Protecting circuitry from dust and moisture
Proper sealing of an electrical enclosure is crucial as the harmful effects of both dust and moisture to sensitive equipment can cause failure and reduce reliability. Overall security has become an issue leading to increased protection for electrical enclosures, but is enough consideration given to the protection rating?
In addition to carrying a range of enclosure types and accessories to provide ideal solutions, advice on specifying enclosure ratings should be provided by all dedicated enclosure suppliers and specialists, no matter what the challenge.
Enclosure manufacturer Rittal has a wide range of enclosure systems and accessories that offer different materials and designs as well as IP ratings. Many of their small enclosures have an IP rating of IP68 and Rittal has tested all of its IP69K enclosure ranges and will issue a certificate of the test carried out.
The IP rating of an enclosure is dictated not only by the enclosure itself, but also by its fixing method, lid sealing and cable entries. When mounting an enclosure inside a cabinet, fixing to a machine wall, a building wall or in a vehicle, the method of attachment can either maintain or instantly downgrade the IP rating of the enclosure assembly.
Generally the lid arrangement has a big affect on the sealing; basic 'click' fit lids are IP54 or lower whereas a lid fitment of IP54 and above requires an additional compressible seal to achieve higher protection. Machine applied polyurethane seals are generally more reliable than gasket types as they are not prone to movement during fixing and a seal that runs inside the lid fixing screws is normally required for IP65 and above.
Cable entries are present in virtually all sealed enclosures offering a significant IP rating and vary from basic gland plates through to independently rated waterproof cable glands. Basic gland plates and open holes offer some protection, but where moisture is present, to any degree, the cable entry must offer a complete seal around the cable sheath. An enclosure can be derated if the cable glands and other surface mounted equipment do not meet the same or higher IP rating.
Other considerations such as ambient atmospheric moisture combined with large temperature fluctuations can also cause condensation problems. In situations where this is likely, it always pays to fit breather valves (or grommets) to allow the enclosure humidity and pressure to equalise without compromising the intended IP rating.
By John Wilkins, Marketing Manager, Rittal
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