INCIDENT DUE TO LACK OF PROPER CONTROL OF HAZARDOUS ENERGY

On January 19, 2023, less than five pounds of hot water and pulp were accidentally released, seriously injuring one employee at a paper mill in Georgia, a facility that produces paper products.
The employee had been tasked with inspecting and cleaning a pulp screen. The pulp screen equipment’s drain system had plugged (an abnormal condition), causing water and pulp to remain inside the equipment. With the plugged drain, the process conditions allowed the typically warm water to become hot.
When the employee started unbolting the equipment flange to access the screen, hot water and pulp sprayed out of the flange, contacting the employee. The employee received thermal burns requiring hospitalization. Miscommunication and ineffective training allowed the worker to open this equipment before it was effectively isolated and de-energized.
After the incident, the company added safety interlocks to shut down this equipment automatically during certain abnormal conditions.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was opening equipment that contained pressurized hot water and pulp. Contributing to the incident was ineffective communication and training on the site’s procedure to control hazardous energy.

Source: CSB

HAPPY NEW YEAR!

 TO ALL MY BLOG FOLLOWERS, 

 

CHANGES CAUSE AN INCIDENT

 On August 29, 2024, at 6:45 p.m., flammable vapors were accidentally released from a reactor at a refinery in Houston, Texas, resulting in a fire at the facility. The incident resulted in $16.8 million in property damage.
At the time of the incident, employees noticed flames coming from the head of a reactor in the fluidized catalytic cracking unit (“FCCU”). The flammable vapor released from the reactor likely caught fire from autoignition because the reactor operated at 960 degrees Fahrenheit (℉), which is above the autoignition temperature for most of the hydrocarbons released. Unit operators put out the flames with a fire extinguisher. The company reported that over 400 pounds of flammable vapors were released during this incident.

The company’s investigation determined that the flammable chemicals were released through an 8-inch crack in the wall at the top (head) of the reactor. Additionally, the company found other cracks in the reactor that were up to 67 percent of the wall thickness. The cracks were created by a damage mechanism known as corrosion fatigue. Corrosion fatigue is caused by cyclically applied stress under corrosive conditions. Internal cracks formed at the top of the reactor, an area that was consistently exposed to sulfur-containing chemicals commonly found in petroleum refining. This sulfidation corrosion was coupled with temperature swings over 200℉, which applied stress to the vessel through expansion and contractions of the metal with the temperature changes. The company found that there had been more than 50 temperature cycles since 2011. Additionally, platform supports were added to the reactor head in 2001, contributing to the cracking by increasing the stress exerted on the vessel. Stress-assisted preferential sulfur penetration is the specific type of corrosion fatigue responsible for the 8-inch crack.

The investigation also revealed that the company was not inspecting the reactor’s walls for cracking because the site’s mechanical integrity program did not identify corrosion fatigue as a potential damage mechanism. The company attributed this gap to following industry standards that did not identify corrosion fatigue as a common FCCU reactor damage mechanism.

Probable Cause
Based on the company’s investigation, the CSB determined that the probable cause of the accidental release was an 8-inch corrosion fatigue crack through the wall at the top of the reactor. Adding platform supports to the top of the reactor contributed to the incident by increasing the stress exerted on the vessel during the temperature changes. The company’s mechanical integrity program contributed to the incident by not identifying corrosion fatigue as a potential damage mechanism for its FCCU reactor.

Source: CSB.gov

HUMAN FACTORS CAUSED A FURNACE TUBE RUPTURE

 On July 12, 2024, at 7:00 p.m., a mixture of nitrogen and benzene was accidentally released into the firebox of a fired heater. The benzene ignited, causing a fire at a facility in Texas. The company estimated that the incident resulted in $9.8 million in property damage.

The incident occurred while employees were restarting the fired heater after Hurricane Beryl damaged offsite power systems, disrupting water availability and causing a shutdown of the facility on July 8, 2024. Process fluid should circulate through the fired heater’s tubes during the unit startup. The company's investigation found that the process flow through the fired heater was reduced because two misaligned valves (open valves that should have been closed) allowed some of the flow to bypass the heater.
Without enough fluid flow to remove heat, the tubes reached temperatures as high as 1,900 degrees Fahrenheit, far above the safe operating temperature. The high-temperature condition weakened the tubes in the upper portion of the fired heater and caused some of them to rupture, likely from short-term overheating.

