The valve opening degree is related to the following factors:
Process requirements: In industrial production and other scenarios, different process flows have specific requirements for parameters such as fluid flow rate and pressure. For instance, in chemical reactions, to control the reaction rate and product quality, it is necessary to precisely adjust the flow rate of raw materials. This requires determining the opening degree of the valve based on specific reaction conditions and formulas to ensure that an appropriate amount of raw materials enter the reactor. In the heating system, the valve opening should be adjusted according to the heat load demand of the room to control the flow of hot water, so as to achieve an appropriate indoor temperature.
Characteristics of Pipeline system
Pipe resistance: The length, diameter, inner wall roughness of the pipe, as well as the quantity and type of pipe fittings such as elbows and tees on the pipe, all affect pipe resistance. When the resistance in the pipeline is relatively large, in order to ensure a certain flow rate, it is necessary to appropriately increase the valve opening. Conversely, when the pipeline resistance is relatively small, the valve opening degree can be relatively small. For instance, when there are long-distance transportation pipelines with a large number of pipe fittings, a larger valve opening is required to overcome resistance and ensure that the fluid can be smoothly transported to the destination.
System pressure: The pressure difference between the inlet and outlet of the system also affects the valve opening degree. If the pressure difference in the system is large, the valve opening can be smaller while meeting the flow requirements. When the pressure difference in the system is small, it may be necessary to increase the valve opening to boost the flow rate. For instance, in a fluid transfer system driven by a pump, the pressure provided by the pump is constant. If the pressure at the outlet end of the pipeline is relatively high, it is necessary to balance the pressure by adjusting the valve opening to ensure that the flow rate meets the requirements.
Characteristics of the valve itself
Valve type: Different types of valves have different flow characteristics. For instance, the flow characteristic of a gate valve is relatively close to linear, and the flow change is more obvious when the opening degree is large. Ball valves, on the other hand, have better shut-off performance and can achieve a wide range of flow control at a relatively small opening. Therefore, depending on the type of valve, the required opening degree to achieve the same flow rate will also vary.
Valve size: The nominal diameter of the valve determines its maximum flow capacity. For the same flow requirement, large-diameter valves need a relatively smaller opening degree, while small-diameter valves require a larger opening degree. For instance, when transporting the same flow of water, a DN100 valve may only need to be opened to 50%, while a DN50 valve may require an opening of 80% or even greater.
Fluid properties
Fluid viscosity: Fluids with higher viscosity encounter greater resistance when flowing in pipes and require a greater force to push them forward. Therefore, for fluids with high viscosity, to ensure a certain flow rate, the valve opening is usually larger than when transporting fluids with low viscosity. For instance, when transporting viscous fluids such as lubricating oil, the valve opening is generally larger than that when transporting water to overcome the viscous resistance of the fluid.
Fluid density: Fluids with higher density exert greater pressure on the valve. When controlling the flow rate, the valve opening needs to be adjusted according to the fluid density. For fluids with high density, to avoid excessive flow or high pressure, the valve opening may need to be appropriately reduced. For instance, in a pipeline system for transporting crude oil (with a density greater than that of water), the control of valve opening should take into account the density of crude oil to ensure the safe and stable operation of the system.
