Refinery turnarounds require operators to make difficult decisions within a fixed time period and constrained budget. U.S. Energy Information Administration data shows that refinery utilization averaged approximately 89% between 2014 and 2023, with planned maintenance, unforeseen disruptions and safety considerations among the factors affecting production rates.

When maintenance requirements exceed available funding, process safety and the work required to maintain availability come first at a refinery. The longer-term projects addressing corrosion, fouling, energy efficiency and gradual performance loss must compete for the remaining budget, even where delaying intervention may increase future maintenance requirements.

This creates an important question for downstream operators. If work can safely be deferred today, at what point does postponement become a larger reliability and maintenance requirement for refineries in the future?

Annual budgets and lifecycle costs

Lifecycle costing is well understood across the downstream industry, but maintenance decisions are still largely made within annual budgets, yet equipment is expected to operate for decades. The disconnect becomes more pronounced when market conditions change operating priorities. This year, for example, supply disruptions are contributing to unusually high U.S. refinery runs, as stronger margins and export demand encourage operators to maximize available capacity.

Corrosion, however, does not follow a financial year. Once degradation is identified in pipelines or equipment, engineers must assess the extent and rate of metal loss, remaining wall thickness, operating conditions and the risk of failure to determine whether the asset can safely operate until the next planned intervention. A lower-cost repair may be appropriate, but the assessment should also consider whether the same area will require further inspection, access or repair at subsequent turnarounds.

As refinery infrastructure ages and reaches its original design life, equipment does not necessarily become unserviceable. Well-managed assets can continue operating safely for many years. However, changes in feedstock, throughput or process duty can introduce new corrosion risks. For example, switching from sweeter to more sulfur-rich crude can increase the risk of high-temperature sulfidation, accelerating metal loss in susceptible piping and equipment. Higher operating temperatures or changes in flow conditions can further influence where and how quickly degradation occurs.

Equipment lifecycle decisions in refineries should therefore consider both asset condition and whether the current service budget still reflects the environment and operating conditions behind the original maintenance strategy. The challenge is ensuring that a decision which makes commercial sense within one budget cycle remains economic over the remaining life of the asset.

Inspection does not always reveal the full picture

Inspection and condition monitoring give downstream operators a strong understanding of equipment condition, but not every issue can be fully characterized while an asset remains online. Wall-thickness measurements, process data and other techniques may identify material loss, but its full extent can only be understood once equipment is opened and internally inspected.

Corrosion must also be assessed by its underlying damage mechanism, rather than simply by the amount of metal already lost. Different mechanisms, such as chloride-induced pitting, high-temperature oxidation and erosion-corrosion, can produce different patterns and rates of degradation. For example, chloride contamination can cause localized pitting in susceptible alloys, while high-velocity flow containing abrasive particles can accelerate metal loss at bends and other areas of turbulence. Understanding the mechanism and the operating conditions that influence it helps engineers predict where further damage may occur and select an appropriate mitigation strategy.

Amine systems, which remove corrosive acid gases from process streams, provide a good example. Corrosion is not typically caused by the amine itself, but by dissolved acid gases, degradation products and contaminants. For example, heat-stable salts can increase solution corrosivity, while high flow velocities and turbulence can accelerate localized metal loss. Sudden pressure reductions can also cause dissolved acid gases to break out of solution, increasing corrosion risk in affected areas. Repairing damaged equipment without addressing these underlying conditions may leave it vulnerable to further degradation.

Inspection should therefore establish more than fitness for continued service. The scope and methods will vary depending on the equipment, operating conditions and suspected damage mechanisms. For example, in a process vessel, visual inspection may identify areas of localized corrosion, while ultrasonic thickness measurements can quantify wall loss and identify areas approaching minimum allowable thickness. Comparing these findings with previous inspection records helps engineers estimate corrosion rates, assess remaining service life and determine whether repair, additional monitoring or replacement is required before the next planned maintenance interval.

Planning for a scope that can change

Refinery turnarounds are planned years in advance, but the final maintenance scope cannot always be determined until equipment is opened. Even when inspection history and condition data provide a strong basis for planning, have a plan for discovery work.

When additional degradation is identified, the decision should consider:

• the extent and expected progression of degradation
• whether operating conditions have changed from the original design basis
• whether localized repair or wider protection is more appropriate
• the effect of each option on turnaround time and future maintenance
• The lifecycle cost of the available approaches.

The difficulty is that these decisions are often made when much of the budget is already committed, contractors are mobilized and the startup date is fixed. There may be several technically acceptable options, but not all will be practical within the remaining window.

