SIST EN 12953-4:2002
(Main)Shell boilers - Part 4: Workmanship and construction of pressure parts of the boiler
Shell boilers - Part 4: Workmanship and construction of pressure parts of the boiler
This Part of this European standard applies to shell boilers as defined in prEN 12953-1. This Part of the standard specifies rules for the workmanship and construction of shell boilers.
Großwasserraumkessel - Teil 4: Verarbeitung und Bauausführung für drucktragende Kesselteile
Diese Norm gilt für Großwasserraumkessel wie in prEN 12953-1 festgelegt. Dieser Teil der Europäischen Norm legt Regeln für die sicherheitstechnische Ausrüstung von Großwasserraumkesseln fest.
Chaudieres a tubes de fumée - Partie 4: Fabrication et construction des parties sous pression des chaudieres
La présente partie de cette norme européenne s'applique aux chaudieres a tubes de fumée telles que définies dans le prEN 12953-1:2001.
La présente partie de la norme européenne spécifie les regles de fabrication et de construction des chaudieres a tubes de fumée.
Mnogovodni kotli - 4. del: Izdelava in izvedba tlačno obremenjenih delov kotla
General Information
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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Großwasserraumkessel - Teil 4: Verarbeitung und Bauausführung für drucktragende KesselteileChaudieres a tubes de fumée - Partie 4: Fabrication et construction des parties sous pression des chaudieresShell boilers - Part 4: Workmanship and construction of pressure parts of the boiler27.060.30Grelniki vode in prenosniki toploteBoilers and heat exchangersICS:Ta slovenski standard je istoveten z:EN 12953-4:2002SIST EN 12953-4:2002en01-november-2002SIST EN 12953-4:2002SLOVENSKI
STANDARD
SIST EN 12953-4:2002
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 12953-4May 2002ICS 27.060.30; 27.100English versionShell boilers - Part 4: Workmanship and construction of pressureparts of the boilerChaudières à tubes de fumée - Partie 4: Fabrication etconstruction des parties sous pression des chaudièresGroßwasserraumkessel - Teil 4: Verarbeitung undBauausführung für drucktragende KesselteileThis European Standard was approved by CEN on 15 May 2002.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2002 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 12953-4:2002 ESIST EN 12953-4:2002
EN 12953-4:2002 (E)2ContentsPage1Scope.42Normative references.43Terms and definitions.44Symbols.45General requirements.55.1General.55.2Material identification.55.3Cylindrical shells.55.4Tell-tale holes.85.5End plates and tube plates.85.6Plain tubes and stay tubes.85.7Manhole frames and openings.95.8Connections for mountings.95.9Cylindrical furnaces.95.10Water-cooled reversal chamber.115.11Stays.115.12Design of welded joints.115.13Openings in or adjacent to welds.135.14Fillet Welds.135.15Fabrication.135.16Post-weld heat treatment and other heat treatments.18Annex A (informative)
Typical examples of acceptable weld details.21Annex ZA (informative)
Clauses of this European Standard addressing essential requirements or otherprovisions of EU Directives.43Bibliography.44SIST EN 12953-4:2002
EN 12953-4:2002 (E)3ForewordThis document (EN 12953-4:2002) has been prepared by Technical Committee CEN/TC 269 "Shell and water-tubeboilers", the secretariat of which is held by DIN.This European Standard has been prepared under a mandate given to CEN by the European Commission and theEuropean Free Trade Association, and supports essential requirements of EU Directive(s).For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this standard.This European Standard shall be given the status of a national standard, either by publication of an identical text orby endorsement, at the latest by November 2002, and conflicting national standards shall be withdrawn at the latestby November 2002.This European Standard EN 12953 concerning shell boilers consists of the following Parts:Part 1:General.Part 2:Materials for pressure parts of boilers and accessories.Part 3:Design and calculation for pressure parts.Part 4:Workmanship and construction of pressure parts of the boiler.Part 5:Inspection during construction, documentation and marking of pressure parts of the boiler.Part 6:Requirements for equipment for the boiler.Part 7:Requirements for firing systems for liquid and gaseous fuels for the boiler.Part 8:Requirements for safeguards against excessive pressure.Part 9:Requirements for limiting devices of the boiler and accessories.Part 10:Requirements for boiler feedwater and boiler water quality.Part 11:Acceptance tests.Part 12:Requirements for firing systems for solid fuels for the boiler.Part 13:Special requirements for stainless steel boiler servicing sterilizer.CR 12953-14:Guidelines for the involvement of an inspection body independent of the manufacturer.Although these Parts can be obtained separately, it should be recognized that the Parts are inter-dependent. Assuch, the design and manufacture of shell boilers requires the application of more than one Part in order for the re-quirements of the standard to be satisfactorily fulfilled.Annex A of this European Standard is informative.According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following coun-tries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Swe-den, Switzerland and the United Kingdom.SIST EN 12953-4:2002
