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Measurement of roller shafts' dynamic deflection

Kiln shell's state, or shell's state of rotary drum's with similar design, it is used to be estimated with application of so-called measurements of geometry. These measurements consist in evaluation of shell's run-out in individual object's planes, located along kiln's length in adequate density. Thanks to this we can get maps of eccentricity and local deformation distribution, what is the base to make decision about remedial activities /1/.
But these measurements have very essential mistake. Visual view of these maps shows us clearly, that in support places - in places of rings' mounting - vector of eccentricity is close to zero value and deformations are significantly reduced.
So it suggests a question: do deflections of shell's axis take places only between supports? Answer is obvious: surely not.
Apparently, with relatively flexible shell, weight of ring is significant enough and stiffness of rollers considerably enough, that shell is not capable of making free from put on it constraints.
Only in extreme cases, deflection of shell leads to "rings' jumps", what is displaying as loss of contact between it and rollers /2/.
"Rings' jumps" phenomenon occurs very seldom. Vector of eccentricity bigger than static deflection of shell in support point - for case of removed this support - it is the condition when phenomenon occurs, so it is case, when we can find eccentricity in the range of shell's support section /3/.
Static deflection very often achieves dozens of millimeters and even a few hundred (depending on shell's flexibility). From this reason "rings' jumps" are the rare opportunity.
But it doesn't mean, that, along with lack of shell's run-out in the range of support section, the problems can be omitted.
Shell's deflection causes cyclical changeable loads of roll-ers, thus cyclical changeable deflections of rollers' shafts. These deflections, distinct from static deflections coming from roller and kiln nominal weight, are called dynamic deflections.
These deflections are main reason of material fatigue and, coming from it, roller shafts' cracking, what is the one of least desirable failures of kiln /4/.

Moreover, invisible in the range of geometrical measurements, so-called hidden crank causes:
  • increased stresses and shell deformation (ovalization), what has disadvantageous for strength and fatigue state (possibility of shell cracks) and it radically reduces durability of kiln lining;
  • increased pressures between raceways of rollers and rings, leading to accelerated wear;
  • increased loads of roller bearings, what can be reason of high temperature and seizing;
  • foundation deflections causing scratches, cracks through and damages of continuous footing;
  • different failures unforeseen in effects, coming from sudden kiln's stoppage as a result of shafts' cracks (even bigger kiln deflection, destruction of drive system, destruction of outlet and inlet seal elements etc).

DynShaft device

Taking mentioned above factors into consideration, ZMP has designed and made device with catalogue name DynShaft, serving for measurement of roller shafts' dynamic deflection during normal operation of kiln /5/.
Measurements, realized thanks to this new device, are at present inseparable whole in process of shell's state evaluation. It gives possibilities to reliable inspection without any fear of disregarding of factors, what is difficult to pick out only in the geometrical measurements' way.
Such comprehensive attitude to kiln shell state analysis or analysis of similar construction shell, showed above, minimize risk of wrong decision in the range of shell's cranked axis straightening.

LT DynShaft device

Complex measurements of kiln shell's geometrical state are numbered among activities - very laborious and not every time economically justified, even the shell axis's state arouses suspicion.
From this reason, and also taking into consideration preventive requirements imposed on kilns' users, ZMP firm worked out simplified version of device (LighT), giving possibilities of periodical, independent control of roller shafts' deflection, to done by user /6/.
LT version device gives opportunity to maximal shaft's deflection's estimate and informs about circumference location of kiln, where the extremum of deflection is situated.
LT version has got also possibility of recording and future reproducing of data. Moreover it is equipped with alert option informing if data is over permissible value, as well as it has got module to self-control of measurements.

For special order, it is possible to work out the interface for transmission, store and data's analysis, dedicated to Windows system (for PC class computer).

It is possible also to join measurement of shafts' deflection in Internet, diagnostic so-called Your Audit OnLine system, offered by ZMP company.

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