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The Impact of Environmental Sealing on Electromechanical Devices
By Joe Torzillo, Vice President of Sales — HMI Components, EAO Corporation
other elements, such as indicators and alarms, are critical aspects of human- machine interfaces (HMIs) for control- ling equipment and systems. Full consideration must be given
E
to the environment in which these devices will be deployed, before speci- fying for any advanced HMI system. Where water, fuel, cleaning solutions, fine dust, and other materials may come in contact with control panels it is important to select components with an appropriate rating for envi- ronmental protection. Failure to do so might lead to significant danger to people and equipment.
The IP Rating System Widely used throughout Europe,
the IP rating system describes the “degree of protection” as defined by the International Electrotechnical Com - mis sion standard 60529 (IEC-60529). IP stands for “international protec- tion,” though is frequently referred to as “ingress protection.” The degree of protection as defined by the IEC is used to describe protection offered to people against hazardous parts inside an enclosure, protection of equipment inside the enclosure against the intru- sion of solids and the protection of equipment inside an enclosure against
NEMA considers numerous requirements, including corrosion resist- ance, effects of icing, gasket aging, oil resistance, and coolant effects.
tion of an enclosure: “a part provid- ing protection of equipment against certain external influences and in any direction protection against direct contact.” The rating proves the device has been tested according to international standards, providing a more detailed measure than generic
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sists of the letters IP followed by two numerals and is sometimes followed by optional letters. The IEC standard defines additional letters that can be appended to classify only the level of protection against access to haz- ardous parts by persons. The IP rating system does not
lectromechanical devices, inclu - ding switches, keypads, key- boards, pointing devices, and
the ingress of liquids. HMI devices must be rated since they fall within the IEC defini-
marketing terms like “waterproof.” Understanding the IP system is simple. The IP code designation con-
cover condensation, fungus or harm- ful vapor, however, so assumptions should not be made that a highly rated switch will be protected from everything. Explosion-proof switches are also not included. For instance, switches used in
oil refineries must be specified for that use and be intrinsically safe. Some IP ratings may require further clarification from the manufacturer, especially for those ending IPx7 and IPx8. The number 8 specifies that the device is suitable for continuous immersion in water under conditions explicitly named by the manufactur- er. The depth of the water and dura- tion must be defined. The reason is that some bodies
of water are so deep that virtually no object can withstand the pressures, and would collapse. Also, continuous might be interpreted as eternal, which is impossible to guarantee. Where there is any doubt, seek fur- ther clarification.
NEMA In the United States, the
National Electrical Manufacturers Association sets the requirements for environmental sealing and its stan- dards are widely used throughout North, Central and South America. The NEMA Standards Publication
Continued on next page
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