A test loop and test method for testing the mechanical seal of a nuclear main pump

Abstract

The present invention relates to a test loop for testing a mechanical seal for a nuclear main pump, which comprises: a main loop system and a pressure control system; the main loop system includes a water tank and a mechanical seal tooling; the outlet of the water tank is connected to the inlet of the mechanical seal tooling through a main pipeline; a plunger pump is arranged on the main pipeline; the reflux outlet of the mechanical seal tooling is connected to the inlet of the water tank, and a closed loop is formed between the water tank and the mechanical seal tooling; the pressure control system includes an expansion tank and a pressure source; wherein, the expansion tank provides static pressure to the closed loop formed by the water tank and the mechanical seal tooling, the first medium in the water tank flows along the main pipeline to the mechanical seal tooling under the power provided by the plunger pump, and then flows back to the water tank through the mechanical seal tooling, so as to conduct a seal test on the mechanical seal tooling. The test loop for testing the mechanical seal for the nuclear main pump provided by the present invention has the advantages of clean medium, capable of conducting thermal shock tests, and high safety performance.

Description

Technical Field

[0001] The present invention belongs to the field of testing, and more specifically, relates to a test loop and a test method for testing a mechanical seal for a nuclear main pump. Background Art

[0002] The mechanical seal for a nuclear main pump is used to control the leakage of reactor coolant along the pump shaft. It is a key component of the main pump and is closely related to the safe and reliable operation of the main pump. Since the mechanical seal mechanism involves multiple disciplines such as tribology, material science, fluid mechanics, solid mechanics, heat transfer, and lubrication theory, a complete design theory has not been formed yet, and many data are obtained through experiments. However, since many mechanical seal manufacturers can only conduct single and non-online experiments. Therefore, it is particularly important to have a fully functional and complete test loop. Summary of the Invention

[0003] The purpose of the present invention is to provide a test loop and a test method for testing a mechanical seal for a nuclear main pump, which can truly simulate the operation of the mechanical seal for a nuclear main pump under actual working conditions to verify that the design of the mechanical seal meets the requirements of the technical specification and ensure the safety and reliability of the mechanical seal during the operation of the nuclear main pump.

[0004] To achieve the above purpose, the present invention provides a test loop for testing a mechanical seal for a nuclear main pump, which includes: a main loop system and a pressure control system; the main loop system includes a water tank and a mechanical seal tooling; the outlet of the water tank is connected to the inlet of the mechanical seal tooling through a main pipeline; a plunger pump is arranged on the main pipeline; the reflux outlet of the mechanical seal tooling is connected to the inlet of the water tank, and a closed loop is formed between the water tank and the mechanical seal tooling; the pressure control system includes an expansion tank and a pressure source, the lower end of the expansion tank is connected to the main pipeline in the main loop system, and the pressure source provides compressed air to the expansion tank; wherein, the expansion tank provides static pressure to the closed loop formed by the water tank and the mechanical seal tooling, and the first medium in the water tank flows along the main pipeline to the mechanical seal tooling under the power provided by the plunger pump and returns to the water tank through the mechanical seal tooling to conduct a seal test on the mechanical seal tooling.

[0005] Among them, the test loop for the mechanical seal of the nuclear main pump further includes a cooling system, and the cooling system includes a cooling tower and a plate heat exchanger; the plate heat exchanger is respectively connected in series with the water tank and the cooling tower through two different pipelines to cool down the main loop system; a fourth electric control valve is also arranged between the plate heat exchanger and the water tank. Among them, the test loop for the mechanical seal of the nuclear main pump further includes a heating system, and the heating system includes an electric heating tank and a third electric control valve; the outlet of the electric heating tank is connected with the outlet of the water tank through a main pipeline; the third electric control valve is arranged between the plate heat exchanger and the electric heating tank; among them, by adjusting the fourth electric control valve and the third electric control valve, the mechanical seal tooling can be respectively connected with the water tank or the electric heating tank to conduct a normal test or a thermal shock test on the mechanical seal tooling.

