Method for testing fatigue life of static sealing element in high-pressure and low-temperature environment

Abstract

The invention relates to the technical field of material analysis and testing, in particular to the field of IPC G01N3 / 08, and more particularly relates to a method for testing the fatigue life of a static sealing element in a high-pressure and low-temperature environment. Comprising the following steps: step 1, carrying out pressure relief tests on the sealing element at different temperatures and under different pressures; step 2, carrying out a variable-temperature voltage-withstanding test; 3, replacing the sealing element, and carrying out a first temperature rise pulse pressure resistance test; 4, carrying out a cooling pulse withstand voltage test; step 5, carrying out a second heating pulse withstand voltage test; 6, carrying out a low-temperature pulse withstand voltage test; 7, measuring the low-temperature performance of the sealing element before and after the experiment; the steps 1-6 respectively comprise a step of continuously monitoring pressure relief, the environment temperature and the real temperature of the pulse liquid are monitored at the same time, and if pressure relief occurs in any step during the monitoring period, the test is ended, and the subsequent steps are not carried out any more. According to the method, the fatigue life of the sealing element can be evaluated in a low-temperature environment, so that the reliability requirement of large complete machine equipment is met.

Description

Technical Field

[0001] The present invention relates to the technical field of material analysis and testing, in particular to the field of IPC G01N3 / 08, and more specifically to a fatigue life test method for static seals under a high-pressure and low-temperature environment. Background Art

[0002] The working environment of large-scale mining engineering machinery equipment is complex. It needs to work normally in extremely cold environments (as low as -50℃). At the same time, it also needs to meet the requirements of the whole machine being in high temperature conditions during high temperature seasons and after continuous work. In order to ensure that the seals do not leak at low temperatures and the whole machine meets the specific life after high temperature work, it is necessary to develop a set of test methods based on actual working conditions to ensure that the fatigue life of static seals in high pressure and low temperature environments meets the working requirements of the whole machine.

[0003] For rubber seals, the aging performance of rubber materials is usually studied: For example, GB / T20028-2005 stipulates that a 50% change in physical properties after rubber aging is the critical value of seal failure, and CN201611174320 proposes that the compression permanent deformation rate CS ≥ 40% is used as the critical standard for seal failure. Chinese invention patents CN110765692A and CN113295400A obtain the aging law of rubber materials based on the Arrhenius equation and the aging kinetics equation, and propose a life prediction method based on aging indicators. However, the evaluation indicators used in this type of method often have no direct relationship with long-term sealing performance and are all empirical. The method for determining the relevant critical life value has not been clearly stated and is not universal. Summary of the invention

[0004] A first aspect of the present invention provides a method for testing fatigue life of a static seal under a high pressure and low temperature environment, comprising the following steps:

[0005] Step 1: Perform pressure relief tests on the seal at different temperatures and pressures;

[0006] Step 2: Perform variable temperature and voltage withstand test;

[0007] Step 3: Replace the seal and perform the first temperature rise pulse withstand voltage test;

[0008] Step 4: Perform a temperature drop pulse withstand voltage test;

[0009] Step 5: Perform the second temperature rise pulse withstand voltage test;

[0010] Step 6: Perform low temperature pulse withstand voltage test;

[0011] Step 7: Determine the low temperature performance of the seal before and after the experiment;

[0012] The steps 1 to 6 all include the step of continuously monitoring the pressure relief, while monitoring the ambient temperature and the real temperature of the pulsed liquid. If pressure relief occurs in any step during the monitoring period, the test is terminated and the subsequent steps are not performed.

[0013] The low temperature performance can be characterized by at least one of the following parameters: TR 10 , low temperature brittle temperature, glass transition temperature.

[0014] The TR 10 The measurement is carried out according to GB / T7758 "Determination of low temperature properties of vulcanized rubber - Temperature retraction method (TR test)".

[0015] In step 1, the seals are from the same batch, the number of seals tested is no less than 4, and the tests are performed simultaneously.

[0016] The applicant has discovered that by first subjecting the seal to a pressure relief test at different temperatures and pressures and then to a variable temperature and pressure test, this test sequence can quickly identify seals that do not reach their fatigue life, shorten the test process, and reduce test costs. The seal may be placed in a high-pressure environment for a long time, so that the air tightness and mechanical strength of the overall structure of the seal are subjected to the dual impact of pressure and temperature, and then a variable temperature and pressure test is performed, which can further verify the life under extreme fatigue conditions.

