ARE YOU MEASURING FURNACE TUBES SKIN TEMPERATURE RIGHT?

 On January 21, 2023, at 1:58 p.m., a mixture of hydrogen and hydrocarbons was accidentally released into the firebox of a fired heater, where it ignited, resulting in a large fire at a refinery in Louisiana. The  property damage from the incident to be approximately $34.1 million.

According to the company's investigation, four months before the incident, a contractor performed an infrared (“IR”) scan of the fired heater and found elevated temperatures in the heater, with one tube section operating above 1,300 degrees Fahrenheit (℉). At the time, the contractor concluded that the high temperatures were measurements of the scale and oxidation on the outside surface of the tubes, not the tube’s metal wall temperature. After the incident, the company determined that the IR temperature measurements taken before the incident were likely accurate, but they had been misinterpreted. As a result, the infrared temperature data was not used to adjust the operating conditions of the fired heater, which could have lowered the tube temperature within the design limit.

The company's  investigation determined that on the day of the incident, the fired heater’s tubes experienced another high-temperature event, leading to a tube rupture. The unit had automatically shut down due to a problem in another part of the process. During this shutdown, the hydrogen and hydrocarbons flowing through the fired heater’s tubes stopped, but the burners continued operating because the fuel gas control valve did not fully close. Without fluid flow through the tubes to remove heat, the tube’s temperature exceeded 1,400℉. Operating at this temperature caused short-term overheating, further degrading the tubes’ integrity. As the fired heater was restarted, a tube ruptured (Figure 2), releasing a flammable mixture of hydrogen and hydrocarbons into the firebox, where flames from the gas-fired burners ignited it and resulted in a fire at the facility. The investigation concluded that the tube failure was likely the result of a combination of localized creep damage (which results from prolonged exposure to stress at elevated temperatures) and short-term overheating.

The company estimated that about 51,000 pounds of diesel, 160 pounds of hydrogen, and 560 pounds of methane were released. After the incident, the company installed larger fired heater viewports to allow for improved infrared scans of the tubes and installed instrumentation to monitor temperature.

Probable Cause
Based on the company investigation, the CSB determined that the probable cause of the incident was a fired heater tube rupture from a combination of creep damage and short-term overheating. Flames from the fired heater’s burners ignited the released flammable mixture of hydrogen and hydrocarbons, resulting in the fire. Insufficient temperature instrumentation and an inadequate infrared scanning program contributed to the incident.

Source:CSB.gov

ARE YOUR FIRED HEATERS SAFEGUARDS RELIABLE?

 On December 23, 2022, at about 4:08 a.m., approximately 1,800 gallons of naphtha were accidentally released into the firebox of a fired heater, where it ignited, resulting in a serious fire at a Refinery in  Arkansas. The company estimated that the property damage from the incident was $36 million.

The company's investigation identified that ambient temperatures at the facility dropped to 12 degrees Fahrenheit by 11:00 p.m. on the night of the incident. This cold weather caused operational issues with some instruments and controls, leading to low hydrocarbon flow through the tubes of a fired heater. The decreased flow resulted in reduced heat transfer, which likely caused the metal temperatures in the tubes to rise significantly. This high-temperature condition ultimately caused a tube to rupture, releasing flammable hydrocarbons into the firebox, where the existing burner flame ignited them. The company commissioned a metallurgical examination and found that the tube ruptured due to creep damage (which results from prolonged exposure to stress at elevated temperatures) and short-term overheating.

The company's investigation found that some instruments and controls were not effectively winterized for cold weather conditions, which impacted their performance. As a result, some controls were put in manual mode, and some alarms were interpreted by employees as unreliable, leading to reduced hydrocarbon flow through the tubes and elevated tube wall temperatures. Additionally, the fired heater was not equipped with instrumentation to measure the tube’s metal wall temperatures. The company's investigation further revealed that the process hazard analysis for this fired heater relied on safeguards that were insufficient or not in place to prevent low tube pass flow conditions. In addition, a low-flow safety interlock did not work because it was improperly set.

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the naphtha release was a tube rupture, which resulted from creep damage and short-term overheating. Flames from the fired heater’s burners ignited the flammable hydrocarbons, resulting in the fire. Fired heater safeguards that were not in place or improperly set, in addition to inadequate winterization of flow control equipment, contributed to the incident. Had the fired heater been equipped with instrumentation to measure the tube’s metal wall temperatures and other safeguards been in place, this incident likely could have been prevented.

Source: CSB.gov

ACCIDENT DURING PIGGING

 On October 11, 2022, at approximately 2:00 p.m., 2,200 cubic feet of natural gas under high pressure were released from a 20-inch gas pipeline at an Energy in New Mexico. The high-pressure natural gas forcefully impacted a contractor, resulting in one serious injury.
On the day of the incident, an employee and a contractor were tasked with passing a large-diameter cleaning tool (called a “pig”) through the 20-inch pipeline. This “pigging” procedure involved sending a pig with a diameter slightly larger than the pipe to clean and displace fluids within the pipeline. High pressure pushes the pig through the piping, ending in a section (called a “receiver”) designed to capture and hold the pig until removal. The receiver was newly installed and being used for the first time at the time of the incident.
When the two workers went to remove the pig from the receiver, the pressure in the receiver was above 1,150 pounds per square inch (“psi”). To safely remove the pig, the pressure needed to be reduced by relieving it through a vent valve located at the top of the receiver. The contractor initially tried to remove the plug from the vent valve to relieve the pressure but found that the plug could not be removed with hand tools. This indicated that there could be pressure between the valve and the plug, forcing the threads tightly against each other. The contractor concluded that the vent valve might be leaking and decided to relieve the pressure inside the receiver using the drain valve instead, which was located at the bottom of the receiver 

The company's investigation of the incident found that the 90-degree fitting (elbow) was not properly tightened, allowing it to turn freely. Because the elbow was not properly tightened, when the contractor applied a wrench to the valve stem and began opening the 2-inch ball valve on the drain piping, the valve rotated to the left and fully opened. The 1,150-psi natural gas forcibly discharged toward the contractor’s left leg, launching the contractor approximately 50 feet away from the source of the release, resulting in a serious injury. The contractor was transported by helicopter and admitted to a hospital for medical treatment.
Probable Cause
Based on company's investigation, the CSB determined that the probable cause of the incident was the insufficient tightening of the 90-degree fitting, which resulted in the full opening of the drain valve and the rapid and forcible release of natural gas from the receiver. The leaking vent valve at the top of the receiver also contributed to the incident. The non-welded drain piping, which was able to turn freely when the valve was opened, contributed to the severity of the incident.

Source: CSB.gov

THE LAST "TO" IN "LOTOTO" IS VERY IMPORTANT!

 On September 22, 2022, at approximately 9:00 a.m., a liquid mixture comprised of aniline, formalin, and hydrochloric acid was accidentally released, seriously injuring one contractor at a chemical manufacturing facility in Louisiana 

On September 20, 2022, two days before the incident, an off-site power outage caused an immediate loss of process flow in the methyl diamine unit. The lack of flow allowed solids to form throughout a piping system. Company personnel were clearing the solids from this piping on September 22 when the incident occurred.
At approximately 9:00 a.m. on September 22, two contract workers began opening a flange connection in the piping system. After the flanged connection was fully opened, an amount (approximately 28 ounces) of toxic and corrosive liquid containing aniline, formalin, and hydrochloric acid sprayed from the open-ended piping. Some of the released liquid contacted the face and neck of a third contract worker (“hot zone attendant”). The hot zone attendant was present to monitor the safety of workers inside the “hot zone”—a 30-foot diameter area marked by red barricade tape—and to help decontaminate any workers leaving the hot zone. While the workers inside the barricade were wearing personal protective equipment (“PPE”) that included chemical suits with hoods and full-face supplied air respirator masks, the hot zone attendant wore a chemical suit and hood but was not wearing face protection.

After being sprayed with the toxic and corrosive liquid, the hot zone attendant first showered in the unit and then again at the site’s medical facility. The hot zone attendant was then transported to a hospital, admitted for inpatient care, and successfully treated for exposure to aniline.
The company's investigation found that the hot zone attendant did not wear face protection because the operations team did not recognize the potential for pressurized liquid aniline to remain in the piping system. Energy isolation work (often referred to as line breaks) performed after the power outage involved opening multiple other piping connections, including a valve at the high point in the piping system. The operations team believed that this work had removed pressure from the system. A post-incident review of the process data, however, showed that pressure remained in some areas of the piping system. The company’s energy isolation plan did not include a review of the available local or computer control system data to ensure that the piping was not under pressure.

Probable Cause
Based on company's investigation, the CSB determined that the probable cause of the accidental release was the opening of the flange connection while portions of the piping contained pressurized liquid. The company's energy isolation plan contributed to the incident by not ensuring the piping was depressured before workers began disassembling the flange connection. Allowing a worker near this equipment opening activity who was not wearing protective equipment that could shield the worker’s face from being sprayed with the toxic and corrosive process liquid contributed to the severity of the incident. Had the worker been wearing protective equipment with a face shield, this incident likely could have been prevented. Additionally, reviewing available local or computer control system data prior to the work to ensure that the piping was not under pressure could have helped prevent this incident.

