1. Application
Marine Cast Iron Sight Glasses are installed throughout the vessel wherever reliable visual flow monitoring is required:

• Fuel Oil Systems: On the discharge side of purifiers and before the engine inlet, to confirm a clean, bubble‑free fuel supply and to immediately detect any water or sludge carry‑over.

• Lubricating Oil Systems: In the return lines of main engines, auxiliary diesels, and stern tubes to verify continuous oil flow, check oil clarity, and spot any signs of emulsification or metallic particles.

• Seawater and Freshwater Cooling: Mounted on pump discharges and heat exchanger outlets to provide instant visual confirmation of cooling water flow — often a classification society rule requirement for essential cooling water systems.

• Condensate and Boiler Feedwater: To monitor condensate clarity, detect oil contamination, and ensure proper return flow to the boiler or feed tank.

• Bilge and Ballast Systems: Used to observe pump priming, verify that bilge water is being discharged overboard via the oily water separator, and check for blockages.

• Cargo and Tank Cleaning Lines: On product tankers, sight glasses at deck manifolds allow observation of product grade changes and flow direction.

2. Material Specifications
All materials are selected in strict accordance with ISO 12510 (or equivalent) and the specific shipboard fluid:

• Body & Covers:

• Grey Cast Iron (EN‑GJL‑250, ASTM A48 Class 30, FC200): The economical standard for moderate pressures. Its graphite flake structure provides excellent vibration damping, making it ideal for engine‑room installations.

• Ductile Iron (EN‑GJS‑400‑15, ASTM A536 Grade 65‑45‑12, FCD400): Specified where higher strength, impact resistance, or larger sizes are required. Ductile iron provides a larger safety margin without a significant cost increase.

• Both materials are protected internally and externally by a high‑build, two‑component marine epoxy coating (minimum 250 µm DFT) or hot‑dip galvanizing to ISO 1461, providing long‑term resistance to salt spray and humidity.

• Flat Glass Discs:

• Borosilicate glass per ISO 3585 is standard. It combines high mechanical strength with excellent thermal shock resistance and can safely operate up to 280 °C. For moderate‑temperature services, toughened soda‑lime glass may be used. Each disc is edge‑ground, thermally pre‑stressed, and individually proof‑tested.

• Sealing Gaskets:

• EPDM for seawater, freshwater, and low‑temperature steam (up to ~120 °C).

• NBR (Buna‑N) for fuel oil and lubricating oil.

• PTFE for higher temperatures and aggressive chemical compatibility.

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

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

3. Technical Specifications
Our Marine Cast Iron Sight Glasses are designed, manufactured, and tested to meet the rigorous demands of shipboard service:

• Design Standards: ISO 12510 (flat glass type), JIS F7212, CB/T 4224. For pressure–temperature ratings, the methodology of ASME B16.34 or EN 12516‑1 is applied.

• Pressure Ratings: PN6, PN10, PN16, PN25 (ISO); Class 150, Class 300 (ASME B16.5); 5K, 10K, 16K (JIS). Higher ratings are achievable with ductile iron bodies.

• Temperature Range: -10 °C to +280 °C with borosilicate glass and appropriately selected gaskets.

• Glass Configuration:

• Single Flat Glass: Suitable for non‑hazardous, low‑risk services where space is limited.

• Double Flat Glass (Safety Design): Two independent glass discs. If the outer disc suffers accidental impact, the inner disc maintains full system pressure integrity. This is the standard for fuel oil, hot water, and other hazardous fluids.

• Optional Features: An internal wiper (manually operated or magnetically coupled) allows the glass to be cleaned while the system is in service — essential for heavy fuel oil. A detachable LED illuminator can be fitted for enhanced visibility in dark bilge and engine‑room areas.

• Testing and Certification:

• Every body is hydrostatically shell‑tested at 1.5 times the rated pressure.

• The glass seating area is leak‑tested at the full rated pressure.

• Each glass disc is individually proof‑tested to the safety factor required by the design code.

• Full EN 10204 Type 3.1 material certificates are supplied for body, glass, gaskets, and bolting.

• Type approval or conformity certificates from all major IACS classification societies are available on request.

4. Dimension Specifications
Exacting dimensional control guarantees direct interchangeability with existing shipboard spool pieces:

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

• Flange Connection Standards: Flanges are drilled and faced to match your vessel’s piping specification:

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

• 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 as required.

• Face‑to‑Face Dimension: The body length between flange faces is manufactured precisely to the dimensions given in ISO 12510, JIS F7212, or CB/T 4224. This ensures a bolt‑for‑bolt fit into an existing pipe spool without any on‑board modification.

• Glass Viewing Diameter: The clear glass area is maximised for each pipe size to give the best possible view of the fluid, while still satisfying the full rated pressure‑bearing requirements.

• Tolerances: All critical machined dimensions — bolt circle, bolt hole diameter, gasket seating face flatness, and glass retaining bore — are held to the strict tolerances mandated by the applicable flange and sight glass standards.