GB/T 2423.23-1995 Environmental testing for electrical and electronic products Test Q: Sealing
Some standard content:
National Standard of the People's Republic of China
Environmental testing for electric and electronic products
Test Q: Sealing
Environmental testing
for electric and electronic productsTest Q: Sealing
1 Subject content and scope of application
GB/T 2423.23--1995
Replaces GB2423.23---82
GB 2424. 16--82
This standard specifies various sealing performance test methods. Tests Qa and Qc are rough inspections, observing bubbles emerging from the leak; test Qd is to observe the leakage of liquid under heating conditions, and tests Qk and Qm are to detect fine leaks with tracer gas; tests Qf and Q1 are to allow liquid to enter through the leak under pressurized conditions and then measure the performance changes. This standard is applicable to the testing of the sealing performance of various electric and electronic products, and also to the sealing performance testing of other sealing components. 2 Reference standards
GB2421 General rules for basic environmental testing procedures for electrical and electronic products GB4208 Classification of enclosure protection levels
3 Terms
3.1 Leak rate
The amount of dry gas at a given temperature flowing through the leak per unit time when the pressure difference on both sides of the leak is known. Note: When the international system of units is used, the leak rate is: Pa·m/s. In this standard, the derived units Pa·cm'/s and bar·cm\/s are used because they are closer to the magnitudes commonly used in industry. Here 1 Pa ~m\/s=10° Pa·cm\/s=10 bar · cm*/s3.2 Standard leak rate standard leak rate The leak rate under standard temperature and pressure difference conditions. For this standard, the standard temperature is 25℃; the standard pressure difference is 105Pa (1bar). 3.3 Measured leak rate (R) measured leak rate The leak rate of a given device measured under specified conditions using a specified test gas. Note: ① Leak rate measurements are usually made with nitrogen as the test gas at a temperature of 25°C and a pressure difference of 10°Pa (1 bar). ② In order to compare the leak rate with that determined using other test methods, the measured leak rate must be converted to an equivalent standard leak rate. 3.4 Equivalent standard leak rate (L) The standard leak rate of a given device when air is used as the test gas. 3.5 Time constant of leakage (0) The time required for the pressure on both sides of the leak to equalize, assuming that the rate of change of the pressure difference on both sides of the leak remains constant. For this test, the time constant is equal to the ratio of the internal volume of the sample to the equivalent standard leak rate. 3.6 Gross leak
Any leak with an equivalent standard leak rate greater than 1Pa·cm/s (10-5bar·cm/s). Approved by the State Administration of Technical Supervision on January 27, 1995 and implemented on August 1, 1995
3.7 Fine leak
GB/T2423.23-1995
Any leak with an equivalent standard leak rate of less than 1Pa·cm\/s (10\5bar·cn°/s). 3.8 Virtual leak
Leakage caused by the slow release of gas absorbed, adsorbed or trapped by the test sample. 3.9 Leak meter
Equipment consisting of a hand-held probe and a meter. The probe is used to collect mixed gas samples, and the meter gives the concentration of a predetermined type of gas in the sample.
3.10 Volume of measurement (Vm) Volume between the sealed cover and the sample where the leak is collected. Note: The concentration of the tracer gas in this volume is very low, and the cover generally does not need to be tightly sealed. 3.11 Leak detector
Equipment consisting of a handheld probe and a sensitive device. The probe is used to collect mixed gas samples, and the sensitive device emits an audible or visible signal when the predetermined gas concentration reaches the set reading value. 3.12 Probing
The action of slowly moving the leak detector probe along the sample to find the leaking part. 4 Overview
Poor sealing of electrical and electronic products will cause gas and liquid leakage of the product, thereby reducing its electrical performance, and sometimes cause corrosion of itself and nearby products, and even damage the product and lose all functions. Due to different use conditions, the sealing requirements for products are also different. In order to meet different sealing requirements, different sealing test methods have been formulated. The series branches of all sealing tests are shown in Figure 1: Sealing test
External detection
Container sealing
Bushing, mandrel
Air tightness
Gas leakage
(bubble test)
Liquid leakage
Container sealing
Tracer gas
Mass spectrometer
Test Q is divided into the following two groups according to the different detection methods used, namely: a.
