Stop valve

I can assure you that not all stop valves have the inlet at the bottom and the outlet at the top; there are also stop valves used in pipelines to prevent leaks that are installed in an inverted position. Such valves require specific technical requirements during installation.

It is still necessary to install it in the direction indicated on the valve, as many globe valves do not have liquid entering from the lower side and exiting from the higher side; rather, it is the opposite. This is likely related to the direction of the force exerted by pressure; in the case of a check valve that allows flow from high to low, when the valve is closed, the back pressure acts above the valve seat, and such a valve is less prone to leakage. It’s probably based on this principle; I can’t remember exactly.

When installing a stop valve, the medium can enter either from below the valve core or from above. The advantage of allowing the medium to enter from below the valve core is that the packing is not under pressure when the valve is closed, which extends its service life; moreover, it is possible to replace the packing even when there is pressure in the pipeline ahead of the valve. The disadvantage of the medium entering from below the valve core is that the driving torque of the valve is higher, at about 1.05~1.08 times that of entry from above; the axial force on the valve stem is large, causing the stem to bend easily. For this reason, the method of allowing the medium to enter from below is generally only suitable for small-diameter globe valves (DN50 and below); for globe valves with a diameter of DN200 or more, the method of allowing the medium to flow in from above is used. Electric globe valves generally allow the medium to enter from above. The disadvantages of the medium entering from above are exactly the opposite of those of it entering from below

1. Globe valves are only suitable for full open and full closed positions; they cannot be used for regulation or throttling. 2. The installation direction of the valve should first be strictly in accordance with the indications on the valve itself. 3. For small-diameter valves, the standard design is one with fluid entering from below and exiting from above; however, most large-diameter globe valves are designed with fluid entering from above and exiting from below. Since the valve disc has a large area while the valve stem is thin, it is not possible to achieve sealing by applying pressure to the valve disc through the valve stem alone. Therefore, the upper-inlet/lower-outlet design is used, so that the pressure of the flowing fluid helps to apply pressure to the valve disc when the valve is closed, thereby achieving sealing (similar to the function of a check valve). The valve stem packing uses a self-sealing mechanism, eliminating the need to worry about fluid leakage. 4. Sometimes, small-diameter valves can also be installed in reverse; the reason is that when there is a leak in the packing, it’s not possible to replace the packing simply by stopping the pump, as there is pressure in the system. By installing the valve in reverse, it can be closed, the pump can be stopped, and then the packing can be repaired.

Can a DN200 stop valve be used if it is installed in the wrong direction? What will be the consequences?