Page 38 - Offshore Electrical Engineering Manual

P. 38

CHAPTER

Insulation and 1

Temperature Ratings of

Equipment

INSULATING MATERIALS
Insulating materials may be grouped into classes according to their properties and the
working temperature for which they are suitable. Further information is available in
BS EN 60085:2004. The main insulation classes in use today are listed below:

1. Class A insulation consists of materials such as cotton, silk and paper when suit-
ably impregnated or coated or when immersed in a dielectric liquid such as oil.
Other materials or combinations of materials may be utilised for this class if by
experience or tests they can be shown to be capable of operation at the Class A
temperature.
2. Class E insulation consists of materials or combinations of materials which
by experience or testing can be shown to be capable of operation at the Class
E temperature; i.e., materials possessing a degree of thermal stability allow-
ing them to be operated at a temperature 15°C higher than that for Class A
materials.
3. Class B insulation consists of materials or combinations of materials such as
mica, glass fibre etc., with suitable bonding, impregnating or coating substances.
Other materials or combinations of materials, not necessarily inorganic, may be
included in this class if by experience or testing they can be shown to be capable
of operation at the Class B temperature.
4. Class F insulation consists of materials or combinations of materials such as
mica, glass fibre, etc., with suitable bonding, impregnating or coating sub-
stances. This class also includes other materials or combinations of materials,
not necessarily inorganic, which by experience or testing can be shown to be
capable of operation at the Class F temperature; i.e., materials possessing a
degree of thermal stability allowing them to be operated at a temperature 25°C
higher than that for Class B materials.
5. Class H insulation consists of materials such as silicone elastomer and combina-
tions of materials such as mica, glass fibre etc., with suitable bonding, impreg-
nating or coating substances, such as appropriate silicone resins. Other materials
or combinations of materials may be included in this class if by experience or
testing they can be shown to be capable of operating at the Class H temperature;
i.e., materials possessing a degree of thermal stability allowing them to be oper-
ated at a temperature 25°C higher than that for Class F materials.

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