Contributory Factors: Maintenance

Six workers were fatally injured during a planned work activity to clean debris from natural gas pipes at Kleen Energy in Middletown, CT. To remove the debris, workers used natural gas at a high pressure of approximately 650 pounds per square inch. The high velocity of the natural gas flow was intended to remove any debris in the new piping. During this process, the natural gas found an ignition source and exploded.

KEY ISSUES:
• SIMILAR NATURAL GAS BLOW INCIDENTS
• INDUSTRY PRACTICES AND SAFER ALTERNATIVE METHODOLOGIES
• HAZARDS OF RELEASING NATURAL GAS NEAR WORK AREAS
• CODES AND STANDARDS

ROOT CAUSES:
1. Natural gas blows are common
2. Workers remained in building during gas blow

Image credit: CSB

On Wednesday, February 8, 2017, at approximately 11:05 am, a foul condensate tank, part of a non-condensable gas system, exploded at the Packaging Corporation of America (PCA) containerboard mill in DeRidder, Louisiana. The explosion killed three people and injured seven others. All 10 people were working at the mill as contractors. The explosion also heavily damaged the surrounding process. The foul condensate tank travelled approximately 375 feet and over a six-story building before landing on process equipment.

At the time of the incident, the mill was undergoing its annual planned maintenance outage, also referred to as a shutdown. The foul condensate tank likely contained water, a layer of flammable liquid turpentine on top of the water, and an explosive vapor space containing air and flammable turpentine vapor.

KEY ISSUES:
• PROCESS SAFETY MANAGEMENT SYSTEM
• INHERENTLY SAFER DESIGN
• PROCESS HAZARD ANALYSIS
• INEFFECTIVE SAFEGUARDS
• HOT WORK SAFETY MANAGEMENT

ROOT CAUSES:
1. PCA did not evaluate the majority of the non-condensable gas system, including the foul condensate tank, for certain hazards. The DeRidder mill never conducted a process hazard analysis to identify, evaluate, and control process hazards for the non-condensable gas system.
2. PCA did not expand the boundaries of its process safety management program beyond the units covered by safety regulations.
3. PCA did not effectively apply the hierarchy of controls to the selection and implementation of safeguards that the company used to prevent a potential non-condensable gas explosion.
4. PCA did not evaluate inherently safer design options that could have eliminated the possibility of air entering the non-condensable gas system, including the foul condensate tank.
5. PCA did not establish which mill operations group held ownership of, and responsibility for, the foul condensate tank.
6. PCA did not apply important aspects of industry safety guidance and standards.

Image credit: CSB

On February 12, 2014, a mechanical integrity failure released sulfuric acid in the alkylation unit, which burned two Tesoro Martinez refinery employees. Approximately 84,000 pounds of sulfuric acid were released during the incident.

On March 10, 2014, sulfuric acid sprayed and burned two contract workers while they removed piping in the same alkylation unit. The CSB found that this second incident shared similar causation with a 1999 incident at the same refinery, then called the Avon refinery, owned by the Tosco Corporation, that resulted in four fatalities. Similarities between the two incidents suggest that the Tesoro Martinez refinery did not effectively continue to implement or communicate important safety lessons from the 1999 Tosco incident.

KEY ISSUES:
• PROCESS SAFETY CULTURE
• PROCESS SAFETY INDICATORS

ROOT CAUSES:
1. The safety culture at the Tesoro Martinez refinery created conditions conducive to the occurrence and recurrence of process safety incidents that caused worker injuries at the refinery over several years.
2. Prior sulfuric acid exposure incidents at the Tesoro Martinez refinery could have properly been considered leading indicators of an impending serious chemical accident and then triggered preventive inspections and review of the refinery’s safety systems and equipment.

