ASME B31.3 §322.6.3 via ASME BPVC VIII UG-135(f)

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 B31.1 Section 137.4

This is a proper hydrostatic test per ASME B31.1. The test pressure of 1.5 times design pressure (150 × 1.5 = 225 PSI) is correct. The 10-minute hold with visual inspection of all joints meets the minimum requirements. The system passes inspection.

ASME B31.3 §314.1(a) / §314.2.1

Threaded joints are a common leak path under vibration and thermal cycling, and a pump discharge sees both — ASME B31.3 para. 314.1(a) says threaded joints should be avoided where crevice corrosion, severe erosion or cyclic loading may occur, and 314.2.1 restricts them under severe cyclic conditions. Welded or flanged is the right call here. But do not carry away a size rule that does not exist: B31.3 sets NO NPS limit on threading, and ASME B16.11 lists threaded fittings through NPS 4. The "nothing threaded above 2 inch" cap most people quote comes from the project piping specification, not from the code. Where the code does address the lost wall thickness, it does it through the minimum schedule of Table 314.2.1 — a required wall, not a size ban.

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.