How do you adjust the parameters of an air tightness tester? How do you set the parameters of an air tightness tester? Methods and tips for setting the inflation time, stabilization time, and test time of an air tightness tester.
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As consumer demands increase, the products launched will all meet the corresponding IP waterproof and dustproof ratings. So how are the dustproof and waterproof ratings of these products determined?
Generally, products that require waterproofing are tested with direct pressure or differential pressure air tightness testers. For example, when an air tightness tester is used for air tightness testing, the air tightness test of the product under test essentially uses compressed air to simulate the pressure the product would experience at a certain depth underwater, to determine whether it leaks and thereby judge whether the product meets the IP67/68 requirements. So, can the test parameters of the air tightness tester be set directly?
Definitely not. For air tightness tests of different IP rating series, the products vary in shape and style, so the parameters cannot be set directly for the product.
The test time is set reasonably according to the product volume, including inflation time, balance time, detection time and exhaust time. The test pressure is set according to the corresponding technical requirements or the pressure resistance of the product. For the upper limit of allowable leakage, it is necessary to repeatedly test confirmed qualified and unqualified products based on the previously set parameters, find the critical point of the leakage value, and set the leakage amount for air tightness.
What is the approach to setting air tightness parameters specifically? Techniques and methods for setting the inflation time, stabilization time, test time, and exhaust time of an air tightness tester.
1. Purpose of takt time setting:
The most important principle (the most basic requirement): the ability to distinguish between qualified and unqualified parts.
2. Is there a formula that can calculate the time required for each stage?
For now, there is no such universal formula. Moreover, such a calculation has little practical significance, because there are simply too many influencing factors. Here are some factors that can affect the testing process: different products vary in internal volume, internal surface area, material, heat dissipation characteristics, deformation characteristics, required test pressure, and upper and lower leak judgment limits. These parameters can be combined in countless ways, making the situation highly complex.
For a test system, there are also the following different states: differences in the length of the test piping, the diameter of the test piping, and the material of the piping lead to different friction and deformation characteristics of the piping with respect to airflow; the various fittings and connectors through which the piping passes also differ, and there are additionally changes in inner diameter and changes in material. These influencing factors also have countless combinations. In addition, there are also the effects of numerous variable factors such as environmental conditions.
In general, it is nearly impossible to solve a test system with a single formula. As you can see, this function would require a very large number of parameters, and many of them, such as the length of the piping, the inner diameter of the fittings, and the flow-limiting characteristics, are unknown before the system is built. Even after the system is built, collecting all these parameters would take so much time that the cycle time would already be finalized by the time you finished debugging!
3. Since there is no formula for calculation, how should the time settings for each test stage be determined?
1. Setting the inflation time:
First, you can set the inflation time very long, for example 900 seconds, then start the test and observe when the pressure value
Wait until it stabilizes. For example, if after 15 seconds the pressure has reached the test pressure and is basically stable, then it can be determined that the minimum fill time is 15 seconds. Extending the fill time will make the inflation a bit more "full," which helps with test stability.
2. Setting the test time:
Set both the fill time and the balance time very long, for example 900 seconds, and set the test time relatively short, for example 2 seconds. Then test a good part and a bad part (the bad part can be simulated by inserting a standard leak orifice into a good part), and record the pressure decay of the good and bad parts at different test times, until this formula is satisfied: ((bad part pressure decay - good part pressure decay) / bad part pressure decay > 0.3, and ideally above 0.7.
For example: if the pressure decay of the leaking part = 100Pa, and the pressure decay of the standard part = 30Pa, then this value will be (100-30)/100 = 0.7.
This is how we arrive at the test time needed to distinguish between good and bad parts. (Test time is the most important time, because it is solely responsible for reliably distinguishing good parts from bad parts.)
3. Setting the stabilization time:
Using the inflation time and test time already obtained in the steps above, the balance time can first be set to a very small value.
value, for example 20 seconds, then perform a comparative test with a known-good part, gradually increasing the balance time until you feel the test result
The repeatability of the results meets the requirements. For example, 10 tests were conducted with a balance time of 20 seconds and a balance time of 25 seconds respectively.
test, the data is as follows:
Balance time = 20 seconds: 3Pa, 5Pa, 3Pa, 7Pa, 4Pa, 3Pa, 8Pa, 3Pa, 5Pa, 4Pa (maximum fluctuation 5Pa)
Balance time = 25 seconds: 5Pa, 5Pa, 5Pa, 4Pa, 5Pa, 5Pa, 6Pa, 5Pa, 5Pa, 6Pa (maximum fluctuation 2Pa)
It can be seen that the result repeatability at a balance time of 25 seconds is better than that at 3 seconds, and so on, until a value is found that makes
What do you think is the time required for repeatability to meet the requirement?
Repeatability meets requirements: If (pressure decay of nonconforming part − pressure decay of conforming part) = 50Pa, then the maximum fluctuation is
The low requirement is within 5Pa. If a maximum fluctuation of 0.5Pa can be achieved, that would be quite ideal.
Here: 50Pa is what we call discrimination, and a fluctuation of 0.5Pa is a factor affecting repeatability.
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The above are the setting methods for the instrument's inflation time, stabilization (balance) time, test time, and exhaust time.
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