Electrical glass failure mechanism

Glass is one of the engineer s most useful and versatile materials. There are many types of glass to choose from to provide a wide range of physical, mechanical, electrical and optical properties for practically every type of environmental condition. The transparency of glass facilitates inspection of process operations and minimises the risk of failure due to unsuspected corrosion, while the hardness and smoothness contribute to easy cleaning. 

Storage chambers should be validated with respect to their ability to maintain the desired conditions, and, if so equipped, the ability to sound an alarm if a mechanical or electrical failure causes the temperature to deviate from preestabilished limits. They should also be equipped with recording devices, which will provide a continuous and permanent history of their operation. Logbooks should be maintained and frequent readings or mercury-in-glass, National Institute of Science and Technology traceable thermometers recorded. 

Table I lists the typical physical characteristics of the new and old membranes, including a Nepton CR-61 on 9-ounce dynel which was substituted for the 9-ounce glass in production a year or two earlier. Figure 2 shows the electrical resistance of the 4-ounce and 9-ounce membranes. From Table I, it can be seen that the reduction in thickness from 30 mils to 23 mils in both the cation and anion membranes led to reduction in Mullen burst strength to 140 p.s.i. The electrical through resistance (Figure 2) was decreased to approximately two thirds for the cation membranes and about one half for the anion membrane. The Nepton CR-61 9-ounce glass membrane had a much lower resistance than the 9-ounce dynel, because of a difference in the weave pattern in the cloth, so that there was actually little if any difference between the 4-ounce dynel cation and the 9-ounce glass cation in electrical through resistance. However, the superior resistance of the dynel backing to mechanical failures leads to its selection.

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