Tracer gas
Internal pre-pressurization
Internal detection
Pressure diffusion
Internal detection: measuring the changes in electrical properties caused by the test medium (liquid or gas) entering the test sample through the leak; GB/T 2423.23--1995
External detection: by observing the test medium escaping through the leak. The two internal inspection tests Qf and Q1 are very similar and are very effective for some components, such as plastic film capacitors, but for such components, their electrical properties may only become significant after a long time (such as after the test), so this method is not recommended.
External inspection tests can be further divided according to their application. Qa is a bubble test, which is used to determine the airtightness of bushings, mandrels and gaskets. Other tests Qc, Qd, Qk and Qm are used to determine the leakage of containers (metal shells, protective covers, etc.). Qc is a bubble test, which includes methods with different sensitivities (leakage rate not less than 1Pa·cm\/s). Tests Qk and Qm are the most sensitive methods in this series of tests. Their sensitivity ranges from 1Pa·cm/s (10-5barcm/s) to about 10-'Pa·cm2/s (10-11bar·cm\/s). Test Qd is a liquid leakage test, which is suitable for test samples filled with liquid during manufacturing or solid fillers that can become liquid at the test temperature. Electrical and electronic products can be tested for protection against various forms of water or solid intrusion according to the requirements of GB4208. In GB4208, the degree of protection is determined by various tests and marked with numbers as shown in Table 1 and Table 2: Table 1 Protection level indicated by the first characteristic number Protection level
First characteristic number
Second characteristic number
No protection
Protection against solid objects larger than 50mm
Protection against solid objects larger than 12mm
Protection against solid objects larger than 2.5mm
Protection against solid objects larger than 1.0mm
No special protection
Objects with large surfaces, such as hands (but not protection against intentional contact) and solid objects with a diameter larger than 50mm
Fingers or similar objects with a length not exceeding 80mm, and solid objects with a diameter larger than 12mm
Tools, wires, etc. with a diameter or thickness larger than 2.5mm, and solid objects with a diameter larger than 2.5 mm solid objects
Wires or belts with a thickness greater than 1.0mm, and solid objects with a diameter greater than 1.0mm
Dust cannot be completely prevented from entering, but the amount of dust entering will not affect the normal operation of the equipment
No dust entry
Table 2 Protection level indicated by the second characteristic numeral Protection level
No protection
No special protection
Dripping water (vertically dripping) should have no harmful effect
Second characteristic numeral
GB/T 2423.23-1995
Continued Table 2
Protection level
Protect against dripping water when tilted upward by 15°
Protect against spraying water
Protect against splashing water
Protect against spraying water
Protect against huge waves
Protect against immersion
Protect against repeated immersion
5 Test Qa: Bushing, spindle and gasket seal 5.1 Purpose
Water dripping from the housing when it is tilted at any angle up to 15° from its normal position shall have no harmful effect
Water falling from the vertical at any angle up to 60° from the vertical position shall have no harmful effect
Water splashing against the housing from any direction shall have no harmful effect Water ejected from the nozzle against the housing from any direction shall have no harmful effect Projectile water from large waves or strong jets shall not enter the housing in such quantities as to be harmful to the equipment
When the housing is flooded with water at a specified pressure and for a specified time, the water entering shall not endanger the equipment
The equipment is suitable for continuous immersion in water specified by the manufacturer Note: Normally this means that the equipment is gas-tight. However, for some types of equipment it may mean that water may enter without causing any harmful effect Determine the sealing performance of bushings, spindles, gaskets and similar parts. Note: For this test, two types of seals will be considered: Type A: In the direction specified in the relevant specification, the pressure applied is 100kPa (10N/cm2) ~ 110kPa (11N/cm2). Type B: In all directions, the pressure applied is 100kPa (10N/cm2) ~ 110kPa (11N/cm\). 5.2 Scope
This test can be used to check for gross leaks.
5.3 Description
The test sample is installed on the lid of the pressurized test chamber immersed in the liquid. If the sample leaks, the air escaping through the leak is collected. The amount of air leakage is expressed as the amount of air collected per unit time. The corresponding test equipment is shown in Appendix A (Supplement). 5.4 Initial test
Not required.
