Weight per metre and Barlow pressure formulas with unit discipline, worked examples (NPS 6 Sch 40, X52 line pipe), nominal versus minimum wall, a free embedded calculator, and sanity-check tables for the most common sizes.
The container loading arithmetic for steel pipe: payload versus floor-space limits, worked capacity tables for common sizes, the European road-weight trap, and lashing practice.
How square and rectangular hollow sections are made, EN 10210 versus EN 10219, ASTM A500 versus A1085, the tolerances to inspect, galvanising rules, and what really moves HSS price.
P = 2St/D explained with yield, code-allowable and mill-test worked examples, thin-wall limits, and how to reverse it for ordering wall thickness.
What random, single-random, double-random and exact lengths mean in practice, why they price differently, and how to write length into a PO.
Verified wall and OD tolerance tables across the four standard families, nominal-wall vs minimum-wall logic, and how to write tolerances into a PO.