Observables por casos (expresados en códigos), decisión de codificación y

The main objective is counting with a basic and uniform procedure that can be used when the bearings and / or supports replacement is required.

14.2 METHOS BASIS OR FOUNDATION

The bearings for rotary kiln tires, require an immediate replacement for a good kiln running when they show wear or damages due to lubrication, cooling or adjustment problems.

14.3 METHOD DEVELOPMENT

14.3.1 Equipment and tools to be used - Replacement bearing

- Crane or frame - Shims gauge

- Tools such as wrenches, etc. to remove and put the bearing cap and lock.

- Ink to mark metals (it can be oil paint, Prussia blue or red colored) 14.3.2 Periodicity

The eventuality of the kiln roller bearings replacement is made when required, because it is damaged whether by Babbitt or bronze worn, or the need exists to change the roller (or kiln tire), by trunnion shaft measure change, or by any other reason.

14.3.3 Procedure, calculation methods and results

By general rule, the bearings are supplied with a machining application corresponding to the kiln tire (or supporting roller) trunnion shaft original diameter, and with a clearance appropriately sized between the trunnion shaft and bearing, therefore if having a roller with lower (or higher) diameter than the nominal, a bearing must be placed according to this new dimension.

The trunnion shaft (or trunnion) of the kiln tire rests, theoretically, on a generatrix at the back of the bearing or lining. At a sufficient shaft rotation speed, the oil will be introduced in the space between the shaft and bearing, with wedge effect, so that a thin film will support the shaft. Depending on the speed and temperature, the thickness of such oil film can be approximately 0.01- 0.02 mm.

Therefore a very careful bearing adaptation is demanded.

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placement of a new one can be performed in the following manner:

a. Clean and dry the new bearing, eliminating paint, dirt and anticorrosive oil as well as control that it has not been damaged during transportation. Eventual damages produced by strikes or a slight polishing or reaming removes scratches.

Control that the bearing contains a smooth transition since the oil pocket (or deposit) to the supporting face, on the radial and axial surface, i.e. steps with cutting edge do not exist.

Dismount the support cover and mount the bearing in the bucket so that the pressure neck chamfered faces the pressure ring.

Control that the bearing, through the fastening pieces (in case of having them), be carefully fastened to the bucket, at level with it, and no clearance exists between the bearing and the bucket.

Remove traces left by reaming of the kiln tire (or supporting roller) shaft trunnion.

Place eye screws in the bucket corners, so that, it, with bearing, could be suspended with the bearing facing downwards. See Figure 14.1.

b. Dry the kiln tire shaft carefully and apply a very thin layer of marking ink (it can be oil paint Prussia blue colored) along all the trunnion shaft length and with a width covering approximately 120°.

c. Dry the bearing - fastened in the bucket - and place it carefully in the kiln tire, at the same time that, the pressure ring is utilized as guide when performing the lowering (or placement).

d. Push the bearing forward and backward with short axial movements (10-12 mm) as long as it rests over the trunnion shaft. Control the clearance between the bearing and the trunnion shaft, as illustrated in Figure 14.2.

e. Elevate the bearing and bucket by removing them from the trunnion shaft and control the Figure 14.1

f. If the contact is shown as a narrow strip interrupted or partially interrupted at the back of the bearing, it means that the foundation is satisfactory. See Figure 14.3.

If the contact is only shown as sporadic spots, the projecting parts regarding the bearing must be removed through slight scrapping and repeating the process until a satisfactory result is obtained.

g. Subsequently, control that the transitions between the oil channels and the support faces of the bearings are leveled. When everything has been controlled and approved, the same type of oil as the one utilized for support is poured. The tire is placed in the correct position, and the support mounting operation is finished. Apply joint paste in all the union faces in order to get the bearing watertight.

14.3.4 Interpretation of results

The results under this procedure must be positive and when the new bearing is correctly installed, the kiln will be working satisfactorily.

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Figure 14.2

Form 14.2

It is always dangerous to work close to a rotary kiln. Because it is required to work very close to it, appropriate clothing, safety goggles, safety shoes, gloves and safety shield must be utilized.

14.3.6 Condemning or permissible limits

In this procedure only successful bearings changes must be made related to the kiln running, and maintaining the bearing temperature within the range established by the manufacturer.

14.4 COMMENTS AND OBSERVATIONS

The development of a bearing replacement activity, is a job requiring persons with long experience, therefore they must be consulted when required by this procedure execution.

14.5 ATTACHMENTS AND FORMS UTILIZED

No attachments are included, and the forms to be utilized are free.

14.6 REFERENCES

- Support type 1958, Manual F. L. Smidth 19024-04 - Kiln tire bearings, Manual F. L. Smidth 18064-13

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Support