8  Metal casing and metal components of the casing

8.1  Material composition

The materials of the shell or shell components should be specified in the documents required in Chapter 24.

Note 1: This document does not require experimental verification of the chemical composition of the material.

Note 2: The paint or coating applied to the metal shell is a non-metallic component of the shell, and the requirements of 7.4 apply.

Note 3: Zinc and zinc alloys containing 80% or more zinc are prone to rapid deterioration (especially in terms of tensile strength), especially in warm and humid air. Zinc is also considered more reactive than other metals, and some explosion-proof types do not allow the use of zinc in the casing.

8.2 Class I equipment

The total content (mass fraction) of the shell material for manufacturing Class I EPL Ma or Mb equipment should not exceed:

——15% aluminum, magnesium, titanium, and zirconium, with magnesium, titanium, and zirconium not exceeding 7.5%,

The above requirements do not apply to Class I portable measuring equipment, but the equipment should be marked with the symbol 'X' in accordance with the requirements of 29.3e), and special precautions should be indicated during storage, transportation, and use under special conditions of use.

8.3  IIClass equipment

The total content (mass fraction) of Class II equipment enclosure materials manufactured for different equipment protection levels should not exceed:

——For EPL Ga: 10% aluminum, magnesium, titanium, and zirconium, with magnesium, titanium, and zirconium not exceeding 7.5%,

——For EPL Gb: 7.5% magnesium, titanium, and zirconium

——For EPL Gc: There are no other requirements except that the fan, fan cover, and vent baffle should meet the requirements of EPL Gb.

If it exceeds the above EPL Ga orGbThe material composition of grade equipment is limited, and the equipment should be marked with "X" according to the provisions of 29.3e). Special usage conditions should contain sufficient information to ensure that users can determine whether the equipment is suitable for use under specific conditions, such as preventing ignition hazards caused by impact or friction.

8.4  Class III equipment

The total content (mass fraction) of Class III equipment shell materials manufactured for different equipment protection levels should not exceed:

——For EPL Da: 7.5% magnesium, titanium, and zirconium

——For EPL Db: 7.5% magnesium, titanium, and zirconium

——For EPL Dc: There are no other requirements except that the fan, fan cover, and vent baffle should meet the requirements of EPL Db.

If the material composition limit of the EPL Da or Db level equipment mentioned above is exceeded, the equipment should be marked with "X" according to the provisions of 29.3e), and the special use conditions should contain sufficient information to ensure that the user can determine whether the equipment is suitable for use under specific conditions, such as preventing ignition hazards caused by impact or friction.

8.5  copper alloy

If intended for use in environments containing acetylene, the equipment casing and Ex component casing for external installation, if made of copper or copper alloy, shall meet the following requirements:

——Coating with zinc, nickel or other coatings; or

——The maximum copper content in the alloy shall not exceed 65%.

The cable entry devices, sealing components, threaded pipe joints, and insulation sleeves specified in Appendix A are not considered as shell surfaces that require coating or copper content limitations.