How Different ASTM A53 and A500?

ASTM A500 is available in cross-sections matching each of the cross-sections for ASTM A53steel pipe, there are many more cross-sections available in A500.

ASTM A53 Standards

ASTM A53 pipe, a standard specification for black and hot-dipped, zinc-coated, welded and seamless  steel pipe, is used for mechanical and pressure applications as well as ordinary uses in steam, water, gas and air lines. ASTM A53 can be formed and welded. Pipe sizes are properly designated using the Nominal Pipe Size (NPS).  This is the nominal pipe diameter with a scheduled wall thickness (i.e., 4 inch Schedule 40 pipe). the ASTM A53 Specification requires testing (i.e., pressure testing) that is not needed for structural applications. This additional testing can add unnecessary additional cost. A53 pipe are only available in standard pipe sizes.  Round HSS come in a variety of sizes and wall thicknesses.

ASTM A500 Standards

ASTM A500 is a standard specification for cold-formed welded and seamless carbon steel structural tubing in round, square and rectangular shapes. ASTM A500 is the most common specification in North America for Hollow Structural Sections.  Round HSS sections are properly designated by indicating the outside diameter in decimal inches by the nominal wall thickness to three decimal places (i.e., 5.563 x 0.250).  

ASTM A500 applications include structural supports, building columns, highway signs, oil field services and communication towers, to name a few. All steel structures have their pros and cons, but ultimately ASTM A500 is the better choice when you need a round profile.

The tolerances of A500 are tighter than those of A53, therefore the A500 round HSS have a higher degree of quality and less variability.

A500 round HSS have greater strength-to-weight ratios than A53 pipes.