Sight glasses with safety viewports of Type 585 are designed to withstand the maximum allowable pressure with only one single glass plate intact. This way, pressure containment is guaranteeed even if one of the glass plates is damaged. Between base and intermediate flange an O-Ring seal ensures tightness even if the inner glass plate has failed. Type 585 is a true safety sight glass! Material:Body made of P235GH, P265GH, 1.4404 or 1.4571Glass plates of borosilicate glass DIN7080 or soda lime glass DIN8902, quartz glass, METAGLASSeal:PTFE enveloped corrugated ring system + O-rings according to customer requirementsShape:straight flow sight glasses with security double glazingNominal size:DN50-400Nominal pressure:PN16