Safety Critical Task Analysis (SCTA)

"Human activities are involved in different aspect of operation of a chemical facility. Starting from design, construction, commissioning, operation, maintenance till decommissioning, human is involved. For safe and reliable operation, high human reliability is required in all phases of lifecycle of the facility. However human errors have contributed to many major industrial accidents in Chemical facilities in the past. Few examples are listed" in this link

Explosion caused due to a catalytic effect of contaminant in the reactor at a resin intermediate manufacturing plant

  "An explosion occurred at a plastic intermediate plant. Raw material was decomposed explosively by contaminant on heating and agitating after charging the raw material into the reactor. The reactor exploded and a fire occurred. Due to imperfect valve operations during vacuum distillation work for a previous run, sodium hydroxide for exhaust gas neutralization flowed in reverse to the reactor. As this alkali became a catalyst, a runaway reaction occurred. "

Read about the incident in this link

DANGERS OF STARTUP AND SHUTDOWN OPERATIONS

 https://int-enviroguard.com/blog/dangers-of-start-up-and-shutdown-operations/

Lessons learned from reactive chemical incidents

https://www.aiche.org/resources/publications/cep/2022/february/spotlight-on-safety-lessons-learned-reactive-chemical-incident

“Even a simple task can turn deadly if it is not performed properly,”

"The accident took place in July 2021 at the LyondellBasell Industries complex in La Porte, near Houston, in the acetic acid production unit. The facility is the third-largest acetic acid producer in the US. The CSB’s report found that the inadvertent removal of pressure-retaining components of a valve caused the release of nearly 75,000 kg of an acetic acid mixture. The incident killed two contract workers, severely injured a third, and sent some 29 others to hospital.


“Even a simple task can turn deadly if it is not performed properly,” CSB Chairperson Steve Owens says in a press release. The incident involved a common plug-valve system, and CSB found similar serious incidents in which these valves were taken apart when removing connected equipment."

Read the article in this link

How to prevent runaway chemical reactions - EPA

" PROBLEM: Many industrial chemical processes involve exothermic (heat generating) reactions. Uncontrolled, or runaway, reactions can occur as a result of various situations, such as mischarged raw materials, failure of a reactor's cooling system or the presence of contaminants. If the heat generation exceeds the reactor's ability to remove it, the reaction can accelerate - or run away - and cause the temperature and pressure to increase. A sudden energy release from such an uncontrolled reaction has the potential to harm workers, the public, and the environment. The following Case Study aims to increase awareness of possible hazards connected with exothermic reactions."

Read the article in this link 

Runaway reactions

"A typical runaway scenario involves reactants being charged into a reactor at room temperature and heated with stirring until the reaction temperature is reached. Temperature is held constant to optimise cycle time and yield. On completion, the reactor is cooled and emptied. However, if no provision is made in the process to account for cooling failure at reaction temperature e.g. due to power failure or operator error (forgot to start the stirrer), etc. then unconverted material still present in the reactor may react at an uncontrollable rate proportional to the amount of unreacted material. This may lead to over-pressure in the vessel and subsequent rupture by virtue of the normal reaction exotherm. Alternatively, a secondary decomposition reaction may be initiated and the heat so produced may lead to yet a further increase in temperature and eventual runaway conditions1 . The prime causes of runaways are associated2,3 with – process chemistry – inadequate design – substandard operational procedures – lack of training – raw-material quality control – temperature control – agitation – mischarging of reactants – maintenance – human factors (which may impact all of the foregoing)".

Read the article in this link 

Accident due to agitator lubricating fluid entering reactor

 "This report investigated the causes of a chemical release accident caused by an abnormal reaction and recommended certain safety steps to prevent the reoccurrence of similar accidents. An abnormal reaction occurred during the input of raw materials (t-BuOH, KMnO4, and H2O), and some foreign impurities (4% MeOH, 13% glycerin) that may have influenced the reaction were identified. The MeOH may have entered the reactor during t-BuOH reuse or the cleaning of mechanical parts, and glycerin was released from the seal oil reservoir to enhance lubrication with the agitator in the reactor. The pilot test carried out to reproduce the abnormal reaction revealed a rapid reaction, with an increase in the mixture temperature when the KMnO4 and glycerin (13%, released from the broken seal oil reservoir) were added to the mixture that contained 96% t-BuOH and 4% MeOH (impurity). Furthermore, some deficiencies in the safety system and some human errors were discovered. The reactor was not equipped with either a safety instrumental system or an automated emergency shutdown system, and the workers did not wear PPE. These factors could have had a significant impact on the accident".

