A testing method for the maximum wall thickness reduction of the heating surface during the safe operation of a power station boiler

Abstract

The present invention provides a test method for the maximum wall thickness reduction of the heating surface during the safe operation of a power station boiler. For the selected test components, actual operating condition parameters are collected (the main data collected are temperature and pressure), and this data is used as the parameters of the experiment. The temperature and tensile force of the creep testing machine are precisely controlled by a computer to conduct variable parameter creep performance tests. Multiple specimens with different wall thickness reductions are processed for the test. Based on the specimen with a 30% wall thickness reduction, the creep test time is selected as 6 months (4320 hours). After the test, high-temperature tensile tests are conducted on all specimens to obtain the yield strength and tensile strength of each specimen, and a comparison curve is established. The wall thickness reduction at the intersection point between the parameter specimen and the 30% wall thickness reduction specimen is used as the replacement standard to guide the use and replacement of materials.

Description

Technical Field

[0001] The invention relates to the technical field of boiler testing, and in particular to a method for testing a maximum reduction in thickness of a heating surface of a power station boiler during safe operation. Background Art

[0002] The heating surface of a power plant boiler includes water-cooled walls, superheaters, reheaters and economizers, which are located around and inside the furnace. They are the main heat exchange components of the boiler and are also subject to the harshest environment of the boiler. The lower water-cooled wall directly bears the high temperature generated by fuel combustion, and other heating surfaces are subjected to the erosion of high-temperature flue gas and high-speed flue gas. In addition, in order to prevent slag inclusion in the heating surface, the boiler is also equipped with a soot blower to blow soot on the heating surface regularly.

[0003] The erosion and thinning of the heating surface is a common hidden danger that cannot be cured. According to relevant standards, if the thinning of the heating surface exceeds 30%, it should be replaced. 30% is the value calculated based on the design conditions to ensure safe operation. However, with the adjustment of the industry, most units are currently involved in peak load regulation, and some units are even involved in deep peak load regulation. In this way, when operating under variable load conditions, the original design of 30% cannot fully guarantee the safe operation of the boiler, and there is a risk of leakage.

[0004] Therefore, it is necessary to invent a test method for the maximum thinning of the heating surface wall thickness for safe operation of power station boilers. The maximum thinning of the heating surface thickness to ensure safe and stable operation of the unit under variable operating conditions can be determined through experiments, which can serve as a standard for guiding whether the heating surface should be replaced during boiler maintenance.

[0005] Therefore, it is necessary to provide a testing method for the maximum thinning amount of the heating surface wall thickness for safe operation of power station boilers to solve the above technical problems. Summary of the invention

[0006] The present invention provides a method for testing the maximum thinning amount of the wall thickness of the heating surface of a power station boiler for safe operation, which solves the problem that most units currently participate in peak regulation, and some units even participate in deep peak regulation. When operating under variable load conditions, 30% of the original design cannot fully guarantee the safe operation of the boiler, and there is a risk of leakage.

[0007] In order to solve the above technical problems, the present invention provides a method for testing the maximum wall thickness reduction of the heating surface of a power station boiler for safe operation, comprising the following steps:

[0008] S1. Select specific units: such as units that participate in peak load regulation for a long time, have large operating load fluctuations, have many non-stop situations, and the causes are difficult to find;

[0009] S2. Select new tubes for corresponding parts: process the samples according to standard requirements, use angle grinder to thin them, the thinning position is in the middle of the sample, and the thinning amount is 15%, 20%, 22%, 24%, 26%, 28% and 30% respectively;

[0010] S3. Specimen parameter test: directly read the temperature parameter in the MIS system by the computer, control the test temperature through the temperature sensor, compare the pressure parameter with the designed pressure to obtain the comparison coefficient μ, and the test tensile force a1 is: a1 = μa;

[0011] S4. High-temperature tensile test: after the test, conduct a high-temperature tensile test on the specimen, select the temperature as the designed temperature, and obtain the yield strength and tensile strength of each specimen;

[0012] S5. Processing of thinned specimens: take the converted value of the minimum wall thickness of the specimen measured by the thickness gauge as the set thinning amount. The thinned part of the specimen has a smooth transition, without defects such as sharp corners and scratches. The surface roughness of the specimen is not greater than Ra25. Determine uniform thinning and local thinning according to the ratio of the pipe diameter to the thinning length. Let the pipe diameter / thinning length = 1 / 3. If it is less than 1 / 3, it is defined as uniform thinning; if it is greater than or equal to 1 / 3, it is defined as local thinning.

