It just seemed like a good idea. Instead of running two reboilers at the same time and shutting down the process when they fouled, why not operate one at a time and when one fouls, start up the other. Then you can perform maintenance on the off-line reboiler. In this way, the process can keep operating in a continuous fashion.
The Williams Olefins workers at the Geismar, Louisiana plant would only have to add a few valves so that one reboiler could operate while the other was closed off and kept idle until needed. A simple, smart business decision -- or so it seemed.
However, Occupational Safety and Health Administration (OSHA) Process Safety Management and Environmental Protection Agency (EPA) Risk Management Program regulations require chemical process facilities to conduct a Management of Change (MOC) review before making a change, such as changes in equipment, to a covered process.
A facility’s MOC review should consider the impact of the change on safety and health, and should consider whether operating procedures need modifications. OSHA and EPA also require companies to train affected employees on the change prior to startup. These disciplined approaches to safety provide the pillars for conducting a robust safety investigation.
In 2001, 12 years before the deadly explosion June 13, 2013, killed two workers and injured 167 others in a catastrophic equipment rupture, explosion, and fire at the plant, Williams Olefins performed a MOC to address the installation of valves on six quench water heat exchangers, including the propylene fractionator Reboilers A and B.
Williams Olefins’ MOC process required operations, maintenance, technical, environmental, safety, and project engineering departments to consider the safety implications of installing the valves.
They complied by answering checklist questions used to prompt a targeted analysis for each department. Department managers were asked to respond to each prompt by checking “yes,” “no,” or “n/a” (not applicable). By filling out and processing such a checklist, it would be possible to address design safety issues before making the change
While MOC checklists can ensure consideration of common hazards and typical change requirements, the Williams Olefins MOC reviewers did not identify the serious overpressure hazards introduced by installing valves on the reboilers.
The goal behind the MOC process was to identify and control all possible hazards. Unfortunately, Williams Olefins did not perform an MOC before installing and commissioning the new block valves. Instead, the MOC was performed after the plant was operating with the new valves. The MOC was used as a tool to address a regulatory requirement rather than to identify potential process hazards.
Installing block valves into a process where they previously did not exist is a significant process change that needs careful safety analysis, one that often should involve the services of a certified safety provider.
In retrospect, the Williams Olefins MOC was flawed and overlooked several risks:
In addition to the MOC, following the installation of the propylene fractionator Reboiler A and Reboiler B valves, Williams Olefins performed a Pre-Startup Safety Review (PSSR) as required by process safety management regulations. Conducting the Williams Olefins PSSR required filling out a 21-question form. Williams Olefins reviewers either did not answer or incorrectly answered key PSSR process safety questions.
PSSRs represent an opportunity to verify effective implementation of design intent, accuracy of process safety information, and proper installation and configuration of equipment. Companies should conduct thorough and effective PSSRs before starting up.
Bringing in a safety consultant during the MOC and PSSR processes could have nullified hazards that Williams Olefins unwittingly introduced and did not fully understand.
In order to find out how some of the various mistakes that occurred over time should have been addressed and prevented, click here.