The constituent parts of the insulators

a) the dielectric of toughened glass

Its electrical qualities derive from its chemical composition which was chosen to obtain an insulator having great dielectrical rigidity under impulse waves and industrial frequency voltage, even in those parts of the globe having extreme climates.


Automatic control of the glass chemical composition

Figure 1 shows the lay-out of the continuous production line of the dielectrics. The raw materials are chosen as a function of their composition, and the regularity of same, which is checked periodically by chemical and granulometric analyses. The raw materials are mixed in predetermined proportions which are checked thanks to the automatic installation shown in Figure 2. Besides the regular chemical analyses, the regularity of the batch and the homogeneity of the glass prepared in the furnace are checked daily by very precise densimetric measurements.

Toughening gives to the glass a very great mechanical resistance which is used all the better when they have a carefully determined shape. The shape and the mechanical resistance of the glass are checked by means applied as soon as its temperature permits. The observations are analysed by the control chart method. Routine tests complement the statistical checks: a cold-hot thermal shock eliminates pieces with heterogeneities and a hot-cold thermal shock has as its aim the destruction of those glass units having improper thermal stresses. Finally each piece undergoes a visual examination designed to eliminate those having defects, internal or external, visible to the naked eye.