An Online Calibration Method for Safety Valves in Ultra-Supercritical Boilers

Abstract

This invention relates to the field of valve calibration methods, specifically to an online calibration method for safety valves in ultra-supercritical boilers. The method includes a warm-up operation and the sequential opening and closing of various valves or gate valves. First, the system pressure of the unit is stabilized to be less than 0.5 MPa below the safety valve's tripping pressure. Then, the first and second inlet electric gate valves are opened. By increasing or decreasing the unit's fuel supply and simultaneously controlling the opening of the turbine's main control valves, the safety valve is tripped and reseated. This invention reduces the impact on grid load and unit parameters, is easy to operate, and prevents the safety valve from experiencing frequent tripping, vibration, or other abnormalities.

Description

Technical Field

[0001] This invention relates to the field of valve calibration methods, and specifically to an online calibration method for a safety valve in an ultra-supercritical boiler. Background Technology

[0002] A boiler safety valve is a valve located at the top of the boiler, near the control room, to prevent the boiler pressure from exceeding the specified pressure. When the boiler pressure exceeds the specified level, the safety valve automatically opens, releasing steam to reduce the pressure. When the pressure drops to the specified level, the safety valve automatically closes, stopping the steam release and pressure reduction. The boiler safety valve is a crucial component ensuring the safe operation of the boiler; therefore, performance verification tests are necessary.

[0003] During boiler safety valve testing, the system pressure of the unit is first increased to above the safety valve's tripping pressure. Then, the primary and secondary electric gate valves are opened to allow high-pressure steam to enter the test pipeline, and the pressure in the test pipeline is gradually increased until the safety valve trips. However, during the test, if the steam trap and PCV valve are in the closed state, and then the primary and secondary electric gate valves are closed to reseat the safety valve, the safety valve will experience frequent tripping and vibration. If the steam trap and PCV valve are in the open state, and the primary and secondary electric gate valves are closed to reseat the safety valve, although frequent tripping will not occur, the operation is complex and has a significant impact on unit load, steam temperature, steam pressure, and other parameters, making it difficult to control. Summary of the Invention

[0004] The present invention aims to provide an online calibration method for safety valves in ultra-supercritical boilers, in order to solve the problems of frequent jumping and vibration of safety valves in existing testing methods.

[0005] The online calibration method for safety valves in ultra-supercritical boilers in this scheme includes the following steps:

[0006] S1. A test circuit was built by opening a hole in the outlet pipe on one side of the final stage superheater, and the installation and commissioning were completed to ensure that all valves were switched on and off normally, and that the control circuit and thermal measuring points were working normally.

[0007] S2, to debug and control the test circuit and the unit, keep the unit load at the preset load, keep the main steam pressure of the test circuit within 22MPa, and keep the parameters of each component in the test circuit running stably.

[0008] S3, close the two bypass valves of the first inlet electric gate valve on the test pipeline according to the preset frequency range, and close the third bypass electric gate valve of the second inlet electric gate valve, open all the drain gate valves on the test circuit, and keep the power relief valve at the outlet on one side of the superheater closed.

[0009] S4, by adding fuel to the boiler, the main steam pressure is increased at a set rate of change, the unit load is increased to a preset multiple of the preset load, the main steam pressure is increased to 23.5 MPa, and the intermediate superheat is increased according to the threshold. After the parameters of each component in the test circuit are stable, proceed to S5.

[0010] S5, manually adjust and control the test circuit and the unit, close the main control valve of the steam turbine according to the preset frequency range, and increase the main steam pressure to 25MPa;

[0011] S6, When the safety valve of the test circuit pipeline is activated, increase the turbine main control valve according to the preset frequency range and increase the boiler fuel according to the preset amount;

[0012] S7. After the pipeline safety valve reseated, reduce the fuel and stabilize the main steam pressure at 22.5MPa. Adjust the unit to automatic control and complete the first hot test of the pipeline safety valve.

[0013] S8. Repeat S4-S7 twice more at the preset interval to conduct the second hot test and the third hot test of the pipeline safety valve, respectively.

