This standard is applicable to the on-site test of cathodic protection parameters of pipeline outer wall. SY/T 0023-1997 Test method of cathodic protection parameters of buried steel pipelinesSY/T0023-1997 Standard download decompression password: www.bzxz.net

1 General Test
Petroleum and Natural Gas Industry Standard of the People's Republic of China Cathodic Protection of Buried Steel Pipelines
Parameter Test Method
Approval Department: China National Petroleum Corporation Approval Date: 1997-12-31
Implementation Date: 1998-07-01
SY/T 0023-1997
Replaces SYJ23---1986
1.0.1 This standard is formulated to unify the field test methods of cathodic protection parameters of the outer wall of buried steel pipelines (hereinafter referred to as pipelines) and make the test data accurate and reliable.
1.0.2 This standard is applicable to the field test of cathodic protection parameters of the outer wall of pipelines. 2 Terminology
2.0. 1 Pipeline-earth electrical potentia! The potential difference between the pipeline and its adjacent soil.
2.0.2 Surface reference method surface reference electrode method A method of placing a reference electrode on the ground near the pipeline to be tested to test the ground potential of the pipeline. 2.0.3 Reference electrode method close to pipeline A method of placing a reference electrode in the soil close to the pipeline to test the ground potential of the pipeline. 2.0.4 Reference electrode method remote from pipeline A method of placing a reference electrode on the ground far away from the pipeline to test where the ground potential tends to zero to test the ground potential of the pipeline. 2.0.5 Auxiliary electrode method A method of testing the protection potential of a test piece connected to the pipeline, with a certain exposed area and the same material as the pipeline, to simulate the protection potential of the pipeline. 3 Basic provisions
3.0.1 The test instrument must have a display speed and accuracy that meet the test requirements, and should also be easy to carry, low power consumption, and adaptable to the test environment. The test instrument used must be calibrated in accordance with the relevant provisions of the current national standards. 3.0.2 In order to improve the accuracy of the test, it is advisable to use a digital instrument. 3.0.3 Principles for selecting a DC voltmeter:
1 The internal resistance of a pointer voltmeter should be no less than 100k/V; the input impedance of a digital voltmeter should be no less than 1Mα. 2 The sensitivity (resolution) of the voltmeter should meet the voltage value being measured, and should have at least two significant digits; when there are only two significant digits, the first digit must be greater than 1.
3 The accuracy of the voltmeter should not be lower than level 2.5. 3.0.4 Principles for selecting a DC ammeter:
The internal resistance of the ammeter should be less than 5% of the total internal resistance of the current loop being measured. 1
2 The sensitivity threshold (resolution) of the ammeter should meet the current value being measured, and should have at least two significant digits; when there are only two significant digits, the first digit must be greater than 1.
3 The accuracy of the ammeter should not be lower than level 2.5. 842
SY/T 0023—1997
3.0.5 When testing the pipe-to-ground potential, a copper-saturated copper sulfate electrode (hereinafter referred to as copper sulfate electrode, code name CSE) should be used as the reference electrode. Its manufacturing materials and use must meet the following requirements: 1 The copper electrode uses red copper wire or rod (purity not less than 99.7%). 2 Copper sulfate is chemically pure, and saturated copper sulfate solution is prepared with distilled water. 3 The permeable membrane uses microporous materials with high permeability, and the outer shell should use insulating materials. The allowable current density flowing through the copper sulfate electrode is not more than 5μA/cm2. 4
3.0.6 All test connection points must ensure good electrical contact. The measuring wire should use copper core insulated soft wire; in areas with electromagnetic interference (such as near high-voltage transmission lines), shielded wires should be used. 3.0.7
The test instrument must be operated in accordance with the relevant provisions of the instrument instruction manual. 3.0.8
4 Pipe-to-ground potential test
4.1 Surface reference method
4.1.1 The surface reference method is mainly used to test parameters such as pipeline natural potential, sacrificial anode open circuit potential, and pipeline protection potential. 4.1.2 The test wiring diagram of the surface reference method is shown in Figure 4.1.2. A digital voltmeter should be used. 4.1.3 Place the reference electrode on the moist soil on the surface within 1m above the top of the pipeline. Good electrical contact between the reference electrode and the soil should be ensured.