Image & AcciMap Credit: CSB

Image credit: CSB

On Wednesday, February 18, 2015, an explosion occurred in the ExxonMobil Torrance, California refinery’s Electrostatic Precipitator (ESP), a pollution control device in the fluid catalytic cracking (FCC) unit that removes catalyst particles using charged plates that produce sparks (potential ignition sources) during normal operation. The incident occurred when ExxonMobil was attempting to isolate equipment for maintenance while the unit was in an idled mode of operation; preparations for the maintenance activity caused a pressure deviation that allowed hydrocarbons to backflow through the process and ignite in the ESP.

The CSB found that this incident occurred due to weaknesses in the ExxonMobil Torrance refinery’s process safety management system. These weaknesses led to operation of the FCC unit without pre-established safe operating limits and criteria for unit shutdown, reliance on safeguards that could not be verified, the degradation of a safety-critical safeguard, and the re-use of a previous procedure deviation without a sufficient hazard analysis that confirmed that the assumed process conditions were still valid. .

KEY ISSUES:
• LACK OF SAFE OPERATING LIMITS & OPERATING PROCEDURE
• SAFEGUARD EFFECTIVENESS
• OPERATING EQUIPMENT BEYOND SAFE OPERATING LIFE
• RE-USE OF PREVIOUS PROCEDURE VARIANCE WITHOUT SUFFICIENT HAZARD ANALYSIS

ROOT CAUSES:
1. ExxonMobil did not establish the safe operating limits for operating the FCC unit in Safe Park (a standby mode of operation) or determine process conditions that required unit shutdown.
2. ExxonMobil did not perform a sufficient hazard analysis to determine if the unit conditions specified in the 2012 procedure were valid for the 2015 operation.
3. ExxonMobil operated FCC unit equipment beyond its predicted safe operating life.
4. ExxonMobil lacked safety instrumentation to detect flammable hydrocarbons flowing through the equipment and into the ESP.
5. ExxonMobil refinery management permitted opening process equipment without conforming to refinery standards.

Image credit: CSB

On February 23, 1999, a fire occurred in the crude unit at Tosco Corporation. Avon oil refinery in Martinez, California. Workers were attempting to replace piping attached to a 150-foot-tall fractionator tower while the process unit was in operation. During removal of the piping, naphtha was released onto the hot fractionator and ignited. The flames engulfed five workers located at different heights on the tower. Four men were killed, and one sustained serious injuries.

KEY ISSUES:
• CONTROL OF HAZARDOUS NONROUTINE MAINTENANCE
• MANAGEMENT OVERSIGHT & ACCOUNTABILITY
• MANAGEMENT OF CHANGE
• CORROSION CONTROL

ROOT CAUSES:
1. Tosco Avon refinery’s maintenance management system did not recognize or control serious hazards posed by performing nonroutine repair work while the crude processing unit remained in operation.
2. Tosco’s safety management oversight system did not detect or correct serious deficiencies in the execution of maintenance and review of process changes at its Avon refinery.

Image Credit: CSB

On March 13, 2001, three people were killed as they opened a process vessel containing hot plastic at the BP Amoco Polymers plant in Augusta, Georgia. They were unaware that the vessel was pressurized. The workers were killed when the partially unbolted cover blew off the vessel, expelling hot plastic. The force of the release caused some nearby tubing to break. Hot fluid from the tubing ignited, resulting in a fire.

KEY ISSUES:
• RECOGNITION OF REACTIVE HAZARDS
• LEARNING FROM NEAR-MISS INCIDENTS
• OPENING OF PROCESS EQUIPMENT

ROOT CAUSES:
1. Amoco, the developer of the Amodel process, did not adequately review the conceptual process design to identify chemical reaction hazards.
2. The Augusta facility did not have an adequate review process for correcting design deficiencies.
3. The Augusta site system for investigating incidents and nearmiss incidents did not adequately identify causes or related hazards. This information was needed to correct the design and operating deficiencies that led to the recurrence of incidents.

Image Credit: CSB

A fire started inside a depot with 3 million liters of diesel and the flames spread to four neighboring storage tanks. The fire lasted for 9 days.

