ASTM A312 TP304H Serrated Finned Tubes for HRSG Manufacturers
Product Overview
ASTM A312 TP304H serrated finned tubes are high-temperature stainless-steel heat-transfer tubes developed for Heat Recovery Steam Generators (HRSGs), waste heat recovery boilers, industrial heat exchangers, and other demanding thermal systems.
TP304H is an austenitic stainless-steel grade with higher carbon content than standard TP304. This composition is intended for elevated-temperature service and provides a combination of high-temperature strength, oxidation resistance, corrosion resistance, and good weldability when properly processed.
The serrated fin design increases the external heat-transfer surface while creating gas-side turbulence. This enables efficient recovery of heat from hot exhaust gas without requiring an excessively large heat-transfer bundle. For HRSG manufacturers, these characteristics make TP304H serrated finned tubes suitable for applications where thermal efficiency, durability, compact equipment design, and resistance to elevated-temperature oxidation are important.
Why TP304H Serrated Finned Tubes Are Used in HRSGs
In an HRSG, hot exhaust gas from a gas turbine passes across heat-transfer tube banks. The tube-side water or steam absorbs heat from the exhaust gas.
A conventional bare tube has limited external surface area. Serrated fins significantly increase the effective gas-side heat-transfer area, allowing the HRSG designer to obtain the required thermal duty with a more compact tube arrangement.
ASTM A312 TP304H is particularly attractive for selected high-temperature sections because its stainless-steel construction provides better resistance to oxidation and corrosion than conventional carbon-steel finned tubes.
Typical applications include:
- HRSG heat-transfer sections
- Waste heat recovery boilers
- Gas turbine exhaust heat recovery
- High-temperature economizer sections
- Industrial heat recovery units
- Gas-to-water heat exchangers
- Gas-to-steam heat exchangers
- Petrochemical heat recovery equipment
- Refinery process heat recovery
- High-temperature industrial boilers
Product Construction
Our serrated finned tubes can be manufactured using a high-frequency resistance welding process, in which the continuous fin strip is helically wound around the base tube and welded to the tube surface.
The fin is then mechanically formed into a serrated or segmented configuration.
This construction provides:
- Increased external heat-transfer area
- Improved gas-side turbulence
- Strong fin-to-tube attachment
- Good resistance to thermal cycling
- Efficient heat transfer in gas-side applications
- Reduced risk of fin separation during service
- Flexible tube-bank configuration
For HRSG applications, the exact tube, fin, pitch, height and thickness should be selected according to gas temperature, steam/water conditions, pressure drop, corrosion environment and required heat-transfer duty.
Common Size Range
The dimensions can be customized according to the HRSG manufacturer's thermal and mechanical design.
Base Tube
| Parameter |
Common Range |
| Outside Diameter |
25–63.5 mm |
| Wall Thickness |
2.0–6.0 mm |
| Tube Length |
3,000–15,000 mm |
| Typical tube length |
6,000–12,000 mm |
Serrated Fin
| Parameter |
Common Range |
| Fin Height |
8–25 mm |
| Fin Thickness |
0.8–2.5 mm |
| Fin Pitch |
2.5–8 mm |
| Fin Density |
125–400 fins/m |
| Fin Material |
Stainless steel or compatible alloy |
| Fin Type |
Serrated / segmented spiral fin |
These are typical manufacturing ranges rather than fixed ASTM dimensional requirements. Final dimensions can be produced according to the customer's HRSG design drawings and heat-transfer calculations.
ASTM A312 TP304H Chemical Composition
The following values represent the commonly specified chemical requirements for ASTM A312 TP304H. The applicable edition of the purchasing specification should always govern the final material certificate.
| Element |
Typical Requirement, wt.% |
| Carbon (C) |
0.04–0.10 |
| Manganese (Mn) |
≤ 2.00 |
| Silicon (Si) |
≤ 1.00 |
| Phosphorus (P) |
≤ 0.045 |
| Sulfur (S) |
≤ 0.030 |
| Chromium (Cr) |
18.0–20.0 |
| Nickel (Ni) |
8.0–11.0 |
| Iron (Fe) |
Balance |
The relatively high chromium and nickel contents provide the austenitic stainless-steel structure and corrosion/oxidation resistance associated with the 304 family.
Mechanical Properties
Typical minimum mechanical requirements for ASTM A312 TP304H include:
| Property |
Requirement |
| Tensile Strength |
≥ 515 MPa |
| Yield Strength, 0.2% offset |
≥ 205 MPa |
| Elongation |
≥ 35% |
Actual properties should be confirmed against the applicable ASTM A312/A312M edition and the purchaser's project specification.
For HRSG service, mechanical-property requirements should be considered together with design temperature, pressure, creep exposure, thermal cycling and corrosion conditions.