4.1.4 Adjust the voltmeter to an appropriate range, read the data, make a record, and indicate the name of the potential value. 4.2 Near reference method
4.2.1 The near reference method is generally used to test the protection potential of pipelines with poor anti-corrosion layer quality and the closed circuit potential of sacrificial anodes. 4.2.2 Dig a test pit for placing the reference electrode above the pipeline (or sacrificial anode) about 1m away from the test point, and place the reference electrode on the soil 3~~5cm away from the pipe wall (or sacrificial anode), as shown in Figure 4.2.2. 4.2.3 Test and record according to 4.1.4. CSE
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Figure 4.1.2 Schematic diagram of test wiring for surface reference method Schematic diagram of test wiring for near reference method
Figure 4.2.2
4.3 Remote reference method
4.3.1 The remote reference method is mainly used for forced current cathodic protection of pipe sections affected by the auxiliary anode ground electric field and pipe sections near the sacrificial anode buried point, measuring the potential of the pipeline to the distant earth to calculate the negative offset potential value of the point. 4.3.2 The wiring diagram of the remote reference method is shown in Figure 4.3.2. 4.3.3 Place the copper sulfate reference electrode on the ground surface one by one in the direction away from the ground electric field source. The first placement point is not less than 10m away from the pipeline test point, and then move 10m one by one. Use a digital multimeter to test the pipeline ground potential according to 4.1.4. When the difference between the pipeline ground potentials tested at two adjacent placement points is less than 5mV, the reference electrode will no longer move far away, and the farthest pipeline ground potential value is taken as the potential value of the pipeline at the test point to the distant earth.
SY/T 0023—-1997
4.4 Power-off method
1—Auxiliary anode or sacrificial anode; 2--Pipeline; 3—Test pile; 4 Digital multimeter; 5—Reference electrode (CSE) Figure 4.3.2 Wiring diagram of remote reference method test 4.4.1 In order to eliminate the IR drop effect in the cathodic protection potential, the power-off method should be used to test the protection potential of the pipeline. 4.4.2 The power-off method is implemented through a current interrupter, which should be connected in series to the output terminal of the cathodic protection current. 4.4.3 During the non-test period, the cathodic protection station is in a continuous power supply state; during the test of the pipeline protection potential or the external anti-corrosion layer resistance, the cathodic protection station is in an intermittent working state of supplying power to the pipeline for 12 seconds and cutting off power for 3 seconds. All cathodic protection stations in the same system must be synchronized during intermittent power supply, and the synchronization error should not exceed 0.1s. The potential measured by the surface reference method during the 3s power outage is the pipeline protection potential where the reference electrode is placed.
4.5 Auxiliary electrode method
4.5.1 A test piece made of the same material as the pipeline is used as an auxiliary electrode. Except for a 10mm diameter exposed hole in the center of one side, the rest of the piece is covered with an anti-corrosion layer and buried in the soil below the permafrost line near the pipeline. When burying, the exposed hole faces upwards, and after covering with 1-2cm of fine soil, the bottom of the long-acting copper sulfate electrode is placed directly above the exposed hole, and then backfilled to the ground level. The wires of the auxiliary electrode and the long-acting copper sulfate electrode are connected to their respective wiring posts in the test pile, and the auxiliary electrode wiring posts are short-circuited with copper sheets or copper wires to the wiring posts of the pipeline lead-out wires in the test pile. 4.5.2 Use a digital multimeter to regularly test the potential difference between the auxiliary electrode and the long-acting copper sulfate electrode. When there is cathodic protection, the potential difference represents the pipeline protection potential at this point.
5 Sacrificial anode output current test
5.1 Standard resistance method
5.1.1 The wiring diagram of the standard resistance method test is shown in Figure 5.1.1. 5.1.2 The two current terminals of the standard resistor are connected to the terminals of the pipeline and the sacrificial anode respectively, and the two potential terminals are connected to the digital multimeter respectively, and the digital multimeter is set to the DC200mV range. The total length of the access wire shall not exceed 1m, and the cross-sectional area shall not be less than 2.5 mm2.
