Classification of check valves

I. Swing check valve: The disc of a swing check valve is disk-shaped and rotates around an axis located in the valve seat channel. Due to the streamlined shape of the flow path within the valve, its flow resistance is lower than that of lift check valves; it is suitable for large-diameter applications with low flow rates and little variation in flow conditions. However, it is not appropriate for use with pulsating flows, and its sealing performance is inferior to that of lift check valves. Swing check valves are available in three types: single-disc, double-disc, and semi-double-disc. These three types are primarily classified based on the valve diameter, with the aim of reducing hydraulic shock when the flow of the medium stops or reverses. II. Lift-type check valve: A check valve in which the valve disc slides along the vertical center line of the valve body. Lift-type check valves can only be installed in horizontal pipelines, and a sphere-shaped valve disc can be used in high-pressure, small-diameter check valves. The valve body of the lift-type check valve has the same shape as that of a globe valve (it can be used interchangeably with a globe valve), so its fluid resistance coefficient is relatively high. Its structure is similar to that of a globe valve, with the valve body and valve disc being identical to those in a globe valve. Guide sleeves are machined on the upper part of the valve disc and the lower part of the valve cover; the valve disc’s guide sleeve can move up and down freely within the valve seat’s guide sleeve. When the medium flows in the correct direction, the valve disc opens due to the thrust exerted by the medium. When the flow stops, the valve disc drops back down onto the valve seat, thereby preventing the medium from flowing in the reverse direction. In the direct-acting lift check valve, the direction of the medium inlet and outlet channels is perpendicular to the direction of the valve seat channel ； A vertical lift-type check valve, in which the directions of the medium inlet and outlet channels are the same as those of the valve seat channel, has lower flow resistance compared to a straight-through type. III. Disc check valve: A check valve in which the valve disc rotates around a pin inside the valve seat. The disc check valve has a simple structure, can only be installed in horizontal pipes, and has poor sealing performance. IV. Pipe-type check valve: A valve in which the valve disc slides along the center line of the valve body. The pipe-type check valve is a newly developed type of valve; it is small in size, light in weight, and easy to manufacture, making it one of the trends in the development of check valves. However, the fluid resistance coefficient is slightly higher than that of the swing check valve. V. Compression-type check valve: This type of valve is used as a valve for shutting off boiler feed water and steam; it combines the functions of a lift-type check valve with those of a globe valve or angle valve. In addition, there are also some check valves that are not suitable for installation at the pump outlet, such as foot valves, spring-type check valves, Y-type check valves, etc.

Does the steam check valve need to be custom-made?

If it is steam at room temperature not exceeding 250°C, use a steam-specific check valve.