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