Piping (ASME B31.3)

A: Picking the wrong material here buys you sulfide stress cracking and a leak after startup, not a paperwork issue. Wet H2S in amine drives SSC, not uniform wall loss, so hardness and PWHT matter more than nominal corrosion rate. Carbon steel is acceptable when hardness is controlled per NACE; stainless and Cr-Mo miss the failure mechanism and extra CA doesn’t stop cracking.

A: Overshooting this number pushes you into a heavier schedule and missed weight targets; undershooting fails the pressure test. Using the B31.3 pressure design equation with OD-based diameter gives roughly 2 mm before adding CA and mill tolerance. The larger values mix in allowances that aren’t part of the required thickness, and the smallest drops the diameter basis.

A: Blowing a transmitter diaphragm or missing a leak forces a drain-down and schedule slip. B31.3 allows using available design data, but you must protect the weakest component you can identify. Bounding the test pressure from known ratings keeps the test valid while avoiding damage; the other paths either assume ratings or invalidate the test boundary.

A: Ignoring this leads to a line that technically fails code the moment you approve the change. Allowable stress drops with temperature for most steels, which directly reduces MAWP. The safe move is to re-rate the line against the new temperature using B31.3 tables.