Tank Sight Glass type 121-V | Noris

Noris Type 121-V Sight Glass for Vacuum Applications

The Noris Bauform 121-V is a specialized circular sight glass, based on DIN 28121, designed with O-ring sealing for vacuum service. It is not a level measurement device but a static visual inspection component for tanks, vessels, and silos operating under negative pressure or alternating vacuum/pressure conditions.

Technical Configuration

• Base series: Bauform 121
• Dimensional standard: similar to DIN 28121
• Sealing: O-ring for vacuum duty
• Glass: borosilicate, up to 280 °C
• Availability: all nominal diameters, pressure classes up to PN 40, and materials per series
• Application: higher vacuum integrity compared to flat gaskets

Difference from Type 121-H

Type 121-H is specified for temperatures above 200 °C using pure graphite gaskets. Type 121-V is intended for vacuum applications and utilizes an O-ring. Selection is based on primary operational requirement: thermal load or vacuum tightness.

Typical Applications

• Vacuum tanks
• Mixing vessels with suction or degassing
• Chemical and pharmaceutical processes requiring visual inspection
• Vessels where air ingress must be minimized
• Observation of foaming, color, clarity, deposits, or level

Selection Criteria

Specification must confirm DN, PN, body material, operating temperature, glass type, and O-ring compatibility with process media, cleaning agents, and thermal cycles. For chemically aggressive media, O-ring material selection is critical to prevent swelling, hardening, or loss of seal integrity.

FAQ

Is an actuator required?
No. Type 121-V is a passive component with no actuated mechanism.

When is it selected over standard Type 121?
When the installation operates under vacuum or requires enhanced air ingress prevention.

What is checked during maintenance?
O-ring, glass, protective layer, bolts, sealing surfaces, and signs of leakage after vacuum/pressure cycles.