3-Base Kiln

Since the 1800s, FLSmidth has been continually improving its high-quality kilns to solve complex challenges – and to deliver the market’s highest production rate

Rotax kiln_FLSmidth
  • The basics
  • Design & Supports
  • Maintenance

Key benefits

  • Sturdy and flexible, full-welded rotary kiln
  • Long run time before maintenance is needed (low brick wear)
  • Effective inlet/outlet seals
  • Minimal kiln tyre wobbling
  • Simple, high-quality tyre support
  • Longest life span and best production rate of any 3-base kiln
  • Extra retention time achievable for materials of difficult burnability

How it works

The 3-base kiln is a high-quality, traditional three-support rotary kiln system ranging from 3.6–6.6m in diameter and 55–95m in length. Its balanced design ensures optimal stiffness and flexibility and minimises wobbling and misalignment.

Loose-fitting blocks are held in place by bushings bolted to the kiln shell. This allows restorative shimming to take place without dismantling bolts – lessening both maintenance costs and the chance of possible crack formations.

Optional extended design

If desired, the 3-base kiln can also include an optional extended design with a longer retention time that is ideal for processing kiln feed with a high Burnability Index (BI). This extended design is also beneficial when using certain types of alternative fuels.


The durable design of the kiln’s drive station tolerates high levels of shell expansion and contraction.

The girth gear and pinion are cast and machined from high-grade steel. The girth gear is attached by bolted-on spring plates that are welded to the kiln shell, allowing full expansion of the shell.

The pinion and the gear rim are enclosed in a gear guard, protecting the gearing from invasive dust and preventing lubrication spillage.


Each live-ring is supported by cast-steel rollers shrunk onto the enlarged diameter of the forged steel shafts. The rollers themselves are bolstered by robust bearings that can accommodate operational irregularities.

Graphite seals

The graphite seals at the inlet and outlet of the kiln reduce false air intake yet allow enough flexibility to follow the kiln’s movements.

The seals require no greasing and are practically maintenance-free.


Most mechanical problems with rotary kilns are caused by just four conditions. Regular inspections of the following can help you avoid them:

1. Kiln axis geometry – kiln axis geometry must be aligned, as it determines the distribution of the weight load among the kiln supports and the longitudinal distribution of bending stresses in the kiln shell.

2. Kiln ovality – make sure that the kiln shell’s radius of curvature does not change unacceptably during the kiln’s rotation.

3. Kiln crank – monitor kiln shell temperature. Check for red spots on the kiln shell and misaligned kiln shell sections.

4. Axial kiln balance – measure trust face temperatures to make sure the axial forces are not too large.

Kiln maintenance
Kiln maintenance