A main steam isolation valve load test system and method

Abstract

The application relates to a main steam isolation valve load test system, which comprises a first plug-in valve, a second plug-in valve, a first electromagnetic valve, a second electromagnetic valve, a regulating valve, an extension rod, a first isolation valve, a first oil pressure switch, a second isolation valve, a second oil pressure switch, a third isolation valve, a third oil pressure switch, a throttling element and a fourth isolation valve. The application also relates to a main steam isolation valve load test method. The application can prevent the main steam isolation valve from being abnormally closed during the load test, prevent the residual pressure between the plug-in valves from causing high-pressure alarm, and release the residual pressure between the plug-in valves after the load test.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power plant equipment, in particular to a main steam isolation valve load test system and method. BACKGROUND

[0002] The main steam isolation valve is one of the most critical safety class valves in the nuclear power plant, which is required to be kept open in daily operation and to be closed quickly to ensure the main steam isolation function and avoid the reactor core overcooling in accident conditions. The main steam isolation valve load test system of the No. 5 and No. 6 units of Fuqing nuclear power plant is divided into two redundant A and B columns. The main steam isolation valve load test needs to be performed every month to verify the availability of the quick closing loop of the main steam isolation valve. If the test fails, the unit needs to be withdrawn within the specified time limit, which has a significant impact on the operation of the nuclear power plant.

[0003] Reference Figure 1, the A column main steam isolation valve with load test system, the A column main steam isolation valve with load test system includes first cartridge valve DV1, second cartridge valve DV2, first solenoid valve SV1, second solenivia valve SV2, regulating valve FCA, telescopic rod IA, first isolation valve NNSV1, first oil pressure switch PSSV1, second isolation valve NNSV2, second oil pressure switch PSSV2, third isolation valve NVA, third oil pressure switch PSA, overpressure valve OVA and fourth isolation valve NVY;First cartridge valve DV1 is controlled by first solenoid valve SV1 Switch state, second cartridge valve DV2 is controlled by second solenoid valve SV2 Switch state;The inlet of first cartridge valve DV1 is connected with the oil cylinder pipeline of main steam isolation valve, and the outlet of first cartridge valve DV1 is connected with the inlet pipeline of second cartridge valve DV2;The piston side of first cartridge valve DV1 is connected with the inlet pipeline of first solenoid valve SV1 and first isolation valve NNSV1 respectively;The outlet of first isolation valve NNSV1 is connected with first oil pressure switch PSSV1 pipeline;The piston side of second cartridge valve DV2 is connected with the inlet pipeline of second solenoid valve SV2 and second isolation valve NNSV2 respectively;The outlet of second isolation valve NNSV2 is connected with second oil pressure switch PSSV2 pipeline;The outlet of second cartridge valve DV2 is connected with regulating valve FCA pipeline;The outlet of first cartridge valve DV1 is connected with the inlet of second cartridge valve DV2 respectively pipeline connection telescopic rod IA and the inlet of third isolation valve NVA;The outlet of third isolation valve NVA is connected with third oil pressure switch PSA and overpressure valve OVA pipeline respectively;Overpressure valve OVA is connected with fourth isolation valve NVY pipeline;The inlet of first isolation valve NNSV1 is connected with first solenoid valve SV1 pipeline, and the inlet of first isolation valve NNSV1 is provided with first pressure gauge interface TPSV1 on the pipeline connected with first solenoid valve SV1;The inlet of second isolation valve NNSV2 is connected with second solenoid valve SV2 pipeline, and the inlet of second isolation valve NNSV2 is provided with second pressure gauge interface TPSV2 on the pipeline connected with second solenoid valve SV2;The inlet of third isolation valve NVA is connected with telescopic rod IA pipeline, and the inlet of third isolation valve NVA is provided with third pressure gauge interface TPA on the pipeline connected with telescopic rod IA. First cartridge valve DV1 and second cartridge valve DV2 are connected in series and closed normally, first solenoid valve SV1 and second solenoid valve SV2 are closed normally, overpressure valve OVA is opened at low pressure and closed at high pressure, and fourth isolation valve NVY is normally open.

