Boiler pipes are tubing made from chromium molybdenum alloys for high-temperature applications. They can be seamless or ERW, but the former is more popular due to its higher pressure/temperature resistance. According to these requirements, boiler tubes can get divided into two types;

  • General use/ medium-pressure boiler tubes
  • High-pressure boiler tubes

Types of Boiler Pipes

General use/ medium-pressure boiler tubes are used in environments up to 842 degrees Fahrenheit. These pipes typically get made via the hot rolling and cold drawing process. These pipes have applications as 

boiling water pipes

locomotive boilers

arch brick pipes

superheated steam pipes

smoke pipes and more.

On the other hand, high pressure boiler tubes have higher corrosion resistance and durability than general use boiler pipes. They get used for high temperature and high pressure applications where the pipes risk oxidization on exposure to corrosive steam and fluid. Due to their structural stability, high pressure boiler tubes get used in high and ultra-high pressure applications, including

  • Air ducts in petrochemical industries
  • Reheater tubes
  • Main steam tubes 
  • Superheater pipes

Manufacturing Process for Boiler Pipes

The manufacturing for both general use boiler pies and high pressure boiler tubes is the same initially. Both types of boiler tubing follow the crucial steps of 

  • Fine Drawing
  • Surface Brightening
  • Hot Rolling
  • Cold Drawing 
  • Heat Expansion

However, high pressure boiler tubes are processed further to improve their corrosion resistance, toughness, and hardness. These pipes go through the following extra process compared to general boiler pipes/ medium-pressure boiler pipes.

  • Quenching- This process refers to the practice of instant cooling where heated pipes get dipped into water and oil for cooling. Quenching improves steel hardness as the pipes must adjust to the quick changes in surface temperature.
  • Tempering rids the pipe of the brittleness caused by quenching.
  • In annealing, the steel is heated to a specific temperature and left to cool slowly in lime. This process helps get rid of the pie's internal stress. 

Characteristic Features of Boiler Pipes

  • Due to the high pressure application, only seamless pipes and ERW get used as boiler products.
  • Boiler pies are available in carbon steel, alloy, and stainless steel options.
  • The Outer Diameter of boiler pipes varies from 6 mm to 1250 mm. 
  • Boiler pipes have a low thickness ranging from 1 mm to 50 mm.

Boiler Pipe Applications

Boiler pipes have applications in

  • Energy Generation
  • Electric Power Plants 
  • Steam Boilers
  • Petrochemical Industry
Boiler pipes. Source: Shutterstock

Boiler Pipe Specifications

Your home could have different types of heat systems. Some important specifications for boiler pipes include ASTM A178, ASTM A192, ASTM 210, and ASTM 209. These classifications get used to standardize boiler pipes according to their 

  • Size
  • Shape
  • Marking
  • Tensile Properties
  • Hardness and Softness Index
  • Weight Deviations
  • Quality Testing and Inspections

Chemical Properties for ASTM A192 Boiler Pipes

  Elements  ASTM A192
  Silicon   0.25% (max %)
  Sulfur  0.035% (max %)
  Carbon  0.06% to 0.18 %
  Manganese  0.27 % to 0.63 %
  Phosphorous  0.035% (max %)

ASTM A178 Specification for Boiler Pipes

This specification covers ERW carbon steel and carbon-manganese pipes for application in superheaters and boilers. Under AST A178, pipes fall under the following range;

  • ASTM Grade A- For steel with low carbon content
  • ASTM Grade C- For steel with medium carbon content
  • ASTM Grade D- For carbon-manganese steel 

Chemical Properties of ASTM A178 Pipes

  Elements  ASTM A178 Grade A  ASTM A178 Grade C  ASTM A178 Grade D  
  Silicon      0.10% (min %)
  Sulfur  0.035% (max %)  0.035% (max %)  0.015% (max %)
  Carbon  0.06% to 0.18 %  0.035% (max %)  0.25 % (max %)
  Manganese  0.27 % to 0.63 %  0.80 % (max %)  1.0% to 1.50%
  Phosphorous  0.035% (max %)  0.035% (max %)  0.30% (max %)

Tensile Properties of ASTM A178 Pipes 

  Properties  ASTM A178 Grade A  ASTM A178 Grade C  ASTM A178 Grade D  
  Hardness(maximum)  77 HRB  79 HRB  77 HRB
  Tensile Strength  325 MPa  415 MPa  485 MPa
  Yield Strength  180 MPa  425 MPa  275 MPa

ASTM 210 Specifications for Boiler Pipes

This specification covers the seamless medium carbon steel boiler and superheater tubing standards. Some of the chief characteristics of ASTM 210 pipes include; 

  • Two ASTM Grades A1 and C cover the carbon steel boiler pipes standard.
  • The Outer Diameter of these pipes range from 12.7 mm to 114.3 mm
  • The average wall thickness of ASTM 210 pipes ranges from 0.8 mm to 15 mm 

Tensile Properties for ASTM 210

  Properties  ASTM A210 Grade A1  ASTM A210 Grade C
  Elongation (%)  >30  >30
  Tensile Strength  >415 MPa  >485 MPa
  Yield Strength  >255 MPa  >275 MPa

Chemical Properties for ASTM 210

  Elements  ASTM 210 Grade A1      ASTM 210 Grade C
   Silicon  0.035 (max)   0.035 (max)
  Sulfur  0.035 (max)   0.035 (max)
  Carbon  0.27 (max)   0.35 (max)
  Manganese  0.93 (max)   0.29 to 1.06
  Phosphorous  0.035 (max)   0.035 (max)

Other Specifications for Stainless Steel Boiler Pipes

  • ASTM A213
  • ASTM A210M: Specification for seamless medium-carbon steel boiler and superheater tube
  • ASTM A213: Specification used for making seamless ferritic/austenitic alloy steel superheater, steel boiler, and heat exchanger tubes
  • SA213-T2: ASME SA213 T2 SA213-T9
  • SA213-T12: Specification for seamless ferritic/austenitic alloy boiler, superheater, and heat-exchanger.
  • SA213-T11: The tubes made using this specification get used in heat exchangers, super heaters, and boilers.
  • SA213-T22: ASM T22 Boiler Tube: used in acidic and corrosive applications such as hydrochloric processing that require hydrochloric acid and aluminum chloride catalyst.