Insulation casings are critical components that connect conductors to the equipment shell, divided into those that are integrated with the shell and those that are separate from the shell.
Specific types of insulation casings, such as Class I and Class II threaded Ex insulation casings and Class I non-threaded Ex insulation casings, can be assessed as equipment; other types are considered as Ex components.
Insulation casings made of molded insulating materials must meet the requirements of specific safety standards regarding non-transmission explosion tests.
During testing, the insulation casing is installed on a representative shell with the maximum volume of the expected final application, and the conductor length must reach the minimum value specified in the documentation.
The insulating material itself can enhance the mechanical strength of the shell.
Insulation casings with adhesive assembly components must comply with the relevant standards for non-transmission explosion tests.
Similarly, when installed on a representative shell with the maximum volume, if the conductor length meets the minimum value requirements, it can be considered to meet the bonding requirements.
If these conditions are not met, they must be designed and tested according to specific requirements.
Insulation casings outside explosion-proof shells must receive additional protection according to relevant standards.
When integrated with the explosion-proof shell or specifically designed for that shell, they are required as part of the relevant shell.
Insulation casings as Ex components must undergo pressure type tests, such as the static pressure test specified in GB/T 3836.2.
The test pressure for Class I electrical equipment is 2000kPa, and for Class II electrical equipment, it is 3000kPa.
Routine pressure testing is also required unless the manufacturer can document that their assembly procedures ensure product consistency with written descriptions, and the adhesive joints meet the requirements during leakage testing.
Restrictions on explosion-proof qualification certificates for Ex components will specify the maximum shell volume and minimum conductor length to ensure the safety and reliability of the equipment.
