Tank Sight Glass type 120-D-HZ | Noris

Sight Glass Noris Type 120-D-HZ

The Noris Bauform 120-D-HZ is a specialized circular tank sight glass featuring double safety glazing and integrated heating. It is designed for visual inspection of vessel interiors where the external glass surface may fog due to humidity or temperature differentials. Documentation refers to this as “safe double-vitrification” with a heating system for anti-fog operation and O-ring sealing.

Technical Configuration

• Base series: Bauform 120
• Flange dimensions: per DIN 28120
• Arrangement: double safety glass
• Heating: integrated heating element
• Sealing: O-ring
• Availability: all diameters, pressure classes, and materials of the 120 series, per technical datasheet

Operational Purpose

Double glazing provides a secondary optical barrier compared to standard Type 120. The heating element minimizes condensation on the outer glass and can reduce thermal losses at the observation point. This is relevant for hot tanks, vessels with vapor, outdoor installations, or areas with high relative humidity.

Typical Applications

• Tanks with hot liquids or condensate
• Process vessels requiring clear visual inspection
• Locations prone to glass fogging
• Applications needing additional glass protection
• Observation of foaming, level, color, deposits, or agitation

Selection Criteria

Type 120-D-HZ is selected when a standard circular sight glass Type 120 is insufficient due to fogging or double glazing requirements. Before specification, confirm DN, design pressure, body material, O-ring compatibility with process media, operating temperature, and electrical heating parameters.

FAQ

Is an actuator required?
No. The assembly has no actuation mechanism. Only electrical supply for the heating element is needed.

Is this a level measurement device?
No. It is a visual inspection component.

What is checked during maintenance?
Glass discs, O-ring, heating terminals, sealing integrity, bolts, and presence of condensate between glass layers.