API 6A gate valve and gate valve

Globe valve open-close part is plug valve, sealing surfaces appear flat or cone, disc make linear movement along the center line of the seat. Movement of the stem form, also have lift rotating lever, cut-off valve is closed a move along the center line of the valve seat of the valve. According to this mobile form of disc, seat and disc change in his itinerary directly proportional relationship. Because this valve open or close the valve travel relatively short, and very reliable cutting function, and due to the change of his seat and disc stroke proportional relationship, is very suitable for the traffic regulation. Therefore, this type of closure cut-off valve and throttle valve is very suitable for as a cutoff or adjusted.
Cut-off valve, belongs to the forced sealed valve, the valve is closed, must be pressure on the disc, to force a sealing surface does not leak. When medium from the disc below to valve, operating force required to overcome the resistance, is stem and packing friction with the thrust produced by medium pressure, close the valve of the force is greater than the force to open the API 6A gate valve, so it's bigger, the diameter of the stem or stem top bending failure will happen.
According to the connection mode is divided into three types: flange connection, threaded connection, welding connection. From sealed valve, cut-off valve above the medium flow direction is replaced by the disc into the valve cavity, then under the effect of medium pressure, close the valve is small, the force and the force of opening 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 three to had rules in our country, the flow of cut-off valve, shall be applied. This valve should be installed to horizontal cut-off valve opens, the disc of the opening height, for 25% ~ 30% of nominal diameter. Flow has reached maximum, said valve to full open position. So stop valve in full open position, should be determined by disc's schedule.
Control valve, the valve is one of the most widely used, it is popular, is due to open and close in the process of sealing surface friction between the small, more durable, opening, manufacturing easy, convenient maintenance, not only suitable for low pressure, and is suitable for high pressure.
Globe valve closure principle is, depending on the valve rod pressure, the valve sealing surface and the valve sealing surface fit closely, prevent medium circulation.
Globe valve only one-way flow of medium, the installation direction. Cut-off valve structure length greater than gate valves, at the same time, fluid resistance is large, long-running, seal reliability is not strong.
Advantages: simple structure, manufacture and maintenance more convenient. Working stroke is small, opening and closing time is short. Good sealing, small friction between the sealing surface, long service life. As the structure of china valve body has a straight-through, straight and right angle type. Straight-through type is the most common structure, but the maximum resistance of the fluid.
Once-through fluid resistance is small, usually for containing solids or the viscosity of the fluid. Right Angle type body use forging, more suitable for smaller drift diameter, high pressure cut-off valve. In the process of opening and closing gate valve sealing surface friction than small, wear-resisting. Usually only one seal face, good manufacturing process, easy to maintenance.