Core knowledge of butterfly valves, gate valves, and ball valves: understanding selection and application

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In fluid conveying systems, butterfly valves, gate valves, and ball valves are the three most widely used types of control valves; their structural designs, performance characteristics, and applicable scenarios each have their own emphases. Guided by the principles of “precise distillation and practical orientation”, this article summarizes the key essentials for three types of valves, aiming to facilitate industrial selection, routine maintenance, and the accumulation of professional knowledge. The entire text strikes a balance between professionalism and readability, while avoiding any redundant expressions. The butterfly valve utilizes a disc-shaped butterfly plate as its main closing element; it rotates 0°–90° around the axis within the valve body to open or close the flow. Thanks to its compact structure and cost-effectiveness, it is the preferred choice for large-diameter applications under low-pressure conditions. Its 10 key points are as follows: Classification of butterfly valves 1. By sealing type: soft-sealed butterfly valves (rubber, PTFE seats) and hard-sealed butterfly valves (metal seats). 2. Classified by structural form: centerline vertical plate butterfly valves, eccentric butterfly valves (single-eccentric, double-eccentric, triple-eccentric). 3. Classified by actuation method: manual butterfly valves, pneumatic butterfly valves, electric butterfly valves, hydraulic butterfly valves. 4. Classified by pressure rating: vacuum butterfly valves, low-pressure butterfly valves, medium-pressure butterfly valves, high-pressure butterfly valves. 5. Classified by medium of flow: water supply and drainage butterfly valves, gas butterfly valves, corrosion-resistant butterfly valves, high-temperature butterfly valves. 1. D71X-10Q: Manual wafer-type midline soft-seal butterfly valve, for low-pressure applications in municipal water supply and drainage systems. 2. D973H-16C: Electric wafer-type triple-eccentric hard-seal butterfly valve, suitable for high-temperature flue gas and steam pipelines. 3. D641F-10P: Pneumatic flange-type midline soft-seal butterfly valve, used for transporting chemical acids and alkalis. 4. D371J-16Q: Worm gear-driven wafer-type rubber-lined butterfly valve, appropriate for handling particulate-containing media such as mine tailings and sewage. 5. D943W-25P: Electric flange-type triple-eccentric hard-seal butterfly valve, used for transporting high-pressure gases. Features: 1. Extremely simple and lightweight structure: It consists only of the valve body, valve stem, butterfly disc, and sealing components; the number of parts is 30% less compared to gate valves of the same diameter, and its weight is only 1/5 that of gate valves, making it easy to install and transport. 2. Significant cost advantage for large diameters: The manufacturing cost is 30%-50% lower than that of gate valves for DN≥300mm, and it offers the best cost-performance ratio at DN≥600mm, making it widely used in municipal water supply and drainage projects. 3. Efficient and labor-saving operation: A 90° rotation is sufficient to achieve full opening or closing; the manual operation torque is only 1/5 that of gate valves with the same diameter. When paired with pneumatic/electric actuators, it enables frequent operations. 4. Minimal installation space requirement: The valve body is short in length, measuring only 1/3 of the nominal diameter, making it suitable for pipe layouts with limited space (such as basements and areas with dense equipment). 5. Scenario-specific sealing adaptations: Rubber valve seats are suitable for low-pressure (≤1.6 MPa) conditions at normal temperatures (-20°C to 80°C); metal seals can withstand high temperatures and pressures, provided that their leakage rate meets the ANSI Class IV standard. 6. Special flow regulation characteristics: It has a nearly quick-opening type of flow curve. Within the 30%-70% opening range, the flow rate changes drastically. It is suitable only for rough regulation, not for scenarios requiring precise flow control. 7. The medium compatibility has limitations: it is suitable for clean or low-viscosity media such as water, air, and low-pressure gases; media containing particles can get trapped in the gap between the butterfly disc and the valve seat, causing scratches on the sealing surface. 8. High pressure differences can lead to erosion: When the pressure difference exceeds 2.5 MPa, bubble collapse can occur downstream of the butterfly valve, which may result in a reduction in the thickness of the valve body; therefore, an anti-erosion coating or a pressure-reducing mechanism is necessary. 9. Highly focused application scenarios: It is primarily used in water treatment, ventilation and air conditioning, as well as low-pressure gas pipelines. Typical applications include the inlet and outlet pipes of sedimentation tanks in water treatment plants, and air valves in central air conditioning systems. 