, a high-voltage generator, a pulse generator, a probe, an electrical breakdown detector, and a coating defect display unit, the power source connected to A converseoathemep, the output of which is connected through a voltage control unit to the first input of a high-voltage generator, the second input of which is connected to the output pulse generator house, high-voltage generator output through a detector the electrical sample is connected to the probe, and the output of the electrical sample detector is connected to the input of the coating defect indication unit, characterized in that the purpose of increasing the reliability of control and reducing the likelihood of electrical coating sample, sensor inserted coating thickness and interface, and the coating thickness sensor is mechanically connected to the probe and connected to the voltage control unit via the interface unit. / // /