New Ultra-Low Temperature Zero Friction Seal Compensation Butterfly Valves

In the past two decades, China’s real economy has entered a rapid development phase under the guidance of the "sustainable development" strategy. From the planning and construction of the national space station to the development of "new infrastructure" in the 5G era and the implementation of livelihood projects and poverty alleviation, these efforts are advancing in parallel, reflecting unprecedented enthusiasm. However, the development of the industrial economy is inseparable from the support of infrastructure and equipment. As the primary control components in process pipelines, valves often play a vital role in critical operations. Especially in the emergency shut-off of special media such as flammable, explosive, and toxic substances, no errors are permissible. However, China has long been restricted by foreign technology in these critical bottleneck areas and has had to rely on imported products. The long delivery periods often hinder the progress of critical stages in project construction.
 
This article focuses on the structural design and introduces a new type of ultra-low-temperature zero-friction seal compensation butterfly valve. Compared with other butterfly valves of the same diameter and pressure, this new valve design requires only about a quarter of the torque to open under pressure, and the operation speed is also greatly improved. Under working conditions where the medium needs to be cut off urgently, the advantages are quite evident. It is hoped that the introduction of this new valve will address the difficulties of some customers and contribute to the development of the industrial economy.

As shown in Figure 3, the structure and physical depiction of the zero-friction seal compensation butterfly valve consist mainly of a valve body, valve seat, valve stem, pin, slide, butterfly plate, and fasteners. The slide is generally positioned at an angle of 30° to the centerline of the valve stem, which can be fine-tuned according to the valve diameter and opening time. The larger the angle, the faster the valve seat and butterfly plate will separate, increasing the rigidity requirements for each part.
 
 
Figure 3 Structure and picture of zero-friction seal compensation butterfly valves
 
This new zero-friction butterfly valve also uses the operation principle of the three-eccentric hard seal butterfly valve, but the connection between the valve stem and the butterfly plate has been improved at the moment of opening and closing. To open the butterfly valve, first turn the handwheel on the top of the valve. At this point, the principle of globe valve thread and nut transmission is applied. The valve stem is lifted upward by the thread transmission, driving the slider to move upward simultaneously. At this point, the pin will move relative to the slide groove in the slider, sliding downward (although the slider is lifted and the slide groove moves upward). The pin is connected to the butterfly plate, and the slide groove has a specific angle, forcing the butterfly plate to be pulled toward the valve stem, thereby easily separating the sealing surface of the butterfly plate from the sealing surface of the valve seat. Once the sealing surfaces of the butterfly plate and valve seat are separated, the medium in the pipeline can easily release pressure through the gap between them. At this point, the valve is not fully open, but the pressure difference across the valve is very small and nearly negligible. You need only turn the rotary wrench under the handwheel to rotate the butterfly plate to a position parallel to the flow channel, easily achieving full valve opening. Conversely, when the valve needs to be closed, first rotate the wrench under the handwheel by 90°. At this point, since the valve is not fully closed and a gap exists between the sealing surfaces of the butterfly plate and valve seat, no friction occurs between them. The only friction during the entire process is between the valve stem and the packing, and between the lower valve stem and the bearing, both of which are relatively minor and easily manageable. Next, turn the handwheel at the top. Again using the principle of thread transmission, the valve stem will naturally move downward, driving the slider downward, while the pin moves relative to the slide groove. Due to the angle of the slide groove, it will naturally drive the butterfly plate toward the valve seat sealing surface until it fits tightly, thereby achieving sealing and allowing the valve to be fully closed. Throughout the entire opening and closing process, the sealing surfaces of the butterfly plate and valve seat remain separated in a static, wear-free state, ensuring no friction occurs between them, which effectively protects the sealing surfaces.
 
Throughout the entire process, although the transmission principle of the globe valve is applied, the required operating force is much smaller than that of the globe valve operation. This is because the globe valve is operated by pressing the valve disc through turning the handwheel, often requiring an F wrench with an extended rod to accomplish the task. However, in the sealing process of the butterfly valve, when the valve stem is driven downward, the butterfly plate moves in the same direction as the medium flow, eliminating the need to overcome the reverse thrust of the medium. As a result, this butterfly valve structure requires lower torque compared to a traditional transmission-type butterfly valve. In an actual torque comparison test, under the same diameter and pressure, the operating torque of this hard-sealed butterfly valve structure is only about one-fourth that of a traditional butterfly valve. Due to this advantage, while many traditional butterfly valves require worm gears to open, the new zero-friction butterfly valve only requires a handle and handwheel for easy operation. Especially in scenarios requiring intelligent operation, the new butterfly valve's lighter torque means the required actuator will be significantly smaller, leading to much lower overall machine costs, making the advantage quite apparent.
 
In the field of ultra-low temperatures, most valves can easily achieve sealing at room temperature, but maintaining sealing performance under low-temperature conditions is challenging. The primary reason is that extremely low temperatures cause changes in the metallographic structure of the metal parts, resulting in slight deformation of the seals, particularly when the sealing surface of key components like butterfly valves is irregular. This deformation is especially pronounced. Conventional hard-sealed butterfly valves rarely have sealing compensation capabilities, so once leakage occurs, standard measures cannot resolve the issue. The advantage of the new zero-friction seal compensation butterfly valve is its ability to compensate for sealing at low temperatures. When the pin slides in the groove, the slide generally has a certain margin. When the sealing surface shrinks at low temperatures and causes leakage, the handwheel can be tightened slightly more, allowing the pin to drive the butterfly plate to fit the valve seat sealing surface more closely. This process is similar to static compression, converting the rotational motion into radial micro-motion of the butterfly plate to achieve sealing. In actual operation, as long as the sealing surface finish is adequate, this design requires less compensation force than a metal seated globe valve, yet still achieves an effective seal. Furthermore, from a long-term perspective, even if the sealing surface experiences slight normal corrosion, as long as the surface matching the valve seat remains undamaged, the seal can be compensated by moving the slider, something conventional metal seated butterfly valves cannot achieve. In addition to these advantages, this new butterfly valve can be quickly opened by rotating the wrench 90° after the initial handwheel operation. Compared to similar metal seated butterfly valves, the time required for opening and closing is significantly shorter, which is particularly advantageous in locations requiring emergency medium cut-off.