Regarding the installation direction of the stop valve
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Everyone: There is now a stop valve used for filling the system with nitrogen for displacement – in which direction should it be installed? After the system is in operation, the pressure inside it is higher than atmospheric pressure. I would like to ask, is it better to start from the outside world and move towards the system, or from the system and move towards the outside world? What is the reason?
Follow the direction that requires sealing under normal operating conditions
The system works well with the outside environment, allowing for a tighter sealing of the cover
Thank you for your responses. Is there any theoretical basis to support this?
Stop valves have a specific direction of operation; the arrow should point in the same direction as the desired flow. As per your requirement, fluid flows from the outside into the system, and high internal pressure prevents backflow.
For this type of small shut-off valve, the direction of the arrow indicates the pressure-bearing direction; it is correct that the system is connected to the outside world
Stop valves are generally installed in the direction indicated by the arrow (to stop the flow within the pipeline), with the system leading to the outside
The key issue is that you haven’t determined the location yet; the function of a valve is to stop the flow of fluid and regulate its volume. Typically, the pressure of the gas used for displacement is lower than the operating pressure of the equipment. Moreover, once the replacement is complete, many requirements call for the installation of blind plates. Therefore, the end of the pipeline connected to the production unit equipment should be used as the output end (for globe valves); this is commonly referred to as installing the valve in reverse. The arrow points toward the displaced gas side. The weak sealing point of a globe valve is at the connection between the valve stem and the valve body, which is a dynamic sealing point. This point should be set in the direction toward the outlet side. These can be understood based on the structural design principles of valves.
The valve body is marked with the direction; generally, fluid enters from the lower side and exits from the higher side
1. The valve body of a stop valve indicates the flow direction, and it is generally installed in accordance with this direction； 2. This route is designed for systematic nitrogen displacement; therefore, check valves should be installed at both the beginning and end, or two gate valves should be used with an eight-shaped blind plate installed in between. So there is no need to consider the system and nitrogen pressure. 3. Under normal circumstances, it also depends on the design requirements. I hope it can help you.