10. Outstanding maintainability: The modular design allows for online maintenance; replacing the rubber valve seat only requires removing the stem gland, reducing maintenance time by over 50% compared to gate valves. 1. Valve body material: For municipal water supply and drainage systems, gray cast iron (HT200) is the preferred choice, as it is cost-effective and resistant to corrosion by neutral water ； For chemical processing conditions, ductile iron (QT450-10) or carbon steel (WCB) should be selected, as they offer higher strength ； For highly corrosive media (such as acids and bases), 304/316 stainless steel should be used. 2. Butterfly valve material: For normal operating conditions, carbon steel coated with epoxy resin is used, offering wear resistance and corrosion protection ； For media containing particles, wear-resistant cast iron (Ni-Hard) or cemented carbide (Stellite) is used ； The food and pharmaceutical industries opt for 316L stainless steel, which meets hygienic standards. 3. Valve seat material: For normal temperature and low pressure, nitrile rubber (NBR) is recommended; it is oil- and water-resistant ； For high-temperature operating conditions (≤150°C), EPDM is selected due to its strong weather resistance ； For highly corrosive chemical environments, fluororubber (FKM) is used, as it can withstand acids, alkalis, and salts ； For high-temperature and high-pressure metal sealing, stainless steel is used with cemented carbide surfacing. 4. Valve stem material: 2Cr13 stainless steel is selected for general applications, offering rust resistance and wear resistance ； For highly corrosive environments, use 316 stainless steel or Hastelloy C276 to prevent stem breakage caused by media erosion. 5. Material of sealing packing: Graphite packers are used at normal temperatures, flexible graphite for high-temperature applications, and PTFE packing for food-grade environments, ensuring no residues or contamination. 6. Lining material: For rubber- or PTFE-lined butterfly valves used in the transportation of corrosive media, the lining materials can be natural rubber (NR) or polytetrafluoroethylene (PTFE), which prevents direct contact between the media and the valve body. 7. Material of actuator connection components: The brackets for pneumatic/electric actuators are made of painted carbon steel to prevent rusting in outdoor environments ； Stainless steel fasteners are used to prevent jamming during disassembly. 8. Material combination for wear-resistant applications: For butterfly valves used in the transport of mine tailings, it is recommended to use a valve body made of QT450-10, with a stellite alloy welded onto the butterfly plate, and a nitrile rubber seat – this configuration increases the service life by more than 3 times. 9. Material combination for sanitary applications: In the food and beverage industry, the valve body and butterfly disc are made of 316L stainless steel, while the valve seat is made of silicone rubber (VMQ), meeting FDA certification requirements. 10. Material combination for high-temperature flue gas conditions: For boiler flue butterfly valves, the valve body is made of heat-resistant cast iron (RTCr2), the butterfly disc is made of heat-resistant steel (12Cr1MoV), and the valve seat is made of ceramic fiber, enabling tolerance to temperatures above 600°C. Gate valves use a gate as the opening/closing element; it moves up and down along the vertical axis of the valve seat to achieve sealing. When fully open, the flow passage remains completely unobstructed. Therefore, they are the ideal choice for shut-off applications where minimal fluid resistance is required. Its 10 core essentials are as follows: Classification of gate valves 1. By gate structure: parallel gate valves (single gate, double gate), wedge gate valves (single gate, double gate, elastic gate). 2. Classified by the movement of the valve stem: stem-type gate valves (the valve stem moves up and down with the gate), and non-stem type gate valves (the valve stem does not move up or down, only rotates). 3. Classified by sealing type: soft-sealed gate valves, hard-sealed gate valves. 4. Classified by actuation method: manual gate valve, electric gate valve, pneumatic gate valve, gear-driven gate valve. 5. Classified by pressure rating: low-pressure gate valves, medium-pressure gate valves, high-pressure gate valves, ultra-high-pressure gate valves. 1. Z41H-16C: Manual flange-type gate valve with exposed stem and wedge-shaped single gate; suitable for long-distance oil and natural gas pipelines.
2. Z945X-10Q: Electrically operated flange-type gate valve with non-exposed stem and elastic seat sealing; used in buried municipal water supply and drainage pipelines.
3. Z61Y-25I: Pneumatically operated welded gate valve with exposed stem and wedge-shaped single gate; applied to high-temperature and high-pressure steam pipelines in power plants.
