译文：
1、概述 用于火电厂高加疏水、再热器疏水和过热器疏水等系统疏放水的关闭与排放阀门密封要求高,须快开快闭,并具有故障保护功能、自动控制功能和较高的可靠性。因此气动控制截止阀(电厂俗称疏水阀,疏水门)成为这类系统的{sx}产品。气动控制截止阀密封比压持久稳定,调试简单,维护要求低,故障低,可靠性高,失气失电自动保护,快速启闭,价格相对低廉,节能环保,因而适用于火电厂疏放水工况。 2、阀门及气动执行机构的选型 气动控制截止阀一般为全开全闭式。从流量特性考虑,截止阀和球阀具有启闭行程短,速度快,密封可靠,启闭静态力矩小等特点,因而两类产品都得到应用。但从可靠性考虑,主流产品仍然是气动截止阀。 气动控制装置的气缸为定型产品,依作用方式可分单作用和双作用两种。单作用产品带复位圆柱弹簧,具有失气自动复位功能,即失气时气缸活塞(或膜片)在弹簧作用下,驱动气缸推杆回复到气缸初始位置(行程的原始位置)。双作用气缸无复位弹簧,推杆进退须依靠变换气缸气源的进出口位置。气源从活塞上腔进时,推杆向下运动。气源从活塞下腔进时,推杆向上运动。由于不带复位弹簧,双作用气缸对比同径单作用气缸具有更大的推力,但不具备自动复位功能。显然不同的进气位置使推杆有不同的方向运动。当进气位置在推杆的背腔时,进气使推杆前进,这种方式称为正作用气缸。反之进气位置在推杆同侧时,进气使推杆后退,这种方式称反作用气缸。气动截止阀因为一般需要失气保护功能,通常选用单作用气缸。 从分析可知,当阀门保护方式为失气打开时,必须选择单作用的正作用气缸。当阀门的保护方式为失气关闭时,必须选择单作用的反作用气缸。单作用的正作用气缸在阀门关闭时必须维持持久的稳定气源压力,对气源的稳定性和持久性要求较高常闭阀尽可能地避免选择这种设计,此结构适用于常开阀。单作用的反作用气缸适用于常闭阀,但对于弹簧的要求较高,应具有稳定持久的弹力。 3、气缸推力计算 除了作用方式的选择,计算所选气缸推力是计的重要工作,以常见的常闭式气动截止阀为例分析。因压力较高,为尽可能选择较小的气缸,采用了上进流(倒流)的阀门设计方式。为提高密封比压,采用了锥形密封面。 3.1、气缸关闭力的计算 关闭状态受力分析得各力为 式中Qt———填料摩擦力,N Qj———介质静压力,N Qf———阀杆截面的介质推力,N Qm———阀门达到必须密封比压时的密封面作用力,N Qg———气缸关闭时输出力,N Qk———气缸打开时输出力,N qMF———密封面必须比压,MPa dm———密封面平均直径,mm df———阀杆直径,mm f———填料摩擦系数 bt———填料宽度,mm P———阀门设计压力,MPa fm———密封面摩擦系数 要实现阀门的有效密封,必须 Qg-Qf-Qt+Qj≥Qm 即 Qg≥Qf+Qt+Qm-Qj 关闭力也不是越大越好,还须校核密封面实际比压q,并使其小于许用比压[q] 式中Qm′———作用于密封面的实际密封力,由气缸实际推力减去相关阻力得出,MPa, 通过以上计算可确定关闭状态的弹簧预紧力,为弹簧选型确定依据。 3.2、开启状态气缸力的计算 开启瞬间阀门受力分析。 Qk≥Qt+Qj+Qg-Qf 当阀门被打开后,Qj会消失为零,但Qg会逐渐增加,两者部分抵消,到开启行程末端({zg}位),气缸推力Qk′为 Qk′≥Qt-Qf+Qs′ 式中Qs′———此位置弹簧的压缩力,N比较以上两式确定其中较大者为气缸推力,再根据实际输入气源额定压力,可大致推算出所选择气缸的直径,考虑一定的安全系数,最终确定气缸规格。 4、出厂试验 工厂型式试验是确认产品性能的重要依据,通过试验可确认阀门的设计加工质量,承压能力,启动装置的动作性能,一般应进行密封试验、壳体试验和动作试验。 (1)密封试验 撤除气源,让弹簧复位至阀门关闭后,从设计流向向阀芯密封面逐步加压,进行承压密封试验,全程分3～4个压力阶段,分别观察阀门各阶段保压性能,到{zg}设计压力的1.1倍压力为止均应无泄漏。以此验证阀门在压力波动时也能稳定密封。 (2)壳体试验 依公称压力的115倍进行水压壳体试验,观察填料部位、中法兰垫片各处以及壳体全表面应无渗漏。 (3)动作试验 阀门关闭后,将阀门打压到设计压力,给气缸通气(压力控制0.4～0.45MPa)确认能否开启阀门,能否达到设计行程,到达设计行程后撤除气源,阀门应能自行复位。此试验至少反复3次以上。 5、附件 除阀门和气缸外,气动截止阀应配备电磁阀、行程开关、调压阀(含过滤器、油雾器,即三联件)和手动装置等。对电磁阀一般单作用气缸选择二位三通,并按安装位置确定电磁阀的结构形式。行程开关可选择摇臂式,调整方便。三联件用于气源处理及压力调节,如气源统一处理,可不必单配。手动装置用于辅助强制密封,分为上装式和侧装式,配置应考虑安装空间及合同规定。连接管及管件应选择金属材料,因介质温度比较高。支架尽可能高一些,使气缸内部橡胶件远离热源,延长内部橡胶密封件的使用寿命。 6、结语 气动截止阀可广泛应用于火力发电厂疏放水系统,控制介质的通断,具有普通手动或电动截止阀无法比拟的优点,但由于气动装置结构较大,应考虑有足够的阀门安装空间,因而高压大口径阀门的应用受到限制。

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原文：
1, an overview of For thermal power plant of high pressure hydrophobic, reheater, superheater hydrophobic and the hydrophobic drainage systems such as the closure of sparse and the discharge valve sealing requirements in need of quick open soon closed, and has fault protection features, automatic control functions and high reliability. Therefore, pneumatic control valve (commonly known as trap plants, hydrophobic gate) to become the preferred products of such systems. Pneumatic control valve sealing pressure than the long-lasting stability, easy adjustment, low maintenance requirements, failure is low, high reliability, loss of gas lost electricity automatic protection, quick open and close, relatively inexpensive, energy saving and environmental protection, and thus turn on the water for thermal power plant dredging working conditions. 