Cleaning Insulators

Cleaning Insulators

Field experience in cleaning insulators indicates that no general solvent can be recommended for all cases, and that the character of the deposit must be taken into consideration.

Cemented deposits, such as Portland cement dust, calcium sulphate, and calcium-carbonate deposits have been loosened by cold soaking for 24 hours in ammonium acetate solution (10 ounces per gallon), or in sodium hyposulphate solution (two pounds per gallon). The film of zinc oxide was removed from the galvanized parts by these solutions but the life of the galvanizing was not seriously reduced. To prevent penetration of the solvents into the cemented joints, it is necessary to coat them thoroughly with hard petrolatum or a coat of melted paraffin or asphalt before starting the soaking treatment.

Tightly cemented deposits have been treated with hydrochloric acid diluted with water to give solutions ranging from 10 to 50% concentration.

Railway and industrial soot can be loosened by soaking for ten minutes to an hour in a cold solution containing from 4 to 16 ounces per gallon of Oakite No. 31, a slightly acid preparation that contains an inhibitor to prevent the attack of metal parts. The use of a wire scrub brush followed by a thorough rinsing is the general practice. In some instances depostis of this nature are not readily softened in the cold solution, and treatment with Oakite Text X is used in solution of one pound per gallon at room temperatures up to 175º F. The insulators are immersed for 40 seconds in the hot solution and then plungeed directly into cold water for rinsing and brushing.

Neither of the solutions just mentioned attacks the metal fittings, and the mechanical strength of the joints is not reduced even after several treatments. With the cold solution, melted paraffin may be used to protect the cement. For the hot treatment an asphalt with a softening point above 200º F is suggested.

Hydroflouric acid and its compounds are usually to be avoided, for the flourine attacks the glaze of the insulator and is also very dangerous to the operator. — Electrical Digest.