5.1.3 The resistance of the standard resistor shall be 0.1Ω, and the accuracy shall be 0.02 level. 5.1.4 The output current of the sacrificial anode shall be calculated according to the following formula. 1
Wherein: I--
Sacrificial anode (group) output current (mA)-digital multimeter reading (mV);
R--standard resistor value (Ω).
5.2 Direct measurement method
5.2.1 The wiring diagram of the direct measurement method is shown in Figure 5.2.1. 844
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R--standard resistor; V-digital multimeter; X-sacrificial anode Figure 5.1.1 Standard resistance method test wiring diagram SY/T 0023-1997
A-4-digit digital multimeter; X--sacrificial anode Figure 5.2.1 Direct measurement method wiring diagram
5.2.2 The direct measurement method should use a 5-digit reading (4<digit) digital multimeter, and use the DC10A range to directly read the current value. 6 Current test in pipe
6.1 Voltage drop method
6.1.1 For pipelines with good external anti-corrosion layer, when the tested pipe section has no branch pipes and no grounding electrodes, and the pipe diameter, wall thickness, and material resistivity are known, the DC current flowing along the pipeline is tested according to Figure 6.1.1. 6.1.2 Measure the pipe length Lab between points a and b, and the error is not greater than 1%. The minimum length of La should be determined according to the pipe diameter and the current in the pipe. The minimum pipe length should ensure that the potential difference between points a and b is not less than 50uV, and Lab is generally taken as 30m. 6.1.3 First use a digital multimeter to determine the positive and negative polarity of points a and b and roughly measure the V value. Then connect the positive and negative terminals to the corresponding terminals of the "unknown" terminal of the UJ-33a DC potentiometer, and carefully measure the V value. 6.1.4 The current in the ab section of the pipe is calculated according to the following formula. In the formula:}-
The current flowing through the ab section of the pipe (A);
The potential difference between ab (V)
Outer diameter of the pipe (mm);
-Pipeline wall thickness (mm);
Pipeline resistivity (2mm2/m);
The length of the pipe between ab (m).
Vab : Yuan (D -- 8)8
6.2 Compensation method
6.2.1 For pipelines with good external anti-corrosion layer, when the measured pipe section has no branch pipes and no grounding electrodes, and the DC current flowing in the pipe is relatively stable, the compensation method can be used to measure the current in the pipe. The wiring diagram of the compensation method is shown in Figure 6.2.1. UJ-33a
Figure 6. 1. 1
Wiring diagram of voltage drop method test
Wiring diagram of compensation method test
SY/T0023—--1997
6.2.2 In Figure 6.2.1, La≥Yuan D, Lb≥Yuan D, and the length of La should be 20 to 30 m. 6.2.3 Connect the test circuit according to Figure 6.2.1, close the switch K, and adjust the rheostat R. When the indication of the galvanometer or potentiometer G is zero, the value indicated by the ammeter A is the absolute value of the current I in the pipe. 7 Insulation performance test of insulating flange (joint) 7.1 Megaohmmeter method
7.1.1 The insulation resistance value of the insulating flange (joint) that has been manufactured but not yet installed on the pipeline is measured by the megohmmeter method. 7.1.2 As shown in Figure 7.1.2, it is advisable to use a magnetic joint (or clamp) to crimp (clamp) the measuring wire at the input end of the 500V megohmmeter to the bare pipe on both sides of the insulating flange (joint) (the connection point must be rust-free), turn the megohmmeter handle to the specified speed, and continue for 10S. At this time, the resistance value indicated by the megohmmeter stably is the insulation resistance value of the insulating flange (joint). 7.2 Potential method
7.2.1 The insulation performance of the insulating flange (joint) that has been installed on the pipeline can be judged by the potential method. 7.2.2 As shown in Figure 7.2.2, before the protected pipeline is energized, use a digital multimeter V to test the pipe-to-ground potential Va of the non-protected side a of the insulating flange (joint); adjust the cathodic protection power supply so that the pipe-to-ground potential V at point b on the protected side reaches between -0.85 and 1.50V, and then test the pipe-to-ground potential Va2 at point a. If Va and Va2 are basically equal, the insulation performance of the insulating flange (joint) is considered to be good; if /Va2l>/VI and Va2 is close to the value, the insulation performance of the insulating flange (joint) is considered to be questionable. If the auxiliary anode is far enough from the insulating flange (joint), and it is determined that the pipeline connected to the non-protected side is not close to or crosses the pipeline on the protected side, it can be determined that the insulation performance of the insulating flange (joint) is very poor (serious leakage or short circuit); otherwise, further testing should be performed according to the method in 7.3. ytit