4. Z342Y-40C: Worm gear-operated flange-type gate valve with exposed stem and wedge-shaped double gates; utilized for shutting off high-pressure chemical media.
5. Z45W-10R: Manual flange-type gate valve with non-exposed stem and wedge-shaped single gate; suitable for low-pressure applications involving corrosive media.

Features:
1. Extremely low fluid resistance: When fully open, the gate completely clears the flow path. The flow resistance coefficient Kv is nearly equivalent to that of the pipeline itself, resulting in significantly lower pressure loss compared to butterfly valves and globe valves. This makes it ideal for transporting media with high viscosity or at high flow rates. 2. Applicable only for fully open or fully closed positions: When regulating flow, the gate is susceptible to erosion by the medium, and the wear on the sealing surface accelerates. It must not be used for throttling control; otherwise, its service life will be reduced by more than 50%. 3. High structural stability: It features a linear lifting opening/closing mechanism with no rotational wear. The valve body is produced using casting or forging processes, making it suitable for all diameter ranges from DN15 to DN1200 mm. 4. Long opening and closing stroke: The gate plate must completely disengage from the flow channel to open fully; the handle needs to be rotated multiple times to operate it, and large-diameter models require a gearbox, making them unsuitable for emergency shutdown situations. 5. Moderate to high sealing performance: It provides reliable sealing under normal temperature and pressure conditions; however, in high-temperature and high-pressure environments (>400°C, >10 MPa), a bellows is required as an auxiliary sealing element to prevent deformation of the sealing surface and resulting leaks. 6. Wide medium compatibility: It can transport clean media such as water, steam, oil, and natural gas. Media containing particles will accelerate the wear of the gate, so filtration is required in advance. 7. No restrictions on installation direction: It is not affected by the flow direction of the medium and can be installed at any angle, making it suitable for pipeline systems with complex layouts (such as those in chemical plants). 8. Obvious advantages for large diameters: It offers stable performance under operating conditions where DN≥100mm; the range of DN150 to DN600mm is the optimal application range, and it is commonly used for shutting off long-distance pipelines. 9. Maintenance should focus on the sealing surfaces: It is necessary to regularly check the fit between the gate and the valve seat to prevent corrosion caused by residual media. It is recommended to clean and maintain the sealing surfaces every 6–12 months. 10. The typical application scenarios are well-defined: it is primarily used for main water supply and drainage pipes, steam pipelines in power plants, and long-distance oil and gas pipelines; it is a type of core valve that requires low flow resistance. 1. Valve body material: Carbon steel (WCB) is used for long-distance pipelines, as it can withstand high pressures and has good weldability ； For low-temperature conditions (≤-40°C), use low-temperature carbon steel (LCB) to prevent cold embrittlement ； For highly corrosive media, use 304/316 stainless steel or duplex stainless steel (2205). 2. Gate material: Carbon steel is selected for general operating conditions; the sealing surface is surfaced with hard alloy ； For media containing particles, use wear-resistant steel (NM400) ； Chromomolybdenum steel (WC6/WC9) is selected for high-temperature steam service to resist high-temperature oxidation. 3. Valve seat material: For soft-sealed gate valves, PTFE or reinforced nylon is recommended, as they offer excellent sealing performance ； For hard-sealed gate valves, stainless steel with Stellite surfacing is used; it can withstand high temperatures and pressures, with a sealing level up to ANSI Class VI. 4. Valve stem material: For straight-stem gate valves, 2Cr13 or 304 stainless steel is used to facilitate observation of the opening and closing status ； For dark stem gate valves, 316 stainless steel is used to prevent rust and sticking of the valve stem ； For high-pressure conditions, nitriding steel is selected to enhance surface hardness. 5. Packing box material: In high-pressure conditions, a bellows seal is used in place of traditional packing; the bellows are made of 316 stainless steel, which completely eliminates the problem of leakage at the valve stem. 6. Material of handwheel and transmission components: The handwheel of manual gate valves is made of ductile iron, offering light weight and durability ； The gears in the gear transmission mechanism are made of cast steel, with their tooth surfaces hardened to improve wear resistance. 7. Material combination for fire protection applications: The fire protection pipeline gate valve uses ductile iron for the valve body, carbon steel for the gate, and rubber for the seat, meeting the requirements of rapid opening and closing as well as reliable sealing in fire protection systems. 