1. Application
Sight glasses are installed in a wide variety of fluid systems where visual monitoring is required:

• Flow Verification: The most basic application — confirming that a pump is running, a filter is not blocked, or that flow is occurring at all. Essential on cooling water pump discharges, lubricating oil returns, and condensate lines.

• Fluid Condition Monitoring: Detecting colour changes, turbidity, emulsification, or solids carry‑over. On fuel oil lines, a sight glass shows whether fuel is clean and free of water or sludge. On lube oil returns, it reveals metal particles or foam.

• Phase Observation: Checking for air or gas bubbles in liquid lines, or condensate in steam lines. On bilge and ballast lines, confirming that the pump is primed and discharging water, not air.

• Interface Detection: On chemical and product lines, a sight glass can be used to observe the transition between different product grades during tank changes.

• Steam and Condensate Systems: With high‑temperature glass and graphite gaskets, sight glasses are used on condensate return lines to check for clear water and on steam tracing lines to verify proper drainage.

• Process Control: In pharmaceutical, food, and fine chemical production, a sight glass provides visual validation of CIP (Clean‑in‑Place) rinsing, ingredient flow, and reactor contents.

• Safety Isolation: In some cases, a sight glass with an integral wiper and light source acts as a local viewing port on vessels and tanks for operator safety.

2. Material Specifications
All materials are selected to suit the service fluid and are fully compliant with the applicable standard (ISO 12510, ISO 1106‑1, or equivalent):

• Body & Covers:

• Grey Cast Iron (ASTM A48, EN‑GJL‑250): Economy for non‑hazardous water, air, and oil at moderate temperatures. Always coated with epoxy or galvanized.

• Ductile Iron (ASTM A536, EN‑GJS‑400‑15): Higher strength and toughness for larger sizes and higher pressures.

• Cast Steel (ASTM A216 WCB, EN 1.0619): Standard for high‑pressure steam, hot oil, and fire‑safe services. Protected by marine‑grade epoxy or paint.

• Bronze/Gunmetal (CuSn10): Traditional for seawater, fuel, and fire main sight glasses. Inherently corrosion‑resistant and non‑sparking.

• Stainless Steel (AISI 316L / 1.4404, CF8M, Duplex): The premium choice for aggressive chemicals, hygienic water, high‑purity process lines, and offshore platforms. No external coating required.

• Glass Discs:

• Borosilicate glass (e.g., per ISO 3585) is the standard for all service conditions. It provides high mechanical strength, excellent resistance to thermal shock (up to ~280 °C), and good chemical durability. For extremely demanding applications, quartz glass or sapphire windows may be used.

• Toughened soda‑lime glass is acceptable for low‑pressure, moderate‑temperature services per the design code.

• All glass is edge‑ground and thermally pre‑stressed, and individually proof‑tested to a safety factor consistent with the design standard.

• Sealing Gaskets:

• EPDM for water, steam (up to 120 °C) and general use.

• NBR/Buna‑N for fuel, lubricating oil, and mineral oils.

• PTFE for aggressive chemicals and high‑temperature services.

• Graphite or mica‑reinforced gaskets for steam and fire‑safe applications.

• Fasteners: All cover bolts, nuts, and washers are stainless steel (AISI 304 or 316) to eliminate corrosion and allow easy glass replacement.

3. Technical Specifications
Our sight glasses are designed, manufactured, and tested to the most demanding international requirements:

• Applicable Standards:

• ISO 12510 — Ships and marine technology — Sight glasses.

• ISO 1106‑1 — Industrial sight flow indicators (for general process use).

• JIS F7212 — Shipbuilding — Sight glasses.

• CB/T 4224 — Marine sight glasses (China).

• For pressure‑temperature ratings where the above standards give reference, ASME B16.34 or EN 12516‑1 methodology is followed.

• Pressure Ratings: PN6, PN10, PN16, PN25, PN40 (ISO 7005‑1); Class 150, Class 300 (ASME B16.5); 5K, 10K, 16K (JIS). Higher ratings are engineered on request.

• Temperature Range: -10 °C to +280 °C with borosilicate glass and compatible gaskets. For cryogenic or very high‑temperature services, special glass and gasket materials are specified.

• Glass Configuration:

• Single‑disc: For low‑risk, non‑hazardous services.

• Double‑disc safety design: Two independent glass discs; if the outer disc is accidentally impacted, the inner disc maintains full pressure integrity. Standard for flammable or toxic fluids.

• Cylindrical/slotted glass: Provides 360° visibility in low‑pressure drain and vent lines.

• Optional Features:

• Internal wiper (manual or magnetically coupled) to clean the glass without draining the line — essential for heavy fuel oil or sludges.

• Detachable LED or low‑voltage illuminator for enhanced visibility in dark areas.

• Laminated safety glass or polycarbonate shield for impact protection.

4. Dimension Specifications
Exacting dimensional control ensures direct interchangeability and trouble‑free installation:

• Nominal Size Range: DN 15 to DN 200 (NPS ½" to 8"). Larger sizes are available for special applications.

• Flange Connection Standards: Flanges are drilled and faced to:

• DIN EN 1092‑1 (PN6, PN10, PN16, PN25, PN40)

• ASME B16.5 (Class 150, Class 300)

• JIS B2220 (5K, 10K, 16K)

• GB/T 2501 (PN6, PN10, PN16)
  Flange facings are flat‑face or raised‑face to match the piping specification.

• Face‑to‑Face Dimension: The distance between flange faces is precisely manufactured to the length specified in the applicable standard (ISO 12510, ISO 1106‑1, or JIS F7212). This ensures that a sight glass of a given size and rating will fit into an existing spool piece without any pipework modification.

• Glass Viewing Diameter: The visible glass area is optimized to give the largest possible view of the fluid stream, while retaining the full pressure‑bearing capacity required by the code.

• Tolerances: All critical dimensions — bolt circle diameter, bolt hole size, gasket seating face flatness, and glass retaining bore — are held to the tolerances specified in the relevant flange and sight glass standards.