A method for online flushing of a main steam isolation valve oil circuit

Abstract

The present application relates to the field of nuclear power plant maintenance, and more particularly to a main steam isolation valve oil line online flushing method. The main steam isolation valve oil line online flushing method comprises the following steps: step one, slow closing flushing; step two, fast closing flushing; step three, solenoid control loop flushing; step four, foreign matter inspection; step five, flushing and then pumping and injecting; step six, foreign matter confirmation; and step seven, test verification. The present application can efficiently remove foreign matter in the oil line without replacing or disassembling the main steam isolation valve actuator, thereby ensuring the operation reliability of the main steam isolation valve.

Description

Technical Field

[0001] This invention relates to the field of nuclear power equipment maintenance, and in particular to an online flushing method for the oil circuit of a main steam isolation valve. Background Technology

[0002] The main steam isolation valve is one of the key and sensitive pieces of equipment in a nuclear power plant, playing a vital role in quickly shutting it off during accident conditions and keeping it open to transmit main steam during normal operation.

[0003] The main steam isolation valves of Units 1-4 at the Fuqing Nuclear Power Plant consist of two parts: the valve itself and the actuator. The actuator is a pneumatic-hydraulic linkage structure, using a pneumatic oil pump to provide hydraulic power to open the valve. The spherical chamber at the top of the actuator is filled with high-pressure nitrogen, providing the power needed for the main steam isolation valve to close quickly. The pressure relief circuit is designed with two redundant lines: one on the pump side and one on the non-pump side.

[0004] The main components of the main steam isolation valve actuator include: air supply valve 1, compressed air filter 2, compressed air solenoid valve 3, compressed air pressure reducing valve 4, compressed air safety valve 5, pressure gauge 6, pneumatic oil pump 7, pump inlet filter 8, pump outlet filter 9, oil tank 10, return oil diffuser 11, oil sight glass 12, oil circuit safety valve 13, accumulator 14, oil pressure gauge 15, main oil circuit isolation valve 16, pump-side pressure relief circuit, non-pump-side pressure relief circuit, cylinder-ball head assembly 29, piston assembly 30, nitrogen pressure monitoring device 31, and related pipelines. The components of the pump-side or non-pump-side pressure relief circuit include: return oil isolation valve 17 / 18, main pressure relief valve 19 / 20, speed control valve 21 / 22, test switching valve 23 / 24, main solenoid valve 25 / 26, test solenoid valve 27 / 28, and related pipelines.

[0005] The working principle of the actuator of the main steam isolation valve is as follows: Before the main steam isolation valve is opened, the main solenoid valves 25 / 26 and the test solenoid valves 27 / 28 are de-energized, which closes the main pressure relief valve 19 / 20 and keeps the test switching valve 23 / 24 in the quick-close position, while the balloon valve 1 is normally open. After the compressed air solenoid valve 3 is energized, the compressed air drives the pneumatic oil pump 7 to work, which increases the hydraulic oil pressure. After flowing through the oil pressure gauge 15, the accumulator 14 and the main oil circuit isolation valve 16, the oil cylinder-ball head assembly 29 pushes the piston assembly 30 to move upward, thereby driving the main steam isolation valve to open. When the main steam isolation valve closes rapidly, the main solenoid valve 25 / 26 is energized, the main pressure relief valve 19 / 20 opens, the pressure relief channel is opened, and the main steam isolation valve closes rapidly. When the main steam isolation valve closes slowly, the test solenoid valve 27 / 28 is energized, the test switching valve 23 / 24 switches to the slow closing position, then the main solenoid valve 25 / 26 is energized, the main pressure relief valve 19 / 20 opens, the pressure relief channel is opened, and the main steam isolation valve closes slowly.

[0006] The connection relationships of the above components are as follows: the air supply valve 1 and the compressed air filter 2 are connected by threads; the outlet of the compressed air filter 2 and the inlet of the compressed air solenoid valve 3 are connected by threads; the outlet of the compressed air solenoid valve 3 and the inlet of the compressed air pressure reducing valve 4 are connected by threads; and the outlet of the compressed air pressure reducing valve 4 is connected to the inlet of the compressed air circuit of the compressed air safety valve 5, the air pressure gauge 6, and the pneumatic oil pump 7 through a cross-threaded connector.

