Case Study: Kiln Alignment at NSW Cement Plant

TL;DR: This kiln alignment cement plant NSW case study follows a Southern Highlands clinker producer whose 4.2 m diameter, 64 m rotary kiln was throwing red-hot tyre dust, running a roller bearing 18°C hotter than its pair, and chewing through thrust roller faces. ISS ran a hot survey while the kiln turned to capture its true operating geometry, then a cold confirmation survey inside the annual shutdown, and supervised the roller adjustment that followed. The kiln was returned to within 0.4 mm/m axis tolerance, bearing temperatures evened out, and the work was completed inside the planned 96-hour outage with no schedule slip.

Key takeaways

• A hot rotary kiln alignment survey, taken while the kiln turned at roughly 1,450°C burning-zone temperature, showed the carrying axis bowed 6.8 mm out of line at the centre pier — a fault that a cold survey alone would have understated because thermal growth had partly masked it.
• Measurement was done with a Leica Absolute Tracker AT960 for the cold roller geometry (±0.015 mm at 10 m) and a Leica MS60 MultiStation for the hot non-contact shell and tyre observations, all tied to a local control net and reduced against ISO 1101 geometric principles rather than any single Australian Standard, because none prescribes kiln tolerances.
• The root cause was not the kiln itself but 9 mm of differential pier settlement at the No. 2 (centre) support, confirmed by levelling against AHD benchmarks and GDA2020/MGA2020 Zone 56 control — the kiln was faithfully following a foundation that had moved.
• Supervised cold adjustment of the No. 2 carrying rollers brought the axis back inside 0.4 mm/m and squared the thrust roller, dropping the hot bearing's running temperature from 71°C to 54°C within two days of restart.
• The full scope — hot survey, cold survey, adjustment supervision and reporting — was delivered for AUD $19,800 inside the existing 96-hour shutdown window, against a deferred-failure exposure the site costed at well over AUD $1.2 million for an unplanned tyre or shell failure.

The plant and the problem

The client operates an integrated cement works in the NSW Southern Highlands, producing ordinary Portland clinker for the Sydney and Illawarra construction markets. The asset at the centre of this case study is a single-string rotary kiln: 4.2 m internal diameter, 64 m long, supported on three tyres and six carrying rollers, with a hydraulic thrust system holding the kiln on its three-degree downhill slope. At full production it turns at roughly 3.5 rpm with a burning-zone temperature around 1,450°C, and it is the single most expensive piece of plant on site to lose.

The reliability engineer flagged three symptoms over a four-month window. The No. 2 (centre) tyre had begun throwing fine red oxide dust — a classic sign of relative slip and edge loading between tyre and roller. The inboard bearing on the No. 2 downhill roller was running 18°C hotter than its uphill partner, trending up. And the thrust roller face was wearing unevenly while the hydraulic thrust unit cycled more often than its baseline, meaning the kiln was no longer "floating" cleanly between its limits.

Individually, none of these is unusual. Together, on a kiln of this age, they point to a geometry problem: the rotational axis was no longer straight, and the kiln was loading its supports unevenly as a result. The site had two questions. What is the actual misalignment, in millimetres, while the kiln is running hot? And can it be corrected inside the annual 96-hour shutdown already booked for September, without an extra outage?

Why a hot survey came first

The instinct on most sites is to wait for the shutdown, let the kiln cool, and measure it cold. That gives the cleanest geometry, but it answers the wrong question. A rotary kiln does not run cold — it runs at temperature, and a 64 m steel shell grows several millimetres as it heats. The geometry that wears tyres and overheats bearings is the hot, turning geometry, not the static cold one.

So ISS mobilised first for a hot survey, with the kiln in full production. Using the Leica MS60 MultiStation in non-contact mode, the team observed the rotating shell and the three tyres from established control stations, capturing the running axis without touching the kiln or interrupting clinker output. Each tyre centre was derived from multiple shell observations per revolution and averaged across dozens of rotations to filter out shell crank and ovality.

The hot survey told the real story. The carrying axis was bowed, with the No. 2 tyre sitting 6.8 mm low and off-line relative to the straight line drawn between the No. 1 and No. 3 tyre centres. Crucially, this was worse than the eventual cold figure — thermal growth had partly lifted the centre of the kiln, so a cold-only survey would have understated the running fault and risked an under-correction. Capturing the hot geometry first is what let the team specify an adjustment that would be correct once the kiln returned to temperature.

The cold survey and finding the real cause

When the September shutdown began, the kiln was barred to a stop and allowed to cool below 40°C — verified by infrared thermometer before any contact instrument went near it. ISS then ran the cold confirmation survey with a Leica Absolute Tracker AT960, the right instrument once physical adjustment is the goal because supervised shimming needs a target that is not breathing.