5.5 Conditional test
5.5.1 Unless otherwise specified, the air pressure difference specified below shall be applied to each seal or to a group of assembled seals at the same time. Type A: The pressure applied in the direction specified in the relevant specifications is 100kPa (10N/cm2) ~ 110kPa (11N/cm\); Type B: The pressure applied in all directions is 100kPa (10N/cm2) ~ 10kPa (11N/cm\); where higher pressure is required, the pressure should be 340kPa (34N/cm2) ~ 360kPa (36N/cm\). Note: The test equipment described in Appendix A may not be suitable for these higher pressures. 5.5.2 Type B seals should be tested statically and during mechanical operation in accordance with the relevant specifications. 244
5.6 Final inspection
GB/T 2423.23--1995
The leakage rate should be measured. The limit value should be specified in the relevant specifications. 5.7 Details to be given in the relevant specifications
When this test is included in the relevant specifications, specific provisions should be made for the following items: pressure requirements (Clause 5.5.1);
Direction of applying the pressure difference (Clause 5.5.1);
Mechanical operation of the conditional test (Clause 5.5.2); c.
Leakage rate requirements (Clause 5.6).
6 Test Qc: Sealing of containers (leakage)
6.1 Purpose
To determine the sealing performance of test samples containing gas-filled spaces (such as test samples that are not completely filled with filler). 6.2 Scope
Depending on the method selected, this test can be used to verify leakage rates greater than 100, 10 or 1 Pa·cm\/s (10-3, 10-4 or 10\5bar·cm/s). Test methods 1 or 3 are applicable only to test specimens which have the full reduction or increase of pressure required to resist immersion without deformation or permanent physical damage (Chapters B1, B2, B3). Test method 2 is applicable to test specimens which are subjected to significant pressure differentials due to heat when operating at the maximum ambient temperature. 6.3 Explanation
The test specimen is flooded in a suitable liquid and, under controlled conditions, is inspected for gross leaks by observing bubbles released from the surface of the test specimen (Chapter B5).
Use one of the following test methods to produce a positive pressure inside the test specimen. 6.3.1 Test method 1
The test is carried out in a vacuum, thereby increasing the pressure differential across the seal of the test specimen. 6.3.2 Test method 2
The test specimen is immersed in a test liquid maintained at an elevated temperature (Chapter B10). 6.3.3 Test method 3
The specimen is first flooded in a liquid having a boiling point lower than the test temperature and then immersed in the test liquid. 6.4Qc Test Method 1
The test is conducted in a vacuum, thereby increasing the pressure difference on both sides of the seal of the test sample. 6.4.1 The test chamber with the liquid tank required for this test shall be capable of evacuating the vacuum, and the tank shall contain sufficient liquid to immerse the uppermost end of the shell or seal of the test sample to a depth of less than 10 mm. The temperature of the test liquid (Chapter B8) shall be maintained between 15 and 35°C, and the liquid tank shall be capable of draining or removing the test sample from the liquid before the vacuum is broken. 6.4.2 The test sample is immersed in the test liquid with the sealing surface facing upward, and then the air pressure in the test chamber is reduced to 1 kPa or other values specified in the relevant specifications within one minute. If no failure is observed (see 6.4.4), this air pressure is maintained for a few minutes or other duration specified in the relevant specifications (see Chapter B9). 6.4.3 For test samples with more than one sealing surface, each sealing surface shall be tested in turn in the upward position according to 6.4.2 (see Chapter B4).
6.4.4 The failure criterion for this test is usually the appearance of obvious continuous bubbles, two or more large bubbles, or attached bubbles that gradually increase in size at any time during the test duration (see Chapters B6 and B7). 6.5Qc Test Method 2
This is achieved by immersion in a test liquid maintained at an elevated temperature (see Chapter B10). 6.5.1 The test tank should contain enough liquid to allow the uppermost end of the shell or seal of the test sample to be submerged to a depth of less than 10 mm.
GB/T 2423.23-1995
6.5.2 The liquid temperature should be maintained at 1 to 5°C above the highest working environment temperature of the test sample or at a temperature specified in the relevant specifications. 6.5.3 Immerse the test sample at 15 to 35°C with its sealing surface facing up in the test liquid (see Chapter B11). The immersion time shall be at least 10 minutes or as specified in the relevant specifications (see Chapter B3). 6.5.4 For test specimens with more than one sealing surface, each sealing surface shall be tested in turn in the upward position according to 6.5.3 (see Chapter B4).
6.5.5 The failure criterion for this test is usually the presence of obvious continuous bubbles, two or more large bubbles, or attached bubbles that gradually increase in size at any time during the test duration (see Chapters B6 and B7). 6.6Qc Test Method-3
This is achieved by immersing in a liquid with a boiling point lower than the test temperature and then immersing in a test liquid with a higher boiling point.
