Preventing weld failure in a 100-foot stainless trough

Client Requirements

A municipal water treatment authority specified a corrosion-resistant storage tank for chlorinated process water in a facility located inside a seismic design category D zone. The material of record was duplex 2205, chosen for chloride pitting resistance. The tank needed an ASME U-stamp and had to accommodate saddle loading calculated for the seismic spectrum at the install site.

Northern’s Approach

Duplex 2205 is unforgiving on heat input, so welding procedures were run on our qualified duplex WPS with controlled interpass temperatures and matching filler chemistry. Every pressure-boundary weld was radiographed 100% per ASME Section VIII Division 1, and the saddle supports were finite-element checked against the seismic loading before fabrication. Rolling was staged on our heavy roller with in-process ferrite measurements to confirm the microstructure stayed within spec after forming.

Outcome

The tank passed hydrostatic test at 1.5x maximum allowable working pressure with no rework. The authorized inspector applied the ASME U-stamp, and Northern issued a 25-year corrosion warranty backed by the duplex material certification package. The tank has been in continuous service without incident.