Proposed ASME Design Standard Riles International Tank Sector
Jul 1, 1998 12:00 PM
Efforts by a US engineering association to develop international standards for tank container builders have touched a raw nerve overseas. While it is agreed that an international accreditation standard is needed, there is no consensus on the source of that standard.
International accreditation issues were among the topics discussed during the recent Tank Container Association (TCA) seminar that was held in conjunction with the International Intermodal Expo May 6 to 8 in Dallas, Texas. The TCA sessions were May 7. The Department of Transportation precipitated the overseas uproar by asking the American Society of Mechanical Engineers (ASME) to develop a new standard for cargo tanks, including those used in international transportation operations. ASME responded by establishing Subcommitee XII, Transport Tanks, under the Boiler and Pressure Vessel Code Committee.
"DOT officials won't recognize anything but a US standard, and they want a level of detail in a cargo tank design standard that is lacking in the current UN (United Nations) requirements," said Allen Selz, Pressure Sciences Inc. Selz is chairman of ASME Subcommittee XII and a member of ASME Main Committee VII.
"DOT had several important reasons for selecting ASME to develop the new standard," he added. "Over the past 25 years, ASME has become an international code-writing body, and there is a clear need for rules that are internationally acceptable. Both the international manufacture and international use of transport tanks will be facilitated by a code that is used worldwide. DOT also wanted to take advantage of ASME's experience in working with third-party inspection organizations in the United States and around the world.
"It is our intention to make this new code easily usable for construction and in-service inspection in any country, so that transport tanks built anywhere can be used anywhere. In addition, we want to make the code easy to apply internationally. The language will be English. We will work on a simple format, and we will use metric units.
"We will apply the idea of equivalence. The qualifications for engineers, designers, and others in various jurisdictions should be equivalent, not necessarily identical. We will leave this up to the jurisdiction, perhaps with approval by ASME."
International use of the ASME Code has grown steadily since about 1972, Selz said. There are approximately 650 non-nuclear ASME stampholders outside the United States and Canada, with about 350 currently in Europe.
Membership on the subcommittee includes DOT officials and representatives from TCA. They approved a draft outline of the new Section XII in September 1997 and hope to complete a rough draft of the new standard by the end of 1998. A final draft won't be ready for a couple of years.
The new ASME standard will cover all types of cargo tanks, and DOT has requested that the first units covered should be multiunit tankcar tanks (Ton tanks) and IMO portable tanks used for refrigerated and nonrefrigerated liquefied gases. These tanks often are used internationally.
Rail tankcar tanks intended for operation in the United States and throughout North America would come next. The last to be covered would be highway transportation cargo tanks that are used in the United States and North America.
According to the formal scope approved by the ASME Board on Pressure Technology Codes and Standards, the subcommittee is responsible for the development of codes and standards covering the construction, in-service inspection, alteration, and repair of cargo tanks used for the carriage of dangerous goods by all means of transport (road, rail, air, and sea). The subcommittee also will develop accreditation criteria for tank manufacturers. The new codes and standards will be suitable for reference by regulatory authorities and safety organizations worldwide.
Under Section XII, tank manufacturers will be able to apply for a certificate of authorization and a "T" stamp. Code-certified cargo tank builders currently receive a "U" stamp, and "R" stamps are awarded to repair shops.
"If we follow current practice, an ASME designee will lead a survey team that establishes the qualifications of the manufacturer," Selz said. "We expect that the manufacturer's authorized inspection agency may be any Notified Body."
Specific regulations, such as the US Code of Federal Regulations, will not be referenced in Section XII, because regulations and combinations of regulations differ among potential users. If the subcommittee does its job correctly, code tanks will meet the regulations of any political jurisdiction or provide equivalent safety, according to Selz.
In general, Section XII will not set requirements for equipment outside the boundary of the pressure vessel, such as trucks, shelf-couplers, or wheels for railcars. Some exceptions are possible, though. For example, the supporting frames for tank containers should be built to some standard, and rules may need to be included in an appendix to Section XII.
"We would like to create a code in which there are three or four classes of construction," Selz said. "Within these classes, allowable stresses (and therefore, wall thicknesses) would be determined based upon the properties of the material, the degree of nondestructive examination of the original construction, the thoroughness of the design and analysis, the acceptability of user operating and recordkeeping procedures, and the frequency and degree of in-service inspection."
The subcommittee plans to create a structure for non-ASTM materials (DIN Standards, for example). Selz said that Subcommittee II, Material Properties, already is addressing this issue. Some technical problems are introduced because, for example, some ASTM and non-ASTM testing methods are different.
ASME, in conjunction with the American Welding Society and other technical societies, has been developing standardized welding procedures. The subcommittee plans to incorporate them in the new cargo tank standard. Procedure qualification would no longer be required of the manufacturer for these standard welds.
Another element that is likely to be incorporated into the new code is the Central Certification Program that was developed by the American Society for Nondestructive Testing. The program probably would be used as the basis for certification of testing personnel.
