RU2822310C1 - Gas pipeline crack opening measurement method - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to the field of gas industry, to methods of diagnostic control of surface of steel products, in particular to determination of value of crack opening of elements of the main gas line. Method of measuring the value of crack opening in a gas pipeline involves installation of a sensor near the crack, recording readings, obtaining actual data on the value of crack opening. At the first stage of measurement, a sensor is calibrated, made in the form of a strain gauge located on a metal bracket, by fixing one of the control sites of the bracket on one of the crack faces and mechanical loading of this site with a given pitch, simulating the crack opening, after recording the readings, a table of the dependence of the readings of the strain gauge on the shift of the control sites under said action is formed. At the second stage, the sensor bracket is fixed with another control platform on the second face of the crack, the sensor readings are zeroed, then, gas pipeline is loaded with internal gas pressure. Actual data on value of crack opening are obtained after registration of sensor readings and their comparison with tabulated values.

EFFECT: improving measurement accuracy of crack opening in range of 10–500 mcm during bench tests of a gas pipeline.

1 cl, 5 dwg

Description

The invention relates to the field of the gas industry, namely to methods for diagnostic monitoring of the surface of steel products when determining their technical condition, and is intended to determine the magnitude of crack opening during bench tests of main gas pipeline elements.

When bench testing elements of a main gas pipeline, it is necessary to evaluate the magnitude of crack opening to determine the optimal operating mode that excludes the occurrence and development of defects, as well as to assess the wear resistance of gas pipeline elements.

There is a known method for measuring the size of crack openings in parts (SU 697804, publ. November 15, 1979), using a sensor made in the form of an elastic thread with spiral turns and a closed loop in the middle part. The sensor receives a signal from two copper plates rigidly attached to the sides of the crack. When a crack opens, the elastic thread stretches, unwinding the loop, thereby changing the active resistance of the sensor's sensitive element. Based on the change in resistance, the magnitude of the crack edge opening is judged. However, the known method does not take into account the nonlinear change in voltage across the active resistance of the sensor, and also does not calibrate the sensor to measure small changes in the opening value of crack edges (from 50 to 500 μm), which guarantees a high measurement error in this measurement range.

The closest to the claimed method is a method for measuring the length of a crack in building structures using sensors - strain gauges attached on both sides of the crack, in which the structural element is loaded and unloaded, the electrical resistance of the sensors is measured before and after loading and the length of the crack is calculated using a mathematical formula (RU 2596694 , published 09/10/2016).

The known method is intended for measuring crack opening values in building structures, where high measurement accuracy in microns is not required.

The disadvantage of the known method is the low accuracy of measuring changes in the opening values of crack banks in the range of 10 to 500 microns, therefore the known method cannot be used for bench testing of main gas pipeline elements when loaded with operating gas pressure.

The technical result is an increase in the accuracy of measuring the magnitude of crack opening in the range of 10-500 microns during bench tests of a gas pipeline.

A method is claimed for measuring the magnitude of the crack opening in a gas pipeline, which includes installing a sensor near the crack, recording sensor readings and obtaining actual data on the magnitude of the crack opening, characterized in that the measurements are carried out in two stages. At the first stage of measurement, the sensor is calibrated, made in the form of a strain gauge located on a metal bracket, by fixing one of the control platforms of the bracket on one of the edges of the crack and mechanically loading this site with a given step, simulating the opening of a crack; after recording the sensor readings, a table is formed dependence of the strain gauge readings on the displacement of the control areas under the specified impact. Then, at the second stage of measurement, the sensor bracket is fixed with another control platform on the second side of the crack, the sensor readings are reset, then the gas pipeline is loaded with internal gas pressure, and actual data on the size of the crack opening is obtained after recording the readings of the strain gauge and comparing them with the tabulated ones.

The order of operations allows you to pre-calibrate the strain gauge to monitor the deformation from pure bending that occurs in the working area of the sensor when the edges of a narrow crack open.

The fastening zone allows you to pre-fix the sensor to the gas pipeline to calibrate the strain gauge without deforming the crack on the object.

The method allows you to take into account the nonlinear change in voltage on the strain gauges of the sensor.

Preliminary calibration of the sensor allows you to eliminate the factor of measurement error due to a possible nonlinear change in the resistance of the sensor strain gauges when working on a gas pipeline under pressure. Under bench test conditions, it is possible to measure minimal changes in the opening value of crack edges, because The accuracy of measurements is due to preliminary calibration. Calibration of the sensor when measuring changes in the opening value of crack edges from 10 to 500 μm guarantees a minimum instrument error in this measurement range (±5 μm).

Making the sensor fastening element in the form of a metal bracket allows you to rigidly attach the sensor on the surface of the gas pipeline to the crack banks by welding, which contributes to high accuracy in measuring the opening value of the crack banks.

The method is illustrated by the following figures.

In fig. 1 shows a diagram of a device that implements the proposed method. fig. 2a - view A in Fig. 1, fig. 2b - view B in Fig. 1. In FIG. Figure 3 shows the placement of the micrometer during the calibration process.