[0017] The present application study found that replacing the seal before the step 3 test and performing the subsequent steps 3-6 tests can improve the accuracy of the test. It may be that after the step 2 test, the seal is close to the extreme life edge. Performing the pulse withstand voltage test may cause the experiment to end prematurely, making it impossible to test whether the specific service life can be met during the whole machine test.

[0018] The number of seals that pass the test is not less than 75%, and TR 10 The test is considered passed if the temperature is less than 10℃.

[0019] The temperature points in step 1 are selected between -60°C and 130°C, the number of the temperature points is 6 to 12, and the pressure points are selected between 5 and 50 MPa, the number of the pressure points is 1 to 7.

[0020] Preferably, the temperature points in step 1 are selected from -50°C to 120°C, the number of temperature points is 6 to 12, and the pressure points are selected from 5 to 50 MPa, the number of pressure points is 1 to 7.

[0021] Preferably, the temperature point in step 1 is selected from the following values: -50°C, -40°C, -30°C, -20°C, 25°C, 95°C, 100°C, 110°C, 120°C, -45°C, -35°C, -25°C, -15°C, 20°C, 30°C, 35°C, 90°C, 105°C, 115°C, 125°C, 130°C.

[0022] Further preferably, the temperature points in step 1 are: -50°C, -40°C, -30°C, -20°C, 25°C, 95°C, 100°C, 110°C, 120°C.

[0023] Preferably, the pressure point includes at least one between 30-40 MPa, and preferably, the pressure point includes at least 35 MPa.

[0024] The pressure point also includes at least one of the following values: 10MPa, 15MPa, 20MPa, 25MPa, 28MPa.

[0025] Further preferably, the pressure points are 10 MPa, 15 MPa, 20 MPa, 25 MPa, and 35 MPa.

[0026] The step 2 comprises: firstly cooling the temperature from 5 to 35° C. to -40 to -60° C., then pressurizing to 20 to 50 MPa, and heating to 80 to 110° C. during the pressure-maintaining process.

[0027] Preferably, the step 2 comprises: firstly cooling from 15 to 35° C. to -45 to -60° C., then pressurizing to 30 to 50 MPa, and heating to 90 to 110° C. during the pressure-maintaining process.

[0028] More preferably, the temperature is first lowered from 15 to 35° C. to -45 to -55° C., then pressurized to 30 to 40 MPa, and the temperature is raised to 90 to 100° C. during the pressure-maintaining process.

[0029] More preferably, the step 2 includes: firstly cooling from 25°C to -50°C, then pressurizing to 35MPa, and heating to 95°C during the pressure-maintaining process.

[0030] The pulses in steps 3 to 6 include: firstly increasing the pressure from 1 to 5 MPa to 20 to 50 MPa within 0.1 to 1 s, and then decreasing the pressure from 20 to 50 MPa to 1 to 5 MPa within 0.1 to 1 s, and completing the pressure increase and pressure decrease is one pulse.

[0031] Preferably, the pulses in steps 3 to 6 include: first increasing the pressure from 1.5 to 5 MPa to 30 to 50 MPa within 0.3 to 1 s, and then decreasing the pressure from 30 to 50 MPa to 1.5 to 5 MPa within 0.3 to 1 s.

[0032] Further preferably, the pulses in steps 3 to 6 include: first increasing the pressure from 1.5 to 3 MPa to 30 to 40 MPa within 0.3 to 0.8 s, and then decreasing the pressure from 30 to 40 MPa to 1.5 to 3 MPa within 0.3 to 0.8 s.

[0033] More preferably, the pulses in steps 3 to 6 all include: first increasing the pressure from 2 MPa to 35 MPa within 0.5 s, and then decreasing the pressure from 35 MPa to 2 MPa within 0.5 s.

[0034] The step 3 comprises: firstly cooling from 5 to 35°C to -40 to -60°C, then heating to 80 to 110°C, and keeping warm; applying pulses during the heating and keeping warm process, and the number of times of applying pulses is 60,000-120,000 times.

