Wayne Geyer looks at the variety of causes in tank fires and explosions, and the importance of awareness
Explosions and fires in the petrochemical industry capture headline news locally, nationally, and globally depending on the severity and location. Best practices with safety in operations and management are essential to avoid injury and death.
Unfortunately, far too many incidents continue to take place. The wide information available today via the internet makes it seem that explosions and fires are becoming more frequent. Whereas before the turn of the century, most incidents captured by headline news were contained to national incidents. A recent review through the internet revealed a surprising number of incidents globally, many of which would have never been heard about twenty years ago.
Many petrochemical products are rated as either flammable or combustible. For example, gasoline and ethanol are classified as flammable liquids by the fire safety codes. Diesel, heating oil, and kerosene are considered combustible liquids. Flash points, or the temperature at which their vapours will ignite, determine their rating. The lower the flash point, the more flammable and dangerous the liquid and its vapours become.
The Steel Tank Institute (STI) used to produce a monthly newsletter entitled Tank Mishaps. STI did not always have the details behind what caused the fire or the explosion, only the news story that was published. With every issue, STI would print this little explanatory introduction:
‘By learning about the misfortunes of others, it is STI’s hope to educate the public by creating a greater awareness of the hazards with storage and use of petroleum and chemicals. Please refer to the many industry standards and to the fire and building codes for further guidance on the safe operating practices with hazardous liquids.’
This article will be no different. By writing about incidents that have taken place recently, the hope is that the reader obtains a greater awareness of the hazards of the petrochemical industry. Safety moments, safety procedures, safety clothing, safety rules, etc. do not simply exist because a safety manager says so. The consequences of a fire or explosion from improper handling or storage of flammable and combustible liquids is too great – with huge property losses, business devaluation, disruption in supply, and the greatest of unfortunate consequences – injury and death.
NUSTAR IN CALIFORNIA
In 2019, before the COVID-19 pandemic, a very significant explosion occurred in Crockett, California, US. NuStar Energy owned a tank farm that included two ethanol storage tanks, each with a capacity of 250,000 gallons (946,353 L). A huge explosion occurred at one of these tanks, so great, that the top of the tank lifted off and landed upon an adjacent ethanol tank, causing it to explode also (Figures 1 and 2).
The fire could be seen over a great distance, and the explosion scared many people from the local population who lived near the NuStar facility, some thinking there was a seismic event.
Several stories came out after the event, such as allegations that the tanks were built without the local authority’s inspection or permit, structural deficiencies, and damaged valves had not been replaced. But the reports given much later stated that either static electricity, or a spark inside the tank vapour space, coupled with the flammable vapours given off by the ethanol and oxygen intrusion through the vent opening, set off the fireball, with the spark possibly caused by inadequate grounding with equipment used in the storage operation.
Fortunately, no one was killed. Over
1.5 million gallons of fire-fighting foam and water mixture were used to contain and extinguish the fire. The two tanks completely collapsed. Words don’t adequately describe the massive fireball that can be seen in videos of the incident. The video of the tank roof flying through the air is available at https://youtu.be/AN4MfaWJRGo.
THE DANGERS OF
TORCHES AND WELDING
On 19 May 2020, a crew was performing maintenance in a tank farm on Pelican Island in Galveston, Texas, US, near a branch campus of Texas A&M. There was a welding operation occurring near a
2 million gallon crude oil tank. According to a law firm with an interest in such incidents, ‘there was an explosion and fire enveloped the area.’
Two of the welding crew were injured and hospitalised. Fire fighters applied foam to extinguish the flames. The footage is available at https://youtu.be/mIE39dK8djY. I found it to be of interest that another fire occurred at a crude oil tank farm on Pelican Island in 2012.
Many from the industry do not view asphalt tanks as being flammable, but a fire in Ennis, Texas in 2018 suggests that due care and following best safety practices are required with asphalt operations also. A five-person contractor crew was hired to retire a damaged asphalt tank. The damaged tank shared a catwalk with another tank.
The crew started using a cutting torch on the catwalk, resulting in a tank explosion. Inside Climate News was quoted to say that over a dozen asphalt and #6 bunker oil tanks exploded.
Many industry participants view asphalt as relatively benign. But hydrogen sulphide gas can form when certain hydrocarbons are heated to high temperatures, with production of asphalt being one such application. A rule of thumb is that 1 ppm of hydrogen sulphide in the liquid phase of asphalt correlates to 400 ppm in the vapour phase. Some asphalts can produce over 30,000 ppm in the vapour phase in a confined space such as a storage tank. Safety regulations limit hydrogen sulphide exposure to workers to less than 10 ppm, with the potential of death at 700 ppm. Hydrogen sulphide is also flammable, as well as various chemical additives.
Both the Pelican Island crude oil tank incident and the Ennis asphalt tank involved welding or cutting torch operations near storage tanks in operation. Regardless of the petrochemical in storage, at terminal operations, all work involving flames must be first tested for flammable vapours in the atmosphere where the work is to be done.
In the past few years, there were also some significant explosions at refineries. In Indonesia, on 29 March 2021, a lightning strike caused an explosion and a resultant tank fire that spread to other tanks at a refinery owned by state oil company Pertamina. 1,000 people had to be evacuated. Five people were seriously injured, fifteen were reported to have slight injuries, and one death resulted from a heart attack.
