如何选用进口的自力式调节阀
进口自力式压力调节阀因为不需要其它外来能源如电源、气源，仅靠介质自身的能量来驱动，既节能又环保，使用方便，安装完毕后设定好压力值即可投入自动运行，所以在对控制精度要求不高，又缺乏电源、气源的场合，得到了越来越广泛的使用。美国威盾VTON主要有用于调节流量的进口自力式流量调节阀，用于调节温度的进口自力式温度调节阀，用于控制压力的进口自力式压力调节阀，
不过，这种阀门也需正确选型和正确安装、使用，才能保证投入运行后不出现什么问题。选型方面就不用多说了，比如调节阀是用来控制阀前压力（控制阀前压力调节阀）阀后压力（控制阀前压后调节阀），介质是常温还是高温，有无腐蚀性，*高工作压力等等，一定要事先搞清楚，我们主要谈谈安装使用方面的问题。因为我*近碰到一例自力式压力调节阀的使用方面出现的问题，很有代表性。阀门是用在蒸汽管道上的，投入使用才短短一两个月，用户就报修。到现场一看，大量蒸汽从调节阀膜头的排气孔中排出，噪声极大，声势惊人。事故原因，明显是蒸汽没经过冷凝，直接进入膜头，烧坏了膜片。用于蒸汽管道的自力式压力调节阀，安装时必须在执行器和管道之间加一个冷凝罐，不能让蒸汽进入执行器膜头，而且，调节阀必须头朝下安装，冷凝罐要高于膜头，初次使用，一定要将冷凝罐和膜头中加满水。看现场的安装方式，询问现场仪表人员，这些都没问题，那么是什么造成的呢？令人百思不得其解。后来，仔细询问了一个操作工，无意之下得知：这台阀门安装、投入使用后，冷凝罐和膜头之间的铜管接头一直在断断续续地漏水。原来是这样，漏水导致冷凝罐里的水慢慢漏光，蒸汽就进入膜头，烧坏了膜片。由此可见，自力式压力调节阀在蒸汽管道上使用时，安装、维护方面一定要多加注意，为保证调节阀正常运行，千万不能让接头漏水，不能让冷凝罐缺水，要定期检查，适时加水。其实，不光是自力式压力调节阀，就是其它的自力式调节阀，在使用时也需注意维护和保养才行。另外，蒸汽压力如果较高，*好选用活塞式执行器，而不取薄膜式执行器，因为膜片一般能承受的压力不超过0.4Mpa，过此虽然能用，却要大大降低使用寿命。
尤其要提到的是当要控制的压力低于5kp的时候，要选用带指挥器的自力式压力调节阀，此阀门主要用于微压的控制，氮封装置场合。
Self-pressure regulating valve used Self-pressure regulating valve because there is no other external energy sources such as power, gas supply, relying on the media's own energy to drive, both energy saving and environmentally friendly, easy to use, after installation you can put pressure value set to run automatically, so in the control accuracy is not required, the lack of power, gas supply of the occasion, has been more widely used. However, this valve also need the correct selection and proper installation, use, put into operation to ensure there are no any problems. Needless to say the selection of areas, such as the control valve is used to control valves or valve before the pressure after the pressure medium is at room temperature or high temperature, with or without resistance, the maximum working pressure, etc., must first find out, we mainly discuss the about installation problems. I recently came across one case of self-pressure regulating valve used in problems, very representative. Valve is used in the steam pipe, and put into use until a month or two, the user repair. To the scene and saw a lot of steam control valve membrane from the vent in the discharge head, a great noise, momentum amazing. Cause of the accident, was not through the condensation of steam directly into the membrane head, burn the diaphragm. Self-piping for steam pressure control valve must be installed between the actuator and pipe plus a condensation tank, can not let the steam into the head actuator membrane, and the control valve must be installed upside down, condensate tank is higher than film head, initial use, be sure to head in the condensate tank and fill the water film. Look at the installation site, ask live instrumentation personnel, these no problem, then what is causing it? Baffling. Later, asked in detail about an operator, under the intention that: this valve is installed, put into use, condensate tanks and brass fittings between the first film has been leaking intermittently. The original is the case, leading to condensation tank leaking slowly leaked water, steam enters the membrane first, burn the diaphragm. Thus, the self-pressure regulating valve used in the steam pipe, installation, maintenance must pay more attention to ensure the normal operation of control valve, do not let joint leakage, condensation can not allow water to regular inspection, timely add water. In fact, not only is the self-pressure regulating valve, is that other self-regulating valve, when in use also need to pay attention to maintenance and maintenance of the job. In addition, if a higher vapor pressure, the best selection of piston-type actuator, rather than take the film actuator, because the pressure diaphragm is generally no more than 0.4Mpa, although this can be used too, have greatly reduced service life.