The company reported that the ruptured tubes released approximately 16,000 pounds of nitrogen and 630 pounds of benzene into the firebox. The operating burner flames ignited the flammable benzene, resulting in a fire.
The company's investigation reviewed the company’s process hazard analysis and determined that the existing instrumentation safeguards did not protect against low-flow or high-temperature conditions in the fired heater during startup. The investigation also found that human factors caused valve alignment errors that allowed some process flow to bypass the furnace. These included vague radio communications, multitasking due to a high startup workload, stress from the major hurricane, perceived time pressure from delays, and implementing an unfamiliar startup, which was infrequently conducted.
After the incident, the company provided its operations team with fired heater startup simulator training and improved the company’s instrumented safeguards for the fired heater. These instrumentation upgrades included an alarm and a safety interlock to protect the equipment when the temperature difference between any individual tube pass temperature and the combined process fluid temperature exiting the furnace indicates that there is insufficient process flow through the tubes.

Probable Cause
Based on The company's investigation, the CSB determined that the probable cause of the incident was ruptured process tubes in a fired heater. Short-term overheating likely resulted in the tubes rupture, releasing nitrogen and benzene into the firebox. The flames from the fired heater’s operating burners likely ignited the benzene. Human factors resulted in two valve misalignments that contributed to the incident by creating a low-flow condition through the tubes, which increased the temperature in the tubes. A lack of instrumentation safeguards to protect the fired heater from low-flow and high-temperature conditions also contributed to the incident.

Source:CSB.gov

H2S LEAK KILLS ONE AND SERIOUSLY INJURES ANOTHER

On May 29, 2024, at about 3:15 p.m., several pounds of hydrogen sulfide and carbon monoxide gas were released at a facility in Colorado. As a result of the release, one employee was fatally injured and another  employee was seriously injured due to inhalation of the gases.

The company's investigation found that at the time of the incident, two employees were performing maintenance work on a pump at the facility. The workers closed an isolation valve and removed approximately half of the bolts on the connection before water began leaking from the flange onto the floor. The workers and their supervisor determined that the isolation valve was not properly seated. The two workers left the pump house to get a tool to help close the valve. While the workers were gone, hydrogen sulfide and carbon monoxide gas began releasing into the pump house (which was approximately 400 square feet and 8 feet tall).
When the workers reentered the pump house, they experienced symptoms consistent with toxic gas exposure. One of the workers lost consciousness (“Worker One”) when trying to escape up a ladder. The other worker (“Worker Two”) escaped the pump house. Worker Two explained the situation to another supervisor, and emergency responders were contacted. A third supervisor and two other employees attempted to rescue Worker One, but they realized that the area was dangerous and tried to escape. During the escape, one of the attempted rescuers (“Rescuer One”) fell, appeared to be unconscious, and could not self-rescue. An air monitoring device that was lowered into the pump house sounded an alarm for both hydrogen sulfide and carbon monoxide, indicating the concentrations of the gases were above 20 and 35 parts per million, respectively. Because of the high concentrations of the gases, employees halted their rescue attempts and waited for emergency responders to arrive.
Emergency responders with self-contained breathing apparatuses were able to rescue the two employees from the lower pump house and transport them to a local hospital for medical treatment. Rescuer One died at the hospital later that day. Worker One survived and was released from the hospital after a few days. After the incident, The company classified the lower pump house as a confined space and installed continuous air monitoring equipment.

Probable Cause
Based on The company's investigation, the CSB determined that the probable cause of the incident was the pump’s leaking isolation valve that allowed hydrogen sulfide and carbon monoxide gas to enter the pump house when the flange was opened. Not identifying or controlling these toxic gases from being released in this part of the process contributed to the incident. Contributing to the severity of the incident was that the lower pump house was not classified as a confined space, which allowed employees to enter without safeguards such as respiratory protection, air monitoring, attendants, or a rescue plan.

Source: CSB.gov