Process flow pipeline issues
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I would like to ask the experts: In the diagram shown, there is already a pneumatic diaphragm cut-off valve equipped with a solenoid valve on the material pipeline. Then why is another bypass circuit provided along with another cut-off valve? What is the purpose of such a design?
When repairing the valve above, operations can continue using the valve below, as a precaution
Then why not design the pipeline above as a bypass control similar to the one below? Why is it necessary to add an additional shut-off valve?
I can only tell that it’s meant to be a backup pipeline; I’m not sure why it was designed this way for now. I’ll ask the designers: lol
My personal guess is that function 1: at the beginning of operation, fine adjustments are made using the control valves on the bypass. Function 2: For such material main line shut-off valves, it is necessary to regularly check their opening and closing degrees. The function of the bypass is to ensure production continues when the main shut-off valve is switched off, allowing materials to flow through the bypass. By combining these two functions, it was decided to design a set of bypass control valves; this was probably also due to economic considerations. If control valves were used for the main pipeline, the cost would be high, it would require more space, and it would be difficult to design such a system.
When the main pipeline valve fails and cannot be used, continuous material transfer can be achieved through the bypass valve.
Let me talk about it. (1) This bypass shut-off valve is not intended for creating a bypass during maintenance, because if a bypass were needed for maintenance, one manual valve would be sufficient ； (2) This type of bypass shut-off valve is also common; the diameter of the main pipe is large, and when the main valve is closed, a large pressure difference exists before and after the valve, making it difficult to open the main valve. In such cases, the bypass shut-off valve opens first, reducing the pressure difference before and after the main valve, thereby facilitating its opening. Then the bypass shut-off valve closes.
After hearing what you said, I checked the diameter of the pipeline; indeed, DN300 is larger than those of other pipelines. The smaller pipelines don’t have this design – only the DN300 pipelines feature it
The functions of the three valves from top to bottom are as follows: the first one is a safety valve; under normal operating conditions, material flows through it, while its role is to automatically cut off the flow of material in case of an accident. The second remote control valve: during operation, the self-protection function is not activated; the fluid flow takes this path, and the valve is operated from the control room. Thirdly, the bypass valve: during the preparation phase for operation, water transport and steam purging are carried out through this route, to prevent impurities in the medium from damaging the control valves.
What was said on the eighth floor is correct; my explanation of the second valve was flawed – the self-protection valve can be put into use during the startup phase.