Shut-off valve

The globe valve is designed as a forced sealing valve, meaning that when the valve is closed, pressure is applied to the disk to ensure a tight seal. Closing the valve requires a greater force compared to opening it, as it must overcome the friction force between the valve stem and packing, as well as the thrust generated by the medium's pressure. To prevent failure, it is essential to have a large diameter valve stem capable of handling the closing force.

In recent years, self-sealing valves have emerged, causing a change in the flow direction of shut-off valves. The flow now enters the valve cavity from above the valve clack. This design reduces the force required to close the valve and increases the force needed to open it, allowing for a smaller valve stem diameter. Additionally, this type of valve provides a tighter seal under the influence of the medium.

In the past, China's valve industry, represented by "Sanhua," mandated that the flow direction of stop valves should be from top to bottom. It was also recommended to install the valve horizontally.

The maximum flow is achieved when the shut-off valve is opened and the disc height reaches 25% to 30% of the nominal diameter. This is a clear indication that the valve is fully open. Thus, the extent to which the valve disc has been opened should be taken as the determining factor of the fully open position of the stop valve. It is recommended to ascertain the stroke of the valve disc in order to establish the fully open position, thereby ensuring optimum efficiency.