Tank Sight Glass type 121-A | Noris

Tank Sight Glass Noris Type 121-A

The Noris Type 121-A is a circular sight glass assembly designed for direct mounting on existing ANSI flanges. It is used for visual inspection or illumination of the interior of closed vessels, such as tanks, boilers, and silos. The unit is supplied pre-assembled and bolts directly onto the flange connection.

Technical Specifications

• Design: Similar to DIN 28121
• Connection: ANSI flange design
• Standard execution: for ANSI 150 lbs
• Operating pressure: 10 bar
• Operating temperature: up to 200 °C
• Sizes: 1½” to 8”
• Material certificates: EN 10204-2.2 or EN 10204-3.1 (optional)

Materials and Sealing

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

Configuration Options

• Special construction for temperatures above 200 °C
• Higher pressure versions
• ANSI 300 lbs or 600 lbs
• Double safety window
• Sight glass luminaire
• Base flange lining

Selection Criteria

Type 121-A is selected when the vessel is equipped with an ANSI flanged nozzle, as opposed to DIN connections. The main difference from Type 121 is the flange geometry: Type 121 is for DIN flanges, Type 121-A is for ANSI flanges.

For corrosive media or chemical environments, stainless steel 1.4571 construction is recommended. For high-temperature processes, confirm design temperature, gasket material, and PTFE compatibility with the process medium.

FAQ

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

Is it a continuous level indicator?
No. It provides direct visual confirmation of level, foaming, color, or medium condition.

What is checked during maintenance?
Glass, gaskets, bolts, tightening torque, and signs of leakage at the flange connection.