[0014] S9. After completing the three tests of the pipeline safety valve, reduce the fuel and stabilize the main steam pressure at 22.5MPa. Then, open the third bypass electric valve of the second inlet electric gate valve of the test circuit, close all the drain valves in the test circuit, close the second inlet electric gate valve of the test circuit, and finally close the third bypass electric valve of the second inlet electric gate valve of the test circuit to conduct a sealing test. After the sealing test is completed, open all the drain valves of the test circuit to complete the pipeline safety valve test.

[0015] Furthermore, it also includes the following steps:

[0016] S10, after completing the pipeline safety valve test, conduct a hot test of the power relief valve at the superheater outlet on one side within a preset time period, keep the pipeline safety valve in the closed state, then open the third bypass electric valve of the second inlet electric gate valve of the test circuit, then open the second inlet electric gate valve of the test circuit, and finally close the third bypass electric valve of the second inlet electric gate valve of the test circuit to resume the test. Repeat S4-S7 three times according to the preset interval.

[0017] S11. After completing the hot test of the power relief valve, repeat step S9 to conduct the sealing test.

[0018] Furthermore, in S10, the preset time is 20-30 minutes. When the power relief valve hot test is performed after the preset time has been exceeded, step S2 is repeated to warm up the pipe.

[0019] Furthermore, in step S2, the debugging control includes the following sub-steps:

[0020] S2.1, open the manual valves of the two local pressure gauges and two pipeline pressure transmitters in the test circuit, open the electric drain valve and the manual drain valve in front of the electric gate valve of the steam inlet in the test circuit, and after the test pipeline of the test circuit has been fully warmed up for a set time, open the manual drain valve and the electric drain valve of the pipeline.

[0021] S2.2, remotely open the third bypass electric valve of the second steam inlet electric gate valve, and locally open the first bypass electric valve and the second bypass electric valve of the first steam inlet electric gate valve according to the test pipeline pressure, temperature rise and vibration conditions of the test circuit within a preset frequency range, and control the temperature and pressure of the test pipeline to gradually rise through the first bypass electric valve and the second bypass electric valve.

[0022] S2.3 After the pipe has been sufficiently drained and warmed up, open the first and second inlet steam electric gate valves locally according to the preset frequency range to allow the pressure in the test pipeline to gradually increase, and open the pipeline PCV valve to purge the test circuit for the set duration.

[0023] Furthermore, in S2.3, the setting duration is greater than or equal to 30 seconds.

[0024] Furthermore, the preset interval is 20-30 minutes.

[0025] Furthermore, in step S6, when the main steam pressure increases to 25 MPa and the pipeline safety valve does not activate, the main steam pressure continues to increase and is maintained at less than or equal to 25.5 MPa. If the pipeline safety valve still does not activate, the test is stopped and the main steam pressure is reduced to 23.5 MPa.

[0026] Furthermore, while closing the first and second inlet steam electric gate valves, the power is kept off. When closing the manual and electric drain valves of the pipeline, the pressure in the test circuit is kept from rising. After the manual and electric drain valves of the pipeline are closed, the power is kept off.

[0027] Furthermore, during the warm-up process, it is determined whether the test pipeline is vibrating. If the test pipeline is vibrating, the bypass regulating valve of the first steam inlet electric gate valve is closed.

[0028] Furthermore, the criteria for determining whether the pipe has been fully warmed up are: after warming up, the temperature of the drain pipe in the test circuit is not less than 400℃.

[0029] Compared with existing technologies, the beneficial effects of this solution are:

[0030] When conducting boiler safety valve tests, this method ensures the safety of each valve or gate valve in the test circuit by performing warm-up operations and opening or closing each valve or gate valve sequentially, preventing damage during the test. First, when the system pressure of the unit is stabilized to be less than 0.5MPa below the safety valve's opening pressure, the first and second inlet electric gate valves are opened. By increasing or decreasing the unit's fuel supply and simultaneously controlling the opening of the turbine's main control valve, the safety valve is activated and reseated. This reduces the impact on the grid load and unit parameters, is easy to operate, and prevents the safety valve from experiencing abnormal conditions such as frequent tripping or vibration. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating an embodiment of the online calibration method for safety valves in ultra-supercritical boilers according to the present invention.

[0032] Figure 2 This is a schematic diagram of the test circuit in an embodiment of the online calibration method for safety valves in ultra-supercritical boilers of the present invention;

[0033] Figure 3 This is a pressure-time curve from a test conducted in an embodiment of the online calibration method for safety valves in ultra-supercritical boilers according to the present invention.

