Common Types and Functions of Check Valves
Add time：2019/3/29 16:58:45 Page views：8538
Check valves are classified by structure into three types: lift check valves, swing check valves and butterfly check valves. Lift check valves include vertical‑lift check valves and horizontal‑lift check valves. Swing check valves are divided into single‑disc swing check valves, double‑disc swing check valves and multi‑disc swing check valves. Butterfly check valves are straight‑through check valves. The above‑mentioned check valves can be further categorized by connection end type into threaded check valves, flanged check valves and welded check valves.
Rated Pressure: PN1.0‑16.0 MPa, ANSI CLASS 150‑900, JIS 10‑20K
Nominal Diameter: DN15~900, NPS 1/4~36
Connection Types: Flanged, butt‑welded, threaded, socket‑welded
Applicable Temperature: ‑196 °C ~ 540 °C
Body Materials: WCB, ZG1Cr18Ni9Ti, ZG1Cr18Ni12Mo2Ti, CF8 (304), CF3 (304L), CF8M (316), CF3M (316L), Ti.
With different material selections, check valves are suitable for media including water, steam, oil, nitric acid, acetic acid, oxidizing media, urea and other fluids.
1. Application of Wafer‑Type Check Valves
Installed in piping systems, check valves are automatic valves whose primary function is to prevent medium backflow. They open and close by means of medium pressure.
Wafer‑type check valves are applicable for nominal pressure PN1.0 MPa~42.0 MPa, Class 150~2500; nominal diameter DN15~1200 mm, NPS 1/2~48; operating temperature ‑196 °C ~ 540 °C. They are used in various pipelines to prevent medium reverse flow. By adopting different materials, they can handle diverse media such as water, steam, oil, nitric acid, acetic acid, strong oxidizing media and urea.
2. Main Materials of Wafer‑Type Check Valves
Carbon steel, low‑temperature steel, duplex steel (F51 / F55), titanium alloy, aluminum bronze, Inconel, SS304, SS304L, SS316, SS316L, chrome‑molybdenum steel, Monel (400/500), Alloy 20, Hastelloy and other metallic materials.
3. Standards and Specifications for Wafer‑Type Check Valves
Design and Manufacturing: API 594, API 6D, JB/T 8937, JB/T 3595
Face‑to‑Face Dimensions: API 594, API 6D, DIN 3202, JB/T 8937, ANSI/ASME B16.10
Pressure‑Temperature Ratings: ANSI B16.34, DIN 2401, GB/T 9124, HG 20604, HG 20625, SH 3406, JB/T 74
Test and Inspection: API 598, JB/T 9092, GB/T 13927
Pipe Flanges: JB/T 74~90, GB/T 9112‑9124, HG 20592~20635, SH 3406, ANSI/ASME B16.5, DIN 2543‑2548, GB/T 13402, API 605, ASME B16.47
4. Structural Features of Wafer‑Type Check Valves
Short face‑to‑face dimension, only 1/4 ~ 1/8 of that of conventional flanged check valves.
Compact size and light weight; its weight is merely 1/4 ~ 1/20 of conventional flanged check valves.
Quick disc closure with low water‑hammer pressure.
Suitable for both horizontal and vertical pipeline installation, easy mounting.
Unobstructed flow passage with low fluid resistance.
Sensitive action and reliable sealing performance.
Short disc stroke, low closing impact force.
Simple, compact integral structure with neat appearance.
Long service life and reliable performance.
In pump water‑supply systems, check valves protect pump impellers from damage caused by high‑pressure water backflow. When pump pressure suddenly drops for any reason, high‑pressure water at the pump outlet tends to flow backward toward the pump. A check valve fitted at the pump outlet closes instantly to prevent such reverse flow.
In hot‑water systems, check valves prevent hot‑water backflow into pipelines. In particular for solar water‑heater systems, back‑flowing hot water may damage PVC pipelines and even cause personal injury.
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