[0004] The main steam isolation valve load test is to open and close the plug-in valve one by one through the electromagnetic valve control, and the availability of the main steam isolation valve opening and closing loop is judged by the change of the pressure switch alarm signal and the action of the telescopic rod. Taking the A column main steam isolation valve load test system as an example, the main steam isolation valve load test logic is: under the condition that the third oil pressure switch PSA has no high pressure alarm, the first electromagnetic valve SV1 is powered on to open, the first oil pressure switch PSSV1 low pressure alarm appears, the first plug-in valve DV1 is opened, the third oil pressure switch PSA high pressure alarm appears, the telescopic rod IA is extended, the first electromagnetic valve SV1 is powered off to close, the first oil pressure switch PSSV1 low pressure alarm disappears, the first plug-in valve DV1 is closed, and the telescopic rod IA is extended and the third oil pressure switch PSA high pressure alarm is kept for 30s, the second electromagnetic valve SV2 is powered on to open, the second oil pressure switch PSSV2 low pressure alarm appears, the second plug-in valve DV2 is opened, the third oil pressure switch PSA high pressure alarm disappears, the telescopic rod IA is retracted, the second electromagnetic valve SV2 is powered off to close, and the second oil pressure switch PSSV2 low pressure alarm disappears, and the second plug-in valve DV2 is closed.

[0005] The existing main steam isolation valve load test system has low reliability, and the main steam isolation valve load test has failed many times. Taking the A column main steam isolation valve load test system as an example, the main problems are as follows:

[0006] 1. During the 30s interval between the closing of the first plug-in valve DV1 and the opening of the second plug-in valve DV2, the telescopic rod IA is retracted in advance, and the third oil pressure switch PSA high pressure alarm disappears. At this time, it cannot be proved that the subsequent second plug-in valve DV2 has normal opening and closing action, that is, the availability of the main steam isolation valve quick closing loop cannot be proved, the main steam isolation valve load test cannot be proved to be qualified, and the confidence of the main steam isolation valve load test is low.

[0007] 2. When the second plug-in valve DV2 is opened, the main steam isolation valve occasionally appears real quick closing, and the valve has the risk of accidental closing leading to unplanned shutdown.

[0008] 3. After the second plug-in valve DV2 is closed, the third oil pressure switch PSA high pressure alarm reappears, which restricts the development of the next main steam isolation valve load test. If the main steam isolation valve load test is performed again under the condition that the first plug-in valve DV1 has internal leakage to eliminate the high action of the third oil pressure switch PSA high pressure alarm, there is a risk of accidental closing of the main steam isolation valve. SUMMARY

[0009] The present application aims to provide a main steam isolation valve load test system and method, solve the problems that the existing main steam isolation valve load test system is prone to early disappearance of high pressure alarm of the third oil pressure switch during the main steam isolation valve load test, leading to inability to prove the real fast closing of the main steam isolation valve and the reappearance of high pressure alarm of the third oil pressure switch after the second plug-in valve is closed, and realize that the main steam isolation valve does not abnormally fast close during the main steam isolation valve load test, the residual pressure between the plug-in valves does not cause high pressure alarm, and the residual pressure between the plug-in valves can be released after the main steam isolation valve load test is completed.

[0010] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0011] A main steam isolation valve load test system for verifying the availability of the fast closing loop of the main steam isolation valve during the main steam isolation valve load test, comprising: a first plug-in valve, a second plug-in valve, a first electromagnetic valve, a second electromagnetic valve, a regulating valve, a telescopic rod, a first isolation valve, a first oil pressure switch, a second isolation valve, a second oil pressure switch, a third isolation valve, a third oil pressure switch, a throttling element and a fourth isolation valve.

[0012] The first plug-in valve controls the switching state through the first electromagnetic valve, and the second plug-in valve controls the switching state through the second electromagnetic valve; the inlet of the first plug-in valve is connected with the oil cylinder pipeline of the main steam isolation valve, and the outlet of the first plug-in valve is connected with the inlet pipeline of the second plug-in valve.