This method consists of two steps:
6.6.1 Step 1
Step 1 shall be carried out at room temperature.
The test specimen is sealed in a vacuum/pressurized container, the pressure is reduced to 100 Pa and maintained for 1 hour, and then the container is filled with liquid (see Chapters B12 and B13) without breaking the vacuum until the test specimen is submerged. The test sample is then pressurized under the following conditions (see Table 3). Table 3
Volume of cavity
≤0.1cm2
Minimum pressure (absolute value)
600kPa
300kPa
Immersion time
After the immersion time has expired, the pressure is released and the test sample is kept in the liquid. Before proceeding to the second step (Chapters B14 and B15), the test sample should be removed from the liquid tank and allowed to dry at room temperature for 3±1min or other time specified in the relevant specification.
6.6.2 Step 2
If not otherwise specified, method 2 with a test temperature of 125±5℃ is applicable. If not otherwise specified in the relevant specification, the test sample should be observed for 30s from the time of immersion.
6.7 Details to be given in the relevant specifications
When this test is included in the relevant specifications, the following items should be specified: a.
Test method (6.3, 6.4, 6.56.6); recommended liquid (Chapters B8 and B11);
Test method 1: pressure and time (if different from 6.4.2), test method 2: liquid temperature (if different from 6.5.2); test method 2: duration of flooding (if different from 6.5.3); drying time (if not 3 minutes) (6.6.1), temperature of step 2 of test method 3 (if not 125°C) (6.6.2). Test Qd: Sealing of container (leakage)
7.1
Determine the sealing performance of the liquid-filled test sample. Note: This test is also applicable to test samples whose filling is solid at room temperature but liquid at the test temperature. 246
7.2 Scope
GB/T2423.231995
This test can be used to test test samples with a leakage rate equivalent to air greater than 1Pa·cm\/s. The sensitivity of the test method depends on the kinematic viscosity of the liquid at the test temperature and the leak detection technology used. 7.3 Description
This test is used to test test samples that may leak when the temperature is slightly higher than the maximum operating temperature of the test sample. 7.4 Severity level
The severity level is determined by the time kept at the test temperature. The relevant specifications should select the applicable severity level from the following times: 10 min;
48h.
7.5 Pretreatment
The test sample should be cleaned (remove oil stains) to clearly distinguish the leaking liquid from other substances. 7.6 Initial test
Not required.
7.7 Condition test
7.7.1 Place the test sample in an air circulation drying oven, and heat the oven temperature until the surface temperature of the test sample is 1 to 5°C above its highest working environment temperature. The test sample should be placed in the state most susceptible to leakage. 7.7.2 The test sample should be kept at the above temperature for the time specified by the severity level and then removed from the oven. 7.7.3 For test samples with more than one sealing surface, each sealing surface should be tested in the downward position in accordance with 7.7.1 and 7.7.2.
7.8 Final test
Inspect the liquid leakage with the naked eye. If there is no other provision in the relevant specifications, the test sample should have no leakage. The relevant specifications should specify the inspection method (see Chapter C2). 7.9 Details to be given in the relevant specifications
When this test is included in the relevant specifications, the following items shall be specified:
Test temperature (7.7.1);
b. Duration of the conditioning test (7.7.2); Method of checking for leakage (7.8).
8 Test Qf: Flooding
8.1 Purpose
Determine the watertightness of components, equipment or other products when flooded under specified pressure and time. 8.2 Description
Flood the test sample to a specified depth in a water container or place it in a high-pressure water tank. Apply a specified pressure to the test sample. After the conditioning test, check the water that has penetrated into the test sample and check its possible performance changes. 8.3 Initial inspection
Measure the electrical and mechanical properties and visually inspect the test sample as specified in the relevant specifications. All sealing components shall be inspected to determine that they are correctly installed. 8.4 Pretreatment
Pre-treat the test sample and the seal according to the relevant specifications. 8.5 Conditioning test
GB/T 2423.23---1995
8.5.1 The test sample shall be placed in the position specified in the relevant specifications and shall be completely immersed in the water container or high-pressure water tank. If the relevant specifications do not specify otherwise, dehumidifying water may be used. Note: Usually a wetting agent is added to the water.