[0013] Preferably, in the step S1, specific components are selected for testing, such as components prone to leakage, severely aged components, and components damaged by blowing, etc. Select a representative operating period in the MIS system, and retrieve and download the temperature and pressure parameters.

[0014] Preferably, in the step S2, a thickness gauge is used for thickness verification during processing. The test temperature of the 30% thinned specimen is the designed temperature, and the test tensile force a is the creep strength of the material at the designed temperature.

[0015] Preferably, in the step S3, the test time is selected as 6 months (4320 hours). The retrieval of test parameters can be selected according to the test time, or individual periods can be selected for cycling.

[0016] Preferably, in the step S4, with the thinning amount as the abscissa and the yield strength and tensile strength as the ordinates respectively, establish coordinate axes and make a comparison curve. The mechanical properties of the material will decline during variable parameter operation. Select the thinning amount corresponding to the point with the same mechanical properties as the 30% thinned specimen as the actual thinning amount used. Connect the tensile strength values of the variable parameter operation specimens into a curve. Draw a horizontal line with the tensile strength of the 30% thinned specimen and intersect it with the curve at point A. Then the thinning amount corresponding to point A is the required thinning amount of 24.5%.

[0017] Preferably, in step S5, the specimen is subjected to local thinning test or uniform thinning test according to requirements. A professional software is designed in the computer of the conventional creep test device. This software has functions of reading MIS temperature and pressure parameters, calculating test tensile force by comparing pressure parameters with designed pressure, controlling temperature with variable parameters, and controlling tensile force with variable parameters. Using this method, no additional hardware costs are required, and only a small control software needs to be designed. The selected test time is 6 months (4320 hours), which is basically the same as the interval between power station unit maintenance cycles. The test time is selected according to the actual situation of the unit. Other values can also be selected for the thinning amount. Among the values of yield strength and tensile strength corresponding to the thinning amount obtained in step 8, the smaller value is taken as the final test result.

[0018] Compared with the related technology, the test method for the maximum wall thickness thinning amount of the heat - receiving surface for safe operation of a power station boiler provided by the present invention has the following beneficial effects:

[0019] The present invention provides a test method for the maximum wall thickness thinning amount of the heat - receiving surface for safe operation of a power station boiler. This method uses a creep testing machine as the basic test equipment. For the selected test components, actual operating condition parameters (the main data collected are temperature and pressure) are collected, and this data is used as the experimental parameters. The computer precisely controls the temperature and tensile force of the creep testing machine to conduct variable - parameter creep performance tests. Multiple specimens with different thinning amounts are processed for the test. Based on the specimen with a 30% thinning amount, the creep test time is selected as 6 months (4320 hours). After the test, high - temperature tensile tests are carried out on all specimens to obtain the yield strength and tensile strength of each specimen, and a comparison curve is established. The thinning amount at the intersection point of the parameter specimen and the 30% thinning amount specimen is used as the replacement standard to guide the use and replacement of materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic structural diagram of a preferred embodiment of the test method for the maximum wall thickness thinning amount of the heat - receiving surface for safe operation of a power station boiler provided by the present invention;

[0021] Figure 2 is a curve graph of the thinning amount corresponding to the yield strength and tensile strength. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention will be further described below in conjunction with the drawings and embodiments.