[0034] Figure 4 The pressure and time curves for the secondary test in an embodiment of the online calibration method for the safety valve of an ultra-supercritical boiler of the present invention are shown.

[0035] Figure 5 The displacement-time curve is shown in the embodiment of the online calibration method for safety valves of ultra-supercritical boilers of the present invention, representing a single test.

[0036] Figure 6 The displacement-time curves are from a secondary test in an embodiment of the online calibration method for safety valves in ultra-supercritical boilers of the present invention. Detailed Implementation

[0037] The following detailed description provides further details on specific implementation methods.

[0038] The reference numerals in the accompanying drawings include: 1. First inlet electric gate valve; 2. Second inlet electric gate valve; 3. Pipeline PCV valve; 4. Pipeline safety valve; 5. First bypass electric valve; 6. Second bypass electric valve; 7. Third bypass electric valve; 8. Manual drain valve before the inlet electric gate valve; 9. Manual drain valve before the inlet electric gate valve; 10. Pipeline drain valve; 11. Primary sampling valve for local pressure gauge 1; 12. Secondary sampling valve for local pressure gauge 1; 13. Primary sampling valve for local pressure gauge 2; 14. Secondary sampling valve for local pressure gauge 2; 15. Primary sampling valve for pipeline pressure transmitter; 16. Secondary sampling valve for pipeline pressure transmitter; 17. Manual bypass valve; 18.

[0039] Example

[0040] This embodiment of the online calibration method for safety valves in ultra-supercritical boilers is based on a test circuit. The test circuit is constructed based on an actual operating unit in a thermal power plant, specifically on the left-side superheater platform of the boiler. The test circuit is led out from the single-sided outlet pipe opening of the final-stage superheater, as follows: Figure 2 As shown, it includes a test pipeline, one end of which is connected to the boiler. The test pipeline is sequentially equipped with a first steam inlet electric gate valve 1 and a second steam inlet electric gate valve 2.

[0041] The first steam inlet electric gate valve 1 is connected to the boiler via an extension pipe. The steam inlet electric gate valve front drain manual valve 8 and the steam inlet electric gate valve front drain electric valve 9 are connected in series.

[0042] The first steam inlet electric gate valve 1 is provided with a first bypass electric door 5, a second bypass electric door 6 and a bypass manual door 18 through an extension pipe. The bypass manual door 18 is located between the first bypass electric door 5 and the second bypass electric door 6. The bypass manual door 18 is set in series and then connected in parallel outside the first steam inlet electric gate valve 1.

[0043] The second steam inlet electric gate valve 2 is connected in parallel with a third bypass electric gate 7 via a pipe;

[0044] The test pipeline is connected in series with the local pressure gauge sampling primary valve 12 and the local pressure gauge sampling secondary valve 13, which are installed in sequence on the pipeline adjacent to the second steam inlet electric gate valve 2 via an extension pipe.

[0045] A PCV valve 3 is installed on the test pipeline at a position adjacent to the local pressure gauge sampling valve 12 via an extension pipe.

[0046] On the test pipeline, a local pressure gauge sampling primary valve 14 and a local pressure gauge sampling secondary valve 15 are sequentially installed at the position adjacent to the PCV valve 3 via an extension pipe. The local pressure gauge sampling primary valve 14 and the local pressure gauge sampling secondary valve 15 are connected in series.

[0047] On the test pipeline, a pipeline pressure transmitter sampling primary gate 16 and a pipeline pressure transmitter sampling secondary gate 17 are sequentially installed at the position adjacent to the pipeline local pressure gauge sampling primary gate 14 via an extension pipe. The pipeline pressure transmitter sampling primary gate 16 and the pipeline pressure transmitter sampling secondary gate 17 are connected in series.

[0048] A pipeline safety valve 4 is installed on the test pipeline at a position adjacent to the primary sampling valve 16 of the pipeline pressure transmitter via an extension pipe;

[0049] The test pipeline is equipped with a manual drain valve 10 and an electric drain valve 11 at a position adjacent to the pipeline safety valve 4 via an extension pipe. The manual drain valve 10 and the electric drain valve 11 are connected in series.

