Installation direction of control valve

Have you confirmed that all the installed control valves have positive-displacement spools? Generally, when installing valves, the fluid flow is from low to high. However, if there are specific requirements in the process, the flow may also be from high to low. When time permits, it is necessary to consider the pressure difference before and after the control valve. You can take a look at the detailed specifications for the control valve; there is an item there that specifies whether the control valve should operate in flow-open or flow-close mode. By \"flowing in this direction,\" it means that the fluid flows in the same direction as the opening direction of the valve, that is, from low to high ； Conversely, in the case of flow in the opposite direction, the flow moves along the direction in which the valve is closed, that is, from high pressure to low pressure. These are just my humble opinions; as a newcomer, I hope to receive plenty of guidance.

To be honest, I haven’t paid attention to this issue over the years; thank you!

The flow direction and whether it should be open or closed are generally specified in the design; the manufacturer carries out calculations based on these requirements. During installation, attention must be paid to the flow direction to ensure it is not installed in the wrong way.

What kind of trashy manufacturer produces valves? Surely no one makes valves in this way; you might have misseen it. Take a close look – are there any differences between the valves with these two different flow directions? For example, in the case of a valve that allows fluid to flow from high to low, there is a protrusion at the bottom of the valve body

Thank you all. It seems we have no choice but to follow the manufacturer’s specifications; the manufacturer must have designed it accordingly

For single-seat valves, the unbalanced force is high; if they are installed in the wrong direction, the control valve is likely to not function properly. Cage-type control valves can be installed in reverse. One of our company’s cage-type control valves had a problem with low pressure difference; by installing it in reverse, with high inlet and low outlet instead of the original low inlet and high outlet configuration, the issue of low pressure difference was resolved, and the valve is now functioning properly. It should also be noted that when selecting control valves, process conditions and the properties of the medium have already been taken into account. Please use them as specified; do not change their operating conditions arbitrarily, as this may lead to adverse effects, impede normal operation, or even render them unusable.

For the oxygen medium I’ve come across, high inlet pressure and low outlet pressure are required.

Usually, the input is low and the output is high, but this is different due to the requirements for opening and closing the flow!

Globe valves are considered to be valves with forced sealing; therefore, when the valve is closed, pressure must be applied to the valve disc in order to ensure that the sealing surfaces do not leak. When the medium enters the valve from below the valve disc, the resistance that the operating force must overcome consists of the friction between the valve stem and the packing, as well as the thrust generated by the pressure of the medium. The force required to close the valve is greater than that needed to open it; therefore, the diameter of the valve stem must be large enough, otherwise the valve stem may bend, a condition known as \"low inlet, high outlet\". In recent years, since the emergence of self-sealing valves, the flow direction of the medium in globe valves has changed to enter the valve chamber from above the valve disc, that is, from high to low. At this time, under the action of medium pressure, the force required to close the valve is low, while the force required to open it is high; accordingly, the diameter of the valve stem can be reduced. At the same time, under the influence of the medium, this type of valve is also more airtight. There is no clear standard stipulating why stop valves should be designed with the inlet at the lower level and the outlet at the higher level in domestic or international standards; generally, for sizes up to DN100, the inlet is at the lower level and the outlet at the higher level. ! In the domestic and international valve industry, large-diameter valves are routinely designed with the inlet at a higher level and the outlet at a lower level. Secondly, it also does not specify that valves with a certain diameter or larger should be designed with high inlet and low outlet. (Basically, those of DN125 and above, including DN125, are designed with high inlet and low outlet.) In check valves with high inlet and low outlet pressure, they are usually designed with double valve discs (also known as balanced valve discs). There are two reasons for this design: one is to prevent excessive pressure differences from occurring when the valve is opened or closed. Secondly, the stiffness of the valve must be taken into account. A high inlet and low outlet configuration has a significant impact on the valve; typically, for large-diameter globe valves that are not designed with a balanced valve disc seal to handle this configuration, it becomes very difficult to hold the medium in place. Therefore, the installation direction of the valve should first be strictly followed according to the markings on the valve; if there are no markings, rely on experience or consult the manufacturer – do not install it randomly! ! !

Stop valves are available with flow from high to low as well as from low to high! The diaphragm control valve should work on a similar principle to a globe valve!