[0006] Among them, the main pipeline is provided with a diversion port through the plunger pump, and after passing through the diversion port, the main pipeline is divided into a first pipeline and a second pipeline. The first pipeline is connected to the inlet of the mechanical seal tooling, and the second pipeline is connected to the inlet of the water tank; among them, a confluence port is also provided on the second pipeline.

[0007] Among them, the mechanical seal tooling includes a three-stage seal tooling arranged on its upper part and a balance seal tooling arranged on its lower part; the three-stage seal tooling is provided with: a first leakage outlet, which is connected to a first measuring cup for measuring the low-pressure leakage of the mechanical seal tooling, and a first return outlet, which is connected to the confluence port on the second pipeline through a third pipeline; the balance seal tooling is provided with: a second leakage outlet, which is connected to a second measuring cup for measuring the balance seal leakage of the mechanical seal tooling, and a second return outlet, which is connected to the confluence port on the second pipeline through a fourth pipeline; among them, the third pipeline and the fourth pipeline converge at the confluence port and are then connected to the water tank through the second pipeline.

[0008] Among them, a first pneumatic control valve and a second flowmeter are sequentially arranged on the second pipeline between the diversion port and the confluence port; a second pneumatic control valve and a fourth flowmeter are sequentially arranged on the fourth pipeline between the second return outlet and the confluence port for regulating the flow rate of the test seal injection water of the mechanical seal tooling; a first electric control valve and a third flowmeter are sequentially arranged on the third pipeline between the first return outlet and the confluence port, which are respectively used to control the conduction or cut-off of the third pipeline and measure the flow rate of the third pipeline.

[0009] Among them, an air outlet pipe is arranged at the upper end of the expansion tank; an electromagnetic valve is also arranged on the air outlet pipe. When the pressure in the closed loop exceeds the set value, the electromagnetic valve opens, and gas is released to the outside through the air outlet pipe to ensure that the pressure in the closed loop is within the safe range.

[0010] Among them, the plate heat exchanger plate includes a primary side and a secondary side. The primary side of the plate heat exchanger is connected in series with the second pipeline; the secondary side of the plate heat exchanger is connected in series with the cooling tower through the sixth pipeline, and the cooling tower and the plate heat exchanger form a closed loop; the second medium stored in the cooling tower flows along the sixth pipeline, and the second medium flows to the plate heat exchanger. The second medium on the secondary side of the plate heat exchanger absorbs the heat of the first medium on the primary side of the plate heat exchanger, and the second medium after absorbing the heat flows back to the cooling tower along the sixth pipeline from the secondary side to form a cooling cycle; a circulation pump, a second electric control valve and a fifth flow meter are sequentially arranged on the closed loop formed by the cooling tower and the plate heat exchanger to control the flow rate of the second medium in the cooling circulation system.

[0011] A test method for the mechanical seal of a nuclear main pump, the test method can carry out a normal operation test, and the test process is as follows:

[0012] Step S1: Open the fourth electric control valve and close the third electric control valve, so that the water tank is connected to the mechanical seal tooling through the main pipeline and the first pipeline and disconnected from the electric heating tank;

[0013] Step S2: Fill the entire test loop with the first medium, and the pressure source injects compressed air into the expansion tank to provide static pressure to the test loop;

[0014] Step S3: Start the plunger pump. When the minimum pressure for starting the mechanical seal tooling is reached, start the mechanical seal tooling to operate;

[0015] Step S4: Adjust the opening degrees of the second pneumatic control valve and the first pneumatic control valve to meet the working condition requirements for the normal operation of the mechanical seal tooling;

[0016] Step S5: The first medium in the water tank flows into the mechanical seal tooling through the main pipeline and the first pipeline, and flows back to the water tank from the return outlet; during the test process, observe the leakage amounts of the first measuring cup and the second measuring cup, that is, observe the low-pressure leakage amount and the balance seal leakage amount of the mechanical seal tooling respectively;

[0017] Step S6: Shut down the mechanical seal tooling and the plunger pump after the test ends;

[0018] In the step S3, the minimum pressure for starting the mechanical seal tooling ≥ 2 MPa;

[0019] In the step S5, the temperature of the injected first medium is controlled between 25 and 55 °C.

