The function of the bypass setting
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What is the purpose of installing bypasses for pneumatic valves and flow meters, and why is a ball valve installed on the bypass? If it is only for maintenance purposes, the ball valves on both sides of the pneumatic valve can be closed to block the flow of material, allowing for maintenance to be carried out. If the pneumatic valve fails and the bypass is activated, and the bypass cannot regulate the flow rate, it will result in inaccurate reflux in the distillation column, affecting the quality of the product
Regarding the function of the bypass, I remember that the regulations provide a detailed description of it. As far as I recall, there are two main purposes: 1. When it is necessary to service the pneumatic valve flow meter, the bypass can be used to allow flow to continue for a short period of time, thus avoiding the need to shut down production. Although flow regulation isn’t possible in this case, it’s still better than shutting down the entire system entirely. 2. During driving, in the initial stage the flow rate of the fluid within the piping system is insufficient; using large-diameter pipes directly can cause stress on the control valves. In such cases, it is necessary to route the fluid through a bypass first, and only after a sufficient flow rate is achieved should it be directed back to the main pipeline.
However, the inability to adjust the flow rate can cause imbalance in the distillation tower, affecting product quality; it is better to close the valves on both sides of the flow meter and send all the output product back as reflux
The situation varies; product characteristics and manufacturing processes differ, which leads to different outcomes that need to be considered in a balanced manner. If real-time adjustment based on parameters is required, then a bypass isn’t necessary. However, design institutes lack knowledge of these manufacturing processes, so they are unable to design flow meter valve assemblies effectively.
When designing, the design institute will not follow your procedures (because they don’t know how to carry them out); instead, they will adhere to the relevant regulations in their work. If you think a bypass is unnecessary, you can omit it, but what will you do when it becomes necessary?
It is necessary to service the flow meter and control valve without shutting down the plant; a bypass line can only be used temporarily
Bypass design refers to carrying out maintenance tasks without shutting down production. “If the ball valve is closed to shut off the material flow, then maintenance can be carried out – but doesn’t that mean the plant has to be stopped? Why can’t ball valves be adjusted? It’s just that they don’t have the convenience of automatic valves
This post was last edited by Suspected Good Citizen on 2023-2-14 at 10:51. Certain processes have special requirements; what is discussed here refers to bypass systems, and it is not limited to bypasses in distillation towers.
There should be two functions: first, to transport materials during maintenance work, and second, to be used during purging.