This standard specifies an experimental method for non-destructive measurement of the dry film thickness of the non-magnetic anti-corrosion layer on the outer surface of steel pipes. This standard is applicable to the measurement of anti-corrosion layers with a diameter of not less than 13 mm and a thickness of less than 6 mm. This standard is not suitable for measuring anti-corrosion layers that are too soft or easily deformed under pressure. SY/T 0066-1999 Non-destructive measurement method for thickness of anti-corrosion layer of steel pipes (magnetic method) SY/T0066-1999 Standard download decompression password: www.bzxz.net

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Petroleum and Natural Gas Industry Standard of the People's Republic of China Non-destructive Measurement Method for Thickness of Anticorrosion Layer on Steel Pipe (Magnetic Method)
Approval Department: State Administration of Petroleum and Chemical Industry Date of Approval: 1999-05-17
Implementation Date: 1999-12-01
SY/T 0066—1999
Replaces SY0066-1992
This standard specifies a test method for non-destructive measurement of the thickness of non-magnetic anticorrosion layer on the outer surface of steel pipeline. This standard is applicable to the measurement of anticorrosion layer with a diameter of not less than 13mm and a thickness of less than 6mm on steel pipes. This standard is not applicable to the measurement of anticorrosion layer that is too soft or easily deformed under pressure.
Cited Standards
The provisions contained in the following standards constitute the provisions of this standard by reference in this standard. When this standard is published, the versions shown are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest version of the following standards. GB/T700-1988 Carbon structural steel
3 Method overview
3.1 This method uses a non-destructive measuring instrument to measure the thickness of the anti-corrosion layer based on the change in magnetic flux or magnetic attraction between the probe and the magnetic substrate metal.
3.2 Non-destructive measurement of the thickness of the anti-corrosion layer is a basic standard in the series of standards for pipeline anti-corrosion layers. Appropriate thickness of the anti-corrosion layer is important for preventing or slowing down the corrosion of the pipeline. 3.3 The accuracy of the thickness measurement may be affected by the deformability of the anti-corrosion layer. This method is not suitable for anti-corrosion layers that are easily deformed under the force applied by the probe of the measuring instrument.
4 Instrument
4.1 This method uses a non-destructive measurement thickness gauge that can be calibrated within a given range of use. The instrument can be calibrated based on the change in magnetic flux or magnetic attraction between its probe and the steel substrate to indicate the thickness of the anti-corrosion layer. 4.2 The selected thickness gauge should be suitable for measuring the dry film thickness of non-magnetic anti-corrosion layers on flat or curved magnetic substrates. 5.1 Before using the instrument, it should be calibrated with a standard sheet of appropriate thickness in accordance with the provisions in the manufacturer's instructions. During the use of the instrument, it should be calibrated once every period of time. 5.2 The non-magnetic standard sheet with uniform thickness used for calibration can be a foil or a standard coating sheet of known thickness, which can be provided by the instrument manufacturer or purchased by yourself.
5.2.1 Foil (thin sheet): The thickness of the foil should be close to the estimated value of the thickness of the anti-corrosion layer to be measured. The foil should be placed on a smooth, clean, low-carbon steel substrate and kept in close contact. Use a single layer of foil as much as possible and replace it frequently because it is easy to produce indentations. Foil is suitable for calibration on curved surfaces.
SY/T0066-1999
Note: The magnetic field of the probe of some instruments has an effective penetration thickness. When the substrate thickness exceeds the critical value, it will not affect the instrument measurement. The critical thickness is related to the instrument and the substrate and can be determined through experiments. 5.2.2 Standard coating sheet: This calibration standard sheet is a non-magnetic anti-corrosion layer of known thickness permanently attached to a 8mm thick low-carbon steel plate. The steel plate should comply with the provisions of Q215 in GB/T700-1988. The thickness of the anti-corrosion layer should be as close as possible to the estimated value of the thickness of the anti-corrosion layer to be measured.
Note: If the curvature of the anti-corrosion layer to be measured is relatively large and it is impossible to use a plane calibration, the foil should be closely attached to a substrate with the same curvature as the anti-corrosion layer to be measured for calibration.
6 Steps
6.1 Operate the instrument according to the manufacturer's instructions. 6.2 Measure each pipe 3 times along the top surface at equal intervals, then rotate the pipe 3 times, each time by 90°, and measure 3 times at equal intervals after each rotation, record 12 anti-corrosion layer thickness data, and obtain the average, minimum and maximum values. Note:
①) When using a bipolar probe, the two poles should be located on the same plane of the anti-corrosion layer surface. ② If the anchor pattern depth on the metal surface of the pipeline is greater than 25% of the thickness of the anti-corrosion layer, its impact on the measurement accuracy must be considered. ③ Without damaging any anti-corrosion layer material, remove dust and grease with appropriate methods. ① The measuring instrument and the measuring method are related to the operator's skills. For example, the pressure applied to the probe and the rate of applying the balancing force are different for different people. Calibration and measurement by the same operator, or the use of a constant pressure probe, can reduce or eliminate this effect. The probe must be placed in a position perpendicular to the surface of the measuring point. If it is used in a horizontal or inverted position, it should be calibrated in this position. ? Magnetic instruments are sensitive to measurement speed, so when using them, the measuring speed of the probe must not affect the thickness reading. 7 Report
The report should include the following:
Name and technical standard number of the anti-corrosion layer
—…pipe size, manufacturer, pretreatment method of the pipe surface, anchor pattern depth and production batch number;…—name, model and calibration method of the thickness gauge;—number of thickness measurements and the average, minimum and maximum values ​​of the measured data. 8 Precision
8.1 Repeatability: When the same operator uses the same instrument to measure the same test piece, the allowable deviation between the results is ±5%. 8.2 Reproducibility: When different operators use different instruments to measure standard pieces of known thickness, the maximum allowable deviation between the average result and the thickness of the standard piece is 10%.
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