A rotary valve can be classified as a type of spool valve and in this valve, the ports would run axially instead of circumferentially. These valves are used for the continuous discharging of bulk powder or granules under the gravity flow. A rotary valve can be considered as a feeding device that would feed granular solids between fluid atmospheres that must remain isolated from each other. The rotary valves are designed in a way that they can be used as discharge and dosing valves for powdery and granular bulk material or as intake valves for the pneumatic conveying system. These valves are used in a process where it does not get a reaction with the rotary valve materials and also it must not vary the properties of the rotary valve in a dangerous way.
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What are the functions of rotary valves?
The major function of a rotary valve is to regulate the flow from one chamber to the other and it should be done while maintaining a good airlock condition.
A rotary valve is used to provide powdered or granular solids between areas of different pressure while it would still maintain the pressure differentials and product flow. The mass flow capacity of the rotary valve is dependent upon the particle characteristic, roughness, size, and revolution of the rotary valve.
Major functions of a rotary valve
- It is used to do the airlock in pneumatic systems
- It can do product metering
- It can also be used as a combination of both airlock and feeder for pneumatic conveying systems
- It could act as an explosion barrier
- It could act as a flame barrier
- It can isolate the process
What are the components of a rotary airlock valve?
This valve is a discharging machine that has an impeller, bearing, oil seal, airlock shell, end cover, and other spare parts. The valve top has a flange and it will be connected to the unload opening of the discharger, to receive the material from the discharger and then remove the material from the valve while the impeller is rotating. The impeller can prevent the material from blocking as well as reduce the airlock’s weight and shape.
How does a rotary valve works?
The rotor in the rotary valve rotates at a constant speed and thus it would move the waste product which is separated from the air and this could be in powdered form, from the top to the bottom of the rotary valve. Because of the air-tight compartments, there is no pressure loss in the installation. The waste product is then removed from the rotary valve to a discharging device and this could be like a conveying belt or a suction pipe and from there it is moved to waste management.
How to select a rotary valve?
- It must be selected according to the size and speed
- Filling efficiency
- Valve throat size
- Gas leakage
- Operating temperature
- It must be selected according to the through-put
How can we use a rotary valve as airlocks and feeder
This valve can act as an airlock valve where an air seal is required, it can be used at the end of the vacuum system where the product is transferred from a filter receiver to a hopper. So if this valve is not used then the air would be drawn up through the discharge by the blower. These valves are used as a feeder so that it will discharge a given rate of the product.
What are the advantages of a rotary valve?
- Rotary valves are simple
- Low cost
- It only needs simple control for the effective operation
- These valves can be used under the silo emptying, cyclone discharging, dust collection system, dosing, mixing, etc.
What are the limitations of a rotary valve?
- If the pressure differential across the rotor is high, then the filling efficiency will be low
- These valves could not create the product flow, it can only pass product that can fall into it and out of it under gravity
What are the applications of rotary valves?
- Paper industry
- Chemical industry
- Petro-chemical and gas
- Power plants
- It is also used for food and pharmaceutical applications
- Cement industry