A buried crude oil pipeline internal and external corrosion testing device and method

Abstract

The present invention discloses a device and method for testing the internal and external corrosion of a buried crude oil pipeline, and belongs to the technical field of testing the corrosion rate of buried metal pipelines. The device includes an experimental box, an internal corrosion circulation flow pipeline system, an external corrosion liquid circulation flow pipeline system, an internal and external corrosion measurement unit, and a soil physical property monitoring and adjustment unit. The present invention uses the principles of material conservation and charge conservation to construct a relationship between the length and diameter of the experimental pipe section, the corrosion rate, the relative atomic mass of iron and corrosive ions, the flow rate of the outflow liquid of the solenoid valve, the opening time of the solenoid valve, and the concentration of corrosive ions, and proposes a corrosive ion consumption algorithm. A programmable time controller is used to control the solenoid valve to add a corrosive medium solution to maximize the consistency of the corrosive ion concentration in the experimental environment with the real environment. The present invention can overcome the problems that the existing device cannot simultaneously perform internal and external corrosion tests on buried pipelines and the test accuracy is low, and provides a more reliable basis for the safe operation of buried crude oil pipelines.

Description

Technical Field

[0001] The invention relates to a device and method for testing the internal and external corrosion of a buried crude oil pipeline, belonging to the technical field of buried metal pipeline corrosion rate testing. Background Art

[0002] The mileage of crude oil pipelines in service in my country is increasing year by year. Most of the pipelines are buried underground. Internal and external corrosion of buried pipelines often occurs, and the economic losses caused by corrosion amount to tens of billions of yuan each year. Internal and external corrosion of buried pipelines is caused by chemical or electrochemical reactions between corrosive ions contained in the transported crude oil and buried soil and pipeline steel, generating solid metal compounds, causing steel thinning and quality reduction, and eventually evolving into pipeline failure, resulting in huge economic losses.

[0003] The test experiment is used to measure the internal and external corrosion rate of buried crude oil pipelines under different working conditions. This type of experiment has important academic and engineering value. The current existing equipment for testing the internal and external corrosion of buried crude oil pipelines has the following shortcomings:

[0004] (1) During the corrosion process of crude oil pipelines, the inner surface is usually in contact with the flowing crude oil medium, and the outer surface is in full contact with the soil. During the corrosion process of the pipeline, the ion consumption and migration on the inner and outer surfaces are in dynamic equilibrium, and the ion concentration at the corrosion defect remains almost constant. However, the traditional test experimental device does not take into account the concentration changes caused by the consumption of corrosive ions, resulting in a large deviation in the corrosion rate measurement.

[0005] (2) In addition, the existing test devices such as the multiphase flow corrosion and flow state test experimental pipeline device and test experimental method disclosed in CN103926191A can only perform internal corrosion tests on pipelines and do not consider the impact of temperature changes during the flow process on the corrosion rate; the test device CN107238566A discloses an experimental device for testing external corrosion of pipelines. This device can only perform external corrosion tests on pipelines and does not consider the impact of changes in ion concentration in the external soil on the corrosion rate. The existing test devices cannot perform internal and external corrosion tests on buried crude oil pipelines at the same time. Summary of the invention

[0006] In view of the problems in the prior art, the present invention provides a device and method for testing the internal and external corrosion of a buried crude oil pipeline. A corrosion pre-experiment is carried out, and based on the pre-experiment corrosion data, a corrosion growth model based on a gamma degradation process is used to predict the corrosion growth rate. The material conservation and charge conservation principles of the corrosion process are used to construct a relationship between eight experimental parameter variables, namely, the length of the experimental pipe section, the pipe diameter, the corrosion rate, the relative atomic mass of the iron element, the relative atomic mass of the corrosive ions, the outflow flow rate of the solenoid valve, the opening time of the solenoid valve, and the concentration of corrosive ions. A corrosive ion consumption algorithm suitable for different working conditions is proposed, and a programmable time controller is used to control the solenoid valve to add a corrosive medium solution, so as to maximize the consistency between the corrosive ion concentration in the experimental environment and the real environment. This can not only realize the simultaneous implementation of internal and external corrosion test experiments, but also improve the accuracy of the internal and external corrosion rate test of the buried crude oil pipeline.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A buried crude oil pipeline internal and external corrosion testing device and method, characterized in that the testing device includes an experimental box, an internal corrosion circulating flow pipeline system, an external corrosion liquid circulating flow pipeline system, an internal and external corrosion measurement unit, and a soil physical property monitoring and adjustment unit;

[0009] The internal corrosion circulation flow pipeline system is composed of the experimental box 1, 1# bolt 20, 1# gasket 21, 1# flange 22, pipeline 2, flow meter 19, cleaning recovery pipeline, internal corrosion water bath heating pipeline, internal corrosion medium filling pipeline, circulation pump 16, 2# bolt 26, 2# gasket 27 and 2# flange 43 connected in sequence in the clockwise direction;

[0010] The experimental box 1 is a rectangular box with an open top, a circular hole on each of the two sides, two circular holes on the front, and four circular holes on the top; the experimental box 1 can be filled with experimental soil and covers the external corrosion liquid filling and circulating temperature control pipeline 3, the experimental pipe section 23, the 1# annular filler 24, the 2# annular filler 25, the temperature measurement probe 28, the soil pH value measurement probe 29, the internal corrosion probe 30, the 1# electromagnetic valve 32, the 1# three-electrode system 33, the 2# electromagnetic valve 34, the 2# three-electrode system 35 and the soil pH adjustment and filling device 41; the experimental box 1 and the experimental pipe section 23 are connected to the pipeline 2 through the 1# bolt 20, the 1# gasket 21, the 1# flange 22, the 2# bolt 26, the 2# gasket 27, and the 2# flange 43;

