Does the term \"reduced diameter of a control valve\" refer to the nominal diameter or to the valve seat diameter?
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For example, if the pipe has a diameter of DN50 and reduction is required for calculations, can an control valve with a nominal diameter of DN50 and a seat diameter of 40 (or another desired diameter) be used? In that case, it would not be necessary to use reducers on the pipe
The reduction in diameter of a control valve usually refers to the valve seat diameter, rather than the nominal bore diameter. In the situation you mentioned, if an control valve with a seat diameter of 40 is to be used, it is necessary to consider the compatibility between the diameter of the pipeline and that of the control valve, to ensure that the flow rate is not restricted. At the same time, it is also necessary to check whether parameters such as the maximum pressure and temperature of the valve meet the requirements of the pipeline. If the selection is improper, it may affect the process flow and the service life of the valves; comprehensive analysis and calculations should be carried out before making the choice. .
Generally, reduced diameter refers to the nominal diameter! This is common in chemical plants; liquid media are generally aligned at the bottom, rather than being welded in alignment.
The diameter reduction of control valves is divided into internal diameter reduction and external diameter reduction; the valve seat diameter corresponds to the internal diameter reduction, while the nominal diameter corresponds to the external diameter reduction. The reduction in diameter of the control valve is usually achieved through selection calculations so that the valve operates at an appropriate opening degree, thereby achieving optimal control.
The relative reduced diameter of the valve seat is a bit more expensive; when designing, I usually opt for a valve seat with a reduced diameter
A decision can be made based on the flow capacity of valves from different manufacturers; in principle it is possible, but reducing the diameter to 50% of the original size is not recommended.
For small diameters, either reducing the bore diameter or the valve seat size will work; principles should be established along with the pipeline during design to avoid any omissions. Additionally, the degree of diameter reduction should generally not exceed two stages.