Index of protection
Standards organisations
IEC – International Electrotechnical Commission, publishes international standards for all electrical, electronic, and related technologies. www.iec.ch
NEMA – National Electrical Manufacturers Association, a U.S. trade association sets ratings for environmental sealing. www.nema.org
The IP Rating System describes the ‘degree of protection’ as defined by the International Electrotechnical Commission standard 60529 (IEC60529). IP stands for International Protection, 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 intrusion of solids.
- Protection of equipment inside the enclosure against the ingress of liquids.
The IP code designation consists of the letters IP followed by two numerals, and is sometimes followed by optional letters. The first number is a measure of how well the enclosure can prevent an invasion by solids. The second number indicates the degree of protection against liquids of various pressures, directions and volumes.
The IP rating system does not cover condensation, fungus and harmful vapour so assumptions should not be made that a highly rated switch will be protected.
NEMA considers numerous requirements including corrosion resistance, effects of icing, gasket aging and oil resistance and coolant effects. It is possible to say that a NEMA Type is equivalent to an IP rating but an IP rating is not equivalent to a NEMA Type. The IP code only address requirements for the protection of people, the ingress of solids and the ingress of water. The NEMA Types consider these and also numerous other requirements including:
- Construction requirements
- Door and cover securement
- Corrosion resistance
- Effects of icing
- Gasket aging and oil resistance
- Coolant effects
IP69K
German standard DIN 40050-9 extends IEC 60529 with an additional rating for environmental sealing – IP69K, for high-pressure, high-temperature wash-down applications. Devices must not only be dust tight (IP6X), but also able to withstand high-pressure and steam cleaning. The test is very strict: 80°C water is sprayed through a nozzle at pressures of 8–10 MPa (80–100 bar) and a flow rate of 14–16 Litres/min. The nozzle must be held 10–15 cm from the tested device at angles of 0°, 30°, 60° and 90° for 30 seconds each. The test device sits on a turntable that rotates once every 12 seconds (5 rpm). The IP69K test specification was initially developed for road vehicles, especially construction vehicles and those that need regular intensive cleaning, but also finds use in other intensely hygienic applications (e.g. food industry).
NEMA
In the United States, the National Electrical Manufacturers Association sets the requirements for environmental sealing and its standards are widely used throughout North, Central and South America. The NEMA Standards Publication 250 – 2008 (previously 250 – 2003; 250 – 1997) “Enclosures for Electrical Equipment (1000 Volts Maximum)” defnes enclosures according to their type from 1 to 13. Detailed information on some of the types relevant to HMI components are shown in Table 3.