1. Gate Valve
Also known as gate valve or gate, gate valve and the direction of movement of the gate is perpendicular to the direction of flow, gate valve can only be fully open and full, can not be adjusted and throttled. According to sealing surface configuration can be divided into wedge-type gate valve and parallel gate valve, wedge-type gate valve can be divided into: single gate, double gate and elastic gate; parallel gate valve can be divided into single gate and double gate. According to the screw position of the valve stem, it can be divided into stem gate valve and non-stem gate valve two kinds. Gate valve drive mode classification: manual gate valve, pneumatic gate valve, electric gate valve.
The advantages of gate valve: fluid resistance, sealing surface by the medium of erosion and less; open and close more labor-saving; medium flow is not restricted, non-disturbing flow, not reduce pressure; simple shape, short structure, good manufacturing technology, wide scope of application. Disadvantages of gate valve: Sealing surface between easy to cause erosion and Abrasion, maintenance is difficult; large size, open to require a certain amount of space, open and close time is long; complex structure; easy to deposit solid material in the seat groove and not closed strictly. Therefore, should not be used in the fluid containing fibrous or solid material pipeline. Commonly used in air, steam, oil medium in the pipeline, but also used as a vent valve and low vacuum system valves.
Gate valve is one of the commonly used cut-off valves, mainly used to connect or cut off the medium in the pipeline, not suitable for regulating medium flow. The gate valve is suitable for the pressure, the temperature and the caliber range is very big, is especially suitable for the middle, the big caliber pipeline.
2. Ball Valve
Ball Valve, standard GB/T21465-2008″Valve Terminology” defined as: Open and close pieces (ball) by the stem driven, and around the axis of the stem rotation movement of the valve. It is mainly used for cutting off or connecting the medium in the pipeline, and it can also be used for regulating and controlling the fluid. Among them, the hard seal v-type ball valve has a strong shearing force between the v-type ball core and the metal seat of the hardfaced alloy It is especially suitable for medium containing fiber and small solid particles. The multi-pass ball valve can not only flexibly control the confluent, shunting and the change of flow direction of the medium, but also close any channel and make the other two channels connected. Valves of this type shall generally be installed horizontally in the pipeline. Ball Valve classification: Pneumatic Ball Valve, electric ball valve, manual ball valve.
Ball valve it has 90 degrees of rotation of the action, the plug body for the ball, a circular through hole or channel through its axis. Ball valve in the pipeline is mainly used to do cut, distribution and change the direction of the flow of media, it only needs to rotate 90 degrees of operation and a small torque can be closed tightly. Ball valves are most suitable for use as switch and cut-off valves, but recent developments have designed them for throttling and flow control, such as v-type ball valves.
The main features of the ball valve are its compact structure, reliable sealing, simple structure, convenient maintenance, sealing surface and ball often in closed state, not easily eroded by media, easy to operate and maintain It is suitable for water, solvent, acid, natural gas and other working media, but also suitable for the poor working conditions of the media, such as oxygen, hydrogen peroxide, methane and ethylene, etc. . The ball valve body may be integral or modular.
3. Butterfly Valve
Butterfly Valve also known as the disc valve, open and close for disc plate and can rotate around the axis of the valve body of a valve. The utility model is mainly composed of a valve body, a valve stem, a disc plate and a sealing ring. Valve body is cylindrical, short axial length, built-in disc. Disc driven by the stem, if turn 90, you can complete a one-time open and close. The flow of the medium can be controlled by changing the deflection angle of the plate. The main seal is the seal ring, its material according to the use and media commonly used butterfly valve has a pair of clip-on Butterfly valve and flanged butterfly valve two kinds. Clip-on butterfly valve is a double-headed bolt connecting the valve between the two pipe flange, flange-type butterfly valve is a valve with flange, with bolts on the two ends of the valve flange in the pipeline. Butterfly Valve can be used with pneumatic actuator and electric actuator in every industries.
Butterfly Valve is suitable for producing furnace, gas, natural gas, Liquefied petroleum gas, city gas, cold and hot air, chemical smelting and environmental protection engineering systems to transport a variety of corrosive, non-corrosive fluid medium on the pipeline, used to regulate and cut off the flow of media.
Butterfly Valve is a closed piece (disc or disc) for the disc, rotating around the valve shaft to achieve open and closed a valve, in the pipeline mainly to cut off and throttle role. Butterfly Valve opening and closing piece is a disc-shaped disc, in the body around its own axis rotation, so as to open and close or adjust the goal. Butterfly Valve is usually less than 90 full-close, butterfly valve and butterfly rod itself has no self-locking ability, in order to locate the butterfly plate, to install the worm gear reducer on the valve rod. The use of worm gear reducer, not only can make the butterfly plate with self-locking ability, so that the butterfly plate stopped in any position, but also improve the operation of the valve performance.
The relationship between the butterfly valve opening and the flow rate is basically linear proportional change. If it is used to control the flow rate, its flow rate characteristic is also closely related to the flow resistance of the piping, such as the same diameter and form of the valve installed in the two pipes, and the flow rate of the valve will vary greatly with the different loss coefficient of the piping.If the valve is in the throttling range, the back of the valve plate prone to Cavitation, there is the possibility of damage to the valve, are generally 15 outside the use.
When the butterfly valve is in the middle opening, the opening shape of the valve body and the front end of the butterfly plate is centered on the valve shaft, and the two sides are formed in different states. The Front End of the butterfly plate on one side moves in the direction of the water flowing, and the other side moves against the direction of the water flowing one side of the valve body and valve plate to form a nozzle-shaped opening, the other side is similar to throttle orifice-shaped opening, nozzle side than throttle side flow much faster, and throttle side valve under the negative pressure, rubber seals often fall off.
Butterfly valve operating torque, due to the opening and the direction of the valve opening and closing different values, horizontal butterfly valve, especially large-diameter valve, because of the water depth, the shaft, the head of the difference produced by the torque can not be ignored. In addition, the valve inlet side of the device elbow, the formation of bias, torque will increase. When the valve is in the middle opening, the operating mechanism needs self-locking because of the action of water flow torque.
4. Globe Valve
Globe valve is a forced sealing valve, so when the valve is closed, the pressure must be applied to the disc to force the sealing surface not to leak. When the medium from the bottom of the valve disc into the valve, operating force to overcome the resistance is the friction of the stem and packing and the pressure generated by the medium thrust, closing the valve than open the valve force, so the diameter of the stem to be larger, otherwise there will be a valve stem top bending failure. In recent years, after the emergence of self-sealing Valve, the medium flow direction of the globe valve is changed from the top of the disc into the valve cavity, then under the medium pressure, the force of closing the valve is small, and the force of opening the valve is large, the diameter of the valve stem can be reduced accordingly. At the same time, in the role of the media, this form of valve is also more rigorous. Cut-off valve flow, the use of top-down. Cut-off valve to be installed horizontally. When the globe valve is opened, the opening height of the disc is 25% ~ 30% of the nominal diameter, the flow rate has reached the maximum, indicating that the valve has reached the full open position. Therefore, the full open position of the globe valve, should be determined by the disc stroke.
A Globe valve is a valve in which the closing member (disc) moves along the centerline of the seat. According to this movement of the disc, the change in the seat opening is proportional to the disc stroke. Because the stem of this kind of valve has relatively short opening or closing stroke, and has very reliable cutting function, and because the change of the valve seat opening is proportional to the stroke of the disc, it is very suitable for regulating the flow rate. Therefore, this type of valve is ideal for shutoff or regulation and throttling.
Post time: Nov-25-2021