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Department of healthy (Ex-) sense

Did you know a "wrong" IP class may withdraw the explosion-proof character of an Ex-certified device?

Frequently it is assumed an Ex certified component is suitable for any hazardous areas. However applying the correct IP class is as important as a gas group or temperature class to use it safely.

A (Ex) certified device usually has a minimum IP class of IP54. Nowadays many devices have  a much "higher" IP rating of IP65 or more. First let’s have a look at what IP coding actually means:

IP class according to IEC 60529 describes protection against dust and water.
We are naturally inclined to consider the "highest number" as a better IP class.
However, this is not always correct. Firstly, it is important to know what we are looking for: dustresistace or waterresistance.

The IP class describes two very different aspects, for example IP54:

 

 

Protection against objects and dust resistance.

When we look at dust resistance for the environment, the first number is important to read:

Up to IP4X we speak of "protection against objects" and gives this type of protection no protection against dust.

IP5X and higher provides protection against dust.
IP6X is compatible with lower classification 0X up to 5X.

Protection against ingress of water
The second number describes the waterproofing. Lets start with the classes to X6:

The first class is afforded protection against water.  A device with IPX6 meets the lower classes X0 to X5.

However, we consider the "higher" classes for waterproofing X7, X8 and X9, they should otherwise be noted:

IPX7 / X8 or X9 should be subject to a fundamentally different kind of test than the lower IP classes for water resistance and they cannot be seen as “compatible” for the classes X6 and lower.

Conclusion
Dust- and waterproof classes must be separately evaluated. The use of an improperly selected IP class may endanger the safe operation of a device in an explosive atmosphere. Healthy (Ex) common sense can prevent this.

Higher classifications IP6X for dust resistance meet the requirements of the lower classifications. Up to IPX6 the same applies to water resistance.

A device with IPX7, X8, or X9 class, for water resistance, isn’t by definition suitable for environments that require a lower IP classification.

Of course it is still possible that a IPX8 classified device can meet "lower" IP ratings, provided it is tested by the manufacturer or a Notified Body. Manufacturers should advise their customers and also inform them correctly.

If a certain water resistance class is required, it is imperative to select equipment that is specifically tested for this purpose, as specified by the manufacturer. Therefore it is not obvious that "higher" classes are always better.

Want to know more about this topic? Please contact Jos Abbing.
E: abbing@electromach.nl T: 074-2472413