NOTE: The sponsor of this content may contact you with more information on this topic. Click here to opt out from sharing your email address with this sponsor. (This link will not unsubscribe you from any other BIC email list).
HF (hydrofluoric acid) alkylation units are designed and operated around one priority: preventing a primary loss of containment of HF. The margin for error is narrow, and reliability directly affects both safety and profitability.
When an HF alkylation unit shuts down unexpectedly, the impact extends far beyond lost production. Shutdowns involve many complex steps and increase risk to both equipment and personnel. The restart that follows is equally demanding, requiring detailed procedures and careful execution. Avoiding unnecessary shutdown-startup cycles protects on-stream time, preserves margins and supports long-term unit integrity.
Proactive reliability keeps problems from developing in the first place. It shows up in the daily decisions teams make about how equipment is inspected, maintained, repaired and operated. So, what does this look like in practice?
What proactive HF alkylation reliability requires
Achieving best-in-class performance in HF alkylation units depends on disciplined focus in a number of critical areas:
- Flange integrity and inspection rigor
- High-integrity isolation capability
- Operation within clearly defined Integrity Operating Windows (IOWs)
- Inspection methods and material capability evaluation
- Data-driven reliability and early detection
- Effective turnaround execution
- Experience and work continuity
Each area plays a distinct role, but their effectiveness depends on how they are applied in practice and reinforced through day-to-day operation.
Flange integrity and inspection rigor
Leak prevention starts long before startup. Identifying a viable flange face requires skill. Tightly adhered iron fluoride scale can mislead an untrained technician into believing the surface is clean and suitable for reuse. Proper scale removal – without damaging the flange surface – requires specialized expertise.
Proper gasket selection using compatible materials is essential. Dry fitting the gasket and avoiding the use of paste or tape helps prevent the creation of leak paths for HF migration. A rigorous program must also ensure that every flange is properly torqued and re-torqued based on the selected bolting material (e.g., B7 vs. B7M).
Minor leaks are a reality in HF alkylation units. Addressing them quickly, before flange damage occurs, is critical. In some cases, re-torquing and evaluating bolt condition can stop an incipient leak. More advanced leaks may require clamping, which is itself a specialized technique and differs significantly from leak repair practices in other process units.
High-integrity isolation capability
When a leak occurs, the ability to isolate and repair without fully de-inventorying the HF alkylation unit often determines whether the event becomes a brief interruption or a prolonged outage. This makes isolation strategy critical to runtime performance.
Metal-seated gate valves, while commonly used due to cost, can present challenges when isolating equipment or piping. Iron fluoride scale can accumulate in the seat area, preventing full closure. Globe and plug valves generally offer better performance for isolating critical equipment such as exchangers and relief valves.
Operation within clearly defined IOWs
IOWs define the limits required to keep HF alkylation units operating safely.
Controlling water is one of the most essential IOWs for managing unit corrosion, and proper operation of the regenerator/rerun system needs to be guided by reliable laboratory analysis. IOW variables must also be consistently interpreted and acted upon across both operations and engineering teams.
Inspection methods and material compatibility evaluation
Aging HF alkylation units require inspection techniques that reflect actual field conditions as well as operational and inspection history. Using compatible materials, defining appropriate inspection scope, and conducting detailed component reviews all contribute to reducing degradation risk.
Inspection findings should inform capital planning and long-term strategy. Achieving this requires selecting inspection methods that align with expected damage mechanisms and unit-specific risk areas.
Inspection techniques must be appropriate for detecting localized corrosion. Questions remain around best practices – including the role of ultrasonic thickness (UT) thickness monitoring vs. multi-axis radiography, the use of fixed-location UT systems and how many monitoring points are needed (and where they should be placed) – to generate reliable, actionable data.
Material considerations are another critical part of this equation and continue to evolve. Concerns around residual element contamination in carbon steel persist, while greater attention is now being given to the effects of oxygen exposure on Monel Alloy 400. These factors must be incorporated into both inspection planning and material selection decisions.
Non-destructive testing of in-service equipment has never been more important. Effective programs combine the right technologies with experienced interpretation to ensure that degradation is identified early and managed before it threatens containment.
Data-driven reliability and early detection
Proactive reliability depends on what is inspected, but also on how information is used to anticipate problems before they escalate.
HF alkylation units generate large amounts of operating and inspection data, but value comes from connecting that data to actionable decisions. Trends in corrosion rates, changes in pressure drop, temperature deviations and analyzer results can all provide early indication of developing issues.
Effective programs define clear triggers for action. Rather than reacting only to threshold exceedances, leading organizations monitor rates of change and subtle deviations from normal operation. This allows teams to intervene before conditions challenge containment.
