Structural features

1. Core transmission system: Exclusive design of worm gear and worm mechanism
Structural composition It is composed of a high-precision worm gear (input end, connected to the handwheel or drive shaft) and a worm gear (output end, rigidly connected to the valve stem). Both are made of high-strength alloy materials (the worm gear is mostly 20CrMnTi and carburized and quenched, and the worm gear is tin bronze ZCuSn10Pb1 or ductile iron QT500-7), and the tooth surface is precisely ground. The meshing accuracy meets the GB/T 10089 grade 7 standard, ensuring smooth transmission without jamming. ​
Deceleration and force-increasing characteristics The worm gear transmission ratio is typically 1:30 to 1:80 (adjusted according to the valve diameter; for large diameters such as DN2500, it can reach over 1:100). By decelerating, it achieves "small torque input and large torque output", which can amplify the manual operation force by tens of times, easily driving the opening and closing of large-diameter butterfly plates and solving the problem of laborious manual operation of large-diameter valves. ​
Self-locking function: As the lead Angle of the worm is less than the friction Angle of the meshing surface, it has a reverse self-locking ability. That is, after the butterfly plate is in place, even if it is impacted by the medium pressure, the worm gear will not drive the worm in reverse. No additional locking device is needed to maintain the stability of the valve opening. It is especially suitable for working conditions that do not require frequent adjustment (such as cut-off and shut-off scenarios). ​
2. Compatible structure with the valve body: precise connection and stable support
Valve stem connection: The center hole of the worm gear and the valve stem are connected by a key or spline (for some large-diameter models, a conical surface is used with a set screw for fixation), with a fit clearance of ≤0.05mm, ensuring that the transmission torque is transmitted without loss and avoiding the opening deviation caused by the relative sliding between the valve stem and the worm gear. ​
Bearing support: Double-row deep groove ball bearings or tapered roller bearings are equipped on both sides of the worm gear. The outer ring is fixed in the transmission housing, and the inner ring fits with the journal of the worm gear to reduce radial and axial movement during the rotation of the worm gear. The bearing adopts a lifetime lubrication design (filled with lithium-based grease), requiring no frequent maintenance and is suitable for long-term outdoor or harsh environment use. ​
Transmission housing: Made of cast aluminum or cast iron (cast aluminum for small valves and cast iron for large valves), the housing is of a sealed structure, with a dust cover on the top and an oil drain hole reserved at the bottom, which can prevent dust and rainwater from entering the meshing surface. At the same time, it is convenient to change the lubricating oil regularly and extend the service life of the transmission system. ​
3. Operation and control structure: Optimization of convenience and safety
Handwheel design: The input end of the worm gear is connected to a detachable handwheel (made of engineering plastic or cast steel), with anti-slip patterns on the surface of the handwheel. Some models are equipped with an opening degree indication scale (0°~90°), which is synchronized with the actual opening degree of the butterfly plate, facilitating the operator to visually judge the valve status. The handwheels of large-diameter valves can also be equipped with power-assisted handles to further reduce the operational intensity. ​
Emergency adaptation interface: Some models reserve an electric drive interface (such as flange or keyway) at the end of the worm, allowing for the installation of small electric actuators (such as electric heads) as needed to achieve a "manual and electric" dual drive mode, meeting the upgrade requirements from manual control to semi-automatic control without the need to replace the entire transmission system. ​
Overload protection: For large-diameter models (such as DN1600 and above), the transmission box is equipped with a torque limiter (such as friction plate type or pin type). When the operating torque exceeds the set value (such as 1.2 to 1.5 times the rated torque), the limiter will slip or cut the pin to prevent the worm gear and worm from being damaged due to overload and protect the main structure of the valve. ​
4. Flange connection and sealing compatibility: Continuing the basic advantages of flanged butterfly valves
Flange standard In accordance with the national standard GB/T 9119 or the American standard ANSI B16.5, the flange sealing surface is selected as raised face (RF), concave and convex face (MFM) or tenon and groove face (TG) according to the pressure grade. The distribution and number of bolt holes match the corresponding diameter standard to ensure precise connection with the pipe flange and adapt to different pressure working conditions (PN10~PN40). ​
Sealing coordination: The stable transmission of the transmission system can prevent damage to the sealing surface caused by uneven force when the butterfly plate is opened and closed. Combined with the soft seal (EPDM/FKM) or hard seal (hard alloy/ceramic coating) structure of the butterfly valve itself, the smoothness of the worm gear transmission can further enhance the sealing reliability and reduce the risk of sealing leakage caused by operational shock. ​
5. Adapt to structural differences of different diameters: Optimize design as needed
Small diameter (DN50 - DN300) : The worm gear and worm mechanism is compact in size, integrated at the top of the valve, with a compact overall structure. The handwheel is directly installed on the worm shaft, making operation easy and convenient. It is suitable for scenarios with limited space (such as equipment rooms with dense pipelines). ​
For large diameters (DN1200 - DN2500) : A split transmission box is adopted. The worm gear and worm mechanism is independently installed on the bracket above the valve. The bracket is rigidly connected to the valve body through bolts, enhancing the overall stability. At the same time, the diameter of the worm gear is thickened and the module of the worm wheel is increased to enhance the load-bearing capacity of the transmission system and meet the load requirements of the super-large butterfly plate. ​