[0011] The cleaning recovery pipeline is led out from the dirty oil tank 17, and is connected to the pipeline 2 downstream of the flow meter 19 after passing through the drain valve 18; the internal corrosion water bath heating pipeline is led out from the pipeline 2 downstream of the drain valve 18, and is connected to the pipeline 2 downstream of the 5# throttle valve 46 after passing through the 5# throttle valve 46, the 2# heater 47 and the 6# throttle valve 48; the internal corrosion medium filling pipeline is led out from the pipeline 2 between the 6# throttle valve 48 and the check valve 15, and is connected to the pipeline 2 between the check valve 15 and the circulation pump 16 after passing through the 2# throttle valve 9, the oil storage tank 8, the ball valve 10, the buffer tank 11, and the 3# solenoid valve 14; the agitator 12 and the internal corrosion liquid sprayer 13 are fixedly installed on the top of the buffer tank 11; the top of the 3# solenoid valve 14 is connected in sequence to the 2# programmable time controller 50 and the 2# power supply 49 to form a control loop; the circulation pump 16 is installed on the pipeline 2 between the check valve 15 and the experimental box 1;

[0012] The external corrosion liquid circulation flow pipeline system is composed of an external corrosion liquid filling and circulation temperature control pipeline 3, an external corrosion water bath heating pipeline, a material pump 4, an external corrosion liquid injection pipeline, and an external corrosion liquid filling control unit connected in sequence in a clockwise direction;

[0013] The external corrosion water bath heating pipeline, material pump 4, and external corrosion liquid injection pipeline are located outside the experimental box 1; the external corrosion liquid filling and circulating temperature control pipeline 3 is an annular pipeline that penetrates from the front opening of the experimental box 1 and then penetrates from the front opening of the experimental box 1; the external corrosion water bath heating pipeline is led out from the external corrosion liquid filling and circulating temperature control pipeline 3, and is connected to the external corrosion liquid filling and circulating temperature control pipeline 3 after passing through the 3# throttle valve 44, the 1# heater 5, and the 4# throttle valve 45; the material pump 4 is installed on the external corrosion liquid filling and circulating temperature control pipeline 3 downstream of the 4# throttle valve 45; the external corrosion liquid injection pipeline is led out from the liquid storage tank 6, and is connected to the external corrosion liquid filling and circulating temperature control pipeline 3 downstream of the material pump 4 through the 1# throttle valve 7;

[0014] The external corrosion liquid filling control unit is led out from the electrochemical workstation 40, and after passing through the computer 37, the 1# programmable time controller 36, and the electromagnetic relay 38, it is connected to the experimental box 1 through the top opening of the experimental box 1 and is connected to the tops of the 1# electromagnetic valve 32 and the 2# electromagnetic valve 34; one end of the 1# electromagnetic valve 32 and the 2# electromagnetic valve 34 is connected to the external corrosion liquid filling and circulating temperature control pipeline 3, and the other end is connected to the 1# annular filler 24 and the 2# annular filler 25 respectively; the 1# annular filler 2 The 4# and 2# annular injectors 25 are annular pipeline structures with an opening at the top, and the annular pipeline is provided with 8 corrosion liquid injection nozzles 42 which are unevenly distributed along the vertical ground direction, and the nozzle arrangement scheme is to arrange 8 nozzles at the positions of 0°, 36°, 72°, 108°, 144°, 180°, 225°, and 315° of the annular injectors in a clockwise direction; the 1# annular injectors 24 and 2# annular injectors 25 are vertically installed in the experimental box 1, and are placed around the experimental pipe section 23;

[0015] The internal and external corrosion measurement unit includes an internal corrosion measurement unit and an external corrosion measurement unit; the external corrosion measurement unit is led out by the electrochemical workstation 40, connected to the experimental box 1 from the top opening of the experimental box 1 and connected to the 1# three-electrode system 33 and the 2# three-electrode system 35 at the same time; the top of the electrochemical workstation 40 is connected to the 1# power supply 39; the internal corrosion measurement unit is led out by the display 31, connected to the experimental box 1 from the top opening of the experimental box 1 and connected to the temperature measurement probe 30; the soil physical property monitoring and adjustment unit is led out by the display 31, connected to the experimental box 1 from the top opening of the experimental box 1 and connected to the temperature measurement probe 28 and the soil pH value measurement probe 29; the internal corrosion probe 30 is drilled and installed in the experimental pipe section 23; the 1# three-electrode system 33, the 2# three-electrode system 35, the temperature measurement probe 28, and the soil pH value measurement probe 29 are fixedly installed on the outer surface of the experimental pipe section 23; the soil pH adjustment and filling device 41 is fixedly installed on the top of the experimental box 1.

[0016] A method for testing internal and external corrosion of a buried crude oil pipeline is implemented by using the above-mentioned device for testing internal and external corrosion of a buried crude oil pipeline, and is characterized by comprising the following steps:

[0017] S1, select the type of corrosive ions according to the experimental requirements, and prepare a certain amount of external corrosive medium solution and internal corrosive medium solution containing a certain concentration of the selected corrosive ions, prepare a certain amount of soil pH adjustment solution and a certain concentration according to the experimental requirements, and then add the external corrosive medium solution, the internal corrosive medium solution, and the soil pH adjustment solution to the liquid storage tank 6, the internal corrosive liquid sprayer 13, and the soil pH adjustment filling device 41 respectively;

[0018] S2, determine the metal material and length, diameter, and wall thickness parameters of the pipeline according to the experimental requirements, make the experimental box 1 and the experimental pipe section 23, and install the experimental pipe section 23 equipped with the internal corrosion probe 30, the 1# annular injector 24, and the 2# annular injector 25 into the experimental box 1, connect the experimental box 1 to the pipeline 2 through the flange 20, and then install the 1# three-electrode system 33, the 2# three-electrode system 35, the temperature measurement probe 28, and the soil pH value measurement probe 29 to a fixed position;

[0019] S3, open the ball valve 10, inject the crude oil in the oil storage tank 8 into the buffer tank 11, then turn on the agitator 12 and the internal corrosion liquid sprayer 13, and prepare the test crude oil containing a certain concentration of internal corrosion ions in the buffer tank 11;

