[Trade Journal]
Publication: Railway Signaling and Communications
Chicago, IL, United States
vol. 25, no. 9, p. 283,286, col. 1,1
What's the
Answer?
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Insulators
"What are the advantages or disadvantages of using glass insulators, as compared with porcelain insulators, for signal-control open-line circuits ? For a-c. power lines up to 440 volts ?"
Brown Glass Insulators Now Available
M. K. Holmes
Chief Engineer, Hemingray Glass Co., Muncie, Ind.
In our opinion glass insulators are particularly advantageous for this use on account of their durability and economy. Brown porcelain insulators have been used for this purpose in some cases, on account of a Western Union ruling that in joint construction insulators should be used sufficiently different in appearance to distinguish the power lines from the telegraph lines.
It is now, however, possible to obtain brown glass insulators which qualify under this ruling and which make the expense of brown porcelain insulators unnecessary. Brown glass insulators are particularly adaptable to this requirement. These insulators are made of a glass which is well annealed and free from internal strain, thus giving the glass more resistance to breakage. The petticoats in this insulator are heavier and on comparative impact tests this type shows materially more strength than corresponding porcelain or glass types.
