CAPITULO III. ANALISIS
3.2. Configuraciones brutas y resultados contradictorios
6.1 OBJECTIVE AND SCOPE
The objective is to maintain the rollers (or kiln tires) in correct position in order to control the axial pushing exercised by them.
6. 2 METHOD BASIS OR FOUNDATION
The kilns by design require an inclination to operate, and for this reason a status must be maintained so that the axial pushing is controlled in order to maintain the kiln free of pressure or floating.
Different types of kiln design exist, which have different needs to maintain the kiln in flotation.
6.2.1. Floating kilns
In these kilns the requirement is fundamental in the adjustment of support rollers by inclinating them, to carry the axial gravitational pushing and by this way maintaining the kiln in a floating position. In this position, the tire (kiln tire) does not have contact with any axial pushing rollers (candlesticks), when the kiln has load and when the temperature conditions are considered as normal as long as the material is being processed. From this floating position, the kiln is displaced upwards or downwards until getting contact with the axial pushing rollers (candlesticks).
6.2.2. Kilns with gravitational or complete axial pushing
These kilns are usually long, heavy, and with antifriction bearings on the axial pushing assemblies (candlesticks), and they are capable to allow axial gravitational loads, with all the kiln support rollers on a neutral position, with the longitudinal shaft parallel to the kiln shaft.
6.2.3. Kilns with axial pushing hydraulically operated
The arrangements where the hydraulically operated axial pushing is utilized, consist essentially in a hydraulic jack positioning the kiln and pushing it upwards when the pump is activated and when the kiln is to be lowered or returned to its position, the pump is stopped. The constant travelling of kiln intends to eliminate the unequal wear of tires (kiln tires), and the gearings teeth in transmission.
6.3 DEVELOPMENT OF THE METHOD
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6.3.1 Equipment and tools to be used - Measuring tape
- Impact wrench to move rollers bearings - Dial Indicators (watches)
6.3.2 Periodicity
The axial pushing revision must be made every 6 months as minimum, although a daily inspection per shift will provide a clear idea about the need to make adjustments in the rollers inclination in order to prevent overloads in the axial pushing rollers.
6.3.3 Procedure, calculation methods and results 6.3.3.1 Floating kilns
In these kilns the axial pushing rollers must not be forced to perform pushing operation, only check that it does not have overload.
The bearings movement must be monitored by watch (dial) indicators in order to prevent an over adjustment of any assembly, and having all the support rollers with an approximate equal load. See Figure number 6.1
The adjustment begins with a known neutral position, by positioning the rollers longitudinally parallel to the kiln shaft, the rollers start inclination, as required by the kiln rotation direction, to move the tires upwards or downwards, beginning to displace the kiln shell, reacting to the rollers movements. See Figures 6.2 and 6.3.
The variances in material quantity inside the kiln, affect the rollers and the kiln axial movement. With rollers inclined for a long period in typical conditions, the heaviest production loads will increase reloads in the axial pushing roller (candlestick) in the direction(s) determined by the inclination angle.
Heavy loads cause severe reactions, light loads cause light loads.
Axial push roller
It need to have contact
Hydraulic push
It need to have contact
Hydraulic push Rim
Axial push roller Lower.
It need to have contact
Hydraulic push
As the axial pushing assemblies are capable to carry gravitational axial loads, it is required that the support rollers are in a neutral position and parallel to the kiln shaft.
In order to make corrections, the best practice is to make small movements regarding the rollers neutral position, by deliberately inclining the rollers to make their pushing plates push downwards. In many cases, this can be done by inclining them 0.125 mm - 0.250 mm in the parallel position correct direction.
Figure 6.2
Figure 6.3
6.3.3.3 Kilns with hydraulically operated axial pushing
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ROTATION
INSERT
INSERT
FURNACE OUTLET
THE ROLLERS MOVE TOWARDS THE OUTLET THE FURNACE MOVES TOWARDS
THE ROLLERS MOVE TOWARDS THE OUTLET THE FURNACE MOVES TOWARDS
THE ROLLERS MOVE TOWARDS THE OUTLET THE FURNACE MOVES TOWARDS
THE ROLLERS MOVE TOWARDS THE OUTLET THE FURNACE MOVES TOWARDS THE FEED SIDE
RIM
the kiln shaft, to make the kiln traveling freely.
To make adjustments, the procedure is equal to the previous case, moving the screws to their neutral position. This can be made by a slight inclination to lighten part of load in the axial pushing hydraulic system to move the kiln to its upper position.
It is extremely important that the inclination adjustments in the support rollers do not cancel totally the kiln gravitational pushing; in this manner it is possible to move the kiln upwards without the help of the hydraulic system.
6.3.4 Interpretation of results
The movements performed must be recorded in the attached forms, and this will serve for future movements, which will strongly depend on the kiln type and its load.
6.3.5 Safety concerns
It is always dangerous to work close to a rotary kiln. Due that measuring and compare the parallelism and flotation of kiln rollers it is required to work very close to the kiln, the appropriate clothing, safety goggles, safety shoes, gloves and safety helmet must be utilized.
6.3.6 Condemning or permissible limits 6.3.6.1 Floating kilns
The point to be observed here is to never let the axial pushing rollers be overloaded, it means that the 6 mm separation must exist between the tire or tread ring and the axial pushing rollers.
6.3.6.2 Kilns with gravitational axial pushing
As in the previous case, but with the difference that in the lower axial pushing roller contact must be made with the tire (kiln tire) tread ring, and the separation with the other axial pushing roller, will be maintained in 6 mm.
6.3.6.3 Kilns with hydraulically operated axial pushing
The kiln must normally be allowed to travel a distance between 38 and 50 mm, from the lower position to the upper position.
adjustment movements must be made from 0.125 mm to 0.250 mm at the same time, followed by a waiting period to let the kiln react, until the moment when the axial pushing conditions are corrected by the supporting rollers, and for kiln arrangement.
A rule of thumb exists to perform the movements, and it consists in the following:
1.- Place a hand as though you were holding (grasping) the roller in favor of its spinning sense.
2.- The index and thumb are extended.
3.- The index finger indicates the bearing pushing, and the thumb indicates the adjustment or movement caused in the kiln.
4.- As the thumb indicates the direction towards the movement will be made, from here can be seen what hand is used, left or right, and corresponding to the left bearing and right bearing respectively (if the roller is seen from the front position).
6.5 ATTACHMENTS AND FORMS USED
The most commonly used forms are the following:
Form 6.1 -Parallelism and flotation of kiln rollers.
Form 6.2 -Position of kiln rollers.
6.6 REFERENCES
- Recommended procedures for mechanical analysis of rotary kilns, Book by Robert Chapman, edited by Fuller Company.
- Support bearings and kiln tire alignment, Manual F. L.
Smidth No. 18074-07
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