The function of the flap valve
Thread Content
Due to the certain pressure drop in the cyclones, especially as the pressure drop increases with the use of a reduced-diameter structure at the secondary outlet, the pressure inside the secondary cyclone legs is lower than the pressure in the bed. The pressure difference between the top of the secondary cyclone legs and the dilute-phase pressure in the regenerator is approximately equal to the total pressure drop of the primary and secondary cyclones. The function of the flap valve is to prevent the catalyst from flowing back up through the feed leg due to this pressure difference. Under normal conditions, the flap of the flap valve and the valve seat are in a state of good sealing. When the amount of catalyst accumulated in the catalyst leg causes the static pressure within it to exceed the pressure drop of the cyclone, as well as the sum of the static pressure of the bed layer above the flap valve and the pressure required to open the flap valve, the flap valve opens automatically in a timely manner, allowing the catalyst in the catalyst leg to flow into the bed layer. If the static pressure inside the leg is lower than the sum of these three pressures, the flap valve closes automatically to prevent the catalyst from flowing back. The function of the flap valve is to maintain a certain height of material column in the leg. Its sealing function relies on the weight of the wing plate itself. The level height that can be maintained in the material leg is related to the pressure drop of the centrifuge and the angle between the vanes and the vertical line. Earlier, it was mostly at 3 degrees; now some refineries maintain it at 5–8.
The installation angle of each flap valve is different; static tests must be conducted on the flap valves before they leave the factory, and these tests determine the appropriate installation angle for them. During installation on site, the angle of the flap valve must remain the same as that determined during the factory tests.
Its main function is to ensure a certain height of catalyst column inside the leg, thereby preventing the catalyst from flowing back and being lost
The angle needs to be determined through experiments based on the catalyst weight specified during design, usually ranging from 3 to 7°. Extra care should be taken during installation: symmetric welding is required, and the angle must be measured multiple times using a frame level. The welding method should be determined based on these angle measurements, and once welding is complete, the angle should be measured again to ensure it is roughly consistent with the specified angle. And keep a record of it.
I completely agree with what was said above. Our factory replaced the cyclone separator not long ago, and the angle at which it was installed wasn’t exactly consistent with the designed angle, but it was still within acceptable limits, and the performance is fine! Design and construction can never be exactly the same
The installation angle of each flap valve is different; static tests must be conducted on the flap valves before they leave the factory, and these tests determine the appropriate installation angle for them. During installation on site, the angle of the flap valve must remain the same as that determined during the factory tests. Its main function is to ensure a certain height of catalyst column inside the leg, thereby preventing the catalyst from flowing back and being lost. The angle must be determined through testing based on the weight of the catalyst specified in the design; it is generally between 3–7°, though some angles can be larger. Extra care should be taken during installation: symmetric welding is required, and the angle must be measured multiple times using a frame level. The welding method should be determined based on these angle measurements, and once welding is complete, the angle should be measured again to ensure it is roughly consistent with the specified angle. Measure it every time during maintenance, keep records, and if the deviation is large, adjust or replace it.
Wing valves are commonly used in catalytic cyclone legs. Now, a weight valve can be used as a substitute for wing valves; its production and processing are simpler and more convenient than those of wing valves. Adjusting the amount of catalyst discharged requires only adjusting the position of the weight on the lever, which makes it very convenient for widespread use.
The angle of the flap valve is generally determined by design; if the angle is too small, the flap valve opens and closes frequently, which affects its lifespan； An excessive angle of the flap valve, along with a high catalyst level in the material leg, may affect the efficiency of the cyclone separator. Before leaving the factory, the flap valve must undergo static tests, which focus on the opening angle of the flap valve and are primarily used to check whether the pull ring is flexible. The installation angle of the flap valve should be the design angle minus the static test angle.
How can the flap angle be measured more accurately?
Study*study*. It would be better if it were more detailed
I’d like to ask a question here: the bucket outside the flap valve has many holes, resembling a mesh. What is the purpose of that? Please advise