[0020] S4, open the 1# throttle valve 7, inject the external corrosion medium solution prepared in the liquid storage tank 6 into the external corrosion liquid filling and circulating temperature control pipeline 3, and according to the soil conditions at the buried site of the crude oil pipeline, dig the soil on site and fill it into the experimental box 1, then seal the experimental box 1, close the 1# throttle valve 7, open the 3# throttle valve 44, the 4# throttle valve 45, the 1# heater 5 and the material pump 4, increase the operating power of the 1# heater 5, and quickly preheat the added soil temperature to the required temperature of the experiment;

[0021] S5, close the drain valve 18, open the 3# solenoid valve 14, the check valve 15, the 5# throttle valve 46, the 6# throttle valve 48, the circulation pump 16 and the 2# heater 47 in sequence, and adjust the speed of the circulation pump 16 and the power of the 2# heater 47 so that the experimental crude oil in the pipeline 2 reaches the flow rate and temperature required for the experiment;

[0022] S6, turn on the display 31, computer 37, electromagnetic relay 38, 1# power supply 39, electrochemical workstation 40, 2# power supply 49, turn off 1# programmable time controller 36 and 2# programmable time controller 50, measure the soil pH value at this time, and carry out the internal and external corrosion pre-experiment for 48 hours; starting from time 0, measure and record the maximum corrosion depth d (in mm) of the corrosion point of the experimental pipe section every 6 hours, which is recorded as d n0 d n1 d n2 d n3 d n4 d n5 d n6 d n7 d n8 d w0 d w1 d w2 d w3 d w4 d w5 d w6 d w7 dw8 , where the subscript n represents internal corrosion and the subscript w represents external corrosion;

[0023] S7, according to the experimental requirements, the experimental period is set to T days, T>2, and the crude oil flow rate after the 3# solenoid valve 14 is opened is set to S by using the 2# programmable time controller 50. 油 , use 1# programmable time controller 36 to set the flow rate of ionized water flowing out after 1# solenoid valve 32 and 2# solenoid valve 34 are opened to S 水 , use 2# programmable time controller 50 to set 3# solenoid valve 14 to open for t every 24 hours 1 , use 1# programmable time controller 36 to set the opening time of 1# solenoid valve 32 and 2# solenoid valve 34 to t 2 / 2;

[0024] S8, conduct formal experiments on internal corrosion and external corrosion, adjust the speed of the circulation pump 16, the power of the 1# heater 5, the power of the 2# heater 47, and the soil pH adjustment and filling device 41, obtain and record the internal and external corrosion rates of the experimental pipe section 23 under different working conditions;

[0025] S9, after the experiment is over, open the drain valve 18, turn off the 1# heater 5, 5# throttle valve 46, 2# heater 47, 6# throttle valve 48, circulation pump 16, material pump 4, 1# power supply 39 and 2# power supply 50 in sequence, take out the experimental soil and experimental pipe section 23, organize other experimental measurement equipment, and process the experimental data;

[0026] In step S7, the 3# solenoid valve 14 is opened every 24 hours for a time t 1 , 1# solenoid valve 32 and 2# solenoid valve 34 are open for 24 hours 2 The calculation method of / 2 includes the following steps:

[0027] Step 1: Calculate the internal corrosion growth and external corrosion growth every 6 hours during the 48 hours of the pre-experiment and record them as Δd ni and Δd wi , △d ni =d ni -d n(i-1) ,△d wi =d wi -d w(i-1) , i = 1, 2, 3, ..., 8; calculate the corrosion growth Δd in every 6-hour interval within 48 hours of the pre-experimental period according to the following formula ni , External corrosion growth Δd wi The mean μ and standard deviation σ of

[0028]

[0029]

[0030] Step 2: Use the probability density function of the gamma distribution of the gamma degradation model to calculate the corrosion growth Δd in the pipeline every 6 hours after 48 hours of the pre-experiment. nj and external corrosion growth Δd wj , j = 9, 10, 11, ..., k, k = 4 (T-2) The corrosion growth of the pipeline inside and outside every 6 hours after 48 hours of the pre-experiment Δd j Obey the probability density function:

[0031]

[0032] Where: A—function shape parameter;

[0033] β—function scale parameter, β>0;

[0034] Γ(A)—Gamma function with A as variable;

[0035] In step 2, the values ​​of A and β are calculated using moment parameter estimation, and the calculation formulas are as follows:

[0036] A=β 2 σ 2 ;

[0037] β = A / μ;

[0038] Step 3: Based on the corrosion growth Δd of the pipeline inside and outside every 6 hours within 48 hours of the preliminary experiment, ni With Δd wi , the corrosion growth of the pipeline inside and outside every 6 hours after 48 hours of the pre-experiment Δd nj With Δd wj The total depth of internal corrosion y in the experimental period is calculated in turn. n , total depth of external corrosion y w , average internal corrosion rate v n , average external corrosion rate v w , the calculation formula is:

[0039]

[0040]

[0041] Where: ρ—pipeline steel density, kg / m 3 ;

[0042] y—total corrosion depth during the experimental period, mm;

[0043] v—average corrosion rate during the experimental period, g / (m 2 s);

[0044] Step 4: Use the following formula to calculate the average internal corrosion rate v n and S 油 Calculate the opening time of 3# solenoid valve 14 every 24 hours as t 1 , according to the average external corrosion rate vw and S 水 Calculate the total opening time t of 1# solenoid valve 32 and 2# solenoid valve 34 every 24 hours 2 :

[0045]

[0046] Where, L is the length of the experimental pipe section, m;

[0047] D—outer diameter of the experimental pipe section, m;

[0048] v—average corrosion rate during the experimental period, g / (m 2 s);

[0049] m Fe —Relative atomic mass of iron;

[0050] m—relative atomic mass of corrosive ions;

[0051] T—experimental period, days;

[0052] S—Flow rate of ionized water or crude oil flowing out after opening the solenoid valve, m 3 / s;

[0053] t—solenoid valve opening time, s;

[0054] c—Corrosive ion concentration, g / m 3 .