[0007] The pneumatic oil pump 7 is fixed to the oil tank 10 by flange bolts. Both its inlet and outlet are immersed in the oil tank. The suction port of the pneumatic oil pump 7 is connected to the pump inlet filter 8 via a threaded short pipe, and the outlet port is connected to the pump outlet filter 9 via a threaded short pipe. The outlet of the pump outlet filter 9 is connected to the pump-side pressure relief circuit and the oil cylinder 29 via an oil inlet pipe (on which the accumulator 14, oil pressure gauge 15, and main oil circuit isolation valve 16 are installed in sequence). The other side of the oil cylinder 29 is bolted to the non-pump-side pressure relief circuit.

[0008] The pump-side and non-pump-side pressure relief circuits have the same structural principle; the connection relationship is explained using the pump-side as an example. The pump-side pressure relief circuit is in the form of a block, with its inlet being the return oil isolation valve 17, which is connected to the outlet of the main oil circuit isolation valve 16 and fixed to the oil cylinder 29 by bolts. The outlet of the return oil isolation valve 17 has a cross structure, with one side connected to the main pressure relief valve 19 through the internal flow channel of the block, and the other side connected to the main solenoid valve 25 and the test solenoid valve 27 through the internal flow channel of the block. The remaining side is connected to the control component of the main pressure relief valve 19 through the internal flow channel of the block. The outlet of the main pressure relief valve 19 is connected to the speed control valve 21 through the internal flow channel of the block, and the outlet of the speed control valve 21 is connected to the test switching valve 23 through the internal flow channel of the block. The outlet of the test switching valve 23 is connected to the return oil diffuser 11 back to the oil tank 10 through an oil pipe. The main solenoid valve 25 controls the opening and closing state of the main pressure relief valve 19, and the test solenoid valve 27 controls the opening and closing state of the test switching valve 23.

[0009] According to technical specifications, the main steam isolation valve should undergo partial closure tests periodically to verify the availability of the pressure relief module and the valve body. During the partial closure test of the main steam isolation valve at Fuqing Nuclear Power Plant, the misfire valve failed to switch states twice, resulting in test failure. Disassembly revealed foreign objects inside the test solenoid valve.

[0010] Hydraulic oil is the core medium driving the opening of the main steam isolation valve, and its cleanliness is crucial to the valve's critical function. Traditionally, to remove foreign matter from the main steam isolation valve's oil circuit, the entire actuator of the main steam isolation valve needs to be replaced or completely disassembled for inspection. To create conditions for maintenance, the nuclear power unit needs to be withdrawn to the normal shutdown / residual heat removal and cooling (NS / RRA) mode. However, withdrawing the unit to a deeper mode brings problems such as complex operation, system equipment start-up and shutdown, and the need to re-perform some periodic tests, posing serious challenges to the maintenance schedule and safety and quality. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide an online flushing method for the oil circuit of a main steam isolation valve, which can efficiently remove foreign objects in the oil circuit without replacing or disassembling the actuator of the main steam isolation valve, thereby ensuring the operational reliability of the main steam isolation valve.

[0012] This invention provides a method for online flushing of the main steam isolation valve oil circuit, comprising the following steps:

[0013] Step 1: Rinse slowly;

[0014] Step 2: Quickly turn off the rinse;

[0015] Step 3: Flushing the solenoid valve control circuit;

[0016] Step 4: Foreign object inspection;

[0017] Step 5: Aspirate after rinsing;

[0018] Step Six: Foreign Object Confirmation;

[0019] Step 7: Experimental verification.

[0020] Preferably, step one specifically comprises:

[0021] Step 1-1: Provided that there is no first set of operating events in the unit, open all main steam isolation valves simultaneously;

[0022] Steps 1-2: Slowly close the main steam isolation valve that needs to be flushed, i.e., the test solenoid valve is energized, the test switching valve is switched to the slow-close position, then the main solenoid valve is energized, the main pressure relief valve is opened, and the flushing oil circuit is slowly closed.

[0023] Preferably, step one is repeated at least twice.

[0024] Preferably, step two specifically comprises:

[0025] Step 2-1: Provided that there are no first set of operating events in the unit, open all the main steam isolation valves of the unit simultaneously;

[0026] Step 2-2: Perform a quick-closing operation on the pump-side pressure relief circuit that needs to be flushed for the main steam isolation valve, i.e., the main solenoid valve is energized, the main pressure relief valve is opened, and the oil circuit is flushed.

