Although most direction control valves are of spool type design, other types are also used. One such design is the rotary four-way valve, which consists of a rotor closely fitted in the valve body.
The passages in the rotor connect or block-off the ports in the valve body to provide the four flow paths. The design shown above is a three-position valve in which the centered position has all the four ports blocked. Rotary valves are usually actuated either manually or mechanically.The operation of this valve is illustrated below (Figure 6.13).
This design contains lapped metal-to-metal sealing surfaces which form a virtually leak proof seal. The gradual overlapping of the round flow passages produce a smooth shearing action which results in lesser load on the handle during operation and absence of sudden surges. Also there is no external leakage because of the presence of a static seal on the rotating shaft (non-reciprocating and non-pressurized). The high-pressure regions are confined to flow passages. This type of valve can take higher velocities and more flow than a spool valve of the same size.
These valves are available in a variety of three-way and four-way and two- and three position flow path configuration.