Tank Sight Glass type 121-H | Noris

Noris Type 121-H Sight Glass for Temperatures Above 200 °C

The Noris Bauform 121-H is a circular sight glass engineered to DIN 28121 for applications where the standard Type 121 is unsuitable due to elevated temperatures. While the standard DIN 28121 series is limited to 200 °C, the Type 121-H utilizes pure graphite gaskets for sealing, enabling operation under higher thermal loads.

Operating Conditions

• Dimensional standard: DIN 28121
• Service: temperatures >200 °C
• Sealing: graphite gasket / pure graphite
• Glass: borosilicate up to 280 °C
• Optional: quartz glass up to 1000 °C
• Availability: all pipe diameters, all nominal pressure classes, and all materials of the corresponding series

Difference from Type 121

Standard Type 121 is used for flanged sight glasses to DIN 28121 up to 200 °C. Type 121-H retains the same geometry but replaces the sealing system with graphite to withstand higher temperatures at the observation point.

Typical Applications

• Hot process tanks
• Vessels with steam or thermal oil
• Systems requiring visual inspection above 200 °C
• Observation of foaming, color, level, purity, or deposits

Selection Criteria

Type 121-H selection should be based on design temperature, DN, nominal pressure, body material, glass material, and graphite compatibility with the process medium. For vacuum applications, the related O-ring version, Bauform 121-V, is referenced in the same technical data sheet as suitable for higher vacuum service.

FAQ

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

When is quartz glass selected?
When process temperature exceeds borosilicate limits and resistance up to 1000 °C is required.

What is checked during maintenance?
Glass, graphite gaskets, bolts, sealing surfaces, and signs of leakage after thermal cycling.