Valves suitable for medium temperatures ranging from -40 ℃ to -196 ℃ are called low-temperature valves. Low temperature valves include low-temperature ball valves, low-temperature gate valves, low-temperature globe valves, low-temperature safety valves, low-temperature check valves, low-temperature butterfly valves, low-temperature needle valves, low-temperature throttling valves, low-temperature pressure reducing valves, etc. They are mainly used in ethylene, liquefied natural gas plants, natural gas LPG LNG storage tanks, receiving bases and satellite stations, air separation equipment, petrochemical tail gas separation equipment, liquid oxygen, liquid nitrogen, liquid argon, carbon dioxide low-temperature storage tanks and tank cars, pressure swing adsorption oxygen production and other devices. The output liquid low-temperature media such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum products, etc. are not only flammable and explosive, but also require gasification when heated, and the volume expands hundreds of times during gasification. The material of liquefied natural gas valves is very important. If the material is not qualified, it will cause external or internal leakage of the shell and sealing surface; The comprehensive mechanical properties, strength, and rigidity of the components cannot meet the requirements for use and may even fracture. Causing explosion due to leakage of liquefied natural gas medium. Therefore, in the process of developing, designing, and researching liquefied natural gas valves, material is the primary and key issue. After years of manufacturing, we have accumulated rich experience in design, process, and manufacturing, and have developed a series of low-temperature valve products.

1、 Low temperature valve product specifications and design parameters: 1. Pressure rating: 150, 300, 600Lb, 900LB, 1500LB (45MPa) 2. Valve diameter: 15-1200mm (1/2-48 ") 3. Connection form: flange type, welded type, threaded. 4. Valve materials: LCB, LC3, CF8. 5. Working temperature: -46 ℃, -101 ℃, -196 ℃, -253 ℃ 6. Applicable medium: liquefied natural gas, ethylene, propylene, etc. 7. Drive mode: manual, bevel gear transmission, electric.

2、 Low temperature valve standards and product structure: 1. Design: API6D, JB/T7749 2. Valve routine inspection and testing: According to API598 standard. 3. Valve low-temperature inspection and testing: According to JB/T7749. 4. Drive modes: manual, bevel gear transmission, and electric drive device. 5. Valve seat form: The valve seat adopts a welded structure, and the sealing surface is welded with cobalt based hard alloy to ensure the sealing performance of the valve. 6. The gate adopts an elastic structure and a pressure relief hole is designed at the inlet end. 7. The valve body of a one-way sealed valve is marked with a flow direction symbol. 8. Low temperature ball valves, gate valves, globe valves, and butterfly valves adopt a long neck structure to protect the packing. 9. Standard for ultra-low temperature ball valves: JB/T8861-2004

3、 Low temperature valve material selection: 1. Valve body and cover are made of LCB (-46 ℃), LC3 (-101 ℃), CF8 (304) (-196 ℃). 2. Gate plate: stainless steel overlay cobalt based hard alloy. 3. Valve seat: stainless steel overlay cobalt based hard alloy. 4. Valve stem: 0Cr18Ni9

4、 Low temperature valve manufacturing and testing: Qianze has established strict manufacturing processes and adopted specialized equipment for the production of low-temperature valves, and strictly controls the quality of parts processing. After special low-temperature treatment, the rough machined parts are placed in a cooling medium for several hours (2-6 hours) to release stress, ensure the low-temperature performance of the material, guarantee the precision machining size, and prevent leakage caused by deformation of the valve due to temperature changes under low-temperature conditions. The assembly of valves is also different from ordinary valves, and the parts need to be strictly cleaned to remove any oil stains to ensure their performance.

5、 Low temperature valve test equipment: 1. Low temperature valve test device 2. Liquid nitrogen storage device 3. Low temperature treatment tank 4. Low temperature test bench to ensure the performance of the valve under low temperature working conditions 5. Other

6、 Low temperature valve testing and inspection: The main components of the low-temperature valve are subjected to low-temperature treatment and each batch is sampled for low-temperature impact testing to ensure that the valve does not crack brittle under low-temperature conditions and can withstand the impact of low-temperature media. Conduct the following tests on each valve: 1. Room temperature shell strength test; 2. Sealing test at room temperature and low pressure; 3. Room temperature and low pressure sealing test; 4. Low temperature sealing and airtightness test (with upper sealing); 5. Low temperature gas seal test, etc., to ensure that the entire low-temperature valve meets the standard requirements; 6. Perform low-temperature treatment on the main components of the low-temperature valve and conduct low-temperature impact tests on each batch of samples to ensure that the valve does not crack brittle under low-temperature conditions and can withstand the impact of low-temperature media;

Other parameters of low-temperature valves: The valve body is light and small in size. In order to reduce the heat loss of the valve body, especially to ensure the use of the valve at low temperatures, a lightweight and small-sized valve body is specially designed. The long shaft valve is a valve that allows low-temperature fluid to flow through it. It adopts a long stem form, which can avoid the external heat and keep the cover at room temperature to prevent the performance of the cover seal from being reduced. This length is a suitable length obtained through calculation and experimentation. Ideal valve seat soft seal structure: In SW and BW forms, the valve body cannot be removed from the piping. In order to avoid repairing the valve body and valve seat, a soft contact valve seat is used. The valve core seal is made of Teflon or Teflon, which contains 15% glass fiber and has good low-temperature stability. It can also be replaced as needed. Hard metal sealing structure: Metal sealing is used on gate valves and valves with fire protection requirements. It is to add a tungsten chromium cobalt alloy metal liner on the contact surface of the valve seat to improve surface hardness, burn resistance, and wear resistance. The gasification pressure boosting structure gate valve adopts a flexible structure and is fully sealed. Therefore, at this time, the liquefied gas inside the valve body is sealed, and when it absorbs external heat and the temperature rises, it will undergo re gasification, causing the pressure inside the valve to increase. To prevent this phenomenon, a structure of opening pressure reducing holes on the valve core was adopted. And the long-lasting sealing packing adopts Nanchang's long-lasting PTFE ring packing at the sealing part. This filler can rely on internal pressure to have self sealing performance, so it can be easily controlled with a small tightening torque. And the friction is small, so the operation is easy. The gasket is made of Teflon material containing ceramic filling material with stable sealing properties. In addition, gaskets with spiral metal surfaces wrapped around them that have the ability to withstand frequent transitions between room temperature and low temperature, as well as maintain sealing stability against temperature changes, are also used.