PORCELAIN INSULATORS.

Press, Volume LXI, Issue 18372, 4 May 1925, Page 13

PORCELAIN INSULATORS.

Before a meeting of the Canterbury University Oolleg® Engineering Society on Saturday night, Mr O. C. Stephens, ol X«v.Zealand Insulators, Ltd., read an interesting panel* on "Porcelain Insulators." He first dealt with the raw materials, clays, quartz, and felspars, and then detailed the •processes of manufacture of insulator porcelain. • . J - , The air-dried kail cla.v is plungsd into water and stirred until it reaches tho conwistcncy oC cream, when ground flint -jmd felspar aifl added. When the liquid is of an even tsxiuro ,it passes on to a. leaf type periodic filter press. Hero all excess moisture la expfelled and the clay is taken out in plaßtic nlip-3. From this sUrb there are threo modes of procedure:— (1) The casting slip method used for suspension typo of insulators; (2) the dry process for switch blocks; and (3) tha wet plastic process for pin tvpc insulators. . After the insulator has been formed, it ij subjected to a drying process in a humid atmospuerc, and tUo humidity is gradually rir.or*nßed nntil the slip is in the "leather hard" condition, when it is sent to the lathes and turned to tbo desired shape. It is then subjected to another drying process until it is "white hard." The next stage is to coat the insulator with a gUie material, which is of felspathic origin. fcend it to the kilns to be fired. Mr Stephens then rfp.i'.t with 'he periodic and continuous kiins. Tho T.criodic kilc3 are very inefficient in coal consumption and temperature regulation, but until the output is large it does not pay to install kilns «f the continuous type. Great caro has to be taken in the firing; both the glaze and the porcelain should mature at the same temperature, and with soma clays the firing range is only from 10de<». C. to lode?. C. JThe insulators «Te then tested for resktirity and porosity. With regard to porosity, researches in the fuchsia dye treatment have been carried out in New Zealand by Dr. Farr. Contrary to what is generally supposed, the non-porosity of th« insulators is not due to tlio glaze, whose sol® purpose is to present a smooth surface, from which dust can be washed by raiu showers.