Main components of a rotary drum are rings and rollers, which are forming its support
The drum's working movement is rotation, additionally accompanied by axial displacements.
Resistance of both movements is closely dependent on the contact conditions between
the surfaces of rollers and rings. Correct contact between the two is guaranteed
only when the raceways of both components are cylindrical in shape.
Unfortunately, even during normal operation, rotary drum is exposed to numerous
factors, which in a long run will cause deformation of the contact surfaces, making
the rolling components loosing their original shape in a larger or smaller degree.
Such factors are:
- roller shafts misalignment /1/,
- ring axial run-out /2/,
They result in excessive and unevenly distributed loads on the contact surfaces
of the ring and the rollers.
Complete elimination of the above-mentioned factors is difficult, and sometimes
even impossible. Shape errors (/3/
) are therefore
inevitable, and their magnitude and rate of occurrence depends on the number and
values of faults.
Errors, even the smallest, disturb the correct distribution of forces in the rotary
drum's support system, forming points where the unit loads exceed the permissible
In extreme cases such errors can cause serious disturbances in the drum's movements,
both rotary and axial.
Movement resistance and incorrect distribution of forces can result in considerable
damage, such as:
- wear, breaks of the thrust stop blocks
- bearing bushing damage by excessive loads
- breaks of the roller shafts' thrust collars,
- hastened wear of the rollers and rings raceways caused by increased unit loads in
their contact areas /8/, /9/.
Such a movement resistance has also a negative effect on the drive system, where
the teeth wear in the gear unit is following faster /10/
. This creates a feedback which
results in further deformation of the rings raceways, this time as characteristic
Removal of such a damage entails significant costs caused by both, production downtime
and elimination process of the failure results.
Other important elements of rotary kiln support system are the thrust rollers. By
taking part of the axial forces acting on the object's support system, they are
often exposed to considerable loads. For this reason, it is very important to ensure
the proper roller's positioning and raceway contact with the front surface of the
live ring, so the forces distribution will be even and there will not be any formation
of excessive stresses or vertical forces - over pressing or picking-up the thrust
roller on the frame. What in extreme case may lead to total failure of roller structure
or damages of live rings' suspension system.
Periodical checks and restoration of the correct shape of live rings and support
and thrust rollers raceways is desirable from the technical point of view and fully
The shape can be restored in a traditional way: by dismantling and machining on
stationary equipment. In such case, the downtime is inevitable: if the rollers are
refurbished, the downtime will be shorter (a few dozens of hours); in case of the
ring, the downtime will be fairly longer (several weeks).
The costs of restoration are also sizeable, and include amongst others:
- dismantling and re-assembly (in case of the ring, often the kiln's shell needs to
- transport (difficult, as the parts are usually oversize),
- machining (machine tools are few and expensive).
Machining without dismantling any parts of the facility, even during its normal
operation can significantly reduce such costs.
In case of the support and thrust roller, which axis of rotation is relatively stable,
for turning and grinding operations we can use more or less adapted traditional
In case of rings raceway, continuous changing of the axis position, necessitates
much more sophisticated and refined technology, unavailable on a day-to-day basis.
The machining requires also a deep knowledge and an extensive experience in measurements
and adjusting of such facilities.
The knowledge and experience which dispose ZMP engineers, together with the state
of the art equipment, allow effectively resurface rollers and rings raceways without
the necessity of their dismantling.
Appearing always in case of the ring and sporadically in case of the support roller,
displacements of the rotary axis of the machined element, are compensated by the
rotary joints which allow machine to follow-up to the right position.
Constance of the diameter is assured by the proper design of the rolling guiding
system. The idea of the solution is basing on the three points determination of
the circle diameter. Constant holding down is provided by the pneumatic cylinder.
Thanks to that machining parameters are constant what is very important for the
obtaining good quality surface after grinding.
SCOPE OF SERVICE
Having in our disposal so specialized machines supported by our engineering knowledge
of rotary drums related problems, we can offer you a complex service of support,
thrust rollers and live rings raceways resurfacing.
The service contains:
- qualifying analysis, to determine advisability and possibility of resurfacing service;
- measurement and engineering assistance over the support roller’s position adjustment;
- resurfacing of the roller /12/ / ring raceway /13/ with control of the diameter
and shape of the generating line of the grinded element;
- resurfacing of the thrust roller - restoration of the initial generating line shape
- resurfacing of live ring’s front surface – in contact with thrust roller - restoration of the outline and/or cone’s angle
- no need for costly and time-consuming dismantling and re-assembly;
- elimination of expensive transport to and from the machining facility;
- minimizing the production losses (only in extreme situations resurfacing could disturb
production process - necessity to decrease rotation speed of the drum in case of
high vibration level of resurfacing elements);
- during machining, the reference line is actual axis of rotation of the piece (high
accuracy, minimal shape errors);
- low surface roughness after regeneration.
- grinding of the raceways of support rollers, live rings (tires) – rolling raceways and front surfaces and thrust rollers of rotary drums without dismantling;
- grinding of other large rotary pieces, without dismantling (indispensable rotation
of the resurfacing element).