Tank Sight Glass type 121-W | Noris

Tank Sight Glass Noris Type 121-W

The Noris Type 121-W is a circular sight glass conforming to DIN 28121, designed for installation on existing flanges. It features an integrated wiper on the internal glass surface. Based on Bauform 121, this variant is specified where process media form films, solid deposits, or clouding that restrict visual inspection.

Operating Conditions

• Nominal sizes: DN 40 to DN 200
• Standard: DIN 28121
• Connection: Bolted installation on existing flange
• Operating pressure: By agreement for 121-W version
• Standard 121 series: 10 bar or 25 bar, up to 200 °C
• Glass: Borosilicate, DIN 7080
• Seal: PTFE enveloped gasket, up to 200 °C

Wiper Blade Options

Blade selection depends on process media and temperature:

• Silicone: up to 180 °C, for liquid media
• PTFE: up to 200 °C, for media with solids or abrasive contact
• Standard: Single-arm wiper
• Optional: Double-arm wiper

Typical Applications

• Mixing tanks with foaming or product film on glass
• Silos and vessels with powders or solid particles
• Chemical processes with product deposits
• Vessels requiring inspection without opening or disassembly

Selection Criteria

Type 121-W is specified over standard Type 121 when visibility is reduced during operation. Prior to ordering, confirm DN, design pressure, flange material, blade compatibility with media, temperature, and certification requirements (EN 10204-2.2 or 3.1 for standard 121 series).

FAQ

Is an actuator required?
No. The design includes a manual internal wiper, not an automated actuator.

When is PTFE blade preferred?
For media with solids or deposits, up to 200 °C.

What is checked during maintenance?
Inspect glass, gaskets, wiper shaft, blade, bolt torque, and check for leakage at the flange connection.