[0035] Preferably, the step 3 comprises: first cooling from 15 to 35°C to -45 to -60°C, then heating to 90 to 110°C for heat preservation; applying pulses during the heating and heat preservation process, and the number of pulses applied is 80,000-120,000 times.

[0036] Further preferably, the step 3 comprises: first cooling from 15 to 30°C to -45 to -55°C, then heating to 90 to 100°C for heat preservation; applying pulses during the heating and heat preservation process, and the number of pulses applied is 80,000-105,000 times.

[0037] More preferably, the step 3 comprises: first cooling from 25°C to -50°C, then heating to 95°C and keeping warm; applying pulses during the heating and keeping warm process, and the number of times the pulses are applied is 93700 times.

[0038] The step 4 comprises: firstly cooling from 80 to 110° C. to -40 to -60° C., and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 4 is 1800-5400 times.

[0039] Preferably, the step 4 comprises: first cooling from 90 to 110° C. to -45 to -60° C., and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 4 is 2500-5400 times.

[0040] Further preferably, the step 4 comprises: first cooling from 90 to 100° C. to -45 to -55° C., and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 4 is 2500-4000 times.

[0041] More preferably, the step 4 comprises: first cooling from 95°C to -50°C, and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 4 is 3600 times.

[0042] The step 5 comprises: first heating from -40 to -60°C to 80 to 110°C, and then keeping the temperature; applying pulses during the heating and keeping temperature, and the number of pulses applied in the step 5 is 1800-5400 times.

[0043] Preferably, the step 5 comprises: first heating from -45 to -60°C to 90 to 110°C, and then keeping the temperature; applying pulses during the heating and keeping temperature, and the number of pulses applied in the step 5 is 2500-5400 times.

[0044] Further preferably, the step 5 comprises: first heating from -45 to -55°C to 90 to 100°C, and then keeping warm; applying pulses during the heating and keeping warm, and the number of pulses applied in the step 5 is 2500-4000 times.

[0045] More preferably, the step 5 comprises: first heating from -50°C to 95°C, and then keeping warm; applying pulses during the heating and keeping warm process, and the number of pulses applied in the step 5 is 3600 times.

[0046] The step 6 comprises: firstly cooling from 5 to 35° C. to -40 to -60° C., and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 6 is 5400-9600 times.

[0047] Preferably, the step 6 comprises: first cooling from 15 to 35° C. to -45 to -60° C., and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 6 is 6000-9600 times.

[0048] Further preferably, the step 6 comprises: first cooling from 15 to 30° C. to -45 to -55° C., and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 6 is 6000-8000 times.

[0049] More preferably, the step 6 comprises: first cooling from 25°C to -50°C, and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 6 is 7200 times.

[0050] The research of this application found that the number of pulses applied in step 3 is 80,000-120,000 times, the number of pulses applied in step 4 is 1,800-5,400 times, the number of pulses applied in step 5 is 1,800-5,400 times, and the number of pulses applied in step 6 is 5,400-9,600 times, which can accurately verify that the working life can reach 15,000 hours. At the same time, the end of the test caused by any step can also provide targeted improvement plans for the seals, which may involve a measurement method for converting the equilibrium temperature to the ambient temperature. The operating equilibrium temperature can be calculated according to the ambient temperature. If the ambient temperature becomes lower, the corresponding thermal equilibrium temperature also becomes lower. The temperature has a great influence on the life. The lower the temperature, the smaller the influence. Therefore, a specific ambient temperature and pulse are selected to determine the thermal equilibrium temperature and pulse for testing. At the same time, the specific pulse will not cause the seal to be at the performance limit for a long time, and it can be durable for a long time to ensure the accuracy of the test.

[0051] The rate of cooling or heating in steps 3-6 is 0.5-5°C / min.

[0052] Preferably, the cooling or heating rate in steps 3-6 is 0.5 to 3° C. / min.

[0053] Further preferably, the rate of cooling or heating in steps 3-6 is 1 to 3°C / min.

[0054] More preferably, the cooling or heating rate in steps 3-6 is 2°C / min.

[0055] The applicant has found that the cooling or heating rate in steps 3-6 is 0.5-5°C / min, which can shorten the test time. If the heating / cooling rate is too fast, it will damage the machine; if it is too slow, the efficiency will be low. Further research has found that the cooling or heating rate in steps 3-6 is 0.5-3°C / min, which can further simulate the temperature change rate under actual working conditions, maintain the thermal equilibrium temperature, and further accurately detect the fatigue performance of the seal.

