First, the working principle of the welding check valve:
The check valve is a valve that automatically prevents the fluid from flowing backwards. The valve flap of the check valve opens under fluid pressure, and the fluid flows from the inlet side to the outlet side. When the inlet side pressure is lower than the outlet side, the valve flap automatically closes under the influence of fluid pressure difference, its own gravity and the like to prevent the fluid from flowing backward.
Second, the welding check valve structure features:
Welding check valves are generally divided into several types, such as lift type and swing type.
The structure of the lift check valve is generally similar to that of the stop valve. The valve flap moves up and down along the center line of the passage, and the action is reliable, but the fluid resistance is large, which is suitable for occasions with a small diameter. Lift check valves are available in both straight and vertical versions. Straight-flow lift check valves are generally only installed in horizontal lines, while vertical lift check valves should normally be installed in vertical lines.
The valve flap of the swing check valve rotates around the rotating shaft. Its fluid resistance is generally smaller than that of the lift check valve, which is suitable for larger diameter applications. According to the number of flaps, the swing check valves can be divided into three types: single flap swing type, double flap swing type and multi-lobed swing type. Single-lobed swing check valves are generally suitable for medium caliber applications. When a single-valve rotary check valve is used for the large-diameter pipe, in order to reduce the water hammer pressure, it is preferable to use a slow-closing check valve that can reduce the water hammer pressure. The double-valve swing check valve is suitable for large and medium diameter pipes. The double-grip swing check valve has a small structure and light weight, and is a fast-developing check valve; the multi-lobed swing check valve is suitable for large-diameter pipe roads.
Third, the main parts of the welding check valve materials and performance specifications:
Main parts | Valve body, bonnet, rocker | WCB | CF8 | CF8M | WC6, WC9 |
Valve flap | WCB stack Cr13 or cemented carbide | CF8 stack cemented carbide | CF8M stack cemented carbide | WC6, WC9 stack cemented carbide | |
Seat | 25 piles of Cr13 or hard alloy | 304 pile cemented carbide | 316 stack of cemented carbide | 20Cr1MoV stack cemented carbide | |
Gasket | Soft iron, XB450 | PTFE | PTFE | Stainless steel + acid resistant asbestos winding mat | |
bolt | 35CrMoA | 35CrMoA | 35CrMoA | 25Cr1Mo1V | |
Nut | 45 | 45 | 45 | 35CrMoA | |
The main parameters | Applicable medium | Oil, water, steam | Nitric acid | Acetic acid | Oil, water, steam |
proper temperature °C | ≤425 | ≤200 | ≤200 | ≤550 |
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