ASTM A335 P9 High Frequency Welding Solid Finned Tube with Alloy
Fins For Refinary
ASTM A335 P9 High Frequency Welding (HFW) Solid Finned Tube with
Alloy Fins for Refinery is a specialized type of heat exchanger
tube designed for high-temperature and corrosive environments,
commonly used in refineries, petrochemical plants, and power
generation. Here's a breakdown of its key features:
1. Base Tube Material:
(1) Chemical Composition of ASTM A335 P9
The composition complies with ASTM A335/A335M standards.
| Element | Composition (% Weight, Max unless specified) |
| Carbon (C) | 0.15 max (typically 0.05–0.15) |
| Manganese (Mn) | 0.30–0.60 |
| Phosphorus (P) | 0.025 max |
| Sulfur (S) | 0.025 max |
| Silicon (Si) | 0.50–1.00 |
| Chromium (Cr) | 8.00–10.00 |
| Molybdenum (Mo) | 0.90–1.10 |
| Nickel (Ni) | 0.40 max (residual) |
| Vanadium (V) | 0.18–0.25 (optional for enhanced creep resistance) |
Key Notes:
9% Cr-1% Mo composition provides oxidation & sulfidation resistance
at high temps (up to 650°C / 1200°F).
Low carbon reduces weldability issues (pre-heat & post-weld heat
treatment required).
Vanadium (V) may be added in modified grades (e.g., P9b) for better
creep strength.
(2) Mechanical Properties of ASTM A335 P9
Per ASTM A335, the seamless pipe must meet the following
requirements:
| Property | Value |
| Tensile Strength (MPa) | ≥ 415 (60 ksi) |
| Yield Strength (MPa) | ≥ 205 (30 ksi) |
| Elongation (% in 50mm) | ≥ 30 (varies with wall thickness) |
| Hardness (Brinell HB) | ≤ 179 (typically ~150–170 HB) |
Additional Notes:
Heat Treatment: P9 pipes are supplied in normalized & tempered
condition for optimal strength and toughness.
High-Temperature Performance: Retains strength at up to 600–650°C
(refinery furnace tubes, boilers).
Impact Testing: Often required for low-temperature service (e.g.,
Charpy V-notch per ASTM A370).
(3) Comparison with Similar Grades
| Grade | Cr (%) | Mo (%) | Max Temp (°C) | Key Use |
| P5 | 4–6 | 0.45–0.65 | 550 | Less corrosive environments |
| P9 | 8–10 | 0.9–1.1 | 650 | Refineries, high-sulfur service |
| P11 | 1.0–1.5 | 0.44–0.65 | 550 | Lower-cost alternative |
2. High-Frequency Welding (HFW) Process
The fins are welded to the base tube using high-frequency induction
welding, ensuring a strong metallurgical bond.
Provides better heat transfer efficiency compared to embedded or
wrapped fins.
Suitable for high-stress environments due to superior joint
integrity.
3. Solid Finned Design with Alloy Fins
Fins are made from an alloy (often stainless steel or nickel-based
alloys) to enhance corrosion and oxidation resistance.
Solid fins (as opposed to serrated or studded) provide better
durability in harsh refinery conditions.
Increases heat transfer surface area, improving thermal efficiency.
4. Key Advantages of ASTM A335 P9 Solid Finned Tube
- High thermal conductivity due to alloy fins.
- Long service life in corrosive refinery environments.
- Strong weld integrity prevents fin detachment under thermal
cycling.
The ASTM A335 P9 High Frequency Welding (HFW) Solid Finned Tube
with Alloy Fins is designed for high-temperature, high-pressure,
and corrosive environments, making it ideal for demanding
applications in refineries, petrochemical plants, and power
generation. Below are its key applications:
1. Refinery & Petrochemical Applications
a) Fired Heaters & Process Furnaces
Used in crude oil heaters, reformers, and hydrocracking furnaces
where temperatures exceed 600°C (1112°F).
Resists sulfidation (H₂S attack) and oxidation due to 9% Cr-1% Mo
alloy base + corrosion-resistant alloy fins (e.g., SS 304/321,
Incoloy).
b) Waste Heat Recovery Systems
Recovers heat from flue gases in refinery units (e.g., catalytic
crackers, cokers).
Alloy fins (e.g., Inconel 625) prevent degradation from acidic
condensates.
c) Hydroprocessing Units
Hydrogen-rich environments (e.g., hydrodesulfurization - HDS,
hydrocracking).
HFW fins ensure no fin detachment under thermal cycling.
2. Power Generation & Boilers
a) Boiler Superheaters & Reheaters
Withstands steam temperatures up to 650°C (1200°F).
Alloy fins (e.g., SS 347) resist coal ash corrosion in coal-fired
plants.
b) Heat Recovery Steam Generators (HRSGs)
Used in combined-cycle power plants for exhaust gas heat recovery.
HFW welding prevents fin failure under rapid thermal transients.
3. Chemical & Fertilizer Industry
a) Ammonia & Urea Plants
High-pressure synthesis gas heaters (resists hydrogen
embrittlement).
Alloy fins protect against nitriding attack.
b) Sulfuric Acid & Olefin Plants
Corrosion-resistant fins (e.g., Hastelloy) handle acidic and
chlorinated environments.
