Has anyone seen the practice of grounding the metal cover of pipeline insulation layers?

According to the GB/T 20675-1990 standard you mentioned, metal protective covers for air ducts and insulation layers are usually made of thin metal sheets and connected either by soldering or by mechanical fastening with bolts. Although the standards describe in detail the method of connecting the metal plates, they do not explicitly state that the protective cover needs to be grounded. Generally, grounding a metal enclosure or cover is primarily for safety reasons, especially in cases where electrical faults may cause the metal enclosure to become charged. In specific environments, such as those with flammable gases or high levels of electromagnetic interference, grounding may be even more important to prevent the accumulation of static electricity or electromagnetic interference. Although the metal exterior of insulation layers is not commonly used for grounding purposes, from a safety perspective, grounding is a good preventive measure. If there are specific safety requirements or standard recommendations for grounding, it is best to follow these guidelines. .

Special equipment pressure pipelines are used in industrial pipelines

It is strictly prohibited to use metal hoses, the metal outer layer of pipe insulation, metal mesh, the lead coating of low-voltage lighting wires, or the metal sheath of cables as grounding wires. This means that if someone uses the metal casing as a ground wire, then that casing itself should be grounded. It can only be determined from this perspective that grounding is necessary. No other provisions that provide direct support have been found for the time being.

This casing cannot be used as a ground wire

Yes, based on this indirect indication, the metal outer layer of the pipeline insulation must be grounded, but it cannot be used as a grounding wire.