CN103344548A - System for testing stray current corrosion of buried steel pipeline under function of tensile stress - Google Patents

Abstract

The utility model relates to a stray current corrosion test system for buried steel pipelines under the action of tensile stress, which belongs to the field of material corrosion and protection. The test system includes a stress loading test system, a soil environment simulation system, a stray current simulation system, a cathodic protection system, and an electrochemical test system. The stress loading test system generates the pressure required for the sample test, the soil environment simulation system simulates the soil environment where the buried metal is located, and configures soil solutions with different pH and conductivity, and the stray current simulation system generates DC, AC, AC and DC mixed current stray Current, the cathodic protection system provides cathodic protection potential for the sample, and the electrochemical test system tests the corrosion potential of the sample under different influencing factors. The system can measure weightlessness; can obtain corrosion morphology; can generate DC, AC, AC and DC mixed flow stray current; can provide stress required for experiments according to actual operating conditions; can simulate cathodic protection; Corrosion law experiment.

Description

A Stray Current Corrosion Test System for Buried Steel Pipeline Under Tensile Stress

technical field

The invention belongs to the field of material corrosion and protection, and in particular relates to a stray current corrosion test system for buried steel pipelines under the action of tensile stress.

Background technique

As my country's buried pipeline network becomes more and more complex, steel pipelines in the pipeline network will cause more and more corrosion problems under the action of factors such as stray current and stress, and the damage will become more and more serious. Therefore, research on buried steel pipelines The law of stray current corrosion is very urgent under stress conditions. Since the stray current is affected by many factors such as soil conductivity and buried depth, and it is difficult to conduct field experiments in the special environment, it is very necessary to establish a stray current corrosion test system for buried steel pipelines under stress conditions. At present, there is a single tensile stress test device in China, which can perform tensile tests on optical fibers, plastics, metals and other materials. The existing tensile stress corrosion test devices can perform corrosion tests on rods or plate metals in atmospheric environments. It can also be used for stress corrosion test of other harmful substances. However, the existing experimental devices also have some disadvantages, such as small tensile stress, narrow application range, low test accuracy, inability to conduct stray current corrosion experiments, difficulty in measuring weight loss, and difficulty in obtaining corrosion morphology. There is no stray current corrosion test system for buried steel pipelines under stress conditions in China, so the research and development of stray current corrosion test systems for buried steel pipelines under tensile stress has become an important task for exploring the impact of stray current corrosion on buried steel pipelines. The basis of factors and influencing laws.

Contents of the invention

In order to overcome the defects of the existing tensile stress test device and tensile stress corrosion test device, such as small tensile stress, low test accuracy, and inability to carry out stray current corrosion experiments, the present invention utilizes screw transmission to generate tensile stress, digital multimeter 19 The value obtained by the high-precision tension sensor 9 is displayed in real time, and the DC power supply 22, the pulse signal generator 21, and the intelligent interrupter 20 are used to generate DC, AC, and AC-DC mixed current stray currents; the constant voltage source 12 is used to generate cathodic protection potential; Workstation 15 conducts electrochemical tests on stressed samples; uses pH meter 14 and conductivity meter 13 to configure soil solutions with different pH and conductivity, and monitors changes in soil solution parameters during the experiment. The system can measure weightlessness; can obtain corrosion morphology; can generate DC, AC, AC and DC mixed flow stray current; can provide stress required for experiments according to actual operating conditions; can simulate cathodic protection; Corrosion rule experiments under different stress levels, stray current types/strengths, soil resistivity/conductivity, soil pH, etc.).

A stray current corrosion test system for buried steel pipelines under tensile stress, the system includes a stress loading test system, a soil environment simulation system, a stray current simulation system, a cathodic protection system, and an electrochemical test system. The stress loading test system generates the pressure required for the sample test, the soil environment simulation system simulates the soil environment where the buried metal is located, and configures soil solutions with different pH and conductivity, and the stray current simulation system generates DC, AC, AC and DC mixed current stray Current, the cathodic protection system provides cathodic protection potential for the sample, and the electrochemical test system tests the corrosion potential of the sample under different influencing factors.