[0020] Among them, the test method can also be switched from a normal operation test to a thermal shock test, and the thermal shock test process is as follows:

[0021] Step S1: Use the electric heating tank to heat up the stored third medium;

[0022] Step S2: When the temperature of the third medium rises to the thermal shock required temperature, close the fourth electric control valve and open the third electric control valve, so that the electric heating tank is connected to the mechanical seal tooling through the main pipeline and the first pipeline and disconnected from the water tank;

[0023] Step S3: Keep the plunger pump and the mechanical seal tooling open and running. The third medium enters the mechanical seal tooling through the main pipeline and the first pipeline and returns to the electric heating tank through the reflux outlet; the temperature inside the mechanical seal tooling will instantly increase due to the inflow of the third medium, forming a thermal shock;

[0024] Step S4: Observe the leakage amounts of the first measuring cup and the second measuring cup during the thermal shock test, that is, observe the low-pressure leakage amount and the balance seal leakage amount of the mechanical seal tooling respectively;

[0025] Step S5: Shut down the mechanical seal tooling and the plunger pump after the test.

[0026] In summary, compared with the prior art, a test loop and a test method for testing the mechanical seal of a nuclear main pump have the following beneficial effects: 1. The medium energy used in the test loop of the present invention is clean and environmentally friendly; 2. The test loop of the present invention can not only simulate the normal operation test, but also perform a thermal shock test on the mechanical seal using the hot medium heated by the electric heating tank; 3. The test loop of the present invention realizes the automatic control of the pressure of the test loop by setting a pressure control system, effectively preventing potential safety hazards caused by excessive pressure in the test loop; 4. The test loop of the present invention ensures that the test loop operates at the temperature required for the test by setting a cooling system, improving the accuracy of the test. Brief Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of the test loop for testing the mechanical seal of a nuclear main pump of the present invention. Detailed Embodiments

[0028] The following will combine the attached drawings in the embodiments of the present invention Figure 1 to detail the technical solutions, structural features, achieved purposes and effects in the embodiments of the present invention.

[0029] It should be noted that the drawings adopt a very simplified form and all use non-precise scales, only for the purpose of conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention, and are not used to limit the limiting conditions of the embodiments of the present invention. Therefore, they do not have technical substance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed by the present invention.

[0030] It should be noted that in the present invention, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements expressly listed, but also other elements not expressly listed or elements inherent to such process, method, article or device.

[0031] The present invention provides a test loop for testing a mechanical seal for a nuclear main pump, as Figure 1 shown. The test loop for testing the mechanical seal for the nuclear main pump includes: a main loop system A, a pressure control system B, a heating system C, and a cooling system D;

[0032] Among them, the main loop system A includes: a water tank 1 and a mechanical seal tooling 3; an outlet E10 and an inlet E11 are provided at the lower end of the water tank 1. The outlet E10 is connected to the inlet E30 of the mechanical seal tooling 3 through a main pipeline R0. A plunger pump 01 is provided on the main pipeline R0 between the outlet E10 of the water tank 1 and the inlet E30 of the mechanical seal tooling 3. The plunger pump 01 is a metering pump, which is used to provide power for the first medium stored in the water tank 1 and control the flow rate of the first medium entering the mechanical seal tooling 3. A shunt port K1 is provided on the main pipeline R0 after passing through the plunger pump 01. After passing through the shunt port K1, the main pipeline R0 is divided into two parallel first pipelines R1 and second pipelines R2. The first pipeline R1 is connected to the inlet E30 of the mechanical seal tooling 3, and a first flow meter F01 is provided on the first pipeline R1. The second pipeline R2 is connected to the inlet E11 of the water tank 1, and a confluence port K2 is provided on the second pipeline R2. A first pneumatic regulating valve 04 and a second flow meter F06 are sequentially provided on the second pipeline R2 between the shunt port K1 and the confluence port K2. The first medium (the first medium in this embodiment is water) stored in the water tank 1 flows out from the outlet E10 of the water tank 1 and flows along the main pipeline R0. After passing through the plunger pump 01, one part flows into the mechanical seal tooling 3 along the first pipeline R1, and the other part flows back to the water tank 1 along the second pipeline R2.