2, valve and pneumatic actuator selection Pneumatic control valve is normally full-full-closed. From the flow characteristics to consider cut-off valve and ball valve with a hoist travel a short, fast, sealed and reliable, open and close a small static torque characteristics, and thus two types of products are applied. However, considering the reliability of mainstream products are still a pneumatic valve. Pneumatic cylinder control device for shaping products, according to mode of action can be divided into single-and dual role of the two kinds of roles. Single product with reset cylindrical spring, with loss of gas automatic reset function, which is lost when the gas cylinder piston (or diaphragm) in the spring under the effect of putting the cylinder back to the cylinder driving the initial location (the original location of travel). Double-acting cylinder no reset spring, putting retreat will depend on the changing position of the cylinder import and export of gas source. Gas source from the chamber into the piston when putting downward movement. Gas source from the piston into the next chamber, the putting upward movement. Because they do not with reset spring, double acting cylinder contrast to the role of a single cylinder with diameter greater thrust, but does not have the automatic reset function. Distinctly different intake location so putting a different direction. When the inlet position in putting on the back cavity, the inlet so that putting forward the positive function in this way is called the cylinder. On the contrary position in putting the ipsilateral inlet when the inlet so that putter back, said reaction cylinder in this way. Pneumatic valve because the general need for gas loss protection function, usually the role of selected single-cylinder. From the analysis we can see, when the protection mode for the loss of gas valve is open, you must select a single role in the positive role of the cylinder. When the valve of protection for the loss of gas is turned off, you must select a single role of the reaction cylinder. Single positive role of the cylinder valve is closed must be maintained in the long-lasting stability in gas supply pressure to the gas source of stability and persistence often require a higher closing valve as much as possible to avoid the selection of this design, this structure applies to regular open valve. One role of the reaction of the cylinder valve closed for regular, but for the spring are higher, and should have a stable and lasting resilience. 3, cylinder thrust calculation In addition to the choice of mode of action, calculate the selected cylinder thrust move is an important work to a common regular closed pneumatic valve for example analysis. Due to the higher pressure, in order to choose a smaller cylinder as much as possible, using upward mobility flow (reflux) valve design approach. To improve sealing specific pressure, using a cone-shaped sealing surface. 3.1, the calculation of the cylinder closing force Off force analysis was the force of Where Qt --- packing friction, N Qj --- medium static pressure, N Qf --- stem cross-section of the media thrust, N Qm --- valve to be sealed when the sealing surface than the pressure force, N Qg --- closed cylinder output force, N Qk --- open cylinder output force, N qMF --- sealing surface must be specific pressure, MPa dm --- sealing surface mean diameter, mm df --- Stem diameter, mm f --- packing coefficient of friction bt --- filler width, mm P --- valve design pressure, MPa fm --- sealing surface friction coefficient To achieve an effective sealing valve must be Qg-Qf-Qt + Qj ≥ Qm That Qg ≥ Qf + Qt + Qm-Qj Closing force is not the bigger the better, must actually higher than check of the sealing surface pressure q, and make it less than the allowable pressure [q] Where Qm' --- acting on the sealing surface of the actual seal edge, from the real thrust of the cylinder minus the associated resistance to draw, MPa, Through the above calculations to determine the off spring preload for the spring determine the basis for selection. 