[0055] The advantages of the present invention are:

[0056] (1) The internal corrosive medium filling pipeline and the external corrosive liquid filling control unit designed by the present invention can ensure that the corrosive ions are consumed and replenished in time during the corrosion test of the internal and external corrosion test of the buried crude oil pipeline, so that the concentration of corrosive ions is maintained constant, thereby ensuring the accuracy of the experiment;

[0057] (2) The present invention adopts a corrosion growth model based on the gamma degradation process to predict the corrosion rate and applies the material conservation and charge conservation principles in the pipeline corrosion process to construct a relationship between eight experimental parameter variables, namely, the length of the experimental pipe section, the pipe diameter, the corrosion rate, the relative atomic mass of the iron element, the relative atomic mass of the corrosive ion, the flow rate of the outflow liquid of the solenoid valve, the opening time of the solenoid valve, and the concentration of the corrosive ion. A corrosive ion consumption supplement algorithm is disclosed, which can realize corrosion test experiments with constant corrosive ion concentration under different corrosive anions, different pH values, and different temperature conditions;

[0058] (3) The annular injector designed by the present invention takes into account the influence of gravity on the concentration distribution of corrosive anions and adopts an unevenly distributed corrosive liquid injection nozzle along the gravity direction to ensure that the corrosive anions are evenly distributed in the direction vertical to the ground, thereby improving the accuracy of the experiment;

[0059] (4) The internal corrosion circulating flow pipeline system and the external corrosion liquid circulating flow pipeline system designed by the present invention can simultaneously carry out internal corrosion and external corrosion experiments on pipelines, and have the advantages of high degree of automation, easy disassembly and installation, and high measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0061] Figure 1 The present invention is a schematic diagram of the structural composition of a buried crude oil pipeline internal and external corrosion testing device.

[0062] Figure 2 This is a schematic diagram of the internal perspective and external structure of the experimental box.

[0063] Figure 3 Schematic diagram of the ring filler.

[0064] In the figure: experimental box 1, pipeline 2, external corrosion liquid filling and circulation temperature control pipeline 3, material pump 4, 1# heater 5, liquid storage tank 6, 1# throttle valve 7, oil storage tank 8, 2# throttle valve 9, ball valve 10, buffer tank 11, agitator 12, internal corrosion liquid sprayer 13, 3# solenoid valve 14, check valve 15, circulation pump 16, dirty oil tank 17, drain valve 18, flow meter 19, 1# bolt 20, 1# gasket 21, 1# flange 22, experimental pipe section 23, 1# annular filler 24, 2# annular filler 25, 2# bolt 26, 2# gasket 27, temperature measurement probe 28. Soil pH value measuring probe 29. Internal corrosion probe 30. Display 31. 1# electromagnetic valve 32. 1# three-electrode system 33. 2# electromagnetic valve 34. 2# three-electrode system 35. 1# programmable time controller 36. Computer 37. Electromagnetic relay 38. 1# power supply 39. Electrochemical workstation 40. Soil pH adjustment and filling device 41. Corrosive liquid filling nozzle 42. 2# flange 43. 3# throttle valve 44. 4# throttle valve 45. 5# throttle valve 46. 2# heater 47. 6# throttle valve 48. 2# power supply 49. 2# programmable time controller 50. DETAILED DESCRIPTION

[0065] In order to clearly and completely describe the technical features, purposes and effects of the present invention, the specific implementation of the present invention is now described with reference to the accompanying drawings. The accompanying drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0066] In the description of the present invention, it should be noted that the term "said" is used to indicate the presence of one or more elements / components / etc.; the term "downstream" is used to indicate the position of the fluid after it flows through the pipeline or equipment outlet along the flow direction; the terms "middle", "top", "side", "front", "vertical", "inside", "outside", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and briefly describing, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0067] As attached Figure 1-3The present invention provides an internal and external corrosion testing device for a buried crude oil pipeline. The device consists of an experimental box, an internal corrosion circulating flow pipeline system, an external corrosion liquid circulating flow pipeline system, an internal and external corrosion measuring unit, and a soil physical property monitoring and regulating unit.

[0068] The internal corrosion circulation flow pipeline system is composed of the experimental box 1, 1# bolt 20, 1# gasket 21, 1# flange 22, pipeline 2, flow meter 19, cleaning recovery pipeline, internal corrosion water bath heating pipeline, internal corrosion medium filling pipeline, circulation pump 16, 2# bolt 26, 2# gasket 27 and 2# flange 43 connected in sequence in the clockwise direction;