[0050] The online calibration method for safety valves in ultra-supercritical boilers requires the following main steam parameters: pressure 25 MPa, temperature 605 ± 5℃. The boiler safety valves to be tested in this embodiment include: a superheater outlet safety valve with a discharge capacity of 175 T / h; a superheater inlet safety valve with a discharge capacity of 230 T / h; and a superheater outlet power relief valve with a discharge capacity of 141 T / h. Existing DN65 valves are used for the superheater outlet safety valve and the superheater outlet power relief valve, while existing DN75 valves are used for the superheater inlet safety valve.

[0051] like Figure 1 As shown, it includes the following steps:

[0052] S1. A test loop is constructed by opening a hole in the outlet pipe on one side of the final stage superheater, and installation and commissioning are completed to ensure that all valves operate normally, and that the control loop and thermal measuring points function properly. The control loop can be controlled using existing CCS coordinated control methods. The judgment of normal valve operation and the normal operation of the control loop and thermal measuring points is existing technology and will not be elaborated here. Through the above-mentioned test loop setup, the safety of each valve or gate valve can be guaranteed in the event of test failure or other abnormal situations during the test, ensuring that the valves or gate valves are not damaged.

[0053] S2, Perform commissioning control on the test loop and unit, using the existing CCS coordinated control method to maintain the unit load at a preset load of 500MW, maintain the main steam pressure of the test loop within 22MPa, and ensure stable operation of the parameters of each component in the test loop. The commissioning control includes the following sub-steps:

[0054] S2.1, Open the manual valves of the two local pressure gauges and two pressure transmitters in the test circuit. The local pressure gauges are: Pipeline local pressure gauge 1 sampling primary valve 12, Pipeline local pressure gauge 1 sampling secondary valve 13, Pipeline local pressure gauge 2 sampling primary valve 14, Pipeline local pressure gauge 2 sampling secondary valve 15, and the pressure transmitters are: Pipeline pressure transmitter sampling primary valve 16, Pipeline pressure transmitter sampling secondary valve 17. Open the electric drain valve and the manual drain valve in front of the steam inlet electric gate valve in the test circuit. After the test circuit is fully warmed up for a set time, the condition for sufficient warm-up is: after warm-up, the temperature of the drain pipe in the test circuit is not less than 400℃. Open the manual drain valve and the electric drain valve for 15-25 minutes. By setting the warm-up time range, it is possible to know in time whether the warm-up has reached the sufficient condition while ensuring that the warm-up is sufficient.

[0055] S2.2, remotely open the third bypass electric valve of the second steam inlet electric gate valve, and locally open the first bypass electric valve and the second bypass electric valve of the first steam inlet electric gate valve according to the pressure, temperature rise and vibration of the test pipeline in the test circuit, according to the preset frequency range. The preset frequency range is 1% closing per second. The preset frequency range can be set according to actual needs. For example, the preset frequency range is the valve angle rotated per minute. The temperature and pressure of the test pipeline are gradually increased by controlling the first bypass electric valve and the second bypass electric valve to prevent the temperature or pressure from rising too quickly and causing incorrect test conditions, which would cause repeated debugging and delay the test time.

[0056] S2.3 After sufficient drainage and warming of the pipe, open the first and second inlet steam electric gate valves on-site according to the preset frequency range to gradually increase the pressure in the test pipe. Open the pipe PCV valve to purge the test circuit for a set duration, which is greater than or equal to 30s. By purging the test circuit for a certain duration, the air pressure can be maintained at the required point to ensure sufficient warming of the pipe.

[0057] By gradually adjusting the main steam pressure and temperature during the warm-up operation in step S2, problems such as frequency jumps and vibrations can be prevented, ensuring the safety of each structural component during the test.

[0058] S3, close the two bypass valves of the first inlet electric gate valve on the test pipeline according to the preset frequency range, namely the first bypass electric gate 5 and the second bypass electric gate 6, and close the third bypass electric gate of the second inlet electric gate valve, namely the third bypass electric gate 7. Open all the drain gates on the test circuit, namely the drain manual gate 8 before the inlet electric gate valve, the drain electric gate 9 before the inlet electric gate valve, the drain manual gate 10 on the pipeline, and the drain electric gate 11 on the pipeline. Keep the power relief valve at the outlet on one side of the superheater closed to prevent the pipeline safety valve 4 from malfunctioning.