[0013] The piston side of the first plug-in valve is connected with the inlet pipeline of the first electromagnetic valve and the first isolation valve respectively; the outlet of the first isolation valve is connected with the first oil pressure switch pipeline; the piston side of the second plug-in valve is connected with the inlet pipeline of the second electromagnetic valve and the second isolation valve respectively; the outlet of the second isolation valve is connected with the second oil pressure switch pipeline.

[0014] The outlet of the second plug-in valve is connected with the regulating valve pipeline; the pipeline connecting the outlet of the first plug-in valve with the inlet of the second plug-in valve is respectively connected with the inlet of the third isolation valve and the telescopic rod pipeline; the outlet of the third isolation valve is respectively connected with the third oil pressure switch and the throttling element pipeline; the throttling element is connected with the fourth isolation valve pipeline.

[0015] The inlet of the first isolation valve is connected with the inlet pipeline of the first electromagnetic valve, and a first pressure gauge interface is arranged on the pipeline connecting the inlet of the first isolation valve with the first electromagnetic valve.

[0016] The inlet of the second isolation valve is connected with the inlet pipeline of the second electromagnetic valve, and a second pressure gauge interface is arranged on the pipeline connecting the inlet of the second isolation valve with the second electromagnetic valve.

[0017] The inlet of the third isolation valve is connected with the telescopic rod pipeline, and a third pressure gauge interface is arranged on the pipeline connecting the inlet of the third isolation valve with the telescopic rod.

[0018] As one of the ways that can be realized, the throttling element is a pipeline connecting piece with throttling function.

[0019] As one of the ways that can be realized, the fourth isolation valve is normally closed to realize the double-way isolation of the daily oil circuit.

[0020] The application also provides a main steam isolation valve load test method using the main steam isolation valve load test system, comprising the following steps:

[0021] Step 1, under the condition that the third oil pressure switch has no high pressure alarm, the first electromagnetic valve is powered on, then the first oil pressure switch has low pressure alarm, and then the first cartridge valve is opened;

[0022] Step 2, the third oil pressure switch has high pressure alarm, and the telescopic rod is extended;

[0023] Step 3, the first electromagnetic valve is powered off, then the first oil pressure switch has low pressure alarm, and then the first cartridge valve is closed;

[0024] Step 4, wait for a period of time to ensure that the first cartridge valve is closed tightly;

[0025] Step 5, the second electromagnetic valve is powered on, then the second oil pressure switch has low pressure alarm, and then the second cartridge valve is opened;

[0026] Step 6, the third oil pressure switch has high pressure alarm, and the telescopic rod is retracted;

[0027] Step 7, the second electromagnetic valve is powered off, then the second oil pressure switch has low pressure alarm, and then the second cartridge valve is closed;

[0028] Step 8, the fourth isolation valve is opened;

[0029] Step 9, the fourth isolation valve is closed.

[0030] As one of the ways that can be realized, in step 4, more than 30s is waited to ensure that the first cartridge valve is closed tightly.

[0031] As one of the ways that can be realized, in step 4, 120s is waited.

[0032] As one of the ways that can be realized, the third oil pressure switch has a value higher than the residual pressure between the first cartridge valve and the second cartridge valve during the main steam isolation valve load test.

[0033] As one of the ways that can be realized, the third oil pressure switch has a value of 1000psi.

[0034] As one of the ways that can be realized, in step 8, the fourth isolation valve is opened for a period of time to release the residual pressure between the first cartridge valve and the second cartridge valve.

[0035] As one of the ways that can be achieved, in step 8, the fourth isolation valve (5-10) is opened for 5-10 seconds.

[0036] The beneficial technical effects of the present application are as follows:

[0037] The main steam isolation valve load test system and method of the present application, by using a throttling element instead of an overpressure valve, modifying the opening and closing time of the isolation valve, delaying the action time interval of the plug-in valve, and optimizing the alarm setting value of the oil pressure switch, realizes daily oil circuit double isolation, the main steam isolation valve does not abnormally close during the main steam isolation valve load test, the residual pressure between the plug-in valves does not cause high pressure alarm, and the residual pressure between the plug-in valves can be discharged after the main steam isolation valve load test; the first-time qualification rate of the main steam isolation valve load test is 100%. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a use schematic view of an embodiment of the existing main steam isolation valve load test system;

[0039] Figure 2 It is a structure schematic view of an embodiment of the main steam isolation valve load test system of the present application.

