Flow Characteristics of Final Control Elements

In the first Part of the presented Article the hydraulic basics for determining the flow characteristics of actuators, for example Gas pressure regulators, are explained. The main relevant flow equations and the corresponding approximate solutions are derived. The approximate solutions will be analysed and compared with the exact results. The second Part of the article contains the derivation of the equations for calculating the flow coefficient (KG-value). Practical applications of KG-value will be explained. The KG-value is compared with the Cg-value according to DIN EN 334. The authors recommend the application of the KG-value to compute the flow characteristics of actuators.