[0059] S4: The main steam pressure is increased at a set rate of 0.1 MPa / min by adding fuel to the boiler. This allows the main steam pressure to increase slowly and steadily, ensuring that it accurately reaches the target setting. The unit load is increased to a preset multiple of the preset load, which is 1.06, i.e., the unit load is increased to 530 MW. This increases the main steam pressure to 23.5 MPa. The intermediate superheat is also increased to 30°C according to the threshold. After the parameters of each component in the test loop stabilize, the process proceeds to S5.

[0060] S5, manually adjust and control the test circuit and unit, close the main control valve of the steam turbine according to the preset frequency range, and increase the main steam pressure to 25MPa.

[0061] S6. After the safety valve of the test circuit pipeline trips, increase the turbine main control valve according to the preset frequency range, and increase the boiler fuel according to the preset amount. The preset amount is set according to actual needs, such as 1kg.

[0062] If the main steam pressure increases to 25 MPa and the pipeline safety valve does not activate, continue increasing the main steam pressure while maintaining it at 25.5 MPa. If the pipeline safety valve still does not activate, stop the test and reduce the main steam pressure to 23.5 MPa. This ensures the safety of the main control valves and safety valves, preventing valve damage or malfunction caused by abnormal conditions during the test.

[0063] S7. After the pipeline safety valve reseated, reduce the fuel level. The amount of fuel reduction is adjusted according to the actual situation. Stabilize the main steam pressure at 22.5MPa, adjust the unit to automatic control, and complete the first hot test of the pipeline safety valve.

[0064] S8. Repeat S4-S7 twice more at the preset interval to conduct the second and third hot tests of the pipeline safety valve, respectively. The preset interval is 20-30 minutes. The preset interval ensures that the valve or gate valve status will not interfere with each other and affect the test results when conducting the second and third hot tests after the first hot test.

[0065] S9. After completing the three tests of the pipeline safety valve, reduce the fuel and stabilize the main steam pressure at 22.5MPa. Then, open the third bypass electric valve of the second inlet electric gate valve of the test circuit, and immediately close all the drain valves on the test circuit. Then, close the second inlet electric gate valve of the test circuit, and finally close the third bypass electric valve of the second inlet electric gate valve of the test circuit to conduct a sealing test. After the sealing test is completed, open all the drain valves of the test circuit to complete the pipeline safety valve test.

[0066] S10, after completing the pipeline safety valve test, conduct a hot-state test of the power relief valve at one side of the superheater outlet within a preset time period. If the hot-state test of the power relief valve exceeds the preset time period, first repeat step S2 to warm up the pipeline, keeping the pipeline safety valve in the closed state. The preset time period is 20-30 minutes. Then, open the third bypass electric valve of the second inlet electric gate valve of the test circuit, then open the second inlet electric gate valve of the test circuit, and finally close the third bypass electric valve of the second inlet electric gate valve of the test circuit to resume the test. Repeat S4-S7 three times at preset intervals. The preset interval is 20-30 minutes. By limiting the hot-state test on the test circuit to the sealing test, the effectiveness of the warm-up operation under the re-hot-state test can be maintained, avoiding repeated warm-up operation for a single test time.

[0067] S11. After completing the hot test of the power relief valve, repeat step S9 to conduct the sealing test.

[0068] While closing the first and second inlet electric gate valves, keep them de-energized. When closing the manual and electric drain valves, ensure the pressure in the test circuit does not rise. After closing the manual and electric drain valves, keep them de-energized to ensure that the valves or gate valves are not damaged under test conditions and to prevent safety valves from malfunctioning, thereby improving the safety of the test.

[0069] During the warm-up process, it is determined whether the test pipeline is vibrating. When the test pipeline is vibrating, the bypass regulating valve of the first steam inlet electric gate valve 1 is closed. The bypass regulating valve includes the first bypass electric valve 5, the second bypass electric valve 6, and the bypass manual valve 18.

