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