This standard specifies the test method for detecting leaks in steel pipeline anti-corrosion coatings. This standard is applicable to the determination of leaks (such as pinholes, gaps, metal particles penetrating the anti-corrosion coating, etc.) or areas where the thickness is too thin in the anti-corrosion coating of steel pipelines. SY/T 0063-1999 Test method for leak detection of pipeline anti-corrosion coatingsSY/T0063-1999 Standard download decompression password: www.bzxz.net

1 Scope
Petroleum and Natural Gas Industry Standard of the People's Republic of China Test Method for Leakage Detection of Pipeline Anticorrosion Coating
Approval Department: State Administration of Petroleum and Chemical Industry Date of Approval: 1999-5-17
Effective Date: 1999-12-01
This standard specifies the test method for detecting leakage points of pipeline anticorrosion coating. SY/T0063—1999
Replaces SY0063—1992
This standard is applicable to the determination of leakage points (such as pinholes, gaps, metal particles penetrating the anticorrosion coating, etc.) or too thin thickness in the anticorrosion coating of steel pipelines.
2 Method Overview
2.1 This method is divided into Method A and Method B. Both Method A and Method B are based on the principle that leakage points or metal particles can form a low-resistance path and too thin points in the anticorrosion coating will produce electrical breakdown and send out alarms for detection. 2.2 Method A uses a low-voltage wet sponge leak detector with a DC voltage of less than 100V, which is only suitable for detecting leaks in the anti-corrosion layer with a thickness of 0.025~0.5mm. Method A is a non-destructive test and cannot detect the location where the anti-corrosion layer is too thin. 2.3 Method B uses a spark leak detector with a DC voltage of 900~~20000V, which is used to detect pipeline anti-corrosion layers of any thickness. Method B is a destructive test and can detect the location where the anti-corrosion layer is too thin. 3 Instruments
3.1 Low-voltage leak detector: A leak detection device with a DC voltage of less than 100V, equipped with a sponge electrode wetted by a conductive liquid, an audio signal generator, and a ground wire connected to the pipe wall.
3.2 Spark leak detector: A leak detection device with a DC voltage of 900~20000V, equipped with a detection electrode composed of a copper wire brush or other conductive material, an audio signal generator, and a ground wire connected to the pipe wall. 3.3 Peak voltmeter: A high-impedance voltmeter that can measure the peak value of a single pulse signal of a DC voltage. 4 Instrument calibration
4.1 Before the leak test, the leak detector should be calibrated with a peak voltmeter or oscilloscope according to the leak detection voltage value given in the instrument manual. 4.2 The sensitivity calibration of the low-voltage leak detector is to connect a 0.5W, 100kQ resistor in parallel to the instrument detection end. At this time, the leak detector should be able to trigger an alarm.
5 Test piece
The surface pretreatment and coating process of the test piece should be the same as those of the industrially produced anti-corrosion layer pipe, or a representative length of industrially produced anti-corrosion layer pipe should be selected.
6 Test steps of method A
6.1 Assemble the electrode rod and electrode according to the instruction manual of the low-voltage leak detector, and connect the ground wire to the metal pipe wall. 6.2 Connect the electrode clamp to the electrode rod, soak the sponge with conductive liquid, and then put the sponge into the electrode clamp and clamp it. When the thickness of the anti-corrosion layer is less than 0.25mm, ordinary tap water can be used; when the thickness of the anti-corrosion layer is between 0.25~～0.5mm, some wetting agent should be added to the tap water to allow the liquid to penetrate into the leak as soon as possible. 6.3 Connect one end of the detection electrode and the ground wire to the instrument respectively, and the other end of the ground wire is connected to the metal pipe wall. Use a wet sponge to contact the other exposed surface of the metal pipe. The instrument should send an audio signal, indicating that the leak detector is ready. When detecting leaks, the wet sponge should be moved close to the surface of the anti-corrosion layer. When the leak is found according to the audio signal, use the electrode tip to find the exact location of the leak. 6.4 When the low-voltage leak detector is in normal operation, the DC voltage between the sponge electrode and the metal pipe wall should not exceed 100V. 6.5 The surface of the anti-corrosion layer should be kept dry before leak detection. If the anti-corrosion layer is in an environment where electrolyte can form on its surface (such as salt spray), the surface of the anti-corrosion layer should be rinsed and dried before leak detection. When leak detection, the electrolyte should be at least 13 mm away from the metal pipe end or the exposed metal surface. 7 Test steps of method B
7.1 The leakage detection voltage is related to the thickness of the anti-corrosion layer and can be determined by formula (1) and formula (2). When the thickness of the anti-corrosion layer is less than 1 mm:
V=3294 VT
When the thickness of the anti-corrosion layer is greater than or equal to 1 mm:
V-7 843 /T.
