Bare-shaft Blower Overview
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Principles of The Roots Type Blower
Each rotor of a Roots type blower turns at an equal speed but in the opposite direction to the other. This is achieved by using a pair of equal ratio gears to drive the rotors. Using this type of configuration, blowers can run without internal lubrication to the rotors, as they never come into contact with either the outer casing or each other, thus air is delivered completely oil free.
As the rotors turn, air is drawn into the inlet side of the blower and travels around the outer casing of the machine in the pockets between each lobe of the rotor. Once at the discharge side of the blower the air is forced out and stopped from passing back into the chamber by the finite clearances between all it's internal components. The tiny amount of air that does manage to pass back through these minute clearances is what's known as the blowers “Slip”.
There is no change to air volume within the blower (i.e. no air compression takes place). The air is simply displaced from the intake side, to the discharge side of the blower, against the resistance of the system pressure. Roots blowers are therefore able to deliver a constant airflow, independent of the discharge pressure conditions, and the rate of flow is largely determined by the blowers operating speed.
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The Adams Ricardo SR blower range is based on five gear centre sizes from 70.5mm to 197mm with low, medium and high pressure models available throughout. Virtually any combination of airflow and pressure is available from 20 to 6200 m3/hr (10 to 3650 cfm) with a full 1.035 bar gauge (15psig) delivery pressure available at all flows up to 4620 m3/hr (2721 cfm)
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The unique engineering features include rotors of cycloidal form with carbon tip inserts which:
• maximise airflow and efficiency
• minimise energy consumption
• minimise running temperatures
On start-up, the carbon tip beds in, leaving an absolute minimum running clearance compatible with blower duty. When the time comes eventually for an overhaul, these carbon tips can be quickly and easily replaced to restore the original clthearances and efficiency. Timing gears are positively fixed to the rotor shafts by a unique, precision dowelling process. This ensures accurate and automatic phasing on assembly and eliminates the need for specialist tools and skills.
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• Exhausters: All units are suitable for operation as vacuum pumps up to 15”hg vacuum.
• Performance graphs: detailed pressure and vacuum charts can be supplied for each selection.
• Oil free air: vented air gaps between the air chamber and the lubrication system prevent contamination of air flow.
• Guaranteed performance: all blowers /exhausters are dynamically balanced and fully tested. Test certificates are available if required.
• Full warranty: all units carry a warranty against faulty workmanship and materials.
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The HE range
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In their standard form our HE blowers are equip for the delivery of air up to a pressure of 1bar and a negative vacuum of 500mb abs. Special versions for the delivery of other gaseous media are also available upon request. In total there are 13 sizes of blower available, with cubic volumes ranging from 7 - 10,000m3/h. An increase of pressure or vacuum can also be made possible through the use of blowers linked in series, or by the use of water jet pumps.
The blowers in our new series are of the Roots type and incorporate a combination of all the advancements from previously produced blower types. This brings with it the knowledge and assurance that this new range of blowers uses the very latest designs and developments which have been gained by our continually improved product range.
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Key Design Features
• Rotors All our blowers use a tri-lobe design which greatly reduces air pulsations in the pipeline. This reduction plays a key role in extending the expected service life for such components as membranes, flexible hoses and other perishable All rotors are dynamically balanced, further reducing mechanical vibrations which can cause bearing failure or stress fractures to silencers and connected pipe work.
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| • Construction The blower body and end plates are cast from GJL250 and GJL200 cast iron. The body is also optimally ribbed in order for sufficient heat dispersal and for added rigidity. Rotors and shafts are cast in one piece from GJS500 ensuring optimum strength. This process can be seen in the picture of the three rotors, showing from raw casting to finished product. |
| • Sealing Gears and drive end bearings are both oil lubricated, with the air chamber isolated from the oil sumps by means of labyrinth seals and piston rings. This method of sealing virtually eliminates any chance of oil contaminating to the air supply. |
| •Gears The gears are manufactured with direct and oblique teeth, hardened and ground to give a minimum service life of 100,00 hours of trouble-free operation. The connection of the gears to the shaft is designed according to the blower size, and involves either pressing the gear directly onto the shaft, or fitting by means of a special cone clutch with high security against twisting. |
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