COMPETENCY AND COMMUNICATION - THE ESSENCE OF PROCESS SAFETY

 At 9:20 a.m., a rupture disc of a reactor used to produce an organomagnesium compound burst when the reactor’s internal pressure rose too high. The incident was caused by a nonconforming mixture that had formed in the reactor. First, the ambiguous instructions led a technician to add an insufficient amount of initiator. Then, seeing that the reaction had not yet started, a second technician added more reagents. The process sheet indicated that the reagent could be added after, but only after receiving the supervisor’s approval. 

The operation took place on a Saturday and the chemical engineer belatedly informed the on-duty engineer. This lack of communication between the workers of both shifts and the technicians’ lack of experience are what set the stage for the incident. 

The operator subsequently implemented a number of changes : tracking of technicians who are accredited to carry out synthesis operations has been reinstated ; the process sheet now indicates the amounts of reagent to be added and includes hold points for the start of the reaction ; the reaction may no longer be carried out over the weekend and it must be scheduled at the beginning of a shift so that workers may monitor it from start to finish. In addition, the operator conducted an in-depth review of organomagnesium compound synthesis in order to establish production standards and problem-management guidelines applicable at all its similar production sites.

Source:Aria database

CONFUSION DURING A MAJOR LOPC CAUSES WRONG ACTION TO BE TAKEN

In a petrochemical complex, an ethylene (a highly flammable gas) compressor was in stable operation when a sudden drop in pressure occurred at 5:33 p.m., accompanied by a loud noise. The gas detectors in the zone became saturated, and a 2nd level alarm was triggered in the unit’s control room, as well as in the control room controlling the nearby compressor and at the safety station. The compressor began to vibrate. Its motor stopped but not its ethylene supply.

Confusion over which compressor was leaking
Not knowing which compressor was causing the leak, the shift crew of compressor No. 1 contacted the crew in charge of compressor No. 2. The latter crew persuaded them it was compressor No. 2 that was to blame. Crew No. 1 left their control room to help them. The alarms and parameters indicating the malfunction of compressor No. 1 (pressure drop) were not taken into account since the control room had been deserted.

The two shift crews, joined by the internal fire brigades, approached the area of the accident but were unable to enter due to the deafening noise. They encountered a flammable cloud of ethylene measuring 4 m high x 100 m, with visible droplets. The firefighters protected the nearby units with water curtains. Around 5:45 p.m., the shift leader 1 consulted with the shift leader in charge of the neighbouring unit. A leak on the ethylene supply network was suspected. Two operators, equipped with hearing protection, moved through the cloud, protected by a water curtain, to reach the network’s manual shut-off valves. They were able to close the valves manually, ending the leak. The cloud rapidly dispersed. The operators returned to the control room and closed the local supply valve of compressor 1. 8 t of ethylene (354 kg of flammable mass) was released in 21 minutes.

ROOT CAUSE: Valve ejection due to incorrect tightening and a non-compliant seal
The hatch and the valve porthole of the second stage of compressor 1 were found 6 m away. One stud from the hatch was severed (sudden brittle-type rupture), while the other five studs remained in place, three of which were missing their nuts and exhibited torn threads. These studs are compliant but had never been replaced since the compressor was commissioned 16 years ago. An expert assessment showed that the valve’s copper seal was not annealed at the time of its installation, contrary to procedure and the other seals on the equipment. It was therefore not as flexible and less able to absorb stresses. This defect, combined with a bolt tightening error on the verge of plastic deformation, led to fluttering in the stack and its rupture.

If the emergency stop had been activated, the leak could have been stopped more quickly as it shuts down both the motor and the ethylene supply. The operators believed that the motor shut-down because of vibration was sufficient. After the accident, the compressor was equipped with an emergency stop triggered by gas detection. However, the manual emergency stop remains in operation should this detection system fail.

Source: Aria database

DO YOU CONSIDER ACCIDENTAL REVERSAL OF PNEUMATIC HOSE CONNECTIONS TO CONTROL SYSTEMS DURING HAZOP?

