Kiln Shell

Rotary Kiln Maintenance Seminar

Kiln Shell

Kiln Shell

Shell Details

Kiln Crank

Measuring Kiln Crank

Heat Correction of Kiln Crank

Shell Repair

Shell Welding

Submerged Arc Welding

Shell Details

Shell Details Inlet Cone

30 mm

Tire No. 3

Tire No. 1

Tire No. 2

40 mm (gear)

40 mm 75 mm (under tire)

30 mm

40 mm


40 mm

Typical shell plate thicknesses.

Outlet Shroud


Kiln Crank

Kiln Crank

Kiln crank occurs when a kiln shell is not perfectly straight. As the shell turns, cyclical loads and stresses occur in the shell and the kiln supports.

Kiln Crank

Kiln crank can cause severe cyclical loads, leading to shell cracks and fatigue cracks in the roller shafts.

Kiln Crank

Kiln crank will result in gear misalignment which can destroy gear teeth.

Kiln Crank

Kiln crank can be temporary, as in the case of a rain warped shell, or permanent, as in the case of a shell damaged by heat blisters.

Kiln Crank

When a hot kiln is stopped during a heavy rainstorm, one side of the shell cools off and contracts, causing a concave up curvature.

Kiln Crank

When a hot kiln is stopped too long without rotation, heat will rise and the top of the shell will expand, causing a convex-up curvature.

Kiln Crank

Irregular coating formation or refractory wear can cause one side of the shell to heat up more than the other. The result is a temporary crank in the shell.

Kiln Crank

Damaged refractory will cause a hot spot in the shell.

Kiln Crank

A hot spot left unattended will wrinkle the shell and create a crank. Refractory bricks will no longer stay in place and the shell section will have to be replaced at great expense.

Heat Damaged Kiln Shell

A heat-wrinkled kiln shell will also shorten the kiln, causing tires to run off-center.

Kiln Crank

Kiln crank can be caused by poor alignment of kiln sections during assembly or repair.

Kiln Crank

Kiln crank can be caused by weld shrinkage at a temporary shell patch.



Kiln crank can be identified by measuring roller deflection. The load on the roller will change as the kiln turns and this results in bending of the roller shaft.


A roller that deflects cyclically with kiln rotation by over 0.3 mm typically indicates a crank in the shell that should be repaired.


Kiln crank can be measured by measuring shell runout. A polar diagram is generated on which the deviation from the true kiln center can be seen.


A series of polar diagrams gives a picture of the shell crank.



A kiln shell can sometimes be straightened by heat correction. Insulation is wrapped around the shell, allowing the shell steel to overheat. Shell stresses then diminish as the kiln sags into place on the rollers.


Temperature sensors are installed to carefully monitor shell temperatures beneath the insulation during the correction process.


Shell Repair

Shell Repair

Major shell defects are normally repaired by replacing the damaged section. The bandaid approach is at best a temporary solution.

Field Joint Hardware

New shell sections are joined with adjustable erection lugs.

Shell Alignment

By adjusting the erection lugs the shell sections are straightened until a perfect centerline is achieved.

Tire Handling

Shell Rigging

Shell Rigging

Shell Handling

Spider Bracing

Spider Bracing

Spider Bracing

Shell Stiffening Rings

Many older kilns had shell stiffening rings. These rings would eventually cause shell cracks due to heat expansion. Field-cutting expansion slots may help this problem.

Shell Welding

Joint Preparation

Prior to welding the shell plate ends are carefully prepared.

Weld Shrinkage

The 60º double V weld results in less shrinkage and less weld metal being required. Weld distortion is minimized, avoiding the “gull-wing” effect.

Weld Shrinkage

Shell Welding

Shell Welding

After completing the outside weld, the root pass is removed using carbon arc gouging.

Shell Welding

After gouging, the joint is carefully cleaned and inspected to ensure that no defects from the root pass remain.

Shell Welding

When welding is finished, the joint is inspected radiography or ultrasound. Defects are marked and then repaired.






The depth of penetration increases with increased current.

The depth of penetration is also dependant of the welding speed.


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The depth of penetration is high with the welding rod as PLUS POLE and law with the welding rod as MINUS POLE.












Kiln Shell

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