Fine of around USD $6.4 million (R$ 22.5 million). Environmental impact causing death of thousands of fish

Proximate causes:
• Inadequate management/ supervision
• Inadequate work planning

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Paulo Whitaker / Reuters

On April 8, 2004, four workers were seriously injured when highly flammable gasoline components were released and ignited at the Giant Industries Ciniza refinery, east of Gallup, New Mexico. The release occurred as maintenance workers were removing a malfunctioning pump from the refinery’s hydrofluoric acid (HF) alkylation unit. Unknown to personnel, a shut-off valve connecting the pump to a distillation column was apparently in the open position, leading to the release and subsequent explosions.

KEY ISSUES:
• MECHANICAL INTEGRITY
• CORROSION & SCALE FORMATION
• VALVE DESIGN
• HUMAN FACTORS CONSIDERATION
• MANAGEMENT OF CHANGE
• LOCKOUT/TAGOUT & ISOLATION

ROOT CAUSES:
1. An MOC hazard analysis was not conducted.
2. the facility lacked procedures to verify that the pump had been isolated, depressurized and drained.
3. Instead of determining the cause of frequent pump malfunctions and then implementing a program that would prevent problems before they occurred, Giant used breakdown maintenance by making repeated repairs to the pump seals after failure.

Image Credit: CSB

On April 26, 2018, an explosion and subsequent fire occurred at the Superior Refinery Company LLC refinery in Superior, Wisconsin (‘Husky Superior Refinery’). The incident occurred in the refinery’s Fluid Catalytic Cracking Unit (FCCU). In preparation for the shutdown, the refinery brought in hundreds of contractors and increased operations staffing. The contractors were performing many tasks such as electrical work, preparing for chemical cleaning, building scaffolding, and welding. As a result of the explosion, thirty-six people sought medical attention, including eleven refinery and contract workers who suffered OSHA recordable injuries. In addition, a large portion of Superior, Wisconsin was evacuated. The refinery was shutting down in preparation for a five-week turnaround when an explosion occurred, sending several people to area hospitals with injuries.

KEY ISSUES:
• PYROPHORIC IRON SULFIDE

Image credit: CSB

An explosion at the Partridge-Raleigh oilfield in Raleigh, Mississippi. The incident occurred at about 8:30 a.m. on June 5, 2006, when Stringer’s Oilfield Services contract workers were installing pipe from two production tanks to a third. Welding sparks ignited flammable vapor escaping from an open-ended pipe about four feet from the contractors’ welding activity on tank 4. The explosion killed three workers who were standing on top of tanks 3 and 4. A fourth worker was seriously injured.

KEY ISSUES:
• HOT WORK CONTROL
• SAFE WORK PRACTICES AT OIL & GAS PRODUCTION WELLS

ROOT CAUSES:
1. A gas detector was not used to test for flammable vapor.
2. ‘Flashing’ tanks containing hydrocarbons with a lit oxy-acetylene torch to determine the presence of flammable vapor is unsafe and extremely dangerous.
3. The open pipe on the adjacent tank was not capped or otherwise isolated.
4. A makeshift work platform – a ladder placed between the tanks – was used.
5. All tanks were interconnected and some of the tanks contained flammable residue and crude oil.

Image credit: CSB

On June 9, 2009, a major natural gas explosion heavily damaged the ConAgra Slim Jim meat processing factory in Garner, North Carolina, just south of Raleigh. Three workers were crushed to death when a large section of the building collapsed. The explosion critically burned four others and sent a total of 71 people to the hospital including three firefighters who were exposed to toxic anhydrous ammonia from the plant’s refrigeration system. Approximately 18,000 pounds of ammonia were released to the environment and 100,000 square feet of the plant were damaged. Due to the severity of the structural collapse, there was the potential for numerous additional deaths or serious injuries.

KEY ISSUES:
• DIRECTLY VENT PURGED GASES TO A SAFE LOCATION OUTDOORS, AWAY FROM PEOPLE AND IGNITION SOURCES.
• USE COMBUSTIBLE GAS DETECTORS TO MONITOR THE GAS CONCENTRATION DURING PURGING OPERATIONS.
• ENSURE PERSONNEL INVOLVED IN GAS PURGING OPERATIONS ARE FULLY TRAINED.