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1---Insulating support; 2-Insulating flange (joint) Figure 7.1.2 Schematic diagram of megohmmeter test wiring 7.3 Leakage resistance test method
Figure 7.2.2 Schematic diagram of potential test wiring
7.3.1 When the insulation performance of the insulating flange (joint) installed on the pipeline is questionable by the potential test, the leakage resistance or leakage percentage test should be carried out according to the test wiring diagram shown in Figure 7.3.1. 7.3.2 The steps of the leakage resistance test of the insulating flange (joint) are as follows: 1 Connect the test circuit according to Figure 7.3.1, where the horizontal distance between a and b shall not be less than D, and the length of the bc section should be 30m. Adjust the output current of the forced power supply E to 11 so that the pipeline on the protection side reaches the cathodic protection potential value. 2
Use a digital multimeter to measure the potential difference △V between d and e on both sides of the insulating flange (joint). 3
Test the current I2 of the bc section according to the method shown in 6.1. 4
Read the cathodic protection current I1 provided by the forced power supply to the pipeline. 5
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Figure 7.3.1 Schematic diagram of leakage resistance test wiring 7.3.3 The leakage resistance of the insulating flange (joint) is calculated according to the following formula. RH
Where: RH—insulating flange (joint) leakage resistance (Q); △V--——potential difference on both sides of the insulating flange (V); I--—·Output current of the forced power supply E (A); I2——the current in the pipe of the bc section (A).
— I2
7.3.4 The leakage percentage of the insulating flange (joint) is calculated according to the following formula. 1=×100
Leakage percentage——
SY/T0023—1997
（7.3.4）
7.3.5 If the test result is I.1, it is considered that the leakage resistance of the insulating flange (joint) is infinite, the leakage percentage is zero, and the insulation performance of the insulating flange (joint) is good.
8 Grounding resistance test
8.1 Auxiliary anode grounding resistance test
8.1.1 The auxiliary anode grounding resistance is tested by a grounding resistance measuring instrument. The test wiring diagram is shown in Figure 8.1.1. 1 When using Figure 8.1.1 (a) for testing, in areas with relatively uniform soil resistivity, di: takes 2L and dz takes L; in areas with uneven soil resistivity, d1; takes 3L and di2 takes 1.71. During the test, the potential electrode moves three times along the line connecting the auxiliary anode and the current electrode, and the distance of each movement is about 5% of dl. If the three test values ​​are close, take the average value as the auxiliary anode grounding resistance value; if the test values ​​are not close, move the potential electrode toward the current electrode until the test values ​​are close. 2 The auxiliary anode grounding resistance can also be tested using the triangle pole arrangement method shown in Figure 8.1.1 (b). At this time, d1s=d12≥218.1.2 After arranging the electrodes according to Figure 8.1.1, turn the handle of the grounding resistance measuring instrument to make the hand-cranked generator reach the rated speed, and adjust the balance knob until the meter pointer stops on the black line. At this time, the dial value indicated by the black line multiplied by the magnification is the grounding resistance value. 8.2 Sacrificial anode grounding resistance test
8.2.1 Before measuring the sacrificial anode grounding resistance, the sacrificial anode must be disconnected from the pipeline, and then the electrodes are arranged along a straight line perpendicular to the pipeline according to the wiring diagram shown in Figure 8.2.1, d13 is about 40m, d12 is about 20m, and the grounding resistance value is measured according to the operating steps of 8.1.2.
