IP ratings sorting out fact from fiction

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Even though IPx9 has now been recognised by the British Standard BS EN IEC 60529, this is no guarantee against water ingress over the long term life of the equipment argues Ian Gibson, technical director for Flexicon

 

I suspect everyone reading this is well aware of the IP (Ingress Protection) rating system and most people probably assume that by looking up the relevant tables they can specify which rating they need to ensure protection against dust and water ingress.

To recap, BS EN IEC 60529 specifies a series of tests to assess the protection of an enclosed system against the ingress of solid objects and water (see table 1). It is a case of buyer beware however, since the IP water ingress tests are very short and are conducted on samples that have been assembled under ideal conditions.

They can only really give an indication of long-term performance and specifiers should ask for more information about the test conditions to fully understand the product’s performance.  So for example for an IPx8 rating, what is the water depth or pressure and how long is the product subjected to this?

Looking more closely at the IP ratings (see table 1 below) there are a few things to note.  First you will notice the introduction of IPx9k, which was formerly defined in DIN 40050, but this performance is now incorporated into BS EN IEC 60529. You should note that in the British Standard this is referred to as IPx9, the ‘k’ has been dropped, but the test is the same.
Many industries, notably the food and rail industry, have been working to IPx9k anyway so you could argue the standards are merely catching up with industry practice. 

Bigger is not always better
When it comes to water ingress it is not simply a case of specifying the highest test and assuming that this is okay.

The standard actually states that above IPx6 you cannot assume that the product will meet a lower level. This is because when you look at each of the tests you will see each is a different type of test and subjected to different conditions and environments.

In practice water ingress could come from a variety of sources including rain, spray, wash-down, steam cleaning, shallow immersion, deep immersion and capillary action and suction caused by the rise and fall of temperature. You should check that the manufacturer declares that their products and systems meet all of your needs, which is why for example that we declare that our LTP and FPAX fittings are IP66 + IP67 + IP68 + IP69 to show that they meet each and everyone of these different tests.

Open to interpretation
Looking more closely at the tests you will also notice that IPx8 is open to interpretation by different manufacturers.

To illustrate the point, for Flexicon conduit systems we declare the pressure and time for our IPx8 testing which is typically two bar pressure for one hour for non-metallic systems and is five bar pressure for two hours for metallic conduit systems. These pressures are equivalent to being 20 metres and 50 metres under water respectively.

Compare this to one of our major European competitors where its IPx8 testing is at 1.2 metres under water for one hour.

Long-term solutions
Perhaps the most important point however is all of the tests are conducted over the short term with products and systems selected by the manufacturers themselves.

The user really needs to take a belt and braces approach to prevent water ingress over the lifetime of an installation, particularly if the consequences of water ingress are serious.

Our best advice is to talk to the manufacturer and be clear on what you require.

Flexible conduit is an interesting example since it is generally used to connect equipment together, so any seals must remain intact to protect the system’s integrity.As a manufacturer we recommend using face sealing washers between the conduit fitting and the equipment that it is attached to, in order to maintain the IP rating.

In the past we have recommended FW fibre washers for metal threads and SW rubber sealing washers for plastic threads since SW seals were too soft for use with metal threads and FW seals were too hard for use with plastic threads.

To make it easier we have now introduced RSW washers, which are injection moulded from thermoplastic elastomer and are suitable for both types of thread. These are included as standard with our FPAX range of conduit and feature retaining pips to prevent the washer falling off and ribs on both sides to ensure sealing performance.

Some flexible conduit manufacturers offer O rings to seal threads, which although cheap, should not be used unless they are housed in an O ring groove, to ensure that they are not over-compressed and therefore destroyed.

The IP rating system is a useful guide to standardise product claims through verifiable tests. As the user of final equipment however you need to be clear these are short-term tests and ensure equipment is properly engineered to maintain the stated IP ratings throughout its life.