Instrumentation selection also plays a role. Technologies such as guided wave radar, online analyzers, magnetic level indicators, and advanced diagnostics can improve visibility into unit health when applied appropriately. However, tools alone are not enough; interpretation and response discipline ultimately determine effectiveness.
Data-driven reliability helps close the gap between inspection intervals by strengthening confidence in operating decisions and reducing the likelihood of unexpected events.
Effective turnaround execution
Turnarounds are among the highest-risk and highest-impact activities in HF alkylation units. They present a critical opportunity to restore integrity, but only when executed with discipline at every stage.
Execution begins with effective scope challenge. Not all identified work should automatically be included, and not all risks are visible without careful review. Scope decisions must be grounded in inspection data and known damage mechanisms, supported by operating history. Over-scoping introduces unnecessary risk and complexity, while under-scoping allows degradation to persist undetected.
Careful planning follows. HF alkylation units require detailed coordination across operations, maintenance, engineering and safety teams. Chemical neutralization and cleaning must be carefully planned and executed, with the appropriate technology selected, to ensure the unit is safe for entry and work. Residual HF, iron fluoride scale, and acid-soluble oils (ASO) present hazards that demand strict adherence to proven procedures.
Disassembly and reassembly work, including required repairs, must be carried out by a skilled workforce familiar with HF alkylation service requirements. This includes proper handling of components, protection of flange surfaces, correct gasket selection, and precise bolting practices. Work quality during this phase directly determines post-turnaround reliability.
HF safety awareness is essential throughout execution. Personnel must understand not only standard safety protocols, but also the specific risks associated with HF exposure and mitigation systems. Experienced supervision and verification at each step help ensure that critical details are not missed.
Water removal from the unit prior to start-up is a critical step to minimize the potential for dead-leg corrosion during operation. This requires coordination between inspection and operations group for identification and management of dead-leg systems.
Effective turnaround execution in HF alkylation units reduces early-life failures and supports longer run lengths – ultimately reinforcing overall unit reliability.
Experience and workforce continuity
Most HF alkylation units have been operating for decades, and much of the knowledge required to run them effectively is transitioning out of the workforce. Training budgets are often the first to be cut, which exposes an organization to real-time risk.
Without structured mentoring and meaningful training and qualification programs, that loss of experience can directly affect reliability and safety. Performance is often tested during off-hours and under pressure, and equipment integrity ultimately depends on the people making decisions in those moments.
Where industry alignment really matters
API RP 751 remains the industry’s core guidance for HF alkylation. Now in its 6th Edition revision cycle, it continues to raise expectations around safeguards and inspection.
Most facilities have assessed their HF alkylation units against RP 751 at least once. However, the quality of these assessments depends heavily on the expertise of the assessors, and audits alone are only one part of safe and reliable operation. A periodic audit is no substitute for a knowledgeable internal team capable of maintaining performance between the three-year audit cycle.
While RP-751 provides important direction, it cannot address every day-to-day operating challenge or capture the full range of field experience. Across the industry, detailed operating insights are not widely shared. Companies rarely publish the full context behind internal events, and incident databases offer limited visibility. As a result, lessons are often learned within individual organizations rather than across the industry.
This is why direct peer exchange is so valuable. Progress accelerates when professionals openly compare approaches, such as:
- How are others managing 100% component inspection scope?
- What strategies are being used for positive isolation?
- How are meaningful IOWs defined and implemented?
- Are alternate instrument technologies such as guided wave radar being applied?
- What options exist for ASO disposal?
- Is anyone alkylating C5 olefins and what are the challenges?
These discussions provide insights that standards alone will not be able to capture.
Continuing the conversation at the HF Alkylation Summit
The Becht HF Alkylation Summit 2026 will extend this level of exchange into a focused setting. Following the strong response to the inaugural Summit in 2024, the event returns in 2026.
Taking place September 21–24, 2026, in Houston, the Summit brings together technical and operations professionals responsible for HF alkylation unit performance. The agenda will explore practical drivers of reliability, including:
- Inspection scope decisions
- Machine learning and advanced control
- Mitigation expectations and strategies
- Aging unit performance
- Emerging technologies
- Legislative actions seeking to ban HF use
- Early insight into API RP 751, 6th Edition
These are the issues that operators face every day – and that will be discussed openly at the Summit. The program combines technical presentations with extended Q&A sessions, allowing participants to explore real-world challenges in depth.
Proactive reliability in HF alkylation units depends on disciplined equipment care and consistent adherence to defined operating limits. It also depends on transferring hard-earned knowledge to the next generation of engineers and operators. The Becht HF Alkylation Summit provides a forum to examine these challenges directly and share the insights that strengthen reliability before problems develop.
Registration is open now, with early-bird rates available through April 30.
For more information and to register, visit the event website here.