[0027] Step 2-3: Repeat steps 2-1 and 2-2 at least twice, and record the closing time;

[0028] Steps 2-4: Open all main steam isolation valves simultaneously;

[0029] Steps 2-5: Perform a quick-closing operation on the non-pump side pressure relief circuit that needs to be flushed for the main steam isolation valve, i.e., the main solenoid valve is energized, the main pressure relief valve is opened, and the flushing oil circuit is quickly closed.

[0030] Steps 2-6: Repeat steps 2-4 and 2-5 at least twice and record the closing time.

[0031] Preferably, step three specifically comprises:

[0032] Close the main steam isolation valve;

[0033] Close the balloon supply valve to about 1 / 3 of its opening;

[0034] Remove the solenoid valve;

[0035] The oil circuit between the main solenoid valve and the main pressure relief valve, and the oil circuit between the test solenoid valve and the test switching valve were squeezed and checked to confirm that there were no foreign objects.

[0036] Install a three-way solenoid valve simulator at the positions of the main solenoid valve and the test solenoid valve;

[0037] When the compressed air solenoid valve is energized, flush the two pressure relief circuits of the main steam isolation valve for 10 to 120 minutes.

[0038] Remove the solenoid valve simulator, assemble the main solenoid valve and test solenoid valve, and restore them to the main steam isolation valve actuator.

[0039] Preferably, step four specifically comprises:

[0040] Drain the hydraulic oil from the oil tank and check for foreign objects in the hydraulic oil;

[0041] Remove the fuel tank and check it for foreign objects.

[0042] Check the integrity of the pump inlet filter, outlet filter, and return diffuser assembly;

[0043] Remove the pump inlet filter, outlet filter, and return oil diffuser, and check for foreign objects;

[0044] Clean any foreign objects from the components inside the fuel tank;

[0045] Reinstall all components inside the fuel tank.

[0046] Preferably, step five specifically comprises:

[0047] Add qualified new oil to the upper oil viewing window 12, filling it to 50% to 100%.

[0048] Preferably, step six specifically comprises:

[0049] If there are foreign objects in the return oil diffuser, repeat steps one through five.

[0050] If there are no foreign objects in the return diffuser, replace the solenoid valve and proceed to step seven.

[0051] Preferably, step seven specifically comprises:

[0052] Under the premise that there is no first group of operating events in the unit, perform a quick-closing test on each of the two pressure relief circuits of the main steam isolation valve once;

[0053] Perform a partial shutdown test on each of the two pressure relief circuits of the main steam isolation valve once.

[0054] Compared with the prior art, the online flushing method for the main steam isolation valve oil circuit of the present invention has the following advantages:

[0055] (1) Nuclear power units do not need to retreat to normal shutdown mode (NS / RRA) to avoid a large number of operation operations, system equipment start-up and shutdown and periodic test re-execution, saving at least 5 days of construction time, indirectly generating economic benefits of RMB48 million, and also avoiding unpredictable safety and quality risks.

[0056] (2) There is no need to disassemble the main steam isolation valve actuator or replace the entire main steam isolation valve actuator, thus avoiding spare parts costs of nearly one million yuan. Attached Figure Description

[0057] Figure 1 This diagram illustrates the structural principle of the main steam isolation valve.

[0058] Figure 2 This diagram illustrates the slow-closing flushing oil circuit.

[0059] Figure 3 A schematic diagram showing the quick-closing flushing oil circuit;

[0060] Figure 4 This diagram illustrates the oil circuit flushing controlled by a solenoid valve.

[0061] In the diagram: 1. Air supply valve; 2. Compressed air filter; 3. Compressed air solenoid valve; 4. Compressed air pressure reducing valve; 5. Compressed air safety valve; 6. Pressure gauge; 7. Pneumatic oil pump; 8. Pump inlet filter; 9. Pump outlet filter; 10. Oil tank; 11. Oil return diffuser; 12. Oil sight glass; 13. Oil circuit safety valve; 14. Accumulator; 15. Oil pressure gauge; 16. Main oil circuit isolation valve; 17 / 18. Oil return isolation valve; 19 / 20. Main pressure relief valve; 21 / 22. Speed ​​control valve; 23 / 24. Test switching valve; 25 / 26. Main solenoid valve; 27 / 28. Test solenoid valve; 29. ​​Cylinder-ball head assembly; 30. Piston assembly; 31. Nitrogen pressurization monitoring device. Detailed Implementation

[0062] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0063] An embodiment of the present invention discloses an online flushing method for the oil circuit of a main steam isolation valve, comprising the following steps:

[0064] 1. Slowly turn off the rinse, such as Figure 2 As shown, Figure 2 The thick lines in the text represent the rinsing path.