[0040] In the figure, DV1, first plug-in valve; DV2, second plug-in valve; SV1, first electromagnetic valve; SV2, second electromagnetic valve; FCA, regulating valve; IA, telescopic rod; NNSV1, first isolation valve; PSSV1, first oil pressure switch; NNSV2, second isolation valve; PSSV2, second oil pressure switch; NVA, third isolation valve; PSA, third oil pressure switch; OVA, overpressure valve; NVY, fourth isolation valve; TPSV1, first pressure gauge interface; TPSV2, second pressure gauge interface; TPA, third pressure gauge interface. DETAILED DESCRIPTION

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the description and claims of this application as well as the above abstract are intended to cover not only the embodiments described herein but also any alternatives, modifications, equivalents, and substitutes for those embodiments included within the scope of the application; the description and claims of this application as well as the above abstract are intended to cover any and all alternatives, modifications, equivalents, and substitutes for those embodiments included within the scope of the application; the terms "comprise", "comprising", "include", "including", and "includes" used in the description and the claims of this application as well as the above abstract are intended to be inclusive or open and not restrictive; the terms "first", "second", and the like specified embodiments are used only for distinguishing between different objects discussed and are not necessarily used to describe a particular sequential order.

[0042] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combinable with other embodiments.

[0043] In the present application, unless specifically and explicitly defined otherwise, the terms "mounting", "connection", "connecting", "fixing" and the like are to be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] The technical solutions of the present application are described clearly and completely below in combination with the drawings and specific embodiments.

[0045] The inventor further analyzes the problems existing in the main steam isolation valve load test system, and finds that the main reasons for the problems existing in the main steam isolation valve load test system are as follows:

[0046] 1. The overpressure valve OVA has poor reliability, and the overpressure valve OVA is not reasonably set. The original design of the overpressure valve OVA is to open at low pressure and close at high pressure, which is a double-way plug-in valve with fast closing. That is, the first plug-in valve is theoretically considered to have non-zero leakage, to avoid high pressure alarm in daily use, and to meet the pressure requirement of the main steam isolation valve load test. The O-ring of the overpressure valve OVA is installed in the bevel groove. During the closing process, the O-ring of the overpressure valve OVA is squeezed, expanded and rolled, which is easy to cause O-ring falling off, crushing and internal leakage, resulting in the disappearance of the intermediate pressure during the main steam isolation valve load test. Due to the unstable opening and closing performance of the overpressure valve OVA, the residual oil pressure between the plug-in valves at the end of the main steam isolation valve load test may cause the overpressure valve OVA to be closed and the pressure to be higher than the third oil pressure switch PSA, resulting in high pressure alarm recurrence. Because the overpressure valve OVA is set, the overpressure valve OVA is always open in daily use, and the main steam isolation valve fast closing circuit branch actually has only single sealing in daily use, so that the first plug-in valve DV1 becomes a key sensitive component. If the first plug-in valve DV1 is not tightly sealed, the oil pump cannot compensate the pressure, which may cause the risk of valve closing and reactor shutdown.

[0047] 2、The action interval time of the cartridge valve is not reasonable. The viscosity of hydraulic oil is greatly affected by temperature. For example, the viscosity of hydraulic oil at 20℃ is 3 times that at 40℃. The viscosity of hydraulic oil has an impact on the action performance of the cartridge valve. When the viscosity is high, the time required for complete closing and sealing is longer than when the viscosity is low. The factory-set action interval time of the cartridge valve of 30s is insufficient to meet the condition that the first cartridge valve is completely closed and sealed when the second cartridge valve is opened under various conditions.

[0048] 3、The third oil pressure switch PSA has an unreasonable set value. Since the fast closing cartridge valve is lower than the oil tank, the fast closing oil is pressed into the oil tank from bottom to top. When the second cartridge valve DV2 is closed, the oil between the first cartridge valve DV1 and the second cartridge valve DV2 is squeezed and there is residual oil pressure. According to the external pressure gauge, the transient value of the residual pressure generated each time is between (500-700) psi. Since the alarm set value of the third oil pressure switch PSA is 500 psi, when the residual pressure between the cartridge valves is higher than the set value of the third oil pressure switch PSA and lower than the opening and closing value of the overpressure valve OVA after the main steam isolation valve load test is completed, the high pressure alarm is repeated and maintained, which restricts the next main steam isolation valve load test.