Manufacturing Process
Our TP304H serrated finned tubes can be manufactured through the following controlled process:
1. Base Tube Preparation
ASTM A312 TP304H stainless-steel tubes are inspected for dimensional accuracy, surface condition and material identification.
2. Fin Strip Preparation
The stainless-steel fin strip is slit to the specified width and thickness and prepared for continuous welding.
3. High-Frequency Welding
The fin strip is helically wound around the tube while high-frequency electrical energy produces localized heating at the fin-to-tube interface. Pressure is applied to create a continuous metallurgical bond.
4. Serration
The continuous spiral fin is mechanically serrated to create the required segmented profile.
5. Fin Forming and Calibration
The fin geometry, pitch, height and alignment are controlled to meet the customer's specifications.
6. Finishing
Tube ends are cleaned and finished according to the requirements of the HRSG manufacturer.
7. Inspection
Dimensional, visual, material and weld/attachment inspections are performed before final release.
Testing and Inspection
Quality control is particularly important for HRSG finned tubes because they operate under continuous thermal loading and repeated temperature changes.
Depending on the purchase specification, inspection may include:
Chemical Analysis
Positive Material Identification (PMI) or laboratory chemical analysis can be performed to verify the TP304H material grade.
Tensile Testing
Tensile testing verifies yield strength, tensile strength and elongation.
Hydrostatic Testing
The base tube can be hydrostatically tested according to the applicable ASTM A312 requirements and purchaser specifications.
Eddy Current Testing
Eddy current examination can detect certain surface and near-surface discontinuities in the tube.
Ultrasonic Testing
UT may be specified for tube-wall or weld-area examination depending on the project requirements.
Fin-to-Tube Bond Inspection
The fin attachment is inspected for continuity, bonding quality and potential areas of incomplete welding.
Visual Inspection
The tube surface, fin geometry, weld appearance and tube ends are visually inspected.
Dimensional Inspection
Typical measurements include:
- Tube outside diameter
- Wall thickness
- Tube length
- Fin height
- Fin thickness
- Fin pitch
- Fin density
- Fin-to-tube alignment
- Overall finned length
Advantages for HRSG Manufacturers
High Heat-Transfer Surface Area
Serrated fins substantially increase the external heat-transfer area compared with bare tubes.
Enhanced Gas-Side Heat Transfer
The interrupted fin geometry promotes turbulence and improves gas-side heat transfer.
Stainless-Steel Corrosion Resistance
TP304H offers significantly greater resistance to many corrosive and oxidizing environments than ordinary carbon-steel tube materials.
Elevated-Temperature Capability
TP304H is intended for elevated-temperature applications where the material must maintain useful mechanical properties.
Strong Fin Attachment
High-frequency welded construction provides a continuous and mechanically robust fin-to-tube connection.
Compact HRSG Design
Higher heat-transfer area can help engineers achieve required thermal performance within a compact heat-transfer surface.
Suitable for Thermal Cycling
A properly designed and manufactured welded fin structure can withstand the repeated heating and cooling associated with HRSG operation.
Applications
ASTM A312 TP304H serrated finned tubes are primarily designed for:
- Heat Recovery Steam Generators (HRSGs)
- Combined-cycle power plants
- Waste heat recovery boilers
- Gas turbine exhaust systems
- Industrial cogeneration systems
- Process heat recovery
- Refinery heat recovery
- Petrochemical plants
- Chemical processing facilities
- High-temperature gas heat exchangers
- Industrial boilers
- Energy recovery systems
Recommended HRSG Supply Configuration
For HRSG manufacturers, we can manufacture serrated finned tubes according to project-specific requirements, including:
Base tube: ASTM A312 TP304H
Fin type: Serrated spiral fin
Fin attachment: High-frequency welded
Fin material: Stainless steel / project-specified alloy
Tube length: Customer specified
Fin pitch: Customer specified
Fin height: Customer specified
Fin thickness: Customer specified
Inspection: According to ASTM, ASME and purchaser requirements
Documentation: Material Test Certificate, dimensional inspection report and applicable NDT/testing records
The final tube and fin dimensions should always be established from the HRSG thermal design, mechanical design and applicable project specification, rather than selecting dimensions solely from a standard size table.
Quality Assurance
For HRSG applications, each production batch can be supplied with traceability documentation covering:
- Heat number
- Material grade
- Chemical composition
- Mechanical test results
- Tube dimensions
- Fin dimensions
- Welding/fin attachment inspection
- NDT results where specified
- Hydrostatic test results where specified
- Visual inspection
- Final inspection records
- Material Test Certificate (MTC)
This traceability helps HRSG manufacturers integrate the tubes into their quality-control and pressure-equipment documentation systems.
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