Since it was developed in the 1970s, Metaglas has been known as the safest sight glass in the world. A number of chemical and manufacturing companies collaborated to create Metaglas, and to establish the standard with which it complies and by which all other sight glass is measured, a standard now called DIN7079.
Metaglas was created to improve safety conditions within plants that handled corrosive chemicals, chemicals worked at high temperatures and those worked under high pressures. The safety concerns became serious enough that competing companies joined forces to create Metaglas.
How It Is Made
Metaglas products are made by melting glass inside a circular metal frame, thereby fusing the glass and metal. As the glass cools and solidifies, the difference in the linear coefficient of thermal expansion between glass and metal creates a uniform compressive stress throughout the glass. The glass prevents the metal ring from shrinking back to its theoretical size upon cooling and it remains in tension.
The high degree of mechanically induced compressive stress caused by this physical relationship between the metal and glass makes Metaglas the strongest and most secure glass for sight window or visual flow indicator applications.
Even at the most extreme temperatures (as high as 536° F) or in overpressure situations, sudden, total failure – that involves explosive shattering of the glass – has never been reported.