[0069] The experimental box 1 is a rectangular box with an open top, a circular hole on each of the two sides, two circular holes on the front, and four circular holes on the top. The top opening allows soil to be filled into the box, the two side openings allow the box to be connected to the pipeline 2 through a flange, the front opening allows external corrosion liquid filling and the circulating temperature control pipeline 3 to pass in and out of the box, and the top opening allows the wires to be connected into the box; the experimental box 1 can be filled with experimental soil and cover the external corrosion liquid filling and circulating temperature control pipeline 3, the experimental pipe section 23, the 1# annular filler 24, the 2# annular filler 25, The temperature measuring probe 28, the soil pH measuring probe 29, the internal corrosion probe 30, the 1# electromagnetic valve 32, the 1# three-electrode system 33, the 2# electromagnetic valve 34, the 2# three-electrode system 35 and the soil pH adjustment and filling device 41; the experimental box 1 and the experimental pipe section 23 are connected to the pipeline 2 through the 1# bolt 20, the 1# gasket 21, the 1# flange 22, the 2# bolt 26, the 2# gasket 27, and the 2# flange 43; the cleaning recovery pipeline is led out from the dirty oil tank 17, and is connected to the pipeline 2 downstream of the flow meter 19 after passing through the drain valve 18. The cleaning recovery pipeline is realized by opening or closing the drain valve 18. The connection and cutoff of the dirty oil tank 17 with the pipeline 2 are now realized; the internal corrosion water bath heating pipeline is led out from the downstream pipeline 2 of the sewage valve 18, and is connected to the downstream pipeline 2 of the 5# throttle valve 46 after passing through the 5# throttle valve 46, the 2# heater 47 and the 6# throttle valve 48. The crude oil in the pipeline 2 passes through the 5# throttle valve 46 and enters the 2# heater for heating, and then flows through the 6# throttle valve 48 into the pipeline 2 to realize the water bath heating of the crude oil; the internal corrosion medium filling pipeline is led out from the pipeline 2 between the 6# throttle valve 48 and the check valve 15, and passes through the 2# throttle valve 9, the oil storage tank 8, the ball valve 10, the buffer tank 11, the 3# solenoid valve 14 After that, it is connected to the pipeline 2 between the check valve 15 and the circulation pump 16; the agitator 12 and the internal corrosion liquid sprayer 13 are fixedly installed on the top of the buffer tank 11, and the agitator 12 can magnetically stir the crude oil in the buffer tank 11; the top of the 3# solenoid valve 14 is connected to the 2# programmable time controller 50 and the 2# power supply 49 in sequence to form a control loop, and the control algorithm of the 2# programmable time controller 50 can be set to control the flow rate of the crude oil flowing out of the 3# solenoid valve, so as to realize the injection of internal corrosive ions into the pipeline 2; the circulation pump 16 is installed on the pipeline 2 between the check valve 15 and the experimental box 1;

[0070] The external corrosion liquid circulation flow pipeline system is composed of an external corrosion liquid filling and circulation temperature control pipeline 3, an external corrosion water bath heating pipeline, a material pump 4, an external corrosion liquid injection pipeline, and an external corrosion liquid filling control unit connected in sequence in a clockwise direction;

[0071] The external corrosion water bath heating pipeline, material pump 4, and external corrosion liquid injection pipeline are located outside the experimental box 1; the external corrosion liquid filling and circulating temperature control pipeline 3 is an annular pipeline that penetrates from the front opening of the experimental box 1 and then penetrates from the front opening of the experimental box 1; the external corrosion water bath heating pipeline is led out from the external corrosion liquid filling and circulating temperature control pipeline 3, and is connected to the external corrosion liquid filling and circulating temperature control pipeline 3 after passing through the 3# throttle valve 44, the 1# heater 5, and the 4# throttle valve 45; the material pump 4 is installed on the external corrosion liquid filling and circulating temperature control pipeline 3 downstream of the 4# throttle valve 45; the external corrosion liquid injection pipeline is led out from the liquid storage tank 6, and is connected to the external corrosion liquid filling and circulating temperature control pipeline 3 downstream of the material pump 4 through the 1# throttle valve 7;

[0072] The external corrosion liquid filling control unit is led out from the electrochemical workstation 40, and after passing through the computer 37, the 1# programmable time controller 36, and the electromagnetic relay 38, it is connected to the experimental box 1 through the top opening of the experimental box 1 and is connected to the tops of the 1# electromagnetic valve 32 and the 2# electromagnetic valve 34; one end of the 1# electromagnetic valve 32 and the 2# electromagnetic valve 34 is connected to the external corrosion liquid filling and circulating temperature control pipeline 3, and the other end is connected to the 1# annular filler 24 and the 2# annular filler 25 respectively; the 1# annular filler 24 and the 2# annular filler 25 are connected to the outer corrosion liquid filling and circulating temperature control pipeline 3, and the other end is connected to the 1# annular filler 24 and the 2# annular filler 25 respectively; The filler 25 is an annular pipe structure with an opening at the top, and the annular pipe is provided with 8 corrosion liquid filling nozzles 42 which are unevenly distributed along the vertical ground direction. The nozzle arrangement scheme is to arrange 8 nozzles at the positions of 0°, 36°, 72°, 108°, 144°, 180°, 225° and 315° of the annular filler in a clockwise direction to realize uniform filling of the external corrosion liquid; the 1# annular filler 24 and the 2# annular filler 25 are vertically installed in the experimental box 1 and are placed around the experimental pipe section 23;

[0073] The internal and external corrosion measurement unit comprises an internal corrosion measurement unit and an external corrosion measurement unit; the external corrosion measurement unit is led out from the electrochemical workstation 40, connected to the experimental box 1 through the top opening of the experimental box 1, and connected to the 1# three-electrode system 33 and the 2# three-electrode system 35 at the same time; the pipeline external corrosion depth data is measured by the three-electrode system and then transmitted to the electrochemical workstation, so as to realize the measurement of pipeline external corrosion depth data; the top of the electrochemical workstation 40 is connected to the 1# power supply 39; the internal corrosion measurement unit is led out from the display (31), connected to the experimental box (1) through the top opening of the experimental box The internal corrosion probe (30) is connected to the body (1); the soil physical property monitoring and adjustment unit is led out by the display (31), and is connected to the temperature measurement probe (28) and the soil pH value measurement probe (29) in the experimental box (1) through the opening on the top of the experimental box (1); the internal corrosion probe 30 is drilled and installed in the experimental pipe section 23; the 1# three-electrode system 33, the 2# three-electrode system 35, the temperature measurement probe 28, and the soil pH value measurement probe 29 are fixedly installed on the outer surface of the experimental pipe section 23; the soil pH adjustment and filling device 41 is fixedly installed on the top of the experimental box 1. The embodiment is as follows, using the present invention to test the internal and external corrosion of the buried crude oil pipeline in sulfate corrosive soil under different soil temperature and pH conditions, and the experimental process is as follows:

[0074] S1, determine that the external corrosion ions of the pipeline are carbonate ions, and the internal corrosion ions of the pipeline are chloride ions. Use sodium carbonate and water to prepare 20L of carbonate ion concentration of 127.5g / m 3 Sodium carbonate solution is added to the liquid storage tank 6, and 10L of sodium chloride and water are prepared to have a chloride ion concentration of 20g / m 3 The sodium chloride solution is added to the internal corrosion liquid sprayer 13, and 1L of ammonia solution containing 5% to 8% ammonia is added to the soil pH adjustment and filling device 41;

