Class

Maximum working temperature

Materials or Combination of materials

Y

900C

Cotton, paper, silk, press board,

PVC with or without plasticiser, wood and vulcanised natural rubber.

A

1050C

Cotton, silk and paper while immersed or impregnated in a liquid dielectric as oil.

E

1200C

Materials possessing a degree of thermal stability permitting them to be operated at temperature 150C higher than class A materials.

B

1300C

Mica, asbestos and glass fibre with appropriate bonding substances.

 F

1550C

Mica, asbestos and glass fibre with appropriate bonding substances including other materials, not essentially inorganic, that by experience or accepted test can be demonstrated to be able of operation at 1550C.

H

1800C

Materials as silicon elastomer and combinations of materials, as mica, asbestos and glass fibre, with appropriate bonding substances as suitable silicon resins.

C

above 1800C

Mica, glass, porcelain and quartz along with or without an inorganic binder.