Gas Flat Gate Valve | API 6D Soft Seal | DN50–DN1200

Our Gas Flat Gate Valve is a sliding isolation valve with a parallel flat gate closing member, designed for gas media including natural gas, city gas, and LPG. It provides on-off control only - not for throttling. The floating soft-seat structure with NBR rubber-coated gate eliminates sealing and leakage issues of traditional valves, while the compact full-bore design minimizes flow resistance and supports pigging. Bodies are precision-cast carbon or stainless steel with epoxy powder coating for corrosion resistance. Built to API 6D, ASME B16.34, GB/T 12234, available DN50–DN1200 with manual, pneumatic, electric, and gearbox operation.

1. Floating Soft-Seat Bidirectional Zero Sealing: The valve adopts a floating valve seat with elastic soft sealing structure; the gate plate is fully coated with high-performance NBR synthetic rubber and integrally vulcanized, generating micro-adaptive elastic deformation under operating force and medium pressure to form an excellent seal against the precision-cast seat. The four-way O-ring inverted sealing structure enables emergency seal replacement under pressure without stopping the medium, ensuring zero leakage and maximum safety for gas transmission.

2. Full-Bore Low Resistance & Pigging Capability: The straight-through full-bore flat flow channel completely removes the gate from the flow path when fully open, and the groove-free valve seat bottom prevents debris accumulation. Flow resistance is equivalent to a straight pipe, effectively reducing pressure loss and energy consumption during gas transmission. The design supports pipeline pigging, making it suitable for gas pipelines containing solid particles or dust impurities while ensuring unobstructed medium flow.

3. High Durability & Corrosion-Resistant Construction: The valve body and bonnet are integrally precision-cast from high-strength cast steel without secondary machining, ensuring high structural strength and corrosion resistance. The stainless steel valve stem features rolled trapezoidal threads for smooth operation and wear resistance, effectively reducing operating torque and extending service life. Inner and outer surfaces receive non-toxic epoxy resin powder electrostatic coating, matching the pipeline's anti-corrosion life for use in humid and corrosive environments.

4. Flexible Operation & Easy Maintenance: Available in both non-rising stem and rising stem designs to suit different installation space requirements, with handwheel, T-handle, electric, and pneumatic operation options. The integral copper nut is directly connected to the gate plate skeleton without idle travel or loosening, and the bronze material provides self-lubrication against the stem, reducing maintenance frequency. The replaceable valve seat and seal design simplify later maintenance and reduce lifecycle cost.

5. Comprehensive Safety Protection: Equipped with a triple safety stem sealing system including a dust-proof ring, multiple O-ring seals, and a sealing gasket, effectively preventing external impurity ingress and medium leakage. The inverted stem design prevents blowout under medium pressure, and double thrust bearings reduce wear for stable operation. All sizes feature integrally cast double feet and double lifting lugs for safe handling, storage, and installation.

6. Standard Compliance & Wide Material Options: Fully compliant with API 6D, ASME B16.34, GB/T 12234, JB/T 5298, and CT514 standards for design, manufacturing, and testing. Body materials include carbon steel (WCB), low-temperature carbon steel (LCB/LCC), stainless steel, and alloy steel to match different media and temperature conditions. Connection types cover flanged, butt-weld, grooved, socket, and PE joint, ensuring compatibility with global gas pipeline standards.

The Gas Flat Gate Valve operates on the parallel slide gate principle with floating soft seats. Rotating the actuator drives the stem to lift or lower the NBR rubber-coated flat gate between two floating seats: fully open, the gate retracts completely above the bore, creating an unobstructed straight-through channel with resistance equal to a straight pipe; closing, medium pressure pushes seats against the gate, and elastic rubber micro-deforms to form a tight bidirectional zero-leakage seal. Non-rising or rising stem options accommodate different installation space constraints.

Municipal Gas Supply Systems: Urban gas distribution pipelines, residential and commercial gas service lines, and community metering stations, ensuring safe, stable gas delivery to end users with reliable isolation for maintenance and emergency shutdown.