[0033] Among them, the upper part of the mechanical seal tooling 3 is a three-stage seal tooling, and the lower part is a balance seal tooling; there are two outlets on the three-stage seal tooling. The first outlet E31 (leakage outlet) is connected to a first measuring cup F02, which is used to measure the low-pressure leakage of the mechanical seal tooling 3. The second outlet E32 (return outlet) is connected to the confluence port K2 of the second pipeline R2 through the third pipeline R3. And a first electric control valve 02 and a third flowmeter F04 are sequentially arranged on the third pipeline R3 between the second outlet E32 and the confluence port K2; the balance seal tooling is provided with two outlets. The third outlet E33 (leakage outlet) is connected to a second measuring cup F03, which is used to measure the balance seal leakage of the mechanical seal tooling 3. The fourth outlet E34 (return outlet) is connected to the confluence port K2 of the second pipeline R2 through the fourth pipeline R4. And a second pneumatic control valve 03 and a fourth flowmeter F05 are sequentially arranged on the fourth pipeline R4 between the fourth outlet E34 and the confluence port K2. The third pipeline R3 and the fourth pipeline R4 converge at the confluence port K2 of the second pipeline R2 and then are connected to the water tank 1 through the second pipeline R2.

[0034] Among them, the first electric control valve 02 remains open during the normal operation test of the loop and does not need to be operated. When conducting the accident condition test (simulating the high-pressure leakage shutdown test), the electric control valve 02 plays a role in cutting off the flow of the third pipeline R3; the third flowmeter F04 is used to measure the pipeline flow of the third pipeline R3, that is, the high-pressure leakage pipeline flow (the normal range is between 800 and 850 L); by observing the flow rates of the fourth flowmeter F05 and the second flowmeter F06, the opening degrees of the second pneumatic control valve 03 and the first pneumatic control valve 04 are adjusted, thereby adjusting the injection flow rate of the first medium in the first pipeline R1 flowing into the mechanical seal tooling 3, so that the flow rate of the fourth flowmeter F05 is at 1 m 3 / h, the flow rate of the second flowmeter F06 is at 4.2 m 3 / h, and the flow rate of the first flowmeter F01 for injecting water into the mechanical seal tooling 3 is at 1.8 m 3 / h; the first medium in the first pipeline R1 flowing into the mechanical seal tooling 3 is divided into two paths. One path flows upward and flows out after passing through the three-stage seal tooling; the other path flows downward and flows out after passing through the balance seal tooling.

[0035] Among them, the pressure control system B includes: an expansion tank 5, a solenoid valve 07, and a pressure source 501; an air outlet pipe E51 extends from the upper end of the expansion tank 5, and the lower end stores a first medium (the first medium is water in this embodiment) and is connected to the main pipeline R0; a solenoid valve 07 is arranged on the air outlet pipe E51. A pressure value is set for the solenoid valve 07. When the loop pressure exceeds the set value, the solenoid valve 07 automatically opens to release gas to the outside. When the loop pressure is lower than the set value, the solenoid valve 07 automatically closes, which can ensure that the pressure of the test loop is within a safe range; the installation height of the expansion tank 5 is higher than any equipment in the entire closed test loop. The pressure source 501 injects compressed air from the top of the expansion tank 5 to apply pressure to the first medium in the expansion tank 5, thereby providing static pressure to the entire closed test loop. At the same time, since the lower end inside the expansion tank 5 always stores the first medium, it can effectively prevent compressed air from entering the test loop.

[0036] Among them, the cooling system D includes: a cooling tower 6 and a plate heat exchanger 4; the cooling tower 6 stores a second medium for cooling the pipeline in the main loop system A; the plate heat exchanger 4 includes a primary side (hot side) and a secondary side (cold side). The primary side of the plate heat exchanger 4 is connected in series with the second pipeline R2, that is, the primary side of the plate heat exchanger is connected in series with the main loop system A; the secondary side of the plate heat exchanger 4 is connected in series with the cooling tower 6 through the sixth pipeline R6, and the cooling tower 6 and the plate heat exchanger 4 form a circular closed loop.

