Construction work requires pipes that can withstand exposure to the elements without running the risk of corrosion. For this reason, carbon steel piping is typically preferred for building bridges and flyover constructions. These pipes have great environmental resistance while still being durable enough to support the structures adequately.

ASTM A500 pipes fulfill these criteria of tensile strength and corrosion resistance by acting as a high-grade structural framework for construction projects. These pipes come in numerous sizes, covering both seamless and cold-finished piping. A500 pipes are versatile and have several uses in construction owing to their shaped availability. This piping can be found in various shoes, helping fit the requirements of different building projects.

Construction Pipes. Source: Shutterstock

ASTM A500 Specification for Mechanical Construction Machinery.

This specification provides the methods involved in producing carbon steel piping. ASTM A500 piping is mostly used in construction and comes in shapes like round, rectangular, square, or customized sizing. The pipes can be of various types, including welding, cold-formed, and seamless.

Processes like open hearth, electric, and basic oxygen furnaces improve the mechanical properties of the steel, which aids its applications in construction projects like bridges, buildings, flyovers, and other large structures. 

Though ASTM A500 pipes come in grades A, B, C, and D, only the last one requires post-production heat treatments. 

Characteristic Features of ASTM A500 Pipes

  • Alongside round, rectangular, and square tubing, ASTM A500 also covers welded, bolted, and riveted tubing shapes for use in construction.
  • An adjacent specification/counterpart to ASTM A500 is ASME SA500.
  • Compared to ASTM A53 pipes, A500 piping has straightness tolerances of ¼" per every 10 feet, leading to better application in projects requiring curved structural steel. 
  • The Outer Diameter (OD) of A500pipes ranges from 0.4 to 32.2 inches.
  • The length of ASTM A500 pipes is usually limited to 18 feet.
  • The wall thickness of these pipes varies from 0.8 mm to 75 mm.
  • This specification states that A500 welded pipes must be made from electric resistance welding for optimum strength. The steel used must be flat-rolled, and the result must be unfurnished, still containing the flash. 
  • Grade B of ASTM A500 pipe has higher strength and closer tolerances fit for application in construction.
  • Longitudinal welding gets preferred in welded pipes, especially one that uses butt joints that can get fused longitudinally to ensure the structural strength and design of the construction pipe.
  • ASTM A500 carbon steel pipes are to be made using open earth, electric, or basic oxygen furnace. 
  • Dimensional variations in wall thickness, Outside Diameter (OD), twist, and structural straightness are available during A500 pipe production. 

Dimensional Variations in ASTM A500 Pipes

Permissible Variations in Wall Thickness of ASTM A500 Pipes

According to ASTM A500 specifications, carbon steel pipes' wall thickness should not be less than 90% of the specified nominal wall thickness. Similarly, the maximum thickness should not exceed 110% of the given nominal wall thickness. However, variations within this 10% range are permitted below or above. This rule also excludes the fused seam region of welded pipes. 

The wall thickness measurement should be taken at the flat center for shapes other than round, particularly rectangles and square-shaped pipes. This step is crucial as the WT for special-shaped pipes refers only to the inner center of the flats. 

Permissible Variation in Outside Diameter (OD) of ASTM A500 Pipes

A variation of 5% above or below the specified outer diameter is allowed in ASTM A500 pipes. However, for this to be applicable, the pipe must be round, with an outside diameter of 1.9 inches or smaller. 

For pipes that are rectangular or square shaped, a similar variation is allowed. A maximum three-fold radius deviation from the specified wall thickness is authorized outside any corner of these pipes.

Variations in Straightness and Side Squareness of ASTM A500 Pipes

The variation in pipe straightness is calculated using the following formula

  • Permissible straightness of ASTM A500 carbon steel pipes = ⅛ inches X total pipe feet in length divided by five.

Whereas for square or rectangular structural tubing, a variation of 2 Degrees above the 90 degrees rule is permissible. 

Reference Specifications for ASTM A500 Pipes

  • ASTM A752: This specification provides the testing practices and methods and the terminology/definitions for chemically testing ASTM A500 steel pipes.
  • ASTM 700: The post-product steps of ASTM A500 pipes are guided by the standards set by this specification. ASTM 700 sets up practices for pipe marking, packaging, and loading for shipments.
  • ASTM A941: This standard provides the definitions of A500 pipes, including stainless steel, iron-based alloys, and other related alloy pipes.
  • ASTM 370: Mechanical testing is necessary to check the flaws in the piping products. ASTM 7– provides the setup, including terminology and methods for successfully testing defects in ASTM A500 pipes.

Chemical Composition of ASTM A500 Pipes

Chemical Composition of ASTM A500 Pipes

  Element 
ASTM A500 Grade A, Grade B, Grade D 		          ASTM A500 Grade C
   Heat Analysis  Product Analysis  Heat Analysis  Product Analysis
  Carbon  0.26% (max)  0.30% (max)  0.23% (max)  0.27% (max)
  Manganese  1.35% (max)  1.40% (max)  1.35% (max)  1.40% (max)
  Phosphorous  0.035% (max)  0.035% (max)  0.035% (max)  0.045% (max)
  Sulfur  0.035% (max)  0.045% (max)  0.035% (max)  0.045% (max)
  Copper  0.20% (min)  0.18% (min)  0.20% (min)  0.18% (min)

Tensile Properties of ASTM A500 Pipes (Shaped Structural Tubing)

                                           Shaped Structural Tubing
   Grade D  Grade C  Grade B  Grade A
  Elongation %(In 2 inches)  23% (min)  21% (min)  23% (min)    25% (min)
  Yield Strength  250 MPa (min)  345 MPa (min)  315 MPa (min)  270 MPa (min)
  Tensile Strength  400 MPa (min)  425 MPa (min)  400 MPa (min)  310 MPa (min)

Tensile Properties of ASTM A500 Pipes (Round Structural Tubing)

                                           Round Structural Tubing
   Grade D  Grade C  Grade B  Grade A
  Elongation %(In 2 inches)  23% (min)  21% (min)  23% (min)    25% (min)
  Yield Strength  250 MPa (min)  315 MPa (min)  290MPa (min)  230 MPa (min)
  Tensile Strength  400 MPa (min)  425 MPa (min)  400 MPa (min)  310 MPa (min)