Stainless steel flange observation window (also known as sight glass) is an observation device installed on pipelines or containers, used for real-time monitoring of internal medium flow, color changes, liquid levels, bubbles or sediments, etc. It is widely used in industries such as chemical, petroleum, pharmaceutical, food, and water treatment.
1. Structure and composition
The stainless steel flange observation window mainly consists of the following components:
Component Material/Type Function
Flange; 304/316 stainless steel (ASTM A182); Connect pipelines and provide mechanical support
Window glass; tempered borosilicate glass/quartz glass; pressure and temperature resistant, providing a transparent observation window
Sealing gasket; PTFE/silicone/graphite/metal winding gasket; prevents medium leakage
Fasteners; 304/316 bolts and nuts; fixed flanges and windows
2. Main types
According to different working conditions, stainless steel flange observation windows can be divided into the following types:
(1) Classified by structure
Single flange sight glass: single-sided flange connection, suitable for low-pressure environments (≤ 1.6MPa).
Double flange mirror: connected by flanges on both sides, with higher pressure resistance (≤ 10MPa).
Threaded connection sight glass: suitable for small-diameter (DN15-DN50) high-pressure pipelines.
Quick installation clamp sight glass: designed with hygiene standards, easy to disassemble and clean quickly (in the food/pharmaceutical industry).
(2) Classified by Function
Ordinary sight glass: only used to observe the state of the medium.
Light mirror: Built in LED light source, suitable for low light environments.
Explosion proof sight glass: Complies with ATEX/IECEx standards and is used in flammable and explosive environments.
High temperature and high pressure mirror: using quartz glass and metal sealing, with a temperature resistance of up to 1200 ℃.
3. Key performance parameters
Parameters; Standard Range; Remarks
Nominal diameter (DN); DN15-DN600 ； Beyond customization required
Pressure level; PN10-PN40（1.0-4.0MPa） ； High voltage type can reach PN100
Temperature resistance range; -30 ℃~450 ℃ (ordinary type); Quartz glass can reach 1200 ℃
Sealing grade; Zero leakage (ISO 5208 Class A); Using PTFE/metal gasket
