The 76-Type Fused Sight Glass is a high-strength metal-fused borosilicate sight glass disc designed specifically for welding neck flange assemblies according to DIN 28121. The glass is fused directly to a metal ring, creating a permanently integrated glass-to-metal construction for demanding industrial applications.

During manufacturing, the borosilicate glass and metal ring are heated together under controlled conditions. The glass flows against the inner surface of the metal ring and is subsequently cooled through a controlled process. This creates a compressive stress structure within the glass, improving its resistance to mechanical impact, pressure and thermal shock compared with conventional loose glass discs.

The Type 76 is designed as a direct replacement for conventional sight glass discs used in compatible DIN 28121 welding neck flange assemblies. It can be used with welding neck flanges featuring flat or raised faces, provided that the required dimensions are matched.

Standard versions are available for 16 bar and 40 bar pressure ratings, with operating temperatures generally ranging from -60°C to +300°C, depending on the selected metal ring material and operating conditions. Higher pressure and non-standard dimensions can also be evaluated according to project requirements.

The metal ring can be manufactured from S355J2+N carbon steel, Duplex stainless steel 1.4462, Hastelloy C-22, Hastelloy C-276 or Hastelloy C-4, allowing the sight glass to be selected for different chemical, temperature and corrosion conditions.

Typical applications include chemical reactors, petrochemical equipment, pressure vessels, filtration systems, mixing vessels, pharmaceutical process equipment, power generation equipment and vacuum or pressure coating systems.