A weak process safety culture contributed to two sulfuric acid releases at the Tesoro Refinery in Martinez, Calif., in 2014, as well as to the recurrence of sulfuric acid incidents that caused worker injuries over several years, says the U.S. Chemical Safety Board. In its final report, the CSB cites key process safety findings related to safety culture, safety indicators and the continued need for a proactive regulator to conduct preventive inspections.

On February 12, 2014, an incident occurred that burned two workers and released an estimated 84,000 pounds of sulfuric acid. Less than a month later on March 10, sulfuric acid sprayed and burned two contract workers during the removal of piping. Both incidents occurred in the refinery’s alkylation unit, where high octane blending components are produced for gasoline.

The investigation, which included an evaluation of previous incidents and worker statements, found a number of safety culture concerns at the refinery, including:

  • Characterization of the February 2014 incident as a minor injury. The incident should have been classified as the most serious type of process safety incident under industry guidelines.
  • Exposure of alkylation unit workers to hazardous materials including vapors, acids and corrosives.
  • Removal of safer sulfuric-acid-sampling systems from service and reliance on inadequate temporary alkylation unit equipment.
  • Failure to provide alkylation unit workers with necessary protective equipment.
  • Existence of site-specific safety policies that were less protective than corporate policies and established industry good practice.
  • Failure to develop an action plan to address concerns identified in a 2007 safety culture survey.
  • Withdrawal from key national safety programs that workers believed were effective.
  • Perceived pressure on alkylation unit workers to expedite training and reduce cost.

Following the investigation, the CSB recommended changes to strengthen refinery regulations in California. As a result, the state issued a draft refinery process safety management standard containing more rigorous safety regulations for the oversight of petroleum refineries. The CSB’s Tesoro case study underscores the need for proposed refinery safety reforms as well as individual refineries to continually assess and improve their process safety programs.

The report also emphasizes that regulators can use what are known as lagging process safety indicators (e.g., spills, fires or gas releases) and leading indicators such as timely maintenance on safety critical equipment to focus inspections, audits and timely closure of action items resulting from incident investigations to drive process safety improvement.