[0049] In order to solve the problems existing in the main steam isolation valve load test system during the main steam isolation valve load test, the embodiment provides a main steam isolation valve load test system for verifying the availability of the fast closing loop of the main steam isolation valve during the main steam isolation valve load test, which comprises: a first cartridge valve DV1, a second cartridge valve DV2, a first electromagnetic valve SV1, a second electromagnetic valve SV2, a regulating valve FCA, a telescopic rod IA, a first isolation valve NNSV1, a first oil pressure switch PSSV1, a second isolation valve NNSV2, a second oil pressure switch PSSV2, a third isolation valve NVA, a third oil pressure switch PSA, a throttling element and a fourth isolation valve NVY.

[0050] The first cartridge valve DV1 controls the opening and closing state through the first electromagnetic valve SV1, and the second cartridge valve DV2 controls the opening and closing state through the second electromagnetic valve SV2. The inlet of the first cartridge valve DV1 is connected with the oil cylinder pipeline of the main steam isolation valve, and the outlet of the first cartridge valve DV1 is connected with the inlet pipeline of the second cartridge valve DV2.

[0051] The piston side of the first cartridge valve DV1 is connected with the inlet pipeline of the first electromagnetic valve SV1 and the first isolation valve NNSV1 respectively. The outlet of the first isolation valve NNSV1 is connected with the pipeline of the first oil pressure switch PSSV1.

[0052] The piston side of the second cartridge valve DV2 is connected with the inlet pipeline of the second electromagnetic valve SV2 and the second isolation valve NNSV2 respectively. The outlet of the second isolation valve NNSV2 is connected with the pipeline of the second oil pressure switch PSSV2.

[0053] The outlet of the second insertion valve DV2 is connected with the regulating valve FCA pipeline; the outlet of the first insertion valve DV1 is respectively connected with the inlet of the third isolation valve NVA and the inlet of the third isolation valve NVA through the pipeline connected with the extension rod IA and the third isolation valve NVA; the outlet of the third isolation valve NVA is respectively connected with the third oil pressure switch PSA and the throttling element pipeline; the throttling element is connected with the fourth isolation valve NVY pipeline;

[0054] The inlet of the first isolation valve NNSV1 is connected with the inlet of the first electromagnetic valve SV1 through the pipeline, and the inlet of the first isolation valve NNSV1 is provided with the first pressure gauge interface TPSV1 on the pipeline connected with the first electromagnetic valve SV1;

[0055] The inlet of the second isolation valve NNSV2 is connected with the inlet of the second electromagnetic valve SV2 through the pipeline, and the inlet of the second isolation valve NNSV2 is provided with the second pressure gauge interface TPSV2 on the pipeline connected with the second electromagnetic valve SV2;

[0056] The inlet of the third isolation valve NVA is connected with the extension rod IA through the pipeline, and the inlet of the third isolation valve NVA is provided with the third pressure gauge interface TPA on the pipeline connected with the extension rod IA.

[0057] In the embodiment, as one of the implementable modes, the throttling element is a pipeline connecting piece with throttling function.

[0058] In the embodiment, as one of the implementable modes, the fourth isolation valve NVY is normally closed to realize double isolation of the daily oil circuit.

[0059] The embodiment also provides a main steam isolation valve load test method, which uses the main steam isolation valve load test system and comprises the following steps.