Source:CSB.gov

DOES YOUR LOW FLOW TRIP OF FIRED HEATERS TAKE CARE OF ALL PASSES?

 On August 19, 2022, at approximately 3:45 a.m., about 4,000 pounds of a hydrogen and hydrocarbon mixture was accidentally released into the firebox of a fired heater, where it ignited, creating a large fire at a refinery in Texas City, Texas. Estimated that the property damage from the incident was $10 million.

On the morning of the incident, the company restarted a fired heater that had been offline for approximately 12 hours due to a compressor shutdown caused by a malfunction of a pressure transmitter in the lube oil system. During the startup, it was essential to flow process feed through all four passes of the fired heater’s tube system. However, only two of the four passes in the tube system had sufficient flow through them when the burners were ignited. Although the minimum flow was eventually established in another tube pass, there was no flow through the fourth pass.
Company investigation of the incident found that without the fluid flowing through the fourth pass to remove heat, the tube’s metal wall temperature reached 1,500 degrees Fahrenheit (℉), which exceeded the design temperature limit. After the operations supervisor noticed the high temperature, field operators were sent to inspect the heater tubes. The field operators reported that some tubes were “glowing red hot,” and consequently they manually turned off two of the fired heater’s eight burners. The field operators then reduced the flow through the first three passes to help drive feed material into the fourth pass. Although operators reported hearing material flowing in the fourth pass, the meter indicated no flow. The operations team concluded that the flow meter was malfunctioning.
Less than an hour later, a convection section tube in the fourth pass ruptured due to short-term, overheating  releasing a flammable mixture of hydrogen and hydrocarbons into the firebox. Flames from the gas-fired burners ignited the mixture, resulting in a large fire.

During its investigation, the company discovered that the startup procedure for the fired heater, which required maintaining a steady flow through all four tube passes before lighting the burners, was not used. This procedure was “conditional,” however, and was only necessary if the firebox temperature had cooled below 400℉. At the time when the burners were lit, this temperature was slightly below 400℉.
Additionally, the company found that the fired heater lacked engineered safeguards to prevent the burners from being lit before establishing flow in each of the four passes. In response to the incident, the company modified its automated burner controls to help ensure that the flow rate through every pass exceeds a predetermined minimum flow rate before operators can ignite a burner.

Probable Cause
Based on the company investigation, the CSB determined that the probable cause of the incident was a ruptured fired heater tube from short-term overheating. Flames from the fired heater’s gas-fired burners ignited these flammable chemicals, resulting in the fire. The lack of automated safeguards that did not prevent the burners from being ignited before the minimum flow was established through each of the four tube passes contributed to the incident. Had the company had such automated safeguards in place, this incident likely could have been prevented.

Source:CSB.gov

ARE YOU CLEARING YOUR TANKS COMPLETELY AND ENSURING NO FLAMMABLE / TOXIC VAPOURS ARE PRESENT BEFORE HANDING OVER TO MAINTENANCE?

On July 29, 2022, at 7:45 a.m., an explosion and fire occurred at a facility in Mississippi. The explosion and subsequent fire fatally injured one employee and seriously injured five other employees 

The facility separates crude oil condensate (flammable liquid hydrocarbon) from salt water through a series of four tanks. After the crude oil condensate is recovered, the saltwater waste is pumped into a saltwater disposal well. Two of the tanks used in the disposal process were replaced with new tanks shortly before the incident occurred, but two tanks were not replaced.
The company's investigation found that although most of the liquid was removed from the two tanks that were not replaced, some salt water, residual hydrocarbon material, and air remained inside these tanks. At the time of the incident, seven employees were completing the tank replacement work, which included installing an elevated walkway between the tanks and finishing piping and structural connections. While welding piping between the two middle tanks, one of the employees opened a valve to the older tank that contained residual crude condensate material, likely releasing some hydrocarbon vapors into the new piping being welded. The flammable vapor ignited, and flames traveled back into the tank, resulting in an explosion and fire that ejected the top of the tank. In addition, the blast launched and forcefully propelled an adjacent tank approximately 80 feet into the woods 

As a result of the explosion and fire, six of the employees were transported and admitted to the hospital, where they received treatment for their burn injuries. One of these employees died at the hospital six days later.
The company's investigation found that no work permits were written for the welding work associated with the tank replacement task. An investigation by the federal Occupational Safety and Health Administration (OSHA) found that the tanks involved in the explosion had not been thoroughly cleaned, which allowed flammable material to remain near the welding activity at the time of the incident.

Probable Cause
Based on the company's and OSHA’s investigations, the CSB determined that the probable cause of the incident was the presence of flammable vapors near a welding activity being performed. Not thoroughly draining, cleaning, and purging the tanks to remove the flammable material before starting construction contributed to the incident. Had the tanks been thoroughly drained, cleaned, and purged prior to the commencement of construction, this incident likely could have been prevented.

Source:csb.gov

ARE YOUR PROCEDURES CLEAR AND WARN OF DANGERS?

On July 2, 2021, at approximately 9:15 p.m., approximately 700 pounds of a mixture of vapors, including chlorodifluoromethane (“R22”) and perfluoroisobutene (“PFIB”), were released a facility in Alabama . Exposure to the toxic mixture of vapors fatally injured two operators and seriously injured another Daikin operator.

A drying tower was being returned to service after it had been offline for maintenance. After the maintenance activity, this equipment contained air, and the procedure included steps to remove this air and replace it with R22. To accomplish this, the company used a two-step purge process. First, nitrogen was added to sweep out the air, and second, R22 was added to sweep out the nitrogen. The displaced vapors were released into the ambient air from an open valve about six feet above the ground for each step. The valve was aimed vertically downward, resulting in the vapors being released in a downward direction toward the area where the operators were working.
The procedure did not specify the source of the R22 material used in this purging operation. The R22 was taken from another process vessel that contained other chemicals, including PFIB. As operators performed this purging, PFIB was released into the ambient air from the open valve, exposing three operators to this toxic vapor. The operators did not immediately report any adverse effects from the exposure and went home at the end of their shift. Approximately two days later, two of the operators became ill and were admitted to the hospital. The next day, the third operator was hospitalized. Two of the operators later succumbed to their respiratory injuries. One operator died on August 10, 2021, and the second operator passed away on September 28, 2021.

After the incident, the comapny updated its procedure to warn that toxic vapors may be present and to require that its operators use supplied air respirators. In addition, the company now directs the purge vapors to an incinerator. The procedures were also updated to specify that only high-purity (non-toxic) R22 can be used in the purging procedure.

Probable Cause
Based on the company's investigation and an investigation by the federal Occupational Safety and Health Administration (OSHA), the CSB determined that the toxic PFIB vapors were likely released with R22, which was purged from equipment into the ambient air to remove nitrogen. The safety management systems, which allowed the discharging of R22, PFIB, and other byproducts into a work area, contributed to the severity of the incident. Had the company ensured that the release of these hazardous vapors was avoided or discharged to a safe location, the incident could have been prevented. 

Source:CSB.gov

ARE YOUR EMERGENCY SHUTDOWN PROCEDURES ADEQUATE TO PREVENT DAMAGE?

 On February 15, 2021, at 3:05 p.m., a hydrogen and hydrocarbon gas mixture was accidentally released into the firebox of a fired heater, where it ignited and exploded. It was estimated the incident resulted in $2.5 million in property damage.

The company's investigation found that the facility shut down multiple fired heaters when extreme cold weather from Winter Storm Uri caused several freeze-related operational issues. Due to emergency conditions that included utility losses and supplier-driven gas shortages, the company shut down its fired heaters without removing the solidified carbon deposits on the interior walls of the heater tubes (decoking).

The company's investigation revealed that further utility upsets caused the facility to stop all fuel gas supply and fully shut down the remaining fired heaters. During the shutdown, a valve between one of the ethylene unit’s fired heaters and downstream equipment remained open. The open valve allowed downstream flammable hydrogen and hydrocarbon gas to flow backward into the fired heater tubes. Approximately 30 minutes after this happened, a tube within the fired heater ruptured, allowing the flammable gas to enter the firebox. The gas accumulated, ignited, and exploded, causing extensive damage to the fired heater (Figure 2).

The company's investigation determined that the tube failure likely occurred because the fired heater tubes were shut down without decoking. Coke fouling can insulate the tube surface, resulting in local hotspots and increasing the risk of thermal shock and tube failure in fired heaters. These conditions stressed the tube’s walls when the metal cooled faster than the internal coke, breaking the tube. The company's investigation concluded that hot insulation inside the firebox likely ignited the gas (autoignition).