8.5.2 According to the relevant specifications, the test sample shall be able to withstand the water level value or the corresponding pressure difference value given in Table 4 - When a liquid tank is used, the specified water level shall be measured from the highest point of the test sample. When a high-pressure water tank is used, the water pressure shall be adjusted to the pressure difference specified in Table 4. Table 4
8.5.3 The relevant specifications shall specify the duration, and the preferred values are 30min, 2h, and 24h. Corresponding pressure difference (at 25℃)
8.5.4 The temperature of the sample and water is between 15 and 35℃. During the treatment process, the temperature difference between the sample and water should be as small as possible and should not be less than 5℃.
8.5.5 If there are no other provisions in the relevant specifications, the test sample should be in a non-working, disconnected state during the immersion period, and its movable parts should be in a static state.
8.6 Recovery
If there are no other provisions in the relevant specifications, the surface of the test sample should be wiped or blown with room temperature air to thoroughly dry it.
8.7 Final inspection
According to the relevant specifications, the test sample shall be inspected for water seepage, visually inspected, and measured for electrical and mechanical properties. 8.8 Details to be given in the relevant specification
When this test is included in the relevant specification, the following items shall be specified: a.
Initial inspection (Clause 8.3);
Preconditioning method (Clause 8.4);
Position state during conditioning test (Clause 8.5.1); Whether dehumidifying agent is used (Clause 8.5.1);
Water level or pressure difference (Clause 8.5.2);
Duration of conditioning test (Clause 8.5.3); Inspection of electrical and mechanical properties after recovery (Clause 8.7). 9 Test Qk: Tracer gas method using mass spectrometer 9.1 Purpose
To verify the quality of the hermetic package of the sample by measuring its leak rate using a tracer gas and a mass spectrometer. Nitrogen is the most commonly used tracer gas for mass spectrometers. For tests using this gas, see Appendix E1 (Supplement). 248
9.2 Scope
GB/T2423.23--1995
Test method 1 is mainly used for small volume samples (see Table 5). The surface of the sample should not absorb too much ammonia to affect the test results (such as fabrics, welding points, organic materials, paint, etc.) unless it is properly treated before detection. Test method 2 is used for samples that have been filled with a mixed gas containing a large amount of nitrogen during the manufacturing process or due to test requirements. Test method 3 (spray gun and gas mask method) is used for samples installed on bulkheads and flat plates. Note: This method should be used with caution because it is possible to release enough hydrogen into the room to interfere with the mass spectrometer and cause the test to be interrupted until the room is ventilated and the test can not be resumed. This method cannot be used in situations where the emission rate acceptance limit is specified. Grade (time constant) and test conditions (corresponding equivalent standard leak rate) Table 5 Severe
Immersion time
Immersion pressure
(absolute value)
Pa-105
(minimum)
9.3 Note
(8=2×101 s)
Measured leak rate
(maximum)R
Pa·cm'/s
(bar·cm\/s)
(2×105）
(5×10-5)
Grade 60h
(82×105 s)
Measured leak rate
(maximum)R
Pa·cm\/s
(bar -cm\/s)
Harshness level 600 hl
Harshness level 1000h
(82×10%s)
Measurement leakage rate
(max)R
Pa - cm'/s
(har cm\/s)
(10-8)
(10-7)
(5×10 6)
(10~5)
(10-30)
(10-9)
(10-8)
(5X10-7)
(10°5)
(6-4X106 s)
Equivalent standard leak rate L
Measured leak rate
(maximum)R
Pa· cm\/s
(barcm'/s)
(10-10)
(10-9)
(10-\)
Pacm\/s
(bar * cm'/s)
5×10-4
1.5×10-a
(5×10 -~
1. 5×10-B)
5×10-3
(5×108~
1.5×107)
5×102~
1.5×10-1||t t||(5×103~
1.5×106)
(5×10-6~
(5×10~6
1.5×10-5)
9.3.1 Test method 1 consists of the following steps: Place the test sample, which has been carefully cleaned and dried in advance, in a box containing a pressurized nitrogen mixture for pressurization, so that ammonia penetrates into the interior of the test sample cavity. After a given time, place the test sample in a test box, then evacuate the test box and connect it to a mass spectrometer, draw the hydrogen leaked from the test sample into the mass spectrometer, and measure its leakage. The measured nitrogen leakage rate is converted into an equivalent standard leakage rate by calculation, so as to compare the test samples of the same volume tested under different test conditions. If the time constant 0-PV/L (see Chapter D1) of the test sample is compared, then the comparison between test samples of different volumes is still valid.