[0075] S2, determine the size parameters of the experimental box 1 as 1m long, 0.5m wide, and 0.5m high. The material of the experimental pipe section 23 is L245 steel, with a length of 1m, an inner diameter of 20mm, an outer diameter of 25mm, and a wall thickness of 3mm. Install the experimental pipe section 23 equipped with the internal corrosion probe 30, the 1# annular injector 24, and the 2# annular injector 25 into the experimental box 1, connect the experimental box 1 to the pipeline 2 through the flange 20, and then install the 1# three-electrode system 33, the 2# three-electrode system 35, the temperature measurement probe 28, and the soil pH value measurement probe 29 to a fixed position;

[0076] S3, open the ball valve 10, inject the crude oil in the oil storage tank 8 into the buffer tank 11, then open the internal corrosion liquid sprayer 13 and the stirrer 12, mix the prepared sodium chloride solution and the crude oil thoroughly, and prepare a solution with a chloride ion concentration of 20g / m in the buffer tank 11.3 of test crude oil;

[0077] S4, open the 1# throttle valve 7, inject the sodium carbonate solution prepared in the liquid storage tank 6 into the external corrosion liquid filling and circulating temperature control pipeline 3, and fill the experimental box 1 with soil dug on site according to the soil conditions of the pipeline buried site, and then seal the experimental box 1, close the 1# throttle valve 7, turn on the material pump 4 and the 1# heater 5, and preheat the temperature of the experimental box 1 to 20°C;

[0078] S5, close the drain valve 18, open the 3# solenoid valve 14, the check valve 15, the 5# throttle valve 46, the 6# throttle valve 48, the circulation pump 16 and the 2# heater 47 in sequence, and adjust the speed of the circulation pump 16 and the power of the 2# heater 47 so that the experimental crude oil in the pipeline 2 reaches the experimental flow rate of 0.2 m / s and the temperature of 25°C;

[0079] S6, turn on the display 31, computer 37, electromagnetic relay 38, 1# power supply 39, electrochemical workstation 40, 2# power supply 49, turn off 1# programmable time controller 36 and 2# programmable time controller 50, measure the soil pH value at this time to be 5.9, carry out the internal and external corrosion pre-experiment for 48 hours, and measure and record the maximum corrosion depth d (in mm) of the corrosion point of the experimental pipe section every 6 hours from time 0, respectively, and record it as d n0 d n1 d n2 d n3 d n4 d n5 d n6 d n7 d n8 d w0 d w1 d w2 d w3 d w4 d w5 d w6 d w7 d w8 , where the subscript n represents internal corrosion and the subscript w represents external corrosion;

[0080] S7, set the experimental period T as 30 days, use the 2# programmable time controller 50 to set the crude oil flow rate after the 3# solenoid valve 14 is opened to S 油 =3.1×10 -3 m 3 / s, and the ionized water flow rate after the 1# solenoid valve 32 and the 2# solenoid valve 34 are opened is set to S by using the 1# programmable time controller 36. 水 =1.4×10 -3 m 3 / s; the calculated internal corrosion function shape parameter A = 1.27, size parameter β = 0.48, external corrosion function shape parameter A = 1.08, size parameter β = 0.41, internal corrosion rate v = 2.21×10 -5 g / (m 2 ·s), external corrosion rate v = 1.36×10 -5 g / (m 2 ·s), the opening time of 1# solenoid valve 32 and 2# solenoid valve 34 every 24 hours is t 2 / 2 = 17.3 seconds, the opening time of 3# solenoid valve 14 every 24 hours is t 1 = 25.2 seconds, set the control algorithm of 1# programmable time controller 36 and 2# programmable time controller 50;

[0081] S8, turn on the 1# programmable time controller 36 and the 2# programmable time controller 50, and carry out formal experiments on internal corrosion and external corrosion at the same time, adjust the speed of the circulation pump 16, the power of the 1# heater 5, the power of the 2# heater 47, and the soil pH adjustment and filling device 41, and obtain and record the internal and external corrosion rates of the experimental pipe section 23 under different working conditions;

[0082] S9, after the experiment is over, open the drain valve 18, turn off the 1# heater 5, 5# throttle valve 46, 2# heater 47, 6# throttle valve 48, circulation pump 16, material pump 4, 1# power supply 39 and 2# power supply 50 in sequence, take out the experimental soil and experimental pipe section 23, organize other experimental measurement equipment, and process the experimental data.