Probable Cause
Based on the company investigation, the CSB determined that the probable cause of the incident was a fired heater tube failure from thermal stress due to the rapid shutdown. When the tube broke, a hydrogen and hydrocarbon gas mixture from downstream equipment flowed into the firebox. Hot insulation within the firebox likely ignited the flammable gas, resulting in an explosion. Inadequate winterization of multiple valves, instruments, and control systems contributed to the incident.

Source: CSB.gov

HAVE YOU CONSIDERED FREEZING OF WATER IN INSTRUMENT AIR HEADERS DURING LOW AMBIENT WEATHER CONDITIONS?

 On February 15, 2021, at 9:53 p.m., a hydrogen and hydrocarbon gas mixture was accidentally released into the firebox of a fired heater, where it ignited, creating a fire at a facility in Texas. The estimated property damage from the incident was $5.8 million.

The company investigation determined that freeze-related operational issues due to extreme cold weather from Winter Storm Uri caused the facility’s boiler units to shut down. This shutdown decreased the supply of steam and water to an ethylene unit at the facility. A safety system automatically shut the fired heater down due to insufficient steam and water flow. Although the automatic valves closed to prevent feed from entering the tubes, the fired heater’s fuel gas isolation valve failed to close as intended. This failure allowed the burners to continue operating. Without any flow through the tubes to remove heat from their walls, the tubes in the fired heater reached excessively high temperatures. Some tubes ruptured, likely due to short-term overheating, but a metallurgical analysis was not performed to confirm the cause of the tube failures. When the tubes ruptured, hydrocarbons downstream from the fired heater were released through the broken tubes and ignited by the burner flames inside the firebox, causing a fire.

During post-incident testing by the company in temperatures above freezing, the fuel gas isolation valve successfully closed as designed. The company's investigation concluded that the fuel gas isolation valve did not close because water in the instrument air supply had frozen or ice formed on the external actuator components (related to inadequate winterization), preventing the isolation valve from closing.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the rupture of fired heater tubes from short-term overheating. When the tubes were broken, a hydrogen and hydrocarbon gas mixture flowed from downstream equipment into the firebox. Flames from the burners ignited the flammable materials, resulting in the fire. Inadequate winterization of flow control equipment contributed to the incident.

HAVE YOU IDENTIFIED ALL POSSIBLE SOURCES OF CORROSION?

On October 1, 2020, at approximately 9:00 a.m., approximately 554 pounds of chlorine gas were accidentally released at a facility in Louisiana. Exposure to the toxic chlorine vapors seriously injured one employee.

At the time of the incident, four workers (two employees and two contractors) were trying to stop a chlorine leak (described by as a fugitive emission) from a drain valve in the company’s methyl diisocyanate production plant. Because a chlorine leak was detected, the company assumed that at least one of the drain valve’s connections in its flanges or bonnet was loose.
The four workers had a safe work permit to retighten the bolts using hand tools. However, the leak persisted after the bolts were retightened by hand. One of the contractors then tried to retighten the bolts using an impact wrench, a power tool designed to tighten and loosen bolts with short bursts of high torque. The vibrations from the impact wrench caused the connections on the drain valve’s bonnet to fail catastrophically, forcefully disconnecting the top half of the drain valve (closing element, stem, and handle) from the bottom half (body and seat) and releasing the toxic chlorine vapors.
The workers were wearing supplied air respirators to perform the job. After the chlorine release, they evacuated the area. However, one employee did not switch to the “escape bottle” for their respirator before detaching the respirator from the stationary air supply source during the evacuation. The subsequent lack of supplied airflow in the respirator caused the employee to remove their respirator mask during the evacuation, resulting in the employee being exposed to the toxic chlorine vapors. The employee was transported and admitted to a hospital for medical treatment.
The company's investigation found that the drain valve was severely corroded. Over time, chlorine being released from the drain valve had reacted with condensed water that had accumulated in the piping system’s insulation blanket, creating hydrochloric acid that had corroded the valve and deteriorated the bolts in the valve’s bonnet. After the incident, the company discovered that three other valves were similarly corroded.

The investigation also revealed that one of the contractors tried to use their stop work authority after seeing the dilapidated valve. The contractor brought concerns to one of the employees. While the  employee went to get a supervisor’s opinion, there was a miscommunication between the two parties about whether or not to continue working on the corroded valve. As a result, the work continued, ultimately leading to the chlorine gas release.

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the catastrophic failure of corroded bolts in the drain valve’s bonnet. The corrosion was caused by prolonged exposure to hydrochloric acid, created by the reaction between chlorine and condensed water.
Contributing to the incident was the company's mechanical integrity program. Had the company  inspected the valve before authorizing this job, the extent of the corrosion could have been identified, and a shutdown could have been initiated to replace the drain valve instead of attempts to repair it. Contributing to the severity of the incident was the company's respiratory protection program, which did not ensure its workers could effectively transition to the escape bottle during an emergency. Had the company effectively trained its workers to switch to their escape bottles during an emergency, the employee should have not been exposed to the chlorine.

Source: CSB.gov

DISTILLATION TOWER COLLAPSE DUE TO INTERNAL FIRE

On September 5, 2023, at 11:50 a.m., a distillation tower (“Tower”) collapsed (Figure 1) at a Petrochemical in Texas. The collapse was the result of a fire inside the distillation tower. The incident resulted in approximately $194 million in property damage.

A few weeks before the incident, the company shut down its Pyrolysis Gasoline unit, including its extractive Tower. The company followed its procedure to remove solvent and hydrocarbons from within the Tower to prepare for maintenance work. On the day of the incident, a maintenance crew began opening manways to prepare the Tower for entry. At 9:30 a.m., temperatures with the Tower’s stainless steel structured packing beds began to rise. The company sounded an emergency alarm at 10:44 a.m. after smoke and flames showed a fire within the Tower. Personnel were evacuated after adding nitrogen and trying to stop air from entering the Tower. At 11:53 a.m., the Tower folded over (collapsed).
The company investigation found that the Tower fire resulted from a chain of undesired reactions. About a month before the unit shut down, equipment leaks in another area of the process allowed water to enter the extractive distillation unit, leading to internal corrosion that removed iron from the metal walls. This iron formed iron sulfide (a pyrophoric material) from hydrogen sulfide that is usually present in the process equipment. When the Tower’s manways were opened, oxygen (air) entered the Tower, starting an exothermic iron sulfide oxidation reaction. The company concluded that the heat from this iron sulfide oxidation reaction resulted in localized heating (1,300 to 1,800 degrees Fahrenheit) within the structured packing that weakened the Tower’s walls and ultimately caused the Tower to collapse.
In addition, The company’s investigation found that a 2016 incident had revealed the potential for iron sulfide to accumulate within the Tower. The investigation team determined that this knowledge had not been effectively transferred to the existing site personnel. Had the site’s operations team known about the potential for iron sulfide within the Tower, changes to the procedure to remove solvent and hydrocarbon could have been made to mitigate the heating from the iron sulfide oxidation.
During the incident, approximately 160 pounds of sulfur dioxide and an unknown amount of other reaction and combustion products were accidentally released.
Probable Cause
Based on The company’s investigation, the CSB determined that the probable cause of the fire was smoldering iron sulfide oxidation within the structured packing of the Tower. Contributing to the incident was that the company did not effectively maintain its knowledge from its 2016 incident finding that iron sulfide could accumulate within the Tower.

Source: CSB.gov

TANK OVERPRESSURE INCIDENT

On June 22, 2023, at about 9:10 p.m., a 5,200-gallon polyethylene storage tank (“tank”) ruptured at a facility in North Carolina. The rupture fatally injured one employee.
At the time of the incident, the tank needed to be refilled with aluminum chloride; however, sulfuric acid was added instead. Approximately 80 gallons of 93 percent sulfuric acid were added to the 60 gallons of aluminum chloride remaining in the tank, resulting in a reaction that caused the tank to rupture. The tank rupture fatally injured the employee who was refilling the aluminum chloride tank.
The company's investigation appeared to focus on the incorrect reaction rather than a reaction scenario consistent with the available evidence. Its research materials pointed to the reaction between sulfuric acid and aluminum metal that generated hydrogen gas. The company concluded that the hydrogen gas was released at its autoignition temperature (over 1,000 degrees Fahrenheit (°F)) and ignited, triggering an explosion. Post-incident photographs of the damaged tank do not appear to support a scenario where the internal tank temperature reached 1,000 °F, however. The melting temperature of the polyethylene is approximately 260 °F. Therefore, the company’s reaction scenario appears inconsistent with the available evidence.
The CSB concluded that the reaction most likely generated hydrogen chloride vapors. The more likely scenario was that the reaction between aluminum chloride and sulfuric acid produced enough hydrogen
chloride vapor to increase the pressure within the polyethylene tank, likely resulting in an overpressure that separated the tank’s body from its base.
The CSB estimated that approximately 130 pounds of hydrogen chloride vapors were accidentally released.
Probable Cause
Based on the factual information from the company's investigation, the CSB determined that the probable cause of the overpressure was the increase in the tank’s internal pressure resulting from the hydrogen chloride vapors created by the reaction between sulfuric acid and aluminum chloride.