[0070] The first experiment was conducted using the method described above:

[0071] Test Procedure: With the drain valve of the test pipeline fully open, the bypass electric regulating valve is gradually opened to warm the test pipeline to approximately 500℃ and 16MPa. Initially, the safety valve is a mechanical mechanism, and the set-off value after cold-state adjustment may have deviations. If the previous method is followed, frequent tripping of the safety valve occurs during the opening of the first and second inlet electric gate valves. Therefore, the warm-up parameters are reduced for the first hot-state test of each safety valve, and subsequent tests are conducted using the same method. The boiler pressure is controlled at 22MPa, and the electric gate valve is opened. The boiler pressure is increased by enhancing boiler combustion while simultaneously controlling the main steam valve opening, causing the safety valve to trip. After the safety valve trips, the main steam valve is quickly opened to further enhance boiler combustion, causing the safety valve to reseat. Data is directly obtained from the control room to plot the pressure-time curve. Figure 3 As shown. By increasing fuel in the boiler and simultaneously opening the main steam valve to increase the load and reduce the main steam pressure of the unit, the pressure on the test platform decreases, causing the safety valve to reseat. The safety valve displacement versus time curve is shown below. Figure 5 As shown.

[0072] The second experiment was conducted under the same conditions as the first experiment:

[0073] The safety valve opens and reseats smoothly, and the pressure-time curve is as follows: Figure 4 As shown, the displacement versus time curve is as follows: Figure 6 As shown.

[0074] Through the above two operation tests, the safety valve discharge time was maintained at about 1 to 1.5 minutes, the safety valve operation performance was stable, and no harmful phenomena such as frequent jumping occurred. Therefore, the method of this embodiment can solve the problems of frequent jumping and vibration.

[0075] Compared to existing test methods that involve raising the system pressure to the safe trip pressure before opening each gate valve until the safety valve trips, this embodiment first performs a warm-up operation on the test circuit and sequentially opens or closes each valve or gate valve, allowing the main steam pressure in the test circuit to gradually rise and be maintained. This ensures the safety of each gate valve or valve in the test circuit and prevents damage during the test. Through the preceding operations, the system pressure of the unit is stabilized at less than 0.5 MPa below the safety valve trip pressure. At this point, the safety gate valve will not trip. Then, the first and second inlet electric gate valves are opened. By increasing or decreasing the unit's fuel supply and simultaneously controlling the opening of the turbine's main control valves, the safety valve trips and reseats in a timely and safe manner, reducing the impact on unit parameters. This method is easy to operate and prevents abnormal situations such as frequent tripping and vibration of the safety valve.

[0076] Currently, China lacks testing methods for ultra-supercritical safety valves, and actual operating condition tests have never been conducted on units in thermal power plants. This is primarily due to concerns about the impact on unit load. Preliminary estimates suggest that calibrating a 200T / H displacement safety valve affects unit load by approximately 60MW, potentially impacting grid safety. Relying solely on the safety valve's own pressure relief not only results in a long reseating time and erosion of the valve core, but also significantly affects the parameters of the operating unit, severely impacting its safe operation. The method described in this embodiment, based on practically permissible unit conditions, allows for online calibration, completing the test in approximately 1.5 minutes (90 seconds). This not only solves the problem of frequent safety valve tripping but also mitigates disturbances to grid load and impacts on unit parameters. While constructing a dedicated ultra-supercritical boiler for safety valve calibration is simple to operate, its daily utilization rate is low, and maintenance costs are high.