Where: V—-leakage detection voltage peak value (V);
T. - thickness of the anti-corrosion layer (mm).
Note: The above formula is based on the voltage required to break through the air gap with the same thickness as the anti-corrosion layer. Therefore, it is only suitable for detecting pinholes, gaps and locations where the anti-corrosion layer is too thin, and is not suitable as a means of quality control of the thickness of the anti-corrosion layer. 7.2 The leakage detection voltage can also be determined by multiplying the insulation breakdown voltage of the anti-corrosion layer per millimeter by the minimum allowable thickness of the anti-corrosion layer (mm). Note: The insulation breakdown voltage of various anti-corrosion layers per millimeter can be determined by testing in the following way: gradually increase the leakage detection voltage on the anti-corrosion layer of known thickness and measure the voltage value when the leak detector just alarms. Divide this value by the known thickness of the anti-corrosion layer to obtain the insulation breakdown voltage value of the anti-corrosion layer per millimeter. 7.3 Connect the ground wire to the metal pipe wall, connect the other end of the ground wire to the leak detector, then connect the detection electrode to the leak detector, and then turn on the leak detector.
Note: Due to the high voltage involved, after the leak detector is turned on, the operator cannot touch the metal part of the ground wire and the detection electrode at the same time. 7.4 Move the detection electrode along the surface of the anti-corrosion layer for leak detection, and always keep the detection electrode in close contact with the surface of the anti-corrosion layer. When the detection electrode passes through the leak point of the anti-corrosion layer or the position where the thickness is too thin, the leak detector will alarm. At this time, the electrode can be moved back and the position of the leak point can be determined by observing the jump-out point of the electric spark.
7.5 During the leak detection process, the surface of the anti-corrosion layer must be kept dry, and the detection electrode must be kept at least 13mm away from the metal pipe end or the exposed metal surface. Www.bzxZ.net
8 Report
The leak test report shall be filled in according to the requirements of Appendix A (the appendix of the prompt), and its content shall include: 1. The complete mark of the test piece, that is, the name of the anti-corrosion layer, the diameter of the steel pipe, the thickness of the anti-corrosion layer and the technical standard number, the production date, the manufacturer and the product batch number.
Detection method (method A or method B), leak detector type, model and calibration method. 1. If method B is used, the leak detection voltage, the method for calculating the leak detection voltage and the minimum allowable thickness of the anti-corrosion layer (mm) shall be indicated. 9 Precision
9.1 Repeatability: When the same operator uses the same instrument to repeat the measurement on the same test piece, the allowable deviation of the measurement result is ±5%. 9.2 Reproducibility: When different operators use different instruments to test the same test piece under the same leakage detection voltage, the allowable deviation of the average result is ±10%.
Anti-corrosion layer manufacturer
Anti-corrosion layer name
Leak detector type
Leak detector calibration method
Calculation method of leakage detection voltage
Minimum allowable thickness of anti-corrosion layer
Test piece number
Inspector:
Inspection unit:
Inspection date:
Appendix A
(Suggested appendix)
Pipeline anti-brain layer Leak test report and data sheet Production date
Product batch number
Manufacturer
Test data of method A and method B Recommended record format of anti-corrosion layer thickness
Detection voltage
Detection method
Leak detector resistance
SY/T0063—1999
Report number
Number of leak points
Auditor
Steel pipe diameter
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