Patuha-2 / Geothermal steam scrubbers.

Patuha-2 expands an established geothermal field on the Bandung plateau. The client required a matched set of two scrubbers and two atmospheric flash tanks, all rated for chloride-bearing two-phase steam at elevated temperature.

Schedule was driven by the turbine erection window. Vessels had to leave the Cikarang shop fully tested and documented in time for an over-dimensional convoy to the plateau.

Three failure modes governed the design: chloride pitting and stress-corrosion cracking of austenitic stainless, thermal cycling between hot operation and cold shutdown, and seismic loading per ASCE 7-16 for a Site Class D location.

Geothermal steam quality varies well-by-well. Internals were sized for the worst-case droplet load reported by the resource team, with a margin on demister area.

SS316L was selected over 304L for chloride tolerance and over duplex for weldability at the wall thicknesses involved. Welding procedures were qualified on production-thickness coupons, with ferrite control and a maximum hardness target in the heat-affected zone.

Filler metals were lot-controlled. Each heat number was traced from mill certificate through to the final hydrotest report.

Shell courses were rolled on the 80 mm plate roll and fit-up was completed on the rotator beds. Longitudinal seams were GTAW root with SAW fill and cap; circumferential seams followed the same procedure stack.

Phased-array ultrasonic testing of the longitudinal seams ran in parallel with fit-up of the next course to compress the critical path.

The third-party inspector witnessed weld-procedure qualification, PWHT cycles, NDE on production welds, and the hydrotest at 1.43 × design pressure. A helium leak test followed for the final box-up.

The Manufacturer's Data Report was issued in the client's template with full traceability — heat numbers, NDE film, PWHT charts and hydrotest curves cross-referenced to the weld map.

Each vessel shipped as a single piece on a low-bed trailer under over-dimensional permit. Route survey, escort and bridge checks were coordinated with the EPC logistics team. Site reception, off-loading and setting on the foundation were witnessed by SKM field staff.

All four vessels were delivered within the contracted window with zero NDE rejects on first submission. The MDR was accepted by the third-party inspector without revision.

The same procedure stack is now the reference for follow-on geothermal scrubber inquiries.