EN 12953-4:2002 (E)41 ScopeThis Part of this European Standard specifies requirements for the workmanship and construction of shell boilersas defined in EN 12953-1.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text, and the publications are listed hereafter. Fordated references, subsequent amendments to or revisions of any of these publications apply to this EuropeanStandard only when incorporated in it by amendment or revision. For undated references the latest edition of thepublication referred to applies (including amendments).EN 287-1, Approval testing of welders - Fusion welding - Part 1: Steels.EN 288-3, Specification and approval of welding procedures for metallic materials - Part 3: Welding procedure testsfor the arc welding of steels.EN 1011-2, Welding - Recommendations for welding of metallic materials - Part : Arc welding of ferritic steels.EN 1418, Welding personnel — Approval testing of welding operators for fusion welding and resistance weld set-ters for fully mechanized and automatic welding of metallic materials.prEN 10216-2, Seamless steel tubes for pressure purposes — Technical delivery conditions — Part 2: Non-alloyand alloy steel tubes with specified elevated temperature properties.prEN 10217-2, Welded steel tubes for pressure purposes — Technical delivery conditions — Part 2: Electricwelded non-alloy and alloy steel tubes with specified elevated temperature properties.prEN 10217-5, Welded steel tubes for pressure purposes — Technical delivery conditions — Part 5: Submergedarc welded non-alloy and alloy steel tubes with specified elevated temperature properties.EN 12953-1:2002, Shell boilers - Part 1: General.EN 12953-3:2002, Shell boilers — Part 3: Design and calculation for pressure parts.EN 12953-5:2002 Shell boilers — Part 5: Inspection during construction, documentation and marking of pressureparts of the boiler.3 Terms and definitionsFor the purposes of this European Standard the terms and definitions given in EN 12953-1 shall apply.4 SymbolsFor the purposes of this European Standard the symbols given in EN 12953-1:2002, Table 4-1 shall apply.SIST EN 12953-4:2002
EN 12953-4:2002 (E)55 General requirements5.1 General5.1.1The rules in this Part are applicable to all aspects of fabrication, including welding, of boilers and boilerparts, and shall be used in conjunction with the specific requirements applicable to the grades of materials used.5.1.2All welding shall be in accordance with the requirements of this standard.5.1.3For category II, III and IV boilers, all welders or welding operators and welding procedures shall be ap-proved (see 5.15.3). For category I boilers, approval shall not be mandatory.5.1.4The manufacturer of a boiler, or boiler part, built in accordance with the requirements of this EuropeanStandard, shall be responsible for the welding done by his workmen. The manufacturer shall designate a compe-tent welding supervisor and also conduct the tests for the approval of the welding procedures used. No productionwork shall be undertaken on category II, III and IV boilers until both the welding procedures and the welders orwelding operators have been approved (see 5.15.3).5.1.5The manufacturer shall maintain a record of the results of welding procedure and welding approval tests.5.1.6The welds made by each welder shall be marked with a stamp showing the welder's identity or some otherappropriate record shall be made. If hand stamping is employed, only low-stress stamps shall be used.NOTELow-stress stamps are those with radiused edges or those making a series of dots.5.1.7If, during the construction of a boiler or pressure part, the work is not satisfactory or is not in accordancewith the requirements of this European Standard, the causes shall be investigated by the manufacturer and recti-fied. If necessary, requalification tests shall be undertaken and this shall be recorded.5.2 Material identificationIn laying out and cutting the material, the material identification shall be so located as to be clearly visible when thepressure part is completed. Alternatively, for materials that cannot be stamped, or for small multiple parts, or non-pressure parts, the manufacturer shall operate a documented system that ensures material traceability for all mate-rials in the completed boiler. If the material's identification is unavoidably cut out during manufacture, it shall betransferred by the pressure part manufacturer to another part of the component. The transfer of the identificationshall be carried out by a person designated by the manufacturer. The method of transferring the original identifica-tion shall not contravene the requirements of the material specification.5.3 Cylindrical