Source:CSB.gov

A SELF ACCELERATING DECOMPOSITION REACTION KILLS AN OPERATOR

On May 4, 2023, at about 12:40 a.m., a pressure Nutsche filter vessel (“vessel”) exploded at a facility in  Massachusetts. The explosion and fire fatally injured one operator and caused approximately $48 million in loss from property damage, which led to the permanent closure of the facility.

At the time of the incident, the plant was producing a substance called Dekon 139 (“Dekon”). The Dekon had already been synthesized, and excess liquid from the production process had been removed from the solid product (“cake”) within the nitrogen-inerted vessel. The plant used an agitator to smooth the cake and remove lumps that formed during drying to remove the liquid from the cake.                                                                                                                                                                            In post-incident testing, the plant determined that Dekon could undergo exothermic, self-accelerating decomposition when heated to 280 degrees Fahrenheit. The plant learned that Dekon decomposition releases flammable gases, including hydrogen, methane, and carbon monoxide.
In its incident investigation, the plant determined that leading up to the incident, the agitator had loosened and was rubbing a plate at the bottom of the filter dryer vessel, generating heat from friction. The friction likely caused an area of high temperature (“hot spot”) in the Dekon, which likely reached the temperature
necessary for the Dekon to begin decomposition. The decomposition reaction released energy, which increased the temperature of the material in the vessel and caused more Dekon to decompose.                                                                                                                                
The gases produced by the reaction rapidly increased the pressure within the vessel, causing the vessel’s discharge door to open. The released flammable materials (gas and Dekon dust) mixed with atmospheric oxygen and ignited, causing an initial weak explosion. Shortly after that, the vessel’s rupture disc opened, and a second larger explosion occurred when the vessel failed.
One operator was unable to escape the area and was fatally injured.
The CSB estimated that approximately 600 pounds of Dekon decomposed into flammable gases that were consumed during the incident.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the explosion and fire was a self-accelerating decomposition reaction of Dekon, which produced flammable gases and released combustible Dekon dust that ignited upon release. Contributing to the incident was the company's incomplete knowledge of the hazards associated with Dekon, including its ability to undergo a self-accelerating decomposition reaction capable of rupturing the reaction vessel.

Source:CSB.gov

Watch "Process Alarm Systems Updates to EEMUA 191 by Andy Brazier" on YouTube

 Watch "Process Alarm Systems Updates to EEMUA 191 by Andy Brazier" on YouTube

 https://youtu.be/xh62GMQ53u0?feature=shared

INCOMPATIBLE CHEMICALS CAUSE H2S RELEASE

 On March 29, 2023, at approximately 5:05 p.m., toxic hydrogen sulfide gas was accidentally released at a paper mill in Kentucky. Exposure to the hydrogen sulfide gas seriously injured one operator and injured two other operators.
At the time of the incident, three operators were tasked with circulating an acid-cleaning solution through process equipment to remove the buildup of solids impairing its performance. This task required an operator to stand directly over a tank and pour solid sulfamic acid powder into its opening.
When these operators added the sulfamic acid powder, the tank should have contained water, but a valve had been left open. This allowed a “weak wash” process stream to enter the tank before the operators added the solid sulfamic acid. The weak wash contained sodium sulfide, which reacted with the sulfamic acid, generating the toxic hydrogen sulfide gas.
Operator 1, who was standing directly over the tank opening (Figure 1), lost consciousness from exposure to the hydrogen sulfide gas that evolved from the tank. Operator 3 was able to call for help over the plant radio system but lost consciousness soon after. Operator 2 was seriously injured after losing consciousness (while trying to help Operator 1), falling to the floor, rolling through a guardrail system, and falling about 11 feet to a lower area of the structure.
Two other Domtar employees heard the distress call and entered the room to help the operators. All three operators regained consciousness. Operator 1 and Operator 3 were able to walk outside without assistance. Emergency responders transported Operator 2 to a hospital for treatment.
The company reported that about 25 pounds of hydrogen sulfide were released.

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the hydrogen sulfide release was the reaction between the added sulfamic acid and the sodium sulfide in the tank. The company's procedure procedures did not indicate that the weak wash valve should be closed during normal operation, which contributed to the incident. Had the weak wash valve remained closed (or more robustly isolated), sodium sulfide could have been kept out of the tank, preventing the reaction that generated the toxic hydrogen sulfide.

Source:CSB.gov

"Travel Stops on Spring Supports: What Engineers Need to Know" by Piping Technology and Products

The June 2025 process safety beacon talks about an incident that I had experienced with a locked spring hanger. Read the beacon in this link https://ccps.aiche.org/resources/process-safety-beacon/archives/2025/june/english

Piping Technology and products have published a safety alert explaining  "

"Travel Stops on Spring Supports: What Engineers Need to Know"

Read it in this link

https://pipingtech.com/resources/technical-bulletins/safety-alert-installation-spring-supports/

 

 

A FIRE WATER HOSE CAUSES A PUMP TO CRACK AND INJURE A EMPLOYEE

On February 24, 2023, at 9:20 a.m., an accidental release of approximately two gallons of a sodium hydroxide and water solution (“caustic solution”) seriously injured an employee at a facility in South Carolina.
A new pump for unloading caustic solutions from tank trucks was installed at the facility the day before the incident. On the day of the incident, the company used the new pump for the first time. Employees turned on the pump to begin transferring the caustic solution from a tank truck, but the pump failed to move fluid and leaked. The employees planned to disassemble the pump to identify the operational problem.
Before disassembling the pump, it was decided to flush it out with water from a fire hose. This action was taken to prevent employees from getting the caustic solution on their hands when the pump was disassembled. An employee connected a fire hose to the pump and partially opened the valve. The pump could not handle the pressure supplied by the firewater, and the plastic pump casing cracked. Caustic solution and water sprayed out of the pump, seriously injuring one employee.

After the incident, the company modified its caustic unloading system, eliminating the need for an unloading pump.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the overpressure of a pump casing after pressurized firewater was introduced to the pump.

Source:CSB.gov

INCIDENT DUE TO LONE WORKING WITHOUT ENGINEERING SAFEGUARDS

During the morning of February 24, 2023, an unknown amount of hydrocarbons and hydrogen sulfide were accidentally released, fatally injuring an employee inside an enclosed building at an oil and gas facility in Dakota. The hydrocarbons and hydrogen sulfide displaced the oxygen in the building, and the employee asphyxiated in the oxygen-deficient atmosphere.

The employee was considered a “lone worker” who operated multiple oil and gas facilities in the local area. Some of the oil and gas equipment was housed inside enclosed, insulated buildings, allowing operators to work in a climate-controlled environment. At the time of the event, it was negative 26 °F outside, and the interior of the building where the incident occurred (approximately 8 feet tall and 90 square feet) was about 65 °F.
A pump inside the building was not operating as designed, causing an adjacent vessel to begin overfilling. To prevent the vessel overfill from causing the facility to shut down, the employee began manually draining the vessel and another nearby vessel, both of which were housed inside the building. To drain the vessel, the employee connected a temporary hose to it and drained its liquid, mostly water and hydrocarbons, into a bucket inside the building. The employee then left the building temporarily to conduct operations at other locations in the facility. During this time, the drained hydrocarbons vaporized inside the enclosed building and displaced oxygen. About twenty minutes later, the employee returned to the insulated building and may have accidentally knocked over the bucket of drained liquid. Additional hydrocarbons and hydrogen sulfide likely vaporized, further displacing the oxygen inside the building. The employee breathed in the oxygen-depleted atmosphere and asphyxiated.
The building where the draining occurred did not have detectors installed to monitor for hazardous gases, and it was not ventilated. The employee had a personal gas detection monitor, but it was turned off and in his truck. No company procedure was in place that provided instructions for safely draining liquids from vessels inside buildings.
After the incident, the company evaluated adding additional engineering controls (for example, hazardous gas detection and alarms, forced ventilation) to its enclosed buildings, developed a written procedure requiring that process fluids be drained outside of buildings, and enhanced training and supervisor verification requirements regarding the use of personal gas monitors.
Probable Cause
Based on the company's investigation, the OSHA inspection, and the local Sheriff’s Office investigation, the CSB determined that the probable cause of the incident was the displacement of oxygen inside an enclosed building after an operator drained process liquid into a bucket and the hydrocarbon and hydrogen sulfide components vaporized. Contributing to the incident was the absence of company procedures detailing instructions for safely draining liquids from vessels located inside buildings. Contributing to the severity of the incident was the lack of engineered safeguards (such as installed detectors, alarms, and ventilation) to control or alert of a hazardous atmosphere and an unsuccessful system for ensuring employees wear personal gas monitors.