[0037] It should be noted that when the cooling system D operates, the second medium (the second medium is water in this embodiment) flows out of the cooling tower 6 and flows along the sixth pipeline R6. When the second medium flows to the plate heat exchanger 4, the second medium in the sixth pipeline R6 on the secondary side of the plate heat exchanger 4 absorbs the heat of the first medium in the second pipeline R2 on the primary side of the plate heat exchanger 4. After absorbing the heat, the second medium flows back to the cooling tower 6 along the sixth pipeline R6 from the secondary side. The cooling tower 6 cools the second medium, and the cooled second medium re-enters the sixth pipeline R6 to form a cooling cycle.

[0038] Among them, a circulation pump 09, a second electric control valve 10, and a fifth flowmeter F07 are sequentially arranged on the sixth pipeline R6 in the cooling system D; the heat exchange rate of the plate heat exchanger 4 is controlled by observing the flow value of the fifth flowmeter F07 on the secondary side. The opening of the second electric control valve 10 is adjusted according to the flow rate of the fifth flowmeter F07, thereby controlling the temperature of the test loop (the larger the flow rate of the plate heat exchanger 4, the better the heat exchange effect); the circulation pump 09 makes the second medium in the sixth pipeline R6 circulate.

[0039] Among them, the heating system C includes: an electric heating tank 2 and a third electric control valve 06; the outlet E20 of the electric heating tank 2 and the outlet E10 of the water tank 1 are connected in parallel through a pipeline to the main pipeline R0. The electric heating tank 2 is used to heat the third medium (the third medium is water in this embodiment).

[0040] Among them, the second pipeline R2 passes through the plate heat exchanger 4 and is then respectively connected in parallel to the inlet E11 of the water tank 1 and the inlet E21 of the electric heating tank 2 through two different pipelines.

[0041] Among them, the third electric control valve 06 is arranged on the pipeline between the plate heat exchanger 4 and the electric heating tank 2; a fourth electric control valve 05 is also arranged on the pipeline between the plate heat exchanger 4 and the water tank 1; by adjusting the opening and closing of the fourth electric control valve 05 and the third electric control valve 06, the test type of the test loop is controlled; when the fourth electric control valve 05 is opened and the third electric control valve 06 is closed, the water tank 1 is connected to the mechanical seal tooling 3 through the main pipeline R0 and the first pipeline R1 and is disconnected from the electric heating tank 2, and the test loop is in normal operation test; on the contrary, when the fourth electric control valve 05 is closed and the third electric control valve 06 is opened, the electric heating tank 2 is connected to the mechanical seal tooling 3 through the main pipeline R0 and the first pipeline R1 and is disconnected from the water tank 1, and the test loop is in thermal shock test.

[0042] The thermal shock test is used to test the sealing performance of the mechanical seal tooling 3 under instantaneous high temperature. When the test loop conducts the thermal shock test, the third medium is preheated by the electric heating tank 2 in advance. When the temperature of the third medium in the electric heating tank 2 rises to the temperature required for the thermal shock test, the third medium enters the mechanical seal tooling 3 through the main pipeline R0 and the first pipeline R1. The temperature inside the mechanical seal tooling 3 will instantaneously increase due to the inflow of the third medium, forming a thermal shock; by switching the electric control valve, that is, opening the third electric control valve 06 and closing the fourth electric control valve 05 at the same time, the flow direction of the third medium is limited. Since the fourth electric control valve 05 is in the closed state, the third medium flows back to the electric heating tank 2 through the plate heat exchanger 4 and the third electric control valve 06.

[0043] Among them, pressure gauges and thermometers are respectively arranged on the first pipeline R1, the second pipeline R2, the third pipeline R3, the sixth pipeline R6, the water tank 1, the electric heating tank 2, the mechanical seal tooling 3 and the expansion tank 5 to monitor the pressure and temperature of the test loop.

