III. Feature Description

A. Trunnion Mounted Design: Stability in High Pressure

• Pressure Force Distribution: Fluid pressure acts on the ball, but trunnions transfer these forces to robust bearings—preventing the ball from shifting into the valve seats. This eliminates seat deformation, a common issue in floating ball valves that increases operational torque and shortens seal life. In a DN350 Class 600 natural gas pipeline, this design maintains consistent sealing for 8–12 years, compared to 3–5 years for floating ball alternatives.
• Low Operational Torque: Trunnion support reduces friction between the ball and seats, lowering torque requirements by 40–50% compared to floating ball valves. A DN350 worm gear-operated model requires only 120 N·m of torque to operate—enabling manual control without specialized tools, even in high-pressure Class 600 systems.
• High-Pressure Resilience: The trunnion structure withstands Class 150-600 pressures without structural failure. In an offshore oil wellhead (Class 600), the valve handles 15MPa pressure spikes without leakage, outperforming floating ball valves that risk seat damage under such extreme conditions.

B. Carbon Steel Construction: Durability & Cost-Effectiveness

• High-Pressure Strength: Forged A105 and cast WCB carbon steel offer superior tensile and yield strength compared to low-grade materials, making them suitable for Class 150-600 high-pressure applications. In hydrostatic testing, the A105 body withstands 1.5× Class 600 pressure (22.5MPa) without deformation—ensuring safety in over-pressure scenarios (e.g., pump surges, pipeline blockages).
• Cost-Effectiveness: Carbon steel is more affordable than stainless steel (e.g., 304/316) while delivering comparable strength in non-corrosive oil & gas media. For large-scale oil pipeline projects with 100+ DN350 valves, this translates to 30–40% cost savings without compromising performance.
• Thermal Stability: Carbon steel retains its mechanical properties up to 425℃, making it suitable for heated media applications (e.g., crude oil heating systems, process steam lines) where lower-grade materials would soften or deform.
• Machinability & Weldability: A105/WCB’s excellent machinability enables precision CNC machining of critical surfaces (flanges, trunnion seats), ensuring dimensional accuracy. Its weldability allows for on-site modifications or repairs—critical for remote pipeline installations where valve replacement is time-consuming and costly.

C. Hard-Seal Performance: Reliability in Harsh Media

• High-Temperature Compatibility: Stellite 6 hard-facing retains its hardness (≥58 HRC) up to 425℃, making the valve suitable for high-temperature media (e.g., heated crude oil, natural gas, industrial steam) where soft seals (PTFE) would degrade rapidly. In a refinery’s hot oil line (380℃), the hard-seal valve operated reliably for 10 years, while a soft-sealed valve required quarterly seat replacements.
• Abrasive Media Resistance: The hard-sealed surface resists wear from particulate-laden media (e.g., natural gas with sand, crude oil with sediment). In a rural natural gas pipeline with fine dust particles, the valve withstood abrasive wear for 8 years, outperforming soft-sealed valves that failed within 2 years.
• Leak-Tight Sealing: The precision-ground metal-to-metal seal achieves ANSI/FCI Class IV leakage performance (≤0.1×DN mm³/min for gas), preventing fugitive emissions of oil and natural gas. This compliance with environmental regulations (e.g., EPA Methane Rules, EU Industrial Emissions Directive) avoids costly fines and reduces safety risks in residential or industrial areas.

D. Flanged Connection: Secure Installation & Maintenance Ease

• Leak-Tight Sealing: Bolted flanges distribute clamping force evenly across the gasket, ensuring a secure seal even under vibration or pressure fluctuations. In a DN350 oil pipeline, this design prevented fugitive emissions of crude oil, meeting strict safety standards for pipeline operations.
• Easy Installation & Retrofit: Flanges align with standard pipeline components, reducing installation time by 30% compared to welded valves. When upgrading an existing natural gas line, the valve can be installed without cutting the pipeline—minimizing downtime for utilities or oil & gas operators.
• Simplified Maintenance: Flanged valves can be disassembled for seat replacement or stem packing adjustment without removing the valve from the pipeline. In a refinery, this reduced maintenance time for DN350 valves from 8 hours (welded valves) to 2 hours—critical for continuous-process operations where unplanned downtime costs thousands of dollars per hour.

E. Multi-Drive Adaptability: Flexibility for Diverse Operations

• Manual Operation: Worm gear operators enable easy manual control of DN350 valves, ideal for remote pipeline sections or low-frequency use (e.g., emergency isolation in natural gas storage facilities). The ergonomic handwheel and 90-degree rotation reduce operator fatigue.
• Pneumatic Actuation: Spring-return pneumatic actuators provide critical fail-safe operation—auto-closing the valve if air supply fails, a non-negotiable feature for oil & gas pipelines where uncontrolled media release poses severe safety and environmental risks. Double-acting pneumatic actuators offer rapid cycle times for high-frequency applications (e.g., refinery process lines).
• Electric Actuation: Electric actuators with remote control capabilities integrate seamlessly with SCADA/DCS systems, enabling centralized monitoring and control. For cross-country oil pipelines or large refineries, this eliminates the need for on-site operators, reducing labor costs and safety risks associated with manual intervention.

