IEC Cables - SHF1 and SHF2

[NickParker]

I read that "Where a cable has both an inner and outer sheath, the class of sheathing material shall be identical".
Say, if the inner sheath of the cable is of SHF1, then the outer sheath also has to be SHF1. Why not the outer sheath be SHF2?

 

[7anoter4]

I cannot see in any known cable IEC standard such a requirement.
IEC 60502-2. 8.1.2 Material
The materials used for inner coverings and fillers shall be suitable for the operating temperature of the cable and compatible with the insulating material.
IEC 60502-1 7.1.2 Material
The materials used for inner coverings and fillers shall be suitable for the operating temperature of the cable and compatible with the insulating material.
IEC 60840 4.3 Cable oversheathing materials
The choice of the type of oversheath depends on the design of the cable and the mechanical and thermal constraints during installation and operation

 

[NickParker]

I cannot see in any known cable IEC standard such a requirement.
IEC 60502-2. 8.1.2 Material
The materials used for inner coverings and fillers shall be suitable for the operating temperature of the cable and compatible with the insulating material.
IEC 60502-1 7.1.2 Material
The materials used for inner coverings and fillers shall be suitable for the operating temperature of the cable and compatible with the insulating material.
IEC 60840 4.3 Cable oversheathing materials
The choice of the type of oversheath depends on the design of the cable and the mechanical and thermal constraints during installation and operation

This comes from the cable manufacturer catalogue,


From another manufacturer,

 

[7anoter4]

In my opinion, it is not a standard requirement but a manufacturer policy [simplifying the extrusion process or material supplier or else]