| 01 | Wafer Butterfly Check Valve | Two spring-loaded plates close rapidly when reverse flow begins. | Cast iron, ductile iron, carbon steel, stainless steel | Wafer, lug, flanged | API 594 ASME B16.34 API 598 | DN50–DN1200; NPS 2–48 | Usually PN10–PN40; Class 150–300 | Water, cooling water, air, low-to-medium viscosity liquids | Water treatment, HVAC, power stations, general process piping | Disc balance, spring fatigue resistance, low cracking pressure, and face-to-face dimensions are critical. |
| 02 | Swing Check Valve | A hinged disc swings away from the seat under forward flow and returns by gravity or reverse flow. | Carbon steel, stainless steel, alloy steel, ductile iron | Flanged, butt-weld, wafer | API 6D API 594 API 598 GB/T 12236 | DN50–DN2000; NPS 2–80 | PN10–PN420; Class 150–2500 | Oil, gas, water, steam, and non-corrosive process fluids | Pipeline transport, refineries, chemical plants, municipal infrastructure | Hinge design, disc travel, seat wear, pressure drop, and water-hammer control require careful engineering. |
| 03 | Lift Check Valve | A guided piston or disc moves vertically away from the seat during forward flow. | Forged steel, cast steel, stainless steel, alloy steel | Flanged, threaded, socket-weld, butt-weld | ASME B16.34 API 598 BS 1868 | DN15–DN600; NPS ½–24 | PN16–PN420; Class 150–2500 | Steam, gas, oil, condensate, and clean process fluids | Boilers, thermal power, petrochemical and chemical process lines | Accurate guide clearance, vertical installation orientation, seat alignment, and resistance to high-temperature deformation are important. |
| 04 | Piston Check Valve | A piston moves axially inside a guided chamber and closes against a seat when flow reverses. | Carbon steel, stainless steel, chrome-molybdenum alloy steel | Flanged, threaded, socket-weld | ASME B16.34 API 598 BS 1868 | DN15–DN500; NPS ½–20 | PN16–PN420; Class 150–2500 | Steam, hydrocarbons, gases, and high-pressure liquids | Refining, chemical processing, steam systems, and high-pressure piping | Piston-to-guide clearance, damping behavior, seat hardness, and resistance to internal scoring affect service life. |
| 05 | Ball Check Valve | A free-moving or spring-assisted ball seals the flow passage during reverse flow. | Ductile iron, carbon steel, stainless steel, plastic-lined metal | Threaded, flanged, socket-weld, union | EN 12334 API 598 ASME B16.34 | DN15–DN600; NPS ½–24 | PN6–PN250; Class 125–1500 | Water, wastewater, slurries, viscous fluids, and mild chemicals | Pumping stations, sewage systems, mining, slurry handling, and process plants | Ball density, coating compatibility, chamber geometry, anti-clogging performance, and solids handling are key factors. |
| 06 | Silent or Nozzle Check Valve | An axial disc closes against a spring before significant reverse flow develops. | Carbon steel, stainless steel, ductile iron, nickel-aluminum bronze | Flanged, wafer, lug | API 594 ASME B16.34 API 598 | DN25–DN1200; NPS 1–48 | PN10–PN100; Class 150–600 | Water, air, chilled water, condensate, and clean process liquids | Water supply, HVAC, desalination, pump discharge, and power utilities | Spring response, disc mass, flow-path optimization, noise reduction, and surge protection determine performance. |
| 07 | Dual-Plate Check Valve | Two semi-circular plates pivot toward the centerline and close with spring assistance. | Cast steel, stainless steel, ductile iron, duplex stainless steel | Wafer, lug, flanged | API 594 API 6D API 598 | DN50–DN1200; NPS 2–48 | PN10–PN420; Class 150–2500 | Oil, gas, water, air, and corrosive process fluids | Petrochemical pipelines, offshore facilities, water networks, and power plants | Plate synchronization, hinge strength, spring selection, sealing under low flow, and compact face-to-face length are essential. |
| 08 | Foot Valve | A spring-loaded or weighted check valve at the suction line prevents pump drainage and often includes a strainer. | Cast iron, ductile iron, bronze, stainless steel, engineering plastics | Flanged, threaded, socket-weld | EN 12334 API 598 Local project specifications | DN25–DN500; NPS 1–20 | PN6–PN25; Class 125–300 | Raw water, clean water, irrigation fluids, and light industrial liquids | Municipal water systems, agricultural irrigation, wells, and booster-pump installations | Strainer open area, suction loss, corrosion resistance, debris tolerance, and easy maintenance are major design points. |
| 09 | Diaphragm Check Valve | A flexible diaphragm opens under forward pressure and seals the passage during reverse flow. | PVC, PP, PVDF, PTFE-lined steel, stainless steel | Socket, threaded, flanged, sanitary clamp | EN 12334 ISO 16138 API 598 | DN15–DN300; NPS ½–12 | PN6–PN16; application-dependent | Corrosive chemicals, ultrapure water, acids, alkalis, and hygienic fluids | Electronics manufacturing, chemical dosing, water treatment, and pharmaceutical systems | Diaphragm material compatibility, permeation, fatigue life, cleanliness, and low-dead-volume design are critical. |
| 10 | Axial Flow Check Valve | A streamlined axial disc or piston moves along the pipeline centerline to minimize turbulence. | Carbon steel, stainless steel, duplex stainless steel, nickel alloys | Flanged, butt-weld, wafer | API 6D API 594 ASME B16.34 | DN50–DN1500; NPS 2–60 | PN16–PN420; Class 150–2500 | Natural gas, refined products, steam, water, and high-velocity process fluids | Long-distance pipelines, compressor stations, LNG facilities, and high-efficiency process systems | Flow coefficient, spring dynamics, erosion resistance, weld quality, and rapid closure performance require advanced testing. |