Boiler Pipe

Product Description

Primary Material Standards & Grades

1. Low & Medium Carbon Steel (Up to ~425°C / 800°F)

• ASTM A192 / ASME SA192: Seamless carbon steel tubes for high-pressure firetube and watertube boilers and superheaters. Low carbon content ensures easy bending and flaring.

• ASTM A210 Grade A-1 / C: Medium-carbon seamless tubes providing higher yield strength for boiler water walls and economizer tubes.

• ASTM A106 Grade B: The standard seamless pipe spec for boiler external piping, blowdown lines, and main steam headers.

2. Ferritic Alloy Steel / Chrome-Moly (425°C to 600°C / 800°F to 1100°F)

Used in superheater and reheater zones where carbon steel loses creep strength and scales rapidly:

• ASTM A213 / ASME SA213 (Tubes):

  • T11 (1.25Cr-0.5Mo): Standard low-alloy grade for medium superheaters.

  • T22 (2.25Cr-1Mo): Higher thermal stability and oxidation resistance.

  • T91 (9Cr-1Mo-V): Modified martensitic steel offering high creep-rupture strength, allowing thinner wall profiles in ultra-supercritical boilers.

• ASTM A335 / ASME SA335 (Pipes):

  • P11, P22, P91: Matching pipe designations for heavy-wall headers and main steam piping.

3. Stainless Steel (600°C+ / High-Corrosion Zones)

• ASTM A213 (TP304H, TP347H, TP310S): High-carbon austenitic grades chosen for creep strength and fire-side corrosion resistance in advanced superheater loops.

Key Requirements for Boiler Tubes

1. Seamless Construction: Almost all high-pressure boiler tubes are seamless to eliminate weld seam vulnerability under cyclic thermal fatigue.

2. Hydrostatic & Non-Destructive Testing: Every length undergoes hydrostatic testing or Ultrasonic / Eddy Current testing per ASME Section I code.

3. Flaring & Flattening Tests: Mechanical tests ensure the material can handle cold bending, expanding, and rolling into drum seats during boiler assembly.

4. Important Distinction: Pipe vs. Tube in Boilers

   In boiler engineering, "pipe" and "tube" refer to two distinct functional zones:

   • Boiler Tubes (Heat Exchanger Duty): Sized by exact Outer Diameter (OD) and minimum wall thickness. Installed directly inside the furnace zone (water walls, superheaters, reheaters, economizers) to absorb heat.

   • Boiler Piping (Transport & Headers): Sized by Nominal Pipe Size (NPS) and Schedule. Used to carry high-pressure steam and hot water outside or between major vessels (main steam lines, feed water piping, steam headers).