[0023] Please refer to Figure 1-2 , wherein, Figure 1 is a schematic structural diagram of a preferred embodiment of the test method for the maximum wall thickness thinning amount of the heat - receiving surface for safe operation of a power station boiler provided by the present invention; Figure 2 is a curve graph of the thinning amount corresponding to the yield strength and tensile strength. Embodiment 1

[0024] Testing method for maximum wall thickness reduction of heat transfer surfaces during safe operation of utility boilers, comprising the following steps:

[0025] S1. Select a specific unit: such as a unit that has been participating in peak shaving for a long time, has large fluctuations in operating load, has many non-stop situations, and is difficult to find the reasons, etc. Select specific components, such as components prone to leakage, severely aged components, components damaged by blowing, etc. for testing. Select a representative operating period in the MIS system, and retrieve and download temperature and pressure parameters;

[0026] S2. Select new tubes for the corresponding components: Process specimens according to standard requirements, use a angle grinder to reduce the thickness. The reduction position is selected in the middle of the specimen. The reduction amounts are respectively selected as 15%, 20% and 22%. Use a thickness gauge to check the thickness during processing. The test temperature of the 30% reduction specimen is the design temperature, and the test tensile force a is the creep strength of the material at the design temperature;

[0027] S3. Specimen parameter test: Directly read the temperature parameters in the MIS system by the computer, control the test temperature through a temperature sensor, compare the pressure parameter with the design pressure to obtain the comparison coefficient μ. The test tensile force a1 is: a1 = μa. The test time is selected as 6 months (4320 hours). The retrieval of test parameters can be selected according to the test time, or individual periods can be selected for cycling;

[0028] S4. High-temperature tensile test: After the test, conduct a high-temperature tensile test on the specimen. The temperature is selected as the design temperature to obtain the yield strength and tensile strength of each specimen. Take the reduction amount as the abscissa, and the yield strength and tensile strength as the ordinates respectively to establish coordinate axes and make a comparison curve. Figure 2 Taking the tensile strength as the ordinate, variable parameter operation will cause the mechanical properties of the material to decline. Select the reduction amount corresponding to the point with the same mechanical properties as the 30% reduction specimen as the reduction amount for actual use. Connect the tensile strength values of the variable parameter operation specimens into a curve. Draw a horizontal line with the tensile strength of the 30% reduction specimen and intersect the curve at point A. Then the reduction amount corresponding to point A is the reduction amount of 24.5% to be obtained;

[0029] S5. Thinning specimen processing: Taking the converted value of the minimum wall thickness of the specimen measured by a thickness gauge as the set thinning amount, the thinning part of the specimen has a smooth transition, without defects such as edges, corners, and scratches. The surface roughness of the specimen is not greater than Ra25. According to the ratio of the pipe diameter to the thinning length, uniform thinning and local thinning are determined. Let the pipe diameter / thinning length = 1 / 3. If it is less than 1 / 3, it is defined as uniform thinning; if it is greater than or equal to 1 / 3, it is defined as local thinning. The specimen is subjected to local thinning test or uniform thinning test according to requirements. A professional software is designed in the computer of the conventional creep test device. This software has functions such as reading MIS temperature and pressure parameters, calculating the test tensile force by comparing the pressure parameter with the design pressure, controlling the temperature with variable parameters, and controlling the tensile force with variable parameters, etc. Using this method, no additional hardware costs are required, and only a small control software needs to be designed. The selected test time is 6 months, 4320 hours, which is basically the same as the interval between the maintenance periods of power station units, and can ensure the safe operation of the unit to the greatest extent. The test time can also be selected according to the actual situation of the unit. Other values can also be selected for the thinning amount. Among the values of the yield strength and tensile strength corresponding to the thinning amount obtained in the 8th step, the smaller value is taken as the final test result. Example 2

[0030] A test method for the maximum thinning amount of the wall thickness of the heating surface for the safe operation of a power station boiler, comprising the following steps:

[0031] S1. Select a specific unit: Such as a unit that participates in peak shaving for a long time, has large fluctuations in operating load, has many outages, and is difficult to find the reasons, etc. Select specific components, such as components prone to leakage, severely aged components, components damaged by blowing, etc. for testing. Select a representative operating period in the MIS system and download the temperature and pressure parameters.

