The American Petroleum Institute (API) has published the sixth edition of API Recommended Practice 751, revising safety requirements and operational guidance for refineries that operate hydrofluoric acid alkylation units. The updated standard strengthens provisions covering mitigation-system reliability, mechanical integrity, maintenance and turnaround activities, and the management of leaks. It incorporates operating experience, incident findings and changes in accepted industry practices to support safer and more reliable refinery operations.
Hydrofluoric acid (HF) is used as a catalyst in alkylation units to produce alkylate, a component used in gasoline blending. Since HF is toxic and corrosive, facilities using it must maintain controls to prevent releases and protect workers. API RP 751 has provided guidance for the industry since 1992, addressing equipment integrity, release prevention, worker protection, HF transportation and inventory management, and emergency-response systems.
The sixth edition places greater emphasis on the availability and reliability of HF mitigation systems, including formal testing. It also introduces mandatory analyses of backup-power and fireproofing requirements. Updated turnaround provisions address the management of solids, sludge, water and HF stored during maintenance periods.
The revised practice expands guidance on temporary leak repairs, early identification and monitoring of leaks, and first aid and medical response. Mechanical-integrity provisions have also been updated to cover carbon-steel weld inspection, hydrogen-damage detection, elastomer selection, flange inspection, valve casting practices and the qualifications required for maintenance personnel.
Further revisions address equipment decontamination and maintenance, including work performed outside the HF alkylation unit. The standard also updates provisions relating to HF unloading, utility isolation, product treatment and the design of risk-mitigation systems.
Anchal Liddar, Senior Vice President of Global Industry Services at API, said the revised edition incorporates industry experience and lessons learned to strengthen operational safety and reliability. She emphasised the need for rigorous practices throughout the operation of hydrofluoric acid alkylation units.
Nearly 100 alkylation specialists from the United States, Canada, Germany, France, Belgium and the United Arab Emirates contributed to the revision. According to API, the updated document draws on operating experience, incident investigations, recommendations from the US Chemical Safety Board and changes in widely accepted industry practices.
API RP 751 is intended to provide refineries with a framework for reviewing and improving safety practices across the operating life of HF alkylation units. The latest edition updates the guidance available to operators responsible for managing HF-related hazards, maintaining equipment and ensuring that mitigation and emergency-response systems remain effective. The revised practice also supports assessments conducted under API’s Process Safety Site Assessment Program, which uses RP 751 as part of its evaluation framework.
