ASTM A53 Seamless pipe ASTM A53 is a carbon steel alloy, which can be used as structural steel or for low-pressure pipelines. ASTM A53 (ASME SA53) carbon steel pipe is a specification that covers seamless and welded black and hot-dipped galvanized steel pipe in NPS 1/8″ to NPS 26. A53 is intended for pressure and mechanical applications and is also acceptable for ordinary uses in steam, water, gas, and airlines. A53 pipe comes in three types (F, E, S) and two grades (A, B). A53 Type S is a seamless pipe found in Grades A and B) https://www.slpipeline.com/ASTM-A53-SEAMLESS-PIPE.html