Transport Tank Code Section Focuses on Different Needs
This article by late staff member Chuck Walters was originally published in the winter 2005 National Board BULLETIN. Some code requirements may have changed because of advances in material technology and/or actual experience. The reader is cautioned to refer to the latest edition and addenda of the National Board Inspection Code and ASME Boiler and Pressure Vessel Code for current requirements.
Throughout the history of the ASME Boiler and Pressure Vessel Code, ASME’s intended goal has been to develop a uniform set of construction rules that can be adopted by the jurisdictions and promote public safety – thereby reducing the potential for accidents and explosions.
Today, the scope of the code is expanding to include rules for continued service, repairs, and alterations.
The latest code to reflect this new direction is ASME Code Section XII, Rules for Construction and Continual Service of Transport Tanks. Section XII, like other codes, concentrates on a particular class of pressure-retaining items. Section VIII focuses its requirements on pressure vessels, while Section XII addresses requirements on transport tanks. Included in the definition of transport tanks are cargo tanks, portable tanks, rail tanks, and ton tanks transporting dangerous goods over the highways, and by rail, sea, and air. Each of these tanks is controlled under the Code of Federal Regulations, Title 49, Parts 100 through 185, Transportation. The jurisdictional authority for transport tanks is the federal government under the Department of Transportation (DOT).
Section XII was developed under the concept that transported units have different needs than pressure vessels designed, fabricated, and operated in a fixed location.
Consequently, Section XII was written to recognize different types of design rules and material requirements that would both withstand severe operating conditions and pass the proof of time needed to provide reasonable safety to the general public. Proof of time is based on developing rules for the continued service, repair, and alteration for this pressure-retaining item classification.
In developing Section XII, the committee was charged with the responsibility of blending applicable requirements of Section VIII for the construction requirements of transport tanks with the specific rules, based on Title 49, for new construction and continued service, repairs, and alterations of this equipment. The committee fulfilled its responsibility with the adoption and publication of Section XII, effective April 1, 2005.
In the development of Section XII, some very important concepts had to be considered. These included establishing rules for pressures, temperatures, and design more stringent than
Section VIII, Div. 1.
The scope of Section VIII, Div. 1, includes pressures from 15 psi to 3000 psi, whereas Section XII includes pressure requirements from a full vacuum to 3000 psi. Section XII limits both the thickness of these units to 38 mm (1½ in.) and the minimum metal design temperature to a range of -269°C to 343°C (-452°F to 650°F). Design requirements are implemented by a system of appendices (called modal appendices) for different classifications of transport tanks. For the purpose of Section XII, “modal” is defined as the transport of bulk packaging for dangerous goods.
Section XII is formatted more in line with Section VIII, Divs. 2 and 3, with respect to each part being specific to an activity. As an example, Section XII, Part TG, General Requirements, estab-lishes duties and responsibilities of the manufacturer, owner, user, and inspector, and scope of activities. Section XII, Part TD, only addresses design requirements. In other words, each part is self-contained and not repeated in any other part of Section XII.
Section XII recognizes three classifications of transport tanks: Class 1, Class 2, and Class 3.
Class 1 transport tanks, operating with pressures in excess of 35 psi, must be inspected by an authorized inspector – and depending upon the medium – in a manner similar to pressure vessels constructed to ASME Code Section VIII, Div. 1.
Inspections of Class 2 transport tanks must be performed by a “Qualified Inspector” employed by a “Qualified Inspection Organization.” A Qualified Inspection Organization most likely will be accredited by ASME (to QAI-1). The Qualified Inspector probably will be qualified (certified) by the National Board.
The concept of the Qualified Inspector and the Qualified Inspection Organization is unique to ASME Code Section XII and is not found in other code sections.
Verification that Class 3 transport tanks comply with Section XII requirements is performed by a Certified Individual. A Certified Individual is an employee of the certificate holder who is certi-fied by the certificate holder.
A major strength of this code is that all repairs and alterations to transport tanks are required to be in accordance with the National Board Inspection Code (NBIC). This requirement ensures a uniform system for this activity will be maintained. Additionally this system mandates a National Board commissioned inspector will be involved in the inspections of repairs and alterations.
With the publication of ASME Code Section XII, the NBIC Committee established a task group to develop a Nonmandatory Appendix to establish requirements for continued service, repair, and alteration of transport tanks. The task group is made up of representatives from DOT, rail car manufacturers, transport tanks users, transport tank manufacturers, metallurgists, authorized inspection agencies, and jurisdictions.
At the task group’s first meeting, it developed the following scope:
This appendix is to provide rules for continued service, repair, and alteration of transport tanks (e.g., cargo tanks, rail tanks, portable tanks, and ton tanks) that transport dangerous goods as required in the Code of Federal Regulations, Title 49, Parts 100 through 185 and the United Recommendations of the Transport of Dangerous Goods-Modal Regulations. This appendix, where possible, shall be used in conjunction with Parts RA, RB, RC, and RD of the NBIC and Section XII “Transport Tanks” of the ASME Boiler and Pressure Vessel Code.
The appendix will establish the appropriate methods to be used for continued service, repairs, and alterations inspection requirements of transport tanks. It will also establish the criteria for inspection, reports, document maintenance, and inspector duties and responsibilities. For the purpose of this appendix, the inspector, depending on the class designation of the transport tank, must be a National Board-recognized individual.
The appendix is divided into two parts. The first part is formatted for inspections such as Part RB of the NBIC. The second part is formatted for repairs and alterations and the methods used such as Parts RC and RD.
With the impending need to satisfy Section XII requirements, the task group has established an aggressive schedule for the adoption of the new appendix.
The scope of Section XII covers manufacturing, examination, inspection, continued service, repair, and alteration, and will, like other safety standards, benefit the general public in transport tank safety.