Fault detection and solution method for main steam safety valve

Abstract

The invention relates to a main steam safety valve fault detection and solution method. The main steam safety valve is provided with a non-contact magnetic limit switch, a target magnet of the magnetic limit switch is fixed on a free end base of a safety valve spring, a probe of the magnetic limit switch is arranged on a safety valve cover, and the method comprises the following steps: S1, acquiring an output voltage value of the magnetic limit switch through a measuring element. And S2, judging whether the output voltage value exceeds a preset voltage value or not, if so, judging that the magnetic limit switch is closed abnormally, and executing the step S3. And S3, a gasket is arranged in the magnetic limit switch. The invention can effectively solve the fault that the main steam safety valve is not actually opened but not triggered to be closed for alarming.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power plants, and in particular to a main steam safety valve fault detection and solution method. Background Art

[0002] During normal operation of nuclear power, the main steam safety valve should remain closed. At present, the regular alarm function inspection of the main steam safety valve mainly involves manually simulating the gap between the target magnet and the probe, increasing it, and verifying whether the alarm (alarm of the main steam safety valve not closed) triggering range is normal, and manually simulating the gap between the target magnet and the probe, reducing it, and verifying whether the alarm reset value is normal.

[0003] However, during the normal operation of the unit, the main steam safety valve was repeatedly alarmed for not closing. The maintenance personnel verified on site that the main steam safety valve was not open, and the gap value between the measured target magnet and the probe did not reach the alarm trigger value. Obviously, the current regular alarm function inspection work can no longer meet the fault detection of the main steam safety valve. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a main steam safety valve fault detection and solution method for the above-mentioned defects.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a main steam safety valve fault detection and solution method, the main steam safety valve is provided with a non-contact magnetic limit switch, the target magnet of the magnetic limit switch is fixed on the free end base of the safety valve spring, the probe of the magnetic limit switch is arranged on the safety valve cover, and the method comprises the following steps:

[0006] S1. Obtaining the output voltage value of the magnetic limit switch by measuring the element;

[0007] S2, determining whether the output voltage value exceeds a preset voltage value, if so, determining that the closing resistance value of the magnetic limit switch is abnormal, and executing step S3;

[0008] S3, adding a gasket to the magnetic limit switch.

[0009] Further, in the main steam safety valve fault detection and solution method described in the present invention, step S1 includes:

[0010] The non-closing state alarm of the main steam safety valve is reset, and after the reset, the output voltage value of the magnetic limit switch is obtained through a measuring element.

[0011] Further, in the main steam safety valve fault detection and solution method described in the present invention, the preset voltage value is 0.02V.

[0012] Further, in the main steam safety valve fault detection and solution method described in the present invention, step S3 includes:

[0013] A gasket is arranged between the fixing nut of the magnetic limit switch and the probe fixing plate.

[0014] Further, in the main steam safety valve fault detection and solution method described in the present invention, the step of providing a gasket between the fixing nut of the magnetic limit switch and the probe fixing plate includes:

[0015] A gasket is respectively arranged on the upper part and the lower part of the probe fixing plate of the magnetic limit switch.

[0016] Furthermore, in the main steam safety valve fault detection and solution described in the present invention, the gasket is a polytetrafluoroethylene gasket, and the thickness of the gasket is 4 mm.

[0017] Further, in the main steam safety valve fault detection and solution method described in the present invention, the method also includes:

[0018] S4. Determine the closing state of the main steam safety valve according to the gap between the target magnet and the probe in the magnetic limit switch.

[0019] Further, in the main steam safety valve fault detection and solution method described in the present invention, step S4 includes:

[0020] Obtaining an actual gap value between the target magnet and the probe;

[0021] When the actual gap value is greater than the first gap range, it is determined that the main steam safety valve is in an open state, and a valve open alarm signal is triggered;

[0022] When the actual gap value is smaller than the second gap range, it is determined that the main steam safety valve is in a closed state, and a valve opening reminder signal is triggered or a valve not closed alarm signal is eliminated.

[0023] Further, in the main steam safety valve fault detection and solution method described in the present invention, the first gap range is 2.36-3.88 mm; the second gap range is 2.03-3.05 mm.

[0024] Further, in the main steam safety valve fault detection and solution method described in the present invention, step S2 includes:

[0025] It is determined whether the output voltage value exceeds the preset voltage value. If so, it is determined that the closing resistance of the magnetic limit switch is abnormal, and a reminder signal for adding a gasket to the magnetic limit switch is issued. Then, step S3 is executed.

