Classify the different types of insulating materials with reference to their limiting safe temperatures for use.
On the basis of insulating materials and their limiting safe temperatures utilization, classification is as follows:
|
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.
|