Read the report in this link 

Hazard Alert: Combustible Dust Explosions

 Source:OSHA.Gov

Hazard Alert: Combustible Dust Explosions
Combustible dusts are fine particles that present an explosion hazard when suspended in air in certain conditions. A dust explosion can be catastrophic and cause employee deaths, injuries, and destruction of entire buildings. In many combustible dust incidents, employers and employees were unaware that
a hazard even existed. It is important to determine if your company has this hazard, and if you do, you must take action now to prevent tragic consequences 

See the link....

https://www.osha.gov/sites/default/files/publications/osha3791.pdf

DUST EXPLOSIONS CAN BE CAUSED SUBSTANCES YOU WOULD NEVER IMAGINE!

Source: OSHA.Gov: 

Does your company or firm process any of these products or materials in powdered form?
If your company or firm processes any of these products or materials, there is potential for a “Combustible Dust” explosion

https://www.osha.gov/sites/default/files/publications/combustibledustposter.pdf

Sulhur dust explosion

At 2:15 a.m. on September 17, 2019, an employee was emptying a supersack of sulfur into a bin at a tire manufacturing facility. The sulfur in the bin ignited and caused an explosion, causing the bin door to be blown open. The employee incurred burns to his face and arms from the explosion and torn ligaments in his legs as a result of the bin door striking him. The employee was hospitalized. 

 Source:OSHA.Gov

Thermal expansion of DMS caused incident

At 11:30 a.m. on June 20, 2007, Employees #1, #2, #3, and #4, who worked for Scaffolding Company, and Employees #5, and #6, who worked for Plant Services Company, and Employees #7 and #8, who worked for a chemical manufacturer, were hospitalized after being exposed to dimethyl sulfate (DMS) in the ethoxylation area where it was used in reactors 4 and 5. 

Employee #7 was an operator who moved bags containing chemicals into the area in order to add it to reactor 4. Employee #8 was a mechanic that worked unplugging an auger at reactor 4. Employees #7 and #8 started working at 7 a.m. at reactor 4. 

Employees #1, #2, #3, and #4 dismantled a scaffold at a platform at the reactors. 

 Employees #5 and #6 removed and installed new insulation on piping at a platform at the reactors. The host employer did not become aware that employees were exposed to DMS until about 2 p.m., when workers were discovered having chemical burns. Employees worked on a raised platform around the two reactors. In order to enter and leave the area, they walked along a path between two the reactors that was only 30 inches wide, and a pipe that contained DMS which ran overhead between the reactors. The piping system normally operated at 5 psi, but thermal expansion of DMS caused pressures over 300 psi and caused a valve on the overhead pipe to leak this extremely hazardous compound down onto employees that worked beneath the pipe. 

Source:OSHA.Gov

Turbine exhausts are HOT!

 On April 5, 2012, Employee #1 was handling an exhaust leak from a turbine on the site of a power plant. The task involved the placement of a piece of insulation blanket over the pipe expansion bellow system, which contained the exhaust leak. The leak was of hot air, which was approximately 600 to 700 degree F. It was emanating from a section of pipeline located on the exhaust waste heat recovery system. While Employee #1 was dealing with the leak, he inhaled the hot air exhaust and injured his lungs. He was transported to a medical center. At the medical center, Employee #1 underwent treatment and was hospitalized. 

 

Source:OSHA.Gov

Asphyxiation incident during installation of a PSV

 At 11:30 a.m. on October 15, 2021, Employees #1 and #2, both maintenance employees, were assigned to install a pressure safety valve (PSV) on a flare header in a methylene diphenyl diisocyanate (MDI) unit when they were exposed to nitrogen and carbon monoxide. The installation procedure requires supplied air respirators. The employees were staging equipment on the platform area in the MDI unit to remove the PSV. Employee #2 decided to go down to the lower level to obtain both employees a supplied air respirators before starting the work. Employee #2 looked back and saw Employee #1 slumped over on the platform. Employee #1 was overcome with the gases and loss consciousness. Employee #2, in an attempt to revive Employee #1 also loss consciousness. The employees were discovered by coworkers and emergency services were notified. First responders removed both employees from the platform but Employee #1 died from his exposure.

Source:OSHA.gov

Are you discussing domino effects in your HAZOP?

At approximately 5:50 p.m. on March 25, 1988, the leacher autoclave (#2) in building #1, which had been in service for about three weeks, reached a temperature of about 490 degrees Fahrenheit and a pressure of 400 psi. At this point the single locking (locating) pin sheared (the second pin was missing) allowing the cover to rotate against the locking ring, which was not fully engaged. The cover was released with explosive force, tearing a large hole in the roof and rupturing a 2 in. high-pressure gas line. As the head fell, a second hole was made in the roof about 25 yards northwest of the original location. Approximately 120 gallons of 28 percent sodium hydroxide solution was instantly vaporized into a cloud of caustic fumes that drifted over the area, causing eye, lung, and throat irritation to approximately 25 people, including the police who responded to the emergency. Employees #1 through #12 required medical attention. The gas line was promptly shut off by plant maintenance personnel who responded to the explosion. This action prevented further serious fire and explosion damage and possible loss of life.

Source: OSHA.gov

HAPPY NEW YEAR!