[0026] The implementation of the main steam safety valve fault detection and solution method of the present invention has the following beneficial effects: the present invention determines whether there is a hidden problem of excessively large resistance in the limit switch by measuring the closed output voltage of the limit switch, and solves the problem of excessively large resistance by adding a gasket, thereby improving the shock absorption effect, and can effectively solve the fault of the main steam safety valve not actually opening but triggering an alarm for not closing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0028] Figure 1 It is a flow chart of main steam safety valve fault detection and solution according to one embodiment of the present invention;

[0029] Figure 2 It is a structural schematic diagram of a main steam safety valve provided by an embodiment of the present invention;

[0030] Figure 3 It is a flow chart of main steam safety valve fault detection and solution in some embodiments of the present invention;

[0031] Figure 4 yes Figure 2 A partial enlarged view of the magnetic limit switch;

[0032] Figure 5 is a circuit schematic diagram of a limit switch provided in some embodiments of the present invention;

[0033] Figure 6 It is a partial enlarged view of the gasket installation position of some embodiments of the present invention. DETAILED DESCRIPTION

[0034] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0035] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0036] In order to facilitate the understanding of the present invention, the present invention will be described more fully below, and the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0038] In a preferred embodiment, reference Figure 1 The main steam safety valve fault detection and solution method of this embodiment is applied to the main steam safety valve of a nuclear power plant.

[0039] The main steam safety valve is an overpressure protection device for the main steam system (VVP) of a pressurized water reactor nuclear power plant. When the system operating pressure rises to the opening pressure of the safety valve, the main steam safety valve automatically opens to discharge the steam in the main steam system to reduce the system pressure; when the system operating pressure drops to the return pressure of the safety valve, the main steam safety valve automatically closes and stops discharging, protecting the safety of the pipelines and equipment of the main steam system, while maintaining the stability of steam parameters and the safe operation of the unit. Its main functions are: to prevent overpressure and overheating on the primary circuit side by discharging the energy of the reactor cooling system; to prevent overcooling of the reactor core by limiting the amount of steam released to the atmosphere.

[0040] The main steam safety valve is a spring-loaded safety valve. It is a high-pressure, large-displacement safety valve designed for the saturated steam system of nuclear power plants. The main steam safety valve is divided into two groups. The set pressure of the first group is 8.5Mpa, and the set pressure of the second group is 8.7Mpa.

[0041] The main steam safety valve is a spring-loaded safety valve. It is a high-pressure, large-displacement safety valve designed for the saturated steam system of nuclear power plants. The main steam safety valve is divided into two groups. The set pressure of the first group is 8.5Mpa, and the set pressure of the second group is 8.7Mpa.

[0042] The main steam safety valve spring assembly is seated on the valve stem assembly through the lower spring seat, and the spring force is applied through the spring adjusting nut, which acts on the valve disc through the valve stem to seal the valve. When the valve set pressure is qualified, the position of the adjusting nut is fixed with a locking sleeve to prevent the valve setting value from drifting.

[0043] like Figure 2 As shown in the figure, it is a schematic diagram of the structure of the main steam safety valve. A non-contact magnetic limit switch is provided on the main steam safety valve to monitor the opening state of the main steam safety valve. The target magnet of the magnetic limit switch is fixed on the free end base of the safety valve spring, and the probe of the magnetic limit switch is set on the valve cover of the safety valve. Figure 1 The main steam safety valve fault detection and solution of this embodiment includes the following steps:

[0044] S1. Obtain the output voltage value of the magnetic limit switch through the measuring element.

[0045] S2, determine whether the output voltage value exceeds the preset voltage value, if so, determine that the closing resistance of the magnetic limit switch is abnormal, and execute step S3. As an option, the preset voltage value is 0.02V.

[0046] S3. Add gaskets to the magnetic limit switch.

[0047] This embodiment determines whether there is a hidden problem of excessively large resistance in the limit switch by measuring the closed output voltage of the limit switch, and solves the problem of excessively large resistance by adding a gasket, thereby improving the shock absorption effect, and can effectively solve the problem of the main steam safety valve not actually opening but triggering an alarm for not closing.

[0048] In some embodiments of the main steam safety valve fault detection and solution, in step S1, the main steam safety valve's unclosed state alarm is reset, and after the reset, the output voltage value of the magnetic limit switch is obtained by the measuring element. Then, S2, determine whether the output voltage value exceeds the preset voltage value. If so, determine that the closing resistance value of the magnetic limit switch is abnormal, and execute step S3. As an option, the preset voltage value is 0.02V. Of course, according to the specific valve requirements, the gap range can also be other numerical ranges. S3, add a gasket to the magnetic limit switch.

