Rotary valve is a general term sometimes used to describe valves with a rotary action such as ball, butterfly, plug valves.
The term is also used specifically for a design of valve used to dose precise quantities of powders or liquids into a process stream. The closure is machined with a series of cups to hold the done and may be continuously rotated through 360 degrees or partially rotated to provide dosing. A particular design is the cup ball valve typically used in chemical plants
A rotary valve is used for the transfer of fine free flowing powder or granules from one chamber to the other. The control valve should be precision machined and used in fully closed condition. Any leakage will cost problems in the material transfer. You should select the appropriate valve needed for your process. One valve that is designed for a particular process should not be used for another. It is very important to coordinate well with the suppliers to be able to choose which one is suitable for your needs.
A rotary valve controls the flow of dry powder and other solid granules under gravity and a vacuum condition in a circular motion. Its parts should be precision machined to make sure that they would fit and perform they way it is expected to do and allows to be used in pressurized conditions. Each design is suited only for a particular purpose and not be used for other purposes.
Rotary valves are used in controlling the flow of dry and free flowing particles usually powder and granules in solids handling system. The system usually operates under gravity or vacuum conditions. A material will enter the inlet part and fall into space between the blades. When the blades rotate the material will be carried toward the outlet. The design of the valve should prevent any accumulation or build-up of the material in any of its parts to avoid clogging that will lead to malfunction of the control valve.
Proper maintenance of the rotary valve is needed as it will give more life and usage to its main parts and other components. The wear and tear of its parts will be inspected so that before its use you can find out which parts need replacement and avoid breakdown in the middle of operations. Always refer to the product manual before you start with any maintenance activity. There you will also know the frequency of maintenance as recommended by the supplier.