Carriers should be aware of the possibility of future proposals for new vehicle weight regulations and note that those proposals, if enacted, would likely be complex with far-reaching implications, said Peter Weiss of Polar Tank Trailer LLC.
Joining Weiss in discussing topics related to cargo tanks were Duane Plumski also of Polar, Tom Anderson of LBT Inc, Charles “Shorty” Whittington of Grammer Industries Inc, Danny Shelton of HazMat Resources, John Conley of National Tank Truck Carriers (NTTC), Robert Lane of Heil Trailer International, John Cannon of Brenner Tank LLC, and Robert Koeninger of Dixon Bayco. They made presentations at the NTTC 2008 Cargo Tank Maintenance Seminar in Louisville, Kentucky, October 27-29, 2008.
Weiss pointed out that currently there are no pending regulations related to weight, but interest is rising again because of fuel prices, driver shortages, new tracking technologies, and issues involving truck size relative to miles traveled for taxing purposes.
If tank trailers are designed with heavier weight in mind, he predicted there would be no height increase and the center of gravity would be about the same. A heavier trailer likely would call for a tractor with more power.
There is a possibility that some trailer retrofits could be applied to existing equipment, but he noted that an axle spread change could make the vehicle more costly. At the same time, there could be opposition from federal regulators for retrofitting. He added that some safety advocates oppose weight limits being increased — as well as the railroad industry.
Stress analysis
Turning to another cargo tank subject, Plumski discussed finite element analysis (FEA), a numerical way of examining tank stress. Using the technique provides a more real-world view of factors affecting trailers and can be used to improve vehicle design. However, he pointed out that the technique does have limitations, so it shouldn't be used alone in the analysis process.
Anderson addressed shifting weight from the tractor to the trailer by using various strategies. He said the upper coupler can be adjusted to shift the weight, but before beginning the process, the trailer manufacturer should be consulted to determine if the coupler can be repositioned without causing problems.
To shift weight from the trailer to the tractor, the upper coupler can be moved to the rear, but proper tank clearance is required. He also pointed out that tractor design affects how well the positioning will work. In addition, he said that with compartmentalized tank trailers, load capacities can be varied, but adjusting the volume will have to coincide with the carrier operation. If adjusting the volume is possible, the coupler adjustment is not required.
MC331 tanks
Whittington turned the discussion to MC331 tanks and their condition. He advised carriers when buying an MC331 tank trailer to determine who conducted the required tests. In addition, it is essential to build a relationship with maintenance facilities that will be maintaining the tank trailers in order to insure quality service. Carriers should communicate to maintenance facilities exactly what services are expected and to confirm that the shop personnel understand the requirements.
He advised carriers to verify the results of shop inspections, ask for referrals, inspect facilities periodically, and interview employees. Feedback from carrier employees about the maintenance service also is important.
Shelton seconded Whittington's suggestions for addressing maintenance and repair services. Procedures for testing and inspections should be verified, as well as safety practices, he added. Shelton advised checking for the type of harnesses used in fall protection and obtaining information about the confined space entry requirements the facility employs. Ask questions, he said: How do you know your registered inspectors are properly trained? How do you determine if a product has been corrosive to a valve? Do you have a bench tester? How do you document procedures and training?
Conley added that carriers should confirm that facilities are properly registered and that registrations are up to date. He pointed out that facilities welding to a code vessel are required to have National Board of Boiler and Pressure Vessel Inspectors “R” stamps. American Society of Mechanical Engineers (ASME) “U” stamps are required for cargo tank fabrication and manufacturing.
Ethanol tests
Lane discussed the effect of ethanol on aluminum tank trailers and noted a study conducted by Alcan Inc in which tests were performed using different alloys and fuel blends that included E100, E85, and pure gasoline. Preliminary conclusions indicate there is no corrosion or weight change, and no problems appeared in weld interfaces as a result of exposure to ethanol.
The study is scheduled to continue and future tests will include the addition of water to the product to determine whether that creates possible tank problems.
Cannon advised carriers to research information about various products that will be hauled and determine compatibility. Resources are available in libraries, on the Internet, and from laboratories, manufacturers, and metallurgists. Some steel companies publish handbooks. He also recommended reviewing the Department of Transportation hazardous materials table.
Carriers unsure about product compatibility should get another opinion. If corrosion problems are occurring, pre- and post-step inspections will help focus on potential causes. Another way to handle suspected corrosion is to consult with cleaning facility personnel to determine the best wash recipe to protect the cargo tank.
Koeninger addressed common failures of overfill protection systems and how to prevent them. He said that when a system is operating erratically there may be cuts or breaks in the cable jacket, which can result in corrosion to the conductors inside. Cable jacket penetration may not always be visible, he pointed out, but any moisture accelerates the process of corrosion.
To reduce damage to the jacket, he advised removing razor knives and box cutters from use and apply tools that can be adjusted to avoid slitting the jacket. If mechanics use a razor knife, they should exercise caution to avoid nicking conductors inside the jacket. He also recommended tools be used that are suggested by overfill protection manufacturers.
Some equipment in the on-board monitoring system may be resistant to water, but it is not water-tight. As a result, substances used in cleaning can be conductive and can cause rust and corrosion. This is also true on the back of socket housing when water on the highway is thrown up from the vehicle's wheels.
In addition, newer rack monitors that have signal processing inside are more selective, so any moisture on back of socket can cause problems. A hand-held tester won't detect microchanges, he said.