ASTM A335 P11 HFW Helical Serrated Finned Tube With Gr.11 Fins For Refinary
HFW Helical Serrated Finned Tube is a specific type of finned tube used in heat exchange applications. The "HFW" stands for High Frequency Welded, which is the process used to attach the fins to the tube. This welding technique uses high-frequency electrical currents to produce heat, thereby welding the fins onto the surface of the tube to ensure a strong bond.
The use of HFW Helical Serrated Finned Tubes can significantly improve the performance of a heat exchanger by increasing the efficiency of heat transfer, leading to better thermal management and potential energy savings in industrial processes. They are particularly useful in applications where the operating conditions lead to fouling, as the serrations can help minimize the build-up of deposits on the tube surfaces.
Here's a breakdown of the key components:
1. Helical: This refers to the shape and arrangement of the fins. The fins are wound in a helical or spiral pattern around the exterior of the tube. This configuration can improve heat transfer efficiency because of the increased surface area and enhanced turbulence it creates as fluids flow over the fins.
2. Serrated: The fins are notched or serrated, meaning they have a jagged edge rather than a smooth one. This design increases the surface area even further and can contribute to turbulent flow as well. The serration also allows for more flexibility in the fin, which can help accommodate thermal expansion and contraction, potentially reducing stress and wear on the tube.
3. Finned Tube: A finned tube is a tube that has fins attached to its surface. The primary purpose of the fins is to increase the surface area of the tube, which enables more efficient heat transfer between the tube and the fluid flowing over it.
4. Gr.11 Fins
The fins are made from Grade 11 material, matching the tube's base alloy (ASTM A335 P11) to ensure compatibility in high-temperature environments and prevent galvanic corrosion.
5. Chemical Composition and Mechanical Properties of ASTM A335 P11
The chemical composition (in weight %) is specified by ASTM A335 and ASME SA335 standards:
| Element | Composition (%) |
| Carbon (C) | 0.05 – 0.15 |
| Manganese (Mn) | 0.30 – 0.60 |
| Phosphorus (P) (max) | 0.025 |
| Sulfur (S) (max) | 0.025 |
| Silicon (Si) | 0.50 – 1.00 |
| Chromium (Cr) | 1.00 – 1.50 |
| Molybdenum (Mo) | 0.44 – 0.65 |
| Nickel (Ni) (max)* | 0.25 |
| Vanadium (V) (max)* | 0.08 |
| Residuals (Cu, Nb, etc.) | Trace |
Note: Some standards allow minor residual elements, but they are typically restricted to avoid adverse effects on weldability and creep resistance.
Mechanical Properties of ASTM A335 P11
Per ASTM A335, the mechanical properties in the normalized & tempered condition are:
| Property | Value |
| Tensile Strength (min) | 415 MPa (60,000 psi) |
| Yield Strength (min) | 205 MPa (30,000 psi) |
| Elongation (min, % in 50mm) | 30% |
| Hardness (max, Brinell HBW) | 179 HBW (for seamless tubes) |
Additional Notes of Mechanical Properties of ASTM A335 P11:
- Heat Treatment: P11 is typically supplied in normalized + tempered condition to optimize strength and toughness.
- High-Temperature Performance:
- Retains good creep resistance up to ~600°C (1,112°F).
- Oxidation resistance due to chromium content.
- Impact Testing: Often required for low-temperature applications (e.g., Charpy V-notch per ASTM A370).
Comparison with Other Grades
- P11 is part of the Cr-Mo alloy family. Key differences:
- P5 (5Cr-0.5Mo): Higher Cr for better oxidation resistance.
- P9 (9Cr-1Mo): Enhanced creep strength.
- P22 (2.25Cr-1Mo): Higher strength than P11.
Common Applications of Material ASTM A335 P11
- Power plant boilers & superheaters
- Petrochemical refining tubes
- High-pressure heat exchangers
The applications of ASTM A335 P11 HFW (High-Frequency Welded) Helical Serrated Finned Tube with Grade 11 Fins
1. Power Plants
- Used in boilers, superheaters, and economizers to enhance heat transfer efficiency in steam generation systems.
- Suitable for coal-fired, gas-fired, and waste heat recovery power plants.
2. Petrochemical & Refineries
- Employed in fired heaters, reformers, and cracking furnaces where high-temperature resistance is required.
- Handles corrosive and high-pressure fluids in oil refining processes.
3. Chemical Processing
- Used in heat recovery systems, reactors, and distillation columns where efficient heat exchange is critical.
4. Waste Heat Recovery Systems
- Recovers heat from exhaust gases in industrial furnaces, reducing energy waste.
5. HVAC & Industrial Heating
- Applied in air heaters, duct heaters, and thermal fluid systems for large-scale industrial heating.
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ASTM A335 P11 HFW Helical Serrated Finned Tube With Gr.11 Fins For Refinary Images
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