DN50 Ductile Iron Metal-Seated Flanged Connection Telescopic Soft Seal Mechanical Gate Valve

I. Product Overview

II. Key Attributes and Specification Parameters

Basic Attributes

• Structure Design: Telescopic gate valve with a split-body structure, featuring a movable inner cylinder that slides within the outer body to absorb pipeline displacement (axial or angular). This design eliminates stress from thermal expansion, contraction, or ground settlement, preventing valve or pipeline damage—a key advantage over rigid gate valves.
• Body Material: Ductile iron (grade QT450-10), a malleable alloy with superior mechanical properties: tensile strength ≥450MPa, elongation ≥10%, and impact resistance (≥15J at -20℃). QT450 offers better corrosion resistance than gray iron, making it suitable for wet or humid environments, while balancing cost and durability.
• Sealing System: Dual-mode sealing combining soft and metal components:
  • Primary seal: PTFE (polytetrafluoroethylene) soft seal ring bonded to the gate, ensuring bubble-tight shutoff for clean media (water, steam) with low friction and chemical resistance.
  • Secondary seal: Metal-to-metal backup seal (ductile iron or alloy steel) on gate and seat surfaces, activating under high pressure or abrasive conditions to prevent leakage if the soft seal wears—enhancing reliability in harsh scenarios.
• Pressure Rating: PN10 to PN25 (1.0MPa to 2.5MPa), suitable for medium-pressure systems such as municipal water mains, industrial steam lines (saturated steam), and HVAC circuits.
• Temperature Range: -10℃ to 120℃, operating stably in cold water (e.g., groundwater) and moderately heated fluids (e.g., low-pressure steam, hot water loops).
• Nominal Diameter: DN50 (2”), catering to small-to-medium flow rates in residential, commercial, and light industrial pipelines.
• Connection Type: Flanged ends conforming to PN10/PN16 standards (GB/T 17241.6, EN 1092-1). Flanges feature precision-drilled bolt holes for alignment with pipeline flanges, ensuring leak-free installation with gaskets (typically EPDM or PTFE).
• Operation Mode: Mechanical manual operation via a handwheel with a trapezoidal-thread stem. The handwheel rotates to raise or lower the gate, with a self-locking design to hold position—preventing unintended movement from vibration or pressure fluctuations.
• Media Compatibility: Versatile for clean water, raw water, saturated steam (≤120℃), hot water, compressed air, mineral oil, and mildly corrosive fluids (pH 6–8), ensuring adaptability across sectors.
• Design Standards: Complies with GB/T 12232 (cast iron gate valves) and EN 13709, ensuring compatibility with domestic and international pipeline systems.

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.

V. Product Advantages

• Pipeline Stress Relief: The telescopic design absorbs thermal expansion and misalignment, preventing flange leakage or valve damage—critical for systems with temperature fluctuations (e.g., steam lines, outdoor water mains).
• Dual Seal Versatility: Soft PTFE seals ensure tight shutoff for clean media, while metal backup seals handle high pressure or minor abrasives—eliminating the need for separate valves for different conditions.
• Cost-Effective Durability: Ductile iron balances strength and cost, outperforming gray iron in impact resistance and stainless steel in affordability. The valve’s design minimizes maintenance, reducing lifecycle costs.
• Energy Efficiency: Full-port design reduces pressure drop, lowering pump energy consumption in circulation systems like HVAC or water distribution networks.
• Easy Integration: Flanged connections align with industry standards, simplifying retrofitting into existing pipelines. The telescopic feature reduces installation precision requirements, saving on-site time.
• Reliable Manual Operation: The self-locking handwheel ensures precise control, with no need for power—ideal for remote or backup systems where automation is impractical.

VI. Product Applications

• Municipal Water Supply: Deployed in residential or commercial water mains, where the telescopic design handles ground settlement and temperature changes, and soft seals prevent water loss.
• HVAC and Building Services: Used in hot/cold water loops for heating or cooling systems, leveraging low pressure drop and telescopic compensation for pipe expansion from temperature swings.
• Industrial Steam Systems: Suitable for low-pressure saturated steam lines (≤120℃) in food processing or textile mills, where the metal backup seal ensures reliability under steam pressure.
• Light Industrial Fluids: Applied in mineral oil transfer lines or compressed air systems, with PTFE seals resisting oil degradation and metal seals handling pressure spikes.
• Agricultural Irrigation: Used in underground water distribution, where the valve’s corrosion resistance and telescopic function withstand soil movement and outdoor conditions.