By John Davis
Safe handling of liquid asphalt by terminal workers and tanker-truck drivers is extremely important because liquid asphalt is stored and transported at high temperatures.
Asphalt binder, if heated to a high enough temperature, releases fumes that flash in the presence of a spark or open flame. The temperature at which this occurs is called the flash point, and it is well above the temperature normally used in paving operations. To be certain of an adequate margin of safety, the flash point of the asphalt is measured and controlled. As an added precaution, sources of ignition, such as electrical sparks, open flames, or lighted cigarettes, should be prohibited or strictly controlled.
Asphalt foaming can be another concern. Asphalt is normally free of water or moisture as it leaves the refinery. However, trucks may have moisture in their tanks. If any water is present, it will become steam when the hot asphalt is added to the tank, and the steam will cause the asphalt to foam.
The basic source of information about accidental fire and explosion is the Material Safety Data Sheet (MSDS). Each terminal employee or driver who works with asphalt should receive a MSDS. It should include specific information on the components present in the asphalt. It should list all pertinent information including flashpoint, boiling point, acute and chronic effects of all chemical ingredients, recommended personal protective equipment (PPE), and fire and emergency cleanup information.
OSHA requires that the employer of the terminal worker or tanker-truck driver determine if hazards are present and if they necessitate the use of PPE. If hazards are present, or likely to be present, the employer must select appropriate PPE and have the workers use that equipment for specific hazards.
This equipment includes a hardhat, safety goggles or safety glasses, face shield, long-sleeved shirt buttoned at the collar and cuffs, heat resistant gloves, long pants without cuffs, and sturdy high-top and steel-toed leather work boots.
At the Terminal
Working at an asphalt terminal, driving a tanker-truck full of hot asphalt, or unloading at a storage facility can present many challenges and hazards. A driver should know what material was previously hauled in his tanker-truck. Contamination can cause a violent eruption and result in serious injuries and property damage. Additionally, cleaning up a mishap at the loading rack can delay the crucial delivery of asphalt. A truck in poor operating condition increases the risk of accident and injury.
Drivers should read the truck’s manifest for information about the previous load. Check the hatch cover for condensation; this is a warning that there is water inside the tank. There should be no contamination from residues and solvents. If contaminants come in contact with a new load of asphalt, they can cause a flash fire inside the tank.
At the terminal, make sure the tanker is loaded from the right loading rack. Take the proper precautions to make sure no one accidentally drives off in the truck while loading. Lock the brakes, turn off the engine, pocket the keys and chock the wheels.
While loading the tanker, stand clear of the hatch and stay upwind to avoid fumes such as hydrogen sulfide, a potentially dangerous gas. High volume pumps can lift a loading spout out of the truck, so make sure the spout is properly secured. When the tanker is loaded, make sure all covers are properly secured before the vehicle is moved.
At the Hot Mix Plant
Drivers and plant workers should also be aware of the potential hazards at the hot mix plant. A bad connection in a line can cause asphalt to spray out and burn someone. Pumping a load into the wrong storage tank may result in product contamination, causing the resultant mixture to become degraded.
Pumping hot asphalt into tanks containing water, emulsions or cutback asphalts can cause boil-overs, fires and tank failure. Also, make sure that there is enough room in the storage tank to hold the new load.
Tank Gauging Hazards
Currently, there are no specific OSHA standards or directives for asphalt fumes, but exposures to various chemical components of asphalt fumes are addressed in specific standards for general industry.
According to the Asphalt Institute’s Safe Handing of Hot Asphalt program, hydrogen sulfide may be released from storage tanks whenever the tank gauge hatch is open for gauging or for visual inspection. Hydrogen sulfide, a highly toxic and flammable gas, can reach hazardous concentrations inside a storage tank. At low concentrations, hydrogen sulfide emits an odor similar to rotten eggs. At high concentrations, it is odorless because it quickly deadens the sense of smell.
Odor is not a reliable indication that hydrogen sulfide is present. Personal air monitors are available that will sound an alarm when hydrogen sulfide reaches dangerous levels. If it is necessary to open the gauge hatch on an asphalt storage tank, stand upwind of the hatch and at least two feet away from openings. Leave the tank gauge platform if the hydrogen sulfide alarm sounds or an odor of sulfide is detected.
The Asphalt Institute has compiled a publication, IS-225, Management Practices for Asphalt Facility Control of Hydrogen Sulfide Exposure, which provides insight into the management practices to protect employees, contractors and visitors from the potential hazards of hydrogen sulfide exposures at a typical liquid asphalt industry facility. This publication is available from the Asphalt Institute’s website.
Training Is Necessary
A driver’s awareness of these hazards does not come naturally. Employees need to be trained to work safely. Good training programs teach and motivate employees to be a productive part of the safety culture. Current programs that help train employees to be safe include the Asphalt Institute’s (AI) A Guide to the Safe Handling of Asphalt and BP Bitumen’s TruckSafe and RailSafe programs.
AI’s Guide to Safe Handling of Asphalt provides asphalt terminal workers and truck drivers with the basic steps for handling, transporting and storing asphalt.
BP’s new TruckSafe program is designed to reduce injuries and incidents related to the handling and transporting of hot liquid asphalt by truck. BP’s RailSafe, launched in 2006, aims to reduce incidents related to the loading and unloading of liquid asphalt tankers.
“BP’s approach is to make the industry safer,” says Jackie Tavitas, BP’s Asphalt Marketing Manager. “TruckSafe is for the betterment of the whole industry. It’s not only for employees, it’s for truck drivers and all the people who handle asphalt.”
Creating a Safety Culture
The commitment and participation of the entire organization is needed to create an effective safety culture. Every person from top management to the newest employee is responsible for preventing injuries. “Safety starts with our CEO and moves throughout the company,” says Tavitas. “Our goal is to establish a company-wide safety culture.”
BP Asphalt has distributed TruckSafe kits to more than 300 of their customers, carriers and terminals, as well as their own personnel. “We’ve already gotten feedback from terminals and customers asking us to come out and talk about truck safety and handling hot asphalt,” says Tavitas. She believes that TruckSafe sends a strong message to truck drivers and all the people who handle asphalt of how important safety is.
|John Davis is a contributing writer for Asphalt Magazine.