IEC 60079-6:2015 pdf download – Explosive atmospheres – Part 6: Equipment protection by liquid immersion “o”.
3.7 disconnector mechanical switching device which provides, in the open position, an isolating distance in accordance with specified requirements Note 1 to entry: A disconnector is capable of opening and closing a circuit when either negligible current is broken or made, or when no significant change in the voltage across the terminals of each of the poles of the disconnector occurs. It is also capable of carrying currents under normal circuit conditions and carrying for a specified time currents under abnormal conditions such as those of short circuit. [SOURCE: IEC 60050-441 :1 984, 441 -1 4-05] 3.8 switching device device designed to make or break the current in one or more electric circuits [SOURCE: IEC 60050-441 :1 984, 441 -1 4-01 ] 3.9 safety device device intended for use inside or outside explosive atmospheres but required for or contributing to the safe functioning of equipment and protective systems with respect to the risks of explosion 3.1 0 tap selector device designed to carry, but not to make or break current, used in conjunction with a diverter switch to select tapping connections [SOURCE: IEC 60050-421 :1 990, 421 -1 1 -02] 4 Constructional requirements 4.1 General For Type of Protection “liquid immersion “o”, the Ex Equipment or parts of the Ex Equipment are immersed in a protective liquid in such a way that an explosive gas atmosphere, which may be above the liquid or outside the enclosure, cannot be ignited. The Ex Equipment is constructed to ensure that the necessary amount of protective liquid is present. Dependent on the intended Equipment Protection Level, this is achieved by monitoring device(s), indicator(s) or a level control safety device with automatic switch off. NOTE In accordance with the requirements for all electrical equipment given in IEC 60079-0, it is assumed that the relevant industrial requirements have been applied. The requirements of the IEC 60079 series of standards supplement those industrial requirements.
4.2.2 Requirements for Level of Protection “ob” Electrical circuits and components, when liquid immersed in accordance with this standard, are considered to be not ignition capable in normal operation and during expected malfunctions, and shall be assigned a Level of Protection “ob” (EPL Gb or Mb). A liquid level indication according to 4.7 is required. Switching devices protected by liquid immersion level of protection “ob” shall comply with the following additional requirements: a) When a sealed enclosure is employed, the enclosure shall comply with the overpressure test in 6.1 .1 using four times the prescribed pressure. b) Electrical equipment containing switching devices operated in the protective liquid, rated at 2 kVA per contact or less, are permitted without further test. Where the switching device is rated above 2 kVA per contact, neither pressure increases nor excessive decomposition products shall invalidate the type of protection as demonstrated by tests in accordance with 6.1 .5. c) The equipment shall be suitable for a prospective short circuit current of 32 kA unless marked with a lower value. Disconnectors and manual tap selectors, above 1 000 V, shall be lockable and provided with a warning according to 7 i). In addition, information on their use shall be included in the instructions. 4.2.3 Requirements for Level of Protection “oc” Electrical circuits and components, when liquid immersed in accordance with this standard, are considered to be not ignition capable in normal operation or in the case of regular expected occurrences, and shall be assigned a Level of Protection “oc” (EPL Gc). Ex Equipment containing switching devices operated in the protective liquid, rated at 1 0 kVA per contact or less, are permitted without further test. For switching devices rated above 1 0 kVA per contact, neither pressure increases nor excessive decomposition products shall invalidate the type of protection as demonstrated by tests in accordance with 6.1 .5.
4.5 Liquid containment enclosures 4.5.1 General The chemical resistance against the protective liquid shall be documented by the manufacturer. NOTE It is not a requirement of this standard that conformity to the chemical resistance against the protective liquid be verified. The enclosures shall be subjected to the type tests as specified in Clause 6 for sealed and unsealed enclosures respectively. Connection bushings provided for termination of the electrical conductors shall be considered as part of the enclosure and subject to the requirements of this clause. 4.5.2 Sealed enclosures Covers of sealed enclosures may be continuously welded to the enclosure, or sealed by means of a gasket, in which case, the cover shall be provided with special fasteners according to IEC 60079-0. Equipment with a sealed enclosure shall be provided with a pressure-relief device. This device shall be permanently set by the manufacturer of the liquid-filled equipment to operate at a pressure of at least 1 0 kPa. Enclosures permanently sealed at the time of manufacture shall not be capable of being opened without leaving visible evidence that the enclosure has been opened. The enclosure shall be marked in accordance with 7 c).