Dryer Cylinder Maintenance
Maintenance, refurbishment and new dryer cylinder solutions for paper and board machines
Dryer cylinders are critical components in paper and board production. As steam-heated, pressure-containing components, their maintenance requires attention not only to mechanical condition and functional surfaces, but also to applicable pressure equipment requirements.
PR Rolls provides workshop maintenance and refurbishment of dryer cylinders for paper and board machines, taking the applicable pressure equipment requirements into account throughout the maintenance process.
Our services can cover the complete cylinder – from inspection and condition assessment to mechanical maintenance, grinding, surface restoration, coating and precision finishing.
When refurbishment is no longer the appropriate solution, PR Rolls can also provide new dryer cylinder solutions in cooperation with AP-Tela Oy. AP-Tela manufactures the new dryer cylinder in accordance with the applicable pressure equipment requirements, while PR Rolls provides the required functional coating and precision surface finishing.
This gives customers a complete approach to dryer cylinder lifecycle management – from maintaining and restoring existing cylinders to providing new coated cylinders when replacement is required.
Maintain. Restore. Recoat. Or replace with new. The appropriate solution is determined by the cylinder condition, production requirements and applicable safety requirements.
Complete Dryer Cylinder Maintenance
Restore the complete cylinder – not only the surface
A dryer cylinder is more than its outer surface.
Reliable and safe operation depends on the condition and interaction of the complete component, including its pressure-containing structure, mechanical parts, geometry and functional surface.
When a dryer cylinder arrives at the PR Rolls workshop, the maintenance scope is determined according to its actual condition and the applicable requirements for the component.
Depending on the cylinder and maintenance requirement, workshop services can include:
- Incoming inspection and condition assessment
- Review of relevant cylinder and maintenance information
- Dimensional and geometry measurements
- Mechanical inspection and maintenance
- Inspection of journals and mechanical interfaces
- Surface inspection
- Grinding and geometry restoration
- Removal of corrosion, wear and surface damage
- Coating and recoating
- Precision surface finishing
- Final inspection and verification
- Coordination of required pressure-equipment inspections and documentation where applicable
Because dryer cylinders are pressure-containing components, repairs or modifications that can affect pressure-retaining or other safety-critical parts require particular attention. The required procedures, documentation and inspections are determined according to the cylinder, scope of work and applicable pressure equipment requirements.
The objective is to return the dryer cylinder with the mechanical condition, geometry, functional surface and safety integrity required for continued operation.
When Does a Dryer Cylinder Require Maintenance?
Dryer cylinders operate continuously under demanding thermal, mechanical and process conditions.
Over time, wear, corrosion, mechanical deterioration and surface damage can affect the condition of the cylinder.
Maintenance or condition assessment should be considered when there are indications such as:
- Corrosion or rust
- Surface wear
- Scratches or grooves
- Mechanical damage
- Uneven surface condition
- Geometry deviations
- Worn or damaged coatings
- Journal or bearing-related wear
- Recurring surface problems
- Findings during scheduled inspections
- Damage or deterioration that may affect continued safe operation
Not every cylinder requires the same repair.
Inspection and measurement help determine whether the cylinder primarily requires mechanical maintenance, grinding, surface restoration, recoating or a combination of several operations.
Where findings concern pressure-retaining or safety-critical parts of the cylinder, the repair scope is assessed with the applicable pressure equipment requirements in mind.
Dryer Cylinder Inspection & Condition Assessment
Maintenance starts with understanding the actual condition
Before deciding how a dryer cylinder should be repaired, its actual condition should be evaluated.
PR Rolls can inspect and measure the cylinder to identify wear, damage and deviations that should be addressed during refurbishment.
Depending on the project, the assessment can consider the condition of the:
- Cylinder shell and surface
- Cylinder geometry
- Journals and mechanical interfaces
- Existing coating
- Areas affected by corrosion or wear
- Visible mechanical damage
- Other relevant cylinder components
Available information about the cylinder, previous maintenance and inspection history can also be taken into account when determining the appropriate maintenance scope.
