Where is SA387 Grade 22 Class 1 commonly used?
SA387 Grade 22 Class 1 is commonly used in the construction of critical welded pressure vessels and components that operate under high temperature, high pressure, and in corrosive or hydrogen-rich environments, primarily within the energy and petrochemical sectors. Its specific annealed (softened) condition makes it the preferred choice when complex fabrication and severe forming are required during manufacturing.
1. Petroleum Refining & Petrochemical Industry (Most Common Application)
This is the core market for Grade 22 Class 1 due to its excellent resistance to High-Temperature Hydrogen Attack (HTHA).
Hydroprocessing Units:
Hydrocracker Reactors & Separators: The flagship application. These vessels process heavy oils under extreme hydrogen pressure (up to 3,000 psi) and temperatures (700°F-850°F / 370°C-450°C). Grade 22's 2.25Cr-1Mo composition is specifically designed to resist hydrogen embrittlement and decarburization.
Hydrotreater Reactors: For desulfurization and denitrification.
Catalytic Reforming Units: Reactors and heat exchangers.
High-Temperature, High-Pressure (HTHP) Heat Exchangers: Transferring heat between process streams in severe service.
2. Power Generation (Fossil & Nuclear)
Fossil Fuel Plants: High-pressure boiler components, steam drums, and headers that operate at superheated steam conditions.
Nuclear Power Plants: Certain primary and secondary system components requiring high integrity and radiation resistance.
3. Chemical Processing
High-Pressure Reactors for synthesis processes (e.g., ammonia, methanol).
Pressure Vessels exposed to aggressive chemistries at elevated temperatures.
Why Choose CLASS 1 Specifically? The Fabrication Driver
Within these applications, engineers specify Class 1 (Annealed) over the stronger Class 2 (Normalized & Tempered) for specific fabrication advantages:
| Component Type | Reason for Choosing Class 1 (Annealed) |
|---|---|
| Heavy, Dished & Hemispherical Heads | The superior ductility allows for severe cold or hot forming into complex shapes (e.g., reactor heads) without cracking. |
| Thick-Walled Shells with Tight Radii | Easier to roll and bend during cylindrical shell fabrication. |
| Complex, Integral Components | Better suited for heavy machining and forming of nozzles, flanges, and other attachments from plate material. |
| Vessels with Extensive Welding & Repair | The softer, more uniform annealed structure can be more forgiving during weld repair procedures. |
The Engineering Trade-off: The vessel designer accepts lower as-delivered strength in exchange for easier, safer fabrication of complex parts. The final strength and creep resistance are then achieved through the mandatory Post-Weld Heat Treatment (PWHT) of the completed vessel, bringing the Class 1 material's performance in line with service requirements.
Key Material Selection Criteria for These Applications:
Temperature Range: Ideal for continuous metal temperatures from ~500°F to 1050°F (260°C to 565°C).
Environment: Essential for hydrogen partial pressure service per API RP 941 (Nelson Curve) guidelines.
Pressure: Used for high-pressure design, where its strength after PWHT allows for thick-section containment.
In summary
you will find SA387 Grade 22 Class 1 plates in the most critical, thick-walled reactors and exchangers in an oil refinery or a chemical plant, particularly where the component's shape is too complex to form from the harder Class 2 material. It is the "manufacturer-friendly" version of the high-performance 2.25Cr-1Mo alloy.
What is SA387 Grade 22 Class 1?
SA387 Grade 22 Class 1 is an annealed chromium-molybdenum alloy steel plate designed for high-temperature pressure vessel service, with a composition of 2.25% Cr and 1% Mo to resist oxidation and hydrogen attack in refinery and power plant applications.
What are the mechanical properties of SA387 Grade 22 Class 1?
In its annealed condition, SA387 Grade 22 Class 1 typically has a tensile strength of 415-585 MPa (60-85 ksi), a minimum yield strength of 205 MPa (30 ksi), and high ductility, making it suitable for severe forming before final heat treatment.
Where is SA387 Grade 22 Class 1 commonly used?
It is widely used in hydroprocessing reactors, hydrocrackers, heat exchangers, and high-temperature pressure vessels in the petrochemical and power generation industries, especially where resistance to hydrogen attack and creep is required.
How does SA387 Grade 22 Class 1 differ from Class 2?
Class 1 is supplied in an annealed state for better formability, while Class 2 is normalized and tempered for higher as-delivered strength. Class 1 is chosen when complex fabrication is needed before final PWHT.
What is the post-weld heat treatment (PWHT) for SA387 Grade 22 Class 1?
PWHT is mandatory and typically performed at 1250-1300°F (675-705°C) to relieve welding stresses, prevent hydrogen-induced cracking, and restore corrosion resistance in the weld zone for high-temperature service.
What are the equivalent materials to SA387 Grade 22 Class 1?
Common equivalents include UNS K21590, European 10CrMo9-10 (1.7380), and the generic designation 2.25Cr-1Mo steel. However, exact equivalency depends on heat treatment and certification requirements.
Can SA387 Grade 22 Class 1 be used in hydrogen service?
Yes, its 2.25% chromium and 1% molybdenum content provides excellent resistance to high-temperature hydrogen attack (HTHA), making it a standard choice for hydrogen processing units in refineries.
What are the forming and machining guidelines for SA387 Grade 22 Class 1?
Due to its annealed condition, it offers good cold formability but requires preheating for hot forming and controlled machining to avoid excessive work hardening, with tooling suitable for alloy steels.
What standards certify SA387 Grade 22 Class 1 plates?
Plates are certified to ASME SA387/SA387M and ASTM A387/A387M standards, with mill test reports (MTRs) providing chemical and mechanical properties per EN 10204 3.1 or 3.2.
How does SA387 Grade 22 Class 1 compare to Grade 11 or Grade 5?
Compared to lower-alloy grades like Grade 11 (1.25Cr-0.5Mo) or Grade 5 (5Cr-0.5Mo), Grade 22 offers superior high-temperature strength and hydrogen resistance, but requires stricter welding and heat treatment controls.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
