25-08-2017, 09:32 PM
PNEUMATICS CONVEYOR SYSTEM
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INTRODUCTION TO PNEUMATICS
Pneumatics is the use of pressurized gas to affect mechanical motion. Pneumatics is that branch of technology, which deals with the study and application of use of pressurized gas to affect mechanical motion. Pneumatic power is used in industry, where factory machines are commonly plumbed for compressed air; other compressed inert gases can also be used. Pneumatics also has applications in dentistry, construction, mining, and other areas.
Gases used in pneumatic systems
Pneumatic systems in fixed installations such as factories use compressed air because a sustainable supply can be made by compressing atmospheric air. The air usually has moisture removed and a small quantity of oil added at the compressor, to avoid corrosion of mechanical components and to lubricate them.
MATERIAL HANDLING EQUIPMENTS
Material handling equipment is all equipment that relates to the movement, storage, control and protection of materials, goods and products throughout the process of manufacturing, distribution, consumption and disposal. Material handling equipment is the mechanical equipment involved in the complete system. Material handling equipment is generally separated into four main categories: storage and handling equipment, engineered systems, industrial trucks, and bulk material handling.
Engineered systems
Engineered systems are typically custom engineered material handling systems. Conveyors, Handling Robots, AS/RS, AGV and most other automated material handling systems fall into this category. Engineered systems are often a combination of products integrated to one system. Many distribution centers will optimize storage and picking by utilizing engineered systems such as pick modules and sortation systems.
Equipment and utensils used for processing or otherwise handling edible product or ingredients must be of such material and construction to facilitate thorough cleaning and to ensure that their use will not cause the adulteration of product during processing, handling, or storage. Equipment and utensils must be maintained in sanitary condition so as not to adulterate product.
Industrial trucks
Industrial trucks usually refer to operator driven motorized warehouse vehicles. Industrial trucks assist the material handling system with versatility; they can go where engineered systems cannot. Forklift trucks are the most common example of industrial trucks but certainly aren't the extent of the category. Tow tractors and stock chasers are additional examples of industrial trucks.
Bulk material handling
Bulk material handling equipment is used to move and store bulk materials such as ore, liquids, and cereals. This equipment is often seen on farms, mines, shipyards and refineries. This category is also explained in Bulk material handling.
Pneumatic Conveyor Systems
Every pneumatic system makes use of pipes or ducts called transportation lines that carry mixture of materials and a stream of air. These materials are such as dry pulverized or free flowing or light powdery materials like cement, fly ash etc. These materials can be transported conveniently to various destinations by means of a stream of high velocity air through pipe lines. Products are moved through various tubes via air pressure, allowing for extra vertical versatility. Pneumatic conveyors are either carrier systems or dilute-phase systems; carrier systems simply push items from one entry point to one exit point, such as the money exchanging tubes used at a bank drive-thru window. Dillute-phase systems use push/pull pressure to guide materials through various entry and/or exit points. Three basic systems that are used to generate high velocity air stream: 1. Suction or Vacuum systems: utilizing a vacuum created in the pipeline to draw the material with the surrounding air.The system operated at a low pressure, which is practically 0.4-0.5 atm below atmosphere, and is utilized mainly in conveying light free flowing materials. 2. Pressure Type systems: in which a positive pressure is used to push material from one point to the next. The system is ideal for conveying material from one loading point to a number of unloading points. It operates at a pressure of 6 atm and upwards. 3. Combination systems: in which a suction system is used to convey material from a number of loading points and a pressure system is employed to deliver it to a number of unloading points.
DESIGN CONSIDERATION FOR PCS
Pneumatic conveying is a practical method for in-plant distribution of large amounts of dry powdered, granular, and palletized materials. Based on the quantity of air used and pressure of the system, pneumatic conveying system is divided in to two type’s viz. dense phase pneumatic conveying system and dilutes phase pneumatic conveying system. In dilute phase conveying, solid particles are introduced into a fast flowing gas stream where solids remain suspended. Such process systems operate at relatively low pressure and consequently are comparatively inexpensive to install. (5)
Dense-phase pneumatic conveying is defined as the conveying of particles by air along a pipe which is filled with particles at one or more cross-sections. There is much confusion over the use of the term dense-phase conveying and, as a result, many different definitions have been proposed, based on the solid loading ratio, pressure and quantity of air used. Easiness in controlling and flexibility in installations are some of the favourable features of pneumatics applications in many industrial and nonindustrial fields. It has a wide range of applications, with examples ranging from domestic vacuum cleaners to the transport of some powder materials over several kilometres. (5)
The industrial field where pneumatic conveying system is extensively used includes Chemical process industry, Pharmaceutical industry, mining industry, Agricultural industry, Mineral industry, and Food processing industry. Virtually, all powders and granular materials can be transported using this method. (5)
EXPERIMENTAL ANALYSIS OF THE SYSTEM
The conveying potential of the system is of prime importance while selecting a pneumatic conveying system for a particular application. Number of factors has a potential influence on material flow rate. They can be grouped into three broad categories viz. those associated with the material required to be convey, the conveying conditions and pipeline geometry.
The Material To Convey
The factors required to considered related to material to be conveyed include mean particle size, particle size distribution, particle shape, particle and bulk densities, particle volume friction, air retention and permeability. Decision of using pneumatic conveying system for particular material greatly depends on these properties.
The Conveying conditions
Material conveying condition that have a direct influence on material conveying potential includes solid loading ratio, conveying line pressure drop, and air flow rate or conveying air velocity. Of these conveying line pressure drop is the only fully independent variable since both solid loading ratio and conveying air velocity are additional material dependent. Air velocity, pressure, and solid loading ratio decides whether the system is dense phase or dilute phase.
The Pipeline Geometry
The factors required to be considered related to pipeline geometry includes the length of the pipeline, the bore of the pipe and number of bends in the pipeline, bend radius ratio. Power required operating the system increases with increase in pressure drop of the system. The pressure drop of the system depends on the horizontal and vertical length of the system, bends in pipeline. Whereas the quantity of air required increases as the size of the pipeline increases.
These variables are generally required to be considered for the analysis of pneumatic conveying system. (5)