[0083] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A buried crude oil pipeline internal and external corrosion testing device, characterized in that: The test device includes an experimental box, an internal corrosion circulation flow pipeline system, an external corrosion liquid circulation flow pipeline system, an internal and external corrosion measurement unit, and a soil physical property monitoring and adjustment unit; The internal corrosion circulation flow pipeline system is composed of an experimental box (1), a 1# bolt (20), a 1# gasket (21), a 1# flange (22), a pipeline (2), a flow meter (19), a cleaning recovery pipeline, an internal corrosion water bath heating pipeline, an internal corrosion medium filling pipeline, a circulation pump (16), a 2# bolt (26), a 2# gasket (27) and a 2# flange (43) connected in sequence in a clockwise direction; The experimental box (1) is a rectangular box with an open top, a circular hole on each of the two sides, two circular holes on the front, and four circular holes on the top; the experimental box (1) can be filled with experimental soil and covers an external corrosion liquid filling and circulating temperature control pipeline (3), an experimental pipe section (23), a 1# annular filler (24), a 2# annular filler (25), a temperature measurement probe (28), a soil pH value measurement probe (29), an internal corrosion probe (30), a 1# electromagnetic valve (32), a 1# three-electrode system (33), a 2# electromagnetic valve (34), a 2# three-electrode system (35), and a soil pH adjustment and filling device (41); the experimental box (1) and the experimental pipe section (23) are connected to the pipeline (2) through a 1# bolt (20), a 1# gasket (21), a 1# flange (22), a 2# bolt (26), a 2# gasket (27), and a 2# flange (43); The cleaning recovery pipeline is led out from the dirty oil tank (17), passes through the sewage valve (18), and is connected to the pipeline (2) downstream of the flow meter (19); the internal corrosion water bath heating pipeline is led out from the pipeline (2) downstream of the sewage valve (18), passes through the 5# throttle valve (46), the 2# heater (47) and the 6# throttle valve (48), and is connected to the pipeline (2) downstream of the 5# throttle valve (46); the internal corrosion medium filling pipeline is led out from the pipeline (2) between the 6# throttle valve (48) and the check valve (15), passes through the 2# throttle valve (9), the storage valve (47), and the 6# throttle valve (48). The oil tank (8), ball valve (10), buffer tank (11), and 3# electromagnetic valve (14) are connected to the intermediate pipeline (2) of the check valve (15) and the circulation pump (16); the top of the buffer tank (11) is fixedly installed with an agitator (12) and an internal corrosion liquid sprayer (13); the top of the 3# electromagnetic valve (14) is connected in sequence to the 2# programmable time controller (50) and the 2# power supply (49) to form a control loop; the circulation pump (16) is installed on the pipeline (2) between the check valve (15) and the experimental box (1); The external corrosion liquid circulation flow pipeline system is composed of an external corrosion liquid filling and circulation temperature control pipeline (3), an external corrosion water bath heating pipeline, a material pump (4), an external corrosion liquid injection pipeline, and an external corrosion liquid filling control unit connected in sequence in a clockwise direction; The external corrosion water bath heating pipeline, the material pump (4), and the external corrosion liquid injection pipeline are located outside the experimental box (1); the external corrosion liquid filling and circulating temperature control pipeline (3) is an annular pipeline that penetrates from the front opening of the experimental box (1) and then penetrates from the front opening of the experimental box (1); the external corrosion water bath heating pipeline is led out from the external corrosion liquid filling and circulating temperature control pipeline (3), and is connected to the external corrosion liquid filling and circulating temperature control pipeline (3) after passing through the 3# throttle valve (44), the 1# heater (5), and the 4# throttle valve (45); the material pump (4) is installed on the external corrosion liquid filling and circulating temperature control pipeline (3) downstream of the 4# throttle valve (45); the external corrosion liquid injection pipeline is led out from the liquid storage tank (6), and is connected to the external corrosion liquid filling and circulating temperature control pipeline (3) downstream of the material pump (4) through the 1# throttle valve (7); The external corrosion liquid filling control unit is led out from the electrochemical workstation (40), passes through a computer (37), a 1# programmable time controller (36), and an electromagnetic relay (38), and is connected to the experimental box (1) through an opening at the top of the experimental box (1) and is simultaneously connected to the tops of the 1# electromagnetic valve (32) and the 2# electromagnetic valve (34); one end of the 1# electromagnetic valve (32) and the 2# electromagnetic valve (34) is connected to the external corrosion liquid filling and circulating temperature control pipeline (3), and the other end is connected to the 1# annular filler (24) and the 2# annular filler (25) respectively; the 1# The annular injector (24) and the 2# annular injector (25) are annular pipe structures with an opening at the top. The annular pipes are provided with 8 corrosion liquid injection nozzles (42) which are unevenly distributed in a direction vertical to the ground. The nozzle arrangement scheme is to arrange the 8 nozzles at positions of 0°, 36°, 72°, 108°, 144°, 180°, 225° and 315° of the annular injector in a clockwise direction. The 1# annular injector (24) and the 2# annular injector (25) are vertically installed in the experimental box (1) and are placed around the experimental pipe section (23). The internal and external corrosion measurement unit comprises an internal corrosion measurement unit and an external corrosion measurement unit; the external corrosion measurement unit is led out from the electrochemical workstation (40), connected to the experimental box (1) through the top opening of the experimental box (1) and connected to the 1# three-electrode system (33) and the 2# three-electrode system (35); the top of the electrochemical workstation (40) is connected to the 1# power supply (39); the internal corrosion measurement unit is led out from the display (31), connected to the experimental box (1) through the top opening of the experimental box (1) and connected to the internal corrosion probe (30); the soil physical property monitoring and control The node unit is led out from the display (31), and connected to the temperature measuring probe (28) and the soil pH value measuring probe (29) in the experimental box (1) through a hole in the top of the experimental box (1); the internal corrosion probe (30) is installed in the experimental pipe section (23) through a hole; the 1# three-electrode system (33), the 2# three-electrode system (35), the temperature measuring probe (28), and the soil pH value measuring probe (29) are fixedly installed on the outer surface of the experimental pipe section (23); and the soil pH adjustment and filling device (41) is fixedly installed on the top of the experimental box (1).