[0056] Beneficial Effects

[0057] 1. First, conduct a pressure relief test on the seal at different temperatures and pressures, and then conduct a variable temperature pressure test. This test sequence can evaluate the fatigue life of the seal in a low temperature environment, and can quickly determine the seals that cannot reach the fatigue life, shorten the test process, reduce the test cost, and meet the reliability requirements of large-scale complete equipment.

[0058] 2. Replace the seal before testing in step 3 and perform subsequent tests in steps 3-6 to improve the accuracy of the test.

[0059] 3. The number of pulses applied in step 3 is 80,000-120,000 times, the number of pulses applied in step 4 is 1,800-5,400 times, the number of pulses applied in step 5 is 1,800-5,400 times, and the number of pulses applied in step 6 is 5,400-9,600 times, which can accurately verify that the working life can reach 15,000 hours.

[0060] 4. The cooling or heating rate in steps 3-6 is 0.5-5°C / min, which can shorten the test time.

[0061] 5. The test method of this application is simple. In the 6-step test process, by analyzing the test results, a reference basis can be provided for the seal improvement plan.

[0062] 6. This application sets the pressure relief value and TR 10 The dual judgment criteria can effectively improve the test accuracy. DETAILED DESCRIPTION

[0063] Example 1

[0064] A static seal fatigue life test method under high pressure and low temperature environment, seal model: NBR90, test according to the following steps:

[0065] Step 1: Install 4 seals on 4 test heads respectively and connect them to the pulse test bench. Carry out pressure holding tests for 10 minutes at (-50℃, 35MPa), (-40℃, 35MPa), (-30℃, 35MPa), (-20℃, 35MPa), (25℃, 35MPa), (95℃, 35MPa), (100℃, 35MPa), (110℃, 35MPa), and (120℃, 35MPa) in turn without pressure relief.

[0066] Step 2: The seal is first cooled from 25°C to -50°C, then pressurized to 35MPa, and heated to 95°C during the pressure holding process. During the test, one seal was depressurized when the temperature was raised to -27.3°C.

[0067] Step 3: Replace 3 seals, first cool down from 25°C to -50°C, then heat up to 95°C for heat preservation; apply pulses during the heating and heat preservation process, the number of pulses applied is 93700 times, and there is no pressure relief during the test.

[0068] Step 4: first cool the seal from 95°C to -50°C, and then keep it warm; during the keeping warm process, pulses are applied. The number of pulses applied in step 4 is 3600 times, and there is no pressure relief during the test.

[0069] Step 5: The seal is first heated from -50°C to 95°C and then kept warm; pulses are applied during the heating and keeping warm process. The number of pulses applied in step 5 is 3600 times, and there is no pressure relief during the test.

[0070] Step 6: first cool the seal from 25°C to -50°C, and then keep it warm; during the keeping warm process, pulses are applied, and the number of pulses applied in step 6 is 7200 times, and there is no pressure relief during the test;

[0071] Step 7: Determine the TR of the seal before and after the experiment 10 (The temperature corresponding to 10% shrinkage rate) is less than 10℃, and the product is considered qualified.

[0072] Example 2

[0073] A static seal fatigue life test method under high pressure and low temperature environment, seal model: NBR90, test according to the following steps:

[0074] Step 1: Install 4 seals on 4 test heads respectively and connect them to the pulse test bench. Carry out pressure holding tests for 10 minutes at (-50℃, 35MPa), (-40℃, 35MPa), (-30℃, 35MPa), (-20℃, 35MPa), (25℃, 35MPa), (95℃, 35MPa), (100℃, 35MPa), (110℃, 35MPa), and (120℃, 35MPa) in turn without pressure relief.

[0075] Step 2: The seal is first cooled from 25°C to -50°C, then pressurized to 35MPa, and heated to 95°C during the pressure holding process. During the test, one seal was depressurized when the temperature was raised to 95°C.

[0076] Step 3: Replace 3 seals, first cool down from 25°C to -50°C, then heat up to 95°C for heat preservation; apply pulses during the heating and heat preservation process, the number of pulses applied is 93700 times, and there is no pressure relief during the test.

