液化气体如氧、氮、氩、天然气、氢或氦（-218^oC）的生产、运输和储存，存在着几个技术难题。Velan独家采用的加长阀帽铸造阀门更安全更有效。
　　The production, transport and storage of liquefied gases such as oxygen, nitrogen, argon, natural gas, hydrogen or helium (down to - 425°F), presents several technical problems. Velan specially-adapted extended bonnet cast valves offer safe and efficient service.

材料：
MATERIALS:

• 阀体和阀帽：阀体和阀帽采用奥氏体不锈钢铸件，具有更好的撞击强度，最小的热损耗，更加耐腐蚀。
  Body and bonnet: Austenitic stainless steel castings used for bodies and bonnets offer excellent impact strength, minimal heat loss and protection against corrosion.
• 阀杆：奥氏体不锈钢。为了抗磨损，阀杆也采用A479等级XM-19材料，抗拉强度更好，即使在超低温环境，在阀杆接触点处，仍然具有优异的低摩擦和无磨损运动的性能。
  Stem: Austenitic stainless steel. To reduce galling, stems are also offered in A479 grade XM-19 with high tensile strength even at extreme low temperatures, excellent low friction and galling-free movement at points of stem contact.
• 接触液体的部件：奥氏体不锈钢和钨铬钴合金6。
  Wetted parts: All Austenitic stainless steel and Stellite 6.
• 阀杆螺母/轭架衬套：奥氏体球墨铸铁Gr. D-2C。
  Stem nut/yoke bushing: Austenitic ductile iron Gr. D-2C.
• 填料：通过绝缘气体柱防止PTFE或石墨填料冻结凝固。
  Packing: PTFE or graphite packing protected from freezing by a column of insulating gas.
• 阀座面：采用钨铬钴合金6，避免磨损和擦伤。
  如果需要紧密关闭，截止阀和止回阀都会配置四氟乙烯、PTFE或其它软镶嵌件。
  Seating faces: Stellite 6 is used to prevent seizing and galling.
  When extremely tight shutoff is required, globe and check valves are supplied with Neoflon, PTFE or other soft inserts.
• 螺栓：应力硬化奥氏体不锈钢。
  Bolting: Strain-hardened Austenitic stainless steel.
• 阀杆螺母的润滑：Exxon Nebule No. 930-AA或Shell Darina EPI或相同的产品。
  Lubrication of stem nut: Exxon Nebula Lubriplate No. 930-AA or Shell Darina EPI or equivalent.

结构特征：
DESIGN FEATURES:

• 具有足够的气体柱长度的加长阀帽，通常由用户指定，配置在所有阀门上，使得阀杆填料与低温液体之间保持足够的距离，从而能够保持自身的性能。
  Extended bonnets with sufficient gas column length, usually specified by customer, are supplied for all valves to keep stem packing at sufficient distance away from the cold fluid to remain functional.
• 适用于低温环境的钨铬钴合金阀座面的柔性楔板。
  Flexible wedges with Stellite seating faces for cryogenic service.
• 备有可用于截止阀，活塞和旋启式止回阀阀瓣的四氟乙烯镶嵌件。
  Neoflon inserts are available for globe, piston, and swing check discs.
• 清洁处理：所有低温阀门都全面进行脱脂和清洗，管路端口都经过密封，以防止污染。
  Cleaning: All cryogenic valves are thoroughly degreased and cleaned and pipe ends are sealed to prevent contamination.