Source:CSB.gov

H2S RELEASE DUE TO SULFIDATION CORROSION

On April 8, 2023, at about 7:45 a.m., hydrogen sulfide and sulfur dioxide were released from the sulfur recovery unit at the a Refinery in Minnesota . This event resulted in $2.235 million in property damage.

The accidental release resulted from a ruptured tube within the waste heat boiler of the sulfur recovery reaction furnace. The tube rupture was caused by a damage mechanism known as sulfidation corrosion (also known as high-temperature sulfidic corrosion). Under certain temperature conditions, sulfidation corrosion causes thinning in iron-containing materials over time due to a reaction between sulfur compounds and iron.

The company investigation also found fouling (hydrocarbon solids), which had formed on the outside of some tube wall surfaces, resulted in higher tube wall temperatures and areas of increased metal loss from sulfidation corrosion. The investigation also found that the hydrocarbons were in the boiler feed water. This indicates that the boiler feed water was not being effectively monitored, which allowed the hydrocarbon contamination to remain undetected.

The company reported that approximately 68 pounds of hydrogen sulfide and 999 pounds of sulfur dioxide were released.The company now monitors and controls boiler feedwater quality with in-line analyzers. The analyzers continuously sample boiler feedwater and strip any hydrocarbons from the sample. A carrier air then sweeps the hydrocarbons to a metal-oxide sensor for quantitative analysis. The in-line sample results provide the opportunity to evaluate hydrocarbon presence in near real-time. This allows for identification when boiler feedwater does not achieve American Society of Mechanical Engineers (“ASME”) recommendations based on hydrocarbon measurement and implementation of prompt corrective measures as necessary.
Probable Cause
Based on the company investigation, the CSB determined that the probable cause of the accidental hydrogen sulfide and sulfur dioxide release was a tube rupture in the waste heat boiler. The tube had thinned over time from sulfidation corrosion. Contributing to this event was hydrocarbon contamination in the boiler feed water that was not being effectively monitored and controlled, resulting in localized tube fouling that led to increased tube wall temperatures and thinning from the sulfidation corrosion damage mechanism.

Source:CSB.gov

POINTING AND CALLING - REDUCING HUMAN ERROR DUE TO AUTOMATION BIAS

Source: Google

The pointing and calling method, known as "Shisa Kanko" in Japanese (指差喚呼), is a safety procedure used extensively in Japan, particularly in the railway system, to minimize errors and enhance focus. It involves physically pointing at a relevant indicator or control while verbally announcing its status. This dual action engages both visual and auditory senses, reinforcing attention and reducing the likelihood of mistakes.

Core Concept: Operators point at specific indicators (like signals, gauges, or controls) and verbally announce what they are observing or doing. 

 Example:A train driver might point at a signal displaying a green light and say, "Signal is green, proceeding." 
This method has been shown to significantly reduce errors and accidents in various industries, especially in the Japanese railway system, where it's been a key factor in maintaining high safety standards.
Widespread Use: While originating in the railway sector, pointing and calling is now used in many Japanese industries, including manufacturing, construction, and even in some office settings. 
Cognitive Impact: Studies suggest that pointing and calling activates different parts of the brain compared to simply looking or thinking about a task, further enhancing its effectiveness in preventing errors. 
 

Watch "Pointing and Calling – A simple way to reduce automation bias" on YouTube
https://youtu.be/UusWoWPZLNQ?feature=shared 

Answer from Perpexity Pro for my question - Number of Chemical Plant Accidents in India (2015–2025)

 Answer from Perpexity Pro for my question - Number of Chemical Plant Accidents in India (2015–2025)

"Major Chemical Accidents: Over the last 10 years, India has reported approximately 130 major accidents in chemical plants and industries.

Deaths and Injuries: These incidents led to at least 259 deaths and 563 serious injuries according to the National Disaster Management Authority (NDMA).

Monthly Average: In the three years prior to 2020 alone, there were more than four major chemical accidents each month in chemical manufacturing facilities—indicating ongoing risk and persistent safety challenges.

Increasing Trend: The frequency of gas and chemical leakage incidents has notably increased, with the number of registered accidents rising from 13 in 2013 to 30 in 2023, showing that the rate of accidents is climbing.

States Most Affected: Gujarat has repeatedly been the state with the highest number of reported incidents, for example, accounting for 24 of the 30 chemical leakage accidents nationwide in 2023.

Key Facts
Most commonly reported accidents are major fires, explosions, and toxic releases.

Fatalities and injuries figures are likely underestimates, as some incidents are not registered or fully documented.

SMEs and densely industrialized states remain particularly vulnerable.

Summary Table
Period last 10 years
Major Accidents 130
Deaths 259
Serious Injuries 563

*Approximate values, as per NDMA and national reporting.

The continued recurrence of chemical plant accidents in India highlights the need for improved process safety management and regulatory enforcement, particularly in rapidly industrializing regions and among small and medium-sized enterprises."

YOU CANNOT IDENTIFY A PROCESS HAZARD IN HAZOP IF YOU ARE NOT AWARE ABOUT IT!

On January 31, 2023, at 6:40 a.m., an accidental release of high-pressure carbon dioxide (CO2) occurred when a vessel overpressured and catastrophically ruptured at a CO2 gas plant in Texas. Vessel fragments propelled up to 1,200 feet away and heavily damaged a control room (Figure 1). Kinder Morgan estimated the property damage to be over $14 million.

The incident occurred in the site’s CO2 compression system. Upstream of each compressor was a vessel called a scrubber that removed liquid from the CO2 feed stream. Removing liquid from compressor feed streams is critical to preventing compressor damage.
On one of the high-pressure compressor system scrubbers, a liquid level control valve (called a “dump valve”) became stuck in the open position, which was common at the site during cold weather. The outside temperature at the time was 22 degrees Fahrenheit (°F). The liquid drained out of the high-pressure scrubber through the stuck-open valve, and then high-pressure CO2 gas also started flowing out through the stuck-open valve. The high-pressure gas was released into the low-pressure drain system, and as it did, the CO2 became cold—as low as negative 30 °F (due to the Joule-Thompson effect).

The cold CO2 caused ice or hydrate to form in a drain system vessel’s outlet piping, including the piping to its emergency pressure relief valve. When this happened, the high-pressure CO2 could not vent through the pressure relief valve. The pressure in the drain system vessel continued to build until it reached about 550–700 pounds per square inch gauge (psig) and catastrophically ruptured. The vessel fractured in a brittle mode, producing fragments that flew up to 1,200 feet away.
The ruptured drain system vessel, which was made of carbon steel and measured 15 feet long by 6 feet wide, was rated to a maximum pressure of 125 psig at 650 °F. The blocked pressure relief valve had a set pressure of 15 psig. The scrubbers that drained liquid to the drain system operated at pressures ranging from 450-1,000 psig.
The failed vessel did not have instrumentation installed to allow operators to monitor conditions such as pressure, temperature, or level, and the scrubber liquid level and dump valve position were not recorded. The system’s lack of instrumentation prevented operations personnel from identifying the abnormal operating condition and taking corrective action.
In two previous process hazard analysis (PHA) reviews, the company had identified the potential for CO2 gas to blow through a scrubber dump valve, but this scenario was identified as an operational problem, not a safety problem. The PHAs did not identify the potential for ice or hydrate formation in the drain system due to a stuck-open dump valve. The PHAs also did not include a full review of the downstream closed drain system, as the closed drain system was viewed as a low-pressure utility system with low safety risk.
The company's investigation concluded that the incident resulted from the thermodynamic properties and system pressures not being sufficiently accounted for, resulting in inadequate vessel and piping design, inadequate overpressure protection, and inadequate instrumentation. The investigation recommended, among other corrective action items, that the site create an engineering design standard that addresses hazards associated with introducing high-pressure fluids into drain systems.
The company reported that 5.6 million pounds of carbon dioxide were released. In addition, the company reported that natural gas (111,000 pounds), hydrogen sulfide (2,000 pounds), carbon monoxide (1,400 pounds), sulfur dioxide (1,200 pounds), and nitrogen oxides (NOx) (260 pounds) were also released.
Probable Cause
Based on the company investigation, the CSB determined that the probable cause of the incident was the overpressure of a drain system vessel after a scrubber dump valve became stuck in the open position. Ice or hydrate formed in the vessel outlet piping, blocking the relief path. Inadequate vessel and drain system design and the lack of needed equipment instrumentation contributed to the incident.

Source:CSB.gov

SMALL THINGS MATTER IN ASSET INTEGRITY!

On January 21, 2023, at 4:30 p.m., 30 pounds of hydrogen gas were accidentally released from a shell-and-tube heat exchanger at a refineryin Louisiana. The released hydrogen caught fire, leading to an emergency shutdown, and caused over $1.5 million in property damage.
The hydrogen release originated from the flange between the heat exchanger channel and shell and occurred during unit startup. The heat exchanger was assembled in 2013 and had undergone 43 thermal cycles. During that time, the bolts had relaxed (a normal event) but had relaxed to the point that the flange could no longer contain the hydrogen within the heat exchanger. The company's investigation found that the bolt torque value used to assemble the heat exchanger in 2013 was too low and should have been much higher to prevent leakage.

