The regulator mainly selection control and basic common sense

by:AIRWOLF     2020-05-18
Choose the regulator, the first to collect a complete process of fluid physical properties parameters and regulator of the working conditions, the main composition of fluid, temperature, density, viscosity, normal flow, maximum flow and minimum flow, maximum flow and minimum flow of import and export pressure, maximum pressure. Technology in the major control and determine the structure of the regulator itself, flow characteristic, Kv rated flow coefficient value, diameter size, process allows the differential calculation and selection of the actuator, the content of the material and installation, etc. Choose regulator with general should follow the principle of has the following several points. A regulator structure: should be able to meet the medium temperature, pressure, liquidity, flow, and the adjusting range and rigor request. The flow characteristic of regulating valve: should be able to meet the reasonable compensation system characteristics. Regulating valve of flow characteristic refers to the relative flow medium through the valve and stem the relationship between the relative displacement, mathematical expression is as follows: Q/Qmax = f ( l/L) , Q/Qmax as relative flow type, for regulating valve in an opening when the ratio of the flow Q to fully open flow Qmax; L/l as the relative displacement, the regulator in a when opening the valve core displacement and the ratio of the displacement of full open l l. Choice is the general principle of flow characteristic of regulating valve should be contrary to adjust the object properties and regulator characteristic, can make comprehensive features of the adjustment system so close to linear. Alternative flow characteristic in the process is usually under system requirements, but also consider the following situation. 1, the linear flow characteristics, scope of application: (1) the differential changes little, almost constant; (2) process the change of the main parameters of a linear; (3) most system pressure loss allocation on the regulator ( The opening of the change to change differential pressure valve is relatively small) ; (4) external disturbance is small, given value change is small, small adjustable range of requirements. 2, such as percentage characteristics, scope of application: (1) the actual wide adjustable range; (2) the opening change, the valve differential pressure changes in a relatively large; (3) pipeline system pressure loss; (4) process system load fluctuation significantly; (5) regulator often run in the small open degrees. 3, in addition to the above two common flow characteristic, and parabola and open characteristics, and other flow characteristic of regulating valve. Three: the calibre of the valve should be able to meet the requirements of the process of flow. According to the known condition of fluid, calculate the necessary Kv value, choose suitable valve diameter.
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