2. A method for testing internal and external corrosion of a buried crude oil pipeline, implemented by using a device for testing internal and external corrosion of a buried crude oil pipeline as claimed in claim 1, characterized in that: The steps include: S1, according to the experimental requirements, the type of corrosive ions is selected, and a certain amount of an external corrosive medium solution and an internal corrosive medium solution containing a certain concentration of the selected corrosive ions are prepared, and a certain amount of a soil pH adjustment solution and a certain concentration are prepared according to the experimental requirements, and then the external corrosive medium solution, the internal corrosive medium solution, and the soil pH adjustment solution are respectively added to the liquid storage tank (6), the internal corrosive liquid sprayer (13), and the soil pH adjustment filling device (41); S2, determine the metal material and length, diameter, and wall thickness parameters of the pipeline according to the experimental requirements, make an experimental box (1) and an experimental pipe section (23), install the experimental pipe section (23) equipped with an internal corrosion probe (30), a 1# annular injector (24), and a 2# annular injector (25) into the experimental box (1), connect the experimental box (1) to the pipeline (2) through a flange (20), and then install the 1# three-electrode system (33), the 2# three-electrode system (35), the temperature measurement probe (28), and the soil pH value measurement probe (29) to a fixed position; S3, open the ball valve (10), inject the crude oil in the oil storage tank (8) into the buffer tank (11), then turn on the agitator (12) and the internal corrosion liquid sprayer (13), and prepare the test crude oil containing a certain concentration of internal corrosion ions in the buffer tank (11); S4, open the 1# throttle valve (7), inject the external corrosion medium solution prepared in the liquid storage tank (6) into the external corrosion liquid filling and circulating temperature control pipeline (3), and according to the soil conditions at the site of the crude oil pipeline burial, dig soil on site and fill it into the experimental box (1), then seal the experimental box (1), close the 1# throttle valve (7), open the 3# throttle valve (44), the 4# throttle valve (45), the 1# heater (5) and the material pump (4), increase the operating power of the 1# heater (5), and quickly preheat the added soil to the temperature required for the experiment; S5, close the drain valve (18), open the 3# solenoid valve (14), the check valve (15), the 5# throttle valve (46), the 6# throttle valve (48), the circulation pump (16) and the 2# heater (47) in sequence, and adjust the speed of the circulation pump (16) and the power of the heater (47) so that the experimental crude oil in the pipeline (2) reaches the flow rate and temperature required for the experiment; S6, turn on the display (31), computer (37), electromagnetic relay (38), 1# power supply (39), electrochemical workstation (40), 2# power supply (49), turn off 1# programmable time controller (36) and 2# programmable time controller (50), measure the soil pH value at this time, and carry out the internal and external corrosion pre-experiment for 48 hours; starting from time 0, measure and record the maximum corrosion depth d (in mm) of the corrosion point of the experimental pipe section every 6 hours, which is recorded as d n0 d n1 d n2 d n3 d n4 d n5 d n6 d n7 d n8 d w0 d w1 d w2 d w3 d w4 d w5 d w6 d w7 d w8 , where the subscript n represents internal corrosion and the subscript w represents external corrosion; S7, according to the experimental requirements, the experimental period is set to T days, T>2, and the crude oil flow rate after the 3# solenoid valve (14) is opened is set to S by using the 2# programmable time controller (50). 油 , use 1# programmable time controller (36) to set the flow rate of ionized water flowing out after 1# solenoid valve (32) and 2# solenoid valve (34) are opened to S 水 , using the 2# programmable time controller (50) to set the opening time of the 3# solenoid valve (14) to t1 every 24 hours, and using the 1# programmable time controller (36) to set the opening time of the 1# solenoid valve (32) and the 2# solenoid valve (34) to t2 / 2; S8, conducting formal experiments on internal corrosion and external corrosion, adjusting the speed of the circulation pump (16), the power of the No. 1 heater (5), the power of the No. 2 heater (47), and the soil pH adjustment and injection device (41), obtaining and recording the internal and external corrosion rates of the experimental pipe section (23) under different working conditions; S9, after the experiment is finished, open the drain valve (18), turn off the 1# heater (5), 5# throttle valve (46), 2# heater (47), 6# throttle valve (48), circulation pump (16), material pump (4), 1# power supply (39) and 2# power supply (50) in sequence, take out the experimental soil and experimental pipe section (23), organize other experimental measurement equipment, and process the experimental data; The method for calculating the opening time t1 of the 3# electromagnetic valve (14) every 24 hours and the opening time t2 / 2 of the 1# electromagnetic valve (32) and the 2# electromagnetic valve (34) every 24 hours in step S7 comprises the following steps: Step 1: Calculate the internal corrosion growth and external corrosion growth every 6 hours during the 48 hours of the pre-experiment and record them as Δd ni and Δd wi , △d ni =d ni -d n(i-1) ,△d wi =d wi -d w(i-1 ), i = 1, 2, 3, ..., 8; the corrosion growth Δd in each 6-hour interval within 48 hours of the pre-experiment is calculated in the following formula respectively ni , External corrosion growth Δd wi The mean μ and standard deviation σ of Step 2: Use the probability density function of the gamma distribution of the gamma degradation model to calculate the corrosion growth Δd in the pipeline every 6 hours after 48 hours of the pre-experiment. nj and external corrosion growth Δd wj , j = 9, 10, 11, ..., k, k = 4 (T-2), the corrosion growth of the pipeline inside and outside every 6 hours after 48 hours of the pre-experiment Δd j Obey the probability density function: Where: A—function shape parameter; β—function scale parameter, β>0; Γ(A)—Gamma function with A as variable; In step 2, the values ​​of A and β are calculated using moment parameter estimation, and the calculation formulas are as follows: A=β 2 s 2 ; β = A / μ; Step 3: Based on the corrosion growth Δd of the pipeline inside and outside every 6 hours within 48 hours of the preliminary experiment, ni With Δd wi , the corrosion growth of the pipeline inside and outside every 6 hours after 48 hours of the pre-experiment Δd nj With Δd wj The total depth of internal corrosion y in the experimental period is calculated in turn. n , total depth of external corrosion y w , average internal corrosion rate v n , average external corrosion rate v w , the calculation formula is: Where: ρ—pipeline steel density, kg / m 3 ; y—total corrosion depth during the experimental period, mm; v—average corrosion rate during the experimental period, g / (m 2 s); Step 4: Use the following formula to calculate the average internal corrosion rate v n and S 油 Calculate the opening time of 3# solenoid valve (14) every 24 hours as t1, according to the average external corrosion rate v w and S 水 Calculate the total opening time t2 of the 1# solenoid valve (32) and the 2# solenoid valve (34) every 24 hours: Where, L is the length of the experimental pipe section, m; D—outer diameter of the experimental pipe section, m; v—average corrosion rate during the experimental period, g / (m 2 s); m Fe —Relative atomic mass of iron; m—relative atomic mass of corrosive ions; T—experimental period, days; S—Flow rate of ionized water or crude oil flowing out after opening the solenoid valve, m 3 / s; t—solenoid valve opening time, s; c—Corrosive ion concentration, g / m 3 .

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