This provides the basis for a condition-based maintenance strategy:
Inspect → Measure → Assess → Define requirements → Restore
For pressure equipment, traceability and knowledge of previous repairs and modifications are particularly important. Tukes highlights documentation of modifications and repairs as part of managing the condition and remaining service life of pressure equipment.
Dryer Cylinders as Pressure Equipment
Safety requirements throughout the cylinder lifecycle
Dryer cylinders typically operate with pressurised steam and must therefore be considered not only as rotating machine components but also in relation to applicable pressure equipment requirements.
Within the European Union, the Pressure Equipment Directive 2014/68/EU (PED) establishes requirements for the design, manufacture and conformity assessment of pressure equipment within its scope. PED applies to pressure equipment with a maximum allowable pressure PS greater than 0.5 bar.
National legislation also governs the safe use and inspection of pressure equipment. In Finland, Tukes emphasises safety throughout the pressure equipment lifecycle, from design and manufacturing to use, maintenance and servicing. Registered pressure equipment is also subject to statutory periodic inspections by approved inspection bodies.
PR Rolls takes these requirements into account when planning and carrying out dryer cylinder maintenance.
Where work can affect the pressure-retaining structure or other safety-critical characteristics, the required repair procedures, documentation, inspections and verification are determined according to the specific cylinder and applicable requirements.
Pressure equipment safety is therefore considered as part of the maintenance process – not as a separate consideration after the repair has been completed.
Mechanical Maintenance & Refurbishment
Address the complete dryer cylinder
Surface deterioration is often the most visible indication of dryer cylinder wear, but it may not be the only maintenance requirement.
Workshop refurbishment provides an opportunity to assess the mechanical condition of the complete component.
Depending on cylinder design and condition, PR Rolls can combine mechanical maintenance with grinding, surface restoration and coating within the same project.
Particular care is taken when maintenance involves components or structures that can influence pressure equipment safety.
A surface repair, for example, is fundamentally different from a repair or modification affecting a pressure-retaining structure. The latter requires the applicable pressure-equipment requirements and necessary inspection procedures to be considered before the cylinder returns to service.
Tukes specifically identifies maintenance and servicing as part of pressure-equipment lifecycle safety and emphasises that modifications and repairs should be carried out and documented appropriately.
The objective is therefore not simply to repair an individual defect.
The objective is to prepare the complete cylinder for safe and reliable continued operation.
Dryer Cylinder Grinding & Surface Restoration
Restore cylinder geometry and surface condition
A worn or damaged dryer cylinder surface may require grinding before the cylinder can return to production or receive a new functional coating.
Typical reasons for grinding include corrosion, surface wear, scratches, coating damage, uneven wear and geometry deviations.
Precision grinding removes damaged material in a controlled manner and restores the required cylinder geometry and surface condition.
Where recoating is required, grinding also creates the appropriate foundation for subsequent surface preparation and coating.
A typical restoration sequence can include:
Inspection → Measurement → Grinding → Surface preparation → Coating → Precision finishing → Verification
For dryer cylinders, material removal must also be considered in relation to the cylinder itself. The permissible scope of machining is therefore determined according to the cylinder condition, design information and applicable requirements.
The goal is not simply to make the cylinder smooth. It is to restore the required geometry and functional surface while maintaining the integrity of the component.
Dryer Cylinder Coating & Recoating
Create the functional surface required by the process
The dryer cylinder surface continuously interacts with the paper web, process contaminants and, depending on the position, the doctoring system.
Different dryer positions can therefore require different surface properties.
Depending on the application, important requirements can include:
- Wear resistance
- Corrosion resistance
- Paper release
- Reduced contamination
- Surface cleanliness
- Resistance to doctoring
- Surface durability
PR Rolls provides functional coating and recoating of dryer cylinders as part of workshop refurbishment.
