IP protection level requirements for explosion-proof equipment used in combustible dust areas
1、 What is the IP protection level?
IP level, also known as enclosure protection level, is the abbreviation for Ingress Protection. IP level is the protection level for electrical equipment casings against foreign object intrusion, derived from the International Electrotechnical Commission's standard IEC 60529, which was also adopted as a national standard in the United States in 2004.
For the protection of electrical equipment casings against foreign objects, the format of the IP level is IPXX, where XX is two Arabic numerals, the first X represents the dust level of the equipment, and the highest is basically 6; The second X represents the waterproof level of the device, with a maximum basic level of 8. The specific protection level can be referred to in the table below (the larger the number, the higher the protection level).
2、 IP protection level requirements for explosion-proof equipment used in combustible dust areas
(1) Generally speaking, since intrinsically safe equipment has already taken measures for the circuit itself, it is not necessary to use the casing as a protective measure for intrinsically safe equipment. However, due to the potential weakening of intrinsic safety performance by conductive components, such as any type of dust, reliable creepage distance may be reduced. Therefore, according to the requirements of IEC61241-0:2004, the equipment casing should meet the minimum IP6X protection level requirements specified in GB4208-2008.
(2) Equipment components without IP6X outer shell protection level should be considered to effectively prevent dust from entering if they are effectively sealed and the sealing thickness is not less than 1mm.
(3) In other cases, the level of shell protection that the equipment needs to achieve is determined by the specific usage conditions of the equipment.
2. Shell protection type tD
(1) For Type A dust tight equipment, various casings including rotating motors should comply with the IP6X requirements specified in GB4208.
(2) For A-type dust-proof equipment, including rotating motors, various casings should comply with the IP5X testing and qualification requirements specified in GB4208.
(3) For Type A dust tight enclosures, the protection level should not be lower than IP6X in Zone 20, Zone 21, and Zone 22 with conductive dust, and not lower than IP5X in Zone 22.
3. Pouring and sealing protection type mD and positive pressure protection type pD
The sealing protection type mD and positive pressure protection type pD do not have clear requirements for the protection level of equipment in the standard GB 12476. However, in the actual certification testing process, it is still necessary to make requirements and measurements for the protection level based on the actual use and scenario of the product.
3、 Supplementary regulations
According to the provisions of GB/T4942.1-2005, the protection level of the ventilation holes of the external fans of rotating motors should be at least IP20 at the inlet and IP10 at the outlet.
For zones 21 and 22, when the rated current does not exceed 10A and the rated voltage does not exceed 250VAC or 69VDC, the plug and socket do not need to meet the requirements of 12476.1.19.1 if they both meet the following requirements:
1) The socket is connected to the power side.
2) There is an arc extinguishing delay time before the plug and socket are disconnected.
3) During the arc extinguishing period, the plug and socket comply with IP6X dust tight housing.
For lighting fixtures with interlocking devices for opening and power-off, in order to minimize the risk of explosion, live components should be protected by an internal shell with an additional protection level of no less than IP30, and a warning sign stating "Do not open with power" should be attached.
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