15-02-2013, 12:39 PM
DESIGN OF SHAFT AND ROTOR ASSEMBLY FOR ROTARY AIRLOCK VALUE
1DESIGN OF SHAFT.doc (Size: 2.78 MB / Downloads: 59)
INTRODUCTION
The main function of a Rotary Air- lock Valve is to regulate the flow of material from one chamber to another while maintaining a good airlock condition. The material or product being handled is usually dry free flowing powder, dust or granules.
In operation, a motor and drive chain turn the rotor shaft, spinning the rotor inside the housing and head plates. As the blades rotates a fixed volume of material passes through the material inlet to the spaces between adjacent blades (called rotor pockets) and is carried in the pockets toward the material outlet.
Rotary Air-lock Valves are used at the bottom of Bins, Cyclones, Dust Collectors or Feed Hoppers to discharge materials at a controlled rate or act as an Airlock. They are also used to introduce materials into positive or negative conveying systems. A Rotary Feeder / Airlock Valve consists of a rotor which turns at a given RPM in close clearance to it's casing thus maintaining a uniform rate of material flow and provides a seal.
The Rotary Air-locks provide reliable service in high pressure, high temperature and other severe service conditions. The valves can be used in various industries such as food, plastics, chemical, asphalt, mining, baking, cement and paint.
ROTARY AIR-LOCK VALVE
EXPLANATION OF A ROTARY AIRLOCK VALVE:
Rotary airlocks are referred to by many different names. Some are appropriate, and some are not. There are three appropriate names which are universally accepted when referring to this product. Technically, they all refer to a similar device in terms of design and appearance. These are:
1. Rotary Feeder
2. Rotary Valve
3. Rotary Airlock
Most suppliers and users are familiar with all these terms. We will focus on the term ‘rotary airlock’ for the purpose of this discussion. To further identify the name ‘rotary airlock’, we will define the two separate terms.
ROTARY
Refer to this figure and locate the vanes and pockets. The word ‘rotary’ refers to the fact that during operation of a rotary airlock, the vanes turn or rotate. As they turn, the pockets, which are formed between the vanes, become rotating pockets. The material being handled enters the pockets at the top, through the Inlet port, travels around in a rotating motion, and exits at the bottom, or through the Outlet port. As the vanes and
pockets continue to turn, material continues to be moved from top to bottom, or from Inlet port to Outlet port, in a rotating motion.
AIRLOCK
Refer to above figure, the word ‘airlock’ means that this device is to act as a seal, or lock to the air, between the Inlet and Outlet ports, while moving material in a continuous rotating motion through its pockets. Material travels downward from Inlet port to Outlet port, but airflow is restricted. To provide a reference in discussing airflow through the rotary airlock, we have notated a 10 PSI air pressure on the Outlet port side. The air pressure, in this example, is trying to push airflow up through the rotary airlock.
Operating Principle:
The material is fed into rotor pockets (A gap between two vanes) from hopper or bin. Due to rotation of shaft vanes also rotates. Due to rotation of vanes the, material in the rotor pockets will be transferred from inlet of airlock valve to its outlet. From outlet it will go to the pneumatic conveying system.
BEARINGS
A bearing is a machine element, which supports another moving machine element .It, permits a relative motion between contact surfaces of the members, while carrying the load.
Classification of Bearings:
Though the bearings may be classified in many ways, yet the following are important from the subject point of view.
a) Depending upon the direction of load to be supported: The bearings under this group are classified as
1) Radial bearings and
2) Thrust bearing.
In radial bearing the load acts perpendicular to the direction of motion of the moving element.
In the thrust bearing the load acts along the axis of rotation.
b) Depending upon the nature of contact: The bearing under this group are classified as
1) Sliding contact bearing and
2) Rolling contact bearing.
In the sliding contact bearing, the sliding takes place along the surface of contact between the moving element and the fixed element.
In the Rolling contact bearing, the steel balls or rollers are interposed between the moving and fixed elements. The balls offer rolling friction at two points for each ball or roller.
In Rotary Airlock valve deep groove ball bearings are used.