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||CORNING GLASS WORKS
Most of this superiority is inherent in the
glass itself. It is uniform all the way through. Chip or break a
PYREX insulator and the surface you reveal is exactly the same as
the original outer surface of the insulator. All PYREX insulators
are made in one piece, without cement or glaze.
The mechanical ruggedness of PYREX insulators
is again inherent in the glass of which they are made. All PYREX
insulators will withstand cantilever pull sufficient to bend standard
An important safeguard provided by PYREX
insulators is their high puncture voltage in air. Every PYREX
insulator rated 13 kv. or more is subjected to a continuous five
minute test at approximately 25% more than the normal dry flashover
potential. Artificial lightning surge tests have demonstrated
their ability to withstand steep wave front voltages of 1,500,000
volts--the limit of the equipment on which the tests were made.
Power arcs of 2,000 amperes or more maintained for several seconds
result only in crazing the surface of PYREX insulators to a depth
of about 1/16 inch. Their insulating value remains practically
unimpaired and the line will go back into service immediately.
The transparency of PYREX insulators--
greater than the finest plate glass--has permitted more rapid
progress in their development than could possibly have been made
with an opaque substance. At every step in their manufacture they
are visually inspected clear to the pinhole. It would be almost
impossible for any defect to go unnoticed--a fact that is well
demonstrated by the small number of failures on electrical tests;
less than one fortieth of one per cent fail to pass.
On your lines the transparency of PYREX
insulators results in the transmission of sunlight to such a degree
that even the hottest sun does not raise the temperature of the
insulator appreciably above that of the surrounding atmosphere.
Destructive stresses from sun heat and consequent line failure
are eliminated when you equip your lines with PYREX insulators.
In 44 states, Alaska, Canada, Brazil,
Mexico, Venezuela, South Africa, India, Australia and other
foreign countries, PYREX insulators are improving operating
efficiency and lowering maintenance costs.