Sight Glass
Sight glass is used for transparent observation in industrial plants to monitor the level, color, flow or direction of a liquid. They are either windows installed in a piping system or a component made of a metal frame and tubular transparent glass shape that is threaded at both ends and screwed between two pipes. Tanks, boilers, tubing or piping systems, reactors or vessels may contain sight glass as liquid level gages, inline sight glass or media vessels. Also referred to as a sight window or sight port, this type of glass is used in breweries, bio gas plants, chemical plants and the pharmaceutical, food processing and beverage industries.
Manufacturers of sight glass produce plates, ingots, tubing and rods that will undergo processes such as sawing, water jets, thermal shock, scoring, breaking, glass grinding, surface polishing and edge treatments. Sight glass is strengthened by annealing, ion exchange chemical strengthening and thermal tempering. Today, glass made for sight applications is manufactured out of either soda lime, for cost effective applications, or borosilicate glass, when strength and greater coefficient of expansion is needed. The frames and bolts are generally made of stainless steel. The most modern type of sight glass is composed of a glass disc between two metal frames which are secured by bolts or gaskets or fused to the glass by heat application.