CITGO found that the assembly instructions for both the incident heat exchanger and a nearby similar heat exchanger listed incorrect torque values that were too low, as the instructions listed the wrong bolt sizes. In addition, CITGO suspected that since it is common practice at the site to assemble similar flanges to similar torque values, the incorrect torque instructions from the nearby heat exchanger may have been applied to the incident heat exchanger. The company determined that the hydrogen may have ignited from contacting an adjacent hot heat exchanger, friction from the release, or a spark.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was under-torqued bolts that had relaxed during 43 thermal cycles until the flange could not contain the hydrogen within the heat exchanger. Inaccurate assembly instructions and the likely application of incorrect assembly instructions for another heat exchanger contributed to the incident.

Source: CSB.gov

WAKE UP, INDIA'S CONSCIENCE!

 WAKE UP, INDIA'S CONSCIENCE!

AI 171 crash June 12 , 2025- aviation sector - 261 killed
Sigachi Industries blast June 30, 2025 - Chemical sector - Over 42 killed
At the outset, my heartfelt condolences to the familes of those who perished in these unfortunate incidents. Nothing can bring back the people who died. The immense grief of the families is unfathomable.

This is a post to highlight how the Indian media, society and regulators treat the two incidents differently.

Strata of society of the people who perished:

AI 171 crash: Those who could afford an international air ticket and some people on the ground.

Sigachi Industries blast - mostly migrant labourers and few operators and supervisors.

Media coverage:

AI 171 crash - Media coverage still hot and on going

Sigachi Industries blast - Interest for about 2 weeks and then died down

Press conferences by regulatory bodies:

AI 171- Continued involvement of both central and state governments

Sigachi Industries blast - a few by the authorities.

Incident invesigation:

AI171 Crash - Investigation ongoing as per ICAO guidelines.Preliminary report made public within 30 days

Sigachi Industries blast - committee formed but no report made public yet.

QUESTIONS:
Isn't the life of a migrant worker, operator, supervisor in a chemical industry the same as an air passenger?

Why is there no PSM rule implemented in India as a regulatory requirement? Though efforts have been made in the oil and gas sector, still most of the other sectors in the chemical industry are left out.

Why isn't an incident in the chemical sector investigated by an independent body reporting to the highest levels of government and reports made public?

Why, after more than 40 years of the Bhopal disaster, we still have to struggle to obtain incident investigation reports of incidents in the chemical sector in India? Some of the available reports do not delve down to the organizational issues including culture and accountability.

Are we waiting for a bigger chemical disaster than Bhopal to wake up?

Introspect and act!

CHECK THE DIRECTION OF ROTATION OF YOUR BATTERY OPERATED TOOLS - THEY MAY CAUSE AN INCIDENT!

On January 17, 2023, natural gas liquid was accidentally released during maintenance of a natural gas liquid storage cavern in Texas. The released natural gas liquid formed a vapor cloud and ignited, causing a large fire. The fire fatally injured one contract worker and seriously injured another. The company estimated the property damage from the incident to be $3.1 million.
The gas storage cavern was used to store natural gas liquid (a mixture of mostly propane and butane). At the time of the incident, contractors were securing components of the wellhead after a maintenance operation and needed to tighten eight lockdown screws into the wellhead. A contractor used a battery-operated impact wrench, which was inadvertently left in reverse. When the contractor attempted to tighten one of the lockdown screws, the screw was accidentally removed, releasing natural gas liquid. This flammable material ignited, injuring the two workers. Both workers were transported to the hospital, where one succumbed to the burn injuries.

Cavern seals were in place for the maintenance work, which prevented any release from the cavern itself. When the lockdown pin was removed, the residual natural gas liquid was released from the hydraulic workover unit, referred to as a “snubbing unit,” which was being used for the maintenance operation. The pressure in the snubbing unit at the time of the incident was 400 pounds per square inch gauge.It was estimated that 16 barrels of natural gas liquids were released. After the incident, the company created action items to require (1) using hand tools to adjust lockdown screws on cavern wellheads and (2) establishing risk management practices to vent pressure from the snubbing unit to the flare system.
 

Probable Cause
Based on the company investigation and  OSHA inspection, the CSB determined that the probable cause of the accidental release of natural gas liquid was the inadvertent removal of a lockdown screw from the wellhead. Contributing to the incident was the use of a battery-operated impact wrench and the presence of pressurized natural gas liquid in the snubbing unit.

Source:CSB.gov

THE IMPORTANCE OF OPERATION READINESS REVIEWS

 On January 17, 2023, at 10:45 p.m., 670 gallons of hot water were accidentally released and pooled at a facility in Louisiana. One employee was seriously injured after stepping into the pool of hot water.

The investigation of the events leading up to the incident began on January 9, 2023, when the facility planned maintenance work on a control valve in the boiler feedwater piping system. Operators observed water leaking past two valves in series, upstream of the control valve, when in the closed position. To allow for control valve maintenance, site personnel developed and executed a plan to route leaking boiler feedwater out of the system by opening two bleed valves (in series) between the leaking valves. Site personnel attached a hose to the bleed valve piping to route the leaking hot boiler feedwater to a nearby sump.
On January 17, 2023, after maintenance work on the boiler feedwater control valve was completed, operators were tasked to recommission the control valve. At about 8:00 p.m., operators lined up valves in the piping system so the control valve could be returned to service. The operations personnel did not use the site’s operational readiness checklist, which included requirements for personnel to evaluate or “walk down” the piping and valve lineup to ensure correct positioning before startup. As a result, when hot feedwater was re-introduced to the piping, the bleed valves remained open, and the temporary hose remained connected to the piping. Hot boiler feedwater began releasing through the open bleed valves and hose.
At 10:46 p.m., the control board operator observed a low boiler feedwater pressure alarm and requested an outside operator to investigate. Personnel identified that the boiler feedwater piping was the source of the low-pressure alarm and, realizing there was a leak, closed an upstream valve to stop the leak. About 670 gallons of hot water were released. At about 11:45 p.m., an outside operator attempted to close the two open bleed valves and inadvertently stepped into a pool of the hot boiler feedwater that had accumulated in a depression. The high-pressure boiler feedwater release may have created or enlarged this hole. The operator was seriously injured when his lower leg was submerged in the hot water above the top of his rubber boot, and the hot water contacted his lower leg and foot.

Probable Cause
Based on the comapny's investigation, the CSB determined that the probable cause of the incident was starting up the boiler feedwater piping system with open bleed valves connected to an open-ended hose, allowing hot water to release and accumulate. An operator subsequently stepped into the pooled hot water, receiving burns to his lower leg and foot. The ineffective application of the operational readiness checklist contributed to the incident by not ensuring that the bleed valves were closed and the hose was removed before the startup.

Source: CSB.gov

TRAPPED AMMONIA CAUSED AN INCIDENT DURING MAINTENANCE

 On January 7, 2023, at approximately 4:55 p.m., about one pound of anhydrous ammonia was released at the a Meats facility in Iowa.
At the time of the incident, the employee was working on an out-of-service ammonia compressor used in the refrigeration system. The compressor had been previously isolated from the system, and the ammonia was understood to have been removed entirely.
When removing the bolts on the flange connecting the outlet piping to the compressor, a burst of ammonia vapor was released directly into the employee’s chest and face. The employee was not wearing respiratory protection because the ammonia compressor was understood to be empty. The injured employee was taken to a hospital for treatment of the ammonia exposure injuries he suffered.
The company's investigation found that the company’s ammonia removal procedure allowed some ammonia to remain trapped between the compressor’s discharge check valve (a valve that only allows for single-direction flow) and an isolation valve. Another valve needed to be opened to remove ammonia from the isolated piping. It was determined that this valve had remained closed because the procedure did not include this valve.

Based on the company's investigation, the CSB determined that the probable cause of the anhydrous ammonia release was disconnecting the outlet piping from the ammonia compressor while some ammonia remained within the equipment. The company’s ammonia removal procedure contributed to the incident because following it did not effectively remove the ammonia from the compressor.

Source:CSB.gov

ICE DAMAGES EQUIPMENT DUE TO ANAMALOUS EXPANSION - ANOTHER INCIDENT

Water exhibits "anomalous behavior" because it expands when cooled from 4°C to 0°C, unlike most substances which contract when cooled. 

On December 24, 2022, at approximately 10:55 a.m., an accidental release of approximately 1,400 pounds of light straight-run gasoline (flammable hydrocarbon) occurred within a hydrotreating unit at a refinery. The release formed a vapor cloud that ignited, resulting in an explosion and fire. One operator was seriously injured due to thermal burns. The company estimated $40 million in property damage. 