[0049] In this embodiment, the measuring element may be a multimeter to measure the amplitude of the output voltage of the limit switch, thereby making a fault judgment.

[0050] In some embodiments of the main steam safety valve fault detection and solution, S1, the main steam safety valve is reset to the open state alarm, and after the reset, the output voltage value of the magnetic limit switch is obtained by the measuring element. In step S2, it also includes: judging whether the output voltage value exceeds the preset voltage value, if so, determining that the closing resistance value of the magnetic limit switch is abnormal, and issuing a reminder signal for adding a gasket to the magnetic limit switch, and then executing step S3. S3, a gasket is set in the magnetic limit switch.

[0051] In some embodiments of the main steam safety valve fault detection and solution, S1, reset the main steam safety valve's unclosed state alarm, and after resetting, obtain the output voltage value of the magnetic limit switch through the measuring element. S2, determine whether the output voltage value exceeds the preset voltage value. If so, determine that the closing resistance of the magnetic limit switch is abnormal, specifically, the closing resistance of the magnetic limit switch is too large. Then, execute step S3. Specifically, in step S3, a gasket is set between the fixing nut of the magnetic limit switch and the probe fixing plate. Exemplarily, a gasket is installed on the upper and lower parts of the probe fixing plate of the magnetic limit switch. Alternatively, the gasket may be a polytetrafluoroethylene gasket, and the thickness of the gasket may be 4 mm.

[0052] That is to say, Figure 6 As shown, when it is determined that the closed output voltage value of the magnetic limit switch is greater than 0.02V, a 4mm thick polytetrafluoroethylene gasket can be added between the limit switch fixing nut and the probe fixing plate for shock absorption, and one gasket is added above and below the probe fixing plate, and the gasket is close to the probe fixing plate.

[0053] This embodiment determines whether there is a hidden problem of excessively large resistance in the limit switch by measuring the closed output voltage of the limit switch, and solves the problem of excessively large resistance by adding a gasket to improve the shock absorption effect, thereby effectively solving the problem of the main steam safety valve not actually opening but triggering an alarm for not closing.

[0054] In some embodiments of the main steam safety valve fault detection and solution, reference is made to Figure 3 The main steam safety valve fault detection and solution of this embodiment also includes:

[0055] S1. Obtain the output voltage value of the magnetic limit switch through the measuring element. S2. Determine whether the output voltage value exceeds the preset voltage value. If so, determine that the closing resistance value of the magnetic limit switch is abnormal, and execute step S3. S3. Add a gasket to the magnetic limit switch. S4. Determine the closing state of the main steam safety valve by the gap between the target magnet and the probe in the magnetic limit switch.

[0056] Specifically, step S4 includes:

[0057] Get the actual gap value between the target magnet and the probe.

[0058] When the actual gap value is greater than the first gap range, it is determined that the main steam safety valve is in an open state, and a valve open alarm signal is triggered.

[0059] When the actual gap value is less than the second gap range, it is determined that the main steam safety valve is in a closed state, and a valve opening reminder signal is triggered or a valve not closed alarm signal is eliminated.

[0060] For example, the first gap range may be 2.36-3.88 mm, and the second gap range may be 2.03-3.05 mm.

[0061] This embodiment monitors the opening state of the main steam safety valve through the gap between the target magnet and the probe in the magnetic limit switch, intuitively reflects the operating state of the main steam safety valve, and is conducive to timely solving fault problems.

[0062] Understandable, reference Figure 4 The working principle of the non-contact magnetic limit switch of the present invention is:

[0063] The non-contact magnetic limit switch consists of a target magnet and a probe. The target magnet is fixed to the free end base of the safety valve spring and can move up and down with the valve. The probe is installed on the safety valve cover. When the safety valve is in the closed state, the gap between the target magnet and the probe is small. The target magnet is close to the probe, the permanent magnet in the probe is attracted, and the internal contacts of the limit switch are in the closed state. When the safety valve is opened, the gap between the target magnet and the probe becomes larger. As the distance between the target magnet and the probe increases, the suction force weakens, and the internal contacts of the limit switch are in the disconnected state, sending a signal that the valve is not closed. Therefore, the internal contacts of the safety valve limit switch are normally closed contacts.

[0064] When the gap value between the target magnet and the probe is greater than 2.36-3.88mm, the alarm signal that the main steam safety valve is not closed will be triggered; when the gap value between the target magnet and the probe is less than 2.03-3.05mm, the alarm that the main steam safety valve is not closed will disappear.

[0065] The method is further described in detail below with the preset voltage value being 0.02V.

