DIN 28121 Circular Sight Glass Fitting

John Moncrieff’s DIN 28121 circular sight glass fittings are precision-manufactured assemblies designed for bolting directly onto existing flanged nozzles, weld pads, and vessel outlets. Built to the exact construction requirements of DIN 28121, each unit is supplied as a fully pre-assembled, gasketed, and securely bolted sight glass package—ready for straightforward installation with no on-site glass handling.

The paired retaining flanges firmly clamp a high-clarity sight glass disc between two matched seals, ensuring excellent mechanical stability, leak-tight performance, and reliable process visibility across a wide range of industrial applications including tanks, reactors, pressure vessels, silos, separators, and pipelines.

Key Features

• DIN 28121-Compliant Design: Fully pre-assembled and factory-tightened for immediate installation.
• Direct Bolt-On Assembly: Circular flange set designed to mount onto existing flanged nozzles and pads.
• Complete Package: Supplied with a fully gasketed glass disc, seals, and paired flanges.
• Nominal Sizes: DN 40 to DN 200.
• Viewing Diameters: 48 mm to 150 mm.
• Temperature Rating: Up to 200 °C (higher ratings available upon request).
• Pressure Rating: Suitable for operating pressures up to 25 bar.
• Material Options: Stainless steel, carbon steel, and special alloys such as Hastelloy.
• Custom Builds: Engineered variations available to meet specific process and dimensional requirements.

Typical Applications

• Pressure vessels and process tanks
• Silos and storage systems
• Stirred and agitated vessels
• Mixers, separators, and filtration units
• Pipelines requiring clear visual inspection

When a robust, compliant, and installation-ready sight glass is required, John Moncrieff’s DIN 28121 circular fittings provide a proven, high-performance solution for clear and reliable process observation.

Technical Specifications: