ASME Code Section 8The ASME Code Section 8 is the construction code for pressure vessel and covers design, manufacturing and pressure vessel inspection and testing in the manufacturing shop. This Code section addresses the mandatory requirements, specific prohibitions, and non-mandatory guidance for Pressure Vessel Materials, design, fabrication, examination, inspection, testing, certification, and pressure relief. In this article you will learn about the different subsections and guidelines for the use and application of this code. For ASME Code Section 8 scope and boundaries, review the Pressure Vessel Definition article. You may know ASME Code Section 8 has three divisions. Division 1 covers pressure up to 3000 psi, Division 2 has an alternative rule and covers up to 10,000 psi and Division 3 can be used for pressure higher than 10,000 psi. Hierarchy of Standard 1. Law and Regulation at Location of Installation Mandatory application of ASME pressure vessel code is determined by rule and regulation at location of installation. For example, if you are living in the state of Minnesota, the application of ASME Code for construction and stamping is mandatory in your Welder Performance Qualification. For example. section III for Nuclear Power Plant and Section IV for heating Boiler Group 2: Reference Codes These are the codes which are referenced from construction codes as explained in group 1.location. PQR (Procedure Qualification Record). the NBIC is making certification for ASME Authorized Inspectors and is also certifying R stamp for Repair services for stamped pressure vessels. The ASME Section IX for welding and Section V for Non Destructive Testing are in this Group. The ASME Section VI for the heating boiler and Section VII are from this group. but as required for this article. the ASME Code generally is divided into three groups as following: Group 1: Construction Codes Some of them are: Section VIII for pressure vessel. . refer you to ASME Section IX. Section I for Power Boiler. it is not mandatory. Group 3: In-Service Codes These are the codes for in-service inspection after placing the equipment into service. etc. 3. National Board Inspection Code(NBIC): We have assigned a separate article for the NBIC. but if you are living in the state of South Carolina. ASME Boiler and Pressure Vessel Code The next item in this hierarchy is ASME Code itself. ASME Code section VIII for welding requirement such as WPS (Welding Procedure Specification). 2. ULW. and brazed methods. and low temperature materials. . UF. Subsection C covers specific requirements applicable to the several classes of materials used in pressure vessel construction. layered construction. respectively. Mandatory Appendices. It consists of Parts UW. forged. UHA. Subsection A consists of Part UG. It consists of Parts UCS. clad and lined material. nonferrous metals. cast iron. UNF. and UB dealing with welded. Subsection B covers specific requirements that are applicable to the various methods used in the fabrication of pressure vessels. cast ductile iron. and Nonmandatory Appendices. ferritic steels with properties enhanced by heat treatment. covering the general requirements applicable to all pressure vessels. UHT.ASME Code Section 8 Content: See following Fig. UCL. respectively. it shows ASME Code Section 8 Content: This section is divided into three Subsections. UCI. high alloy steels. UCD. and ULT dealing with carbon and low alloy steels. as well as Authorized Inspection Agency certification.. If you review the ASME Forward statement it clearly says “The Code does not address all aspects of construction activities. ASME Code Section 8 Div 1 in UG-28 mandates all loading to be considered in pressure vessel design. does not provide you fabrication tolerances except for misalignment and weld reinforcement. Edition and addenda become effective on the 1st of January of next year (i. experience. and these items and other similar loading considerations need to be designed by using the information provided in the pressure vessel handbooks. For example.” For example. .e. Please note that ASME Code Section 8. projection. for nozzle orientation.” In continuing it says. For example. once a year – both on July 1st. and the use of engineering judgments. Review the Pressure Vessel Certification article. then you need to meet the marked items in above Fig.For example. Review the Pressure Vessel Dimension Inspection article for such tolerances. elevation and other required tolerances there are no values in the code. but the method for calculation of all of them has not been addressed. “The Code is not a handbook and cannot replace education. if you need to manufacture a pressure vessel with SA 516 Gr. and those aspects which are not specifically addressed should not be considered prohibited. For ASME pressure vessel manufacture certification. What is the Summary of Important Points in ASME Code Section 8 ? 1. and you may refer to pressure vessel handbooks for such information. the formula for wind or earthquakes is not provided in the ASME Code Section 8. 6 months after issue).70 material (Carbon Steel). ASME Code Section 8 edition is issued once every 3 years and addenda. B. Longitudinal weld is more critical because it is subjected to double the stress than Circ. D – are based on joint locations in the vessel and stress levels encountered. Weld Types: Type 1: Full penetration welds (Typically Double welded) Type 2: Welds with backing strip Type 3: Single welded partial penetration welds Type 4.2.Head to shell joint (other than Hemisph. 2. 85%.6P) + C 3.) 6. heads are D/4 and D/2 respectively. etc. . 7.All welds in heads. 5 and 6: Various Lap welds (rarely used) 8. (D= Head diameter. Thickness of cylindrical shell t = PR/(SE-0. Spot. C. Nil respectively) . E = 100%. Hemisph-head to shell weld joint Category B: . “Weld joint categories” A.) Category C and D are flange welds and nozzle attachment welds respectively. Weld.All longitudinal welds in shell and nozzles. 5. Weld Joint categories: Category A: .All circumferential welds in shell and nozzles . Depths of 2:1 Ellip. 3. 4. “Weld Types” (type 1.) describe the weld itself. 70% (For the radiography = Full. For full penetration welds (type 1): Joint efficiency. and hemisph. A Butt welds Full length. Prior to the test. Test Pr. head approx. (pneumatic) = test pressure /1.7) Partial/No radiography 10. Hydro-Test is Standard Pressure test on Completed Vessels. B) 12. 14. A welds) 11. 13. spot RT-3: (E=0. MAWP is calculated for: Working condition (Hot & Corroded). 1st step – 50% of test pressure 2nd to 6 step – 10% of test pressure Insp.1 . same as shell. Radiography marking on name plates (typically for Type-1 welds) RT-1: (E=1) All butt welds – full length radiography RT-2: (E=1. E=1. For Welded Heads for E=1. = 1. thickness of 2:1 Ellipsoidal head is approx.85) Spot radiography of both Cat A and B welds RT-4: (E=0. Pneumatic test is performed if hydro is not possible due to design or process reasons. half and Torisph head is 77% higher. Test temp. = MDMT + 30°F Max. Cat B.3 Min. A). / 1. Vessel MAWP is always taken at the Top of the Vessel and is lowest of all part MAWPs adjusted for static pressure. Inspection temp. Pressure (hydro) = test pr. Hemisph. Pneumatic test pressure = 1. and at least spot radiographed (if Cat. = 120°F 15. If a) head to shell weld is fully radiographed (if Cat. Pr.0) All Cat. For seamless heads. Compared to Cylindrical shell.3 x MAWP x stress ratio Insp. Pressure should be increased in steps (Total 6). NDT as per UW-50 is mandatory.9. all welds within the head require full length radiography (since they are all Cat. Hyd.1 x MAWP x stress ratio. Name plate shows The Code stamping. 24. 17. However. if the size of finished opening is (UG 36) Not exceeding 2-3/8” for all thicknesses of vessel Not exceeding 3-½”. Pressure is worked out on basis of Geometric factor A (which depends on L/Do and Do/t ratios) and factor B (depends on A. Ext. MDMT. in any case it shall not be lower than 1. Or 1 mtr of height = 0.) 20. For values of A falling to the left of material line in the material chart: Pa = 2AE/(3(Do/t)) 23. = Vessel MAWP + h x 0. (h = height from top in ft. For vertical vessels.43 psig. if vessel thickness is ≤ 3/8‟‟ . ASME materials (SA) shall be used for code stamped vessel fabrication instead of ASTM (A) materials. 21. Pa = 4B/(3(Do/t)) 22. hydrostatic pressure caused due to liquid with specific gravity = 1. MAWP. Reinforcement pad is not required. ) Allowable Ext.. Pressure. 1ft of height = 0. Vessel MAWP can be calculated by the deducting hydrostatic head from part MAWP.1 Bar 19. design temp. 25. adjusted for hydrostatic head.5 times and not higher than 4 times the test pressure. and Extent of Radiography. 18.433. Total pressure at any point of Vertical vessel is given by: Total Pr. Vessel MAWP is measured at top-most point and is lowest of vessel part MAWPs.16. If part MAWP and elevations are known. Pressure gauge range should be about twice the test pressure. Vessel MAWP represents the maximum safe pressure holding capacity of the vessel. PWHT is ASME Code Section 8 requirement if thickness exceeds those given in tables UCS-56 (given in notes under the tables).5 tn 29. credit can be taken for area available in shell and nozzle. 33. 38. etc. seal. 32. Reinforcement limit normal to vessel wall = smaller of 2.) shall be done using qualified procedures and welders. Compensation area shall be within reinforcement limits. Principle of reinforcement: Area removed = Area compensated. whichever is less. In reinforcement pad calculations. These . The maximum permitted ovality tolerance (D max – D min) shall not exceed 1% of nominal diameter of vessel. 37.5 t or 2. 35. 34. Adequacy of weld sizes shall be checked as required by UW-16. Reinforcement limit along vessel wall = 2d 28. the plates shall be fully identified.3 mm) or 6% of ordered thickness. Mandatory full radiography in ASME Code Section 8 is required for all welding with thickness exceeding Table UCS-57.26. Reinforcement pad with OD = 2d and thk = vessel thk is always safe (d = diameter of finished opening) 27. and also for lethal service vessels and unfired boilers with Design Pr. All welding (including tack. The nozzles construction shall be one of the Code acceptable types. More than 50 psig. The mismatch tolerances and the maximum allowable weld reinforcement is more strict on longitudinal welds compared to circumferential welds (UW-35). If there is opening.707 x leg of weld 31. 30. then the tolerance can be increased by 2% x d (d = diameter of opening) if measurement is taken within a distance of „d‟ from axis of opening. Maximum permitted under tolerance on plates is 0. Fillet weld throat dimension = 0. For use as pressure parts.01” (0. 36. For the ASME Code Section 8 impact test requirement. 39. and thickness respectively. impact testing is exempted.tables also give min. 40. 41. Additional exemptions are given as per UG-20(f) and UCS=68 (c). If MDMT-thickness combination falls on or above the curve. Still air cooling permitted below 800°F. temp difference between hottest and coldest part shall not exceed 150°F. For Furnace PWHT in ASME Code Section 8 . . Loading Temperature shall not exceed 800°F. Minimum overlap for PWHT in multiple heats = 5 ft. During soaking period. PWHT temperature and min. holding time (soaking period) based on P-Nos. cooling rate 500°F /hr/inch of thickness. heating rate 400 deg F/hr/inch of thickness. UCS 66 curve.