原文：
　　闸阀是作为截止介质使用，在全开时整个流通直通，此时介质运行的压力损失最小。闸阀通常适用于不需要经常启闭，而且保持闸板全开或全闭的工况。不适用于作为调节或节流使用。对于高速流动的介质，闸板在局部开启状况下可以引起闸门的振动，而振动又可能损伤闸板和阀座的密封面，而节流会使闸板遭受介质的冲蚀。从结构形式上，主要的区别是所采用的密封元件的形式。根据密封元件的形式，常常把闸阀分成几种不同的类型，如：楔式闸阀、平行式闸阀、平行双闸板闸阀、楔式双闸板闸等。最常用的形式是楔式闸阀和平行式闸阀。 截止阀 截止阀的阀杆轴线与阀座密封面垂直。阀杆开启或关闭行程相对较短，并具有非常可靠的切断动作，使得这种阀门非常适合作为介质的切断或调节及节流使用。截止阀的阀瓣一旦处于开启状况，它的阀座和阀瓣密封面之间就不再的接触，并具有非常可靠的切断动作，合得这种阀门非常适合作为介质的切断或调节及节流使用。 截止阀一旦处于开启状态，它的阀座和阀瓣密封面之间就不再有接触，因而它的密封面机械磨损较小，由于大部分截止阀的阀座和阀瓣比较容易修理或更换密封元件时无需把整个阀门从管线上拆下来，这对于阀门和管线焊接成一体的场合是很适用的。介质通过此类阀门时的流动方向发生了变化，因此截止阀的流动阻力较高于其它阀门。 常用的截止阀有以下几种：1）角式截止阀；在角式截止阀中，流体只需改变一次方向，以致于通过此阀门的压力降比常规结构的截止阀小。2）直流式截止阀；在直流式或Y形截止阀中，阀体的流道与主流道成一斜线，这样流动状态的破坏程度比常规截止阀要小，因而通过阀门的压力损失也相应的小了。3）柱塞式截止阀：这种形式的截止阀是常规截止阀的变型。在该阀门中，阀瓣和阀座通常是基于柱塞原理设计的。阀瓣磨光成柱塞与阀杆相连接，密封是由套在柱塞上的两个弹性密封圈实现的。两个弹性密封圈用一个套环隔开，并通过由阀盖螺母施加在阀盖上的载荷把柱塞周围的密封圈压牢。弹性密封圈能够更换，可以采用各种各样的材料制成，该阀门主要用于“开”或者“关”，但是备有特制形式的柱塞或特殊的套环，也可以用于调节流量。 蝶阀 蝶阀的蝶板安装于管道的直径方向。在蝶阀阀体圆柱形通道内，圆盘形蝶板绕着轴线旋转，旋转角度为0°~90°之间，旋转到90°时，阀门则牌全开状态。 蝶阀结构简单、体积小、重量轻，只由少数几个零件组成。而且只需旋转90°即可快速启闭，操作简单，同时该阀门具有良好的流体控制特性。蝶阀处于xx开启位置时，蝶板厚度是介质流经阀体时{wy}的阻力，因此通过该阀门所产生的压力降很小，故具有较好的流量控制特性。蝶阀有弹密封和金属的密封两种密封型式。弹性密封阀门，密封圈可以镶嵌在阀体上或附在蝶板周边。 采用金属密封的阀门一般比弹性密封的阀门寿命长，但很难做到xx密封。金属密封能适应较高的工作温度，弹性密封则具有受温度限制的缺陷。 如果要求蝶阀作为流量控制使用，主要的是正确选择阀门的尺寸和类型。蝶阀的结构原理尤其适合制作大口径阀门。蝶阀不仅在石油、煤气、化工、水处理等一般工业上得到广泛应用，而且还应用于热电站的冷却水系统。 常用的蝶阀有对夹式蝶阀和法兰式蝶阀两种。对夹式蝶阀是用双头螺栓将阀门连接在两管道法兰之间，法兰式蝶阀是阀门上带有法兰，用螺栓将阀门上两端法兰连接在管道法兰上。 球阀 球阀是由旋塞阀演变而来。它具有相同的旋转90度提动作，不同的是旋塞体是球体，有圆形通孔或通道通过其轴线。球面和通道口的比例应该是这样的，即当球旋转90度时，在进、出口处应全部呈现球面，从而截断流动。 球阀只需要用旋转90度的操作和很小的转动力矩就能关闭严密。xx平等的阀体内腔为介质提供了阻力很小、直通的流道。通常认为球阀最适宜直接做开闭使用，但近来的发展已将球阀设计成使它具有节流和控制流量之用。球阀的主要特点是本身结构紧凑，易于操作和维修，适用于水、溶剂、酸和天然气等一般工作介质，而且还适用于工作条件恶劣的介质，如氧气、过氧化氢、甲烷和乙烯等。球阀阀体可以是整体的，也可以是组合式的。 按防止介质倒流选用阀门 这种类型的阀门的作用是只允许介质向一个方向流动，而且阻止方向流动。通常这种阀门是自动工作的，在一个方向流动的流体压力作用下，阀瓣打开；流体反方向流动时，由流体压力和阀瓣的自重合阀瓣作用于阀座，从而切断流动。其中止回阀就属于这种类型的阀门，它包括旋启式止回阀和升降式止回阀。旋启式止回阀有一介铰链机构，还有一个像门一样的阀瓣自由地靠在倾斜的阀座表面上。为了确保阀瓣每次都能到达阀座面的合适位置，阀瓣设计在铰链机构，以便阀瓣具有足够有旋启空间，并使阀瓣真正的、全面的与阀座接触。阀瓣可以全部用金属制成，也可以在金属上镶嵌皮革、橡胶、或者采用合成覆盖面，这取决于使用性能的要求。旋启式止回阀在xx打开的状况下，流体压力几乎不受阻碍，因此通过阀门的压力降相对较小。升降式止回阀的阀瓣座落位于阀体上阀座密封面上。此阀门除了阀瓣可以自由地升降之外，其余部分如同截止阀一样，流体压力使阀瓣从阀座密封面上抬起，介质回流导致阀瓣回落到阀座上，并切断流动。 根据使用条件，阀瓣可以是全金属结构，也可以是在阀瓣架上镶嵌橡胶垫或橡胶环的形式。像截止阀一样，流体通过升降式止回阀的通道也是狭窄的，因此通过升降式止回阀的压力降比旋启式止回阀大些，而且旋启式止回阀的流量受到的限制很少。 按调节介质参数选用阀门 在生产过程中，为了使介质的压力、流量等参数符合工艺流程的要求，需要安装调节机构对上述参数进行调节。调节机构的主要工作原理，是靠改变阀门阀瓣与阀瓣与阀座间的流通面积，达到调节上述参数的目的。属于这类阀门的统称为控制阀，其中分为依靠介质本身动力驱动的称为自驱式控制阀如减压阀、稳压阀等，凡{lx1}上来动力驱动的（如电力 、压缩空气和液动力）称为他驱式控制阀，如电动调节阀、气动调节阀和液动调节阀等。

“ The correct method of valve selection ”是由提供的阀门行业新闻，译文仅供参考。另外，中国减压阀网还提供相关产品搜索： 、 、 、 、 等。

译文：
Valve is used as a cut-off media, the flow through the fully open, then the pressure medium to run minimal loss. Valve usually does not require frequent opening and closing apply, and maintain the gate fully open or fully closed condition. Does not apply to the use as a regulator or throttle. For high-speed flow of medium, open the gate in the local conditions can cause the vibration of the gate, while the vibration it may damage the gate and the seat of the sealing surface, and cutting medium will suffer erosion gate. From a structural form, the main difference is that the sealing component used in the form. According to the form of seals, often divided into several different types of valve, such as: wedge gate valves, parallel gate valve, Parallel Gate Valve, Wedge Gate, etc. double plate. The most common form of parallel wedge gate valves and gate valves. Valve The stem valve seat sealing surface and the vertical axis. Valve stem to open or close the relatively short trip, and have very reliable cutting action, making this valve is suitable for medium-conditioning and cutting off or use. Cut-off valve in the