was to replace the vessel with one that is internally cladded with SS316L, providing superior corrosion resistance against wet H₂S and amine service. A modified datasheet for a new vessel design, including internal lining and an updated inlet distributor, was developed. x Operating at lower pressure: Process simulations were conducted using Aspen HYSYS to determine whether the unit could safely operate at reduced pressure (6.5 kg/cm², down from a typical 7.5 kg/ cm²). This would reduce mechanical stress on the
Figure 4 Original inlet distributor configuration
Old distributor
New distributor
Figure 5 Modified inlet distributor design with splash elimination
V-38. The primary objective was to ensure structural integrity and continued safe operation of the vessel while preparing for long-term solutions. The evaluation considered operational feasibility, repair time, regulatory compliance, and the ability to sustain pressure containment in a corrosive environment. Patch repair of shell section: The most immediate and practical solution was to cut and replace the affected area measuring approximately 3,360 mm x 3,650 mm with 28 mm-thick SA 516 Gr. 60 insert plates. This method followed ASME PCC-2 Article 201, which outlines the procedure for butt-welded insert plates in pressure components. Due to the unavailability of 32 mm plates, 28 mm thickness was selected based on structural assessment. v Full shell course replacement: Replacing entire shell courses 2 and 3 with 32 mm- thick plates was considered. While this option would have restored the vessel to near- original specifications, it would have involved more extensive downtime, material handling, and weld area, which made it less desirable under the time constraints of the ongoing unit turnaround. w Complete vessel replacement with internally cladded shell: A long-term solution
thinned shell areas. PSV setpoints and flare loads were reviewed, and pressure reduction was remotely feasible but not a long-term solution due to extensive modifications. y Bypassing V-38: Routing rich amine directly to the ARU was evaluated but rejected due to downstream pressure constraints. The rundown pipeline and rich amine flash drum (RAFD) in SRU-2 were not rated for the pressures or two- phase flow. In addition, the flare system could not accommodate the potential gas blow-by scenario. z Encasing or lap patch welding: External encasing or lap patch welding was dismissed due to limited inspection accessibility, ineffectiveness in pressure containment, and lack of reliable nondestructive evaluation (NDE) capability for lap welds under pressure. { Alternate vessel replacement: Replacement with a retired hydrogen generation unit (HGU) pressure swing adsorption (PSA) vessel was considered. It was structurally adequate, but nozzle configuration, instrumentation ports, and foundation modifications made this a less attractive interim solution. Engineering repair strategy implemented: A full insert patch repair was conducted using 28 mm plate. Internal stiffeners were
Refining India
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