Scopes of RTP-1 and Section X, Classes I & II and Design Qualification PUBLIC ACCESS

[+] Author Affiliations
Peter J. Conlisk

Conlisk Engineering Mechanics, Inc., St. Louis, MO

Paper No. PVP2002-1248, pp. 321; 1 page
  • ASME 2002 Pressure Vessels and Piping Conference
  • Pressure Vessel and Piping Codes and Standards
  • Vancouver, BC, Canada, August 5–9, 2002
  • Conference Sponsors: Pressure Vessels and Piping Division
  • ISBN: 0-7918-4650-4
  • Copyright © 2002 by ASME


The ASME does not require design calculations for Section X, Class I vessels. Design qualification is by destructive testing of a prototype vessel. The candidate vessel undergoes repetitive pressure testing up to the design pressure for as many as 100,000 cycles, depending on the type of FRP laminate in the vessel. If the vessel passes the fatigue test, it is then pressurized to six times the design pressure. If it also passes this test, vessels identical to the prototype may be built and receive the code mark. The prototype does not receive a code stamp. Rigorous quality assurance requirements insure that the production vessels are the same as the prototype. The ASME does require design calculations for Class II vessels. It also has stringent quality assurance and inspection requirements. Every Section X Class II vessel must also pass an acoustic emission examination before it receives a code stamp, thereby providing experimental verification of the structural integrity of the vessel. Class I and Class II vessels have different size and pressure scopes. Class I has no geometric limitations. The maximum design pressure for Class I is limited to 150 psig for bag-molded, centrifugally cast, and contact molded vessels, 1500 psig for filament-wound vessels, and 3000 for psig filament-wound vessels with polar boss openings. Class II vessels may be designed by rules or by stress analysis. For vessels designed by rules the diameter must lie between 6 in. and 96 in., and the maximum design pressure is 75 psig. Vessels that are designed by stress analysis must have diameters between 6 in. and 144 in. Their maximum design pressure varies with diameter: from 6 in. to 36 in. the maximum design pressure is 200 psig., and from 36 in. to 144 in. the design pressure is given by P = 7200/D where P is in psi. and D is in inches. RTP-1 has no size restrictions, but design pressure is limited to 15 psig. In both classes of Section X and in RTP-1, external design pressure must be less than 15 psig. Design calculations for FRP differ from calculations for metal vessels because FRP behaves differently from steel and other vessel metals. The material behaviors are compared and the resulting calculation differences are discussed.

Copyright © 2002 by ASME
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