API TR 934-B-2011 pdf download.Fabrication Considerations for Vanadium-Modified Cr-Mo Steel Heavy Wall Pressure Vessels.
1 Scope This best practice report complements API 934-A and specifies additional fabrication considerations that should be observed when constructing a new heavy wall pressure vessel using vanadium-modified Cr-Mo materials intended for hydrogen service at elevated temperature and pressure. It applies to vessels that are designed, fabricated, certified and documented in accordance with ASME Code Section VIII, Division 2, including Paragraph 3.4 of the ASME Code, Supplemental Requirements for Cr-Mo Steels and ASME Code Case 2151, as applicable (or equivalent international codes). Nominal material chemistries covered by this report are the vanadium-modified steels including 2 1 / 4 Cr-1Mo- 1 / 4 V, 3Cr- 1Mo- 1 / 4 V-Ti-B, and 3Cr-1Mo-¼V-Cb-Ca steels. The interior surfaces of these vessels may have an austenitic stainless steel cladding or weld overlay to provide additional corrosion resistance. 2 Normative References The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. API Recommended Practice 582, Welding Guidelines for the Chemical, Oil, and Gas Industries API Recommended Practice 934-A, Materials and Fabrication Requirements for 2 1 / 4 Cr-1Mo & 3Cr-1Mo Steel Heavy Wall Pressure Vessels for High Temperature, High Pressure Hydrogen Service API Recommended Practice 941, Steels for Hydrogen Service at Elevated Temperatures and Pressures in Petroleum Refineries and Petrochemical Plants ASME Boiler and Pressure Vessel Code 1 , Section II, Materials, Part A, Ferrous Material Specifications ASME Boiler and Pressure Vessel Code, Section II, Materials, Part C, Specifications for Welding Rods, Electrodes and Filler Metals ASME Boiler and Pressure Vessel Code Section II, Materials, Part D, Properties
3 Definitions and Acronyms 3.1 Definitions For the purpose of this report, the following definitions apply. Note that some of these definitions are also given in API 934-A and if there are any variations, the API 934-A definitions should be considered the industry standard. The definitions are repeated here for reader convenience. 3.1.1 advanced Cr-Mo steels Family of alloys including both the vanadium-modified Cr-Mo steels and the enhanced Cr-Mo steels. The latter have their strength enhanced by special heat treatments. 3.1.2 ASME Code ASME Boiler and Pressure Vessel Code, Section VIII, Division 2, including applicable addenda. 3.1.3 buyer The firm or organization acting for and on behalf of the owner, who will issue the purchase order to design and fabricate the pressure vessels. 3.1.4 conventional Cr-Mo steels Standard 2 1 / 4 Cr-1Mo and standard 3Cr-1Mo steels, with no vanadium additions. 3.1.5 final PWHT The last postweld heat treatment after fabrication of the vessel and prior to placing the vessel in service. 3.1.6 hot forming Mechanical forming of vessel components above the final PWHT temperature (but typically >900 ºC [>1650 ºF] for these alloys).
3.1.8 maximum PWHT Specified heat treatment of test specimens used to simulate all fabrication heat treatments including austenitizing and tempering, all intermediate heat treatments above 482 °C (900 °F), the final PWHT, a PWHT cycle for possible shop repairs, and a minimum of one extra PWHT cycles for future use by the owner. NOTE To determine the equivalent time at one temperature (within the PWHT range), the Larson-Miller Parameter formula may be used; results to be agreed upon by purchaser and manufacturer. 3.1.9 minimum PWHT Specified heat treatment of test specimens used to simulate the minimum heat treatment (austenitizing, tempering and one PWHT cycle, and ISR above 482 °C [900 °F]). NOTE To determine the equivalent time at one temperature (within the PWHT range), the Larson-Miller Parameter may be used; results to be agreed upon by purchaser and manufacturer. 3.1.10 owner The firm or organization that will own and operate the pressure vessel. 3.1.11 seller The successful bidder, the firm or organization receiving the purchase order to design and fabricate the pressure. 3.1.12 step cooling heat treatment Specified heat treatment of test specimens used to simulate and accelerate embrittlement of test specimens for the purpose of evaluating the potential for temper embrittlement of alloy steels in high-temperature service. 3.1.13 sub-supplier The firm or organization, acceptable to the buyer, which supplies materials and/or services to the seller in conjunction with design or fabrication of the pressure vessel.