From June 17, 2022, until the day of the incident, a steam turbine-driven pump and the surrounding equipment associated with the unit were a temporary dead-leg (a section of piping with no flow). During this period, the pump was locked out for maintenance by closing the inlet and outlet valves to isolate the equipment and piping from the process flow. As a result, the process fluid (hydrocarbon and water) within this equipment was stagnant for 190 days before the incident.

The chemical release occurred during a partial shutdown of the plant due to the severe cold weather. The ambient temperature dropped below freezing between December 21–24, 2022, freezing the water within the isolated pump’s piping (the dead-leg). On December 24, 2022, the daytime temperature increased, and the ice began to melt. At 10:40 a.m., flammable hydrocarbons escaped from the flange of an ice-damaged valve. This release quickly created a flammable vapor cloud, which drifted toward a fired heater (furnace), where it most likely ignited. Simultaneously, two operators, wearing their everyday flame-
resistant coveralls, were performing emergency response tasks in the fired heater area and were engulfed in the colorless and odorless portion of the vapor cloud. The two operators were injured when the vapor cloud exploded.

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the release of flammable hydrocarbons through the flange of an ice-damaged valve. A nearby fired heater most likely ignited the flammable hydrocarbon vapor cloud.
Contributing to the incident was the company's dead-leg identification and management program, which did not identify and protect the temporary dead-leg created during maintenance activities. As a result, the water in this piping froze and expanded during cold weather.
Also contributing to the severity of the incident was the company's emergency response procedure, which allowed the operators to respond to the flammable vapor cloud to “eliminate any source of ignition if it can be done safely.” Under these circumstances, the operators relied (in part) on their senses to determine when and where it was safe to perform emergency response tasks near imperceptible portions of the vapor cloud. The company could have reduced the severity of the event by establishing clear policies and training its operators to respond to the flammable vapor release without putting themselves in harm’s way.

 Source: CSB.gov

ANOTHER INCIDENT DUE TO MOVING EQUIPMENT IN PLANTS

 On December 19, 2022, at approximately 11:10 a.m., an accidental release of anhydrous ammonia occurred at a facility in Massachusetts. Exposure to the toxic ammonia vapor fatally injured one contract worker and seriously injured another contract worker. In addition, the release caused about $4 million in property damage.
The company had hired a contractor to install an electrical (ceiling-mounted) heater to replace an existing leaking steam heater that provided comfort heating inside the facility’s ammonia refrigeration room. The work plan included using a scissor lift to access the installation area. At the time of the incident, two contract workers were on the scissor lift to install the electric heater. While the scissor lift was in an elevated position, the lift was moved forward and then upward, impacting an ammonia refrigeration valve.                                                                                                                                                                       After the scissor lift impacted the piping, a leak formed at the partially severed ½-inch threaded piping connection to the larger ammonia system piping. The anhydrous ammonia was released as a vapor and engulfed the workers. Contractor 1, who was directly in front of the damaged piping, was unable to escape and was fatally injured by the release. Contractor 2, who was further away from the point of release, jumped over the lift’s guardrail to escape from the area.
Two employees heard the sound of the release and saw the ammonia vapor cloud through a door window. One of these employees grabbed a two-way radio and instructed maintenance to initiate an evacuation of the building. Alarms in the ammonia machine room and throughout the building were activated, alerting all employees to evacuate from the building. Evacuating employees found Contractor 2 outside the building. After checking on Contractor 2, one of the employees called emergency responders. Emergency responders recovered Contractor 1’s body from the scissor lift and transported Contractor 2 to a nearby hospital to treat his serious injuries.
Approximately 22,000 pounds of ammonia was released during the incident.

Source:CSB.gov

DESIGN YOUR SAFETY DEVICES DISCHARGE CORRECTLY!

 On January 15, 2022, at 4:51 a.m., 201 pounds of hot methylene diphenyl diisocyanate (MDI) were accidentally released, seriously injuring two workers at a facility in Louisiana.
The company's investigation of this event concluded that the accidental release occurred when a rupture disc activated prematurely. The design activation pressure was 30 pounds per square inch (psi), and process data indicated that this emergency pressure-relief system activated at about 13 psi.

The equipment protected by this rupture disc was typically operated under vacuum conditions. At the time of the incident, however, the equipment was operating at an elevated pressure due to a problem that had developed within the system used to create and maintain the low-pressure (vacuum) conditions. Although the operating pressure was elevated, it was within safe operating limits.
When the rupture disc activated, a 400-degree Fahrenheit mixture of liquid and vapor MDI discharged into 8-inch piping that was vertically orientated downward and ended about eight inches above the concrete floor. At the time of the incident, non-essential workers were not restricted from the area near the rupture disc discharge piping because the system was operating within the safe operating limits.                               
When the high-velocity, two-phase mixture exited the discharge piping, it hit the solid floor, spraying two contract maintenance workers installing a pump near the rupture disc’s discharge piping. The two maintenance workers were hospitalized with thermal burns from exposure to the hot fluid.                                                                                                                                                                  Although Rubicon’s process hazard analysis had identified personnel exposure to hot MDI as a potential consequence of activating the rupture disc, the company had not mitigated the potential hazard of personnel working near the rupture disc discharge piping.

Source:CSB.gov

"IGNITION SOURCES ARE FREE"

 On October 6, 2021, an accidental release of crude oil and produced water occurred during vacuum truck loading operations at  a facility. An unknown amount of flammable vapors from the released fluids ignited, resulting in a flash fire that seriously injured the vacuum truck driver.
An emulsion layer periodically developed at the oil and water interface within the heater treater at the facility and grew thicker over time. The presence of the emulsion layer impaired the heater treater’s efficiency. To address this problem, the company periodically removed the emulsion layer by transferring fluids from the heater treater to a vacuum truck.
The company's investigation identified the sequence of events as follows:
1. The contractor vacuum truck driver discussed the planned work with an operator, and the operator approved the truck driver to start the loading operation;
2. The vacuum truck driver connected a three-inch hose between the truck and the heater treater;
3. The driver opened valves on each end (the truck inlet valve and the process valve);
4. After these valves were opened, produced water and crude oil flowed from the pressurized heater treater into the vacuum truck (the truck’s vacuum pump was not operating);
5. When the vacuum truck driver detected crude oil, he closed the process valve on the heater treater to stop additional fluid from entering the hose; and
6. The vacuum truck driver disconnected the hose from the heater treater, and the contents flowed out of the truck and into the atmosphere through the open hose. The released fluid contained flammable hydrocarbon vapor that ignited, creating a flash fire that seriously injured the driver.
The company’s investigation concluded that the fired heater treater components may have been the ignition source. The heater treater burner was inadvertently left online during the vacuum truck loading operation. The company's investigation team did not eliminate static electricity as the potential ignition source because the hose components were non-conductive, and the truck was not electrically bonded or grounded.
The company's investigation identified additional causal factors, including:
A. The procedures, training, and administrative controls did not effectively control the hazards associated with draining an emulsion layer from its heater treaters;
B. No safety or hazard analysis was performed to identify or control potential hazards before performing this work;
C. There was no pre-determined location to electrically ground or bond the vacuum truck; and
D. Using system process pressure from the vessel to transfer the fluid to the vacuum truck rather than using the truck’s vacuum pump to pull the fluid into the truck contributed to the incident.

Siurce:CSB.gov

BEWARE OF MOVING EQUIPMENT IN PLANTS......

On June 14, 2021, at approximately 6:50 a.m., an accidental release of mineral oil occurred at a facility  that led to the permanent closure of the facility
Leading up to the incident, a contractor was hired to replace insulation on its heating oil piping system. To reach a portion of this piping, the contractor used a scissor lift.
As the contractor began raising the scissor lift near the work location, the top guardrail of the lift impacted a section of a ½-inch piping assembly that included a valve. This threaded piping was connected to a four-inch pipe containing mineral oil, which was part of a hot oil system that provided heating for other process equipment.
After the guardrail impacted the piping, a leak formed at the ½-inch threaded connection to the four-inch piping. The hot mineral oil, which was over 500 degrees Fahrenheit, was released as an aerosol. The mineral oil formed a white cloud and created the electrostatic conditions that most likely ignited the mineral oil.

Upon seeing the white cloud, workers responded to the release. The workers tried to contain the spill by placing absorbent barriers around mineral oil on the floor. Additionally, the workers shut off the oil heating system. The workers also lowered the pressure of the hot oil system, but the leak could not be remotely isolated from a safe location. As a result, the mineral oil ignited, and the fire grew and destroyed the facility.
The CSB estimated that less than 100 pounds of mineral oil was released between the start of the release and the time of ignition.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the mineral oil release was piping damage that resulted from force applied by the scissor lift. The flammable mineral oil was most likely ignited by static electricity. The hot oil system did not allow for the remote isolation of the damaged piping. Had they been able to stop the flow of mineral oil through remote isolation from a safe location, the incident could have been less severe.

