Valves in process design
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Please refer to the cut-off valves mentioned in items 3 and 4 in the diagram. Does this term refer to gate valves that are operated manually, or to pneumatic or electric cut-off valves controlled by an automated system? In our plant and workshop, when we talk about cut-off valves, we usually mean those of the pneumatic type that can be controlled from the central control system DSC. Most of the automated cut-off valves in our system are installed at the bottom of the reflux tank. As for the inlet and outlet isolation valves in our plant, they are both gate valves that require manual operation. If the cut-off valves mentioned in the diagram refer to the automated type, it might be too costly. Additionally, the check valve mentioned in item 4 probably refers to the drain valve located between two valves. Our raw material is liquefied gas, which is flammable and explosive
It is now common to use double isolation valves in designs; electric gate valves are often employed, while manual isolation valves are rarely used (as there are fewer operators available). Especially in locations where strict isolation is required, blind flanges or check valves are used to ensure isolation.
The dual-valve system can be understood in this way: the valve through which the material flows downstream is the operating valve, while the valve located upstream is a normally open valve. When there is a problem with the downstream valve, the upstream valve is closed to allow for the replacement of the downstream valve. Therefore, the upstream valve can also be considered a maintenance valve.
It is very necessary to install two valves for entering and leaving the boundary area, and an 8-shaped blind plate should be placed between the two valves; blind passing operations should be carried out according to the operating conditions.
It is very necessary to install two valves for entering and leaving the boundary area, and an 8-shaped blind plate should be placed between the two valves; blind passing operations should be carried out according to the operating conditions.
1. The valve can be pneumatic, electric, or manual – these are merely the methods used to drive the valve. What matters in terms of technical requirements is the ability to cut off flow; whether automatic control is needed should be determined based on actual conditions. 2. I think this dual-valve with check valve is used to determine whether there is any internal leakage by opening the check shut-off valve. 3. I’m very curious: if the shut-off valve for your liquefied gas fails, do you check by listening for the sound of pressure release? I originally thought there would be a smell, but then I realized that liquefied gas at home has an odor because odorous substances such as thiol are added to help detect leaks more easily.