Metso Full portfolio Kiln and pyro equipment maintenance
Maximize the efficiency, availability, and longevity of your kiln. We provide guidance on what to look for to evaluate the operation of core components and help you reach your sustainability targets.

Why partner with Metso?

Reduce power consumption

Kiln alignment is critical in equalizing loads to reduce stress and power consumption

Increase uptime

Reduce the probability of unexpected downtime by preventing equipment failure with routine maintenance

Improve safety

Routine maintenance can prevent breakdowns and eliminate related safety concerns, inconvenience, and costly repairs

Lower operational costs

Good maintenance habits go a long way toward keeping your kiln healthy and minimizing operating expenses

Get to know your kiln

Rotary kilns have many moving parts and as the kiln ages, these parts can start to move very differently. Whether you’re a kiln expert or a newcomer, it’s always important to review the basics, starting with the key components that make up your kiln.

Kiln anatomy
Kiln anatomy
End seal

End seal

What it is

Located at the point of transfer between the rotating element and the stationary hood or duct. Kiln seals are used to minimize drawing excess air and expulsion of kiln gases.

What to watch for

  • Exessive run-out of the kiln shell
  • Overheating of the seal
  • Damaged or inverted seals
  • Dust or gas escaping from the seal
  • Wear and tear of the seal components

What you can do about it

  • Start with performing visual inspections
  • Take key health measurements - temperature, shell run-out
  • Replace individual leaf seals or the complete assembly if work out
  • Switch materials or upgrade to double or triple leaves

End seal

Riding ring

Riding ring

What it is   

Commonly referred to as a tire, the riding ring is located at every carrying station.  It wraps the kiln shell, providing radial stiffness and a contact area for kiln rotation.

What to watch for

  • Visual wear patterns - check for shoulders, tapers, convex or rolled edges, flat-spotting, or grooving
  • Physical damage - check for indentations, cracks, or spalling
  • Contact wear - check the interface of retaining components or thrust face to the side of the tire

What you can do about it

  • Start with performing visual inspections
  • Take key health measurements – creep, temperature, diameter, tire axial runout
  • Consider tire grinding, alignment, or potentially replacing the riding ring


Riding ring

Kiln shell

Kiln shell

What it is

Assembled sections of rolled steel, typically known as “can sections”. The overall length and diameter of kiln shells are determined by process needs.

What to watch for

  • Physical damage - check for any visual cracks
  • Loose or falling refractory
  • Any shell deformations – kiln crank

What you can do about it

  • Start with performing visual inspections
  • Take key health measurements – temperature, ovality, shell profile, and run-out
  • Consider repairing or potentially replacing the shell section


Kiln shell



What it is

The burner provides the heat required within the process to dry or carry out a chemical reaction in the product within the kiln or dryer. Heat is generated by burning fuels that can be gas, liquid, or solid in the presence of oxygen, normally provided by an air supply.

What to watch for

  • High emissions
  • Internal damage to kiln
  • Inefficient system performance
  • Reliable and current safety systems

What you can do about it 

  • Kiln/dryer survey and audit
  • Burner tuning/optimization
  • Burner upgrade
  • Safety system upgrade


Carrying station

Carrying station

What it is

Located at load piers, the carrying station includes the base frame and all support mechanisms (bearing assemblies, trunnions, etc.).

What to watch for

  • Overheating
  • Contamination
  • Excessive vibrations and noises
  • Leaking oil
  • Visual wear patterns on the roller - check for shoulders, tapers, concave or rolled edges, flat-spotting, grooving

What you can do about it 

  • Start with performing visual inspections
  • Take key health measurements – temperature, differential roller shaft deflection
  • Lubrication/oil testing and analysis
  • Perform trust adjustments
  • Consider repairing or potentially replacing the component

Carrying station

Drive system

Drive system

What it is

The drive system enables the rotary kiln to rotate. It is comprised of the main gear, a drive pinion, and a motor/reducer assembly.

What to watch for

  • Gear and pinion backlash
  • Radial and axial alignment of the bull gear
  • Excessive vibration
  • Visual wear patterns - steps, tapers, offset, the contact pattern
  • Proper lubrication

What you can do about it 

  • Start with performing visual inspections
  • Take key health measurements – temperature, axial/radial alignment, backlash
  • Consider continuous monitoring, realignment, weld repairs, component replacement, or upgrade

Drive system

Kiln alignment is critical

Left untreated, horizontal and vertical misalignment issues on rotary kilns can lead to unpredictable operation, decreased reliability and safety concerns. Alignment is also a key factor in extending equipment lifetime, optimizing maintenance costs and improving sustainability.