[0044] It should be noted that when the test loop for testing the mechanical seal of the nuclear main pump conducts the normal operation test, the test process is as follows:

[0045] Step S1: Open the fourth electric control valve 05 and close the third electric control valve 06, so that the water tank 1 is connected to the mechanical seal tooling 3 through the main pipeline R0 and the first pipeline R1 and disconnected from the electric heating tank 2;

[0046] Step S2: Fill the entire test loop with the first medium, and the pressure source 501 injects 3 bar of compressed air into the expansion tank 5, that is, provides static pressure for the entire test loop;

[0047] Step S3: Start the plunger pump 01. When the minimum pressure (≥2 MPa) for starting the mechanical seal tooling 3 is reached, start the mechanical seal tooling 3 (the mechanical seal tooling 3 rotates by connecting the rotating shaft with the motor) to operate;

[0048] Step S4: Adjust the opening degrees of the second pneumatic control valve 03 and the first pneumatic control valve 04, so that the flow rate of the fourth flowmeter F05 is about 1 m 3 / h, and the flow rate of the second flowmeter F06 is about 4.2 m 3 / h, that is, the flow rate of the first flowmeter F01 is about 1.8 m 3 / h (because the plunger pump is a metering pump with a flow rate of 6 m 3 / h), meeting the working condition requirements for the normal operation of the mechanical seal tooling 3;

[0049] Step S5: The first medium flows into the mechanical seal tooling 3. During the test process, observe the leakage amounts of the first measuring cup F02 and the second measuring cup F03, that is, observe the low-pressure leakage amount and the balance seal leakage amount of the mechanical seal tooling 3 respectively; Normal operation requires long-term operation for hundreds of hours or even thousands of hours;

[0050] Step S6: Shut down the mechanical seal tooling 3 and the plunger pump 01 after the test ends.

[0051] In the said Step S5, the temperature of the injected first medium is controlled between 25 and 55 °C (that is, the temperature of the water tank 1 should be within this temperature range).

[0052] The test loop for the mechanical seal used in the nuclear main pump of the present invention can also be switched from a normal operation test to a thermal shock test. The test process of the thermal shock test is as follows: First, use the electric heating tank 2 to heat up the third medium; when the third medium is heated to the thermal shock required temperature (such as 80 °C); close the fourth electric control valve 05 and open the third electric control valve 06, so that the electric heating tank 2 is connected to the mechanical seal tooling 3 through the main pipeline R0 and the first pipeline R1 and disconnected from the water tank 1; then keep the plunger pump 01 and the mechanical seal tooling 3 in the open and operating states, and the third medium enters the mechanical seal tooling 3 through the main pipeline R0 and the first pipeline R1. The temperature inside the mechanical seal tooling 3 will instantly increase due to the inflow of the third medium, forming a thermal shock; during the thermal shock test, observe the leakage amounts of the first measuring cup F02 and the second measuring cup F03, that is, observe the low-pressure leakage amount and the balance seal leakage amount of the mechanical seal tooling 3 respectively; after the test, shut down the mechanical seal tooling 3 and the plunger pump 01. In summary, compared with the existing test loop for mechanical seals, the test loop for the mechanical seal used in the nuclear main pump provided by the present invention has the advantages of clean medium, being able to conduct thermal shock tests, and high safety.

