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Section 1: Classification by Automation and Actuation 1) Automatic valves: Valves that operate automatically relying on the inherent properties of the medium (liquid, air, steam, etc.). Such as safety valves, check valves, pressure relief valves, steam traps, air traps, emergency shut-off valves, etc. 2) Actuated valves: Valves that are operated by manual, electrical, hydraulic, or pneumatic means. Such as gate valves, globe valves, throttle valves, butterfly valves, ball valves, plug valves, etc. Section 2: Classification by Purpose and Function 1) Shut-off valves are primarily used to shut off or allow the flow of fluid in pipelines. Such as stop valves, gate valves, ball valves, plug valves, butterfly valves, diaphragm valves, etc. 2) Check valves are used to prevent the medium from flowing back. Such as check valves of various different structures. 3) Control valves are mainly used to regulate the pressure and flow rate of the medium in pipelines. Such as control valves, throttle valves, pressure relief valves, etc. 4) Diversion valves are used to change the direction of fluid flow in pipelines, serving to distribute, divide, or mix fluids. Such as distribution valves of various structures, three-way or four-way stopcocks, three-way or four-way ball valves, various types of steam traps, etc. 4) Safety valves: Used for overpressure protection by releasing excess fluid and preventing pressure from exceeding specified levels. Such as various types of safety valves. 6) Multi-functional valves are used to replace two, three, or even more types of valves. Such as globe check valves, ball check valves, globe check safety valves, etc. 7) Other special-purpose valves, such as drain valves, vent valves, coking cleaning valves, pigging valves, etc. Section 3 Classification by Main Technical Parameters I. Classification by Nominal Diameter 1) Small-diameter valves: Valves with a nominal diameter of DN≤40mm. 2) Medium-sized valves: Valves with a nominal diameter of DN50-300mm. 3) Large-diameter valves: Valves with a nominal diameter of DN350–1200 mm. 4) Extra-large diameter valves: Valves with a nominal diameter of DN≥1400mm. II. Classification by nominal pressure 1) Vacuum valves: Valves that operate at pressures below standard atmospheric pressure. 2) Low-pressure valves: Valves with a nominal pressure of PN ≤ 1.6 MPa. 3) Medium-pressure valves: Valves with a nominal pressure of PN2.5–6.4 MPa. 4) High-pressure valves: Valves with a nominal pressure of PN10.0–80.0 MPa. 5) Ultra-high pressure valves: Valves with a nominal pressure of PN ≥ 100 MPa. III. Classification by operating temperature of the medium 1) High-temperature valves: valves with t > 450°C. 2) Medium-temperature valves: valves with 120℃ ≤ t ≤ 450℃. 3) Normal temperature valves – valves with -40°C ≤ t ≤ 120°C. 4) Low-temperature valve – Valves for 100℃ ≤ t ≤ -40℃. 5) Ultra-low temperature valves: valves for temperatures t < -100°C. IV. Classification by valve body material 1) Non-metallic material valves, such as ceramic valves, fiberglass-reinforced plastic valves, and plastic valves. 2) Metal material valves such as copper alloy valves, aluminum alloy valves, lead alloy valves, titanium alloy valves, Monel alloy valves, cast iron valves, cast steel valves, low-alloy steel valves, and high-alloy steel valves. 3) Valves with metal valve bodies lined, such as lead-lined valves, plastic-lined valves, and enamel-lined valves. V. Classification by connection method to pipes 1) Flanged valves: Valves that have flanges on their bodies and are connected to pipes using flanges. 2) Threaded connection valves: Valves whose valve body has internal or external threads, allowing them to be connected to pipes via threading. 3) Welded connection valves: Valves that have weld seams on their bodies and are connected to pipes by welding. 4) Clamp-connected valves: Valves that have clamping jaws on the valve body, and are connected to pipes using clamps. 5) Clamp-connected valves: Valves that are connected to pipes using clamps. VI. Classification by operation method 1) Manual valves: Valves that are operated by human effort using things such as hand wheels, handles, levers, or sprockets. When a large torque needs to be transmitted, reduction devices such as worm gears and gears can be used. 2) Electric valves: Valves operated by electric motors, electromagnets, or other electrical devices. 3) Hydraulic or pneumatic valves: Valves that are operated by the pressure of a liquid (such as water, oil, and other liquid media) or air. Section 4: Classification by Structural Features 1) Gate type: The closing element moves along the center line of the valve seat. 2) Gate type: The closing element moves in a direction perpendicular to the center line of the valve seat. 3) The plug and spherical shut-off elements are plungers, conical plugs, or spheres that rotate around their own axis. 4) Swing type: The closing element rotates around an axis outside the valve seat. 5) Butterfly-type: A disc-shaped closing element that rotates around an axis within the valve seat (centerline type) or around an axis outside the valve seat (eccentric type). Section 5: Classification by Structural Principle. Classification by structural principle is currently the most widely used method both domestically and internationally.