LEAK TESTING FOR
INGRESS PROTECTION CLASS IP67
Many housings for electrical components like sensor enclosures as well as battery
cases for lithium ion drive battery packs are specified as ingress protection class
IP67. The second digit – “7”- stands for protection against intake of water. The test
specifies that the part to be tested be exposed to water at one meter depth for 30
minutes and to make sure that no water that could damage the electronics inside
enters the enclosure.
Many customers struggle with the question of what helium leak rate specification
this relates to. INFICON setup an experiment to answer this question.

TESTING SETUP

Prel = 0.1 bar

A test part was created which can be equipped with artificial leaks of different sizes. The artificial
leaks are made from glass capillaries with a defined diameter to represent a distinct leak path size.
Capillaries with 10 µm to 40 µm were investigated. The test part was filled with water andpressurized to 100 mbar overpressure (~ 1.1 bar absolute pressure), equivalent to the pressure in
1 m depth. The outlet of the artificial leak was then observed for 30 minutes and the amount ofwater dripping out was tracked.

RESULTS OF WATER TESTING
The results of the water testing are summarized in the below table:
Leak path diameter

Leak rate10 µm x 10.5 mm

0.0007 sccm
-5
(1ꞏ10 mbarꞏl/s)
0.001 sccm
(2ꞏ10-5 mbarꞏl/s)
0.03 sccm(5ꞏ10-4 mbarꞏl/s)
0.05 sccm(9ꞏ10-4 mbarꞏl/s)
0.2 sccm(3ꞏ10-3 mbarꞏ/s)
7.6 sccm(1ꞏ10-1 mbarꞏl/s)

20 µm x 10.5 mm
25 µm x 10.5 mm
29 µm x 10.5 mm
40 µm x 10.5 mm
100 µm x 10.5 mm

Amount of water dripping off in
30 minVery small droplet forms, but does
not drip off
One drop forms but does not drip off
within 30 min
3 drops

Average time per dropn.a.
Drop may drip off after 40 – 50 min
depending on temperature and humidity
8:30 – 9:00 min

3 – 4 drops

7:30 – 8:30 min

20 drops~ 1:30 min

560 drops~ 3 seconds

The test proved that the leak path where the force generated by the water pressure trying to push the water through the leak pathand the forces that make the water adhere to the surface of the leak path are in equilibrium, is just below 20 µm in diameter.

CONVERSION TO LEAK RATE SPECIFICATION
The following graphs describe the correlation between the amount of water going through a potential leak within 30 min and thecorresponding gas leak rate. The helium leak rate and the air leak rate differ with the same factor as the ratio between the dynamic
viscosity of helium compared to the dynamic viscosity of air. As these differ by only 7%, for the resolution of the above graph thesecan be considered identical. In both graphs, the yellow lines show the direct conversion of the test results for a leak path made fromglass. The other lines show the corresponding leak rates for other materials as converted by their material properties.

LEAK TESTING FOR INGRESS PROTECTION CLASS IP67

Leak rates for 100 mbar differential pressure
Many parts that are designed for IP67 also only withstand very limited pressure differences (typically only 100 to 200 mbar)
without damaging the part itself or the seals of the part. The above graph shows the leak rates for a pressure difference of100 mbar. Depending on the amount of water your part can tolerate you can read the allowable maximum gas leak rate tobe tested for. If your part geometry is made e.g. from an ABS or steel housing with a polymer seal, you should test your part-3
for leak rates below the 2*10 mbarꞏl/s (~ 0.1 sccm) if you can tolerate a few drops of water (orange / green line). If you want-3
to allow no water leakage at all, you should go for a 1*10 mbarl/s (0.06 sccm) leak rate. If your part is made from analuminum with a polymer seal so that the leak path is an aluminum surface on one side and a polymer surface on the other-4side, use an intermediate leak rate level between the two materials, i.e. test in the 1*10 mbarꞏl/s range if you can tolerate a-5
few drops of water. Go for a mid 10 mbarꞏ l/s range leak rate if you want to be absolutely sure no water can penetrate into
the housing.

CONCLUSION
Leak testing for ingress protection according to IP67 requires sensitive leak testing methods that can test well below 1 sccm
leak rates. Tracer gas leak testing is the method of choice for these applications. Different pressure conditions and different
materials yield different leak rate specification. Contact us with your specific needs for testing and we will be happy to help
you reach the highest efficiency and reliability of testing!

www.inficon.com

reachus@inficon.com

Due to our continuing program of product improvements, specifications are subject to change without notice.
miaq00en-02 (1910)©2019 INFICON