[0053] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A test loop for testing the mechanical seal of a nuclear main pump, characterized in that, Comprising: A main circuit system (A) and a pressure control system (B); The main circuit system (A) includes a water tank (1) and a mechanical seal tooling (3); the outlet (E10) of the water tank (1) is connected to the inlet (E30) of the mechanical seal tooling (3) through a main pipeline (R0); a plunger pump (01) is provided on the main pipeline (R0); the reflux outlet of the mechanical seal tooling (3) is connected to the inlet (E11) of the water tank (1), and a closed loop is formed between the water tank (1) and the mechanical seal tooling (3); The pressure control system (B) includes an expansion tank (5) and a pressure source (501), the lower end of the expansion tank (5) is connected to the main pipeline (R0) in the main circuit system (A), and the pressure source (501) supplies compressed air to the expansion tank (5); Wherein, the expansion tank (5) provides static pressure to the closed loop formed by the water tank (1) and the mechanical seal tooling (3), the first medium in the water tank (1) flows along the main pipeline (R0) to the mechanical seal tooling (3) under the power provided by the plunger pump (01), and returns to the water tank (1) through the mechanical seal tooling (3) to perform a seal test on the mechanical seal tooling (3); The test loop for the mechanical seal of the nuclear main pump further includes a cooling system (D), The cooling system (D) includes a cooling tower (6) and a plate heat exchanger (4); the plate heat exchanger (4) is respectively connected in series with the water tank (1) and the cooling tower (6) through two different pipelines to cool down the main circuit system (A); A fourth electric control valve (05) is further provided between the plate heat exchanger (4) and the water tank (1); The test loop for the mechanical seal of the nuclear main pump further includes a heating system (C), The heating system (C) includes an electric heating tank (2) and a third electric control valve (06); the outlet (E20) of the electric heating tank (2) is connected to the outlet (E10) of the water tank (1) through a main pipeline (R0); the third electric control valve (06) is provided between the plate heat exchanger (4) and the electric heating tank (2); Wherein, by adjusting the fourth electric control valve (05) and the third electric control valve (06), the mechanical seal tooling (3) can be respectively communicated with the water tank (1) or the electric heating tank (2) to perform a normal test or a thermal shock test on the mechanical seal tooling (3); Wherein, a shunt port (K1) is provided on the main pipeline (R0) passing through the plunger pump (01), the main pipeline (R0) is divided into a first pipeline (R1) and a second pipeline (R2) after passing through the shunt port (K1), the first pipeline (R1) is connected to the inlet (E30) of the mechanical seal tooling (3), and the second pipeline (R2) is connected to the inlet (E11) of the water tank (1); Wherein, a confluence port (K2) is further provided on the second pipeline (R2).

2. The test loop for the mechanical seal of the nuclear main pump according to claim 1, wherein The mechanical seal tooling (3) includes a three-stage seal tooling provided on its upper part and a balance seal tooling provided on its lower part; The three-stage seal tooling is provided with: a first leakage outlet (E31), which is connected to a first measuring cup (F02) for measuring the low-pressure leakage of the mechanical seal tooling (3), and a first return outlet (E32), which is connected to a confluence port (K2) on the second pipeline (R2) through a third pipeline (R3); The balance seal tooling is provided with: a second leakage outlet (E33), which is connected to a second measuring cup (F03) for measuring the balance seal leakage of the mechanical seal tooling (3), and a second return outlet (E34), which is connected to the confluence port (K2) on the second pipeline (R2) through a fourth pipeline (R4); Wherein, the third pipeline (R3) and the fourth pipeline (R4) converge at the confluence port (K2) and are then connected to the water tank (1) through the second pipeline (R2).

3. The test loop for the mechanical seal of a nuclear main pump according to claim 2, wherein A first pneumatic control valve (04) and a second flowmeter (F06) are sequentially arranged on the second pipeline (R2) between the shunt port (K1) and the confluence port (K2); a second pneumatic control valve (03) and a fourth flowmeter (F05) are sequentially arranged on the fourth pipeline (R4) between the second return outlet (E34) and the confluence port (K2) for adjusting the flow rate of the test seal injection water of the mechanical seal tooling (3); A first electric control valve (02) and a third flowmeter (F04) are sequentially arranged on the third pipeline (R3) between the first return outlet (E32) and the confluence port (K2), which are respectively used to control the on-off of the third pipeline (R3) and measure the flow rate of the third pipeline (R3).

4. The test loop for the mechanical seal of a nuclear main pump according to claim 3, wherein An air outlet pipe (E51) is arranged at the upper end of the expansion tank (5), and a first medium is stored at the lower end; An electromagnetic valve (07) is further arranged on the air outlet pipe (E51). When the pressure in the closed loop exceeds the set value, the electromagnetic valve (07) opens, and gas is released to the outside through the air outlet pipe (E51) to ensure that the pressure in the closed loop is within the safe range.