9.3.2 Test Method 2 is the same as Method 1 except that the pressurized immersion is omitted. The test should normally be completed within 30 min after encapsulation. For large samples, a longer time will be required depending on the volume of the inner cavity and the thickness of the encapsulation (see E7.2). For small samples, the test should be carried out immediately after encapsulation (see E7.1 and 7.2).
This method is not suitable for general sealing tests, such as sealing tests performed after other environmental tests. 9.3.3 The pressure for filling and testing should be selected so that it corresponds to the maximum possible air pressure that the test sample may be subjected to without seal damage. 9.3.4 If no leakage is detected by this test, the test sample should also be subjected to Test Qc or an equivalent test. 9.3.5 Method 3 is to connect one side of the sample to the vacuum chamber connected to the mass spectrometer, and then cover the visible surface of the sample with a sealed cover filled with ammonia (method a) or use a fine nitrogen spray gun to blow (method b). Method a: If there is a leak, the nitrogen in the nitrogen cover will enter the vacuum chamber, and its size (but not its position) can be determined based on the reading of the mass spectrometer.
Method b: When the gun passes through the sealing defect, the instrument can detect nitrogen, and the location and size of the leak can be determined based on the reading of the mass spectrometer.
9.4Qk Test method 1
Test sample not filled with nitrogen during the manufacturing process. 9.4.1 Severity level
The severity level is determined by the minimum time constant required for use. The relevant specifications should select the appropriate level from Table 5. In the case where different severity levels must be specified, the relevant specifications should specify all relevant test parameters. See Appendix D (Supplement). 9.4.2 Pretreatment
Remove contamination from the test sample that may conceal leakage or absorb ammonia, such as grease, fingerprints, flux and paint. After cleaning, the test sample should be dried to remove traces of solvents, capillary condensation, etc. They may conceal existing leaks. The test should be carried out on the test sample without any external attachments that may capture ammonia.
Note: In order to optimize the pretreatment procedure, each technology used should be studied in advance. 9.4.3 Initial testing
Not required.
9.4.4 Test parameters
Table 5 shows the severity level and test method selected according to the relevant standards. The test parameters and the acceptable limits of the allowable measured leak rate R are given for different test sample internal cavity volumes.
9.4.5 Condition test
The test sample should be placed in a closed test chamber. When the maximum filling pressure specified in the relevant specifications does not exceed 200kPa (absolute value), the tester shall select one of the following procedures: a. Reduce the pressure in the chamber to an absolute value of about 0.1 to 1 kPa. b. Or purge the test chamber with ammonia (see Chapter E3). When the filling pressure required by the relevant specification is greater than 200 kPa, neither of the above two procedures is required. Unless otherwise specified, the test chamber shall be filled with a mixed gas with a minimum ammonia content of 95% and then pressurized to the time and pressure selected from Table 5. The pressure shall not exceed the maximum pressure specified in the relevant specification for this type of device (see Clause E8.4). NOTE: The filling time t and the measured leak rate R are interrelated with the filling pressure P, the severity level 0 and the equivalent standard leak rate L (see Table 5). In order to quickly convert between these interrelated parameters, a nomogram is given in Figure D1 and explained in Appendix D. 9.4.6 Recovery
After the test sample is removed from the pressurized container, it should be exposed to standard atmospheric conditions in order to remove the nitrogen adsorbed on the surface of the test sample and avoid unacceptable interference signals in the final measurement. The recovery time is limited by the provisions of 9.4.7 (see Chapters E5 and E6). Note: Dry air blowing can be used to accelerate recovery. 250
9.4.7 Final test
GB/T 2423.23—1995
The test sample should be transferred to a box connected to the leak detection system, and then the pressure in the box should be reduced to the range where the mass spectrometer can work normally. The measured nitrogen leak rate is then determined by comparing it with the calibrated standard leak. It should be less than the maximum value of the severity level specified in the relevant specifications. The severity level is selected from Table 5.
Unless actual experience has shown that a longer ventilation time is required to take into account the effect of removing adsorption, the measurement of the leak rate R should be completed within 30 minutes after being removed from the pressurized container.
Note: The effect of longer ventilation time can be estimated using the data given in Chapter D2. 9.4.8 Gross leaks
In addition to this test, the presence of gross leaks shall be checked by other appropriate methods as specified in the relevant specification. For example, the method described in the test QC (see Chapter E4).
