Roots Blowers have been a common utility in cement plants for a very long time now. Whenever a large volume of air is to be used at constant pressure, a Roots Blower is the right equipment.
The Roots Blower design was patented way back in 1860 by Philander Higley and Francis Marian Roots. The name of the equipment is derived from the name of the scientist; the blower is recognised as ?Roots Blower? or ?Rotary Air Blower? in the industry.
The executing mechanism of the blower is intake of air from the inlet; dual impellers rotating in different directions or the same direction trap the air during the rotation between the casing and impeller and discharge at the outlet. The mechanism of the blower is unique and traditional. The blower throws a consistent volume of gas to the outlet without discharge. The gas-blowing capacity of a Roots Blower depends on the size of casing and rotating part. Thus, a Roots Blower is unique compared to a compressor. The manufacturing of Roots Blowers is done either by SMEs or MSMEs in various parts of the country. There are a good number of manufacturers meeting the requirement of the industry.
The blowers have higher efficiency at moderate compression ratios, and are most efficient in the compression ratios of 1.1 to 2. They find use in applications which require relatively constant flow rate at varying discharge pressures. There are various types of Roots Blowers, mainly categorised as air-cooled blowers and water-cooled blowers. The capacity of blowers varies from 10 M3/Hr to 14000 M3/Hr. The blower should be made up of good quality and sturdy parts. There should be no machine vibration during operation execution, as this may bring down the blowing capacity of the machine. The Roots Blower must be a power-saving unit, and continue functioning over a long period of time, with low electricity consumption.
Twin-lobe rotary air blowers consist of a pair of involute profiled (shape of 8) lobes/rotors rotating inside an oval-shaped casing, closed at ends by side plates. One lobe is the driving lobe, which is driven by external power, while the driven lobe is driven by a pair of equal ratio gears. Both lobes rotate at the same speed, but in opposite directions. As the rotors rotate, air is drawn into the inlet side of the cylinder and forced out of the outlet side against the system pressure. With each revolution, four such volumes are displaced.
In the case of three-lobe rotary blowers, the shape of the rotor is different. The two three-lobe rotors rotate in a direction opposite to each other. Running on the same operating speed, three-lobe blowers can deliver larger air flow and volume than conventional two-lobe blowers.
Since the lobes run within the casing with finite clearances, no internal lubrication is required. Thus, the air delivered is 100 per cent oil-free. These blowers deliver, practically, a constant flow rate independent of the discharge pressure conditions. The flow rate is largely dependent on the operating speed.
These machines are extensively used in applications such as pneumatic conveying, aeration, cement plants, water treatment plants for filter backwash, aquaculture, aeration etc. They are used as general utilities, more commonly where the distance is short and a large volume of air is required (during blending, aeration, fluidisation and conveying).
Fuller-Kinyon (FK) Pump
The Fuller-Kinyon (FK) Pump was first introduced in 1926. It is a very versatile equipment, popular for lower power consumption, less maintenance needs, and increased efficiency, flexibility and reliability over other pneumatic systems. It is commonly known as an FK pump or a Screw Pump and it is ideal for conveying fine powders without risk of blowback. The design of the pump ensures that a material seal is formed when the product is compacted in the barrel and forced against the counterweighted flapper valve preventing air leakage back through the screw. Only one moving part means less maintenance and high reliability in the most demanding environments. It has an inlet for supply of compressed air.
The FK Pump operates with line pressures up to 30 psig. Parts can be replaced without removing the pump from service. Recent technological improvements on the FK Pump include the use of high-wear pump screws, and the pneumatic flap controller for optimisation of throughput of the system.
Screw Pumps are constructed of mild and structural steel, and mounted on a base. These pumps can be equipped with pedestal blocks that support a pump screw which helps to provide a smooth, balanced operation. The screw is dynamically balanced. Areas of this screw, along with other parts of the pump in direct contact with the material to be conveyed, are made of hardened, wear-resistant material and special hard surfacing where required. The screw is directly coupled to the driving motor but can be V-belt driven.
The materials to be conveyed enter from the hopper by gravity. Then the material is compacted as it is advanced. Its density is further increased in the space between the terminal flight of the screw and the face of the non-return valve to form a seal against the transport line pressure, thus preventing blowback.
The material then enters the discharge body, is fluidised by compressed air, and is conveyed into the transport line.
Dry bulk materials are conveyed literally anywhere a pipeline can be run and to any number of delivery points. Distances of 4,500 feet (1,371 meters) are not uncommon.
Multinational companies like FLSmidth are well-known suppliers of these types of pumps. Currently, upgrades of the pump are available.
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