These are the components that vary the most and possess different features. The rotor is sometimes known as the rotor assembly because it is a blend of the shaft and blades (also known as vanes) put together by welding and/or sometimes by casting. It is the rotating component of the valve. The two types of rotation systems in a valve are known as; load side rotation and return side rotation. The load side rotation system is the rotation of the blades and the pockets from the inlet to the outlet (considering one pocket, this rotation starts when the feed is supplied to the pocket via the inlet and ends when the feed gets discharged from the pocket). The return side rotation is simply the rotation of the vanes and the pockets from the outlet to the inlet (with respect to a single pocket, this rotation starts when the pocket gets emptied and ends when the feed refill starts at the inlet). Rotors have different numbers of vanes, 6, 8, 10 and so on. The greater the number of vanes the better the sealing ability and the lower the number of vanes the bigger its pocket capacity. For low pressure differential zones between the inlet and the outlet, the wider pockets provide great advantage like handling large sized bulk materials. The wider pocket will generally fill at a greater percentage for a specific rotating speed compared to the narrow pocket. In addition, slightly sticky materials tend to get released easily from such pockets. Free falling materials are impacted less by the number of vanes. The rotor design is dependent on the function that it is to perform, each rotor has its own special characteristic.
There are two fundamental types of rotors used in rotary valves, the open-end rotor, and the closed-end rotor. Custom rotors are also possible to suit the users demands. The rotor to housing surface relationship accounts for a wide range of parameters including functionality and wear.
This is the most commonly used rotor, it is known as an open-end rotor because the pockets are open at each end. The material is contained on each end by the valve housing. The rotor blade has three tips, the two tips at each open end and one adjacent to the housing. Wear of this component (vane) occurs on the three tips when the material is in contact with them.
Closed-end rotor is designed in such a way that the pockets are enclosed by plates (also known as a shroud) on both sides. This setup reduces the three tips to one thus reducing the wear surfaces to one (the housing bore surface). This type of rotor offers better sealing than the open-end rotors.
The other types of rotors used for handling different bulk materials in a rotary valve include rotor with elastic polyurethane tips, metering rotor, reduced volume rotor, replaceable bladed rotors (also known as adjustable bladed rotors), and scalloped rotors (also known as radius pocket rotors).
Adjustable bladed rotor
This rotor is used to handle abrasive materials. The types of materials it handles may lead to premature wear of the tips. The tips can be replaced easily to keep tight clearance between the housing and the blades.
Rotor with elastic polyurethane tips
Similar to the adjustable bladed rotor, the elastic polyurethane rotor has replaceable polyurethane tips. Flexible tip designs are used for large sized particles and moderate abrasive powders.
The scalloped rotor has smooth pockets that help with the discharge of sticky materials.
This is a small precision rotor for highly controlled flow. It is used to feed powdered and granular materials in small amounts by metering. It is mostly used in the food and pharmaceutical industries when handling expensive active ingredient.
Reduced Volume Rotors
This rotor is designed with filled rotor pockets. This rotor is used for feeder applications where the valve flanges need to match a set size of the inlet and outlet. The volumetric capacity of a rotary valve is decreased to match required throughput with a good degree of accuracy. This type of rotary valve rotor is good for handling free flowing and slightly cohesive products.
Wide range of rotary valve models and configurations are available for different process conditions and physical properties of transferred bulk solids. According to process (silo, cyclone, jet filter, conveyor, pneumatic conveying system etc.) ; according to bulk material (fine powder, granule, abrasive, elastic, high temperature etc.)
Throughout the industrial sector, the use of a rotary valve is undeniable. Since its inception, its use in industries has progressively grown. Its utilization can range from food and pharmaceutical to agricultural and milling industries – nearly every industry out there makes use of it to its full capacity.