PTQ Q2 2026 Issue

Mitigation options comparison

HCF tower #1

S/No.

Mitigation options

Relative cost index *

Relative schedule impact

1 2 3

CS tower top replacement with Incoloy 825 cladding CS internal weld overlay with Incoloy 825 cladding

2.1× baseline 1.9× baseline 1.0 (baseline)

+43% +71%

HVTS

Baseline

Tail gas unit quench tower #2

1 2 3

CS tower replacement with SS316L CS internal weld overlay with SS316L

~2.0× baseline ~2.3× baseline 1.0 (baseline)

+51%

+170% Baseline

HVTS

EKT quench tower #3

Weld overlay

~8-9× baseline 1.0 (baseline)

~2.5× baseline

HVTS

Baseline

* Baseline = HVTS

Table 1

Among these, HVTS stands out because it uses high- velocity metallic alloy particles accelerated toward a pre- pared substrate. Upon impact, they flatten and bond mechanically, forming a dense, low-porosity metal-based cladding that can approximate the performance of wrought corrosion-resistant alloys (CRAs). HVTS cladding is particularly effective in aggressive acid/ chloride/CO₂/H₂S environments typical of oil and gas, pet - rochemical, and refining processes. Key application benefits include: • Low heat input: HVTS application does not raise sub- strate temperature significantly (typically below ~120°C), avoiding heat-affected zones (HAZ) and eliminating the need for PWHT. • Rapid execution: Spray deposition rates allow coverage of several square metres per shift, enabling large-area rehabilitation within tight turnaround windows. • Durable corrosion barrier: Use of high-nobility alloys results in long-term resistance, with service life often exceeding 10-15 years under aggressive service conditions. • Reduced lifecycle costs: Compared to weld overlay or replacement, HVTS often provides 30-50% cost savings in material and labour and reduces shutdown duration. • Flexibility and minimal downtime: No curing time or bake-out is needed (unlike organic coatings), and clad- ding is insensitive to ambient temperature/humidity, facil- itating deployment during turnaround or even emergency shutdown.

These advantages make this durable corrosion barrier a compelling choice for upgrading critical refinery/tower internals, especially in acid service quench towers. Corrosion challenge Spanning two operating sites, the integrated refinery and chemical complex processes more than half a million bar- rels per day and is closely linked with downstream chem- ical production. The petrochemical complex was originally commissioned in the early 2000s and has since undergone multiple major expansions, significantly increasing capac - ity. Further downstream integration was achieved through the addition of large-scale aromatics and speciality elasto- mer production units. The chemical facilities include a world-scale ethylene cracker with an annual capacity approaching two million tonnes, supporting the production of a broad portfolio of commodity and performance materials. Outputs include plastics, elastomers, resins, aromatics, and oxo-based products used in a wide range of everyday applications, such as automotive components, personal care products, and food packaging. The plant follows a predictive maintenance strategy grounded in risk-based inspection (RBI) and reliabili- ty-centred maintenance (RCM), with major turnarounds scheduled approximately every four to five years. A routine thickness monitoring (part of RBI) identified localised metal loss in the EKT quench column, tail gas unit column, and the HCF tower, around the shell and nozzles. Left unaddressed, projections further indicated thinning rates that could breach safety margins before the next scheduled turnaround, posing a risk to pressure boundary integrity and potential unplanned shutdowns. In addition, the observed damage was consistent with localised corro- sion mechanisms that are difficult to mitigate through con - ventional coatings or short-term repairs, particularly under fluctuating process and thermal conditions. Technical via - bility, cost, and schedule were considered when selecting an appropriate corrosion mitigation solution for HCF tower #1, tail gas quench unit tower #2, and EKT quench tower #3, as shown in Table 1 .

Indicative pitting resistance of common corrosion-resistant alloys *

Alloy

Relative pitting resistance

Inconel 690 65/35 NiCr Inconel 625

Moderate

Moderate-high

High

Hastelloy C-276

Very high

High-nobility nickel-based CRA

Extremely high

(HVTS system) *Alloy enhancements vary by supplier and application.

Table 2

PTQ Q2 2026