The stress loading test system consists of a left tie rod 1, a left bottom plate 2, a long hexagonal head bolt 3, an electrolytic cell 4, a sample 5, a pin 6, a pin sleeve 7, a middle pull rod 8, an S-type tension sensor 9, and a right pull rod 10 , right bottom plate 11, excitation power supply 17, voltage amplifier 18, digital multimeter 19;

It is characterized in that: two long hexagonal head bolts 3 pass through the right bottom plate 11 and are embedded in the blind holes of the left bottom plate 2, the two long hexagonal head bolts 3 form a bracket with the left bottom plate 2 and the right bottom plate 11, and the left and right bottom plates are in turn left tie rods 1 , sample 5, middle tie rod 8, S-type tension sensor 9, right tie rod 10; one end of the long hexagon head bolt 3 is threaded with the right bottom plate 11, and the other end is clearance fit with the left bottom plate 2 blind holes; the left tie rod 1 and The left bottom plate 2 is screwed, and the sample 5 is connected to the left tie rod 1 and the middle tie rod 8 through two pins 6 respectively. The pin 6 is covered with a pin sleeve 7 and the two are interference fit. And in the through hole of the middle tie rod 8, the pin sleeve 7 and the through hole of the left tie rod 1 and the through hole of the middle tie rod 8 are all interference fits; the S-type tension sensor 9 and the middle tie rod 8 are threaded, and the right tie rod 10 passes through The through hole of the right bottom plate 11 is threadedly connected with the S-type tension sensor 9; the sample 5 passes through the middle of the electrolytic cell 4; Sample 5; the positive and negative poles of the excitation power supply 17 are respectively connected to the positive and negative poles of the S-type tension sensor 9 excitation signal lines, the positive and negative poles of the output signal line of the S-type tension sensor 9 are connected to the positive and negative poles of the input terminal of the voltage amplifier 18, and the S-type tension sensor 9 is shielded The line is grounded, and the output terminal of the voltage amplifier 18 is connected with a digital multimeter 19.

Further, the soil environment simulation system includes a conductivity meter 13, a probe P1, a pH meter 14, and a probe P2; the conductivity meter 13 is connected to the probe P1, and the pH meter 14 is connected to the probe P2, and both the probes P1 and P2 are immersed in the electrolytic in the soil solution of the pond.

Further, the stray current simulation system includes a pulse signal generator 21, a power amplifier 23, a constant current source 22, an intelligent interrupter 20, a third auxiliary electrode CE3, an ammeter A2, an ammeter A3, a switch K2, and a switch K3; the pulse signal generator 21 is connected to the power amplifier 23, the positive pole of the power amplifier 23 is connected in series with the switch K2 and the ammeter A2, and then connected to the positive pole of the input terminal of the intelligent interrupter 20, the negative pole of the power amplifier 23 is connected to the negative pole of the input terminal of the intelligent interrupter 20, and the negative pole of the constant current source 22 is connected in series with the switch K3 Connect the negative pole of the input terminal of the intelligent interrupter 20 to the ammeter A3, the positive pole of the constant current source 22 is connected to the positive pole of the input terminal of the intelligent interrupter 20, the positive pole of the output terminal of the intelligent interrupter 20 is connected to the sample 5, and the negative pole is connected to the third auxiliary electrode CE3.

Further, the cathodic protection system includes a constant voltage source 12, an ammeter A1, a switch K1, and a first auxiliary electrode CE1; the positive pole of the constant voltage source 12 is connected to the first auxiliary electrode CE1, and the negative pole is connected in series with the switch K1 and the ammeter A1 to connect the sample 5.

Further, the electrochemical testing system is composed of a PC 16, an electrochemical workstation 15, a reference electrode RE, and a second auxiliary electrode CE2; the electrochemical workstation 15 is connected to the PC 16, and the three electrodes of the electrochemical workstation 15 are connected to the test electrode respectively. Sample 5, the reference electrode RE and the second auxiliary electrode CE2 are connected to form a three-electrode system, the reference electrode RE is close to the sample 5, and the distance between the reference electrode RE and the sample is within the range of 0.5cm to 2cm.

Configure multiple groups of soil simulation solutions according to the needs of the experiment. The properties of the configured soil solution are similar to the physical and chemical properties of the actual soil. Before the experiment, use the conductivity meter 13 and the pH meter 14 to measure the conductivity and pH value of the soil solution. The conductivity meter 13 and the pH meter 14 test the pH value and conductivity value of the solution, and need to be adjusted in time when the parameters occur.

The pulse signal generator 21 can generate AC signals with different frequencies and amplitudes, the power amplifier 23 can amplify the AC signals to simulate AC stray currents, the constant current source 22 can generate DC with different strengths to simulate DC stray currents, and the intelligent interrupter 20 can Realize the control of continuous (duration), intermittent (frequency of action) and instantaneous interference of stray current. The opening and closing of the switches K2 and K3 can realize the control of three kinds of stray currents: AC, DC, and AC-DC mixed current.

The constant voltage source 12 provides the required cathodic protection potential for the sample 5, and the opening and closing of the switch K1 can control whether the sample 5 has cathodic protection or not.

The electrochemical workstation 15 tests the corrosion potential of sample 5 under different influencing factors (soil resistivity/conductivity, soil pH, different stress levels, stray current type/strength, damaged area/peeled area, etc.).