The cold survey measured each carrying roller individually: roller diameter, slope, skew and the precise position of each roller axis relative to the kiln centreline. It confirmed the bowed axis seen hot, and it isolated the No. 2 station as the problem support, with the roller skew driving the tyre edge-loading that had been throwing dust.

The decisive measurement, though, was the levelling. ISS levelled the three pier soleplates against site AHD benchmarks, with all control tied into GDA2020 on MGA2020 Zone 56. The No. 2 centre pier had settled 9 mm relative to the outer two piers. The kiln was not bent — it was straight, and faithfully following a foundation that had subsided. This changed the recommendation entirely. Shimming the rollers alone would have corrected the symptom while leaving a slowly settling pier underneath; the report instead specified a roller adjustment to recover safe running now, plus geotechnical monitoring of the No. 2 pier on a six-month cycle to confirm the settlement had stabilised.

Equipment and method

All instruments carried current ISO/IEC 17025-traceable calibration certificates. Because there is no Australian Standard prescribing rotary kiln geometric tolerances the way AS 1418.18 governs crane runways, results were assessed against the OEM design data, ISO 1101 geometric tolerancing principles, and the practical industry tolerance of 0.4 mm/m on the carrying axis. The hot work and confined approaches near the kiln were covered by the site's permit-to-work and ISS's own SWMS, with surveying scheduled around the burner and refractory crews so no trade waited on another.

The result

The adjustment was carried out by the site's mechanical crew under ISS supervision, with the tracker live so each shim and roller movement was verified in real time rather than measured after the fact. The No. 2 carrying rollers were repositioned and re-skewed, and the thrust roller squared to the tyre.

The kiln was realigned, restarted and back to full clinker production inside the 96-hour shutdown window, with no additional outage required. Within two days of restart the No. 2 bearing temperature had settled at 54°C and tracked steadily, the tyre dust had cleared, and the thrust unit returned to its normal cycling band.

The outcome for the operator

The commercial logic is straightforward. The full ISS scope — hot survey, cold survey, supervised adjustment and a traceable report — came to AUD $19,800. The exposure it closed out was an unplanned tyre or shell failure, which the site's own reliability team costed at well over AUD $1.2 million once lost clinker production, emergency repair, and contractor mobilisation to a regional site were included. Catching the fault as a geometry-and-settlement problem, while the kiln was still running, converted an emerging unplanned failure into a line item inside an outage that was already booked.

Just as important, the levelling result reframed the maintenance plan. The operator now knows the kiln is geometrically sound and that the variable to watch is the No. 2 pier foundation, not the kiln steel. Six-monthly settlement levelling against the same AHD benchmarks gives an early-warning trend, so the next intervention can be planned around real data rather than the next time the bearings overheat.

Frequently asked questions

Why survey a kiln hot rather than just waiting for the shutdown?

Because the kiln runs hot, not cold. A 64 m shell grows several millimetres as it heats, so the cold geometry is not the geometry that wears tyres and overheats bearings. In this case the hot survey showed a 6.8 mm fault that the cold survey understated — measuring only cold would have risked an under-correction that left the kiln still mis-running once it was back at temperature.

What accuracy is achievable on a rotary kiln this size?

For the cold roller geometry, the Leica AT960 tracker holds about ±0.015 mm at 10 m, far tighter than any kiln tolerance. The limiting factor is the kiln itself — shell ovality, crank and thermal movement — not the instrument. The practical, defensible target on the carrying axis is 0.4 mm/m, which this kiln was returned to.

Is there an Australian Standard for kiln alignment tolerances?

No. Unlike crane runways, which AS 1418.18 governs, there is no Australian Standard prescribing rotary kiln geometric tolerances. ISS works to the OEM design data, ISO 1101 geometric principles and ISO/IEC 17025-traceable measurement, with control on GDA2020 / MGA2020 and levels on AHD. Methodology and traceability are what make the result defensible.

Could the roller adjustment have been done without the survey?

Not safely. Adjusting rollers by feel or by chasing the hot bearing would have corrected a symptom while leaving the bowed axis and the settling pier untouched. The survey isolated the No. 2 station, quantified the 6.8 mm misalignment, and — through levelling — revealed that 9 mm of pier settlement was the true driver, which changed the recommendation from "shim and forget" to "adjust now, monitor the foundation".

How long does a kiln alignment like this take, and does it stop production?

The hot survey is done with the kiln in full production and stops nothing — typically one to two days on site. The cold survey and supervised adjustment are done inside a planned shutdown; here the entire cold scope fitted within the existing 96-hour annual outage with no extra downtime.

Industrial Spatial Solutions delivers hot and cold rotary kiln alignment surveys for cement, lime, alumina and mineral-processing operators across NSW and nationally, using Leica laser trackers, total stations and traceable control to turn geometry problems into planned, costed maintenance. If your kiln is throwing tyre dust, overheating a bearing, or simply due for its alignment baseline, call ISS on 0407 057 015 to scope the work around your shutdown calendar and request a fixed-price quote.