Incompatible Chemicals: Explosion at AB Specialty Silicones

Voiceover: May 3, 2019, the AB Specialty Silicones facility in Waukegan, Illinois. During production of an emulsion product, two incompatible chemicals were mixed. The chemicals reacted and produced flammable hydrogen gas that ignited, causing a massive explosion that killed four workers and destroyed the company's production building.

Lemos: The explosion at AB Specialty is one of many reactive chemistry incidents investigated by the CSB during the agency's history. Reactive chemicals can lead to major explosions, fires or toxic emissions that can cause death, injury, property damage and negative effects in the environment. Chemical reactivity hazards can be more difficult to anticipate and recognize than other types of process hazards.

Inadequate recognition and evaluation of reactive chemical hazards has been a causal factor in a significant number of the reactive chemical incidents with known causes. And yet companies are often not required by regulation to implement the most basic safety management system elements to control these hazards. For these reasons, serious incidents like the one at AB Specialty continue to occur.

Voiceover: AB Specialty Silicones manufactures silicone products used in a wide variety of applications from personal care to roof coatings for distribution worldwide. One of those products is an emulsion commercially sold as Andisil EM 652, which is used as a waterproofing agent. AB Specialty manufactured EM 652 using a batch process.

It was produced in a part of the facility known as the Low Bay Emulsions Area. On May 2, first shift operators started the process to manufacture the first of two back to back batches of EM 652. They obtained a form called a batch ticket which detailed the operation steps.

For the first batch, the operators staged the chemical ingredients used to make EM 652, including the polymer known as Andisil XL-10. The operators then followed the steps outlined in the batch ticket to manually add and mix the chemical ingredients in a tank inside the production building. The operators then delivered two sequential product samples to AB Specialty's Quality Control department.

The QC department found the Ph in both samples of the first batch to be too low and in both cases required the operators to increase the Ph of the batch by adding a solution of 10% potassium hydroxide in water. The operators brought drums of the 10% potassium hydroxide into the emulsions area and added the necessary amount to the first batch of EM 652 product. A third sample delivered to the QC department revealed that the Ph was correctly adjusted, and the first batch of EM 652 was approved for packaging.

Sometime before 8:00 p. m. on May 3 a second shift operator likely obtained the batch ticket with instructions for how to produce the second batch of EM 652.

This batch required the use of eight drums of XL-10. There were also likely two or three drums containing 10% potassium hydroxide remaining in the emulsions area. As a result, they were up to 11 nearly identical drums containing both XL-10 and 10% potassium hydroxide in the production area.

The operator added the first two ingredients to the batch tank which included XL-10. But at some point while completing the initial steps, the operator likely misidentified the 10% potassium hydroxide drums that remained in the area for XL-10 and incorrectly added potassium hydroxide to the tank. Potassium hydroxide is highly reactive with chemicals that contain silicon hydride bonds such as XL-10.

The reaction of these chemicals rapidly produces flammable hydrogen gas. Shortly after the chemicals were mixed, the contents of the tank started to foam and overflow onto the floor. The operator began to yell and several additional workers ran to the emulsions area in response.

A fog also formed which spread through the low bay. The workers did not realize the material released during the upset was hazardous and there were not functioning gas detectors to warn them to the dangers of the hydrogen gas. The workers did not evacuate the building.

Two operators were directed to ventilate the building, but before they could take effective action at about 9:35 p. m. the hydrogen gas ignited, causing an enormous explosion and fire.

Four AB Specialty workers lost their lives and another was injured. The manufacturing building was completely destroyed. Following the incident, the Chemical Safety Board launched an investigation and found that a number of safety issues led to the fatal explosion.

One such safety issue was the AB Specialty did not have a written procedure requiring employees to separate 10% potassium hydroxide drums from XL-10 drums in the emulsions area or to remove leftover containers after use. This plus the fact that the two incompatible chemicals were stored in nearly identical blue drums made mixing of the two materials all too possible. Vincent: In processes that rely on operators to gather and mix chemicals, it is critical that companies reduce the risk of human error by making it easy to do the job right and hard to do the job wrong.

In this case that could have been as simple as having written procedures that specify storing incompatible chemicals in separate areas and in different colored containers. Voiceover: The CSB also found that the design of the batch equipment and ventilation system likely led to the severity of the incident. The emulsion process tank had an open hatch type lid and no vent pipe to direct gases to a safe location.

