Protecting Process Vessels from Corrosion
Understanding the Challenge
Process vessels, towers, and columns are mission-critical equipment in oil and gas plants. These assets operate under extreme conditions – elevated temperatures, high pressures, and constant exposure to aggressive, corrosive chemicals. Corrosion and metal wastage are the primary causes of process disruption and costly downtime.
Unique factors compound the challenge in African markets. Many facilities operate well beyond their original design life due to capital constraints for replacements. Additionally, the harsh climates across the continent, from coastal humidity to desert heat, accelerate corrosion mechanisms. A typical refinery in South Africa reports that nearly 50% of corrosion incidents occur in the hottest parts of plants, particularly in reboilers and regenerators.
Asset failures resulting from corrosion have a significant financial impact. Industry reports show that unplanned shutdowns can cost facilities between $1.2 million and $3 million per day. For African operations where supply chains may face additional logistical challenges, these costs can escalate quickly as replacement equipment often requires extended lead times.
Approaches to Protect Equipment from Corrosion
Several viable solutions exist to address corrosion through Corrosion Resistant Alloy (CRA) barriers. The optimal technique depends largely on available shutdown time and budget constraints.
Welding has been traditionally used for rebuilding degraded areas and providing corrosion-resistant barriers. However, this approach can have drawbacks including shell distortion from heat input, added stress (especially on thinner vessels), and potential requirements for heat treatment. Most importantly, welding is relatively slow at 1-1.5m² per weld head per shift, extending critical path timelines and delaying return to service.
Organic Epoxy (Non-metallic) Coatings offer another option but come with temperature limitations (typically below 140°C/284°F.), vulnerability to mechanical damage, and strict environmental control requirements during application. While initially cost-effective, these coatings often experience repeated failure and require frequent reapplication in harsh process environments.
HVTS® (High Velocity Thermal Spray) technology has emerged as a proven solution. Unlike conventional thermal spray methods, which can produce permeable cladding susceptible to premature failure, advanced HVTS applies non-porous high-nobility metal alloys that form an excellent bond strength (>83 MPa) with the base metal. The process is considerably faster than welding (3-6m² per shift/machine)with no stress imposed on the base material, no heat-affected zones, and no dilution issues.
HVTS cladding delivers high corrosion and erosion resistance, withstands temperatures above 500°C, requires no curing, and remains mechanically tough throughout its service life. Importantly, it allows for external inspection during normal operations, a critical advantage for ongoing asset integrity management.
Case Study
South African Pressure Vessel Corrosion Mitigation in Olefin Production
A South African oil and gas company faced critical asset integrity challenges in its olefin production vessels. The plant experienced excessive pitting and cracking due to hydrogen-induced corrosion (HIC) and stress corrosion cracking (SCC). Traditional weld overlay repairs were slow and expensive, resulting in millions of dollars in standby costs.
In 2017, HVTS technology was applied to protect 129m² of critical surfaces across multiple vessels, including a feed surge drum, coolers, a quench tower, a condenser, and a stripper column. The application was completed on a 24-hour basis to minimize downtime.
Four years later, a 2021 inspection found 100% cladding in excellent condition with no indication of thickness loss. This eliminated the need for additional repairs during the scheduled turnaround, reducing critical path days from 36 to 25 – a significant operational advantage that translated directly to increased production and profitability.
This successful implementation demonstrates how advanced corrosion protection technologies can significantly extend asset life while reducing maintenance costs and unplanned downtime – important considerations for optimizing operations in conditions where maximizing asset longevity delivers substantial competitive advantages.
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