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
"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
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
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
Moreover, invisible in the range of geometrical measurements, so-called hidden crank
- 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
- increased loads of roller bearings, what can be reason of high temperature and seizing;
- foundation deflections causing scratches, cracks through and damages of continuous
- 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).
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
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
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
by ZMP company.