8. Material combination for steam service: High-temperature and high-pressure steam gate valves for power plants, with the valve body made of WC9 chromium-molybdenum steel, the gate plate made of 12Cr1MoV, and the valve seat clad with Stellite; capable of withstanding conditions of 540°C and pressures above 10 MPa. 9. Material combination for seawater service: For marine platform gate valves, the valve body is made of duplex stainless steel 2205, while the valve stem is made of Hastelloy to prevent corrosion caused by chloride ions in seawater. 10. Material combination for sewage service: Municipal sewage gate valves, with the valve body made of gray cast iron lined with rubber, and the gate plate made of stainless steel, to prevent blockage and corrosion caused by impurities in the sewage. A ball valve features a sphere with through-holes as its core; rotating it by 90° enables the opening and closing of the flow. It boasts excellent sealing properties, quick operation, and a wide range of applications, making it a versatile tool in both industrial and domestic settings. Classification of ball valves: 1. By structural type: floating ball valve, fixed ball valve, three-way ball valve, four-way ball valve, V-ball valve. 2. Classified by sealing type: soft-sealed ball valve, hard-sealed ball valve, fire and static electricity-proof ball valve. 3. Classified by actuation method: manual ball valve, electric ball valve, pneumatic ball valve, hydraulic ball valve. 4. Classified by bore diameter: reduced-bore ball valve, full-bore ball valve. 5. Classified by pressure rating: vacuum ball valves, low-pressure ball valves, medium-pressure ball valves, high-pressure ball valves, and ultra-high-pressure ball valves. Model 1. Q41F-16C: Manual flanged floating ball straight-through ball valve, for transporting chemical solvents and oils. 2. Q947F-25P: Electric flanged fixed ball straight-through ball valve, used in natural gas automation control systems. 3. Q647Y-40C: Pneumatic flanged fixed ball straight-through ball valve, for emergency shutoff of high-pressure steam and oil/gas. 4. Q44F-10Q: Manual flanged three-way L-type ball valve, used for reversing or splitting pipeline flow. 5. Q347H-64P: Worm gear flanged fixed ball straight-through ball valve, suitable for high-pressure corrosive media applications. Features: 1. Extremely fast opening and closing speed – only a 1/4 turn (90°) is required to fully open or close the valve; the operation time is 80% shorter than that of gate valves, making it the ideal choice for emergency shutdown systems (such as in fire protection and gas leak prevention). 2. Excellent sealing performance: Soft seals (made of PTFE or nylon) achieve near-zero leakage, while hard seals (made of metal) are suitable for high temperatures and pressures. Some models offer two-way sealing, making them suitable for use in vacuum systems. 3. Fluid resistance is nearly zero: The ball passage in the full-bore model has the same diameter as the pipe interior, allowing the fluid to flow without obstruction; thus, the pressure loss is close to zero, which helps reduce pumping energy consumption. 4. Robust and durable structure: It has few moving parts, and its ball, valve seat, and valve stem are made from high-quality materials such as stainless steel and special alloys, which give it corrosion and wear resistance; its service life is 2-3 times longer than that of ordinary butterfly valves. 5. It has a very wide range of applicable operating conditions: it can operate at temperatures ranging from -200°C to 425°C, and the pressure can reach levels suitable for API 600LB high-pressure applications; it is capable of handling various media such as gases, liquids, and sludges containing particles. 6. Easy and labor-saving to operate: It features low rotational torque, so no additional force is needed for manual operation; combined with an actuator, it enables remote automated control, making it suitable for high-frequency operation scenarios such as filling production lines. 7. Lower maintenance costs: The top-mounted design allows the valve seat seal to be replaced without removing the valve body, and some ball valves can be maintained online; daily, only the cleanliness of the sealing surfaces needs to be checked. 8. There are specific preferences regarding pipe diameters: small diameters (DN≤50mm) offer excellent cost-performance, and are commonly used in instrument pipelines and household water supply valves ； Large-diameter (DN＞200mm) pipes have high manufacturing costs and are used only in high-demand industrial applications. 9. Adjustable function with scalability: The V-type port ball valve boasts excellent flow regulation capabilities, and its control precision is close to that of a globe valve; it can be used in applications where both on/off control and throttling are required. 10. Comprehensive coverage of key applications: ranging from urban gas distribution and petrochemical wellhead equipment to the transportation of corrosive substances in the pharmaceutical industry and automated control systems, these are all its main areas of application. 