In some respects, the present invention can replace the currently widely used tensile stress test device and tensile stress corrosion test device, and is a novel stray current corrosion test system for buried steel pipelines under stress conditions. The system can measure weightlessness; can obtain corrosion morphology; can generate DC, AC, AC and DC mixed flow stray current; can provide stress required for experiments according to actual operating conditions; simulate cathodic protection; Stress level, stray current type/strength, soil resistivity/conductivity, soil pH, etc.), are widely used in laboratory research in universities and scientific research institutes, as well as in metallurgy, materials, construction, and machinery. In the preliminary research of the enterprise.

Description of drawings

Fig. 1 is the overall structure diagram of the present invention.

Figure 2 is a front view of the left tie rod.

Figure 3.1 is a cross-sectional view of the right bottom plate front view. Figure 3.2 is a top view of the right bottom plate.

Figure 4 is a front view of the right pull rod.

Figure 5.1 is a front view sectional view of the left bottom plate, and Figure 5.2 is a top view of the left bottom plate.

Figure 6 is a top view of the sample.

In the figure, left tie rod 1, left bottom plate 2, long hex head bolt 3, electrolytic cell 4, sample 5, pin 6, pin sleeve 7, middle tie rod 8, S-type tension sensor 9, right tie rod 10, right bottom plate 11, Constant voltage source 12, conductivity meter 13, pH meter 14, electrochemical workstation 15, PC 16, excitation power supply 17, voltage amplifier 18, digital multimeter 19, intelligent interrupter 20, pulse signal generator 21, constant current source 22 , Power amplifier 23.

Detailed ways

In the specific structure of the stray current corrosion test system for buried steel pipelines under the action of tensile stress of the present invention shown in Figure 1, after the stress loading test system is built, use a wrench to simultaneously rotate two long hexagon head bolts 3 Axial tensile stress is generated by screw transmission, and the tension can be changed by adjusting the amount of rotation. Observe the digital multimeter 19 and stop rotating the long hexagon head bolt 3 when the tension is specified. In the experiment, if it is necessary to adjust the tensile stress of the sample 5, it is only necessary to rotate the long hexagon head bolt 3.

Build a soil environment simulation system, a stray current simulation system, a cathodic protection system, and an electrochemical test system. Use the soil environment simulation system to configure the required soil solution, and pour the soil solution into the electrolytic cell 20 . Turn on PC 16, electrochemical workstation 15, pulse signal generator 21, power amplifier 23, intelligent interrupter 20, constant current source 22, constant voltage source 12, conductivity meter 13, pH meter 14, excitation power supply 17, voltage amplifier 18. Digital multimeter 19 power supply. Carry out the corrosion rule experiment under different influencing factors (soil resistivity/conductivity, soil pH, different stress levels, stray current type/intensity, damaged area/stripped area, etc.) according to the following steps.

1. Close switch K1 to perform cathodic protection on sample 5.

2. Open the switch K2 and close the switch K3 to pass the DC stray current to the sample 5.

3. Set the parameters of the electrochemical workstation 15 software in the PC 16 to measure the potential in the sample 5 and process it to obtain a curve. The conductivity meter 13 and the pH meter 14 monitor the conductivity and pH of the solution in real time.

4. Change the current intensity of the constant current source 22, change the intelligent interrupter 20 to realize the continuous (duration), intermittent (frequency of action) and instantaneous interference of the current, measure the potential of the sample 5 with the electrochemical workstation 15 and process it to get the curve.

5. Close the switch K2 and open the switch K3 to pass AC stray current to the sample 5, measure the potential of the sample 5 with the electrochemical workstation 15 and process it to obtain a curve.

6. Change the frequency and amplitude of the signal from the pulse signal generator 21, change the intelligent interrupter 20 to realize continuous, intermittent and instantaneous current interference, measure the potential of the sample 5 with the electrochemical workstation 15 and process it to obtain a curve.

7. Close the switch K2 and the switch K3 to pass the AC/DC mixed current to the sample 5, measure the potential of the sample 5 with the electrochemical workstation 15 and process it to obtain a curve.

8. Change the stress on sample 5, repeat steps 2-7, repeat steps 2-7 each time the stress is changed, and proceed to step 9 after changing the stress at least twice.

9. Disconnect the power supply of all equipment, take out all electrodes and probes, pour out the solution of electrolytic cell 4, pour in the soil solution with different conductivity and pH value, turn on all power supplies, repeat steps 2-8 and then proceed to the next step 10.

10. Disconnect the power supply of all equipment, take out all electrodes and probes, and pour out the solution of electrolytic cell 4.

