Axial flow check valve is a high-performance check valve designed according to API 6D and ASME B16.34. It is widely used in pipeline system to prevent liquid backflow hazards and protect mechanical equipment. It not only has the functional characteristics of general check valve, but also has the advantages of reducing water hammer hazards, reducing noise, reducing pressure drop and rapid response.
Axial flow check valve was developed in 1930. Its development is inspired by the ideal design requirements: a check valve can meet different application conditions with maximum reliability and minimum maintenance and operation cost. After years of application, the axial flow check valve has proved its reliability and ability to meet a variety of working conditions, and has been used in many strict occasions. The inner cavity surface of the valve body, flow guiding cover, valve disc and other overflow surfaces of the axial flow check valve shall have streamline shape, with round front and sharp back. The fluid is mainly laminar flow on its surface, with no or little turbulence. In addition to the function of general check valve, the axial flow check valve is also designed with damping spring. The combined valve seat sealing structure with hard seal and soft seal has silencing and damping effect, which is convenient for on-site maintenance. The unique axial flow shuttle structure has the advantages of small flow resistance, large flow coefficient and small overall size, It is the preferred valve for oil and gas gathering and transportation pipe network system at home and abroad, especially at the outlet of oil pump. It is suitable for oil, gas, water slurry and sour corrosive medium containing H2S + CO2, etc. to control the countercurrent of medium. The axial flow check valve adopts the axial flow shuttle structure in structure, and the valve disc is equipped with a buffer spring. When the medium flows downstream, the valve disc opens, and the medium flows through the axial flow channel of the valve body. When the medium pushes the valve disc open, the spring plays a buffer effect, avoiding the impact and vibration between the valve disc and the valve body when the ordinary check valve is opened. When the medium flows in reverse, the valve disc closes quickly, and the valve disc fits closely with the valve seat to prevent the medium from flowing in reverse. The combined hard seal and soft seal seat structure can effectively reduce the impact noise when the valve disc fits with the valve seat. This kind of check valve is an ideal product for fluid gathering and transmission pipe network to prevent medium countercurrent and eliminate noise and vibration.
Type of axial flow check valve
Axial flow check valve can be divided into sleeve shape, disc shape, ring disc shape and other forms according to its disc structure.
Structural characteristics of axial flow check valve
1. A damping spring is designed to avoid vibration and noise caused by the direct impact between the valve disc and the valve body when the ordinary check valve is opened.
2. The valve seat adopts the combined sealing structure of hard sealing and soft sealing, which has the effect of silencing and shock absorption, and is convenient for users’ on-site maintenance.
3. Compact structure, beautiful appearance and small overall size.
4. Unique axial shuttle structure, small flow resistance and large flow coefficient.
Working principle of axial flow check valve
The opening and closing of the valve disc is determined by the pressure difference between the inlet and outlet of the valve. When the pressure at the inlet end is greater than the sum of the pressure at the outlet end and the spring force, the valve disc opens. As long as there is a differential pressure, the valve disc is always open, but the opening degree is determined by the differential pressure. When the sum of the pressure at the outlet end and the spring force is greater than the pressure at the inlet end, the valve disc is closed and always closed. Since the opening and closing of the valve disc is in a dynamic force balance system, the valve operates stably without noise and the phenomenon of water hammer is greatly reduced. If the fluid flow rate and pressure cannot support the valve at a large opening and maintain a stable opening position, the valve disc and related moving parts may be in a state of continuous vibration. In order to avoid premature wear, noise or vibration of moving parts, the diameter of check valve should be selected according to the fluid state. The weight of the disc of the axial flow check valve is light, which can reduce the friction on the guide surface and return to the seat quickly. The valve disc with small mass and low inertia passes through a short stroke and contacts the valve seat surface with minimal impact force. This can reduce the damage to the sealing surface of the valve seat and prevent the leakage of the valve seat. The axial flow check valve closes quickly without impact. The valve disc with small mass and low inertia contacts the valve seat surface with minimal impact force after a short stroke, which can keep the sealing surface of the valve seat in good condition and avoid damage. More importantly, it can minimize the formation of pressure fluctuation and ensure the safety of the system.