oven through which the ware passes at a predetermined
rate and at a controlled temperature. As a still further
precaution against strain, frequent test inspections are
made by means of polarized light. Strained glassware is
sensitive to polarized light, and an inspection of the
product in polarized light removed the hazard from the
process.
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VI THERMAL CHARACTERISTICS |
 |
The coefficient of thermal expansion is .0000032 per °C.
between 20° and 100°C. The percentage transmission
of heat rays in sunlight through 1" thickness = 96%.
 |
These thermal properties are of extreme importance in
an insulator. They enable the insulator to withstand
power arcs of great magnitude without any shattering
of the unit. In addition, Pyrex insulators do not
heat up in the sunlight. They are unaffected by
sudden atmospheric temperature changes. It is not
possible for the top side of the insulators to become
hot while the underside remains cool. Pyrex power
insulators will meet the A.I.E.E. specifications in
regard to thermal cycle tests, even though these
specifications were originally designed as protection
against poorly manufactured ware having vastly
different characteristics.
|
VII CHEMICALLY STABLE |
|
Pyrex insulators resist to a high degree the attacks
of acids and alkalies; hence there is no weathering
effect or deterioration over an indefinitely long period
of time. Pyrex Insulators clean easily under normal
rainfall and are easy to clean when forced cleaning
is necessary.
|
Pyrex suspension insulators
undergoing thermocycle test under load.
|
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