Methods for Inspection and Adjustment of Rotary Kiln Roller Centerline

Purpose: To ensure the kiln shell centerline is a straight line, enable uniform stress on rollers of each support station, reduce wear of rollers, riding rings and liners, and eliminate kiln axial drifting and vibration.

Common Methods: Laser alignment method (mainstream modern method), steel wire ranging method (traditional classic method). Auxiliary measurements: shell radial runout and roller level measurement.

1. Pre-inspection Preparation

1. Shut down and fully cool the kiln; cut off power, implement lockout-tagout (LOTO). Clear material deposits and oil contamination on riding rings and roller surfaces.

2. Tools required

- For laser alignment: laser collimator, targets, scales, level gauge, inside micrometer, steel rule, marking pen.

- For steel wire ranging: steel wire, plumb bobs, supports, tensioners.

3. Record original data first: roller clearances of each station, roller level, shell radial runout and kiln drifting direction.

2. Method 1: Laser Alignment Method (Recommended, High Precision)

1. Set up reference laser

Install laser transmitter at kiln head or kiln tail. Take the centers at both ends of the kiln shell as reference to generate a laser beam representing the theoretical kiln centerline, running through all support stations.

2. Mount targets

Place a center target at each riding ring position. Read the laser offset on the target to measure the deviation between the shell center at this station and the theoretical centerline.

3. Measure roller center

Measure the centers of left and right rollers, compare with the shell center to judge whether the roller centers lie on the kiln centerline; meanwhile measure the top level and gradient of rollers.

4. Documentation: level of left & right rollers at each station, center deviation, contact condition between riding ring and rollers.

3. Method 2: Steel Wire Ranging Method (Common for Conventional Overhaul of On-site Kilns)

1. Build stable supports at kiln head and kiln tail. Tighten a thin steel wire as the theoretical center reference line, which shall coincide with the kiln theoretical centerline.

2. At the cross-section of each riding ring, use plumb bobs and steel rulers to measure the distance from steel wire to shell edge and calculate the shell center.

3. Measure the transverse distance from roller center to reference steel wire to obtain roller center deviation.

Disadvantages: The steel wire sags under its own weight for long kilns; sag correction is required. Susceptible to wind effect, suitable for short kilns only.

4. Adjustment of Roller Centerline (Core Operation)

Principle: Adjust rollers instead of shell; perform minor adjustments multiple times. Large one-time displacement is strictly prohibited.

1. Judge offset direction

- Whether roller center deviates left/right relative to kiln shell centerline; check roller top level (height difference between left and right sides) simultaneously.

2. Adjustment approach: Move rollers by shims on roller base anchor bolts and transverse jackscrews.

- Transversely shift rollers to make left and right rollers symmetric about kiln centerline.

- Adjust shims to calibrate roller level and guarantee consistent elevation of two roller tops.

3. Roller gradient (to control kiln drifting)

Rollers are not perfectly horizontal; tiny inclination controls upward/downward kiln drifting. Rule: adjust in the same direction with small angles, adjust in pairs. Synchronously adjust a pair of rollers; large single-side inclination adjustment is forbidden.

Simple judgment of drifting: If kiln shell drifts toward kiln head, fine-tune roller angle to bring shell back to center.

5. Recheck after Adjustment (Mandatory)

1. Re-measure laser/steel wire center deviation and keep it within specification allowable range (normally ≤0.5 mm, subject to equipment drawings).

2. Measure shell radial runout; runout at riding rings shall meet standards.

3. Bar the kiln manually for several revolutions, inspect contact between riding rings and rollers: uniform contact band, no local indentation and no edge point contact.

4. Trial operation: no-load slow rotation, observe stable kiln drifting without abnormal vibration. Recheck after temperature rise (minor thermal deformation exists).

6. General Notes

1. Cold-state measurement ≠ hot-state condition: Reserve thermal expansion during cold alignment; final acceptance review shall be conducted under hot running condition in formal production.

2. Avoid excessive load on single-side rollers, otherwise roller pitting and riding ring cracking may occur.

3. Bar kiln and re-measure after each adjustment, fine-tune repeatedly. Single adjustment amount shall not exceed 0.2~0.3 mm.

4. Safety: Unified command during kiln barring operation to prevent crushing injury; sufficiently cool high-temperature kilns before work.

7. Simple Acceptance Criteria

①The shell centers of all stations form a straight line.

② Centers of two rollers on the same station are symmetric relative to kiln centerline.

③ Small level error on roller tops; full-width uniform contact between riding rings and rollers.

④Controllable kiln drifting and no periodic vibration during continuous operation.