[0066] Through analysis, the reason why the main steam safety valve flashes and fails to close the alarm may be that the internal contacts of the limit switch may be unstable and too large due to high-temperature oxidation or vibration.

[0067] To solve the above problem, after the alarm of the main steam safety valve not being closed is reset, the output voltage of the magnetic limit switch of the main steam safety valve is measured, and the actual output voltage value is required to meet ≤0.02V.

[0068] If the above voltage requirements are not met, add gaskets to the limit switch.

[0069] If the output voltage of the limit switch meets the requirement of ≤0.02V, it means that the internal closed resistance of the limit switch is small and within the normal range, so it can remain stable during normal operation. If the output voltage of the limit switch is greater than 0.02V, it means that its internal closed resistance is too large. If the resistance is greater than a certain threshold, the acquisition card will think that its contacts are in the disconnected position, which will cause an abnormal alarm to be triggered during normal operation.

[0070] Combination Figure 5 , which is a circuit schematic diagram of a limit switch, explains the mechanism by which an increase in the resistance of the limit switch will cause an abnormal alarm to be triggered.

[0071] Under normal circumstances, the resistance value is small when the limit switch is closed. Figure 5The "1" end in the circuit is at a low level, the light-emitting diode is turned on, the photocoupler is turned on, and the output is at a low level. In an abnormal situation, when the limit switch is closed, the resistance is large. At this time, the "1" end is at a high level, the light-emitting diode is turned off, the photocoupler is turned off, and the output is at a high level.

[0072] In this embodiment, by connecting Figure 5 The closed output voltage of the magnetic limit switch is measured at the terminals An and Bn or any parallel circuit in the loop.

[0073] In this embodiment, the limit switches with unqualified output voltage are processed with gaskets, and after the processing, the problem of flashing alarm does not occur during daily operation.

[0074] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0075] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A main steam safety valve fault detection and solution method, characterized in that: The main steam safety valve is provided with a non-contact magnetic limit switch, the target magnet of the magnetic limit switch is fixed on the free end base of the safety valve spring, and the probe of the magnetic limit switch is arranged on the safety valve cover. The method comprises the following steps: S1. Obtaining the output voltage value of the magnetic limit switch by measuring the element; S2, determining whether the output voltage value exceeds a preset voltage value, if so, determining that the closing resistance value of the magnetic limit switch is abnormal, and executing step S3; S3. Adding a gasket to the magnetic limit switch.

2. The main steam safety valve fault detection and solution method according to claim 1 is characterized in that: Step S1 includes: The non-closing state alarm of the main steam safety valve is reset, and after the reset, the output voltage value of the magnetic limit switch is obtained through a measuring element.

3. The main steam safety valve fault detection and solution method according to claim 1 is characterized in that: The preset voltage value is 0.02V.

4. The main steam safety valve fault detection and solution method according to claim 1 is characterized in that: Step S3 includes: A gasket is arranged between the fixing nut of the magnetic limit switch and the probe fixing plate.

5. The main steam safety valve fault detection and solution method according to claim 4 is characterized in that: The step of providing a gasket between the fixing nut of the magnetic limit switch and the probe fixing plate includes: A gasket is respectively arranged on the upper part and the lower part of the probe fixing plate of the magnetic limit switch.

6. The main steam safety valve fault detection and solution method according to any one of claims 1, 4 or 5, characterized in that: The gasket is a polytetrafluoroethylene gasket, and the thickness of the gasket is 4 mm.

7. The main steam safety valve fault detection and solution method according to claim 1 is characterized in that: The method further comprises: S4. Determine the closing state of the main steam safety valve according to the gap between the target magnet and the probe in the magnetic limit switch.

8. The main steam safety valve fault detection and solution method according to claim 7 is characterized in that: Step S4 includes: Obtaining an actual gap value between the target magnet and the probe; When the actual gap value is greater than the first gap range, it is determined that the main steam safety valve is in an open state, and a valve open alarm signal is triggered; When the actual gap value is smaller than the second gap range, it is determined that the main steam safety valve is in a closed state, and a valve opening reminder signal is triggered or a valve not closed alarm signal is eliminated.

9. The main steam safety valve fault detection and solution method according to claim 8, characterized in that: The first gap ranges from 2.36 to 3.88 mm; the second gap ranges from 2.03 to 3.05 mm.

10. The main steam safety valve fault detection and solution method according to claim 1, characterized in that: Step S2 includes: It is determined whether the output voltage value exceeds the preset voltage value. If so, it is determined that the closing resistance of the magnetic limit switch is abnormal, and a reminder signal for adding a gasket to the magnetic limit switch is issued. Then, step S3 is executed.

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