Bimetallic Extruded Finned Tubes for Timber Drying Kilns
Engineered Heat Transfer Solutions for High-Efficiency Timber Kiln Applications
Our bimetallic extruded finned tubes are specifically designed for demanding timber drying kiln environments where durability, corrosion resistance, and superior heat transfer performance are essential. Combining the mechanical strength and corrosion resistance of EN 10217-7 1.4301 stainless steel base tubes with the exceptional thermal conductivity of aluminum fins, these finned tubes provide reliable operation and extended service life under continuous industrial drying conditions.
The extrusion manufacturing process creates a permanent mechanical bond between the aluminum fin sleeve and the stainless steel core tube. Unlike wound or bonded fin constructions, extruded fins offer enhanced structural integrity and excellent resistance to vibration, thermal cycling, and mechanical damage, making them an ideal choice for wood seasoning and timber drying systems.
Product Features
- High thermal efficiency for accelerated timber drying cycles
- Excellent corrosion resistance in humid kiln environments
- Strong mechanical bond achieved through extrusion technology
- Superior fin durability against cleaning and handling damage
- Uniform heat distribution across the heat exchanger surface
- Reduced maintenance requirements and longer operating life
- Suitable for steam, hot water, thermal oil, and low-pressure heating systems
- Customizable dimensions to suit various kiln designs
Construction Details
Base Tube Material
- Material Standard: EN 10217-7
- Grade: 1.4301 Stainless Steel
- Equivalent Grades:
- AISI 304
- UNS S30400
- X5CrNi18-10
Fin Material
- Material: Industrial-grade Aluminum
- Typical Alloy: Aluminum 1050A or equivalent
- Purity: ≥99.5% Al
- Excellent thermal conductivity for efficient heat transfer.
Manufacturing Process
A seamless aluminum sleeve is pressure-extruded over the stainless steel tube using specialized finning equipment. During the extrusion process, the aluminum is plastically deformed to form continuous integral fins while tightly compressing onto the base tube surface.
This process ensures:
- Full circumferential contact
- Minimal thermal contact resistance
- High pull-out strength
- Long-term operating stability
Standard Size Range
The following dimensions represent our typical production capability. Customized dimensions are available upon request.
| Parameter |
Standard Range |
| Base Tube Outside Diameter |
19.05 mm to 50.80 mm |
| Base Tube Wall Thickness |
1.20 mm to 3.00 mm |
| Finned Outside Diameter |
38 mm to 82 mm |
| Fin Height |
8 mm to 16 mm |
| Fin Thickness |
0.30 mm to 0.50 mm |
| Fin Density |
8 to 13 fins per inch |
| Tube Length |
Up to 18,000 mm |
| Maximum Operating Temperature |
300°C |
| Maximum Design Pressure |
According to base tube specification |
Typical kiln heater applications commonly utilize:
- 25.4 mm * 57 mm finned tubes
- 31.75 mm * 57 mm finned tubes
- 38.1 mm * 70 mm finned tubes
Chemical Composition
EN 10217-7 Grade 1.4301 Stainless Steel (wt.%)
| Element |
Content (%) |
| Carbon (C) |
≤ 0.07 |
| Silicon (Si) |
≤ 1.00 |
| Manganese (Mn) |
≤ 2.00 |
| Phosphorus (P) |
≤ 0.045 |
| Sulfur (S) |
≤ 0.015 |
| Chromium (Cr) |
17.5 – 19.5 |
| Nickel (Ni) |
8.0 – 10.5 |
| Nitrogen (N) |
≤ 0.11 |
Aluminum Fin Material (Typical 1050A)
| Element |
Content (%) |
| Aluminum (Al) |
≥ 99.50 |
| Iron (Fe) |
≤ 0.40 |
| Silicon (Si) |
≤ 0.25 |
| Copper (Cu) |
≤ 0.05 |
| Manganese (Mn) |
≤ 0.05 |
| Magnesium (Mg) |
≤ 0.05 |
| Zinc (Zn) |
≤ 0.07 |
Mechanical Properties
EN 10217-7 Grade 1.4301 Base Tube
| Property |
Typical Value |
| Tensile Strength (Rm) |
500 to 700 MPa |
| Yield Strength (Rp0.2) |
≥ 190 MPa |
| Elongation (A) |
≥ 35% |
| Hardness |
≤ 215 HB |
| Impact Resistance |
Excellent |
Aluminum Fin Material
| Property |
Typical Value |
| Tensile Strength |
65 to 95 MPa |
| Yield Strength |
20 to 30 MPa |
| Elongation |
≥ 25% |
| Thermal Conductivity |
Approximately 220 W/m·K |
Inspection and Testing
To ensure consistent quality and dependable field performance, every production batch undergoes comprehensive inspection procedures.
Dimensional Inspection
- Base tube outside diameter verification
- Wall thickness measurement
- Fin height inspection
- Fin pitch verification
- Finned outside diameter measurement
- Length tolerance confirmation
Hydrostatic Testing
Base tubes are hydrostatically tested in accordance with applicable EN requirements to verify pressure integrity before finning operations.
Eddy Current Examination
Non-destructive eddy current testing may be conducted to identify potential surface or subsurface discontinuities.
Air Leakage Test
Completed finned tubes can be subjected to pneumatic leak testing upon customer request.
Fin Bond Integrity Test
Mechanical adhesion between the aluminum fins and stainless steel tube is verified through pull-off and deformation evaluations.
Visual Examination
- Fin continuity
- Surface defects
- Mechanical damage
- Burr formation
- End finishing quality
Material Traceability
Full traceability documentation is maintained throughout production, including:
- Raw material certificates
- Heat numbers
- Inspection reports
- Test records
Third-party inspections by organizations such as SGS, TÜV, BV, or customer-appointed representatives can also be arranged.
Applications
These bimetallic extruded finned tubes are widely used in:
- Timber drying kilns
- Wood seasoning chambers
- Biomass-fired kiln heating systems
- Steam-heated drying installations
- Hot water kiln heaters
- Industrial lumber processing plants
- Agricultural drying equipment
Advantages in Timber Drying Operations
Efficient heat transfer directly influences drying quality, energy consumption, and production throughput. Our bimetallic extruded finned tubes maximize heat exchange efficiency while maintaining excellent resistance to corrosion and mechanical wear.
The result is:
- Faster drying cycles
- Improved temperature uniformity
- Reduced fuel consumption
- Lower maintenance costs
- Extended equipment lifespan
- Increased operational reliability
For kiln manufacturers, maintenance contractors, and wood processing facilities seeking long-term performance, these finned tubes provide a robust and cost-effective heating solution engineered for demanding industrial service.
