III. Product Features

• Wedge Gate Sealing Excellence: The wedge-type gate design ensures uniform contact with the valve seat under line pressure, creating a tight seal that improves with increasing pressure—critical for preventing leakage in oil and gas pipelines. The wedge can be solid or flexible (split wedge), with flexible designs accommodating minor pipeline misalignment or thermal expansion.
• Dual Flange Versatility: Single and double flange options provide installation flexibility. Single flange valves are ideal for systems where one end connects to a fixed pipeline and the other to a removable component (e.g., pumps), while double flange designs offer secure mounting between two fixed flanges, reducing stress on pipeline joints in high-vibration environments.
• Rising Stem Visibility: The rising stem design (standard) provides visual confirmation of valve position—fully open when the stem is extended, fully closed when retracted—eliminating ambiguity in manual operation and simplifying system troubleshooting. Non-rising stems are available for space-constrained applications, with position indicators for status tracking.
• Robust Stem Protection: The stem is protected by a gland packing system, typically featuring flexible graphite or PTFE packing rings, preventing external leakage and ensuring smooth operation. The packing is designed to be adjustable, allowing for maintenance without disassembling the valve body.
• Bidirectional Sealing: The valve body and gate are engineered for bidirectional sealing, enabling installation without regard to media flow direction. This simplifies on-site installation, reduces errors, and enhances versatility in reversible pipeline systems (e.g., water distribution networks with variable flow).
• High-Temperature Tolerance: WCB cast steel retains its mechanical properties at temperatures up to 425℃, making the valve suitable for medium-pressure steam lines in power plants or hot oil circuits in refineries, where thermal stability is critical.
• Erosion Resistance: Hard alloy overlay on gate and seat surfaces (e.g., Stellite 6) resists wear from abrasive media or high-velocity flow, extending service life in applications such as sewage systems or crude oil pipelines with minor sediment.

IV. Manufacturing Process

• Material Selection and Inspection: WCB cast steel raw materials undergo rigorous testing to verify compliance with ASTM A216 standards. Chemical composition analysis ensures carbon content (0.25-0.35%), manganese (0.60-1.00%), and silicon (0.15-0.40%) meet specifications, while mechanical testing confirms tensile strength (≥415MPa) and impact resistance (≥20J at -29℃). Valve stem materials (2Cr13) are checked for corrosion resistance and hardness (HB 197-255).
• Precision Casting: Valve bodies and bonnets are produced using sand casting with resin-bonded sand molds, ensuring dimensional accuracy and minimizing internal defects (e.g., porosity, shrinkage). Castings undergo ultrasonic testing to detect hidden flaws, critical for pressure-containing components.
• Machining of Key Components: Flange faces, stem holes, and seat surfaces are machined using CNC lathes and milling centers to maintain tight tolerances (±0.05mm). Flange sealing surfaces are finished to Ra 1.6μm to ensure proper gasket seating, while stem threads are precision-cut to ensure smooth engagement with the handwheel or actuator.
• Sealing Surface Treatment: Gate and seat sealing surfaces are prepared via overlay welding of hard alloy (Stellite 6) using submerged arc welding. This process is followed by heat treatment (solution annealing) to enhance hardness (HRC 38-45) and prevent cracking, ensuring wear resistance during repeated operation.
• Assembly and Calibration: The valve stem is assembled with the gate, ensuring perpendicular alignment to prevent binding during movement. Packing glands are torqued to specifications to balance sealing and stem mobility. Manual handwheels are calibrated for smooth rotation, with torque requirements tested to ensure operability across the valve’s service life.
• Pressure Testing and Quality Control: Each valve undergoes comprehensive testing in accordance with API 598:
  • Shell test: 1.5 times PN16 (2.4MPa) to verify the valve body and bonnet’s structural integrity, with no visible leakage or deformation.
  • Seat test: 1.1 times PN16 (1.76MPa) to confirm tight shutoff, with zero leakage across the gate-seat interface.
  • Operation test: Verification of smooth gate movement (full open to full close) and proper alignment of stem position indicators.