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VIII DESIGN AND ASSEMBLY |
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The absence of cement in the one-piece pin type insulators
and also in the assembly of Pyrex suspension and strain
insulators eliminates any question of trouble arising from
its use. There is no possibility of cracking, checking,
nor change of volume with moisture content or time.
Impulse flashover on a string of
Pyrex Suspension Insulators.
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IX MANUFACTURE |
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But few steps are necessary in the manufacture of
Pyrex power insulators. Consequently, the possibility
of errors or inferior ware is greatly decreased. The
desired shapes are accurately moulded by pressing the
glass in highly polished metal moulds. No further
finishing operations are necessary. Controlled annealing
and inspections follow. There is no warpage or shrinkage
in the finished product.
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X ELECTRICAL CHARACTERISTICS |
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Pyrex insulators have a high dielectric strength and
a low dielectric constant and power factor. They have
a favorable volume and surface resistivity. They
resist power arcs to a high degree.
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XI MECHANICAL CHARACTERISTICS |
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Pyrex insulators offer a high surface hardness and the
units are not readily scratched. Pyrex pin type insulators
have a cantilever strength sufficient to bend any standard
service pin. The suspension insulators have a tensile
strength far in excess of the hardware used. Laboratory
tests as well as reports from operating companies indicate
satisfactory resistance to breakage from handling or from
mechanical impacts.
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XII TESTS |
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Pyrex suspension insulators will meet all requirements
covered by A.I.E.E. specifications No. 41, dated March
1930. After manufacture, all Pyrex suspension insulator
shells are carefully inspected and receive vigorous routine
flashovers. Following assembly, each Pyrex suspension
and strain insulator receives a routine mechanical and
electrical test of 40% of its rated strength for five
minutes.
All of these advantages, combined
with fundamentally sound and proven design principles
unite to produce economy for the user. They point to
longer continuous service under normal conditions, and
also to a better withstanding of abnormal conditions
of service such as inevitably occur. They therefore,
result in lower costs and better service records.
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