[0077] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for online verification of safety valves in ultra-supercritical boilers, characterized in that, Includes the following steps: S1. A test circuit was built by opening a hole in the outlet pipe on one side of the final stage superheater, and the installation and commissioning were completed to ensure that all valves were switched on and off normally, and that the control circuit and thermal measuring points were working normally. S2, to debug and control the test circuit and the unit, keep the unit load at the preset load, keep the main steam pressure of the test circuit within 22MPa, and keep the parameters of each component in the test circuit running stably. S3, close the two bypass valves of the first inlet electric gate valve on the test pipeline according to the preset frequency range, and close the third bypass electric gate valve of the second inlet electric gate valve, open all the drain gate valves on the test circuit, and keep the power relief valve at the outlet on one side of the superheater closed. S4, by adding fuel to the boiler, the main steam pressure is increased at a set rate of change, the unit load is increased to a preset multiple of the preset load, the main steam pressure is increased to 23.5 MPa, and the intermediate superheat is increased according to the threshold. After the parameters of each component in the test circuit are stable, proceed to S5. S5, manually adjust and control the test circuit and the unit, close the main control valve of the steam turbine according to the preset frequency range, and increase the main steam pressure to 25MPa; S6, When the safety valve of the test circuit pipeline is activated, increase the turbine main control valve according to the preset frequency range and increase the boiler fuel according to the preset amount; S7. After the pipeline safety valve reseated, reduce the fuel and stabilize the main steam pressure at 22.5MPa. Adjust the unit to automatic control and complete the first hot test of the pipeline safety valve. S8. Repeat S4-S7 twice more at the preset interval to conduct the second hot test and the third hot test of the pipeline safety valve, respectively. S9. After completing three tests of the pipeline safety valve, reduce the fuel and stabilize the main steam pressure at 22.5MPa. Then, open the third bypass electric valve of the second inlet electric gate valve of the test circuit, close all the drain valves on the test circuit, close the second inlet electric gate valve of the test circuit, and finally close the third bypass electric valve of the second inlet electric gate valve of the test circuit to conduct a sealing test. After the sealing test is completed, open all the drain valves of the test circuit to complete the pipeline safety valve test.

2. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 1, characterized in that: It also includes the following steps: S10, after completing the pipeline safety valve test, conduct a hot test of the power relief valve at the superheater outlet on one side within a preset time period, keep the pipeline safety valve in the closed state, then open the third bypass electric valve of the second inlet electric gate valve of the test circuit, then open the second inlet electric gate valve of the test circuit, and finally close the third bypass electric valve of the second inlet electric gate valve of the test circuit to resume the test. Repeat S4-S7 three times according to the preset interval. S11. After completing the hot test of the power relief valve, repeat step S9 to conduct the sealing test.

3. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 2, characterized in that: In step S10, the preset time is 20-30 minutes. When the power relief valve hot test is performed after the preset time has been exceeded, step S2 is repeated to warm up the pipe.

4. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 3, characterized in that: In step S2, the debugging control includes the following sub-steps: S2.1, open the manual valves of the two local pressure gauges and two pipeline pressure transmitters in the test circuit, open the electric drain valve and the manual drain valve in front of the electric gate valve of the steam inlet in the test circuit, and after the test pipeline of the test circuit has been fully warmed up for a set time, open the manual drain valve and the electric drain valve of the pipeline. S2.2, remotely open the third bypass electric valve of the second steam inlet electric gate valve, and locally open the first bypass electric valve and the second bypass electric valve of the first steam inlet electric gate valve according to the test pipeline pressure, temperature rise and vibration conditions of the test circuit within a preset frequency range, and control the temperature and pressure of the test pipeline to gradually rise through the first bypass electric valve and the second bypass electric valve. S2.3 After the pipe has been sufficiently drained and warmed up, open the first and second inlet steam electric gate valves locally according to the preset frequency range to allow the pressure in the test pipeline to gradually increase, and open the pipeline PCV valve to purge the test circuit for the set duration.

5. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 4, characterized in that: In S2.3, the setting duration is greater than or equal to 30 seconds.

6. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 5, characterized in that: The preset interval is 20-30 minutes.

7. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 5, characterized in that: In step S6, when the main steam pressure increases to 25 MPa and the pipeline safety valve does not activate, the main steam pressure continues to increase and is kept less than or equal to 25.5 MPa. If the pipeline safety valve still does not activate, the test is stopped and the main steam pressure is reduced to 23.5 MPa.

8. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 5, characterized in that: While closing the first and second inlet electric gate valves, keep them de-energized. When closing the manual and electric drain valves, keep the pressure in the test circuit from rising. After closing the manual and electric drain valves, keep them de-energized.

9. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 5, characterized in that: During the warm-up process, determine whether the test pipeline is vibrating. If the test pipeline is vibrating, close the bypass regulating valve of the first inlet steam electric gate valve.

10. The method for online verification of a safety valve in an ultra-supercritical boiler according to claim 5, characterized in that: The condition for judging whether the pipe has been fully warmed up is: after the pipe has been warmed up, the temperature of the drain pipe in the test circuit is not less than 400℃.

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