While agreeing that tank containers used to transport hazardous materials should be designed and operated as pressure vessels, Bernd Schulz-Forberg, head of department III, German Federal Institute for Materials Research and Testing (BAM), strongly rejected the suggestion that the proposed ASME code should be adopted as the international standard.
"The UN recommendations, maritime traffic, and the European road/rail transport rules provide that the respective competent authority in each country must decide which pressure vessel code has to be used," he said. "In Germany, the general procedure is that practically any frequently used code may be taken as reference. This procedure is regarded as being advantageous because it provides flexibility without impairing overall safety."
Schulz-Forberg 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. He provided a list of pressure vessel codes that are now in place in various countries:
Argentina-IRAM A.25 Australia-AS 1210 Canada-CSA B51-M1991 [=Code ASME] Czech Republic-CSN 078304+CSN 078305 Finland-SFS 3205+SFS 3339 to 3342 France-CODAP 90 Germany-AD-Merkblatter India-IS 2825 Israel-SI specification #19 Italy-ANCC Codes including VSR/M/S collections Japan-JIS-B 8270 to B 8285 Mexico-Norm standards Netherlands-Regels voor toestellen onder druck Norway-TBK 1-2 or 4 Peru-INTITEC Standards Philippines-PSME Spain-UNE 9, 300 parts 1-0 Sweden-Pressure vessel code and sold sketching code Switzerland-SVDB Code (1992) Taiwan-ROC standards CNS 9788 to 9803 Thailand-TIS 359 (1980) United Kingdom-BS 5500 United States-ASME Russia-GOST standards
Schulz-Forberg added that the latest edition of the UN recommendations for portable tanks contains a section that states: Shells shall be designed and constructed in accordance with the requirements of a pressure vessel code recognized by the competent authority.
"We don't need a harmonized pressure vessel code dealing with the whole spectrum of tanks," he said. "We see this as a barrier to international shipments. The various pressure vessel codes in use around the world deserve consideration, and it may be necessary to develop a multiple recognition agreement that acknowledges the other codes.
"In the long run, a special pressure vessel code should be developed but only for tanks used in international shipments. This code should be developed by ISO (the International Standards Organization)."
Robert Richard, assistant international standards coordinator for DOT's Research and Special Programs Administration, said the multitude of pressure vessel codes have posed difficulties for government officials assigned to the UN working group that has been writing harmonized rules for portable tanks. "We couldn't adopt just any pressure vessel code," he said. "We have tried to compare the various pressure codes in use worldwide, but we also have asked ASME to work on a code for transport tanks. This is all part of an effort to develop model regulations that can be adopted universally."
Richard also reviewed other rulemaking activities that are directed at tank containers. Most importantly, work has been completed at the United Nations on general harmonization of tank container standards.
A new T-code system for designating various types of tank containers is one of the changes that was adopted in the new standards. Richard said the United States will incorporate the UN changes into the DOT regulations.
Further changes to the international standards are anticipated, and work is already underway in several areas. A new UN working group is developing ISO-based standards for multi-element gas containers-tube containers like those used to ship compressed gases such as helium. "We want to combine this with another program in which international standards are being developed for cylinders," Richard said.
The United States has proposed standards for tank containers used to transport hazardous cargoes that are poisonous by inhalation/toxic by inhalation. Proposed requirements call for an insulated tank with a steel jacket. Existing portable tanks that are used for PIH/TIH products would be grandfathered.
Domestically, the DOT has proposed in HM-215C to waive the 21Ž2-year retest requirement for tank containers in dedicated service. Through HM-166Y, DOT is proposing that tank containers be fitted with the same sort of pressure- and vacuum-relief vents as US tank trailers. Tank container industry representatives pointed out during the TCA meeting that this would be a purely US requirement and would hurt international harmonization efforts.
Kevin Green, tank container specialist with Transport Canada, reviewed UN efforts to develop a standardized rail impact test for tank containers. Research was done in Canada in 1997 with railcars traveling at four, six, and eight miles per hour.
The procedure approved for the test is based on the shock response spectrum, which is used in calculating seismic loads from earthquakes and explosions. Accelerometers on the container corner castings were used to record shock response.
"It won't matter where the shock test is done or how it is performed," Green said. "It just has to meet the parameters that have been developed. We will do further evaluation of the standard curve that we developed. The work will be done this summer by Welfit Oddy and CPV (Containers and Pressure Vessels)."
Domestic rail issues were covered by Ed Pritchard, hazmat division of DOT's Federal Railroad Administration. He outlined an 18-month review that is intended to remove defective equipment from the US rail system.
"One of the biggest problems we're finding is with tie-down equipment for intermodal containers," he said. "Equipment has been falling off railcars all over the country. We're finding ineffective inspection and maintenance programs. Maintenance is being delayed or neglected."
Aging containers are another concern. "We have developed criteria for maintaining the structural integrity," Pritchard said. "I don't think we're seeing tank containers that are as beat up as dry freight boxes. However, tanks do deteriorate if they aren't maintained properly."
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