The usage and working principle of pneumatic cut-off valve
Pneumatic cut-off valve opening and closing is plug valve, sealing surfaces appear flat or cone, disc make linear movement along the centerline of fluid. Stem form of exercise, lifting lever ( Valve rod and hand wheel lifting) And lift rotating lever ( Hand wheel rotating lifting with the valve stem and nut in the body) 。 Globe valve used throughout close tu, don't allow to adjust and throttling. Cut-off valve belongs to compulsory sealed valve, the valve is closed, must be pressure on the disc, to force a sealing surface does not leak. When medium by disc below into the valve 6, the operating force needed to overcome the resistance, is stem and packing of the friction force and the thrust produced by medium pressure, close the valve strength is stronger than open the valve, so it's bigger, the diameter of the stem or stem top bending failure happens. From sealed valve, cut-off valve is replaced by the disc above the medium flow direction into the valve cavity, in the medium pressure at this moment, close the valve of the force is small, and the strength of the valve, the valve stem diameter can be reduced accordingly. At the same time, in the role of media, this kind of valve is tight. Valve in China 'three for' regulation, the flow of cut-off valve, shall be applied. Electric butterfly valves, electric gate valves, electric valve, explosion-proof electric 3-way ball valve pneumatic cut-off valve working principle: the cut-off valve opens, the opening of the disc height, is 25% ~ 30% of nominal diameter, flow has reached maximum, said valve to full open position. So stop valve fully open position, should be determined by disc's schedule. Globe valve has the following advantages: simple structure, manufacture and maintenance more convenient. Working stroke is small, opening and closing time is short. Good sealing, sealing surface friction between the small, long service life. Globe valve faults are as follows: fluid resistance is big, required when opening and closing force is larger. Do not apply to the medium with larger particles, viscosity, easy to coking. Poor regulation performance. The kinds of cut-off valve according to the position of the stem thread with external thread type, internal thread type. According to the flow of medium, have straight-through type, straight and Angle. Cut-off valve, the form of the seal packing seal globe valve and bellows seal globe valves.