For an existing coated cylinder, the condition of the current surface and underlying cylinder is evaluated. Where necessary, the worn surface can be removed and the geometry restored before a new functional coating is applied.
The coating solution is selected according to the dryer position, operating environment and dominant surface challenge.
The optimum surface for a release-critical cylinder may, for example, be different from the surface required for a cylinder exposed to hard doctoring and high mechanical wear.
More Than a Coating
Geometry, coating and final surface work together
A high-performance coating cannot compensate for incorrect cylinder geometry.
Likewise, coating material alone does not determine how the finished cylinder will perform.
PR Rolls therefore considers the complete functional surface:
Cylinder integrity → Correct geometry → Appropriate functional coating → Precision surface finishing
Depending on the application, doctoring conditions are also considered when selecting and finishing the surface.
This approach allows the cylinder to be restored according to what the surface actually needs to do in production rather than simply applying a standard coating.
Precision Finishing of Dryer Cylinders
Applying a coating is not necessarily the final stage of dryer cylinder restoration.
The completed surface must have the geometry, roughness and functional characteristics required by the application.
PR Rolls combines coating expertise with grinding and precision surface finishing, allowing both the coating and final functional surface to be controlled within the same workshop project.
This relationship can be summarised as:
Cylinder condition + Geometry + Functional coating + Final surface = Functional dryer cylinder
The objective is a finished cylinder prepared for reliable operation in its intended dryer position.
Repair, Recoat or Replace?
Make the decision based on actual cylinder condition
A worn dryer cylinder does not automatically need to be replaced.
Depending on its mechanical condition, geometry, pressure-containing structure and remaining repair possibilities, refurbishment may provide an appropriate way to extend its operating life.
PR Rolls evaluates the cylinder to determine whether the appropriate solution is:
Maintain → Grind → Restore → Recoat
or whether replacement with a new cylinder should be considered.
For pressure-containing components, this decision must consider more than surface condition alone. Safety, remaining component integrity, previous repairs and applicable pressure equipment requirements can all influence whether continued refurbishment is appropriate.
This condition-based approach helps avoid both premature replacement and repeated refurbishment of a cylinder that has reached the end of its practical service life.
The objective is to select a technically sound and safe solution for continued production.
New Dryer Cylinders
New cylinder solutions in cooperation with AP-Tela Oy
When an existing dryer cylinder is no longer suitable for continued refurbishment – or when a new cylinder is required for an investment, rebuild or replacement – PR Rolls can provide a new dryer cylinder solution in cooperation with AP-Tela Oy.
AP-Tela manufactures the new dryer cylinder, while PR Rolls provides the required functional coating and precision surface finishing.
AP-Tela manufactures welded steel dryer cylinders according to the European Pressure Equipment Directive (PED), providing an alternative to traditional cast dryer cylinders.
This combines pressure-equipment compliant cylinder manufacturing with PR Rolls' expertise in dryer cylinder surfaces, coatings and precision finishing.
A typical new cylinder delivery can include:
Cylinder manufacturing by AP-Tela Oy → Applicable conformity assessment and manufacturing requirements → Surface preparation → Functional coating by PR Rolls → Precision finishing → Final verification → Ready for installation
The coating and final surface are selected according to the intended dryer position and operating requirements.
This gives customers two complementary alternatives:
Existing cylinder:
Inspect → Assess → Maintain → Grind → Restore → Recoat → Verify → Continued production
New cylinder:
Design & manufacture → Pressure equipment requirements → Functional coating → Precision finishing → Verification → Installation
In both cases, the pressure-containing function of the dryer cylinder is taken into account.
Pressure Equipment Requirements for New Dryer Cylinders
For new dryer cylinders within the scope of PED, pressure equipment requirements are addressed from the design and manufacturing stages.
