A pioneer in the safety sight glass industry, PresSure Products Company (PPC) produces a complete line of sight glasses, fused sight glasses, sanitary sight glasses, liquid level gauges, sight flow indicators, process lights, reactors/chambers, ultrasonic stencil cleaners, and concentration monitoring systems.
The highest stress imposed on any sight glass window is at the edge of the sealing gasket. This stress is needed to cause the gasket to undergo plastic deformation to conform to its mating surfaces. This sealing stress is far in excess of any process pressure that the sight glass may experience. As this sealing stress is always imposed on the gasket and the glass, it causes the gasket to continue deforming and the glass to continue weakening; eventually, excessive deformation of the gasket will cause the gasket to become too thin, resulting in a leak. Simply compressing an already too-thin gasket will often result in damage to the sight glass. The unique design of PPC’s sight glass units eliminates such dangers and guarantees high operational safety and sealing performance under the most extreme temperature and pressure conditions.
When the packing materials that seal our sight glass windows are compressed to create the necessary plastic deformation, the sealing compression is applied to the packing material, which surrounds the side wall of the sight window. Without a direct compression path to the glass, the possibility of excessive compression of the sealing material imposing damaging stresses on the glass is greatly reduced. Process pressure, which is applied on the surfaces of the window, is decoupled from the sealing pressure, which is applied on the side walls. This decoupling enables softer, higher-temperature glassy materials such as fused quartz to be used in higher-pressure applications. And if a leak develops, further compression of the sealing material can be achieved with far less danger of damaging the glass window, and without always having to replace the sealing material—which would require taking the sight window out of service. Higher pressure and temperature ratings, along with ease of maintaining seals in the real world, are the traits of PPC’s sight glass windows.