By Dwight Walker, P.E. and John Davis
Long-lasting, low maintenance asphalt pavement performance begins with using an asphalt binder that has uniform properties, including consistency and temperature. The manner in which the asphalt is handled and stored is critical to achieving this goal.
Asphalt Magazine talked to several companies who specialize in asphalt handling and storage and asked them what they considered the most important aspects of their business. We found that some of the key aspects of successfully storing and handling liquid asphalt include heating, permitting, safety, transporting, tank construction, tank management, environmental control and quality control.
Keeping the binder at the right temperature is perhaps the most important goal of any asphalt storage facility, says Al Meitl of Asphalt Operating Services. “The whole issue is keeping asphalt hot,” he says. “Managing the heating cost is the key to operating efficiently. Hot oil and steam are now the standard ways to heat asphalt.”
Matt Corry of American Heating says, “what has been happening in the storage and terminal business is the conversion from fire tubes to heat transfer fluid through submerged tubing. The industry is getting away from direct-fired heaters and going to heat transfer fluid systems. They are safer, more efficient and more effective in heating asphalt down in the tank.”
American Heating manufactures a shell and tube exchanger (tubes inside the unit) with fluid to heat the liquid asphalt. The fluid that American Heating uses in the heat transfer is a synthetic material that can be heated up to 550ºF. Corry says that the heat exchange fluid is designed to withstand high temperatures without degrading.
Bill Kirk, president of Associated Asphalt, operates ten terminals that cover six states. He agrees that heating is the key issue. “We have to keep the asphalt hot to satisfy our customers,” he says. “Fin tubes do a better job of maintaining temperature, but if they get blocked or clogged that can be a big problem.”
Kirk adds that heating has become his number one expense in handling and storing asphalt. He says his largest single expense used to be personnel, but now it is heating.
Bill Sparko of All States Asphalt is building a new asphalt storage facility in Massachusetts. He says the permitting process is critical—both from the local agency’s and fire marshal’s point of view. “In Massachusetts, the codes are different,” says Sparko. “Our tank farm is only the second one in the state.”
Sparko says he and his staff are working to educate the permitters so they will understand that asphalt is combustible but not flammable. “We try to make the permitters understand that asphalt is like a pile of lumber. It can catch fire, but only in rare circumstances.”
Meitl concurs that permitting can be a major problem. “It’s always a challenge,” says Meitl. “We get our permits through the fire marshals. NFPA, NEC and IFC are all recognized codes that fire marshals use.”
Currently, Massachusetts fire marshals are using NFPA No.1, which is a common code that says asphalt is combustible but not flammable. Currently, Massachusetts does not specify a standardized mechanical heating or piping code for asphalt storage.
Safety is another big consideration, says Kirk. “We’ve got to ensure safety for the workers while we keep the asphalt at an elevated temperature to meet customers’ needs,” says Kirk. “We have to guard against burns because of the elevated temperatures.”
Kirk says that wherever there are steam lines and traps, safety is an issue. “When you have steam traveling at 200 pounds pressure, even a pinhole leak can be dangerous.” Another factor that relates to safety is proper maintenance of the facility. Where there is water, there is rust and corrosion. Kirk says that safety involves constant maintenance of the terminal facilities.
Corry adds that the trend toward using oil heaters rather than fire tubes is a move toward safety. “I think we are going in the right direction when we decide to use oil heaters that pump hot oil to the asphalt tank,” says Corry. “It is a safer operation with oil heaters.”
Transporting Liquid Asphalt
Liquid asphalt is normally transferred by barge or rail from the supply source to the terminal site. It is then pumped from the barge or railcar to the storage tank. “To pipe the liquid asphalt, we use thousands of feet of metal pipes,” says Kirk. “For 25,000 barrels of asphalt, we use a mile of piping. And we have upgraded our pipes to fin tubes because they are more efficient.”
Asphalt is typically railed in and then trucked out. “The asphalt comes in between 300 and 325ºF, and it is stored at delivery temperature,” says Sparko. “We have coils at the bottom of the railcar and it takes about a day for the asphalt to heat properly, especially in winter. We have licensed steam engineers for supervising the unloading of railcars, and we heat ten railcars at a time. Once heated properly, we pump the asphalt from the cars into the tank.”
After storage, the asphalt is typically transferred from the tank to a tanker and shipped to the customer. “We transport the asphalt out in trucks usually at 325ºF,” says Sparko. “That’s the typical shipping temperature. But the trucks are not heated.”
According to Kirk, “asphalt storage tanks are capital intensive and expensive to construct. The steel and thousands of feet of pipe are expensive. It’s not just building the tank, but installing the heating coils, insulation and transfer racks that are costly,” he says. You’ve got to be careful about what you are doing and how you are doing it. Accurate and detailed construction management is extremely important.”
Tank farm owners and managers in different areas of the country confirm that tank construction is expensive. Sparko has five new tanks going up in a new facility in Massachusetts. “These are the first ones that I’ve constructed,” says Sparko. “Plant layout, tank spacing, and pipe network are all important. It’s important to have a doable plan within a set time limit. I don’t want to be left with partially built tanks.”
Byron Stromberg, a tank construction consultant with Pioneer Oil, says that planning and effective management are the keys to successful asphalt storage. “When it comes to tank farms, heating is certainly important. But the most important element is management. The manager of the facility is the key to the tank farm’s success,” says Stromberg.
Kirk adds that careful management during loading and storage is important. “We use gauges and floats in the tanks, and we are careful never to overflow a tank. It’s not only wasteful, but it is a safety hazard,” says Kirk. “Another thing—we don’t let the liquid asphalt get below the coils because when it does, it can coke the asphalt.”
Health, Safety and Environment
Health, safety and environmental control are a critical part of asphalt storage and handling. Control of asphalt fumes, both in and around the work site, is an integral part of a good management plan. “Asphalt fumes are more of a perception than a real health issue,” says Kirk. “In our new terminals, we install odor controls from tanks to loading racks, and we use fans and activated carbon filters and canisters to absorb fumes.” Hydrogen sulfide (H2S) fumes are a safety consideration. H2S fumes from asphalt storage tanks or asphalt tanker trucks can cause disorientation and injury to workers. “H2S management is critical from a safety point of view,” says Meitl. “A blast of hydrogen sulfide can knock a man down.
Asphalts vary in the concentration of H2S, with heavy crudes having more H2S than light or medium ones. The Asphalt Institute has a new publication, IS-225, Management Practices for Asphalt Facility Control of Hydrogen Sulfide Exposure, which provides information about the management practices to protect employees and contractors from the potential hazards of hydrogen sulfide exposure.
Kirk says his company, Associated Asphalt, has a strict quality control plan. “We’re careful of quality control and how we market our product,” says Kirk. “We want to deliver what our customers expect.”
In order to do that, Kirk says that his company segregates the suppliers. “And we do a lot of testing,” he says. “If you don’t segregate, there can be compatibility issues—and performance issues.”
Kirk goes on to say that polymer modified asphalts (PMAs) and emulsions involve a whole different set of considerations. “With PMAs we avoid contamination by keeping them separate,” says Kirk. “We don’t commingle them. We even have a separate Tank Manager to manage PMA storage.”
Kirk says that his company also requires dedicated tanker trucks. “We don’t want to ship an AC on top of an emulsion, so we make sure the drivers know what was in their tanks before loading. Our whole operation is built on awareness of product integrity,” he says. “We’re resellers. We buy from refineries—from multiple sources. We’re careful of quality control and we’re careful how we market our product. We deliver what the customer expects from us. We move toward a high standard and we are careful to meet that standard.”