IP68 water resistance: what does it mean and how is it tested?

What exactly do the letters and numbers IP68 mean?  

The abbreviation IP stands for "international Protection". In the English-speaking world, the term "Ingress Protection" is often used, which means protection against intrusion. Behind the letters, there are usually two numbers that indicate the classification of the protection. The first digit after "IP" stands for protection against foreign bodies, the second digit stands for protection against water. The higher the individual digits are, the better the protection class of the housing. The first digit is sometimes also replaced by an X.

The meaning of the first digit of the IP protection class designation

The first digit indicates how resistant or tight the housing is against foreign bodies, i.e. dust, dirt or particles. There are six gradations which in principle refer to the grain size of the foreign body. In the laboratory, very fine talcum powder is used for testing.

                      (Keyfender® in the dust chamber during the dust tightness test with connected vacuum hose)

In order to check the dust density of an object, a vacuum (20 mbar) must be created inside the object while it is in a specially sealed dust chamber. The chamber is filled with extra fine talcum powder which is constantly swirled. The test sample is then left in the chamber for eight hours. If no dust has entered the enclosure after this time, it is considered dust-tight and receives an IP6x rating.
These tests therefore checked whether dust could be sucked into a sealed housing. This was not possible, all samples were 100% dust-tight and thus fulfilled the category IP6X, the hardest possible test for dust-tightness.

                                         (Keyfender® in the laboratory during the dust density test with negative pressure and talcum)

• 0 - No protection.

• 1 - Protected against solid foreign bodies with a diameter of 50 mm or more.

• 2 - Protected against solid foreign bodies with a diameter of 12.5 mm or more.

• 3 - Protected against solid foreign bodies with a diameter of 2.5 mm or more.

• 4 - Protected against solid foreign bodies with a diameter of 1.0 mm or more.

• 5 - Protected against dust in harmful quantities.

• 6 - Dustproof.

The meaning of the second digit of the IP protection class

The second number in the protection class designation indicates how waterproof the housing is under various conditions. A distinction is made here between eight different levels. The tests are usually carried out with special pressure vessels.

                                  (Closed pressure chamber for the waterproof test )

The test sample is therefore 100% waterproof and meets the IPX8 standards, if no water penetrates through continuous submersion under the manufacturer's conditions (here one hour at 10m diving depth). So these cases are suitable for permanent submersion for up to one hour, up to 10 meters depth. The test conditions for this are that the enclosures are subjected to a pressure of 1.0 bar for one hour in a closed pressure vessel filled with water.  

                                        (Testing is always done in groups. Here you can see the open pressure chamber).

• 0 - No protection at all.

• 1 - Protection against dripping water.

• 2 - Protection against falling dripping water when the housing is tilted up to 15°.

• 3 - Protection against falling spray up to 60° from the vertical.

• 4 - Protection against splashing water from all sides.

• 5 - Protection against water jets (nozzle) from any angle.

• 6 - Protection against strong jets of water.

• 7 - Protection against temporary immersion.

• 8 - Protection against permanent submersion. Unless otherwise specified, protection is provided up to a water depth of 1 metre. Other water depths must be specified or agreed separately.