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How IP ratings apply to flexible conduitThere is often misunderstanding regarding Ingress Protection (IP) ratings, because many people believe they understand them fully, explains Meirion Buck of Adaptaflex Ltd.
This popular misconception is based on the theory, ' if the IP rating number is higher then it has to be better than the lower number rating.' Technically, however, this is incorrect at the higher IP ratings.
IP rating standards, such as IEC EN 60529 and DIN 40050 specify how products should be tested and define the particular test for each rating. The standards also clearly explain the meaning of each individual IP rating.
The variation in the specification can best be understood by comparing the methods of determining the IP ratings to static and dynamic tests. Static tests have the items immersed in a measure of water, whereas dynamic tests subject the item to jets of water. Dynamic tests vary quite considerably; an IPX4 rating is equivalent to water from a garden hose at typically 10 litres/min for 5 minutes through 180º, whereas an IPX6 is closer to a fire hose delivering 100 litres/min for 3minutes.
On a typical Ingress Protection rating, say IP54, the first number stands for the protection again dust and solid objects, while the second number stands for the protection against liquids.
In this case IP54 means, 5 - protected against dust - limited ingress no harmful deposit; 4 - protected against splashing water through 180º - no harmful effects.
The tests, up to IPX6, are carried out on a static product where the water is either splashed or sprayed around the product under test. The intensity of the water test ranges from falling drops of water through to a powerful spray jetted on to the product from specified angles.
The water test conditions are very specific within the EN 60529 standard, defining water flow rates and duration of test. Even the diameter of the water jet hose nozzle is specified along with the distance from the test piece. For IPX6 the flow rate is 100 litres per minute for duration of at least 3 minutes.
IPX7 and IPX8 use static tests, conducted by immersion in water.
Temporary immersion is the IPX7 test. This is a pre-set depth of 1m and a pre-set time of 30 minutes. During the test there should be no ingress of water to cause harmful effects.
The continuous immersion IPX8 test, is set against a pressure and a time agreed between manufacturer and user. Again, during the agreed period, there should be no ingress of water in quantities sufficient to cause harmful effects. The test has to be more severe than the IPX7 test.
For IPX8 the test states - 'protected against long periods of immersion under pressure'. Hence the result of the test should be specific and clearly quantified i.e. IPX8 15 bar, illustrating that the product has been tested at a depth of 150 metres of water for a specified time.
The test against IPX8 the pressure rating must be stated to clearly indicate the depth of water at which the test was carried out. This is standard practise on cable data and clearly indicates the operational capability of a product. For example IPX8 15bar 30 minutes
The German DIN 40050 standard for automotive use, has an IP69k test, which typifies installations on vehicles subjected to pressure jet washes. This involves spraying high pressure water at 60 to 80C at angles of 0, 30, 60 and 90 degrees at between 10 - 15 cm distance.
Ingress Protection (IP) Ratings
Relating all this to flexible conduit systems, we have seen that spray tests up to IPX6, are quite different to immersion tests for IPX7 and X8. Indeed, products that have IPX7 or IPX8 may well fail the IPX6 test, as the jet of water can, in some cases, force its way past a gasket or seal, that seal perfectly well under static loads when the weight of water is helping to compress it even further.
It is for this reason that Adaptaflex is leading the way in 'dual ratings' for ingress protection for its high IP systems. That way you have all the facts about whether a conduit system is suitable for use in direct jet spray and/or immersion applications
For example, in Adaptaflex's case, its Liquid Tight equivalent conduit system has an IP66 rating, IP67 and an IP68 rating at 15 bar for 30 minutes (an equivalent depth of 150 metres). This affords both immersion and spray approval, making the product suitable for use in both applications.
Understanding IP ratings is extremely important. When an IPX8 rated product is specified it should be qualified with a pressure rating in bar. This leaves the specifier in no doubt about the capabilities of the system.
The long term use of approved and specified flexible conduit systems is important to maintain system integrity of any installation. There are installations where a flexible conduit system is used to carry cabling beneath water, even flowing rivers. Bearing in mind that over a short period of time that conduit will become buried in the silt on the river bed it is particularly important that the specification is correct.
Whatever the application, the product has to be fit-for-purpose and it is a responsibility of the specifier or electrical contractor carrying out the installation to ensure the product meets the requirements. This they can do by checking with the manufacturers that the information they are being given is correct.
"We see many instances where the information is provided, but in a misleading form. What we are looking for is a clear, concise presentation so customers can be certain they are comparing like with like and that people understand an IPX8 rating and an IPX8 to 10 bar are not the same," adds Meirion Buck.
This is standard practise in cabling where cable glands are specified and is widely understood by specifiers and electrical contractors.
The same should apply for flexible conduit systems where IP ratings are specified, so there is clearly no confusion or misunderstanding.
The moral of the story is to be totally conversant with IP ratings and remember that tests up to IPX6 are dynamic spray tests and tests for IPX7 and IPX8 are static immersion tests. The key test for product which has a 'quoted' IPX8 rating is simply to ask the manufacturer or supplier at what pressure and for what duration of time the test was carried out.
Adaptaflex's new Cable Management Solutions catalogue clearly shows the IP rating for each individual system so there can be no doubt of its suitability for a given application.
So, the higher the IP number does not necessarily mean the better the performance as clearly defined by the spray and immersion tests. Clear knowledge of IP ratings means you can apply the most economical solution, designed to meet the requirements of the installation and fit-for-purpose.
21 November 2006
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