Any mechanical design engineer who designs enclosures MUST have a firm grasp of IP ratings. IP stands for “Ingress Protection” and is a standard protection marking for casings and enclosures of electrical and electronic products. It helps to classify them according to their degree of protection against solids and liquids. The standard IP ratings were originally developed by the International Electrotechnical Commission (IEC) and its corresponding code is IEC 60529, while the equivalent European standard is the EN 60529. Simply put, the IP rating indicates the level of dustproofing and waterproofing achieved by a casing/enclosure design, so that the users of a product are aware of the limits of a device/component – and its intended operational scope and conditions.

A practical example of IP Ratings

For example, industrial forklifts in bottling facilities require electric motor controllers or throttle assemblies of a high IP rating. This is because moisture levels in these facilities are naturally high and the chances of a liquid spillage are equally high. On the contrary, an indoor warehouse electric order picker doesn’t need an electric motor controller of a high IP rating since it operates in much less harsh conditions, so a more cost-effective choice can be made.

Decoding IP Ratings

The IP rating consists of two digits, with the first one indicating the ingress protection against solid particles and the second one against liquids. The digits range from zero to six and zero to nine respectively, corresponding to nine different levels of protection from none to ultimate, so the higher the number the better the protection.

The 1st digit: Solids

The first digit indicates the level of protection of a casing against solid particles of any kind. The corresponding levels of protection are listed below:

0	The casing doesn’t offer any kind of protection against contacting other objects – no test required
1	Protected against objects that are larger than 50 mm (e.g. a hand)
2	Protected against bigger than 12.5 mm (e.g. fingers)
3	This covers objects larger than 2.5 mm, e.g. tools and wires
4	If you are looking for a casing that will keep out wires, screws, screwdrivers, and most insects, then a first IP digit of 4 is the safest choice
5	Reflects adequate protection against dust particles under normal atmospheric air pressure conditions, and complete protection against dust even under vacuum pressure conditions respectively
6	Generally preferred for products that are never meant to be opened for service/maintenance and cleaning

The 2nd digit: Liquids

Liquids are much harder to keep out of a casing/enclosure, so the classification categories are eleven, starting from zero (no protection) and ending on “9k” (maximum protection). These digits are shown second in the IP rating and are defined as follows:-

0	No protection – no test required
1	Protection against water drops with enclosure in a single orientation
2	Protection against water drops with the enclosure in 4 different orientations
3	Protection against water spray
4	Protection against water spray
5	Protection against water jets
6 / 6K	Protection against particularly powerful water jets
7	Protection against water while submerged at a depth of one meter
8	Protection against water up to a depth of 3 meters

Putting both digits together to form a complete IP rating

For example, when a device has an IP 54 rating, this means that the enclosure is adequately protected against dust and water splashes. Another example could be an IP 68 rating which means that the casing offers ultimate protection against dust and can be safely submerged in water at a maximum depth of up to three meters without risking a short-circuit inducing penetration of liquid.

Keep in mind that the two digits are independent but still logically related since you can’t have ratings such as “IP 47” which would mean that the casing is suitable for immersing in liquids at a depth of one meter, but has no protection against solid particles smaller than 2.5 mm. This would mean that the particular IP rating is a false claim.

Testing and Certification of IP Ratings

For products to be officially released with an IP rating they need to be tested by certified laboratories which perform the tests in accordance with the IEC 60529 standard. Testing the sealing of the enclosure against solids is done by the use of spheres of specific diameters (50, 12.5, and 2.5 mm) and checking whether the spheres can reach the critical parts of the electrical/electronic device. For the dust tests, if a device succeeds in the “5” classification, researchers proceed to apply a vacuum in the casing for eight hours so as to determine whether it is fully dust-tight or not.

The waterproofing tests are performed by setting specific water volumes, water dropping rates, water pressure and test duration. For example, the spraying water for the classification “3” is performed for a duration of 10 minutes, during which water at a pressure range of 50-150 kPa is dropping from a spraying nozzle at a rate of 0.07 litres/minute per nozzle hole. The immersion test of “7” dictates that the specimen must be submerged to a depth of one meter for 30 minutes. Finally, the ultimate test of “9K” must be performed by jetting 80 degree Celsius water in all of the casings angles at a pressure range of 80-100 bars, at a maximum distance of 15 cm.