Pin insulator

Insulator of a telephone transmission line

A pin insulator consists of a non-conducting material such as porcelain, glass, plastic, polymer, or wood that is formed into a shape that will isolate a wire from a physical support (or "pin") on a telegraph, utility pole or other structure, providing a means to hold the insulator to the pin and secure the conductor to the insulator. Unlike a strain insulator, the pin insulator is directly connected to the supporting pole.

Pin insulators were utilized before 1830, pre-dating the strain insulator. Production of pin insulators is continued today by manufacturers worldwide.

The pin insulator is designed to allow the conductor to be readily secured to avoid it coming adrift. The most common method is to use a wire to tie the conductor to the insulator. Another method is to provide self-fixing features such as complex slots and grooves formed into the insulator. For heavy conductors, gravity can be used to help hold the conductor in place.

Pin insulators are almost always deployed in the open air, so isolation when wet is a major consideration. To combat this problem they have smooth surfaces and deep skirts or wide shells. These help shed water and increase the surface distance between the conductor and the pin.

The "pin" is typically a wooden or metal dowel of about 3 cm diameter with screw threads. The pin insulator has threads so that it can be screwed onto the pin. A typical pin insulator is more than 10 cm in diameter and weighs one kg or more. Size depends on the voltage to be isolated and the weight of span of wire to be supported.

Collecting

Pin insulators are collectible items. All glass pin-type insulators have been assigned a Consolidated Design number, or CD number. This system was first implemented in 1954 by hobbyist N.R. Woodward.[1] The CD numbers are hobby-specific for collectors, and are not recognized by insulator manufacturers.

Some people collect insulators made only by a certain company that (along with bottles and other glass items) made insulators. Some collectors try to obtain one of each of the variety of interesting shapes. These shapes have been categorized into a system attributing a "Consolidated Design" (CD) number to each style.

There are some clubs dedicated to collecting pin insulator due to there part in technology advancement, http://www.insulators.info/clubs/ is a list of US clubs by state.

Insulators, at the time they were being produced, were viewed simply as another tool and were not meant for spectator analysis. Therefore, the production of insulators was not usually the prime concern of the glass companies that made them. These glass items were commonly "sideline" products. Quality control was not always an important concern.

Companies melted glass and poured it into metal molds to make insulators. The temperature of melted/liquid glass is so high that many foreign objects introduced into the molten glass melt down and diffuse through the "batch." Upon cooling, the impurities cause a discoloration in the finished item. Today, many collectors thrill to this lack of quality control since impurities (adding a unique character) make a prized possession from what would normally be a common, low valued insulator.[2] UFO's (Unidentified Floating Objects), amber swirls; "milk" swirls; graphite inclusions; two or three-tone insulators; and (rarely) identifiable objects such as nails, pennies, screws, etc., are known to be imprisoned within the glass of an insulator.

Although the majority of collectors collect mainly glass insulators, there are a number of people who collect porcelain ones as well. These also come in a vast variety of shapes, sizes, and colors.

Companies

A sparkling CD145 or "beehive" insulator, from the telegraph era, made by the Brookfield Glass Company circa 1882
The same snowy CREB 145 sitting on its side

Possibly the company that produced the most glass insulators during the 19th century and early 20th century in the USA was the Brookfield Glass Company.[3] Brookfield may have had a poor quality control as Brookfield insulators seem most prone to be found with imperfections such as swirls.

The Hemingray Glass Company[4] probably made the most variety of colors. A small sampling of colors which this company's produced are yellow, golden yellow, butterscotch, glowing orange, amber, whiskey amber, "root beer" amber, orange-amber, red-amber, oxblood, green, lime green, sage green, depression green, emerald green, olive green, yellow-olive green, aqua, cornflower blue, electric blue, cobalt blue, sapphire blue, glowing peacock blue, and many, many others. These were not produced for their beautiful colors. Rather, the company made these colors so two (or more) companies with their lines strung along the same set of poles would be able to quickly identify which line was theirs by the color of insulator used on those lines. One company may have a string of amber insulators, while another, on the same poles, might have theirs in cobalt blue. They probably had no idea that, close to a hundred years later, these colors would be a main reason why people would collect/display these brightly colored pieces of glass.

Other names of U.S. companies that can be found embossed on insulators (and by no means a comprehensive listing) include AT&T, American Insulator, Armstrong, Brookfield, California, Good, Hawley, King City Glass Works (K.C.G.W.), Kerr, Lynchburg, McLaughlin, N.E.G.M. Co., Ohio Valley Glass Company (O.V.G.C.), Pyrex, Sterling, Twiggs, Western Flint Glass, and Whitall Tatum. Canadian companies included Diamond, Dominion, Hamilton Glass Works, G.N.W.TEL. Co. and others. Other manufacturers include Telgraficos Nacionales (Mexico), Zicme (South America), Miva (Italy), Isorex (France), Agee (Australia), and many more.

References

  1. ↑ "2012 NIA Hall of Fame Inductee, Nathan R. Woodward". nia.org. Retrieved 4 May 2016.
  2. ↑ "A History and Guide to North American Pintype Insulators". Retrieved 3 May 2016.
  3. ↑ "Brookfield Glass Company". www.glassbottlemarks.com. Retrieved 4 May 2016.
  4. ↑ "Hemingray Glass Company". www.glassbottlemarks.com. Retrieved 4 May 2016.
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