The valve is based on the medium pressure of the pipeline itself as a power source for opening and closing and adjusting. Different combinations of the pilot valve and the system small pipe can have nearly 30 kinds of functions and are gradually being used more commonly. ? Pilot valve by the control object as the water level and pressure changes and action, as a large number of pilot valve can be used alone or in combination, you can get the main valve on the water level and pressure and flow, etc., separately or in combination Function But the main valve is similar to the globe valve, the valve is fully open, the pressure loss is much larger than other valves, and each opening loss coefficient is more close with the full closure, the more drastic increase in valve diameter is more significant. Valve with the above characteristics, near full closure, the valve action is accelerated, prone to water hammer (water impact pressure), close to fully closed, the slower the valve action as possible, so you can set the valve flap Flow institutions. In addition, the pilot valve throttling and the action part should try to avoid setting a special small aperture to avoid clogging. If necessary, add filters, regular maintenance and set up by-pass pipeline. This valve development, the use of promising.