Why alignment is so important

Why alignment is so important

Alignment of the shell or drum between the support piers, gear to pinion, and tires to support rollers, is necessary for all rotary units. The benefits of keeping key components in alignment include:

  • Equalization or optimization of loads on support piers
  • Reduced power consumption
  • Lower component wear rates for riding rings, support rollers, gear and pinion, thrust roller, bearings, etc., resulting in greater sustainabiity
  • Reduced refractory stress and wear 
  • Reduced risk of shell damage by refractory failure
  • Reduced unplanned stoppage risk 
Alignment methods

Alignment methods

Hot alignment and mechanical analysis

Hot alignment allows adjustment of the kiln to the optimum level without interrupting production for multi-pier, refractory-lined kilns. Using the latest technology, the analysis typically includes items such as shell profile and run-out, ovality measurement, differential roller shaft deflections, gear, and tire axial run-out, as well as roller and tire diameter measurements. Corrections to alignment are made on the run. Hot kiln alignments are also beneficial in determining the shell axis prior to shutdowns where major work is planned.

Cold alignment

Cold alignment is executed during a shutdown period to correctly realign the kiln in order to benefit production and safeguard your equipment. This is typically carried out on smaller units such as coolers, dryers, and carbon regeneration kilns, with or without refractory lining, and running spherical roller bearings.

Evaluate your options

Evaluate your options

Because OEMs and repair companies apply different methods to calculate kiln misalignment, you might find it challenging to evaluate the service proposals you receive from suppliers performing their version of a hot-kiln alignment. When looking for support in kiln alignment, there are a few considerations to

What is included in the alignment?

An Alignment Analysis of the unit is often combined with a Mechanical Survey in order to identify, diagnose, and correct any issues before they develop into major problems. Metso Alignment Analysis contains a range of measurements using different tools to ensure all key parameters are analyzed.

How experienced are the service providers?

The use of accurate and proven procedures, performed by experienced and qualified personnel should be of paramount importance to the operator. Metso has crews with many hundreds of hours of experience on all makes and types of rotary equipment.

Is the latest technology being employed?

Proper diagnostics tools and methods should be utilized. For example, some rely on measurements of the riding ring and the associated tire slip or creep. However, given that the tire surface can be irregular due to wear and is often contaminated with lubricant and dust, basing kiln alignment on tire measurements alone is of questionable accuracy. Metso uses state-of-the-art high-frequency laser equipment to capture data with a high degree of accuracy, calculating the position of the kiln shell rotational axis at each support. Calculations include allowance for flexure, shape distortion, and eccentricity of the shell.

Routine maintenance

Performing regular inspections and maintenance are vital for kiln operators. They can prevent breakdowns and eliminate related safety concerns, inconvenience, and costly repairs. Overall, good maintenance habits go a long way towards keeping your kiln healthy and minimizing operating expenses.

Daily kiln maintenance

A walk-by inspection should be performed daily.

  • Check lubrication levels for the carrying roller
  • Check lubrication levels for the gears
  • Verify kiln shell axial position
  • Ensure cooling water flow for the carrying roller
  • Verify the burner’s fuel and air connections for leaks
  • Visually check the flame shape

Weekly kiln maintenance

These inspections should be performed weekly, in addition to the daily checks.

  • Measure kiln tire creep
  • Note major component wear
  • Check the kiln drive amperages for fluctuations
  • Check kiln seals and shell run-out on feed and discharge ends
  • Check drive bolt tightness – visually check for loose bolts
  • Verify the kiln shell temperature profile for fluctuations in operating temperatures
  • Survey general pilot and burner settings including operating pressures and flow rates

Monthly kiln maintenance

  • These inspections should be performed monthly, in addition to the daily and weekly checks.
  • Check the auxiliary drive motor to ensure it is available in an emergency situation
  • Check the pitch line separation between the drive gear and pinion for changes in the gear mesh
  • Inspect gear reducer oil levels and all drive bearings for high operating temperatures
  • Perform vibration analysis of the gear and pinion, gear reducer, and drive system bearings

5 Quick tips for effective maintenance

  1. Put together a detailed maintenance plan
  2. Record all information and activities in a log
  3. Be proactive with maintenance – it always pays off
  4. Kiln issues can be complex. When it comes to major repairs, it’s good to get a second opinion
  5. Kilns are one piece of your process – it is important to take a step back and evaluate holistically

Factors to watch

Similar to visiting a physician for an annual physical exam, the health of your rotary kiln should be followed and examined regularly as well. Keep an eye on the following core areas and key indicators.

