Is there something wrong with this stop valve, which has flow from high to low?

Those with a large diameter or high pressure also have high inlet and low outlet pressures

PN16? It looks like a low-pressure liquid medium?

There seem to be no clear standard specifications in domestic and international standards regarding whether a globe valve should use a low-inlet, high-outlet configuration or a high-inlet, low-outlet configuration; generally, for sizes up to DN100, the low-inlet, high-outlet configuration is used, while sizes above DN125, including DN125 itself, are designed with a high-inlet, low-outlet configuration. Large-diameter or high-pressure globe valves are designed with the inlet at the top and the outlet at the bottom because the valve disc is too large while the valve stem is thin; relying solely on the valve stem to exert pressure is not sufficient, which can lead to internal leakage. Check valves that allow flow in one direction only are usually designed with two 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, taking into account the stiffness of the valve, a medium flow direction with high inlet and low outlet is adopted; when the valve is closed, self-sealing is achieved in both the upper and lower directions. Moreover, the higher the pressure, the better the sealing effect.

When the nominal diameter of the stop valve is less than 200 and the pressure is less than 25 MPa, a low-inhigh-out configuration is usually adopted. When the nominal diameter is greater than 200 and the pressure is greater than 4 MPa, a high-inlet low-outlet configuration is used. The disadvantage of medium entering from below the valve core is that the driving torque required to operate the valve is higher, at about 1.08–1.08 times that when the medium enters from above. The axial force acting on the valve stem is also greater, making it prone to bending. These disadvantages become particularly apparent as the nominal diameter and pressure increase, significantly affecting the proper functioning of the valve. Therefore, in applications with large diameters and high pressures, valves are often designed with the medium entering from above and exiting from below.

1. This depends on the medium pressure; there is no specific defined pressure limit. Generally, for low pressure, low inlet and high outlet are used, while for high pressure, high inlet and low outlet are used. 2. For those commonly over 8 kilograms, high in and low out is applicable; the design in the diagram shows PN16 with high in and low out

It depends on the size of the valve, as well as the medium

Yes. An arrow on the valve body pointing upward indicates that the pressure-bearing direction is upward; using a design with high inlet and low outlet is feasible

Judging from the background and the color of the pipes, isn’t this the circulating water in the power plant?