Tank Truck Industry Takes Interest

May 1, 1999
In ASME Pressure Vessel Code Plans Representatives from the tank truck industry are taking a growing interest in the planning for new boiler and pressure

In ASME Pressure Vessel Code Plans Representatives from the tank truck industry are taking a growing interest in the planning for new boiler and pressure vessel codes currently underway by ASME (American Society of Mechanical Engineers) International.

Members of the new subcommittee on Transport Tanks (XII) of the ASME Boiler and Pressure Vessel Committee gathered for a February 22-26 working meeting in Birmingham, Alabama. Several manufacturers of tank trailers and components sat in on the discussions.

Greater involvement is expected as the tank truck industry becomes more aware of the implications involved, especially regarding DOT400 series trailers.

"We needed the expertise of motor and rail carriers earlier, but now we have them coming to the meetings," said Allen Selz, chairman of the Transport Tanks Subcommittee and president of Pressure Sciences Inc of Pittsburgh, Pennsylvania.

Several other subcommittee members commented on the tank truck industry interest, which is particularly focused on codes that would apply to low-pressure DOT400-designated trailers. High-pressure cargo tanks, such as the MC331s, already fall under ASME scrutiny. Some manufacturers, and others who are involved with the DOT400s, are concerned about these trailers becoming subject to what will be the new ASME codes.

Among the possibilities of what might affect DOT400-series trailers are maintenance requirements, testing procedures, and safety applications.

The seemingly late interest taken by the tank trailer industry was prompted because the initial ASME emphasis was placed on ton tanks and tank containers. But Selz pointed out that it is difficult to address codes for one or two types without addressing all kinds of tanks, so gradually the planning sessions have encompassed tank trailers.

There is European opposition to the ASME code being adopted as an international standard. Opponents have said that experience in Europe and many other parts of the world has shown that the use of different pressure vessel codes for transport tanks does not lead to any relevant differences in safety during normal operation or under accident conditions.

Different Types Although the subcommittee is working on standards for many different types of pressure vessels, a goal of the project is to encompass all modes of transportation in a single new volume of the ASME code. This is an arduous task because of the various designs, products involved, and the uses.

Selz said that rules may not be established immediately for some tanks in the single volume publication, but these tanks may be listed in code appendices for later consideration. The DOT400 series might be an example of that approach.

Another issue that has attracted attention is a DOT proposal calling for third-party inspections at the manufacturing plant and at individual repair and testing shops. The two-fold proposal calls for ASME-approved assembling procedures, as well as training programs for inspectors, both of which will have to be developed by the ASME subcommittee, or another consensus standards group, in order to launch the DOT program.

The subcommittee will address ASME codes for pressure-relief valves. Some tank trailers receiving ASME construction approval do not have ASME-approved safety relief valves, subcommittee members pointed out. However, some DOT-approved valves are used because ASME valves were found to be inappropriate for the use of the tank trailer.

"The transportation industry is a very different world," said Selz. "We need codes for valves that are technically sound, but serve the industry and meet administrative requirements."

Some subcommittee members argued that the tank trailer should not be ASME-certified by the manufacturer unless the valves were also ASME-authorized. Charles Hochman, DOT mechanical engineer and chairman of the subgroup on general requirements for subcommittee XII, noted that DOT-certified valves must test to four times working pressure.

One more subject receiving notable discussion was a rule that allows an ASME-certified repair shop to sub-contract certain welding jobs, provided supervision is implemented and ASME officials are aware of the operation. However, some subcommittee members fear the allowance may prompt abuse of the rule and lead to nonauthorized procedures.

Consideration of the issue will also be included in future subcommittee discussions.

The subcommittee was assigned the code project two years ago by the Department of Transportation at the behest of the Office of Management and Budget in a cost-savings effort to reduce overlapping responsibilities of DOT and ASME. ASME members were aware of the lengthy process that would ensue, said Selz.

The subcommittee will continue to meet independently and present progress incrementally. For more information about the meetings, contact: Paul Stumpf, engineering advisor at ASME International, (212) 591-8536.