Introduction of commonly used cryogenic valves

1. Low temperature gate valve
    The standard cryogenic gate valve is one-way sealed, and its elastic gate has a 3mm relief hole, which connects the valve cavity with the upstream pipeline. When the valve cavity is abnormally increased in pressure, the pressure balance can be achieved through the relief hole and the upstream pipeline. Inside the valve, the upstream medium pressure presses the elastic gate against the downstream valve seat sealing ring to achieve downstream low-pressure side sealing. The two-way sealed gate valve is to set a pressure reducing valve outside the valve cavity without having to open a hole on the gate. External pressure relief enables the gate valve to achieve upstream and downstream two-way sealing. The ultra-low temperature gate valve must mark the flow direction of the medium on the valve body.
    2. Cryogenic ball valve
    The ultra-low temperature ball valve adopts a top-mounted structure. The soft-seal ball valve is cheap and has a low leakage rate. It is only used for small-caliber and low-pressure working conditions. In contrast, hard-sealed ball valves are expensive and have a high leakage rate, but they can be used for fluids containing solid particles and have good erosion and abrasion resistance. LNG soft-seal valve seat can withstand -196℃ PCTFE (KEL-F). The soft-seal ball valve is limited to small-caliber and low-pressure working conditions. The large-caliber high-pressure ball valve should use a metal-to-metal hard seal structure. Butt-welded valves used in low temperature working conditions implement the special grade requirements specified by ANSIB16.34. The ultra-low temperature ball valve must mark the flow direction of the medium on the valve body.
    3. Cryogenic butterfly valve
    Ultra-low temperature butterfly valves require two-way sealing. Most LNG butterfly valves use butt welding end faces. Butt welding butterfly valve has high connection strength (its bearing load is at least twice that of flanged valve), more reliable connection (reduce potential flange leakage), and convenient maintenance (especially the valve seat and butterfly plate of large-diameter butterfly valve) And the valve stem can be replaced online), and the maintenance workload is small and the time is short. The ultra-low temperature butterfly valve must mark the flow direction on the valve body. Based on the influence of the low temperature medium on the sealing performance, the butterfly valve should adopt a double eccentric or triple eccentric structure to reduce or eliminate the phenomenon of excessive squeezing or scratching of the sealing surface during the opening and closing process of the butterfly valve, reducing wear and improving service life. KSB valve seat seal adopts LipSeal structure to achieve good sealing effect. The valve stem seal adopts low-emission composite packing, which can make the packing seal meet the TA-Luft standard.