3.2, open state of cylinder force calculation Instantaneous valve opening force analysis. Qk ≥ Qt + Qj + Qg-Qf When the valve is opened, Qj will disappear to zero, but Qg will gradually increase, partially offset by the two to open the trip ends (highest), the cylinder thrust Qk 'for the Qk '≥ Qt-Qf + Qs' Qs' --- this location where the compression spring force, N comparing the above two-type to determine which is greater thrust of the cylinder, and then rated based on the actual input gas supply pressure can be roughly calculate the diameter of the cylinder of choice, consider a certain degree of safety factor to finalize cylinder specifications. 4, factory test Plant type test is to confirm an important basis for product performance through testing can confirm the quality of design and processing valves, pressure capabilities, start the device moves the performance in general should be sealed test, test shell test and action. (1) Seal Test Removal of gas source, so that spring to reset the valve closed, the flow from the design phase to the spool sealing surface pressure, for pressure sealing test, full sub-pressure phase of 3 to 4 were observed at all stages holding pressure valve performance, to the highest pressure of 1.1 times the design pressure shall be no leakage so far. As a validation of pressure fluctuations valves can also be a stable seal. (2) shell test Carried out in accordance with nominal pressure of 115 times the pressure shell test, observe the filling position, the flange gaskets, as well as throughout the entire surface of the shell should be no leakage. (3) Action Test The valve closed, the valve pressure to design pressure, to the cylinder ventilation (pressure control of 0.4 ~ 0.45MPa) to confirm whether to open the valve, can meet the design itinerary, arriving after the removal of gas supply planning an itinerary, the valve should be able to self - reset. Repeated this experiment at least three more times. 5, Annex In addition to the valve and cylinder, the pneumatic valve should be equipped with solenoid valves, limit switch, pressure regulating valve (including filters, oil mist device, that is, triple pieces) and manual devices. The role of the solenoid valve on a single-cylinder option two links, according to the installation location to determine the structure of the form of solenoid valve. Travel switch selectable rocker style, easy to adjust. FRL for the air source treatment and pressure regulation, such as the gas source unity, may not have a single distribution. Manual device for supporting a mandatory seal is divided into upload and side-mounted type, configuration, should consider the installation space and the contract. Connecting pipes and pipe fittings should be selected metallic materials, due to relatively high temperature of medium. Stand as high as possible a number, so that the internal rubber cylinder away from heat, extending the life of the internal rubber seals. 6 Conclusion Pneumatic cut-off valve can be widely used in thermal power plant dredging drainage system to control the media off, with general manual or electric cut-off valve can not match advantage, but because of large pneumatic device structure should be considered sufficient valve installation space, and therefore the application of high-pressure large-diameter valves is limited.