IV. Manufacturing Processes

A. Material Inspection & Preparation

• Carbon Steel Verification: A105/WCB carbon steel billets are tested via spectral analysis to confirm chemical composition (C: 0.25–0.35% for A105, C: 0.25–0.35% for WCB) and ultrasonic testing (UT) to detect internal defects (porosity, cracks, inclusions). Mechanical testing (tensile strength, impact resistance, hardness) ensures compliance with ASTM standards, with results documented in Material Test Reports (MTRs) for full traceability.
• Heat Treatment: A105 billets undergo normalizing (900–950℃, air-cooled) to relieve forging stresses and improve machinability. WCB castings undergo annealing (850–900℃, slow-cooled) to reduce brittleness and enhance ductility.
• Hard-Seal Material Validation: Stellite 6 alloy is tested for hardness (≥58 HRC) via Rockwell testing and chemical composition (Co: 50–60%, Cr: 25–30%) to ensure wear resistance in abrasive oil & gas media.

B. Valve Body & Ball Fabrication

• Body Manufacturing: A105 valve bodies are produced via forging (for Class 300-600) to ensure material density and structural integrity—forging eliminates internal porosity, critical for ultra-high-pressure service. WCB bodies are produced via precision casting (for Class 150-300) to offer cost-effectiveness for medium-pressure applications. Forged/cast blanks are cleaned via shot blasting to remove scale and surface impurities.
• CNC Machining: Critical surfaces—flange faces, trunnion bearings, and seat pockets—are machined using 5-axis CNC centers. Flange faces are machined to ASME B16.5 flatness (≤0.05mm/m) and surface finish (Ra ≤3.2μm) for proper gasket seating. Trunnion seats are machined to a tolerance of ±0.02mm to ensure proper ball alignment. The valve’s internal flow path is polished to reduce friction and minimize pressure drop.
• Ball & Trunnion Fabrication: Solid carbon steel balls are precision-turned and ground using spherical grinders to achieve a surface finish of Ra ≤0.2μm—ensuring uniform contact with the hard seal. Trunnions (upper/lower) are integral to the ball, heat-treated for hardness (HRC 30–35) and machined to match the valve body’s bearing seats. For abrasive media, Stellite 6 is applied to the ball’s sealing surface via plasma transfer arc (PTA) welding, then ground to restore sphericity.

C. Seal & Actuator Integration

• Trunnion & Bearing Installation: Upper and lower trunnions are press-fitted into the valve body, with PTFE-impregnated bronze bearings to reduce friction. Bearings are lubricated with high-temperature grease (resistant to 200℃) to ensure smooth operation over thousands of cycles.
• Ball & Stem Assembly: The ground carbon steel ball is inserted into the body, and the stem is connected via a drive key—ensuring torque transfer during operation. The stem packing (graphite-PTFE) is installed in layers, with controlled compression (10–15% compression rate) to balance sealing performance and operational torque.
• Drive Mounting: Actuators (manual worm gear, pneumatic, electric) are mounted via an ISO 5211 adapter flange, with laser alignment to ensure coaxiality (stem runout ≤0.05mm)—preventing binding or premature wear. For pneumatic/electric actuators, limit switches are calibrated to trigger at fully open/closed positions, protecting seals from over-travel.

D. Quality Testing & Certification

• Hydrostatic Testing: Per API 598, the valve shell is tested at 1.5× rated pressure (e.g., 22.5MPa for Class 600) for 30 minutes—no leakage, sweating, or deformation is allowed. Seat testing is performed at 1.1× rated pressure (e.g., 16.5MPa for Class 600), with leakage measured via bubble counting (≤1 bubble per minute for Class IV).
• Pneumatic Testing: For natural gas service, the valve is tested with nitrogen at 0.6MPa to confirm airtight sealing—critical for preventing gas leaks in hazardous environments.
• Operational Testing: The valve is cycled 100 times (open/close) to verify smooth operation, consistent torque, and actuator response. Manual override (for pneumatic/electric models) is tested to ensure functionality during emergencies.
• Non-Destructive Testing (NDT): Welds (e.g., Stellite 6 seat welds) undergo liquid penetrant testing (PT) to detect surface cracks; the carbon steel body and trunnions are inspected via magnetic particle testing (MPI) to confirm structural integrity.
• Fugitive Emissions Testing: Per ISO 15848-1, the valve is tested for fugitive emissions at the stem and body-bonnet joint, meeting Class BH standards (≤100 ppmv for methane)—critical for natural gas applications.

E. Final Inspection & Documentation

• Visual Inspection: The valve is checked for surface defects (scratches, dents), proper marking (size, pressure rating, material, serial number), and compliance with ASME B16.34. Marking is permanent (laser-etched) for traceability in oil & gas pipeline systems.
• Documentation: Each valve includes an MTR for carbon steel, hydrostatic/pneumatic test reports, fugitive emissions test certificates, and compliance documents (API 6D, ISO 9001). For hazardous area applications, ATEX/IECEx certificates are provided to confirm compliance with global oil & gas safety standards.