 A reactor exploded in a fine chemicals plant during the chlorination of an alcohol by thionyl chloride (SOCl2 ). The relatively non-exothermic reaction took place in a solvent medium (1,2 dichloroethane or DCE), under a slightly lower pressure and a temperature of 70°C maintained by means of steam injection. The reactor initially contained the SOCl2 in solution in the DCE, with the alcohol being added under close monitoring for 30 hours. 

At the time of the accident, the reactor was being fed for three hours by successive 200- litre loads of alcohol, with the first injection still incomplete. Monitoring performed by two technicians, one of whom was a trainee, included an hourly reading of both the temperature and pressure drop; no anomaly had been observed until that point. Upon hearing a noise accompanied by a break to the protective disc on the glass column connected to the reactor and noticing smoke around the disc joints, the technician turned the feeder control box selector switch to the “off” position. As he closed the alcohol feed valve and was making his way to the valve used to shut down steam injection, he spotted that leaking on the column was becoming more persistent. He immediately left the unit, requesting that a co-worker follow him out — at which point the explosion happened. A rupture disc calibrated at 0.3 bar and the glass fixtures on top of the device burst. The explosion or toxic gases emitted once the equipment had broken killed the trainee technician, who did not exit the premises quickly enough. 

The feeder was equipped with two valves. The upper one (loading side) was found in the closed position while the lower valve (reactor side) was open with a reversal of the pneumatic control hoses. These recordings supported the hypothesis of an accidental addition of water into the reaction medium via the feeder. The laboratory simulation of such an addition found that the SOCl2 hydrolysis with the formation of SO2 and HCl led to a sudden pressure rise. 

Source:Aria database

LOOK ALIKES CAUSE AN INCIDENT

On May 20, 2025, at approximately 8:15 a.m., approximately 8,000 pounds of toxic chlorine were released, seriously injuring one employee at a facility in  Texas . The community was ordered to shelter in place, and estimated that the incident resulted in approximately $23 million in property damage.

On the day of the incident, it was planned to replace a rupture disc (RD-217N) in the chlorine liquefication unit. This safety device protected the E-209A heat exchanger 

 

The company gave two contract maintenance workers the work package and a permit to replace the RD-217N rupture disc. At approximately 8:10 a.m., one of the maintenance workers began disassembling the RD-217N rupture disc holder using a battery-powered impact wrench. In addition to the standard protective equipment, the maintenance worker wore an air-supplying respirator with a 30-minute air bottle. At 8:15 a.m., liquid chlorine at a pressure of 100 pounds per square inch began releasing from the partially disassembled RD-217N rupture disc holder. The maintenance workers evacuated from the area. Alarm horns in the unit were activated after chlorine gas detectors identified the release. Local officials issued a shelter-in-place order for the cities. At 9:03 a.m., emergency responders closed Valve 1 to stop the release.
During the response to the incident, one emergency responder’s 30-minute air supply depleted. He switched to a cartridge-style escape respirator to exit the area, but the respirator likely became saturated with chlorine, causing him to inhale the toxic vapor. Other emergency responders then transported him to a hospital, where he was admitted for treatment.
The company's investigation found that although the work planning documents showed that RD-217N was to be replaced, its operations team had mistakenly isolated, cleared, and tagged a different but nearly identical piping system—heat exchanger E-209B—to replace a different rupture disc, RD-217S. As a result, the operations team did not isolate, clear, or tag the E-209A heat exchanger and the piping associated with RD-217N. This equipment was operating when it issued the contract workers a permit to replace the RD-217N rupture disc. The unit operator who issued the permit and the maintenance workers did not perform a field walk-through of the job. In addition, the contract workers did not review or sign the equipment isolation plan or the tag that identified the rupture disc holder to be opened. Seeking to do so should have revealed that RD-217N was in operation and had not been prepared for replacement.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the chlorine release was the mistaken disassembly of a rupture disc holder in an operating chlorine system. A breakdown in the equipment opening and control of work programs contributed to the incident, including the absence of a pre-job site walkthrough that should have allowed plant operators and the maintenance crew to verify the rupture disc had been prepared for replacement.

Source:CSB.gov 

IMPROPER OPERATION READINESS REVIEW DUE TO HUMAN FACTORS CAUSED AN INCIDENT

 On February 23, 2023, at 8:15 p.m., an accidental release of approximately 164 pounds of hydrocarbons (pentane and heavier hydrocarbons) occurred at a Refinery in Texas. The hydrocarbons were released from an open bleed valve on a crude unit heat exchanger during startup. The hot hydrocarbons ignited (autoignition), causing a fire that damaged nearby equipment. The company estimated the property damage from the incident to be $2.3 million.