[0032] S2. Select new pipes for the corresponding components: Process the specimens according to the standard requirements, use a angle grinder for thinning, select the thinning position in the middle of the specimen, and the thinning amounts are respectively selected as 24%, 26%, 28%, and 30%. Use a thickness gauge to check the thickness during processing. The test temperature of the 30% thinned specimen is the design temperature, and the test tensile force a is the creep strength of the material at the design temperature.

[0033] S3. Specimen parameter test: Directly read the temperature parameter in the MIS system by the computer, control the test temperature through a temperature sensor, compare the pressure parameter with the design pressure to obtain the comparison coefficient μ, and the test tensile force a1 is: a1 = μa. The test time is selected as 6 months, 4320 hours. The retrieval of test parameters can be selected according to the test time or individual periods can be selected for cycling.

[0034] S4. High-temperature tensile test: After the test, conduct a high-temperature tensile test on the specimen at the designed temperature. Obtain the yield strength and tensile strength of each specimen. Use the thinning amount as the abscissa and the yield strength and tensile strength as the ordinates respectively to establish coordinate axes and draw a comparison curve. Figure 2 Taking the tensile strength as the ordinate, variable parameter operation will cause the mechanical properties of the material to decline. Select the thinning amount corresponding to the point with the same mechanical properties as the 30% thinned specimen as the actual thinning amount used. Connect the tensile strength values of the variable parameter operation specimens into a curve. Draw a horizontal line with the tensile strength of the 30% thinned specimen and intersect the curve at point A. Then the thinning amount corresponding to point A is the required thinning amount of 24.5%.

[0035] S5. Thinned specimen processing: Use the measured minimum wall thickness conversion value of the specimen by the thickness gauge as the set thinning amount. The thinned part of the specimen has a smooth transition without defects such as edges, corners, and scratches. The surface roughness of the specimen is not greater than Ra25. Determine uniform thinning and local thinning according to the ratio of the pipe diameter to the thinning length. Let the pipe diameter / thinning length = 1 / 3. If it is less than 1 / 3, it is defined as uniform thinning; if it is greater than or equal to 1 / 3, it is defined as local thinning. The specimen is tested for local thinning or uniform thinning according to requirements. Design professional software in the computer of the conventional creep test device. This software has functions such as reading MIS temperature and pressure parameters, comparing pressure parameters with the designed pressure to calculate the test tension, variable parameter temperature control, and variable parameter tension control. Using this method, no additional hardware costs are required, only a small control software needs to be designed. The selected test time is 6 months (4320 hours), which is basically the same as the interval between power station unit maintenance cycles, and can ensure the safe operation of the unit to the greatest extent. The test time can also be selected according to the actual situation of the unit. For the selected thinning amount, other values can also be taken. Among the values of the yield strength and tensile strength corresponding to the thinning amount obtained in step 8, take the smaller value as the final test result.

[0036] 1. Select a unit and a specific component.

[0037] 2. Find spare new pipes to process specimens and process specimens according to test standards.

[0038] 3. Process thinned specimens according to the preset thinning amount. The 30% thinned specimen is the basic specimen (must be processed).

[0039] 4. Collect the operating conditions of the unit, import the temperature parameters into the computer of the test device, compare the pressure parameters with the conventional test parameters, and convert them into tension parameters and import them into the computer of the test device.

[0040] 5. Install the processed specimens into the test device.

[0041] 6. Start the creep test.

[0042] 7. After the creep test, high-temperature tensile tests are conducted on all specimens to obtain the yield strength and tensile strength.

[0043] 8. Plot a curve graph to obtain the wall thickness reduction corresponding to the yield strength and tensile strength respectively, and take the lower of the two as the final test result.