Kiln shell ovality

Kiln shell ovality

Shell flex or ovality occurs at each pier. This condition is marked by a radial irregularity or deviation from the circular shape at the horizontal axis, and an assumed equal and opposite deviation at the vertical axis.

Causes of kiln shell ovality:

Undersized or worn tires

  • Shell thickness and clearance between tire bore and shell outside diameter, also known as creep or diametrical clearance
  • Misalignment causing excessive loads on support rollers

Effects of kiln shell flex

  • Refractory crushing and failure
  • Shell plate cracking (typically at a weld)
Kiln tire creep

Kiln tire creep

Tire migration, also known as tire creep, is the difference in the circumferential distance traveled between the tire and shell in one revolution i.e. the amount that the tire lags or “creeps” behind the shell.

Causes of kiln tire creep

  • Wearing of kiln components that reduce the diametrical clearance between the tire and shell
  • The thermal differential between the tire and shell

Effects of excessive kiln tire creep

  • Increased ovality (refractory crushing, failure, and shell cracking)
  • Component wear (filler bars, tire blocks, and tire bore)
Shell profile and run-out

Shell profile and run-out

Shell profile (or out-of-roundness) is a permanent deformation of the kiln shell. This is normally referred to as shell blisters, shell warp-age, shell twisting, or coke bottling.

Kiln shell run-out (or eccentricity), is the inaccuracy of kiln shell rotation about its true center. It is the radial offset about the true center of rotation of the kiln. This situation is commonly referred to as a kiln shell crank, dog leg, or a banana in the kiln shell.

Causes of shell out-of-roundness and run-out

  • Overheating of kiln and components
  • Loss of refractory
  • Damage to the kiln shell
  • Emergency shutdown, where proper cooling and slowing the kiln was not possible

Effects of shell out-of-roundness and run-out

  • Physical distortions of both the refractory condition inside the rotary kiln and the integrity of the kiln shell
  • Higher drive amps and excessive loading on carrying mechanisms
  • High differential roller shaft deflection
  • High ovality on the kiln shell
Gear axial & radial run-out

Gear axial & radial run-out

Gear axial runout and radial runout refer to the misalignment of the main gear as it rotates. Radial run-out is checked to ensure proper alignment between the gear and the pinion, while the axial runout is important to ensure proper face contact between the gear and pinion.

Causes of gear axial runout and radial run-out

  • Improper installation
  • The eccentricity of the kiln shell (shell runout)
  • Shell deformation (shell profile)
  • Kiln misalignment

Effects of gear axial runout and radial run-out

  • Heavy tooth wear and damage
  • Insufficient/excessive root clearance
  • Excessive vibrations
You can rely on our expertise
You can rely on our expertise

Keeping your kiln healthy and running at its best can be a big job. Luckily, OEM partners like Metso can help you so you don’t need to take care of everything by yourself. Metso offers end-to-end services for rotary kilns, as well as for full pyro processing systems. Our services also cover the many heritage brands that are part of Metso, and we also service non-Metso equipment. With more than 100 years of experience covering numerous applications and business areas, you can count on Metso to keep your kiln turning.

Our kiln services

Spare parts supply

OEM parts are available for a variety of brands, all held to stringent quality standards

  • Reliable original parts that work with no fuss
  • Tried, tested, and available


Upgrades, retrofits, and repairs

A range of possibilities, from small tire crack repairs to shell section replacement to complete overhaul

  • Extend the life of your equipment
  • Achieve performance improvements: profitability, uptime, safety and sustainability


Inspection and alignment services

Regular maintenance is a core practice that should not be overlooked

  • A variety of standardized inspection packages
  • Comprehensive alignment and mechanical analysis services can be performed during normal operation

Training and seminars

An extensive array of training programs designed for real-world operations

  • We specialize in hands-on training for operators and maintenance personnel
  • We also offer on-site training and regional seminars



Brands and experience

Metso is home to many heritage kiln brands:

  • Allis-Chalmers
  • Allis Mineral Systems
  • Svedala
  • Boliden Allis
  • Kennedy Van Saun (KVS)
  • MPSI/Hardinge
  • Stansteel


Many application areas:

  • Iron ore
  • Cement
  • Lime
  • Pulp & paper
  • Coke
  • Lithium
  • Alumina
  • Waste incineration
Get the most out of your rotary kiln
With 100+ years of designing and servicing kilns, we've seen it all - and want to share our insights, this eBook covers it all.

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