Sanitary Sight Glass & Hygienic Visual Inspection Ports (ASME BPE / DIN 11851)
Process visibility is critical, but the observation window is often the weakest link in a sterile loop. Standard sight glasses suffer from thermal shock failure during SIP (Steam-in-Place) cycles and gasket intrusion that creates bacterial harborages. Our Sanitary Sight Glass range helps process engineers maintain absolute system integrity. Engineered with prestressed Borosilicate Glass and housing made from forged SS316L, these components resist the delta-T of rapid heating/cooling cycles. Whether you require an Inline Sanitary Sight Glass for flow verification or a tank-mounted Hygienic Sight Window, our designs ensure zero dead legs and full drainability, preventing batch cross-contamination in high-purity Food, Beverage, and Biotech applications.
- Glass: Borosilicate 3.3 (DIN 7080).
- Housing: Forged SS316L (1.4404).
- Finish: Electropolished Ra < 0.38μm (SF1).
- Rating: -1 Bar (Vacuum) to 10 Bar.
- Temp: -30°C to +280°C (Glass dependent).
- Compliance: FDA 21 CFR & USP Class VI.
Technical Specifications
Product Name
Sanitary Sight Glass (Inline, Bullseye, Tank Mount)
Design Standards
ASME BPE-2022, DIN 11851, DIN 11864-1, ISO 2852, 3-A SSI
Metal Materials
Wetted: SS316L (1.4404 / 1.4435); Non-wetted: SS304 (1.4301)
Glass Material
Borosilicate Glass 3.3 (Metaglas® compatible), Soda-Lime (upon request)
Sealing / Gaskets
EPDM, PTFE (Teflon), FKM (Viton), Silicone (All FDA / USP Class VI)
Connection Types
Tri-Clamp (Ferrule), Butt Weld, DIN Union, Flanged, ANSI Bolt-on
Surface Finish (ID)
Mechanical Polish (Ra 0.8μm); Electropolished (Ra 0.38μm / ASME BPE SF4)
Pressure Resistance
Standard 6-10 Bar; High-Pressure fused units up to 16 Bar
Resistance to Thermal Shock:
Unlike standard soda-lime glass, our Borosilicate Glass Sight Glass units have a very low coefficient of thermal expansion ($3.3 \times 10^{-6} K^{-1}$). This prevents catastrophic failure (shattering) when the system transitions immediately from a 121°C steam sterilization cycle to a cold water rinse, a common failure mode in dairy processing.
Eliminating Biofilm Risks:
Standard viewports often have a “step” between the glass and the metal ferrule. We utilize a flush-mount design where the glass is fused or precision-compressed to the metal housing. Combined with an internal finish of Ra < 0.4μm, this prevents protein buildup and ensures the unit is fully cleanable via CIP (Clean-in-Place).
Visual Clarity for Quality Control:
For applications requiring color or turbidity monitoring, our Mirror Polished Sight Glass maximizes light transmission. We also offer Sanitary Sight Glass with LED Light attachments (cold light, IP65 rated) to illuminate dark tank interiors without adding heat that could affect sensitive cultures in biotech reactors.
Standard dimensions for ISO 2852 / ASME BPE Tri-Clamp Sight Glass.
| Nominal Size (DN/Inch) | Flange OD (A) [mm] | Total Length (L) [mm] | View Diameter (d) [mm] | Glass Thickness [mm] |
| 1.0″ (DN25) | 50.5 | 148 | 22 | 10 |
| 1.5″ (DN40) | 50.5 | 156 | 35 | 10 |
| 2.0″ (DN50) | 64.0 | 164 | 47 | 12 |
| 2.5″ (DN65) | 77.5 | 170 | 60 | 15 |
| 3.0″ (DN80) | 91.0 | 182 | 72 | 15 |
| 4.0″ (DN100) | 119.0 | 196 | 97 | 19 |
Torque Sequence: When installing a Bolted Tank Sight Glass (DIN 28120 style), do not tighten bolts in a circle. Use a “star pattern” (crisscross sequence) to apply even pressure to the glass disc. Uneven torque causes stress concentrations that lead to immediate cracking under pressure.
Gasket Selection: Ensure the gasket material matches the chemical compatibility of the fluid. Use PTFE Gaskets for aggressive CIP chemicals (Nitric Acid/Caustic Soda), but be aware that PTFE “creeps” (relaxes) over time and may require re-torquing after the first heat cycle. For strictly steam/water loops, EPDM provides better elastic recovery.
Inspection: Before every production run, visually inspect the glass surface. Even microscopic scratches on the wetted side can become nucleation sites for stress cracks or bacterial colonies. If the glass shows signs of erosion (cloudiness) from abrasive fluids, it must be replaced immediately to prevent rupture.
Related Products
FAQ
What is the difference between Borosilicate and Soda-Lime sanitary sight glass?
Borosilicate glass (used in our Premium line) has superior chemical resistance and thermal shock capabilities, handling temperature shifts up to 280°C without cracking. Soda-lime glass is a cheaper alternative suitable only for low-temperature, non-aggressive fluid applications (typically <100°C) and is prone to etching from caustic cleaning agents.
Can your Sanitary Sight Glass withstand full vacuum?
Yes, our standard Tri-Clamp Sanitary Sight Glass units are rated for full vacuum (-1 Bar) up to 10 Bar positive pressure. The structural integrity is maintained by the thickness of the glass and the precision support of the stainless steel housing, preventing the glass from being sucked into the line during vacuum pump-down.
How often should I replace the glass in a Hygienic Sight Window?
Glass is a consumable component. In high-stress environments (frequent SIP cycles or abrasive media), we recommend inspecting the glass monthly and replacing it annually or immediately if any pitting, scratches, or cloudiness is observed. A compromised glass surface reduces pressure rating and cleanability.
Do you offer 3-A or ASME BPE certified sight glasses?
Yes, our High Purity Sanitary Fittings line includes sight glasses manufactured in strict accordance with ASME BPE dimensions and 3-A Sanitary Standards. This includes specific requirements for surface finish (Ra < 0.38μm), material traceability (Mill Certs), and marking for full batch tracking in pharmaceutical validation.
What is the purpose of a Sight Flow Indicator with a rotor?
A Sanitary Sight Flow Indicator with a PTFE rotor spins when fluid moves through the pipe. This provides an immediate visual confirmation of flow for clear liquids (like WFI or solvents) where it is difficult to see movement with the naked eye. It helps operators instantly detect pump failures or blockages.