ROOT CAUSES:
1. Purging into equipment vicinity is common practice

Image credit: CSB

On June 10, 2008, Goodyear operators closed an isolation valve between the heat exchanger shell (ammonia cooling side) and a relief valve to replace a burst rupture disk under the relief valve that provided over-pressure protection. Maintenance workers replaced the rupture disk on that day; however, the closed isolation valve was not reopened.

On the morning of June 11, an operator closed a block valve isolating the ammonia pressure control valve from the heat exchanger. The operator then connected a steam line to the process line to clean the piping. The steam flowed through the heat exchanger tubes, heated the liquid ammonia in the exchanger shell, and increased the pressure in the shell. The closed isolation and block valves prevented the increasing ammonia pressure from safely venting through either the ammonia pressure control valve or the rupture disk and relief valve. The pressure in the heat exchanger shell continued climbing until it violently ruptured at about 7:30 a.m.

The catastrophic rupture threw debris that struck and killed a Goodyear employee walking through the area. The rupture also released ammonia, exposing five nearby workers to the chemical. One additional worker was injured while exiting the area.

KEY ISSUES:
• EMERGENCY RESPONSE & ACCOUNTABILITY
• MAINTENANCE COMPLETION
• PRESSURE VESSEL OVER-PRESSURE PROTECTION

ROOT CAUSES:
1. Although maintenance workers had replaced the rupture disk by about 4:30 p.m. on June 10, the primary over-pressure protection for the heat exchanger remained isolated until the heat exchanger ruptured at about 7:30 a.m. on June 11.

Image credit: CSB

The June 13, 2013 catastrophic equipment rupture, explosion, and fire at the Williams Olefins Plant in Geismar, Louisiana, which killed two Williams employees. The incident occurred during nonroutine operational activities that introduced heat to a type of heat exchanger called a ‘reboiler’ which was offline, creating an overpressure event while the vessel was isolated from its pressure relief device. The introduced heat increased the temperature of the liquid propane mixture confined within the reboiler shell, resulting in a dramatic pressure rise within the vessel due to liquid thermal expansion. The reboiler shell catastrophically ruptured, causing a boiling liquid expanding vapor explosion (BLEVE) and fire.

Process safety management program weaknesses at the Williams Geismar facility during the 12 years leading to the incident caused the reboiler to be unprotected from overpressure.

KEY ISSUES:
• OVERPRESSURE PROTECTION
• PROCESS HAZARD ANALYSIS
• MANAGEMENT OF CHANGE
• PRE-STARTUP SAFETY REVIEW
• OPERATING PROCEDURES
• HIERARCHY OF CONTROLS
• PROCESS SAFETY CULTURE

ROOT CAUSES:
1. Williams did not perform the 2001 MOC until after the plant was operating with the valves installed, and the associated PSSR was incomplete. These actions did not comply with facility (and regulatory) safety management system requirements; however, Williams management accepted both of these practices;
2. Car seals are low-level, administrative controls, but they were the favored safeguard in the 2006 PHA recommendation to prevent overpressure events. Williams Geismar did not have a policy requiring the effectiveness of safeguards to be analyzed;
3. Williams Geismar did not follow OSHA PSM regulatory requirements that operations activities have an associated procedure to safely conduct the work. For example, Williams did not create a procedure specifically for switching the propylene fractionator reboilers Such a procedure should have alerted the operations personnel of the overpressure hazard;
4. The Williams PHA policy did not require effective action item resolution and verification, resulting in incorrect action item implementation in the field;
5. The Williams PHA policy did not require PHA teams to effectively evaluate and control risk; and
6. Operations personnel had informal authorization to manipulate field equipment as part of assessing process deviations without first conducting a hazard evaluation and developing a procedure.

Image & AcciMap Credit: CSB