5. The test loop for the mechanical seal of a nuclear main pump according to claim 4, wherein The plate heat exchanger (4) includes a primary side and a secondary side. The primary side of the plate heat exchanger (4) is connected in series with the second pipeline (R2); the secondary side of the plate heat exchanger (4) is connected in series with the cooling tower (6) through a sixth pipeline (R6), and the cooling tower (6) and the plate heat exchanger (4) form a closed loop; The second medium stored in the cooling tower (6) flows along the sixth pipeline (R6). The second medium flows to the plate heat exchanger (4), and the second medium on the secondary side of the plate heat exchanger (4) absorbs the heat of the first medium on the primary side of the plate heat exchanger (4). After absorbing the heat, the second medium flows back to the cooling tower (6) along the sixth pipeline (R6) from the secondary side to form a cooling cycle; A circulation pump (09), a second electric control valve (10) and a fifth flowmeter (F07) are sequentially arranged on the annular closed loop formed by the cooling tower (6) and the plate heat exchanger (4) to control the flow rate of the second medium in the cooling system (D).

6. A test method for a mechanical seal used in a nuclear main pump, implemented by using the test loop for the mechanical seal used in a nuclear main pump as described in claim 5. The test method can perform a normal operation test, and the test process is as follows: Step S1: Open the fourth electric control valve (05) and close the third electric control valve (06), so that the water tank (1) is connected to the mechanical seal tooling (3) through the main pipeline (R0) and the first pipeline (R1) and disconnected from the electric heating tank (2). Step S2: Fill the entire test loop with the first medium, and the pressure source (501) injects compressed air into the expansion tank (5) to provide static pressure to the test loop. Step S3: Start the plunger pump (01). When the minimum pressure required for starting the mechanical seal tooling (3) is reached, start the mechanical seal tooling (3) to operate. Step S4: Adjust the opening degrees of the second pneumatic control valve (03) and the first pneumatic control valve (04) to meet the operating condition requirements for the normal operation of the mechanical seal tooling (3). Step S5: The first medium in the water tank (1) flows into the mechanical seal tooling (3) through the main pipeline (R0) and the first pipeline (R1), and flows back to the water tank (1) through the reflux outlet. During the test process, observe the leakage amounts of the first measuring cup (F02) and the second measuring cup (F03), that is, observe the low-pressure leakage amount and the balance seal leakage amount of the mechanical seal tooling (3) respectively. Step S6: Shut down the mechanical seal tooling (3) and the plunger pump (01) after the test ends. In step S3, the minimum pressure for starting the mechanical seal tooling (3) is ≥ 2 MPa. In step S5, the temperature of the injected first medium is controlled between 25 and 55 °C.

7. The test method for the mechanical seal of the test nuclear main pump according to claim 6, characterized in that, The test method can also be switched from a normal operation test to a thermal shock test, and the thermal shock test process is as follows: Step S1: Use the electric heating tank (2) to heat up the stored third medium. Step S2: When the third medium is heated up to the thermal shock required temperature, close the fourth electric control valve (05) and open the third electric control valve (06), so that the electric heating tank (2) is connected to the mechanical seal tooling (3) through the main pipeline (R0) and the first pipeline (R1) and disconnected from the water tank (1). Step S3: Keep the plunger pump (01) and the mechanical seal tooling (3) in the open and operating states. The third medium enters the mechanical seal tooling (3) through the main pipeline (R0) and the first pipeline (R1), and flows back to the electric heating tank (2) through the reflux outlet. The temperature inside the mechanical seal tooling (3) will instantaneously increase due to the inflow of the third medium, forming a thermal shock. Step S4: Observe the leakage amounts of the first measuring cup (F02) and the second measuring cup (F03) during the thermal shock test process, that is, observe the low-pressure leakage amount and the balance seal leakage amount of the mechanical seal tooling (3) respectively. Step S5: Shut down the mechanical seal tooling (3) and the plunger pump (01) after the test ends.

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