How do you set the parameters of a domestic air tightness tester? How are the parameters of an air tightness tester configured? Methods and tips for setting the inflation time, stabilization time, and test time of an air tightness tester.
As consumer demands increase, the products launched will meet the corresponding IP waterproof and dustproof ratings. So how are the IP ratings of these products determined?
Products that generally require waterproof requirements are mostly 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 at a certain depth underwater to determine whether leakage occurs, thereby judging whether the product meets the requirements of IP67/68 and IP69K. So, can the test parameters of the air tightness tester be set directly?
That is definitely not the case. For waterproof rating and air tightness tests across different series, the parameters cannot be set directly on the product, because the products differ in shape and style.
The test time is reasonably set based on 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 to find the critical point of the leakage value and set the air tightness leakage amount.
What is the approach to setting the specific air tightness parameters? Tips and steps for setting the air tightness tester's inflation time, stabilization time, test time, and exhaust time.
1. Purpose of takt time setting:
The most important principle (the most basic requirement): able to distinguish between qualified and unqualified parts.
2. Is there a formula that can calculate the time required for each stage?
There is no such universal formula at present. 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 various 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 factors.
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 stabilizes. For example, if after 15 seconds the pressure has reached the test pressure and is basically stable, then you can determine that the minimum inflation time is 15 seconds. Extending the inflation time will make the inflation more "full," which helps with test stability.
2. Setting the test time:
Set both the fill time and balance time very long, for example 600 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 the following formula is satisfied: ((pressure decay of bad part − pressure decay of good part) / pressure decay of bad part > 0.3, 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 determined in the steps above, you can initially set the balance time to a very small value, such as 20 seconds, and then perform comparative tests with known-good parts, gradually increasing the balance time until the repeatability of the test results meets your requirements. For example, 10 tests were performed with a balance time of 20 seconds and a balance time of 25 seconds respectively, and the data are 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 time is found at which the repeatability meets your requirements.
Repeatability meets requirements: If (pressure decay of a nonconforming part − pressure decay of a conforming part) = 50Pa, then the maximum fluctuation must be within 5Pa at minimum. If a maximum fluctuation of 0.5Pa can be achieved, that would be ideal.
Here: 50Pa is what we call discrimination, and a fluctuation of 0.5Pa is a factor affecting repeatability.
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