open position when the valve flap, and its seat and disc sealing surface is no longer between the contacts and have very reliable cutting action, and combine this valve is suitable for medium cut or regulation and throttle use. Once the valve is turned on, its seat and disc sealing surface contact between the longer, so it's sealing surface mechanical wear small, as most of the cut-off valve seat and disc easily repaired or replaced seals without having to remove the valve from the pipeline to which the valves and pipes welded into one of the occasions are very applicable. Medium through the valve when the flow direction of such a change, so a higher cut-off valve of the flow resistance in the other valve. Commonly used cut-off valves are the following: 1) angle-type valve; in the angle-type valve, the fluid change only one direction, so that the pressure drop through the valve structure than conventional globe valves. 2) DC-type valve; in the DC-type or Y-shaped valve, the valve body and the main channel flow into a slash, so the damage flow state is smaller than the conventional cut-off valve, so the pressure losses through the valve accordingly smaller. 3) The plunger-type valve: This form of cut-off valve is a variant of conventional valves. In the valve, the valve disc and seat are usually designed based on the plunger principle. Polished into a flap valve connected between the plunger and valve stem seal is set in the plunger on the realization of the two elastomeric seals. Two elastic rings separated by a ring, and through the valve cover nut load exerted on the valve cover seals around the plunger pressure prison. Elastic ring can be replaced, you can use variety of materials, the valve is mainly used for "open" or "off", but with a special form of plunger or special ring can also be used to adjust flow. Butterfly Butterfly valve panels installed on the pipe diameter direction. Cylindrical channel in the valve body, disc-shaped disc around the axis of rotation, rotation angle 0 ° ~ 90 ° between the rotation to 90 °, the valve is open all license conditions. Butterfly simple structure, small size, light weight, only by a few parts. But only 90 ° rotation to quickly open and close, easy, and the fluid control valve has good features. Butterfly valve is fully open position, the disc thickness is only when the medium flows through the body resistance, thus generated by the valve pressure drop is small, it has a better flow control characteristics. Butterfly valve with elastic metal seal and the seal of two seal types. Flexible sealed valves, seals can be mounted on the body or attached to the disc periphery. Metal sealed valves generally higher than the valve seal flexible, long life, but it is very difficult to completely seal. Metal seal can adapt to high temperature, flexible seal is restricted by temperature, the defects have. If asked to use as a flow control valve, the main choice is the right size and type of valve. Butterfly valve structure principle is particularly suitable for production of large diameter valves. Butterfly not only in oil, gas, chemicals, water treatment, widely used in general industry, but also for the thermal power station cooling water system. Common butterfly valve wafer type butterfly valve and flange type butterfly valve two. Wafer type butterfly valve is the valve stud connection between two pipe flanges, flange type butterfly valve is a valve with a flange with bolts on both ends of the valve in the pipe flange connection method Lan on. Ball Evolved from the plug valve. It has the same movement raised 90 degrees, is the cock body is different