Tank Sight Glass - Fittings - 121 | Noris Armaturen

Tank Sight Glass Noris Type 121

The Noris Type 121 is a circular sight glass fitting per DIN 28121, designed for installation on existing DIN flanges. It is supplied pre-assembled and is bolted directly to the vessel’s flanged nozzle, with no welding required during installation.

Operating Conditions

• Operating pressure: 10 bar or 25 bar
• Nominal sizes: DN 40 to DN 200
• Operating temperature: up to 200 °C
• Standard: DIN 28121
• Connection: flanged, for existing DIN flanges
• Optional certificates: EN 10204-2.2 or EN 10204-3.1

Materials and Sealing

Body and cover are available in carbon steel or stainless steel 1.4571; other materials on request. Glass is borosilicate per DIN 7080. Sealing is achieved with a PTFE enveloped gasket, suitable for up to 200 °C.

Configuration Options

• Grooved or tongue flanges
• Special design for temperatures above 200 °C
• Larger sizes, e.g. DN 250
• Double safety window
• Sight glass luminaire
• Base flange lining
• ANSI flange connection

Typical Applications

Used on closed vessels, tanks, boilers, and silos for visual inspection or interior illumination. Suitable for local level monitoring, foam detection, product color, agitation, sediment, and media cleanliness assessment.

Selection Criteria

Type 121 is selected where a flanged nozzle exists and a sight glass for 10 or 25 bar is required. For corrosive or hot media, stainless steel construction, gasket type, design temperature, and media compatibility must be evaluated.

FAQ

Is an actuator required?
No. This is a static inspection component.

How does it differ from welded Types 118/119/120?
Type 121 is mounted on an existing DIN flange; other types have a welded base.

What is checked during maintenance?
Glass condition, gasket integrity, bolt torque, and signs of leakage at the flange connection.