What factors are related to valve opening?

Process requirements: In scenarios such as industrial production, different process processes have specific requirements for parameters such as flow rate and pressure of fluids. For example, in chemical reactions, in order to control the reaction speed and product quality, it is necessary to accurately adjust the flow of raw materials, which will be based on the specific reaction conditions and formula to determine the opening of the valve to ensure that the right amount of raw materials into the reaction kettle. In the heating system, it is necessary to adjust the valve opening and control the hot water flow according to the heat load demand of the room to achieve the appropriate indoor temperature.

Piping system characteristics

Pipe resistance: The length, diameter, inner wall roughness of the pipe and the number and type of pipe fittings such as elbows and tees on the pipe will affect the pipe resistance. When the pipeline resistance is large, in order to ensure a certain flow, it is necessary to increase the valve opening; Conversely, when the pipeline resistance is small, the valve opening can be relatively small. For example, when the pipeline is transported over a long distance and there are many pipe fittings, a large valve opening is required to overcome the resistance and enable the fluid to be smoothly transported to the destination.

System pressure: The difference between the inlet pressure and the outlet pressure of the system will also affect the valve opening. If the system pressure difference is large, in the case of meeting the flow requirements, the valve opening can be small; However, when the system pressure difference is small, it may be necessary to increase the valve opening to increase the flow. For example, in a pump-driven fluid delivery system, the pump provides a certain pressure, if the pipe outlet pressure is high, you need to adjust the valve opening to balance the pressure, to ensure that the flow meets the requirements.

Valve characteristics

Valve type: different types of valves have different flow characteristics, such as the flow characteristics of gate valves are close to linear, and the flow changes are more obvious when the opening is large; The ball valve has better truncation performance, and can achieve a larger flow control range at a smaller opening. Therefore, depending on the valve type, the opening required to achieve the same flow rate will be different.

Valve size: The nominal size of the valve determines its maximum flow capacity. For the same flow requirement, large caliber valves require a relatively small opening, while small caliber valves require a large opening. For example, when conveying the same flow of water, the valve of DN100 may only need to be opened to 50% opening, while the valve of DN50 may need to be opened to 80% or even more.

Properties of fluid

Fluid viscosity: A fluid with a higher viscosity has a higher resistance when it flows in a pipe and requires a greater force to push it. Therefore, for high viscosity fluids, in order to ensure a certain flow rate, the valve opening is usually larger than when conveying low viscosity fluids. For example, when conveying viscous fluids such as lubricating oil, the valve opening is generally larger than when conveying water to overcome the viscous resistance of the fluid.

Fluid density: The pressure generated by the fluid with higher density on the valve is larger. When controlling the flow, the valve opening needs to be adjusted according to the fluid density. For dense fluids, the valve opening may need to be appropriately reduced in order to avoid excessive flow or pressure. For example, in a pipeline system transporting crude oil (which is denser than 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.