Automation Parts

Renold Couplings Protect Against Eddy Currents The Renold Hi-Tec coupling range of rubber in compression couplings protects the bearings of large rotating machines from eddy current damage. Eddy currents pose a problem in rotating machinery. The larger the machine and the higher its rotating speed, the stronger these currents become. The resulting eddy currents can cause extreme damage to both sleeve and rolling element bearings. In some extreme cases, they can even cause the bearings to weld together. The high rubber content of the Renold couplings combine with the no metal-to-metal contact of the two coupling halves, which effectively insulates the motor from the driven machine. This ensures that damaging shaft currents are not allowed to flow from the motor to the bearings of the driven machine and effectively safe guards against a costly repair and failures. Machines that are most affected by eddy current damage to bearings are: fans, compressors, turbines and pumps. However,...

Renold Couplings Highlights Folly Of Fuse Theory Fuse theory, a myth related to couplings, is costing industry a fortune, according to Paul Shuffleton, managing director of Renold Hi-Tec Couplings. According to fuse theory, rubber-in-shear type flexible couplings protect diesel-driven generator sets by failing or acting like a fuse when there is a potentially damaging short circuit. This is a myth, because the majority of rubber-in-shear couplings fail through fatigue rather than because of a short circuit. This is also the main reason for failing rubber blocks. Rubber-in-shear couplings consist of a rubber element fused in-between two metal hubs. One hub drives the other through the rubber, the flexing of which protects against shock and vibration. The coupling is only as strong as the rubber element, so if the rubber fails then the coupling fails too. When this happens on a diesel-driven generator set, some engineers believe there has been a short circuit and that the relatively ...