As a result, the hydrogen gas produced during the incident released directly into the production building where workers were located. And the production building's ventilation system included an air mover which was designed to introduce outside air to the building and was positioned near the location where EM 652 was being manufactured. This may have helped distribute the hydrogen within the production building where it mixed with air, creating a large and explosive gas cloud.

Vincent: An alternative ventilation design could include local exhaust ventilation where building air discharge fans and vents are located in the process area. This design could have vented hazardous gases to a safe location and reduced the severity of the explosion. Voiceover: The CSB learned that during the incident workers knew that a process upset had occurred, but they did not recognize the hazard of flammable hydrogen gas.

Hydrogen is a colorless and odorless gas, indistinguishable from air without the use of additional technology such as gas detectors. But the CSB found that the production building did not have a hydrogen gas or flammable gas detection and alarm system. Such a system could have automatically activated an alarm to alert workers to the danger they were facing, making it less likely they would've remained inside the production building between the start of the hydrogen release and the time of ignition.

And the CSB found that the workers lacked effective emergency preparedness training to recognize the potential for a hydrogen gas release and know to immediately evacuate if a possible release should occur. Vincent: The CSB encourages companies to work with gas detector manufacturers to help ensure the correct sensor technology is selected for their operations. Once selected the system must be properly installed and adequately maintained.

Workers must have the right resources such as robust procedures, effective technology and training to recognize the signs of an adverse reaction and respond appropriately. Voiceover: To that end the CSB recommended that AB Specialty Silicones develop hazardous gas detection and alarm programs and associated procedures. These should be based on manufacturer specifications, current codes, standards and industry good practice guidance.

The programs and procedures should be developed for all hazardous gases that could be released near workers, including hydrogen, and must address proper installation, calibration, inspection, maintenance, training and routine operations. The CSB determined that many of the safety issues that led to the explosion at AB Specialty could have been identified if the company had an effective hazard analysis program. Instead AB Specialty assessed its manufacturing operations through a program it called Technical Service Requests, which evaluated a mix of business and safety risks.

The process did not and was never intended to assess the hazards of performing an operation or to establish safeguards to reduce risk. At the same facility in 2014, a drum containing EM 652 exploded as an operator inserted a charging wand into the drum. The operator sustained short-term hearing loss from the explosion.

After AB Specialty concluded that a lack of comprehensive hazard analysis among other things contributed to the incident. But despite knowing their hazard analysis program was inadequate, AB Specialty did not make needed improvements after the 2014 incident such as requiring systematic reviews of process hazards. This points to a weak process safety culture at AB Specialty that did not promote effective safety management systems.

Had AB Specialty instituted a safety management system that addressed process safety including a robust hazard analysis program, the company could have identified the serious safety hazards associated with its manufacturing operations, including storing reactive chemicals in similar containers, the practice of allowing incompatible materials to be stored near each other, the problematic ventilation system and batch tank design, the lack of a gas detection system, and its insufficient emergency preparedness. Vincent: Effective safety management systems that address process safety are critical for companies that handle reactive chemicals and to prevent future reactive incidents. AB Specialty did not have a process safety management program in place at the time of the incident.

Voiceover: Although AB Specialty processed chemical is capable of undergoing highly hazardous chemical reactions, those chemicals are not listed for coverage in either OSHA's Process Safety Management Standard or the EPA's Risk Management Plan Rule. Therefore, AB Specialty was not required to implement baseline process safety management system elements that are required under these regulations, including performing an effective process hazard analysis. In response the CSB reiterated a previous recommendation to OSHA to amend the Process Safety Management Standard to achieve more comprehensive control of reactive hazards that could have catastrophic consequences and to augment the process hazard analysis element of the standard to explicitly require an evaluation of reactive hazards.

The CSB also reiterated a recommendation to the EPA to revise the Accidental Release Prevention Requirements to explicitly cover catastrophic reactive hazards that have the potential to seriously impact the public, including those resulting from self-reactive chemicals and combinations of chemicals and process specific conditions. Lemos: When chemical reactivity hazards are identified, it is critical for companies to understand if the hazards can be eliminated or reduced. If not, these hazards must be managed throughout the operational lifetime of the facility and products to protect workers, property and the environment.

It is past time for regulators to fully recognize the hazards presented by reactive chemicals. We call on OSHA and EPA to update their regulatory standards to include better coverage of reactive chemicals. Closing the regulatory gap will prevent further tragic incidents and save lives.

Together we can impact safety for our chemical industries, our workers, our community and our environment. Thank you for watching the CSB safety video. Voiceover: For more information, visit CSB.

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