What is the pressure difference for using a sleeve control valve?
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As stated in the title, SH/T 3005-2016 specifies that sleeve control valves are suitable for use in applications where there is a large pressure difference before and after the valve, where the fluid may experience flashing or cavitation, and where the fluid does not contain solid particles. I would like to ask everyone: how should one determine when the differential pressure before and after is relatively large? What value constitutes a significant differential pressure? Is 2 MPa considered high?
For the control valves in the main feedwater pipelines of ordinary boilers, sleeves are commonly used; for example, when the main feedwater pressure is 6.4 MPa and the main steam pressure is 3.8 MPa, the pressure difference across the control valve exceeds 2 MPa.
There is no clear distinction, and besides sleeve valves there are other options; usually, other factors such as price and importance are taken into consideration. In fact, when the selection criteria for control valves allow for choked flow, sleeve valves can be included in the selection options. One of the features of sleeve valves is that cavitation occurs in a position at the center of the sleeve where there are no components, so they have good resistance to cavitation. But it has little effect on eliminating flashing (other methods can be used, such as a sleeve + cage). .
Whether to choose a sleeve for the valve depends on the valve diameter, pressure difference, and the thrust output of the actuator. In simple terms, the larger the valve port diameter, the smaller the allowable pressure difference; if the pressure difference is high, the actuator can be slightly enlarged or a sleeve can be used.