Feature IP ratings
manufactured, microscopic particles of dust and water droplets will be able to fit through the gaps which are left if a seal is not also employed. As a result, high-quality enclosures will often feature sealing arrangements to ensure absolute protection around the lid. Separate gasket seals have a habit of wandering out of position or folding during installation, which can not only be infuriating but could be dangerous, especially when working on site. To guarantee that its seals won’t fail, Spelsberg has invested in developing an injection moulding technique which means the seal is formed as a single con- struction which is an integrated part of the enclosure.
Enclosures which are designed to offer higher IP ratings will typically require tooling to fix the lid in place. While this is often as simple as a few small screws, it plays an impor- tant part in making sure that the seals are securely pressed flush against the surface, and that small impacts won’t affect this. Medium and low IP ratings are more often supported with a ‘push- click’ mechanism which is quicker to use but allows for a small degree of movement once closed. Hinges and other accessories may also affect the enclosure’s IP levels – while they may offer improved access for the user, they also generate more gaps.
Considerations
A popular technique used to deliver an IP rating of IP68 is to fill the enclosure with a silicone gel after the connections have been made. This completely isolates the electrics from the external atmosphere, meaning that any moisture or dust which does permeate through the enclosure’s protection will still not come into contact with them. Gel filled enclo- sures offer distinct advantages and disadvantages which lends them to very specific applications.
The gel means that an IP68 rating is easier to achieve and doesn’t require such expensive tooling, and the units are often supplied cheaper despite being delivered with the silicone mixing packs. Because of the guaran- teed internal protection there is also little need for screw-down lids, which can speed up the installation process and ultimately improve the profitability of jobs which involve numerous installations. However, it is impossible to access the connections without breaking the gel apart once it has been set. This means that, in applications where reg- ular updates or routine maintenance may be required, they can prove time consuming and expensive as a new gel pack will be required each time. So, if the application calls for an
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enclosure to be installed once and then left in an environment that requires IP68 protection – such as underground connections for external lighting sys- tems – gel filled enclosures are the ideal solution. But, for most other applications which require high IP, it is generally better to pay a slightly increased premium for a product which generates its protection through innovative design and high- quality manufacturing.
gland offers absolute security, while ‘push-fit’ membranes offer a speedy solution for applications which are less exposed to the elements. Finally, it is important to check that the installation process does not risk compromising the effectiveness of the enclosure’s designed-in protection. There are many examples which can be quoted where a customer has speci- fied a high rating enclosure with dome topped cable glands and after a few
‘EN 60529 outlines the universal rating system which utilises the letters IP
(Ingress Protection) followed by two digits – the first to indicate the degree of protection against foreign bodies and the second to indicate protection from moisture. A third digit may be added to indicate protection from mechanical impact damage, but this is rarely used’
A final consideration when specify- ing the enclosure is the number of entries that may be required and ways in which the entry option is presented. As standard, many enclosures are available with knock-out points around the walls of the unit which can be removed using the correct tools. This method is preferable to pre-cut holes as it means that the enclosure is supplied with its IP rating intact. However, there is a fine balance between the knock-outs being extremely hard to remove and being too easy; either vastly increasing instal- lation time or risking accidental removal once in application.
Meeting protection requirements Some companies, like Spelsberg, offer a customisation service which allows the customer to specify the number, size and location of each entry point. This means that the product is deliv- ered ready to be installed with no risk of entry points being opened which are unnecessary. The company offers this service on nearly all of its 14,000 standard products, and all work is carried out on its in-house CNC machines, meaning that no min- imum order quantities are required. A sales team is available to help design the enclosure to the exact requirements of the application. But, specifying the correct enclosure is only the first step in delivering a housing solution which meets the correct requirements. As soon as a cable enters the unit its IP rating is compromised, which means that specifying the correct entry sealing solution is equally important. There are many guides to specifying the cor- rect cable gland for an application available online (and a video on the topic produced by Spelsberg), but suffice to say that for high IP ratings the traditional dome topped cable
months found that there has been water or dust ingress. This is normally caused by a simple oversight in the process which can be easily prevented. Mistakes to avoid include:
• Positioning the entry points on the top side of an enclosure located out- side, where puddles of water are likely to collect around the seal and be drawn in by heat expansion and contraction.
• Fixing caution notes and signs to the lid of an enclosure with screws that perforate the enclosure.
• Not fitting breather valves in high humidity environments with a large temperature differential.
• Compromising the enclosure by fixing it to a wall or bulkhead through the back panel – some enclo- sures supply grommets to cover internal screw heads and others pro- vide bracketing or din rail mounting systems that remain external to the internal box space.
• Using enclosures with loose gaskets that fall out of place as the lid is closed or tightened up.
Mistakes like this are easy to avoid and any good supplier should be able to offer advice on how best to reap the benefits of any enclosure’s IP potential.
Guarantee the IP rating Manufacturers have invested heavily over the years to develop manufactur- ing techniques and product designs which offer the maximum protection from moisture and foreign particles. Some are more reliable than others and some offer easier or quicker instal- lation, so it’s always worth asking how an enclosure’s IP rating is achieved. Most suppliers should be able to show you the different options available and help in the specification process.
Spelsberg T: 01952 200716
www.spelsberg.co.uk WINTER/SPRING 2013 Enclosure & Panel Building Solutions Enter 252
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