[0044] The working principle of the method for testing the maximum wall thickness reduction of the heat-absorbing surface for safe operation of a power plant boiler provided by the present invention is as follows: This method is applicable to testing the maximum wall thickness reduction of the heat-absorbing surface of a power plant boiler and is also applicable to other high-temperature and high-pressure components in the power plant; this method collects actual operating parameters, has a high degree of compliance with the actual working conditions, and has high practicability; the test device adds a computer control system on the basis of the original creep machine and can be completed through device transformation, saving costs.

[0045] Compared with the related technologies, the method for testing the maximum wall thickness reduction of the heat-absorbing surface for safe operation of a power plant boiler provided by the present invention has the following beneficial effects:

[0046] This method is applicable to testing the maximum wall thickness reduction of the heat-absorbing surface of a power plant boiler and is also applicable to other high-temperature and high-pressure components in the power plant; this method collects actual operating parameters, has a high degree of compliance with the actual working conditions, and has high practicability; the test device adds a computer control system on the basis of the original creep machine and can be completed through device transformation, saving costs.

[0047] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are equally included in the patent protection scope of the present invention.

Claims

1. A test method for the maximum wall thickness reduction of the heating surface during the safe operation of a power station boiler, characterized in that It includes the following steps: S1. Select specific units: units that participate in peak shaving for a long time, have large fluctuations in operating load, or have many non-stop situations; select specific components: select components that are prone to leakage, severely aged, or damaged by blowing for testing; select representative operating periods in the MIS system, and download temperature and pressure parameters. S2. Select new pipes for the corresponding components: process specimens according to standard requirements, thin them with a grinding wheel, select the middle of the specimen as the thinning position, and select thinning amounts of 15%, 20%, 22%, 24%, 26%, 28%, and 30% respectively. The test temperature of the specimen with a 30% thinning amount is the design temperature, and the design tensile force a is the creep strength of the material at the design temperature. S3. Specimen parameter test: directly read the temperature parameter in the MIS system by the computer, control the test temperature to be consistent with the temperature parameter through a temperature sensor, compare the pressure parameter with the design pressure to obtain the comparison coefficient μ, and the test tensile force a1 is: a1 = μa. The specimen parameter test is to conduct a variable parameter creep test on the thinned specimen at the above test temperature and test tensile force. S4. High-temperature tensile test: After the test, conduct a high-temperature tensile test on the specimen, select the temperature as the design temperature, obtain the yield strength and tensile strength of each specimen, establish coordinate axes with the thinning amount as the abscissa and the yield strength and tensile strength as the ordinates respectively, connect the yield strength and tensile strength of each specimen into curves, and select the thinning amount corresponding to the point on the curve with the same yield strength value or tensile strength value as the specimen with a 30% thinning amount as the maximum thinning amount.

2. The test method for the maximum wall thickness reduction of the heat-absorbing surface for the safe operation of a power station boiler according to claim 1, wherein In step S2, a thickness gauge is used for thickness verification during processing.

3. The test method for the maximum wall thickness reduction of the heat-absorbing surface during the safe operation of a utility boiler according to claim 1, characterized in that, In step S3, the test time is selected as 6 months, and the retrieval of test parameters in step S1 is selected according to the test time, or individual periods are selected for cycling.

4. The test method for the maximum wall thickness reduction of the heat-absorbing surface during the safe operation of a power station boiler according to claim 1, characterized in that, Design professional software in the computer of the conventional creep test device. This software simultaneously has the functions of reading MIS temperature and pressure parameters, calculating the test tensile force by comparing the pressure parameter with the design pressure, controlling the temperature with variable parameters, and controlling the tensile force with variable parameters.

5. The test method for the maximum wall thickness reduction of the heat-absorbing surface during the safe operation of a power station boiler according to claim 1, characterized in that, Among the thinning amounts corresponding to the points on the curve with the same yield strength value or tensile strength value as the specimen with a 30% thinning amount obtained in step S4, take the smaller value as the final test result.

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