On February 12, 2023, the crude unit heat exchangers were shut down for cleaning. Ten days later, on February 22, refinery operators prepared to put the heat exchangers back into service after the cleaning. During the day shift on February 23, they purged air from the heat exchangers to prepare it for startup.

Night shift operators then continued readying the heat exchangers for startup. They obtained the energy isolation drawing, which was used to document which valves had been locked in the open or closed position to allow for safe cleaning of the heat exchangers.
The operators walked down the equipment, removed the locks indicated on the energy isolation drawing, and ensured the valves were lined up in the correct position for startup. The operators believed they had addressed all the valves documented on the energy isolation drawing. Unknown to the operators, however, a bleed valve on top of the heat exchangers remained locked open when the lock should have been removed, and the valve should have been closed. The company's investigation report noted that the open bleed valve was not easy to locate visually, and the operators’ ability to see it may have been further impaired when it was dark outside.
As the startup sequence progressed, hot hydrocarbons sent to the heat exchangers flowed through the open bleed valve into ambient air and ignited. The material was released at 562 degrees Fahrenheit (°F) and had an autoignition temperature of 482 °F.
The company stated that the energy isolation drawing was destroyed in the fire; so it is unknown if the locked open bleed valve was shown on the drawing.
Probable Cause
Based on the company's investigation, the CSB determined that the probable cause of the incident was the release and ignition of flammable hydrocarbons when a bleed valve was inadvertently left open during an equipment startup. Contributing to the incident was a lack of a system, such as leak testing, to ensure all valves were in the correct position before the equipment was started up.

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/

 

 

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 

INCOMPATIBLE REACTION DURING PREPARING ACID CLEANING SOLUTION CAUSES 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, 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 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

Know the location of your emergency shutoff valve switches

Employees #1 and #5 through #7 were near the chlorine unloading area at a bleach plant when the gasket of a recently-installed vaporizer failed, releasing between 500 and 700 gallons of liquid chlorine. When Employees #1 and #7 went to investigate the extent and location of the leak, they found an overwhelming concentration of the chemical. They were not using SCBAs, nor was Employee #6, who used the wrong escape route. Employee #5, the bleach plant operator, attempted to find and assist Employee #6. 

Employees #2 through #4 attempted to shut down the vaporizer system but they did not know the location of the one critical shut-off valve, and the key person was not immediately available to help. Employees #1 through #7 suffered chemical burns from inhaling the chlorine fumes; all were hospitalized except for Employee #2.

Source:OSHA.gov

ARE YOU CONSIDERING HUMAN FACTORS DURING YOUR HAZARD IDENTIFICATION?

 An ammonia leak occurred in the machinery room of an unoccupied arena. An employee was attempting to add oil to an ammonia compressor when he observed a leak (fill hose was not attached). Approximately 200 lbs ammonia was released.
Qualified person was trained, but with minimal experience in this procedure. No written procedure was available, and an error occurred while executing the procedure. The shut-off valve type (wrench-operated,
mufti-turn, no position indicator) added complexities to the process.

Source: British Columbia Safety Authority 

Employee Location Monitoring in a Post-Pandemic World

Employee Location Monitoring in a Post-Pandemic World: The COVID-19 pandemic has unearthed a number of challenges for power plant managers. However, technology exists to keep workers safe. Through the use of Location Anchors and WirelessHART infrastructure

Are you identifying human factors in HAZOP studies?

On 6.9.19, at Amsterdam airport, a Boeing 737, aircraft was taxiing in a northerly direction on taxiway Charlie to runway 18C when it received take-off clearance for that runway. The flight crew then drove on taxiway Delta in a southerly direction and commenced the take-off. Air traffic control noticed this and instructed the crew to stop immediately. The crew aborted the take-off run and taxied back to the start of runway 18C, after which the aircraft took off uneventfully.
Source:Quaterly aviation report, Dutch Safety Board, July-September 2019

Are you identifying human factors in HAZOP studies?