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8  Metal casing and metal components of the casing

8.1  Material composition

The materials of the casing or casing 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 materials.

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

Note 3: Zinc and zinc alloys containing 80% or higher zinc are prone to rapid deterioration (especially in terms of tensile strength), especially in warm and humid air. Zinc is also considered more active 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 Class I EPL Ma or Mb equipment casing materials for manufacturing 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' according to the requirements of 29.3e), and special precautions during storage, transportation, and use should be specified in special usage conditions.

8.3 IIClass devices

The total content (mass fraction) of Class II equipment casing materials manufactured for different levels of equipment protection 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 hood, and ventilation baffle should meet the requirements of EPL Gb.

If the above EPL Ga is exceeded orGbThe material composition of grade equipment is limited, and the equipment should be marked with an "X" according to 29.3e), and 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 casing materials manufactured for different levels of equipment protection 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 hood, and ventilation 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 an "X" according to 29.3e), and 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.

8.5  copper alloy

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

——Apply 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.