“Never underestimate the power of a fresh coat of white paint.” — Jeremiah Brent
Shortly after midnight on Thursday, April 8, there was a fire and explosion at the OPC Polymers unit of the Yenkin-Majestic Paint facility in Columbus, Ohio. One employee died, five employees were hospitalized, and four others were also injured.
“But it’s just paint. Can paint explode?” What happened in Columbus is being investigated by the CSB and OSHA, so I’m not going to speculate about the causes of that specific catastrophe.
But It’s Just Paint
Paint is so familiar to most of us, we forget its hazards and the hazards associated with manufacturing it. The hazards of a gallon pail of paint sitting in the garage are quite different from the hazards associated producing a 20,000-pound batch.
Paint consists of four types of ingredients, each with their own hazards. The main ingredient is the solvent. Then there are the ingredients that remain in the paint film after the paint dries: pigments, additives, and binders.
Increasingly, we use latex paints because they have low VOCs and because they clean up with soap and water. The solvent in latex paints is primarily water, not a particularly hazardous substance. The other main category of paints is known as “oil-based”, and they use organic solvents. Not surprisingly, organic solvents are flammable liquids, with their associated hazards: flammability and often, toxicity, either when ingested or inhaled.
In a manufacturing environment, where the quantities are much greater than what is found in a garage, it is important to control these hazards. Among other things, that means complying with the requirements of OSHA standards like the Flammable Liquids Standard, 29 CFR 1910.106; the Process Safety Management Standard, 1910.119; and the Hazardous (Classified) Locations Standard, 1910.307; as well as with the PPE requirements in 1910 Subpart I.
Pigments are the reason for paint. They are powders that, when suspended in paint, give it the ability to hide and color. Most pigments and pigment extenders are inorganic solids. They include titanium dioxide, clay, silica, diatomaceous earth, calcium carbonate, talc, and zinc oxide. Most are respirable dusts, and so pose a health hazard, but they are not combustible dusts, so don’t pose a dust explosion hazard.
There are some organic pigments, however. As with inorganic pigments, they are respirable dusts. Generally, though, they are also combustible dusts. Their combustible hazard doesn’t exist once they’ve been mixed into the paint. But the process of producing them, and of adding them to paint, has the potential to create dust clouds that can be very destructive when they ignite and explode.
Paint additives improve the performance of paint. They include biocides, surfactants, and defoamers, all of which have their own hazards. Paint manufacturers typically don’t make their own additives but purchase them to use in the paint formulation process. Obviously, paint manufacturers must be aware of those hazards and follow the recommendations of the additive suppliers.
Modern paints use polymer resins as binders. Latex paints use acrylic polymers as binders. Oil-based paints typically use alkyd resins as binders. The polymer resins themselves are relatively benign (although oil-based binders are dissolved in organic solvents). The manufacture of these polymers, on the other hand, is perhaps the most hazardous operation in paint production.
Acrylic polymers are produced from acrylic monomers like acrylic acid, acrylates, methacrylates, and acrylonitrile, and other monomers like styrene. These monomers are toxic (the OSHA permissible exposure limit for acrylonitrile is 2 ppm) and extremely reactive. By “extremely reactive”, I mean that the potential for runaway reaction and resulting explosion is a major concern for acrylic resin production.
Alkyd resins are a different kind of polymer. They are made by the condensation polymerization of dicarboxylic acids or anhydrides with polyols, i.e., fatty acids or monogylcerides. The reaction is called a “condensation polymerization” because the act of linking two molecules together also generates a small by-product molecule. In the case of alkyd resins, the linking reaction produces water. Unlike the acrylic reaction, the alkyd reaction is pretty reluctant, meaning that the reaction has to be heated to proceed at a reasonable rate. The water that forms during the reaction must be removed in order for the alkyd resin to be usable. There is a process where xylene is used to form an azeotrope with water, allowing it to be removed from the reaction kettle. So, while the main reactants—fatty acids and anhydrides—are not especially hazardous, the azeotropic distillation with xylene gives the process a chance to produce a flammable vapor.
The Alkyd Resin Process at the OPC Polymers Unit
To date, the CSB has posted two updates on their investigation of the fire and explosion at the OPC Polymers Unit in the Yenkin-Majestic Paint facility, one on April 9, the day after the explosion, and one on April 13. The first mentioned the manufacture and marketing of both acrylics and alkyds, as well as other materials. It also mentioned storage of two anhydrides (maleic anhydride and phthalic anhydride), xylene, and mineral spirits—all components of alkyd resin manufacture.
The second update from the CSB confirmed that the OPC Polymers unit was an alkyd resin manufacturing process. Security video shows that at 12:02 am EDT (system time), there was a loss of containment. Two minutes later, at 12:04 am EDT (system time), the video system stopped recording, presumably coinciding with an explosion.
It could be that there was a release of a flammable vapor cloud that found an ignition source. Or not. It is easy to speculate from hundreds of miles away. I’m waiting for updates from the CSB. What we know for certain is that someone died, and others were injured and hospitalized.
Protect Your Investment
No one at Yenkin-Majestic was planning for a fatal explosion early on April 8. No one is planning for a fatal explosion at your facility. But they happen. Let’s not just wait for the CSB report but take another look at our own processes. Where could a failure result in a catastrophic event—a fire, an explosion, a toxic release? Have we deferred maintenance in the hope that we can get through this, whatever “this” is? It’s time to redouble our efforts. Let’s protect the investment in our facilities and in our people.