[0077] Step 4: first cool the seal from 95°C to -50°C, and then keep it warm; during the keeping warm process, pulses are applied. The number of pulses applied in step 4 is 3600 times, and there is no pressure relief during the test.

[0078] Step 5: The seal is first heated from -50°C to 95°C and then kept warm; pulses are applied during the heating and keeping warm process. The number of pulses applied in step 5 is 3600 times, and there is no pressure relief during the test.

[0079] Step 6: first cool the seal from 25°C to -50°C, and then keep it warm; during the keeping warm process, pulses are applied, and the number of pulses applied in step 6 is 7200 times, and there is no pressure relief during the test;

[0080] Step 7: Determine the TR of the seal before and after the experiment 10 (The temperature corresponding to 10% shrinkage rate) is less than 10℃, and the product is considered qualified.

[0081] Example 3

[0082] A static seal fatigue life test method under high pressure and low temperature environment, seal model: NBR90, test according to the following steps:

[0083] Step 1: Install 4 seals on 4 test heads respectively and connect them to the pulse test bench. Carry out pressure holding tests for 10 minutes at (-50℃, 35MPa), (-40℃, 35MPa), (-30℃, 35MPa), (-20℃, 35MPa), (25℃, 35MPa), (95℃, 35MPa), (100℃, 35MPa), (110℃, 35MPa), and (120℃, 35MPa) in turn without pressure relief.

[0084] Step 2: first cool the seal from 25℃ to -50℃, then pressurize it to 35MPa, and raise the temperature to 95℃ during the pressure holding process. During the test, the four seals release pressure one after another when the temperature rises to -40~-30℃. At the end of the test, the product is judged to be unqualified.

[0085] Example 4

[0086] A static seal fatigue life test method under high pressure and low temperature environment, seal model: NBR90, test according to the following steps:

[0087] Step 1: Install 4 seals on 4 test heads respectively and connect them to the pulse test bench. Carry out pressure holding tests for 10 minutes at (-50℃, 35MPa), (-40℃, 35MPa), (-30℃, 35MPa), (-20℃, 35MPa), (25℃, 35MPa), (95℃, 35MPa), (100℃, 35MPa), (110℃, 35MPa), and (120℃, 35MPa) in turn without pressure relief.

[0088] Step 2: first cool the seal from 25℃ to -50℃, then pressurize it to 35MPa, and raise the temperature to 95℃ during the pressure holding process. During the test, the three seals release pressure successively when the temperature rises to 20.6℃, 27.8℃, and 95.1℃ respectively. At the end of the test, the product is judged to be unqualified.

[0089] Example 5

[0090] A static seal fatigue life test method under high pressure and low temperature environment, seal model: HNBR90, test according to the following steps:

[0091] Step 1: Install the four seals on four test heads respectively and connect them to the pulse test bench. All four seals release pressure during the pressure maintenance process (-50℃, 35MPa). The test is completed and the product is judged to be unqualified.

[0092] Example 6

[0093] A static seal fatigue life test method under high pressure and low temperature environment, seal model: NBR90, test according to the following steps:

[0094] Step 1: Install 4 seals on 4 test heads respectively and connect them to the pulse test bench. Carry out pressure holding tests for 10 minutes at (-50℃, 35MPa), (-40℃, 35MPa), (-30℃, 35MPa), (-20℃, 35MPa), (25℃, 35MPa), (95℃, 35MPa), (100℃, 35MPa), (110℃, 35MPa), and (120℃, 35MPa) in turn without pressure relief.

[0095] Step 2: first cool the seal from 25℃ to -50℃, then pressurize it to 35MPa, and raise the temperature to 95℃ during the pressure holding process. During the test, the four seals release pressure when the temperature rises to 86.3℃, 32.3℃, 91.3℃, and 89.2℃ respectively. The test is completed and the product is judged to be unqualified.

[0096] Example 7

[0097] A static seal fatigue life test method under high pressure and low temperature environment, seal model: NBR80, test according to the following steps:

[0098] Step 1: Install 4 seals on 4 test heads respectively and connect them to the pulse test bench. Carry out pressure holding tests for 10 minutes at (-50℃, 35MPa), (-40℃, 35MPa), (-30℃, 35MPa), (-20℃, 35MPa), (25℃, 35MPa), (95℃, 35MPa), (100℃, 35MPa), (110℃, 35MPa), and (120℃, 35MPa) in turn without pressure relief.