[0065] Provided there are no first-stage operational events in the unit, the operators open all main steam isolation valves simultaneously.

[0066] When the main steam isolation valve required for slow closing is flushed, i.e., the test solenoid valve 27 / 28 is energized, the test switching valve 23 / 24 is switched to the slow closing position, then the main solenoid valve 19 / 20 is energized, and the main pressure relief valve 19 / 20 is opened, thus realizing the slow closing flushing oil circuit.

[0067] Repeat the above steps at least twice.

[0068] 2. Quickly turn off the rinse, such as Figure 3 As shown, Figure 3 The thick lines in the text represent the rinsing path.

[0069] Provided that there is no first set of operating events in the unit, the operators will open all the main steam isolation valves of the unit simultaneously.

[0070] Perform a quick-closing operation on the pump-side pressure relief circuit that needs to be flushed for the main steam isolation valve, i.e., energize the main solenoid valve 25, open the main pressure relief valve 19, and flush the oil circuit.

[0071] Repeat the above steps at least twice and record the closing time.

[0072] Open all main steam isolation valves simultaneously.

[0073] A quick-closing operation is performed on the non-pump side pressure relief circuit that needs to be flushed for the main steam isolation valve. That is, the main solenoid valve 26 is energized and the main pressure relief valve 20 is opened to achieve quick closure of the flushing oil circuit.

[0074] Repeat the above steps at least twice and record the closing time.

[0075] 3. Flushing of the solenoid valve control circuit, such as... Figure 4 As shown, Figure 4 The thick lines in the text represent the rinsing path.

[0076] Close the main steam isolation valve.

[0077] Close the balloon valve 1 to about 1 / 3 of its opening.

[0078] Remove solenoid valves 25 / 26 / 27 / 28.

[0079] Use a vacuum cleaner to vacuum and check the oil circuit between the main solenoid valve 25 / 26 and the main pressure relief valve 19 / 20, and the oil circuit between the test solenoid valve 27 / 28 and the test switching valve 23 / 24 to confirm that there are no foreign objects.

[0080] Install solenoid valve three-way simulators at positions 25 / 26 of the main solenoid valve and 27 / 28 of the test solenoid valve (simply remove the valve cores of solenoid valves 25 / 26 / 27 / 28).

[0081] When the compressed air solenoid valve 3 is energized, it flushes the two pressure relief circuits of the main steam isolation valve for 10 minutes.

[0082] Remove the solenoid valve simulator, assemble the main solenoid valves 25 / 26 and the test solenoid valves 27 / 28, and restore them to the main steam isolation valve actuator.

[0083] 4. Foreign body inspection

[0084] Drain the hydraulic oil from oil tank 10 and check for foreign objects in the hydraulic oil.

[0085] Remove fuel tank 10 and check if there are any foreign objects inside.

[0086] Check the integrity of the pump inlet filter 8, outlet filter 9, and return oil diffuser 11 assembly, and replace the filter spare parts and return oil diffuser spare parts if necessary.

[0087] Remove the pump inlet filter 8, outlet filter 9 and return oil diffuser 11 and check for foreign objects (the inlet filter 8 and outlet filter 9 are removed and checked after the first flush and do not need to be opened again).

[0088] Clean any foreign objects from components 8 / 9 / 10 / 11 inside the fuel tank.

[0089] Reinstall all components 8 / 9 / 11 inside the fuel tank.

[0090] 5. Rinse and then add oil.

[0091] Add qualified new oil to the upper oil viewing window 12 at 50-100%.

[0092] 6. Foreign object confirmation

[0093] If there are foreign objects in the return oil diffuser 11, repeat steps 1-5.

[0094] If there are no foreign objects in the return oil diffuser 11, replace the solenoid valves 25 / 26 / 27 / 28 and proceed to Section 7.

