SA 387 Gr 11 Cl 2 is a chromium-molybdenum alloy steel plate grade built for pressure vessel service. Oil and gas facilities push equipment through elevated temperatures and sustained pressure, and a plate that softens under those conditions puts the entire unit at risk. Chromium adds oxidation resistance while molybdenum strengthens the steel at high temperatures. Fabricators specify the SA 387 Gr 11 Cl 2 Plate, where heat and pressure meet in the same vessel wall.
What Is SA 387 Gr 11 Cl 2 Plate?
SA 387, recognized as ASTM A387 Gr 11 Cl 2 Plate, covers chromium-molybdenum alloy steel plates made for pressure vessels at elevated temperatures. Grade 11 means the alloy composition; Class 2 is a heat treatment and strength level applied to that same alloy. SA 387 Grade 11 Class 2 Plate and ASTM A387 Gr 11 Cl 2 Plate are the same designation, with Class 2 selected for increased strength than Class 1 offers.
Key Properties of SA 387 Gr 11 Cl 2
- The chromium-molybdenum alloy composition balances strength and heat resistance in one plate.
- Elevated-temperature performance lets the material hold its mechanical properties as vessel walls heat up.
- Strength levels suited to pressure-vessel design support thinner wall sections than plain carbon steel at the same rating.
- Resistance to hydrogen attack makes the grade common in hydroprocessing units, and weldability under correct preheat and post-weld heat treatment supports reliable fabrication.
Actual mechanical properties depend on plate thickness, heat treatment, the design code, and operating conditions.
Why Is SA 387 Gr 11 Cl 2 Used?
Processing crude oil and natural gas rarely happens at room temperature or atmospheric pressure. Refining and petrochemical units run continuously at high heat, often above 400°C, while carrying corrosive streams. Chromium-molybdenum alloy steels hold strength and dimensional stability as temperatures rises, letting designers build vessels that carry pressure safely for years. No single grade fits every environment, so engineers still validate the choice against code requirements.
Common Oil and Gas Applications
- Pressure vessels holding process fluids under sustained pressure rely on this grade for shell and head plates.
- Boilers use the material where steam generation demands strength and heat tolerance.
- Heat exchangers benefit from a plate that resists thermal fatigue across repeated heating cycles, while hydroprocessing equipment depends on resistance to hydrogen attack.
- Refinery process units, storage vessels, and separators round out the typical uses, though each depends on design temperature and the applicable code.
RPF Pipes & Fittings supplies Alloy Steel SA 387 Gr 11 Cl 2 Plate from ready stock for these needs.
Benefits of SA 387 Gr 11 Cl 2 Plate for Pressure Equipment
- Engineers reach for this grade because it is built for pressure-vessel service rather than adapted from general-purpose steel.
- It handles elevated-temperature applications where standard carbon steel would lose strength too fast for safe design margins.
- Strength and durability figures support long inspection intervals on critical vessels.
- The chromium-molybdenum chemistry stays consistent from mill to mill under ASTM and ASME control, and fabrication proceeds without cracking when preheat and post-weld heat treatment are followed correctly.
Factors to Consider When Selecting SA 387 Gr 11 Cl 2 Plate
- Plate thickness and dimensions need to match the vessel design calculation and available stock sizes.
- Required mechanical properties must align with the design code’s allowable stress tables, and heat treatment conditions should be confirmed on the mill certificate.
- Operating temperature, pressure, and corrosion exposure, including hydrogen or sulfur, determine whether extra allowances apply.
- Welding requirements, applicable ASTM and ASME specifications, and testing needs, such as ultrasonic and impact testing, shape the final order, and traceable mill certificates confirm the chemistry matches.
Material selection should always come from the complete equipment design rather than the grade name alone.
Conclusion
SA 387 Gr 11 Cl 2 is specified in oil and gas pressure-vessel and process equipment because it combines chromium-molybdenum alloy chemistry with strength suited to elevated-temperature service. Refineries and hydroprocessing units depend on plates that hold their properties under sustained heat and pressure. Getting the grade right means confirming specification compliance, running the required testing, and following correct fabrication practices. RPF Pipes & Fittings stocks and supplies this grade with full mill certification for fabricators worldwide. Contact us for current stock availability and thickness options on your next project.