PED covers the design, manufacture and conformity assessment of pressure equipment within its scope and establishes essential safety requirements based on factors such as equipment type, pressure, volume and fluid. Depending on classification, conformity assessment may involve a notified body.
Through cooperation with AP-Tela, these requirements are considered as part of the new-cylinder manufacturing process, while PR Rolls provides the functional coating and final surface engineering.
This creates a clear division of expertise:
AP-Tela → Dryer cylinder manufacturing and applicable pressure equipment requirements
PR Rolls → Functional coating, grinding and precision surface finishing
Together, the objective is to provide a new dryer cylinder that meets both its pressure-containing requirements and its functional requirements in the paper or board machine.
New Coated Dryer Cylinders
Engineer the functional surface before production begins
Functional coating does not need to begin only after a cylinder has become worn.
A newly manufactured dryer cylinder can be provided with a functional surface selected for its intended operating position from the beginning.
Depending on the application, this can address requirements related to paper release, contamination, wear, corrosion, doctoring and surface durability.
PR Rolls' ability to coat and precision-finish new cylinders means that surface engineering can be incorporated into the component before it enters production.
When the cylinder later requires maintenance, the same understanding of its functional surface can be applied to grinding, recoating and refurbishment.
This creates a lifecycle approach rather than treating new-cylinder manufacturing, functional coating and future maintenance as unrelated activities.
Workshop Maintenance or On-Site Dryer Cylinder Service?
PR Rolls provides both workshop and on-site services for dryer cylinders.
The appropriate approach depends on cylinder size, condition, required maintenance scope, transportation possibilities and available shutdown time.
Workshop Dryer Cylinder Maintenance
Workshop maintenance can be particularly suitable when the cylinder has already been removed from the machine, extensive mechanical maintenance is required or several maintenance operations need to be combined.
It also provides an appropriate environment for coordinating condition assessment, mechanical work, grinding, coating and finishing.
Where the planned work affects pressure-retaining or other safety-critical parts, the applicable pressure equipment requirements and required inspections are incorporated into the maintenance plan.
On-Site Dryer Cylinder Services
For large cylinders that are difficult or uneconomical to remove and transport, PR Rolls provides specialised on-site dryer cylinder grinding and coating directly at paper and board mills.
On-site restoration can reduce dismantling, heavy lifting, transportation and reinstallation requirements.
The same fundamental principle applies whether the work is carried out in the workshop or at the mill:
The scope of work must respect both the functional requirements of the cylinder and the requirements applicable to the pressure-containing component.
Dryer Cylinder Lifecycle Management
Safety and performance from new cylinder to refurbishment
A dryer cylinder can remain in production for many years, and its maintenance requirements change throughout its operating life.
For pressure equipment, lifecycle management is particularly important. Tukes describes pressure-equipment safety as covering design, manufacturing, use, maintenance and servicing, while registered pressure equipment is subject to statutory periodic inspections.
PR Rolls therefore approaches dryer cylinder maintenance from both a production-performance and lifecycle perspective.
A typical lifecycle can include:
New cylinder → Functional coating → Production → Periodic inspection → Condition assessment → Maintenance → Grinding → Recoating → Continued production
When continued refurbishment is no longer appropriate:
Condition assessment → Replacement decision → New cylinder → Functional coating → Production
Throughout this lifecycle, relevant maintenance, repair and modification information should be documented so that the cylinder's condition and continued suitability can be evaluated.
Together with AP-Tela, PR Rolls can therefore support both sides of the lifecycle decision:
Restore the existing cylinder when appropriate – or provide a new coated cylinder when replacement is required.
Why Choose PR Rolls for Dryer Cylinder Maintenance?
Dryer cylinder maintenance requires an understanding of both industrial surface engineering and the responsibilities associated with pressure-containing equipment.
PR Rolls combines:
Inspection + Mechanical maintenance + Grinding + Surface restoration + Functional coating + Precision finishing
with consideration of the applicable pressure equipment requirements throughout the maintenance process.
