With the rapid development of industrial technology, more stringent requirements have been placed on the valve industry, especially for butterfly valves used in cryogenic media. Besides meeting the performance requirements of general valves, the most important aspects are the reliability of valve sealing, the flexibility of operation, and other special requirements for cryogenic valves under cryogenic conditions. It is well known that butterfly valves have a series of advantages, including compact structure, small size, light weight (40%–50% lighter than gate valves of the same pressure and diameter), low fluid resistance, and rapid opening and closing. However, in some cryogenic plants in my country, such as natural gas liquefaction equipment, air separation equipment, and pressure swing adsorption equipment in the chemical industry, more than 80% of the valves used are gate valves or globe valves, with very few butterfly valves used. The main reasons for this are the poor sealing performance of metal-sealed butterfly valves under cryogenic conditions, and other factors such as unreasonable structure causing internal and external leakage of the medium, seriously affecting the safety and normal operation of these cryogenic equipment and failing to meet their requirements. With the continuous development of cryogenic equipment in China, the requirements for cryogenic valves are increasing. To adapt to the needs of market economic development, our company has made structural improvements to metal-sealed butterfly valves and developed a triple-eccentric pure metal butterfly valve with high sealing performance (Figure 1, currently pending national patent application). It can meet the requirements regardless of whether the medium is high or low temperature. Based on its structural characteristics, only a brief introduction to its cryogenic performance is given below. I. Requirements for the sealing performance of cryogenic butterfly valves: There are two main causes of leakage in cryogenic valves: internal leakage and external leakage. 1) Internal leakage is mainly caused by deformation of the sealing surface at low temperatures. When the medium temperature drops to a point where the material undergoes a phase change, a volume change occurs, causing the originally highly precision-ground sealing surface to warp and deform, resulting in poor low-temperature sealing. We conducted a cryogenic test on a DN250 valve with liquid nitrogen (-196℃) as the medium and 1Cr18Ni9Ti (without cryogenic treatment) as the butterfly plate material. We found that the warping deformation of the sealing surface reached about 0.12mm, which is the main cause of internal leakage. Our newly developed butterfly valve has changed from a planar seal to a conical seal. The valve seat is an oblique conical elliptical sealing surface, which forms a sealing pair with a circular elastic sealing ring embedded in the butterfly plate. The sealing ring can float radially within the butterfly plate groove. When the valve is closed, the elastic sealing ring first contacts the short axis of the elliptical sealing surface. As the valve stem rotates, it gradually pushes the sealing ring inward, forcing the elastic ring to contact the long axis of the oblique conical surface, eventually resulting in the elastic sealing ring fully contacting the elliptical sealing surface. Its sealing relies on the deformation of the elastic ring. Therefore, when the valve body or butterfly plate deforms at low temperatures, the elastic sealing ring absorbs and compensates for the deformation, preventing leakage and jamming. This elastic deformation disappears immediately when the valve is opened, resulting in minimal relative friction during opening and closing, thus extending its service life. 2) External leakage of the valve: Firstly, when the valve and pipeline are connected by flanges, leakage occurs due to the asynchronous contraction of the connecting gaskets, bolts, and fittings at low temperatures. Therefore, we changed the connection between the valve body and pipeline from flanges to a welded structure to avoid low-temperature leakage. Secondly, there is leakage at the valve stem and packing. Most valves use F4 packing because of its good self-lubricating properties, low coefficient of friction (f=0.05～0.1 for steel), and unique chemical stability, making it widely used. However, F4 also has drawbacks: firstly, it has a high tendency for cold flow; secondly, it has a large coefficient of linear expansion, which causes contraction at low temperatures, leading to leakage and extensive icing at the valve stem, causing the valve to malfunction. Therefore, the cryogenic butterfly valve developed by our company adopts a self-shrinking sealing structure (Figure 2), which utilizes the large expansion coefficient of F4 to achieve sealing at both normal and low temperatures through a reserved gap. [b]II. Design Requirements for Valve Body and Stem Bushing:[/b] 1) Shape of Cryogenic Valve Shell Structure. The correct selection of materials is of paramount importance to the normal and reliable operation of the valve. Compared with gate valves and globe valves, the butterfly valve not only avoids deformation caused by cold shrinkage and thermal stress at low temperatures due to irregular shape and uneven shell wall thickness, but also has a small volume and a basically symmetrical shape, resulting in a small heat capacity and low pre-cooling consumption. Its regular shape also facilitates cold insulation measures for the valve. For example, our newly developed DD363H butterfly valve is designed and manufactured entirely according to the special characteristics of cryogenic valves to ensure reliable use at low temperatures. For example, the shell material is selected as 1Cr18Ni9Ti austenitic stainless steel with a cubic lattice. 2) Selection of Valve Stem Bushings: According to user feedback, some cryogenic valves experience sticking and seizing issues in their rotating parts during operation. This is mainly due to improper selection of mating materials, insufficient cold clearance, and inadequate machining precision. Our company has implemented a series of measures to prevent these issues during the development of cryogenic valves. For example, we have selected SF-1 type composite bearings with low friction coefficients and self-lubricating properties for the upper and lower valve stem bushings, making them suitable for the specific needs of cryogenic valves. Metal-sealed butterfly valves possess characteristics not found in ordinary valves, particularly low flow resistance, reliable sealing, rapid opening and closing, and long service life. Our company's triple-eccentric metal-sealed butterfly valve achieves sealing force through the deformation of the elastic ring, thus eliminating the need for medium force and enabling bidirectional sealing. Based on these characteristics, butterfly valves will gain wider attention, and more butterfly valves will be used in cryogenic equipment in the future.