 June 13, 2013, the Williams-Geismar Oliphant's plant in Geismar, Louisiana, a heat exchanger violently ruptured, causing an explosion and fire that killed two workers. The Chemical Safety Board launched an investigation, Process Safety Management Program Deficiencies at Williams, which set the stage for the incident. In particular, the CSB found that the heat exchanger had failed was completely isolated from its pressure relief valve. When pressure inside the heat exchanger dangerously increased, there was nothing to stop a catastrophic rupture. The Williams-Geismar Oliphant's plant is located in Geismar, Louisiana. The plant produces ethylene and propylene. These are chemicals used in the petrochemical industry to make a variety of products including plastics and antifreeze. Within the Williams process is a distillation column called the propylene fractionator. It separates a mixture of propane and propylene. Heat exchangers called reboilers supply heat to the fractionator to boil the propane and propylene mixture, which is essential to the separation process. The reboilers are shell and tube heat exchangers. Hot water flows through the tubes, heating and vaporizing propane that flows through the shell and back to the propylene fractionator. The water that flows through the tubes contains a small amount of oily tar, which condenses into the water earlier in the process. Over time, the oily tar from the water builds up on the walls of the reboiler tubes. This buildup is called fouling. Fouling reduces the efficiency of the reboilers. Periodically, the reboilers must be shut down to clean the tubes. The original propylene fractionator design had both reboilers running simultaneously, but in that configuration, the fractionator had to be shut down when a reboiler fouled and needed cleaning. To prevent shutdown of the propylene fractionator each time the reboilers needed to be cleaned, in 2001, new valves were installed on each reboiler to allow for operation of only one at a time. The other reboiler is on standby, clean and ready for use. But unforeseen at the time, these valves introduced a serious hazard. They isolated the standby reboiler from its protective pressure relief valve located on top of the fractionator. On June 13, 2013, during a daily meeting with operations and maintenance personnel, the Williams plant manager noticed that the water flow rate through the operating reboiler had dropped gradually over the past day. The operation supervisor informed the group he would try to identify the problem. He went into the plant to evaluate the water flow rates. The operation supervisor informed several personnel that fouling within the operating reboiler could be the problem and they might need to switch the reboilers. He attempted to meet with his manager so they could get the necessary maintenance and operations personnel involved who would perform the work. But his manager was not available. The operation supervisor returned to the field. The CSB determined that at 8.33 a.m. the operation supervisor likely opened the water valves on the standby reboiler. Hot water began flowing inside. The valves blocking the reboiler from its protective pressure relief valve remained closed. But unknown to the operation supervisor, the standby reboiler contained flammable liquid propane that had accumulated during the 16 months the reboiler was out of service. The hot water quickly heated the liquid propane confined inside of the reboiler and pressure dangerously increased. Just three minutes later, the reboiler violently ruptured. Propane exploded from the reboiler and ignited to create a massive fireball. The explosion killed the operation supervisor and an operator working nearby. 167 Williams employees and contractors reported being injured. During its investigation, the CSB found that prior to the explosion the standby reboiler had been out of service for over a year, isolated from the process by closed block valves. But during this 16-month period, liquid propane unintentionally entered the shell of the reboiler, perhaps through a mistakenly opened valve or a leaking block valve. The CSB determined that when the operation supervisor opened the hot water valves to the standby reboiler, the propane liquid trapped inside was heated and expanded in volume to completely fill the reboiler shell. This caused pressure to dramatically increase until the reboiler ruptured. The CSB discovered that in the 12 years leading to the incident, a series of process safety management program deficiencies caused the reboiler to be unprotected from over pressure. When Williams installed the process block valves on the reboilers in 2001, they performed a management of change review to identify how this action affected the safety of the process. The CSB found, however, that Williams did not identify that the new valves could isolate the reboilers from their protective pressure relief valve. Companies are required to conduct a management of change review before making equipment changes, so they may consider the impact of that change on the safety of the process. But the CSB discovered that Williams conducted the management of change review after the process was already operating with the new valves. After the 2001 reboiler valve installation, Williams also performed a pre-start-up safety review as required by regulations. But the CSB found that Williams reviewers did not respond to key process safety questions on the form. One of those questions asked, are pressure relief systems in place and operational? That answer was left blank. The CSB found that in the following 10 years, Williams performed three process hazard analyses, or PHAs, in 2001, 2006, and 2011. None of the PHAs sufficiently identified or controlled the reboiler overpressure hazard. An internal recommendation from the 2006 PHA stated, consider locking open at least one of the manual valves associated with each of the propylene fractionator reboilers. While that recommendation was marked as complete, the CSB found that it was not implemented as intended. And the CSB found that Williams failed to develop a procedure for activities performed on the day of the incident. As following in the quench water system was a known issue, Williams should have had a written procedure to assess fouling and switch the reboilers. Furthermore, the company could have established a routine maintenance schedule to prevent extensive fouling in the first place. To prevent future incidents and further improve process safety at the Geismar plant, the CSB recommended that Williams conduct safety culture assessments that involve workforce participation and communicate the results in reports that recommend specific actions to address safety culture weaknesses. Develop a robust safety indicators tracking program that uses the data identified to drive continual safety improvement and perform comprehensive process safety program assessments to thoroughly evaluate the effectiveness of the facility's process safety programs. In its case study, the CSB encourages companies from across the country to review and incorporate the safety lessons and recommendations from the Williams-Geismar plant investigation within their own facilities.