9.5Qk Test Method 2
Test samples that have been filled with ammonia during the manufacturing process or the test require. 9.5.1 Preconditioning
The test sample shall contain a gas mixture with a nitrogen concentration greater than or equal to 25% calculated on the pressure. Regular checks shall be made to ensure that the gas mixture actually used contains the required ammonia concentration. If appropriate, the relevant specification shall give any necessary installation conditions. 9.5.2 Initial test
Not required.
9.5.3 Final test
Immediately after sealing and packaging, the test sample shall be transferred to a chamber connected to a mass spectrometer type leak detector and the pressure in the chamber shall be reduced to the range within which the mass spectrometer can operate normally. The measured leak rate R is determined by comparison with a calibrated standard leak rate. Except in special cases, the measurement shall be completed within 30 min after sealing (see E7.2).
The measured leak rate R is converted to the time constant 6 using the following formula: nVP
where: V.
the volume of the inner cavity of the test specimen, cm;
the actual concentration of ammonia in the gas mixture used, cm/m; the atmospheric pressure, 105 Pa;
the measured leak rate of ammonia, in Pa·cm\/s; the required time constant, s.
The relevant specification shall specify the minimum required time constant. Or the maximum acceptable equivalent standard leak rate, the recommended values for the time constant are 2×10° s and 2×10* s.
9.5.4 Gross leaks
In addition to this test, the presence of gross leaks shall be verified by other suitable methods as specified in the relevant specification, such as the method described in Test Qc (see E4).
9.6 Test method 3
Applies to samples mounted on a wall or on a plate. 9.6.1 Pretreatment
Clean the sample to remove all contaminants such as grease fingerprints, flux or paint that can easily block the leak. After cleaning, place the sample in an oven to dry to remove residual solvents, lint condensate, etc., which can also block the leak. 9.6.2 Initial measurementwww.bzxz.net
Isolate the chamber from the test port with a valve and evacuate the chamber. When the pressure drops to a low enough level to allow the mass spectrometer to operate normally, connect the chamber to the mass spectrometer.
GB/T 2423.23--1995
Note the background signal of the mass spectrometer without nitrogen injection. Check the mass spectrometer for normal function with a reference ammonia leak. 9.6.3 Test
Place the sample on the test port, open the isolation valve to evacuate, check that the vacuum should be able to maintain the normal operation of the mass spectrometer, and continue to evacuate until the background signal stabilizes at a level approximately consistent with the value measured previously. Method a: Cover the outside of the sample with a flexible outer cover or plastic cover filled with nitrogen, and pay attention to the mass spectrometer reading. Method b: Spray the entire surface of the sample with a small low-pressure nitrogen gun, and pay attention to the mass spectrometer reading. Note: If possible, the relevant specifications should specify the nitrogen pressure. 9.6.4 Final test
The measured leak rate R can be obtained by comparison with the standard leak hole, and the background signal should be subtracted. 9.7 Details to be given in relevant specifications
When this test is included in the relevant specifications, the following items shall be specified: a. Test method (9.2, 9.3);
Qk test method 1
Severity level (9.4.1);
Test parameters (9.4.4);
Test parameters (special cases) (9.4.1): e.
Maximum immersion pressure allowed for such devices (9.4.5); * Gross leak: test method to be used (9.4.8); Qk Test Method 2
Time constant (9.5.3);
Gross leak: test method to be used (9.5.4); Qk Test Method 3
Installation conditions (if necessary) (9.5.1); j
Alternative method a) or b) (9.6.3); .…k,
Ammonia pressure (9.6.3 b);
Acceptance criteria (9.2).
10 Test Q1: Pressurized immersion test
Determine the sealing performance of the test sample whose electrical properties are affected by liquid penetration. 10.2 Scope
This test can be used to determine air leaks greater than 1 Pa cm/s and is only applicable to test specimens that can withstand external overpressure (see Chapters F1 and F2).
10.3 Description
The essence of the method is to allow a test liquid to penetrate into the test specimen through the leak. This method is usually called a pressurized soak test.
The test liquid must have the property of causing a detectable change in the electrical properties of the test specimen. Leaks are determined by measuring the influence of the specified electrical parameters on the test specimen due to the penetration of the test liquid (e.g. alcohol). The addition of a pigment to the test liquid will show the path of penetration after opening the tested test specimen. Since it takes a certain time for the penetration of the test liquid to affect the electrical parameters, repeated measurements separated by short-term storage may be required.
The maximum sensitivity of this method is about 1 Pa cm/s and no quantitative data on the leak rate can be obtained. 252
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.