[0060] Step 1, under the condition that the third oil pressure switch PSA has no high-pressure alarm, the first electromagnetic valve SV1 is powered on, then the first oil pressure switch PSSV1 low-pressure alarm appears, and then the first insertion valve DV1 is opened;

[0061] Step 2, the third oil pressure switch PSA high-pressure alarm appears, and the extension rod IA is extended;

[0062] Step 3, the first electromagnetic valve SV1 is powered off, then the first oil pressure switch PSSV1 low-pressure alarm disappears, and the first insertion valve DV1 is closed;

[0063] Step 4, wait for a period of time to ensure that the first insertion valve DV1 has been closed tightly;

[0064] Step 5, the second electromagnetic valve SV2 is powered on, then the second oil pressure switch PSSV2 low-pressure alarm appears, and then the second insertion valve DV2 is opened;

[0065] Step 6, the third oil pressure switch PSA high pressure alarm disappears, the telescopic rod IA retracts;

[0066] Step 7, the second solenoid valve SV2 loses power and closes, then the second oil pressure switch PSSV2 low pressure alarm disappears, and then the second cartridge valve DV2 closes;

[0067] Step 8, open the fourth isolation valve NVY;

[0068] Step 9, close the fourth isolation valve NVY, and the test is completed.

[0069] In this embodiment, as one of the ways that can be realized, in step 4, wait for more than 30s to ensure that the first cartridge valve DV1 has been closed tightly when the second cartridge valve DV2 is opened, avoiding the risk of rapid closing of the main steam isolation valve due to the first cartridge valve DV1 not being closed tightly when the second cartridge valve DV2 is opened.

[0070] In this embodiment, as one of the ways that can be realized, in step 4, wait for 120s to ensure that the first cartridge valve DV1 has been closed tightly when the second cartridge valve DV2 is opened, avoiding the risk of rapid closing of the main steam isolation valve due to the first cartridge valve DV1 not being closed tightly when the second cartridge valve DV2 is opened.

[0071] In this embodiment, as one of the ways that can be realized, the third oil pressure switch PSA has a set value higher than the residual pressure between the first cartridge valve DV1 and the second cartridge valve DV2 during the main steam isolation valve load test, eliminating the high pressure alarm caused by the residual pressure between the first cartridge valve DV1 and the second cartridge valve DV2 during the main steam isolation valve load test.

[0072] In this embodiment, as one of the ways that can be realized, the third oil pressure switch PSA has a set value of 1000psi, eliminating the high pressure alarm caused by the residual pressure between the first cartridge valve DV1 and the second cartridge valve DV2 during the main steam isolation valve load test.

[0073] In this embodiment, as one of the ways that can be realized, the fourth isolation valve NVY is opened for a period of time to release the residual pressure between the first cartridge valve DV1 and the second cartridge valve DV2.

[0074] The pressure relief between the first cartridge valve DV1 and the second cartridge valve DV2 is achieved through the fourth isolation valve NVY; after the main steam isolation valve load test is completed, the fourth isolation valve NVY is opened to release the residual pressure between the first cartridge valve DV1 and the second cartridge valve DV2, ensuring that the residual pressure between the first cartridge valve DV1 and the second cartridge valve DV2 does not cause a high pressure alarm before the next main steam isolation valve load test.

[0075] In this embodiment, as one of the implementable modes, in step 8, the fourth isolation valve NVY is opened for 5-10 s.

