API Strengthens Standard for Hydrofluoric Acid Alkylation Units

WASHINGTON, October 1, 2026 — The American Petroleum Institute (API) today announced the publication of the sixth edition of API Recommended Practice 751 (API RP 751), Safe Operation of Hydrofluoric Acid Alkylation Units. The updated standard revises requirements and recommendations for refineries that operate hydrofluoric acid (HF) alkylation units and includes strengthened provisions for mitigation-system reliability, mechanical integrity, turnaround practices and leak management.

Hydrofluoric acid is widely used as a refinery catalyst in the production of alkylate, a blending component in gasoline. Because HF is toxic and corrosive, refineries that operate HF alkylation units must carefully manage this hazard.

Since 1992, API RP 751 has provided a common industry framework for maintaining equipment integrity, preventing releases, protecting workers, managing HF transportation and inventory, and preparing mitigation and emergency-response systems.

“Safely managing hydrofluoric acid requires rigorous practices across every stage of an alkylation unit’s operation,” API Senior Vice President of Global Industry Services Anchal Liddar said. “The sixth edition of API RP 751 incorporates industry experience and lessons learned to strengthen operational safety and reliability.”

Developed through API’s open, consensus-based standards development process, the sixth edition builds on more than three decades of industry use and reflects operating experience, incident findings, Chemical Safety Board (CSB) recommendations and changes in broadly accepted industry practices.

Key updates to API RP 751 in the sixth edition include:

• Greater emphasis on the availability, reliability and formal testing of HF mitigation systems, including new mandatory analyses of backup-power and fireproofing needs;
• Stronger turnaround practices designed to help prevent onstream corrosion, including provisions addressing the removal of solids, sludge and water, and management of HF stored during turnarounds;
• Expanded controls for temporary leak repairs, incipient-leak recognition and monitoring, and first aid and medical response;
• Updated mechanical-integrity provisions addressing carbon-steel weld inspection, hydrogen-damage detection, elastomer selection, flange inspection, valve casting practices and maintenance-personnel qualifications;
• Stronger equipment-decontamination and maintenance practices, including work performed outside the HF alkylation unit; and
• Updated requirements and recommendations for HF unloading, utility isolation, product treatment and risk-mitigation system design.

Because API RP 751 serves as the foundation for API’s Process Safety Site Assessment Program’s (PSSAP®) RP 751 Assessment, the assessment schedule will be updated following a planned industry review and endorsement. Assessments to the sixth edition will begin in 2027.

A global working group of nearly 100 alkylation experts from countries including the United States, Canada, Germany, France, Belgium and the United Arab Emirates contributed to this sixth edition revision, reflecting the international use of HF alkylation technology.

The sixth edition of API RP 751 is available through the API Webstore: apiwebstore.org.

The American Petroleum Institute (API) represents all segments of America’s oil and natural gas industry, supporting nearly 11 million U.S. jobs. With approximately 600 members, API companies produce, process, and distribute the majority of the nation’s energy. Founded in 1919, API has developed over 800 standards to enhance operational and environmental safety, efficiency, and sustainability.

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