[0099] Step 2: first cool the seal from 25℃ to -50℃, then pressurize it to 35MPa, and raise the temperature to 95℃ during the pressure holding process. During the test, the two seals release pressure when the temperature rises to 86.2℃ and 64.2℃ respectively. At the end of the test, the product is judged to be unqualified.

[0100] Performance Testing Methods

[0101] The test results in the embodiment are recorded in Table 1, and then the seals of the same model and batch in the embodiment are selected for use on the machine, and the use time is recorded. If it reaches 15,000 hours, it is qualified, otherwise it is unqualified, and the results are recorded in Table 1.

[0102] Performance test data

[0103] Table 1

[0104] Example Test pass Is the machine qualified for use? Example 1 Failure Failure Example 2 Failure Failure Example 3 Failure Failure Example 4 qualified qualified Example 5 Failure Failure Example 6 qualified qualified Example 7 qualified qualified

Claims

1. A method for testing the fatigue life of static seals under high pressure and low temperature environment, characterized in that: The following steps are involved: Step 1: Perform pressure relief tests on the seal at different temperatures and pressures; Step 2: Perform variable temperature and voltage withstand test; Step 3: Replace the seal and perform the first temperature rise pulse withstand voltage test; Step 4: Perform a temperature drop pulse withstand voltage test; Step 5: Perform the second temperature rise pulse withstand voltage test; Step 6: Perform low temperature pulse withstand voltage test; Step 7: Determine the low temperature performance of the seal before and after the experiment; The steps 1 to 6 all include the step of continuously monitoring the pressure relief. If pressure relief occurs in any step during the monitoring period, the test is terminated and the subsequent steps are not performed.

2. The method for testing fatigue life of static seals under high pressure and low temperature environment according to claim 1, characterized in that: The pressure points in step 1 are selected from 5 to 50 MPa, and the number of pressure points is 1 to 7.

3. The method for testing fatigue life of static seals under high pressure and low temperature environment according to claim 2, characterized in that: The temperature points in step 1 are selected from between -60°C and 130°C, and the number of temperature points is 6 to 12.

4. The method for testing fatigue life of static seals under high pressure and low temperature environment according to claim 3, characterized in that: The step 2 comprises: firstly cooling the temperature from 5 to 35° C. to -40 to -60° C., then pressurizing to 20 to 50 MPa, and heating to 80 to 110° C. during the pressure-maintaining process.

5. The method for testing fatigue life of static seals under high pressure and low temperature environment according to claim 4, characterized in that: The pulses in steps 3 to 6 include: firstly increasing the pressure from 1 to 5 MPa to 20 to 50 MPa within 0.1 to 1 s, and then decreasing the pressure from 20 to 50 MPa to 1 to 5 MPa within 0.1 to 1 s, and completing the pressure increase and pressure decrease is one pulse.

6. The method for testing fatigue life of static seals under high pressure and low temperature environment according to claim 5, characterized in that: The step 3 comprises: firstly cooling from 5 to 35°C to -40 to -60°C, then heating to 80 to 110°C, and keeping warm; applying pulses during the heating and keeping warm process, and the number of times of applying pulses is 60,000-120,000 times.

7. The method for testing fatigue life of static seals under high pressure and low temperature environment according to claim 6, characterized in that: The step 4 comprises: firstly cooling from 80 to 110° C. to -40 to -60° C., and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 4 is 1800-5400 times.

8. The method for testing fatigue life of static seals under high pressure and low temperature environment according to claim 7, characterized in that: The step 5 comprises: first heating from -40 to -60°C to 80 to 110°C, and then keeping the temperature; applying pulses during the heating and keeping temperature, and the number of pulses applied in the step 5 is 1800-5400 times.

9. The method for testing fatigue life of static seals under high pressure and low temperature environment according to claim 8, characterized in that: The step 6 comprises: firstly cooling from 5 to 35° C. to -40 to -60° C., and then keeping warm; applying pulses during the keeping warm process, and the number of pulses applied in the step 6 is 5400-9600 times.

10. The method for testing fatigue life of static seals under high pressure and low temperature environment according to any one of claims 5 to 9, characterized in that: The rate of cooling or heating is 0.5-5°C / min.