[0076] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A main steam isolation valve load test system is used for the main steam isolation valve load test to verify the availability of the main steam isolation valve fast closing circuit, characterized in that: include: First cartridge valve (DV1), second cartridge valve (DV2), first solenoid valve (SV1), second solenoid valve (SV2), regulating valve (FCA), telescopic rod (IA), first isolation valve (NNSV1), first oil pressure switch (PSSV1), second isolation valve (NNSV2), second oil pressure switch (PSSV2), third isolation valve (NVA), third oil pressure switch (PSA), throttling element and fourth isolation valve (NVY); The first cartridge valve (DV1) controls the on / off state through the first solenoid valve (SV1), and the second cartridge valve (DV2) controls the on / off state through the second solenoid valve (SV2); the inlet of the first cartridge valve (DV1) is connected to the oil cylinder pipeline of the main steam isolation valve, and the outlet of the first cartridge valve (DV1) is connected to the inlet pipeline of the second cartridge valve (DV2); The piston side of the first cartridge valve (DV1) is connected to the inlet pipelines of the first solenoid valve (SV1) and the first isolation valve (NNSV1) respectively; the outlet of the first isolation valve (NNSV1) is connected to the pipeline of the first oil pressure switch (PSSV1); the piston side of the second cartridge valve (DV2) is connected to the inlet pipelines of the second solenoid valve (SV2) and the second isolation valve (NNSV2) respectively; The outlet of the second isolation valve (NNSV2) is connected to the pipeline of the second oil pressure switch (PSSV2); The outlet of the second cartridge valve (DV2) is connected to the regulating valve (FCA) pipeline; the pipeline connecting the outlet of the first cartridge valve (DV1) and the inlet of the second cartridge valve (DV2) is respectively connected to the telescopic rod (IA) and the inlet of the third isolation valve (NVA); the outlet of the third isolation valve (NVA) is respectively connected to the third oil pressure switch (PSA) and the throttle element pipeline; the throttle element is connected to the fourth isolation valve (NVY) pipeline; The inlet of the first isolation valve (NNSV1) is connected to the inlet pipeline of the first solenoid valve (SV1), and a first pressure gauge interface (TPSV1) is provided on the pipeline connecting the inlet of the first isolation valve (NNSV1) and the first solenoid valve (SV1); The inlet of the second isolation valve (NNSV2) is connected to the inlet pipeline of the second solenoid valve (SV2), and a second pressure gauge interface (TPSV2) is provided on the pipeline connecting the inlet of the second isolation valve (NNSV2) and the second solenoid valve (SV2); The inlet of the third isolation valve (NVA) is connected to the telescopic rod (IA) pipeline, and a third pressure gauge interface (TPA) is provided on the pipeline connecting the inlet of the third isolation valve (NVA) and the telescopic rod (IA).

2. The main steam isolation valve load test system according to claim 1 is characterized in that: The throttling element is a pipe connecting piece with throttling function.

3. The main steam isolation valve load test system according to claim 1 is characterized in that: The fourth isolation valve (NVY) is normally closed.

4. A main steam isolation valve load test method, characterized in that: The main steam isolation valve load test system according to any one of claims 1 to 3 comprises the following steps: Step 1: When the third oil pressure switch (PSA) does not have a high pressure alarm, the first solenoid valve (SV1) is energized and opened, and then the first oil pressure switch (PSSV1) has a low pressure alarm, and then the first cartridge valve (DV1) is opened; Step 2: The high pressure alarm of the third oil pressure switch (PSA) sounds, and the telescopic rod (IA) extends; Step 3: The first solenoid valve (SV1) loses power and closes, and then the low pressure alarm of the first oil pressure switch (PSSV1) disappears, and the first cartridge valve (DV1) closes; Step 4: Wait for a while to ensure that the first cartridge valve (DV1) is tightly closed; Step 5: The second solenoid valve (SV2) is energized and opened, and then the second oil pressure switch (PSSV2) low pressure alarm is issued, and then the second cartridge valve (DV2) is opened; Step 6: The high-pressure alarm of the third oil pressure switch (PSA) disappears, and the telescopic rod (IA) retracts; Step 7: The second solenoid valve (SV2) loses power and closes, then the low pressure alarm of the second oil pressure switch (PSSV2) disappears, and then the second cartridge valve (DV2) closes; Step 8: Open the fourth isolation valve (NVY); Step 9: Close the fourth isolation valve (NVY).

5. The main steam isolation valve load test method according to claim 4 is characterized in that: In step 4, wait for more than 30 seconds to ensure that the first cartridge valve (DV1) is tightly closed.

6. The main steam isolation valve load test method according to claim 5 is characterized in that: In step 4, wait for 120 seconds.

7. The main steam isolation valve load test method according to claim 4 is characterized in that: The third oil pressure switch (PSA) is set to a value higher than the residual pressure between the first cartridge valve (DV1) and the second cartridge valve (DV2) during the main steam isolation valve load test.

8. The main steam isolation valve load test method according to claim 4 is characterized in that: The third oil pressure switch (PSA) is set to 1000 psi.

9. The main steam isolation valve load test method according to claim 4 is characterized in that: In step 8, the fourth isolation valve (NVY) is opened for a period of time to release the residual pressure between the first cartridge valve (DV1) and the second cartridge valve (DV2).

10. The main steam isolation valve load test method according to claim 9, characterized in that: Open the fourth isolation valve (NVY) (5~10)s.

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