Thread Content
Another classification of valves: There are many types of valves. There are large and small ones; the large ones are big enough for a person to enter, while the small ones aren’t even big enough to fit a finger inside ； There are simple ones ； Some are valuable, some are ordinary ； There are metallic ones and non-metallic ones ； ……. Its applications span industrial sectors such as petroleum, chemicals, fertilizers, pesticides, synthetic plastics, synthetic fibers, synthetic rubber, food, pharmaceuticals, and hydropower, as well as areas like national defense, scientific research, transportation, agriculture, and even domestic facilities. Valves are far more numerous than the main components, but in production equipment they often play a secondary role and do not receive as much attention as the main equipment. Due to the advantage in quantity and the disadvantage in attention given, phenomena such as leaks, spills, and other forms of loss of fluid in factories, as well as accidents resulting therefrom such as fires, explosions, poisonings, and burns, often occur at valves. Due to the large number of valves, the cumulative losses are astonishing! Therefore, it is crucial to install and use valves properly, as this can prevent or reduce leakage losses, production shutdown losses, severe damages, and investment losses. It is incorrect to focus only on the main equipment while ignoring the valves. Things are always in a dialectical unity; although under normal circumstances there is a primary-secondary relationship between the main equipment and the valves, if the \"secondary\" element is lost, the \"primary\" element loses its meaning as well. For example, in a continuously operating facility, if the pipeline valves are damaged, the main equipment such as stacks, furnaces, towers, machines, and pumps has to remain idle as well. It is not uncommon to see cases where entire systems fail to function properly due to valve failures. We should draw lessons from this and, following the principle of focusing on the key aspects while also taking into account other elements, carefully study the use of valves while ensuring proper management and utilization of the main equipment. To use valves correctly, it is essential to have a thorough understanding of valves and the wide variety of valve types available. How can we understand it comprehensively? That’s where classification methods and anatomical methods come in. Here, we first introduce the classification, models, and markings of valves. Valves can be classified from different perspectives. 1. Classified by power: 1) Automatic valves – valves that operate based on the force of the medium itself. Such as check valves, pressure relief valves, steam traps, safety valves, etc. 2) Actuated valves: Valves that are operated by external forces such as human power, electrical power, hydraulic power, or pneumatic power. Such as stop valves, throttle valves, gate valves, disc valves, ball valves, plug valves, etc. 2. Classified by structural characteristics: 1) Gate type – the closing element moves along the center line of the valve seat. 2) Gate type: The closing element moves along a center line perpendicular to the valve seat. 3) Plug-type shutters are plungers or balls that rotate around their own central axis. 4) Swing type: The closing element rotates around an axis outside the valve seat. 5) Disc-type shutters are disks that rotate around an axis within the valve seat. 3. By purpose: 1) Cutting-off use – used to cut off or connect the medium in pipelines. Such as stop valves, gate valves, ball valves, plug valves, etc. 2) Adjusting: Used to adjust the pressure or flow rate of the medium. Such as pressure relief valves, control valves. 3) Distribution: Used to change the flow direction of the medium and serve a distribution function. Such as three-way cocks, three-way stop valves, etc. 4) Check valve: used to prevent the medium from flowing back. Such as check valves. 5) Safety use: It releases excess medium when the pressure of the medium exceeds the specified value, to ensure the safety of the equipment. Such as safety valves, emergency valves. 6) For gas blocking and drainage: retains gas and removes condensed water. Such as check valves. 4. Classified by operation method: 1) Manual valves – valves that are operated by human effort using elements such as hand wheels, handles, levers, sprockets, gears, and worm gears. 2) Electric valve: A valve that is operated using electricity. 3) Pneumatic valves: Valves that are operated using compressed air. 4) Hydraulic valves: Valves that are operated by using liquids such as water or oil to transmit external force. 5. Classified by pressure: 1) Vacuum valves: Valves with an absolute pressure of less than 1 kilogram per square centimeter. 2) Low-pressure valves: Valves with a nominal pressure of less than 16 kilograms per square centimeter. 3) Medium-pressure valves: Valves with a nominal pressure of 25–64 kilograms per square centimeter. 4) High-pressure valves: Valves with a nominal pressure of 100–800 kilograms per square centimeter. 5) Ultra-high pressure: Valves with a nominal pressure of 1000 kilograms per square centimeter or higher. 6. Classified by medium temperature: 1) Ordinary valves are those suitable for media operating temperatures ranging from –40 to 450°C. 2) High-temperature valves are valves suitable for media operating at temperatures of 450 to 600°C. 3) Heat-resistant valves: Valves suitable for use with media at working temperatures of over 600°C. 4) Low-temperature valves: Valves suitable for media operating temperatures ranging from –40 to –70°C. 5) Cryogenic valves are valves suitable for media operating at temperatures ranging from –70 to –196°C. 6) Ultra-low temperature valves: Valves suitable for media operating at temperatures below –196°C. 7. Classified by nominal diameter: 1) Low-diameter valves – valves with a nominal diameter of less than 40 millimeters. 2) Medium-bore valves: Valves with a nominal diameter of 50 to 300 millimeters. 3) Large-diameter valves: Valves with a nominal diameter of 350 to 1200 millimeters. 4) Extra-large diameter valves: Valves with a nominal diameter greater than 1400 millimeters. The classifications mentioned above are not absolute; it is also possible to classify valves from other perspectives. However, mastering these basic classifications is very helpful for us to understand the wide variety of valves available.