On 26 April 2018, the Husky Energy Refinery in Superior, Wisconsin, US, experienced a major explosion. Workers shut down a fluid catalytic cracker (FCC) to allow periodic inspection and maintenance work. The FCC uses heat and a solid catalyst to break down, or crack, heavy hydrocarbons into smaller hydrocarbons, which can then be blended into gasoline. Slide valves control the catalyst between the reactor, with hydrocarbons, and the generator, which has air. To avoid the air to get mixed with the hydrocarbons and prevent explosion, the slide valves maintain a catalyst level between the reactor and the generator, which acts as a barrier.
To initiate the shutdown of the FCC unit, the workers closed the two slide valves. But unbeknownst to the workers, a valve stem was eroded and could not hold and maintain the catalyst as a barrier. This allowed the catalyst to flow through to the generator. Further, this allowed air from the generator to flow backwards through the valves to the reactor. The air continued to flow backwards until it reached equipment downstream of the reactor containing flammable vapours.
At this point, the air and flammable vapours mixed, and a large explosion resulted. Debris was hurled everywhere. One large piece travelled 200’ (61 m) and pierced a large hot asphalt storage tank. This allowed the asphalt to escape the tank. The asphalt travelled over a containment berm and caught fire. The fire travelled along the pooled asphalt surrounding the crude oil storage and the FCC. People were evacuated as far as 5 miles (8 km) from the refinery, and 36 Husky employees and contract workers sought medical treatment. Asphalt tank fires are difficult to extinguish, but the local fire emergency responders were able to extinguish the fire in a matter of hours, instead of days. A great animation of this incident was produced by the US Chemical Safety Board at https://www.youtube.com/watch?v=3RFDKpwdbEA.
SMALL TANK EXPLOSIONS
Thus far, the incidents described in this article took place on large field erected storage tanks. But small shop-fabricated storage tanks incidents prove that explosions, death, and injury are not just limited to tanks storing millions of gallons of petrochemicals.
A couple of large explosions took place at petroleum service stations where the public fills their vehicle with petrol. Information was almost non-existent with a couple of these events, but the videos of the incidents are worth a million words. If these explosions do not cause industry workers to respect and fear the dangers of petroleum, nothing will.
An underground tank exploded in Madinah, Saudi Arabia in 2019. Customers filling their cars with fuel can be seen to drop the nozzles and run away as fast they could. Others got into their cars and drove away as fast as they could. With 35 years in the business, I have never seen an underground tank explosion like this incident! The footage is available at https://youtu.be/Bgv_E6dGUZQ.
A large fuel station explosion was reported in Bayda, Yemen on January 30, 2021, resulting in two deaths, 90 wounded, and 20 critically wounded, with many cars and homes destroyed. Another explosion in Novosibirsk, Russia occurred while a fuel tanker was unloading its contents.
Flammable liquid tanks in confined spaces, such as in vaults, provide some of the most hazardous conditions of all. Two explosions in vaults at service stations in Virginia and Pennsylvania resulted in numerous fatalities recently. In one situation, an employee tried to remove accumulated groundwater that seeped into the concrete vault while flammable vapours (and perhaps liquids) were present, using a non-hazardous rated shop-vacuum and a common workshop electrical extension cord, and also without the use of liquid or vapour sensors to establish the hazards – while a truckload of fuel had been just delivered.
SLAMMING THE MESSAGE HOME
The national fire codes have very demanding requirements for fuel tanks in concrete vaults due to the potential for spills and flammable vapours becoming contained in a vault, and creating an explosive environment, especially if an ignition source becomes present.
I have served on committee of the NFPA 30 Code for 35 years. This is the National Fire Protection Association’s (NFPA) Code on Flammable and Combustible Liquid Storage, adopted by many jurisdictions and authorities by regulation, to assure safety during storage, transport, handling, and operation of these dangerous liquids. The committee is composed of experts from the petrochemical industry with experience in storage and operations, insurance companies, national testing laboratories, regulators, safety organisations, and petroleum equipment. The NFPA 30 Code was first published in 1906, and it is reviewed and normally updated every three years. In the US, OSHA created and oversees regulation of flammable and combustible liquids. Other countries have similar organisations as NFPA, such as the Association For Petroleum & Explosives (APEA) in the UK, and regulatory bodies.
Flammable and combustible liquids entail significant built-in energy by their chemistry. When the right mixture of flammable vapour and oxygen combine in conjunction with a flame source, KABOOM, explosions and fire can result. I hope you, as the reader of this article, already know of the hazards, but maybe this article slams one important message that you will not forget. Explosions at petrochemical facilities create tremendous damage, and injury or death.
It is imperative that workers at petrochemical facilities respect the dangers that exist with flammable and combustible liquids and vapours, especially work involving a flame source and the presence of oxygen. Welders and acetylene torch users must use care and always check for flammable and combustible atmospheres before beginning work.
Train workers, no matter how insignificant the task may be while in the presence of hazards. Monitor the air for dangerous vapours. Get special permits in confined space or when performing work near flammable and combustible liquid storage or operations. Follow important codes and regulations. Share the videos to help workers understand the hazards. It could save a life some day!
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Wayne Geyer is a professional engineer who has served on the NFPA 30 Flammable and Combustible Liquids Code since 1986, and was the executive vice-president of the Steel Tank Institute for over 30 years. He gave a talk on this subject at the NISTM Aboveground Storage Tank Conference and Trade Show held from 31 August–2 September 2021 in Florida, US.