PTQ Q2 2026 Issue

Risk-based integrity approach to vessel life extension

Case studies address severe localised corrosion in process equipment, highlighting application methodology and implications for mission-critical process assets

Hayden Hill Integrated Global Services

I n refining and petrochemical complexes, process ves - sels, towers, and columns often operate under harsh chemical conditions, including exposure to amines, caus - tic, organic acid-rich condensates, chlorides, and corrosive thermal cycling, leading to accelerated metal wastage. The following case studies are from three major Asian facilities (two refineries and a chemical plant) of a multi - national oil and gas company, addressing severe local - ised corrosion in a quench column, a tail gas treating unit column, and a high carbon fractionation (HCF) tower by applying High Velocity Thermal Spray (HVTS) cladding as a metallurgical upgrade. The proprietary on-site cladding technology intervention was completed during a scheduled turnaround, without the need for post-weld heat treatment (PWHT). It resulted in a dense, low-porosity, high-nobility metallic lining with an anticipated service life extension of 15 years or more. The inspection findings, technical and economic justifica - tion, application methodology, quality assurance, and early performance are described, and the discussion includes practical lessons and broader implications for mission-crit - ical refinery assets. Equipment risks Process vessels, towers, and columns are mission-critical in various refinery and petrochemical units, including: • Tail gas unit quench column. • HCF tower. • Ethylene (EKT) quench column. The quench column is used to cool gas containing hydro - gen sulphide (H₂S), carbon dioxide (CO₂), and sulphur diox - ide (SO₂) by direct counter-current contact with circulating water. Soda caustic (NaOH) is injected into the quench water to neutralise the acid in the solution. The tower inter - nal shell section suffered internal corrosion from sour water and from acid corrosion caused by SO₂ breakthrough, resulting in a pH below 5.5. The HCF tower removes H₂S and ammonia (NH₃) from the incoming kerosene feed. The top section of the tower suffered severe corrosion from corrosion under-deposits, sour water corrosion, and corrosion caused by ammonium chloride (NH4CL), salts, and condensation of hydrochloric acid (HCL).

The EKT quench column, with a 9m diameter, had SS 316L lining installed during the 2013 turnaround. Organic acid had penetrated under the lining and affected the bot - tom section of the column. If unchecked, corrosion can lead to localised thinning, pitting, and ultimately premature failure of the pressure boundary, risking unplanned shutdowns and substantial repair costs. Corrosion mitigation Traditional remediation strategies, such as weld overlay, full-vessel replacement, or conventional coatings, have drawbacks, including high heat input (requiring PWHT), long execution times, and limited corrosion resistance in aggressive acid/chloride environments. This study describes a safety and schedule-sensi - tive metallurgical upgrade using HVTS, executed during planned turnarounds at major Asian refining petrochemical facilities. The solution demonstrates how modern thermal spray technology can deliver a durable corrosion barrier, enabling asset life extension, minimising downtime, and aligning with the facility’s risk-based inspection (RBI) and reliability-centred maintenance (RCM) philosophy. Technology overview Thermal spray techniques, including atmospheric plasma spraying (APS), high-velocity oxy-fuel (HVOF), twin-wire arc spray (TWAS), and HVTS cladding, have been used for decades to impart wear, erosion, and corrosion resist - ance to components operating under aggressive service conditions. If unchecked, corrosion can lead to localised thinning, pitting, and ultimately premature failure of the pressure boundary, risking unplanned shutdowns and substantial repair costs

PTQ Q2 2026