AS NZS 60079.6:2015 pdf download.Explosive atmospheres Part 6: Equipment protection by oil immersion‘o’.
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 Levels of protection and requirements of electrical equipment
4.2.1 Level of Protection
Electrical equipment with liquid immersion “o” shall be either: a) Level of Protection “ob” (EPL Gb or Mb); or b) Level of Protection “oc” (EPL Gc). The requirements of this standard shall apply to all levels of protection unless otherwise stated.
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 10 kVA per contact or less, are permitted without further test. For switching devices rated above 10 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.
4.3 Switching device
Switching devices are only permitted for a.c. circuits where the working voltage of the switch does not exceed the values given in Table 1. Switching devices for d.c. circuits are not permitted.
4.4 Creepage and clearance
Electrical circuits and components intended to be immersed in the protective liquid shall meet the relevant industrial requirements for creepage and clearance distances in air before being immersed in the protective liquid. If the relevant industrial standard gives options for pollution degree, pollution degree 2 shall be assumed.
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 10 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).AS NZS 60079.6 pdf download.