sphere, there are circular holes or channels through its axis. The ratio of the sphere and the openings should be such that when the ball is rotated 90 degrees, the import and export office should be fully present sphere, thus cutting off the flow. Only need 90 degrees ball valve operation and a small rotation torque can be closed tightly. Full equality for the medium body cavity to provide a little resistance, through the flow channel. Generally considered the most suitable valve opening and closing used directly to do, but the recent development has been designed to make it a throttle valve and flow control purposes. Valve itself, the main characteristics of compact structure, easy operation and maintenance for water, solvents, acids, and natural gas general working media, but also to poor working conditions of media, such as oxygen, hydrogen peroxide, such as methane and ethylene . Ball valve can be integral, it can be modular. Use the valve to prevent backflow by media The role of this type of valve is the only allowed media to flow in one direction, and stop the flow direction. Usually the valve is automatically work in a direction of flow of fluid pressure, the valve flap to open; fluid flow the opposite direction, by the fluid pressure and the valve flap from the coincidence of disc acting on the valve seat to cut off flow. Which belongs to this type of valve the valve, which includes swing check valves and lift check valves. Swing check valves are ordinary hinge, there is a door the same disc as the freedom to tilt the seat leaning against the surface. In order to ensure that the flap valve seat face every time to reach the appropriate position, the valve flap design in the hinge so that the valve flap is enough to swing space, and make a real disc, comprehensive engagement with the valve seat. All metal disc can be made of metal can also be embedded in the leather, rubber, or synthetic cover, depending on performance requirements. Swing check valve in the fully open position, the fluid pressure is almost free of obstruction, therefore the pressure drop through the valve is relatively small. Lift check valves on the valve seat is located in the valve body sealing surface. In addition to this valve disc is free to lift, the other part of the same as the cut-off valve, the fluid pressure valve from the valve seat sealing surface of valve lift, medium return led to a seat on the disc down and cut off the flow. According to terms of use, the valve flap can be all metal construction, it can be rack mounted in the valve flap rubber mat or rubber ring form. The same as the cut-off valves, fluid channels through the lift check valve is narrow, so the check valve by lifting the pressure drop than the swing check valve a little bigger, and swing check valves for flow restrictions few. Medium parameters are chosen by adjusting the valve In the production process, in order to make the medium pressure, flow and other parameters meet the process requirements, need to install the adjusting mechanism to adjust these parameters. Adjusting mechanism and the operating principle, is by changing the valve disc and valve seat between the valve and the flow area to achieve the purpose of adjusting the above parameters. Such valves are referred to as control valves, which are divided into power-driven dependent media itself is called self-drive control valve such as valve, regulator valve, all leading up power-driven (such as electricity, compressed air and fluid power) as his driving style control valves, such as the electric control valve, pneumatic control valve and hydraulic control valve.