For large installed cylinders, these capabilities are complemented by specialised on-site grinding and coating services.
When refurbishment is no longer the appropriate solution, cooperation with AP-Tela enables customers to move from restoring an existing cylinder to obtaining a newly manufactured dryer cylinder with a functional surface engineered by PR Rolls.
This provides a complete lifecycle approach:
Maintain when possible. Restore when appropriate. Recoat when the surface needs renewal. Replace with new when required.
And throughout the process:
Protect the integrity and safety of the pressure-containing component.
Frequently Asked Questions About Dryer Cylinder Maintenance
Are dryer cylinders pressure equipment?
Steam-heated dryer cylinders are pressure-containing components and may fall within applicable pressure equipment legislation. In the EU, PED 2014/68/EU applies to pressure equipment within its scope with a maximum allowable pressure PS greater than 0.5 bar. The exact requirements depend on the specific equipment and its classification.
Does PR Rolls take pressure equipment requirements into account during repairs?
Yes. PR Rolls considers the applicable pressure equipment requirements when defining and carrying out dryer cylinder maintenance. Where work affects pressure-retaining or other safety-critical parts, the required procedures, documentation, inspections and verification are determined according to the specific cylinder and applicable requirements.
Can any damage to a dryer cylinder simply be repaired by welding?
No. Repairs affecting pressure-retaining structures require appropriate assessment before work is carried out. The applicable requirements, repair procedure, documentation and required inspection depend on the cylinder and scope of the repair. Tukes emphasises that pressure-equipment repairs and modifications should be appropriately carried out and documented.
What does dryer cylinder maintenance include?
Depending on cylinder condition, maintenance can include inspection, measurement, mechanical maintenance, grinding, surface restoration, coating, precision finishing and final verification. Where applicable, pressure equipment requirements and required inspections are incorporated into the maintenance scope.
Can a worn dryer cylinder be refurbished instead of replaced?
In many cases, yes. The decision depends on the mechanical and structural condition of the cylinder, geometry, surface condition and applicable requirements. Inspection and condition assessment are used to determine whether continued refurbishment is appropriate.
Does PR Rolls provide new dryer cylinders?
Yes. PR Rolls cooperates with AP-Tela Oy for new dryer cylinder solutions. AP-Tela manufactures the cylinder, while PR Rolls provides the required functional coating and precision surface finishing. AP-Tela states that its welded steel dryer cylinders are manufactured according to PED.
Can PR Rolls grind and recoat dryer cylinders?
Yes. Grinding, surface restoration, coating and precision finishing can be combined as part of a dryer cylinder refurbishment project. The permissible maintenance scope is determined with consideration of cylinder condition and applicable requirements.
Can PR Rolls service dryer cylinders directly at the mill?
Yes. For cylinders that are difficult or uneconomical to remove, PR Rolls provides specialised on-site dryer cylinder grinding and coating services.
Maintain, Restore or Replace Your Dryer Cylinder
Dryer cylinder maintenance requires more than restoring a worn surface.
As a pressure-containing component, the cylinder must be considered from the perspectives of mechanical condition, structural integrity, geometry, functional surface and applicable safety requirements.
PR Rolls combines inspection, maintenance, grinding, surface restoration, functional coating and precision finishing while taking the applicable pressure equipment requirements into account.
When replacement is the appropriate solution, PR Rolls and AP-Tela can provide a new manufactured and functionally coated dryer cylinder, with pressure equipment requirements considered as part of the manufacturing process.
This creates a complete lifecycle solution:
Existing cylinder → Inspect → Maintain → Restore → Recoat → Verify → Continue production
or
Replacement required → New compliant cylinder → Functional coating → Precision finishing → Installation → Production
Contact PR Rolls to discuss your dryer cylinder and determine the appropriate maintenance, refurbishment or replacement solution.