11. Take out sample 5, dry it with filter paper and place it on an optical balance to measure the weight after corrosion, calculate the corrosion rate according to the weight before corrosion, test time and corrosion area, put sample 5 under an optical microscope for observation and take pictures with a camera corrosion morphology. According to the change of corrosion potential, corrosion rate and corrosion morphology, the influencing factors and rules of stray current corrosion of buried metal under tensile stress can be obtained.

Claims (5)

1. buried steel pipe stray current corrosion pilot system under the drawing stress effect is characterized in that: comprise stress load test system, soil environment simulation system, stray current simulation system, cathodic protection system, electro-chemical test system;

Described stress load test system is made up of left lever (1), left bottom plate (2), long hexagon head bolt (3), electrolytic cell (4), sample (5), pin (6), pin cover (7), middle pull bar (8), S type pulling force sensor (9), right pull bar (10), right base plate (11), excitation power supply (17), voltage amplifier (18), digital multimeter (19);

It is characterized in that: two long hexagon head bolts (3) pass right base plate (11) and embed in left bottom plate (2) blind hole, two long hexagon head bolts (3) and left bottom plate (2), right base plate (11) form support, are followed successively by left lever (1), sample (5), middle pull bar (8), S type pulling force sensor (9), right pull bar (10) between the base plate of the left and right sides; For being threaded, the other end and left bottom plate (2) blind hole is clearance fit between long hexagon head bolt (3) one ends and right base plate (11); Left lever (1) and left bottom plate (2) are for being threaded, sample (5) is connected by two pins (6) respectively with middle pull bar (8) with left lever (1), pin (6) is outer to be with pin cover (7) and to be interference fit between the two, pin cover (7) is arranged in left lever (1) and pull bar (8) through hole, is interference fit between pin cover (7) and left lever (1) through hole and middle pull bar (8) through hole; For being threaded, right pull bar (10) passes right base plate (11) through hole and S type pulling force sensor (9) for being threaded between S type pulling force sensor (9) and the middle pull bar (8); Sample (5) passes electrolytic cell (4) middle part; Sample (5) and the surface-coated insulating material that left lever (1), middle pull bar (8) contact guarantee that stray current is only by sample (5); Excitation power supply (17) both positive and negative polarity S type pulling force sensor (9) pumping signal line both positive and negative polarity respectively links to each other, S type pulling force sensor (9) output signal line both positive and negative polarity links to each other with voltage amplifier (18) input end both positive and negative polarity, S type pulling force sensor (9) shielding line ground connection, voltage amplifier (18) output terminal links to each other with digital multimeter (19).

2. buried steel pipe stray current corrosion pilot system under a kind of drawing stress effect according to claim 1, it is characterized in that: the soil environment simulation system comprises conductivity meter (13), probe P1, pH meter (14), probe P2; Conductivity meter (13) linking probe P1, pH meter (14) linking probe P2, probe P1, P2 all are immersed in the soil liquid of electrolytic cell.

3. buried steel pipe stray current corrosion pilot system under a kind of drawing stress effect according to claim 1, it is characterized in that: the stray current simulation system comprises pulse signal generator (21), power amplifier (23), constant current source (22), intelligent interrupter (20), the 3rd auxiliary electrode CE3, reometer A2, reometer A3, K switch 2, K switch 3; Pulse signal generator (21) links to each other with power amplifier (23), be connected intelligent interrupter (20) input anode behind the anodal serial connection of power amplifier (23) K switch 2 and the reometer A2, power amplifier (23) negative pole connects intelligent interrupter (20) input cathode, be connected intelligent interrupter (20) input cathode behind constant current source (22) negative pole serial connection K switch 3 and the reometer A3, anodal intelligent interrupter (20) input anode that connects of constant current source (22), intelligence interrupter (20) output head anode connects sample (5), and negative pole connects the 3rd auxiliary electrode CE3.

4. buried steel pipe stray current corrosion pilot system under a kind of drawing stress effect according to claim 1, it is characterized in that: described cathodic protection system comprises constant pressure source (12), reometer A1, K switch 1, the first auxiliary electrode CE1; Be connected sample (5) behind the anodal first auxiliary electrode CE1 that connects of constant pressure source (12), negative pole serial connection K switch 1 and reometer A1.

5. buried steel pipe stray current corrosion pilot system under a kind of drawing stress effect according to claim 1 is characterized in that: described electro-chemical test system is made up of PC (16), electrochemical workstation (15), contrast electrode RE, the second auxiliary electrode CE2; Electrochemical workstation (15) links to each other with PC (16), electrochemical workstation (15) three electrodes are connected to form three-electrode system with sample (5), contrast electrode RE, the second auxiliary electrode CE2 respectively, and distance is in 0.5cm to 2cm scope between contrast electrode RE and sample (5).

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