Effective turnaround planning therefore requires flexibility to accommodate unexpected findings without compromising safety or unnecessarily extending the shutdown. This can be achieved by engaging contractors early to identify potential repair scenarios, agree on contingency plans and establish access to specialist resources and equipment. Where unexpected corrosion or damage is discovered, having suitable repair options and decision-making processes already in place allows teams to respond quickly. They can consider the equipment's condition, expected service life and future maintenance requirements, rather than simply selecting the fastest available repair.

When the scope changes during the turnaround

A recent turnaround at a long-established 120,000 bpd refinery in Saudi Arabia illustrates how this works in practice. An initially limited corrosion mitigation scope expanded as equipment was opened and additional degradation was identified across several columns, vessels and a process drum. The additional work had to be incorporated into the existing schedule, requiring decisions on the appropriate intervention for each affected area as startup approached.

The condition of the base material was central to that decision. Where sufficient wall thickness remains, a corrosion-resistant alloy cladding can protect the existing pressure boundary from further degradation. Where material loss is more advanced, welding may first be required to restore the base material before protective cladding is applied. The appropriate approach therefore depends on equipment condition and the degradation mechanism, not execution time alone.

In this case, high velocity thermal spray (HVTS) alloy cladding was selected for areas within the expanded scope. The initial requirement of 30 m² increased to 256 m² across eight refinery vessels as additional corrosion was identified during inspection. The work was completed over a 33-day project period, within the refinery's allocated turnaround schedule.

The ability to complete additional work within a tight turnaround schedule need not compromise long-term reliability. In suitable applications, HVTS provides durable corrosion protection and requires less application time than conventional weld overlay. This allows operators to address unexpected corrosion findings without necessarily extending the shutdown or creating additional maintenance requirements at future turnarounds.

Using turnaround time more effectively

Once equipment has been isolated, prepared and made available for inspection, access itself has an economic value. If deterioration is identified, the assessment should consider not only the immediate repair requirement, but also the cost and complexity of returning to the same equipment at a future outage.

Scaffolding, cleaning, isolation, inspection and mechanical preparation can make repeated access considerably more expensive than the repair itself. In some cases, addressing a wider area during the current turnaround may therefore reduce future maintenance requirements. In others, continued monitoring will remain the appropriate engineering decision.

Repair selection depends on the condition of the equipment, the corrosion mechanism and the available maintenance window. Where wall thickness is below the required minimum, welding may be needed to restore the base material before corrosion protection is applied. Where sufficient thickness remains, HVTS alloy cladding may provide an alternative to weld overlay without the associated heat input or post-weld heat treatment. The appropriate method should also account for surface preparation, inspection requirements and expected service life.

At the Saudi refinery, for example, one process drum required weld build-up to restore areas affected by shell thinning before HVTS was applied for corrosion protection. This allowed the structural repair and protective cladding to address different requirements within the same turnaround.

Efficiency has to compete with availability

Energy efficiency presents another way to assess production performance, as efficiency can decline without affecting the immediate ability of equipment to operate. A fired heater, used to heat process fluids to the temperatures required for refining operations, may continue meeting its process duty while consuming more fuel or losing available firing capacity, making intervention easier to defer.

Fired heaters need to be assessed individually, as process duty, burner configuration, tube arrangement and heat recovery vary between assets. For example, fouling in the convection section can restrict heat transfer, increasing stack temperature and fuel consumption. The appropriate cleaning method depends on tube accessibility, deposit characteristics and the heater's operating conditions. Assessing these factors helps operators determine the most effective intervention and whether cleaning can be completed online or requires a planned shutdown.

This helps explain why efficiency projects with a sound return on investment can still struggle for turnaround funding. Where a heater remains operational, incremental performance losses will generally carry less immediate weight than work required to maintain production.

The case for intervention therefore needs to extend beyond fuel savings alone. Throughput, available firing capacity, emissions, operating cost and the effect of degradation on future maintenance all contribute to the economic assessment of efficiency improvements.

Taking a longer-term view

Safety and production availability will continue to determine refinery turnaround priorities. The challenge is to ensure that necessary short-term decisions remain appropriate when considered over the remaining life of the asset.

Deferring corrosion, fouling or performance-related work may be the right decision, given the likely damage progression and future maintenance plans. For downstream operators managing assets over several decades, the question is not simply whether equipment can continue operating, but when intervention will deliver the best technical and economic outcome.