Velan能够制造世界上最先进的锻造平行滑动阀门。我们独特的盒式结构将所有滑动阀瓣的运动部件全部包括在内。平行滑动阀门的结构设计主要根据作用在阀座整体的下游阀瓣上的初始系统压力。在阀座上，没有楔板作用力或其它负载力。因此，关闭扭矩明显较低，手动操作比较轻松，对动力执行机构的扭矩需求也就比较小。这种结构的基本特性，决定平行滑动阀门比较不会受到热附着的影响，因此在高温应用领域具有显著的安全优势。在工作条件接近482^oC，热附着可能要求使用楔板闸阀。在这些情况下，在关闭阀门的初始作用力上，还增加了压缩负载（由于热膨胀）。这种附加的负载可能导致阀门粘合，甚至无法开启。
　　Velan manufactures one of the world's most advanced forged parallel slide valves. Our unique cage unit comprises all of the operating parts of the slide discs. The parallel slide valve design relies on the primary system pressure acting on the downsteam disc for seat integrity. There is no wedging action or extra loading on the seats. As a result, closing torques are considerably lower, requiring less manual operating effort or smaller power actuators. Due to its inherent design, the parallel slide valve is not subject to thermal binding concerns, resulting in a distinct safety advantage in high temperature service. Thermal binding may result in some applications utilizing wedge type gate valves when operating conditions begin to approach 900^oF. In these instances, a compression load (due to thermal expansion) in addition to that initially applied for closure results. This additional load may cause the valve to bind, even to the point of restricting opening.

　　平行滑动阀门固有的缺点是阀座在全过程运动中的负载导致的阀座磨损。在Velan采用了宽大的钨铬钴合金6硬化阀座面，中心因科镍弹簧（用于将负载分散到阀座两面，消除阀座磨损），以及能够消除振动的精确导轨系统等技术后，这种缺点做造成的影响降到最小。如果阀门用在压差很大的场合，建议采用旁通阀来使得阀门在开启前平衡阀瓣两端的压力。
　　The inherent disadvantage to parallel slide valves is seat wear due to seat loading throughout the entire travel. This effect has been minimized in the Velan design by using wide Stellite 6 hardfaced seating surfaces, a centralized Inconel spring (which distributes part of the load on both seats as well as compensating for seat wear), and a precision guiding system which eliminates vibration. Bypass valves are recommended to equalize pressure across the disc before opening if the valve is exposed to very high differential pressure.

锻造盒结构
Forged Cage Unit

　　两个滑动阀瓣和大型硬化阀座面都容纳在阀瓣载体内，并与悬臂因科镍弹簧相连。一块板支撑着所有的部件形成盒结构。精加工导轨嵌入载体槽内，在整个运动过程中，进行准确引导。和结构的采用明显降低了阀门的重量，减小了阀门的尺寸，使得阀门底部具有“袋鼠囊”结构的通用的Velan设计的平行滑板阀门更加紧凑。
　　Two slide discs with large hardfaced seating faces are contained in the disc carrier and are in contact with a cantilevered Inconel spring. A plate holds all parts together forming the cage unit. A precision machined guide fits into the carrier slot and provides close guiding during the entire travel. The use of cage construction considerably reduces the weight and size of the Velan design compared to commonly used parallel slide valves with the "kangaroo pocket" in the bottom of the valves.

阀瓣拆卸 Disc disassembled

阀瓣组装 Disc assembled