There are three kinds of cut-off valve selection

Cut-off valve is one of the automation system of actuators, pneumatic diaphragm actuator by a more spring or floating piston actuators and pneumatic control valve, the reception of the regulating instrument signal, fluid control technology of the pipe on the cut, or switch. It has a simple structure, sensitive reaction, reliable operation, etc. Can be widely used in petroleum, chemical, metallurgical and other industrial production. Pneumatic cut-off valve of air required by the compressed air filter, flowing through the valve body is supposed to be free of impurities and particles of the medium of liquid and gas. According to allow the pressure differential, medium characteristics and process piping requirements, can choose single seat, sleeve, tee cut-off valve. Structure in terms of cutting effect, the choice of quarter-turn valves than straight trip valve ( Such as single seat valve, sleeve valve, gate valve, etc. ) More simple structure, reliable sealing effect more, have more advantages. More representative three partial hardness sealing butterfly valve, ball valve, etc. The choice of sealing surface 1) Face to face seal: common plunger valve core, the sealing surface is 60 & deg; The width of the small cone, the small cone usually at 0. 5 mm ~ 2 mm, between two cone to seal it is necessary to ensure good contact. But, in fact, it is always under the influence of processing error ( Such as concentricity, roundness, gradient, etc. ) , the sealing effect is not very ideal. This kind of valve leakage rate is usually 10 - 4, the precision can reach 10 - after grinding 6, can reach higher protection class. 2) Spherical seal using spherical sphere rotating and fixed valve set small cone and tangent, for line contact between them, it's better than the seal face to face. Ball valve, such as spherical sealing butterfly valve is to use this approach to production, the leakage rate of 10 - 6 ~ 10 - 8, high performance of triple eccentric butterfly valve can be up to 10 - 8, even zero leakage. The choice of sealing material 1) Soft seal in addition to the corrosion resistant lining of the valve, the general soft seal valve refers to the valve or valve seat with non-metallic materials (either Mainly for the teflon and rubber, etc. ) The valve in the form of sealing. Soft sealing valve sealing effect is best, but in the cleaning of pipe installation, the system is likely to leave not clean debris (more or less Such as welding slag, iron filings, etc. ) , they through the pneumatic control valve, easy to put the soft sealing valve seat or valve core scratch, increase leakage and sealing reliability is poor. So, choose soft sealing structure medium must be considered strictly before flushing pipeline cleaning and was put into operation.