Improving safety in confined space entry still is a pressing priority for the National Tank Truck Carriers (NTTC) and its Tank Wash Council.
One death is too many, and the tank cleaning industry suffered three in 2020.
“It could happen to any of us at any time, so we spend a lot of time on this subject for a reason,” said Terry Kolacki, NTTC Safety and Security Council national chairman. “Any time somebody’s going in a tank, or a confined space, there may be a hazardous atmosphere. We have the testing equipment available for employees to use, but sometimes they choose not to use this equipment, and a lot of times it ends up with another person diving in to try to help them, and you end up with two fatalities.
“This is something that hits the industry hard, and it’s something we’re all susceptible to, so please make sure your people are using meters, they know how to use them, they’re instructed on them, you train on them, and you audit your policies and procedures at each location to make sure that they’re using these every day.”
Confined space entry best practices was one of three topics planned for the in-person meeting of the Tank Wash Council, originally slated for June 16-18 in Biloxi, Mississippi, as part of the Safety & Security Council Annual Meeting, along with safely cleaning flammables out of tank trailers, and vapor abatement and management.
Instead, A-One Chemicals’ Ed Wickham, the tank cleaning council chair, vice chairs Angela Castle (KAW Services) and Ken Shafer (Superior Bulk Logistics), and sub-committee chairs Ken Cooper (National Tank Services) and Donny Hearn (WCM) touched on the critical topics during NTTC’s virtual Tank Truck Week 2020.
“These three segments are designed to give you an idea of what the full programs on these topics will look like at our June 2021 Safety & Security Council meeting, that we hope we’re able to hold,” Wickham said.
Confined space entry
A confined space in tank cleaning is defined as a space that is large enough to work inside but has a restricted means of entry and isn’t designed for continuous occupancy.
Proactive measures to eliminate hazards in confined space entry include only entering containers after they’ve gone through the complete cleaning process, including drying with a blower; following company confined space entry procedures and not entering a space if it fails atmosphere monitoring; and using a properly bump tested and calibrated atmosphere monitoring meter.
Proactive measures to enable rescue without entry include requiring all workers entering the space to wear a body harness that is not expired and in good working condition, and ensuring all workers entering the space have a cable/lifeline that connects their body harness to a retrieval system/rescue winch.
Digital inspection equipment like video cameras allow technicians to inspect tank interiors without going inside. This type of equipment also allows for documentation of the condition of the container at the time of cleaning, providing additional transparency for customers. In food grade cleaning, using video inspection tools also prevents human contamination of the container after it has been cleaned and decontaminated.
“This is a prime example of how we can use technology to eliminate confined space entry and keep our people safe,” Cooper said.
The most common cause of injury and death in confined space entry is an oxygen deficient atmosphere. Any atmosphere with less than 19% oxygen decreases a person’s ability to function, and an atmosphere with less than 4% oxygen can cause death in only four minutes of exposure. The most common gases causing injury and death in confined space entry are hydrogen sulfide, carbon monoxide and nitrogen, Wickham said.
The council is working a national confined space entry awareness campaign, Wickham concluded, with posters in key areas reminding tank wash employees of the hazards they face daily and including phrases like “Make it a safe confined space entry,” “Grab a meter and a buddy” and “Make sure everyone goes home safe every day.”
Kolacki said tank wash leaders must reinforce those messages daily.
“Let them know we’re concerned about their safety,” he said. “Make sure your looking over their shoulder to see they’re using the meters, they’re calibrated, and let them know you’re watching them and that you care about them. That sends a great message to your workplace that people care about you and want you to do the right thing.”
When addressing safe cleaning of flammables, tank washes primarily are concerned about hazards involving fires, explosions an inhalation.
Eliminating these hazards includes controlling vapors, keeping ignition sources in safe locations, controlling static discharge and eliminating lower explosive limit (LEL) atmospheres in a container as safely and quickly as possible.
A fire requires oxygen, fuel and an ignition source, so subtracting any one component eliminates the risk of fire or explosion.
Typical ignition sources at a tank cleaning facility include:
- Static electricity caused by improper grounding
- Gas fired steam boilers, hot water pressure washers and heaters
- Electrical motors, switches or actuators
- Exposed electrical connections
- Tools that create sparks, or grinding
The most common fuel sources at a tank cleaning facility include:
- Flammable vapor that arrives in the container, sometimes placarded, but sometimes not if placards are removed
- Residual liquids in containers causing vapors
- Flammable gasses contained in pressurized containers
“Most tank wash fires or explosions happen during the initial stage of cleaning,” Cooper said. “This is the removal of the retain or heel from the trailer. Once the unit is opened to collect retain or heel, vapors pour out along the ground or into the air until they’re dissipated or ignited by an ignition source.”
