Rotary Kiln Maintenance SeminarKiln Shell

Kiln ShellShell DetailsKiln CrankMeasuring Kiln CrankHeat Correction of Kiln CrankShell RepairShell WeldingSubmerged Arc Welding

Shell Details

Shell DetailsTypical shell plate thicknesses.

Kiln Crank

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

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

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

Kiln CrankWhen 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 CrankIrregular 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 CrankDamaged refractory will cause a hot spot in the shell.

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

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

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

Measuring Kiln Crank

Measuring Kiln CrankKiln 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.

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

Measuring Kiln CrankKiln crank can be measured by measuring shell run-out. A polar diagram is generated on which the deviation from the true kiln center can be seen.

Measuring Kiln CrankA series of polar diagrams gives a picture of the shell crank.

Heat Correction of Kiln Crank

Heat Correction of Kiln CrankA 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.

Heat Correction of Kiln CrankTemperature sensors are installed to carefully monitor shell temperatures beneath the insulation during the correction process.

Heat Correction of Kiln Crank

Shell Repair

Shell RepairMajor shell defects are normally repaired by replacing the damaged section. The band-aid approach is at best a temporary solution.

Field Joint HardwareNew shell sections are joined with adjustable erection lugs.

Shell AlignmentBy 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 RingsMany 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 PreparationPrior to welding the shell plate ends are carefully prepared.

Weld ShrinkageThe 60 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 WeldingAfter completing the outside weld, the root pass is removed using carbon arc gouging.

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

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

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc WeldingThe depth of penetration increases with increased current.The depth of penetration is also dependant of the welding speed.

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

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding

Submerged Arc Welding