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POWER TRANSMISSION Brakes, Clutches & Couplings Couplings are soft on pumps Pumping applications place stringent demands on couplings, but rubber-in-compression products are adept at rising to the task Rubber-in-compression couplings, from Renold Hi-Tec, are perfectly suited to pumping applications, particularly when large particulates such as sand or gravel are being pumped. The rubber blocks in the couplings eliminate torsional vibration, isolate resonance and dampen vibrations in the system that would otherwise cause early failures. Torsional vibration is caused by the almost imperceptible pulses in torque that are inherent to diesel engines and variable frequency drives, which are commonly used to power pumps. Each power stroke of the engine produces a pulse, or peak in torque that causes an indiscernible twisting of the drive shaft that will eventually destroy it if left unchecked. Each diesel engine also has its own natural resonance, a bit like the note of a ringing bell or the sound of a vibrating guitar string. If the engine’s resonance coincides with the natural frequency of the pump then the results can be catastrophic. The modern solution is to fit a torsionally soft coupling in-between the diesel engine and the drive shaft to isolate the engine’s harmonics and torsional vibration from the rest of the system. Rubber-incompression couplings are frequently selected due to their failsafe design, which is a critical requirement in many pumping applications like fire fighting for example. Rubber-in-compression couplings are made up of two round metal sections with what looks like the paddles of a paddle steamer projecting inwards from the outer section and outwards from the inner. Rubber blocks are placed in the spaces in-between the paddles, and, as the outer section is turned by the engine, the inner section is driven through the rubber blocks. As this happens the rubber is compressed and hence the term, rubber-in-compression. The couplings are failsafe because even if the rubber blocks failed the strong metal paddles would come together and continue to drive the pump. Rubber-in-compression couplings are also maintenance free and do not require lubrication or adjustment of any kind, which means they provide the lowest lifetime cost on all pump applications. The only serviceable item are the rubber blocks, which in most cases are good for over ten years of service. As well as pumping applications, the rubber-in-compression couplings have also proved their worth in other demanding areas, such as their use in a strip steel mill in the USA where they have cut torque amplification by a staggering 23 percent. The couplings were specified during the refurbishment of the plant to protect the drivelines of two reversing roughing stands and one finishing stand. One of the main causes of torque amplification is backlash across gears and couplings. The Renold Hi-Tec coupling is backlash free by virtue of the precompressed rubber blocks which not only eliminate clearance but incorporate hysteresis damping as the rubber deflects. Renold’s engineers were able to use in-house software to analyse the dynamics of the system and carefully select the correct type of coupling and rubber blocks to change the natural frequency of the system and avoid resonant frequencies. Three rubber-in-compression couplings were specified delivering up to 8MW of power each, and operating at speeds of up to 725rpm. The new couplings dramatically increased the life of the plant and cut the ongoing cost of ownership as rubber-in compression couplings are also maintenance free. Capital investment was also reduced. MORE INFORMATION: Enter D225 on the card, or visit ‘latest issue stories’ at www.industrialtechnology.co.uk for further details from Renold Hi-Tec and more news couplings 22 More details: Write in 220 on the free information card
Bellows - Huco Flex B flexible coupling solutions Whether the accent is on high torsional stiffness, generous misalignment capability, high speed operation, recyclable hubs, or a capacity for operating in push/pull mode, Huco offer the answer to all your flexible coupling needs. Call now for our new Flexible Couplings catalogue or visit our web site at www.huco.com Membrane - Huco Flex M Sliding - Huco Oldham Universal Lateral - Huco Unilat Beam Type - Huco Multi-beam Merchant Drive Hertford, SG13 7BL United Kingdom t: +44 (0) 1992 501900 f: +44 (0) 1992 509890 www.huco.com Double Loop - Huco-Flex P Jaw Type - Huco Flex G More details: Write in 230 on the free information card More details: Write in 231 on the free information card Renold Couplings Renold produces a wide range of standard and customised coupling products. These products include soft start Hydrastart fluid couplings, double and single engagement Gearflex & MB Gear Couplings as well as the ever popular Crownpin and Pinflex “pin & bush” couplings. In addition to these Renold also produce Tyreflex, Spiderflex and Discflex elastomeric couplings. International companies from Steel to Food processing, and from escalators to textile machinery have chosen Renold to solve their problems. <strong>Industrial</strong> sectors such as mining, quarrying, mineral processing, metal manufacture, cement and power generation regularly use Ajax mill Spindles, Hi-Tec flexible couplings, Renold Hydrastart, Gearflex and Pinflex couplings. If you have an application requirement, Renold will offer the solution. Superior Coupling <strong>Technology</strong> More details: Write in 232 on the free information card 23
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