1. Applicable Standards and Design Basis
Our GB Marine Butterfly Valves are designed and manufactured to the following core standards:

• GB/T 3036: Marine centric butterfly valve – defining design, materials, dimensions, and performance requirements.

• GB/T 2501: Marine pipe flanges – connection dimensions and sealing surfaces for PN6, PN10, and PN16.

• GB/T 600: Test and inspection of marine valves – shell strength and seat leakage test procedures.

• GB/T 3985 / GB/T 5574: EPDM and NBR rubber materials for the seat/liner, ensuring proper seawater and oil compatibility.

2. Marine-Grade Materials

• Body: Ductile iron QT400-18 or QT450-10, or stainless steel ZG0Cr18Ni9 (304 equivalent), protected by a heavy-duty two-component epoxy coating for long corrosion resistance.

• Disc: Bronze ZCuSn10Zn2, duplex stainless steel, or 316L stainless steel, selected for excellent seawater corrosion resistance.

• Seat/Liner: Vulcanized EPDM (standard for seawater and freshwater) or NBR (for oil service), extending fully across the flange face to form a built-in, gasket-free seal.

• Shaft: Stainless steel (2Cr13 or 316L) with an anti-blowout shoulder, rotating on self-lubricating, non-metallic bearings that prevent corrosion and seizure.

3. Key Technical Features

• Bubble-Tight Shutoff: Bidirectional zero-leakage sealing achieved and verified to GB/T 600 leakage rate requirements.

• Compact Face-to-Face: Short body design saves critical installation space in engine rooms, pump rooms, and skids.

• Self-Gasketing Connection: The full-face elastomer liner eliminates the need for separate flange gaskets, ensuring a perfect seal against GB-standard raised-face or flat-face flanges.

• Actuator-Ready: Top flange machined to ISO 5211 for direct mounting of manual levers, enclosed worm gearboxes, or automated actuators (electric, pneumatic, hydraulic).

• Low Maintenance: Isolated shaft bearings and corrosion-resistant materials require no lubrication and resist sticking after long idle periods.

4. Typical Marine Applications

• Main and auxiliary seawater cooling circuits

• Ballast water and bilge systems

• Firefighting and foam ring-mains

• Fuel oil and lubricating oil transfer lines

• Fresh water generators and potable water systems

• Overboard and vent lines

5. Quality Assurance, Testing, and Certification

• Testing: Every valve is subjected to a hydraulic shell test at 1.5 times the rated pressure and a seat tightness test at 1.1 times the rated pressure, in strict accordance with GB/T 600.

• Material Traceability: Full material certificates (equivalent to EN 10204 Type 3.1) are provided for all pressure-containing and wetted components.

• Class Approvals: The valves can be supplied with type approval certificates from all major classification societies (CCS, DNV, LR, BV, ABS, NK, KR, RINA) upon request. The body carries permanent markings for heat number, nominal size (DN), pressure rating (PN), material grade, and manufacturer’s identification as required by GB standards.