Pressure glass windows are made in a range of glasses and to specific specifications. They are used in high pressure vacuum environments in technical instrumentation, scientific apparatus, deep sea underwater cameras and pressure vessels widely used in the chemical and oil industries.

The material properties of the glass selected will have to be considered when making your choice for a pressure window. There are formulas available for calculating the strength and thickness of the window when it is under vacuum or high pressure calculated for circular, square or rectangular windows.

Factors to be considered in determining the thickness include:

• Working Temperature
• Pressures (bar) to each side of window
• Supported area
• Usable clear aperture
• Safety Factor

Precision pressure windows are made to very tight tolerances for inspection, flame proof applications, pressure vessels, specialist cameras, observation windows, safety window and viewing windows.

Great care and attention in the fabrication of surfaces and edges must be considered. In some situations the pressures are so intense any defect in the edge or surface can cause a failure. The mechanical strength of the window must be calculated to a good safety factor and the pressure windows given a good inspection.

Pressure window materials include toughened glass, borosilicates, optical glasses, float glass, fused silica, fused quartz and sapphire. Details of these glasses can be seen on materials page.

Pressure Window Mounting

When mounting under pressure the usual method is to clamp the joint area between semi rigid gaskets. When the temperature change is likely both the clamping pressure and gasket material must be such as to permit the window to slide in relation to the metal framework. This is to allow for differential thermal expansion. When temperatures allow it may be safer to use an ‘o’ ring seal, as high spots on a gasket can cause high local stresses resulting in breakage of the window.