To eliminate hazards at washes that do a lot of flammable cleans, like gasoline or ethanol tanks, use a designated area away from ignition sources as the retain/degas area; always have good grounding and bonding points, with cables attached to the trailer; use a properly bonded steel or stainless steel pail to catch retain or heel; and verify LELs are below the threshold to safely bring a trailer into the wash or maintenance bay.
Special considerations often are needed in older facilities to keep trailers away from ignition sources. And atmospheric monitoring instruments should be utilized to properly verify a safe LEL atmosphere has been established in the container before an employee attempts a confined space entry. “A great rule of thumb is to always have a zero LEL,” Cooper said. “That is considered the safest and best practice, so make sure your tank is degassed or cleaned until there is 0% LEL, before you role it into a maintenance bay.”
Some trailer styles, mainly MC 306 and DOT 406 cargo tanks, contain voids between the bulkheads that also must be checked, emptied, steamed out and left open as part of the cleaning process, Wickham cautioned. These tanks can have clean compartments and lines but still have voids holding dangerous liquids or vapors.
The U.S. Environmental Protection Agency (EPA) historically hasn’t considered tank truck cleaning facilities to be a significant source of emissions, specifically volatile organic compounds (VOCs), so most permitting or control requirements are state-specific, Hearn said. These requirements, in places like Texas and California, typically arise from local air quality issues, and range from simple registration of operations to more elaborate command or control requirements, including monitoring or record-keeping.
Regarding air permits, and permitting requirements for controlling vapors at tank washes, individual states often use different methodologies to determine emission levels, and their potential impacts. While the EPA still references its 1978 assessment, “Source Assessment: Rail Tank Car, Tank Truck and Drum Cleaning, State of the Art,” Texas, for example, bases its emissions estimation methodology on the Ideal Gas Law.
The Texas Commission on Environmental Quality (TCEQ) then establishes the state’s control measures in ozone non-attainment areas, like in Houston and Beaumont, based on the Ideal Gas Law equation, PV=nRT, which provides an approximation of the behavior of many types of gases under many different conditions.
So, for instance, while the EPA estimates the annual cleaning of highly volatile acetone produces .686 pounds of emissions per truck, TCEQ says acetone cleaning produces 96.72 pounds per truck, when cleaning 10,000 trucks per year.
“Not knowing which one is correct, I’d say it’s somewhere in the middle,” Hearn said. “It’s probably closer to EPA than TCEQ, but we don’t get a vote. We’re just following normal protocol when it comes to estimating emissions.”
Typical emissions control includes a vapor collection system that utilizes a flare, thermal oxidizer or carbon absorption. A “simple” system consists of piping that removes liquids and routes vapors from a tank container to a combustible device, like a flare or thermal oxidizer, to prevent flames from reaching the tank.
The most common setup is a flare system that uses natural gas or propane to create a combustible mix at the flare tip. Thermal oxidizers are more complicated and require precise temperature controls in the chamber where gasses are combusted. So they’re highly efficient at reducing emissions, but also very temperamental, Hearn said, which can complicate operations for facilities that simultaneously clean multiple products.
A carbon absorption system is a simpler method utilizing canisters piped in series.
Thermal oxidizers deliver the best destruction rate, followed closely by flares and then carbon absorption. Flares and carbon absorption don’t require stack testing for air permits but come with monitoring requirements ranging from simple to complex, Hearn said, and record-keeping, while burdensome, is critical.
Authorization ranges from simple registration to full-blown air permitting that in some cases necessitates dispersion modeling. Other requirements include visual observations and specific types of monitoring for each control method.
Regarding design considerations for tank wash facilities, flares require relatively little capital investment and maintenance, and operating cost is a function of how much natural gas is used; thermal oxidizers have a higher initial capital cost, and a higher maintenance cost than flares, but boast a lower operating cost; and carbon absorption systems are less expensive to establish but costlier to maintain due to issues with VOC monitoring equipment and canister replacement.
When deciding which way to go, companies should consider which system best suits their product mix. For example, carbon systems aren’t as effective with high-polarity and high-volatility products, or oxygen-bearing compounds.
“Thermal oxidizers have a narrow operating range, so it can be troublesome trying to manage that when you have multiple bays and you’re trying to clean multiple things simultaneously, whereas flares are assemble, fire and forget, as long as they’re well-maintained,” Hearn concluded.