[0095] 7. Experimental verification

[0096] Provided that there is no first set of operating events in the unit, perform a quick-closing test on each of the two pressure relief circuits of the main steam isolation valve once.

[0097] Perform a partial shutdown test on each of the two pressure relief circuits of the main steam isolation valve once.

[0098] To avoid the situation where a single main steam isolation valve is open, if the pressure difference between the two steam generators is greater than 0.7 MPa (two high and one low pressure in the main steam pipeline), the unit is at risk of injection.

[0099] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0100] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for online flushing of the oil circuit of a main steam isolation valve, characterized in that, Includes the following steps: Step 1: Rinse slowly; Specifically: Step 1-1: Provided that there is no first set of operating events in the unit, open all main steam isolation valves simultaneously; Steps 1-2: Slowly close the main steam isolation valve that needs to be flushed, i.e., the test solenoid valve is energized, the test switching valve is switched to the slow-close position, then the main solenoid valve is energized, the main pressure relief valve is opened, and the flushing oil circuit is slowly closed. Step 2: Quickly turn off the rinse; Specifically: Step 2-1: Provided that there are no first set of operating events in the unit, open all the main steam isolation valves of the unit simultaneously; Step 2-2: Perform a quick-closing operation on the pump-side pressure relief circuit that needs to be flushed for the main steam isolation valve, i.e., the main solenoid valve is energized, the main pressure relief valve is opened, and the oil circuit is flushed. Step 2-3: Repeat steps 2-1 and 2-2 at least twice, and record the closing time; Steps 2-4: Open all main steam isolation valves simultaneously; Steps 2-5: Perform a quick-closing operation on the non-pump side pressure relief circuit that needs to be flushed for the main steam isolation valve, i.e., the main solenoid valve is energized, the main pressure relief valve is opened, and the flushing oil circuit is quickly closed. Steps 2-6: Repeat steps 2-4 and 2-5 at least twice, and record the closing time. Step 3: Flushing the solenoid valve control circuit; Specifically: Close the main steam isolation valve; Close the balloon supply valve to about 1 / 3 of its opening; Remove the solenoid valve; The oil circuit between the main solenoid valve and the main pressure relief valve, and the oil circuit between the test solenoid valve and the test switching valve were squeezed and checked to confirm that there were no foreign objects. Install a three-way solenoid valve simulator at the positions of the main solenoid valve and the test solenoid valve; When the compressed air solenoid valve is energized, flush the two pressure relief circuits of the main steam isolation valve for 10 to 120 minutes. Disassemble the solenoid valve simulator, assemble the main solenoid valve and test solenoid valve, and restore them to the main steam isolation valve actuator; Step 4: Foreign object inspection; Step 5: Aspirate after rinsing; Step Six: Foreign Object Confirmation; Step 7: Experimental verification.

2. The online flushing method for the main steam isolation valve oil circuit according to claim 1, characterized in that, Step one is repeated at least twice.

3. The online flushing method for the main steam isolation valve oil circuit according to claim 1, characterized in that, Step four specifically involves: Drain the hydraulic oil from the oil tank and check for foreign objects in the hydraulic oil; Remove the fuel tank and check it for foreign objects. Check the integrity of the pump inlet filter, outlet filter, and return diffuser assembly; Remove the pump inlet filter, outlet filter, and return oil diffuser, and check for foreign objects; Clean any foreign objects from the components inside the fuel tank; Reinstall all components inside the fuel tank.

4. The online flushing method for the main steam isolation valve oil circuit according to claim 1, characterized in that, Step five specifically involves: Add qualified new oil to 50% to 100% of the upper oil viewing window.

5. The online flushing method for the main steam isolation valve oil circuit according to claim 1, characterized in that, Step six specifically involves: If there are foreign objects in the return oil diffuser, repeat steps one through five. If there are no foreign objects in the return diffuser, replace the solenoid valve and proceed to step seven.

6. The online flushing method for the main steam isolation valve oil circuit according to claim 1, characterized in that, Step seven specifically involves: Under the premise that there is no first group of operating events in the unit, perform a quick-closing test on each of the two pressure relief circuits of the main steam isolation valve once; Perform a partial shutdown test on each of the two pressure relief circuits of the main steam isolation valve once.

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