AS NZS 60079.2:2015 pdf download.Explosive atmospheres Part 2: Equipment protection by pressurized enclosure ‘p’.
5 Constructional requirements for pressurized enclosures
5.1 Enclosure
The pressurized enclosure shall have a degree of protection in accordance with Table 2.
For Level temperature endurance to metallic parts
of Protection “pxb” with no internal components that exceed the marked class and for Levels of Protection “pyb” and “pzc”, the tests for thermal heat and thermal endurance to cold for non-metallic enclosures and non- of enclosures of IEC 60079-0 need not be applied to the pressurized enclosure.
This is because degradation of the enclosure that results in increased leakage will result in alarm or removal of power to ignition capable circuits. Therefore, the pre-conditioning testing of non-metallic enclosures and non-metallic parts of enclosures is not considered necessary.
5.2 Materials
The materials used for the enclosure, ducts and connecting parts shall not be adversely affected by the specified protective gas.
5.3 Doors and covers
5.3.1 Group I pressurized enclosures
Doors and covers shall either
— have special fasteners complying with IEC 60079-0; or
— be interlocked so that the electrical supply to equipment not providing an EPL as shown in 7.15 is disconnected automatically when they are opened and so that the supply cannot be restored until they are closed. The requirements of 7.7 shall also apply.
5.3.2 Group I pressurized enclosures with static pressurization
Doors and covers shall have special fasteners complying with IEC 60079-0.
5.3.3 Group II and Group Ill pressurized enclosures
The requirements for special fasteners in lEO 60079-0 do not apply.
For Level of Protection “pxb”, doors and covers which can be opened without the use of a tool or key shall be interlocked so that the electrical supply to electrical equipment not identified in 7.15 is disconnected automatically when they are opened and so that the supply cannot be restored until they are closed.
For Level of Protection “pyb” and Level of Protection “pzc”, the use of a tool or key is not required.
Consideration should be given to the possibility that the internal pressure could cause a door or cover to open violently when the fastener is moved. The operator or maintenance personnel should be protected from injury by methods such as the following:
a) use multiple fasteners so that the enclosure will safely vent before all fasteners are released; or
b) use a two-position fastener to allow safe venting of the pressure when opening the enclosure; or
c) limit the maximum internal pressure to not greater than 2,5 kPa.
5.3.4 Group II and Group Ill pressurized enclosures with static pressurization
Doors and covers shall not be capable of being opened readily without the use of a key or tool
5.3.5 Group II and Group Ill Level of Protection “pxb”
A pressurized enclosure that contains hot parts requiring a cool-down period shall not be capable of being opened readily without the use of a key or tool.
5.3.6 Group II and Group Ill Door and Cover warning
To prevent the ignition of an explosive gas atmosphere or an explosive dust atmosphere which may be present when an enclosure is opened, doors and covers shall be marked:
WARNING — DO NOT OPEN WHEN AN EXPLOSIVE ATMOSPHERE IS PRESENT.
5.4 Mechanical strength
The pressurized enclosure, ducts if any, and their connecting parts shall withstand a pressure equal to 1,5 times the maximum overpressure specified by the manufacturer for normal service with all outlets closed with a minimum of 200 Pa.
If a pressure can occur in service that can cause a deformation of the enclosure, ducts if any, or connecting parts, a safety device shall be fitted to limit the maximum internal overpressure to a level below that which could adversely affect the type of protection. If the manufacturer does not provide the safety device, the certificate number shall include the “X” suffix in accordance with the marking requirements of IEC 60079-0 and the Specific Conditions of Use listed on the certificate shall detail the necessary information required by the user to ensure conformity with the requirements of this standard.AS NZS 60079.2 pdf download.