In fig. Figure 4 shows a bridge electrical circuit for connecting the sensor strain gauges to the strain gauge station, which provided a standardized connection to the specialist’s computer, which records changes in the opening value of the crack edges.

In fig. 5, using a specific example, presents a table illustrating the dependence of the displacement of the sensor control pads on the deviation of the micrometer from the “zero” position under mechanical influence.

In fig. 1, 2, 3, 4 the following elements are presented:

1 - metal bracket;

2 - working areas of the sensor;

3 - legs of the bracket;

4 - places where the bracket bends;

5 - gas pipeline;

6 - control platform;

7 - control platform;

8 - gap between platforms 6 and 7,

corresponding to the width of the crack;

9 - crack banks;

10 - welding places;

11 - nut;

12 - bolt;

13 - micrometer;

14 - strain gauge R1;

15 - strain gauge R2;

16 - strain gauge R3;

17 - strain gauge R4;

18 - strain gauge;

19-24 - strain gauge station contacts;

25 - strain gauge station;

26 - USB interface;

27 - personal computer.

The method for carrying out the invention is shown in the specific example described below.

A bench test was carried out on a main gas pipeline 10 m long, on which a crack was discovered (crack length - 20 mm, width - 0.3 mm, depth - 2 mm).

During the test, a measuring device was used, consisting of a bracket 1 and a strain gauge 18, including strain gauges 14, 15, 16, 17, switched and connected to a strain gauge station 25 (Fig. 5).

At the calibration stage, strain gauges 14, 17 and 15, 16 were installed on the working areas 2 of the sensor 18, as shown in FIG. 2a and 2b. Bracket 1 was secured with a control platform 6 on one of the sides 9 of the crack by welding. A micrometer 13 is installed on a loose control platform 7 (Fig. 3). A nut 11 was welded over the platform 7 of the bracket 1, a bolt 12 was screwed into it and turned until it stops in the platform 7. The threaded connection ensured the fixation of the fasteners and made it possible to regulate the degree of mechanical impact on the loose platform 7 of the bracket 1. The gap between platforms 6 and 7 was 0.3 mm.

Bolt 12 exerted pressure on the loose platform 7, displacing it towards micrometer 13, creating bending deformation in the working area 2, thereby simulating the opening of crack edges 9. This displacement was made in steps of 10 μm. For each displacement step, strain gauge station 25 recorded changes in the readings of strain gauges 14, 15, 16, 17 of sensor 18. After this, a sensor calibration table was formed, which displayed the correspondence of the displacement of pads 6 and 7 relative to each other, expressed as the deviation of micrometer 13 from “zero” position (μm) and changes in sensor 18 readings due to bending deformation resulting from displacement of these pads.

After the calibration stage was completed, the micrometer 13 was removed from the platform 7, for which the bolt 12 was removed from the nut 11. The platform 7 was welded to the second side 9 of the crack opening. The readings of strain gauge 18 were reset to zero and accepted as the initial “zero”.

During bench tests of the pipeline when it was loaded with operating gas pressure, the readings of sensor 18 were recorded, which were then compared with the values obtained at the calibration stage (Fig. 5. Table). Based on this information, the actual value of the opening value of crack banks 9 was formed during bench tests of the pipeline.

Bench tests were carried out with 4 stages of increasing gas pressure inside the gas pipeline. At the zero stage, the pressure inside the pipe was equal to atmospheric pressure. At the first stage, the pressure was raised to 3 MPa, at the second - to 6 MPa, at the third - to 9 MPa, and at the fourth - to 12 MPa.

At the first stage, the value on sensor 18 was set to 19 units, at the second stage - 38 units, at the third stage - 57 units, at the fourth stage - 82 units. Thus, based on the linearly proportional relationship between the readings of the strain gauge 18 and the opening value of the crack edges 9, we can conclude that the change in the readings of the sensor 18 over the 4 test stages was 82 units, which indicated the opening of the crack edges by 13 μm . Information from the strain gauge 18 via the USB interface 26 was transferred to the operator's personal computer 27, which recorded changes in the opening value of the crack edges.

Claims (1)

A method for measuring the amount of crack opening in a gas pipeline, including installing a sensor near the crack, recording sensor readings and obtaining actual data on the amount of crack opening, characterized in that the measurements are carried out in two stages; at the first stage of measurement, the sensor is calibrated, made in the form of a strain gauge located on a metal bracket, by fixing one of the control platforms of the bracket on one of the crack edges and mechanically loading this site with a given step, simulating the opening of a crack, after recording the sensor readings, a table is formed depending on the readings of the strain gauge on the displacement of the control platforms under the specified impact, then on the second At the measurement stage, the sensor bracket is fixed with another control platform on the second side of the crack, the sensor readings are reset, then the gas pipeline is loaded with internal gas pressure, and actual data on the size of the crack opening is obtained after recording the readings of the strain gauge and comparing them with the tabular ones.