Gearbox life

The decanter manufacturer will often quote the expected life of the gearbox. This will be based on the fatigue life of the gear teeth, which is proportional to the ninth power of the torque encountered. Thus, one has to be extremely careful not to overload the gearbox above its torque rating. An 8% increase of torque over its rating will halve the expected life of the gearbox. 

Each component of the decanter has its own natural frequency, even the stationary components, which could resonate sympathetically if this frequency is close to the bowl speed. The feed tube is a good example, being a long, thin tube. Apart from the inverse square relationship with length, resonance frequency is also proportional to the fourth power of diameter in its simplest form. Unless care is taken the feed tube can be caused to resonate like a tuning fork. The design engineer thus endeavours to maximise diameter and 

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Separate sections concerning allied topics, such as particle size technology and fluid flow will also be included briefly. A few important mechanical aspects will also be covered, such as resonance, maximum bowl speed, and bearing and gearbox life. 

It should be noted that if drier cakes will be obtained in the future with development of equipment, techniques or chemicals, the conveyor torque will increase. Reserve gearbox torque capacity will permit such improvement and also result in longer gearbox life. 

With oil diagnostic systems it is also possible to recognize defects inside the gearbox. On the other hand, bearing damage, for example, cannot be accurately located. Regular oil diagnosis is also recommended to maximize oil life. 

The foregoing is a rather cumbersome collection of symbols, formulae and curves. To clarify it, a retrospective calculation can be made using one of the components from the office copier gearbox. The large output gear is selected, and we can calculate its working life, as shown below. 

Consider a turbine that operates under normal conditions. Assume that the turbine is affected by a design inadequacy in the gearbox but by no other triggers. The design inadequacy causes the gearbox to age prematurely (over early life). 

The ultimate aim of this research is to yield a method for predicting the remaining useful life of any given component, engine or gearbox. 

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