7 Non metallic casings and non-metallic components of casings

7.1 General rules

7.1 oneApplicable scope

The requirements specified in this chapter and 26.7 shall apply to non-metallic enclosures and non-metallic components of enclosures related to explosion-proof types.

Note 1: Some examples of non-metallic components related to explosion-proof types of enclosures include sealing rings for "e" or "t" type enclosure covers, fillers for "d" or "e" type cable entry devices, sealing rings for cable entry devices, and seals for "e" type switch actuators,

Note 2: In some supplementary or modified parts of this document, the requirements for "non-metallic components of enclosures" in this chapter apply to non enclosure components related to explosion-proof types, such as "d" type insulation sleeves and "e" type terminals.

7.1.2Material requirements

7.1.2.1General rules

According to the documents specified in Chapter 24, the materials of the shell or shell components should be specified

7.1.2.2Plastic materials

The technical requirements for plastic materials should include the following:

A)The name or registered trademark of the resin manufacturer or synthesizer,

B)Material identification, including model and color,

C)Possible surface treatments, such as applying varnish, etc,

D)The temperature index TI corresponding to the 20 000 h point on the thermal stability curve is calculated according to GB/T 11026 at that point 1. GB/T 11026 When measured in accordance with GB/T 9341, the decrease in bending strength shall not exceed 50% If the material does not break during testing before heat exposure, the temperature index should be determined according to the tensile strength measured on lA or lB type test bars specified in GB/T 1040.2. Relative Heat Index (R TI) ­ Mechanical strength or R TI mechanical impact can be replaced by values determined according to ANSI/UL 746B instead of TI.

E)When applicable, data support in accordance with 7.3 (UV resistance).

The data source for the above characteristics should be determined.

Note 1: There is no provision in this document for verifying whether plastic materials meet the manufacturer's technical requirements.

Note 2: When selecting plastic materials, some manufacturers have noted that the types and percentages of fillers, flame retardants, and UV stabilizers have a significant impact on the performance of plastic materials.

Note 3: Material traceability guidelines can be found in GB/T 3836.21. Manufacturers planning to use "fingerprint" methods (such as infrared scanning or oxygen index) to trace the origin of plastics will need to pay attention to this during type testing in order to obtain baseline information.

7.1.2.3Elastic materials

The technical requirements for elastic materials should include the following:

A)The name or registered trademark of the resin manufacturer or synthesizer;

B)Material identification, including model and color;

C)Possible surface treatments, such as applying varnish;

D)Continuous operating temperature (COT);

E)When applicable, data support in accordance with 7.3 (UV resistance)

The data source for the above characteristics should be determined.

Note 1: This document does not specify whether the verification of elastic materials meets the manufacturer's technical requirements.

Note 2: When selecting elastic materials, some manufacturers have noted that the types and percentages of fillers, flame retardants, and UV stabilizers have a significant impact on the performance of elastic materials.

Note 3: Material traceability guidelines can be found in GB/T 3836.21. Manufacturers planning to use "fingerprint" methods (such as infrared scanning or oxygen index) to trace the origin of plastics will need to pay attention to this during type testing in order to obtain baseline information.

7.1.2.4Adhesive materials

The technical requirements for adhesives should include the following:

A)The name or registered trademark of the adhesive manufacturer;

B)Material identification, including model number;

C)Continuous operating temperature (COT),

Determine the data source for the above characteristics.

Note: There is no provision in this document regarding the verification of whether the adhesive meets the manufacturer's technical requirements.

7.2 thermal stability

7.2.1Thermal stability test

The heat and cold resistance tests should be carried out in accordance with 26.8 and 26.9. The experimental sequence is shown in 26.4.

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