Structural features

1. Core transmission system: Efficient matching design of worm gear and worm
Structure and Materials The worm gear transmission core is continued. The worm is made of 20CrMnTi and carburized and quenched (hardness HRC58-62). The worm gear is selected from tin bronze ZCuSn10Pb1 (small diameter) or ductile iron QT500-7 (large diameter). The tooth surface is precisely ground, and the meshing accuracy reaches grade 7 of GB/T 10089. Ensure there is no jamming in the transmission. The transmission ratio is designed to match the diameter. For DN50-DN300, it is 1:30-1:50, and for DN400-DN1200, it reaches 1:60-1:80, achieving "effortless operation". By manually turning the handwheel, the butterfly plate can be driven to open and close. ​
Self-locking and protection: As the worm lead Angle is ≤5°, it has a reliable reverse self-locking function. After the butterfly plate is in place, it will not rebound under the impact of medium pressure, and no additional locking parts are required. The transmission box adopts a sealed structure of cast aluminum (small diameter) or cast iron (large diameter), with a dust cover on the top and an oil drain hole at the bottom. The interior is filled with lithium-based grease, which can prevent dust, water and medium corrosion, and is suitable for outdoor or humid working conditions. ​
2. Core structure of soft seal: Precise adaptation of rubber seal
Sealing surface design: It adopts a "butterfly plate rubber sealing ring" combination. The sealing ring is made of ethylene propylene diene monomer (EPDM) or nitrile rubber (NBR), and is fixed in the valve body sealing groove by embedded or adhesive type (for some models, it is butterfly plate covered with rubber). The sealing surface has a "U-shaped" or "Ω -shaped" cross-section. When opening and closing, the butterfly plate squeeches the sealing ring to form a line seal. When closing, the sealing specific pressure is uniform, and the leakage is ≤0.1×DN mm³/s (conforming to GB/T 13927 grade IV standard). It is suitable for non-corrosive media such as water, sewage, and air. ​
Temperature and compatibility: EPDM sealing rings are compatible with -40 ℃ to 120℃, and NBR is compatible with -20 ℃ to 80℃, meeting the requirements of conventional industrial and municipal working conditions. The sealing ring and the sealing groove of the valve body adopt an interference fit to prevent the sealing ring from shifting or falling off after long-term use. Meanwhile, the rubber material has a certain elasticity, which can compensate for slight deformation of the valve body or butterfly plate and ensure the stability of the seal. ​
3. Valve body and butterfly plate structure: Optimized design adapted to soft sealing
Valve body structure: Cast from cast iron HT200, ductile iron QT450-10 or carbon steel WCB. The flow channel is a straight-through streamlined type, with a smooth inner wall (roughness Ra≤1.6μm), reducing medium resistance. Flange connection complies with GB/T 9119 or ANSI B16.5 standards. The sealing surface is a raised face (RF), and the number of bolt holes matches the diameter of the hole to ensure precise connection with the pipe flange, and is compatible with PN10/PN16 pressure grades. ​
Butterfly plate design: It adopts a vertical plate structure (represented by "1" in the model), with materials of ductile iron QT450-10 (surface plastic spraying for anti-corrosion) or stainless steel 304 (for corrosion-resistant working conditions). The thickness has been optimized through mechanical calculation to ensure no warping during opening and closing. The edge of the butterfly plate is treated with an arc transition to prevent the rubber sealing ring from being scratched during opening and closing, thereby extending the service life of the sealing parts. The valve stem and the butterfly plate are fixed by key connection and set screw, with a fit clearance of no more than 0.05mm, ensuring the synchronization of transmission. ​
4. Operation and auxiliary structures: Enhanced convenience and safety
Handwheel and opening indication: The worm input end is equipped with a detachable handwheel, made of engineering plastic (for small diameters) or cast steel (for large diameters), with an anti-slip texture on the surface. A 0°-90° opening scale is set beside the handwheel, which is mechanically synchronized with the actual opening of the butterfly plate. The operator can visually determine the valve status (fully open at 90°, fully closed at 0°). ​
Valve stem and bearing: The valve stem is made of 2Cr13 stainless steel and is chrome-plated on the surface (hardness HV≥600), which is corrosion-resistant and wear-resistant. Double-row deep groove ball bearings are equipped on both sides of the worm gear to reduce the radial movement of the valve stem, ensure the coaxiality of the butterfly plate when opening and closing with the sealing surface, and avoid sealing offset. The bearing is designed for lifetime lubrication and requires no frequent maintenance. ​
Emergency and overload protection: For some large-diameter models (DN800 and above), friction plate type torque limiters are installed inside the transmission box. When the operating torque exceeds 1.2 to 1.5 times the rated value, it will slip to prevent damage to the worm gear, worm or valve stem. The end of the worm is reserved with an electric drive interface (such as a keyway), which can be equipped with an electric head as needed to upgrade to a "manual and electric" dual drive, without the need to replace the entire transmission system. ​
5. Diameter adaptation differences: Structural details optimized as needed
Small diameter (DN50-DN300) : The overall structure is compact. The worm gear housing and the valve body are integrated as one. The handwheel is directly installed on the worm shaft, occupying a small space. It is suitable for equipment rooms with dense pipelines or narrow installation environments. Most sealing rings are of the adhesive type and are easy to replace. ​
Large diameters (DN400-DN1200) : A split worm gear housing is adopted, which is rigidly connected to the valve body through a bracket to enhance transmission stability. The worm is thickened (diameter ≥30mm), and the worm gear module is increased to enhance the load-bearing capacity. The sealing ring is embedded and, in combination with the butterfly plate guiding structure, ensures precise connection of the sealing surface and avoids sealing deviation caused by large diameter. ​