ASME B31.1 Section 137.4

ASME B31.1 Section 122 / ASHRAE Handbook

Condensate is highly corrosive (carbonic acid from CO2). Condensate return piping should be stainless steel, copper, or use Schedule 80 carbon steel with corrosion allowance. Standard weight carbon steel corrodes rapidly.

ASME B31.1 Section 127.4 / AWS D10.9

Undercut exceeding 1/32 inch (0.8 mm) on any weld is a rejectable defect per ASME B31.1 and AWS D10.9. Undercut creates a stress riser that can initiate fatigue cracking under thermal cycling.

ASME B31.1 Section 137 / EJMA Standards

Expansion joints must be restrained or isolated during hydrostatic testing. Test pressure can cause unrestrained bellows to over-extend, permanently damaging the joint.

ASME B31.3 / AWS D18.1 — Stainless Steel Welding

Sugaring (granular oxidation on the root side) indicates insufficient argon purge gas during welding. The weld root must be shielded with inert gas to prevent oxidation on high-purity stainless steel systems. A sugared weld is structurally compromised and a contamination source.

ASME B31.3 Section 321 / MSS SP-58

High-temperature piping (above 400°F) experiences significant thermal expansion. Without spring supports, thermal movement creates excessive stress at anchors, branch connections, and equipment nozzles. ASME B31.3 requires stress analysis to account for thermal loads, and spring hangers are the standard solution for absorbing vertical movement.

ASME B31.3 Section 328.5.2 / Section 304.3.3 / Table 341.3.2

Socket-weld construction is poor practice on a 4-inch process line. ASME B31.3 restricts socket welds in the larger sizes: under severe cyclic conditions they are generally limited to NPS 2 and smaller (Table 341.3.2), and socket-welded branch connections are limited to NPS 2 and not more than one-quarter of the header size per Section 304.3.3. Although ASME B16.11 socket-weld fittings are made through NPS 4, butt-weld fittings should be used on 4-inch and larger hazardous-fluid piping to provide full-penetration joints with better strength and radiographic inspectability.