8.2.2 When there are many sacrificial anodes or they are strip sacrificial anodes, and the diagonal length of the sacrificial anode group (or the length of the strip sacrificial anode) is greater than 8m, the grounding resistance is tested according to 8.1, but d13 shall not be less than 40m and d12 shall not be less than 20m. 847
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9 Soil resistivity test
/Potential electrode
Potential electrode
Current electrode
Current electrode
Auxiliary anode grounding resistance test wiring diagramzc-8
Potential electrode
Current electrode
Sacrificial anode grounding resistance test wiring diagram Figure 8.2.1
9.1 Equidistant method
9.1.1 The average soil resistivity from the surface to a depth of α is tested according to the four-pole method shown in Figure 9.1.1. In the figure, four electrodes are arranged on a straight line, and the spacing α and b represent the test depth, and ab, the depth of the electrode into the soil should be less than a/20, and the commonly used ground resistance meter is ZC-8. 848
Figure 9, 1.1 Schematic diagram of soil resistivity test wiring 9.1.2 After measuring the resistance R value according to the operating steps of 8.1.2, the soil resistivity is calculated as follows. 2 yuan aR
Where: o-
-the average soil resistivity from the surface to the depth a soil layer of the measuring point (α·m); -the distance between two adjacent electrodes (m);
R——the indication of the ground resistance meter (Q).
9.2 Unequal distance method
SY/T 0023—1997
(9.1.2）
9.2.1 The unequal distance method is mainly used for soil resistivity testing when the depth is not less than 20m. The test wiring diagram is shown in Figure 9.1.1. At this time, b>a. When the depth is 0-20m, α=1.6m, 6=20m; when the depth is 0-55m, a=5m, b=60m. At this time, the depth h is calculated as follows.
(9.2.1）
9.2.2 After arranging the electrodes according to 9.2.1, operate the ground resistance measuring instrument according to 8.1.2 to measure the R value, and the average soil resistivity at the depth h is calculated as follows.
10 Test of the resistance of the outer anti-corrosion layer of the pipeline
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10.0.1 For a section of pipeline without branches and grounding devices (preferably 500-10000m in length, generally 5000m), the resistance of the anti-corrosion layer shall be tested using the method of this standard. The test wiring diagram is shown in Figure 10.0.1. D
10~30m
500 ~ 10 000 m
Pipeline anti-corrosion layer resistance test wiring diagram Figure 10.0.1
10.0.2 The test steps are as follows;
The distance between the tested section ac and the energization point must be no less than element D. 1
Obtain the length of the tested pipe section (accurate to m). 2
If the ad section is buried with a sacrificial anode, disconnect it from the pipeline. 3
SY/T 0023--1997
4 Before the forced current cathodic protection station is powered on, test the natural potential values ​​of points a and c. After the cathodic protection station is powered on for 24 hours, test the protection potential values ​​of points a and c, and calculate the negative offset potential values ​​of points a and c. 5 According to 6.1, test the current values ​​in the pipes of sections ab and cd at the same time. 10.0.3 The resistance of the pipeline anti-corrosion layer is calculated according to the following formula. (AV.+AV.)La yuan D
20-12)||tt| |Where: PA—
resistance of the anti-corrosion layer of the pipe section (2·m2);
negative offset potential of point a at the beginning of the pipe section (V);AV.
AV.—--negative offset potential of point c at the end of the pipe section (V);l,---absolute value of the current in the pipe section ab (A);I2:—absolute value of the current in the pipe section cd (A);-pipeline length of the measured pipe section ac (m);
Ia——
D—outer diameter of the pipe (m).
10.0.4 For pipes with good insulation flanges (joints) at both ends and no other shunt branches, and with good anti-corrosion layer quality, when its length does not exceed the protection radius of a cathodic protection station, the anti-corrosion layer resistance from the energization point of the cathodic protection station to the end pipeline can be calculated as follows.
Where: AV.
(AV. + AV)LrD
negative offset potential value of pipeline at power supply point (V); —negative offset potential value of pipeline at end (V);
-—cathodic protection current provided to pipeline under test (A); I.
length of pipeline under test (m).
(10.0.4)
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