Source:CSB.gov

CONFIRM CYLINDERS ARE EMPTY BEFORE DISCONNECTING!

On December 3, 2020, at approximately 2:30 p.m., an accidental release of toxic chlorine gas occurred at a facility in Point Comfort, Texas, and seriously injured one employee 

At the time of the incident, four employees were involved in replacing an empty chlorine container with a full 2,000-pound (one-ton) container at the facility’s Ethylene Glycol unit. Chlorine gas was used as a biocide in its cooling water treatment system.
As a employee disconnected the supposedly empty chlorine container from the process equipment, chlorine gas escaped because, unknown to the workers, the container still held 1,250 pounds of chlorine (62.5 % of its original inventory). Because the chlorine container was understood to be empty, the  employee was not wearing respiratory protection. After three failed attempts to stop the release, an emergency responder was able to close the chlorine container’s vapor valve and stop the release after 50 minutes.

The employee who disconnected the chlorine container was life-flighted to the hospital after showing respiratory difficulties from exposure to chlorine. Formosa reported that approximately 10 pounds of chlorine gas were released.

The investigation team recommended installing a scale for each container to address the false indication of an empty ton container of chlorine in the future. Knowing the weight of the chlorine container could help plant workers confirm that a container is empty or alert them that the container is not empty. In addition, the company strengthened its operating procedures to clarify that respiratory protection is needed when changing a chlorine container.

Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the accidental chlorine release was disconnecting process equipment from the chlorine container while the system was pressurized with chlorine. The lack of instrumentation or other equipment to allow the operators to confirm the amount of chlorine in the container contributed to the incident. Another factor contributing to the incident was the use of chlorine in the cooling water treatment program. Had the company used a safer alternative, such as bleach, this incident could have been prevented.

Source:CSB.gov

LINE OPENING INCIDENT

 On July 24, 2020, at 1:20 p.m., an accidental release of approximately 100 milliliters of silicon tetrachloride seriously injured two contract workers at a facility in Tennessee.

At the time of the event, contract workers were disassembling a 2-inch flange to remove a blind (a solid metal plate used for isolating equipment) before reinstalling a section of piping that had been taken out and cleaned. This type of equipment opening is commonly called a “line opening” or “performing a line break.”
The contract workers performing the line opening wore personal protective equipment (“PPE”), including full-face respirators, chemical gloves, and fall protection. The contractor’s pre-job safety analysis form did not require using chemical suits or rubber boots because the piping system had been taken apart the previous day for the cleaning activity. This additional protective equipment was required by the safe work permit, authorizing the contractor to perform the line opening work. As the workers disconnected the flanged connection bolts, they were splashed with corrosive liquid silicon tetrachloride that had leaked past an isolation valve and pressurized the piping, seriously injuring the two contract workers with chemical burns.
 

Based on the factual investigative information the CSB obtained from the company and OSHA, the CSB determined that the probable cause of the accidental silicon tetrachloride release was the failure to effectively isolate, flush, and drain the piping system before turning it over to the contract workers for disassembly. Not using PPE that could protect the workers from being splashed with corrosive silicon tetrachloride contributed to the severity of the incident.

Source: CSB.gov

TEMPORARY CHANGES MAY LOOK SIMPLE BUT ARE DANGEROUS!

 On April 11, 2020, at 11:25 p.m., a spent caustic release occurred at a facility in Louisiana. One operator was seriously injured by skin exposure to the corrosive liquid.

At the time of the incident, the operator was implementing a temporary procedure to remove liquid from a chemical hose connected to fill a portable storage tank (“frac tank”) that the company was using to store spent caustic. Once the frac tank was full, air was used to clear the chemical hose before moving the hose to an empty frac tank.
When the operator opened the valve at the frac tank, pressurized fluid in the chemical hose flowed into the tank, erupting spent caustic from the unsecured top hatch (manway) and splashing the corrosive liquid onto the operator. The operator's personal protective equipment (PPE) did not protect from caustic liquid exposure. It took the operator about two minutes to reach the closest plant safety shower to rinse off the corrosive liquid because there was no safety shower near the frac tank, despite the site requirement for a safety shower within 25 feet of the tank. The operator then went to the control room and reported the incident. Emergency responders transported the operator to a hospital, where she was admitted for treatment of chemical burns.

It was  estimated that approximately 20 gallons of spent caustic were released. The spent caustic was comprised of water, sodium hydroxide, sodium sulfide, sodium carbonate, and pyrolysis gasoline.

Source:CSB.gov

INCIDENT DUE TO "WE DO NOT KNOW WHAT WE DO NOT KNOW"

 On April 10, 2020, at 12:46 a.m., a mixture of hydrogen and hydrocarbon gas was accidentally released within the Hydrocracker unit of a refinery/ The flammable gas formed a vapor cloud that ignited, resulting in an explosion and fire (Figure 1) that seriously injured one operator and caused approximately $5.15 million in property damage.
After a heavy rainstorm, the flow to the Hydrocracker unit’s flare began increasing. Operators found that although the unit’s cold separator was operating at normal working pressure, its emergency pressure-relief valve had malfunctioned and remained open, allowing flammable gas to flow into the flare system. Two managers at the refinery phoned the complex manager, who gave the onsite managers verbal approval to proceed with immediate actions to stop the flaring by reseating the safety device.
The company uses the term “reseating” when referring to its practice of trying to close and seal a malfunctioning emergency pressure-relief valve by incrementally closing the inlet (upstream) isolation valve to lower the inlet pressure to the safety device. If the emergency pressure-relief device successfully closes (reseats), its inlet valve is reopened, which returns the safety device to its protective condition.

Onsite managers used the refinery’s management of change process for isolating a safety device for approval for the operations team to perform the urgent reseating activity. One of the onsite managers—the operations supervisor—worked with two field operators to perform the reseating activity while the board operator monitored the system pressure from the control room. Operations personnel raised safety concerns related to accessing either of the two 6-inch inlet valves, resulting in a decision to close the 20-inch outlet valve on the downstream side between the emergency pressure-relief valve and the flare system instead of trying to close one of the inlet valves.

The hazard of closing the outlet valve instead of closing one of the inlet valves was not recognized. Although the two 6-inch inlet valves were designed for high-pressure conditions—2,470 pounds per square inch (psi), the 20-inch outlet valve to the flare system was rated for just 275 psi. Closing the 20-inch outlet valve would subject this valve to about 2,100 psi of pressure from the flammable vapor flowing from the cold separator, much greater than the valve’s 275 psi pressure rating.
When the operations team had the outlet valve about 90 percent closed , the valve failed—releasing a high-pressure mixture of hydrogen and hydrocarbon vapor into the surrounding air. The flammable gas formed a vapor cloud, which ignited resulting in the explosion and fire.

Source: CSB.gov

Become Natech Savvy - Aimee Russell highlights the issues you probably haven’t thought about when it comes to extreme weather risks and what you should do about them

HAVE you ever thought about the impact a natural hazard could have on your site? Have you identified which natural hazards are even credible? For upper tier Control of Major Accident Hazards (COMAH) establishments there is an expectation from regulators that duty holders are aware of external hazards, but what does that really mean? What about sites which do not fall under these regulations? Does that mean they shouldn’t be concerned with such hazards?

Read the article in this link 

Introduction To Pipe Supports - GOOD VIDEO

PDO Safety Day 2024 - Learning from incidents

NITROGEN CYLINDER RUPTURED

 SOURCE: https://s3.eu-west-1.amazonaws.com/resources.stepchangeinsafety.net/downloads/SF-18-24.pdf

Nitrogen cylinder ruptured
What happened
A high pressure Nitrogen cylinder in a quad of 12 cylinders located on a drill rig floor ruptured without warning. The cylinders were charged to 2,400psi and were not connected to anything else at the time of the incident. The rack was destroyed and the other cylinders in the quad were propelled by the blast up to 15m away.

Why did it happen
The base of the cylinder that ruptured was heavily corroded. Other cylinders in the quad had evidence of similar but less severe corrosion.
The cylinders were 9 years into their 10-year hydrotest cycle, and had been visually inspected by the supplier in accordance with applicable industry guidance, when they were refilled some three months before the incident, before being loaded out to the rig. However, the severe corrosion that caused the rupture was not spotted during this inspection;
The cylinder that ruptured was located in the middle of the quad and therefore not easy to properly inspect without disassembly of the quad.
Calculations showed that the fatal blast zone for a single cylinder of this size pressurised to 2,400psi would be around 1.5 metres. The severity of the blast caused the rack to be destroyed and the other cylinders to be propelled across the deck.
Lessons learned
• Are the cylinders on your facility or vessel certified and in good condition?
• Are you able to see the condition of all cylinders in every rack?
• Are all cylinders located on a free draining base to minimise corrosion?
• Do you know what level of visual inspection of cylinders/quads is provided by your supplier?
• Are all cylinders on your facility stored and located in accordance with the relevant industry regulations?