UHV material processing frequently involves the introduction of gases at regulated pressures. In the event of an unintentional or inadvertent pressure burst, fragile components such as vacuum viewports are subject to damage. Whereas burst discs or pressure relief valves can mitigate risk, windows proofed to withstand such pressure can avoid catastrophic rupture in critical UHV applications.
Conflat™ flanges, the most commonly used for UHV, cannot be rated per the ASME boiler pressure vessel code. The upper limit of pressure for such flanged joints is dependent upon the system mating flange; the material and hardness of the gasket; and, the strength and torque of fasteners. The use of Conflat™ mounted, over-pressure protected viewports is not recommended for continuous or intentional use under pressure.*
Over-pressure protected viewports are fully tested at 150% of the rated pressure. For standard Conflat™ viewports, the maximum overpressure protection offered is 200 psi. The sapphire window assemblies are designed with greater than 10x safety factor and tested to 300 psi.
*For pressure applications, MPF can provide safe designs utilizing ASME B16.5 flanges. MPF has designed viewports for service up to 20 kpsi using customer specified mounts.