Petrochemical & Refinery Seamless Steel Pipe ASTM / ASME 335 Standard P91


The pipe of P91 is mainly used in petrochemical & refinery field. Mechanical properties and dimensions are uniform in longitudinal & transversal directions. Pipe has better surface and without any defects.

1. Reference Documents

• ASTM A999/A 999M Specification for General requirements for Alloy and Stainless Steel Pipe.
• ASTM E 213 Practice for Ultrasonic Examination of metal Pipe and Tubing
• ASTM E 309 Practice for Eddy-Current Examination of Steel Tubular Products Using Magnetic Saturation
• ASTM E 381 Method of Macroetch testing Steel Bars, Billets, Blooms, and Forgings
• ASTM E 570 Practice for Flux Leakage Examination of Ferromagnetic Steel Tubular Products
• ASME B26.10M Welded and Seamless Wrought Steel Pipe

2. Standards:
ASTM A335 Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service

3. Application:
For high pressure boiler and steam header pipes; petrochemical industry pipes; thermal power plant; nuclear power plant; USC boiler.

4. Ordering Information
Quantity (feet, meters, or number of lengths),
Name of material (seamless alloy steel pipe),
Grade (P91),
Manufacture (hot-finished or cold-drawn),
Size using one of the following:
NPS and schedule number;
Outside diameter and nominal wall thickness;
Outsider diameter and minimum wall thickness;
Inside diameter and nominal wall thickness;
Inside Diameter and minimum wall thickness.
Length (specific or random)
End finish (plain end or bevel end)

5. Chemical Requirements

6. Available Size Range

7. Tensile Requirements
Tensile Strength min.: 85ksi / 585MPa
Yield Strength min.: 64ks / 415MPa

8. Inspection & Test
Chemical composition, mechanical properties ( tensile strength, yield strength, elongation, flaring, flattening, bending, hardness, impact test), surface and dimension, NDE, hydrostatic test.

9. Manufacture
Hot Rolled for 8'' and above or Cold Drawn for 6'' and below

10. Manufacturing Process
Raw Material Inspection → Cold Centering → Heating → Piercing & Rolling → SIzing → Heat Treatment → Testing → Finishing → NDE → Visual & Dimension Inspection → Marking → Storing & Shipping

11. Heat Treatment

Normalizing
Normalizing for all product forms shall be performed within the temperature range of 1040-1080°C. Once the surface temperature of the component has exceeded 1040°C, the minimum time at temperature shall be specified in the table below.

The product shall be air cooled outside of the furnace and away from any source of heat or other conditions that would retard the rate of cooling or cause non-uniform cooling. Cooling shall be continuous down to at least 95°C at the metal surface before tempering.

The rate of cooling shall be at least 5°C/min from the normalization temperature to 600°C. Note that for components greater in wall thickness than 75mm, forced air-cooling or oil quenching or the equivalent from the normalizing temperature to a surface metal temperature below 600°C may be necessary to achieve the required mechanical properties.

Tempering
Tempering for all product forms is to be performed within the temperature range of 770-790°C. Time at the tempering temperature shall be at least one hour per 25mm of thickness, with a minimum tempering time of 10 minutes. The product may be furnace cooled or cooled in still air from the tempering temperature, so long as excessive distortion, excessive thermal stresses, and over-tempering are avoided.