From the spool buck

Spool structure of single-stage buck and multi-stage step-down of the points. Single-stage step-down structure due to the pressure difference across the large, suitable for low noise, cavitation serious occasions. Where high noise reduction requirements, severe cavitation should be used as shown
In a multi-stage step-down structure, the differential pressure across the control valve is divided into several differential pressure so that cavitation does not occur in less pressure of the grading and flash phenomenon, thereby preventing cavitation and flash evaporated born, and greatly reduce the noise.
From the flow characteristics, according to the different changes in the flow area can be divided into linear performance, the percentage of properties, features quick, the parabolic characteristic, hyperbolic and some amendments characteristics. Flow characteristics, J Pi represents the relationship between the stem displacement and fluid flow. Typically, the use of flow characteristics to compensate for the non-linear characteristics of the controlled object. The spool the shape or the shape of the sleeve hole decision control valve flow characteristics. Straight drive spool can be divided into flat type (for quick opening), the plunger type, window type and sleeve type. Figure 2-30 is a schematic diagram of three commonly used control valve sleeve sleeve, due to changes in the open area, the valve shifts pneumatic hand valve
Flow area, are also different, in order to achieve the desired flow characteristics. Plunger-type valve and window-type valve can also be based on the desired flow characteristics
There are different shapes. The rotary valve spool also have different shapes, e.g. conventional valve used in the butterfly valve plate, the dynamic contour of the valve plate;
The structure of the O-hole for ball valve, V-shaped openings and modified openings.angle seat valve