Natural Gas Transmission & Storage: Long-distance natural gas transmission pipelines, gas storage stations, compressor stations, and gas processing plants, suitable for high-pressure, large-flow gas transmission requiring full-bore pigging and bidirectional sealing.

Industrial Gas Systems: Gas pipelines in petrochemical, chemical, metallurgical, and power generation industries, providing dependable on-off isolation for various industrial process gases including hydrogen, ammonia, and synthesis gas.

LPG/LNG Systems: Liquefied petroleum gas and liquefied natural gas storage and transportation pipelines, with low-temperature carbon steel (LCB/LCC) body options adapting to cryogenic working conditions down to -29°C.

Power Plants & Gas-Fired Boilers: Gas-fired boiler fuel supply lines, power plant gas systems, and gas emergency repair projects, providing reliable isolation and control functions with low operating torque for frequent cycling.

Every Gas Flat Gate Valve undergoes rigorous quality control from raw material to shipment under ISO 9001:2015 and API 6D. All castings are MTR-verified by heat number with dimensional inspection per drawing tolerances. Each valve is hydrostatically shell-tested at 1.5× rated pressure and seat-tested at 1.1× per API 598, GB/T 13927, and ISO 5208, with low-pressure air seal testing for gas service. NDT includes magnetic particle and penetrant examination on castings and welds as required. Units ship with serialized MTR, test certificates, and 18-month warranty, with BV/SGS/TUV inspection on request.

Q1: What is the difference between a soft-seal and metal-seal flat gate valve?

A: A soft-seal flat gate valve has the gate plate fully coated with NBR, EPDM, or PTFE rubber, which micro-deforms against the seat to achieve zero leakage even at low pressures - ideal for natural gas, city gas, and water. A metal-seal (hardfaced Stellite) flat gate valve relies on precision metal-to-metal contact, offering higher temperature and pressure capability and better erosion resistance for high-velocity or particulate-laden gas, but may permit minimal leakage at very low pressures.

Q2: What is the difference between non-rising stem and rising stem designs?

A: A non-rising stem (NRS) has the stem thread inside the valve body, so the stem rotates but does not move vertically - saving installation space and protecting threads from corrosion, ideal for underground or buried gas pipelines. A rising stem (OS&Y) moves vertically as it rotates, providing a visual indication of valve position and keeping threads outside the media, preferred for above-ground industrial installations where position visibility and thread protection are important.

Q3: Can a gas flat gate valve be used for flow regulation or throttling?

A: No. Like all gate valves, the gas flat gate valve is designed for fully open or fully closed on-off service only. Operating it in a partially open position causes high-velocity gas to erode the soft rubber coating on the gate and seating surfaces, leading to premature leakage and irreversible seal damage. For gas flow regulation, use a control valve, globe valve, or butterfly valve specifically designed for throttling service.

Q4: What pressure and temperature ranges does this valve cover?

A: Pressure ratings range from PN1.0 to PN42.0 (ANSI Class 150 to Class 2500), covering low-pressure municipal distribution to high-pressure transmission. Standard operating temperature is -29°C to +150°C. Low-temperature carbon steel (LCB/LCC) bodies extend service for LPG/LNG applications, and high-temperature alloy steel options are available for elevated-temperature gas service. NBR soft seals are rated to approximately 80°C continuous; for higher temperatures, EPDM or metal-to-metal sealing is recommended.

Q5: How is the valve maintained and can seals be replaced in service?

A: Routine maintenance includes periodic stem packing lubrication and visual inspection of external surfaces. The four-way O-ring inverted sealing structure allows stem seal replacement under pressure with the valve fully open, using the back-seat function, without shutting down the pipeline. Gate and seat replacement requires pipeline depressurization and valve removal. The replaceable modular seat design simplifies overhaul, and epoxy-coated bodies require no external corrosion maintenance under normal conditions.

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