1. Valve body material: Brass (HPb59-1) is used for domestic gas ball valves, offering safety and explosion protection ； Ductile iron is chosen for industrial low-pressure applications ； Carbon steel (WCB) is selected for medium and high pressure conditions ； For highly corrosive conditions, 316L stainless steel or titanium alloy (Ti) is selected. 2. Ball material: For soft-sealed ball valves, 304/316 stainless steel is used, with a polished surface ； Hard-sealed ball valves use stainless steel with cemented carbide cladding ； For media containing particles, tungsten carbide-coated spheres are used, increasing wear resistance by 5 times. 3. Seat material: PTFE is chosen for normal temperature and low pressure conditions, as it has a low friction coefficient and provides reliable sealing ； For high-temperature operating conditions (≤200°C), filled PTFE (PTFE + glass fiber) is selected ； For ultra-high temperature conditions (≤500°C), a metal hard seal (stainless steel with Stellite surfacing) is selected. 4. Valve stem material: 304 stainless steel for general applications ； For highly corrosive conditions, Hastelloy or Monel alloy (Monel 400) should be used ； Stainless steel treated with nitriding is selected for high-pressure conditions to prevent valve stem deformation. 5. Anti-static material design: For flammable and explosive media such as gas and gasoline, ball valves are used, and anti-static springs must be installed; phosphor bronze is chosen as the material to conduct static electricity away from the ball, thereby preventing explosions caused by static sparks. 6. Fire-resistant material structure: Ball valves used in the petrochemical industry must comply with the API 607 fire resistance standards. Graphite is used as the backup sealing material for the valve seat, while high-temperature resistant alloys are used for the bolts that connect the valve body to the valve cover, ensuring sealing in case of a fire. 7. Material combination for food and pharmaceutical applications: sanitary-grade ball valves, with the valve body, ball, and stem all made of 316L stainless steel; the inner and outer surfaces are mirror-polished. The valve seat is made of silicone rubber or fluororubber, meeting GMP certification requirements. 8. Material combination for high-pressure hydrogenation applications: For ball valves in refining and hydrogenation units, the valve body is made of 2205 duplex stainless steel, the ball is made of Hastelloy C276, and a metal hard-seal is used for the valve seat, enabling resistance to high-pressure hydrogen embrittlement. 9. Material combination for low-temperature LNG applications: For liquefied natural gas ball valves, the valve body is made of low-temperature stainless steel (304L); the ball is also made of the same material. The valve seat is made of low-temperature modified PTFE, enabling it to withstand temperatures as low as -196°C. 10. Material combination for wear-resistant slurry applications: Ball valves for use in mining and metallurgy industries, with a valve body made of wear-resistant cast iron, a ball coated with tungsten carbide, and a valve seat made of polyurethane – suitable for media with high wear levels and high solid content. Key selection recommendations: 1. For applications with large diameters (DN≥300mm), low pressure, and limited space, butterfly valves should be given priority ； 2. For high-viscosity media, high-flow rate cutoff, and applications requiring minimal resistance, gate valves are the preferred choice ； 3. For applications requiring emergency shutdown, high sealing performance, automated control, and compatibility with multiple media, ball valves should be given priority ； 4. When selecting a product, it is necessary to confirm the medium temperature, pressure, and particle content simultaneously, in order to choose the appropriate sealing material and structure type. Core principle 1: Medium priority principle: For corrosive media, stainless steel and alloy materials should be preferred ； For media containing particles, wear-resistant coatings or wear-resistant alloys are preferred ； For food and pharmaceutical applications, sanitary-grade stainless steel is the preferred choice. 2. Operating condition adaptation principle: Chromomolybdenum steel and metal hard sealing for high temperature and high pressure conditions ； Low-temperature cryogenic applications require low-temperature steel and modified sealing materials ； For flammable and explosive materials, use anti-static and fire-resistant structural materials. 3. Cost balance principle: Cast iron and carbon steel are chosen under normal operating conditions to reduce costs ； Alloy materials can be upgraded as needed for special operating conditions, to avoid waste resulting from over-specification. Although the three types of valves have their own focuses, they are all core components of fluid control systems. Understanding its core features and applicable limits can effectively improve system operational efficiency and reduce maintenance costs. If you need further information on material selection, troubleshooting, or specific application solutions for a certain type of valve, feel free to reach out to discuss your requirements in detail.