THE TELEPHONE’S FIGHT WITH GREAT SALT LAKE

Dominion, Volume 21, Issue 126, 25 February 1928, Page 24

THE TELEPHONE’S FIGHT WITH GREAT SALT LAKE

Telephoning from New York to San Francisco would be' practically impossible if the Great Salt Lake had its way.

Tlie flying salt spray, earned sometimes to a distance of fifteen miles, coats the insulators of the telephoneline with a thick crust of salt which destroys or greatly reduces their iilsullatiug properties. Each insulator has to be periodically washed to keep it in condition. How this is done without climbing poles or removing wires, bv a device invented by B. F. Howard, electrical engineer of the Mountain States Telephone Company, is told by him in a paper published originally in “The Journal” ol the American Institute of Electrical Engineers and now reprinted as a pamphlet by the Bell Telephone Laboratories (New York, 19'27). Incidentally, Mr. Howard gives an interesting account of little-known conditions on the Great Salt Lake Desert of Utah. He writes:

“In 1913, when it had been decided to construct a trans-continental teleI hone line, a warning was given by other wire-using companies of difficulties which would be encountered in the Great Salt Lake Desert, owing to very low insulation of the lines under certain weather conditions. At times they had experienced complete failure of telegiaph lines, due to this low insulation, particularly when heavy fogs prevailed. It was very important to the success of the trans-continental lines that the insulation should be prevented from falling below a certain minimum.

“For a long time these insulation conditions had existed on lines over the mud flats west of Salt Lake. The Great Salt Lake Desert is an old lake bed consisting of a deep valley filled with mud. A chemical company put a drill down at a place where the surface is covered by salt and passed through eight feet of this, 200 feet of mud, 30 feet of solid salt, and another 200 feet of mud. “The salt-bed surface is about eight miles wide and twenty long, and varies from a few inches to eight feet ill thickness. The mud flats are covered with a salty crust which, in the drv season, •is capable of carrying the weight of a horse, and has even carried a tractor; but when a hole is broken, it will rapidly fill with salt water. The melting snow and rains from the mountains run into these flats, and the surface water is blown for miles by the wind. Frequently an area that has been covered with water one day will be dry the next for miles, owing to the removal of the water by the wind during the night. “After storms, salt is sometimes found upon the windows of houses fifteen miles from the lake in Salt Lake City, where the salt-laden moisture has been deposited upon the glass. Telephone leads in the vicinity of Salt Lake Citv have had their insulation considerably lowered on account of salt and alkali dust being blown upon them.” Investigation showed that the salt is blown upoti the insulators during storms, and splashed by the action of rain This forms a crust on the surface, and when this takes place on the interior of the insulators, the insulation of the lines is materially reduced. During fogs the salt becomes wet and the resistance falls rapidly to a very low value. Mr. Howard goes on;

"The effect' of freezing is interesting. During the tests it was observed that at sunrise, after sufficient time for the insulator coating to thaw, tlie. insulation would drop materially; and then, as the warmth of the sun evaporated tlie moisture, the insulation would rise again.

It was known that this trouble was usually noticed during January, February, and March, and chiefly during the night hours. Consequently, an investigation was launched on an experimental basis.

“Tests showed how very important it was to have all glass insulators well washed and cleaned before being put in place on the poles, and that the solution of the problem was to remove the salt from time to time by washing the insulators.

“The problem of washing was a somewhat serious one, because if it were necessary to take the insulators down,, it would mean interruption to service and damage to the conductors and a long and expensive process. The author therefore devised a method by which the insulators could be successfully washed, without climbing the poles or untying the wires by spraying with saturated steam er finely divided hot water. "The steam is applied through a nozzle at the end of a fishing-rod device held under the insulator to be cleaned. The steam is generated in a portable boiler heated by an oil fire. An automatic arrangenient of pumps supplies water to the boiler to replace that which is used.

“The time necessary to wash an insulator is thirty seconds. All fresh water has to be brought by the railroad, distributed at intervals along the line, and then rolled out in barrels across the mud flats.

“During the time when an insulator is being washed, no appreciable disturbance has been noticed in the service taking place over the lines. . The rapid. ity with which salt or alkali dust, both of which are of a stubborn nature, is removed by the steam is astonishing.

“The steam washing-plant is built with wide metal tires and is pulled sometimes by horses and at other times bv a Ford car, which is also equipped with wide tires. Many miles of the mud have been found so soft that is was necessarv to lav planks in order to keep the car and the steam-generating plant from sinking.

“It has been found necessary to wash the insulators at least once every two years, but the frequency, of course, is governed by conditions of salt deposit. When the insulator resistance is found to drop to a predetermined amount, it is time to arrange for a washing of the line. While this is in process, the improvement in the insulation of the wires may be observed as the washing proceeds.

“The cost of washing the insulators on the mud flats ranges between 500 ■and 700 dollars, according to prevailing conditions.

“The illustration shows the action of the salt upon the poles above the ground line. This, at first sight, appears to be rather alarming, but it has been observed that the rending .action of the salt, which takes place as it crystallises, affects the sapwood only/?