III. Product Features

• Telescopic Structure Flexibility: The telescopic inner cylinder slides within the outer body, accommodating axial displacement (±10mm) and minor angular misalignment (≤3°) caused by thermal expansion, pipeline settlement, or installation tolerances. This eliminates stress on valve flanges and pipeline joints, reducing leakage risks and extending system life—critical for outdoor or underground pipelines exposed to temperature swings.
• Dual Sealing Reliability: The PTFE soft seal delivers bubble-tight shutoff for clean media, minimizing leakage to near-zero levels (ideal for water supply or steam systems where efficiency is key). Under high pressure or when handling fluids with minor particulates, the metal backup seal engages to maintain shutoff, preventing premature failure from soft seal wear.
• Ductile Iron Durability: QT450 ductile iron resists cracking under impact (e.g., installation shocks, pipeline vibration) and corrosion in wet environments (via optional epoxy coating). Its toughness outperforms gray iron, ensuring the valve withstands harsh conditions in municipal or industrial settings.
• Low Flow Resistance: The full-port design (gate fully retracts to open the entire DN50 diameter) minimizes pressure drop, ensuring efficient fluid transmission. This reduces energy consumption for pumps, a key advantage in circulation systems like HVAC loops.
• Easy Installation and Alignment: Flanged connections simplify integration into existing pipelines, while the telescopic structure compensates for minor misalignment—reducing on-site fitting time and errors. The handwheel’s ergonomic design (knurled grip) ensures comfortable manual operation, even with frequent use.
• Maintenance-Friendly Design: The stem packing (flexible graphite) is adjustable without disassembling the valve, allowing for quick replacement to prevent external leakage. The split-body structure enables access to internal components (gate, seals) for repair—reducing downtime compared to one-piece valves.

IV. Manufacturing Process

• Material Selection and Inspection: Ductile iron (QT450-10) undergoes rigorous testing, including chemical composition analysis (verifying carbon, silicon, and magnesium content) and mechanical property tests (tensile strength, elongation, impact resistance). Only materials meeting QT450-10 standards proceed to production. PTFE for soft seals is tested for purity (no fillers) and thermal stability (up to 120℃).
• Telescopic Structure Machining: The outer body and inner cylinder are precision-cast, then machined using CNC lathes to ensure smooth sliding surfaces (Ra ≤1.6μm). Tolerances are held to ±0.05mm to prevent jamming while maintaining a tight fit—critical for the telescopic function.
• Seal Fabrication and Integration: PTFE soft seals are molded to exact dimensions, bonded to the gate via high-temperature adhesive, and cured to ensure adhesion. Metal seal surfaces (gate and seat) are ground to a mirror finish (Ra ≤0.8μm) to enhance contact with the soft seal and ensure backup sealing effectiveness.
• Stem and Handwheel Assembly: The stem (2Cr13 stainless steel for corrosion resistance) is threaded with a trapezoidal profile to ensure smooth, self-locking operation. The handwheel is cast from ductile iron, machined for balance, and fitted to the stem with a keyway to prevent slippage.
• Telescopic Calibration: The inner cylinder is tested for axial movement (±10mm) under pressure to ensure it slides freely without binding. The gate is aligned with the seat to verify uniform sealing contact across the PTFE and metal surfaces.
• Pressure and Leak Testing: Each valve undergoes:
  • Shell test: 1.5×nominal pressure (e.g., 3.75MPa for PN25) to verify the body’s structural integrity, with no visible leakage.
  • Seat test: 1.1×nominal pressure (using water or air) to confirm soft seal tightness (zero bubbles) and metal seal backup (minimal leakage under extreme conditions).
  • Operation test: Verification of smooth gate movement (full open/close) and proper telescopic function under pressure.