shells5.3.1Each ring shall be formed from not more than two plates, bent to cylindrical form to the extreme ends of theplate. The bending shall be performed entirely by machine, and local heating or hammering shall not be used.5.3.2The shell of completed boilers shall be in accordance with the following requirements.a) StraightnessUnless otherwise shown on the drawing, the maximum deviation of the shell from a straight line shall not ex-ceed 0,3 % both of the total cylindrical length and of any 5 m length. Measurements shall be made to the sur-face of the parent plate and not to a weld, fitting, or other raised part;b) Irregularities in profile1) Gradual local departures from circularityIrregularities in profile (checked by a 20° gauge) shall not exceed 2 % of the gauge length.SIST EN 12953-4:2002
EN 12953-4:2002 (E)6NOTEThis maximum value can be increased by 25 % if the length of the irregularities does not exceed one quar-ter of the length of the shell part between two circumferential seams, with a maximum of 1 m. Greater irregularities re-quire proof by calculation or strain gauge measurement that the stresses are permissible.2) Peaking at welded seamsIf an irregularity in profile occurs at the welded seam and is associated with "flats" adjacent to theweld, the irregularity in profile or "peaking" shall not exceed the values given in Table 5.3-1.Table 5.3-1 — Maximum permitted peaking for dynamic and cyclic loadsDimensions in millimetresWall thicknesseMaximum permitted peakinge < 31,53
e < 62,56
e < 93,09
ee/3A conservative method of measurement (covering peaking and ovality) shall be by means of a 20°profile gauge or template.The use of such a profile gauge shall be in accordance with Figure 5.3-1. Two readings shall betaken, P1 and P2, on each side of the seam at any particular location, the peaking is taken as beingequivalent to 0,25 (P1+P2), or P3.SIST EN 12953-4:2002
EN 12953-4:2002 (E)7KeyaCut out in gauge to clear weld reinforcementa) 20° profile gaugeb) Reading 1c) Reading 2d) Negative peaking (flat)Figure 5.3-1 — Profile gauge and its method of usec) Departure from circularityThe difference between the maximum and minimum internal diameter of any section of a shell welded longitu-dinally shall not exceed (D+1250)/200, where D is the nominal internal diameter expressed in millimetres.Measurements shall be made to the surface of the parent plate and not to the weld, fitting or other raised part.Shell sections shall be measured for departure from circularityeither when laid flat on their sides or when setup on end. If the shell sections are checked when laid flat, each measurement for diameter shall be repeatedafter turning the shell through 90 about its longitudinal axis. The two measurements for each diameter shallbe averaged to give the out-of-roundness.Any local departure from circularity shall be gradual.SIST EN 12953-4:2002
EN 12953-4:2002 (E)8d) Cold rollingCold rolling of a welded shell to rectify a small departure from circularity shall be permitted, provided thatnon-destructive testing conforming to EN 12953-5:2002, 5.3 is carried out after the departure from circularityhas been remedied.5.4 Tell-tale holesReinforcing plates and saddles of nozzles attached to the outside of a boiler shall be provided with at least onetell-tale hole that may be tapped (maximum size G ¼) for a preliminary leakage test for tightness of welds that sealoff the inside of the boiler. These tell-tale holes may be left open or may be plugged when the boiler is in service. Ifthe holes are plugged, the plugging material used shall not be capable of sustaining pressure between the rein-forcing plate and the boiler wall.5.5 End plates and tube platesIf practicable, flat or dished ends shall be made in one piece except that, where the diameter is so large as to makethis impracticable, flat ends may be made from two plates butt welded together (see Figure A.1). The weld shall belocated preferably between two rows of bar stays or, if there is only one row of bar stays, between this row and thetop row of stay tubes.Dished end plates and flanging of flat end plates shall be produced either by pressing or spinning. The cylindricalskirt shall have a good surface condition and shall be free from local irregularities.Cold forming of flat flanged end plates, tube plates and dished ends shall be permitted in accordance with anagreed approved procedure, including normalising, if required.Hot forming of plates that have been dished or flanged at non-uniform temperatures, or that have been locallyheated, shall be normalized after forming unless the manufacturer can demonstrate that the safety of the compo-nent is not affected.Where hemispherical shell end plates are pressed from one plate, they shall be pressed to form by machine in pro-gressive stages, and shall be normalised on completion.NOTENormalising can be omitted for hot formed ends, when the forming process is completed at temperatures within thenormalising range.5.6 Plain tubes and stay tubes5.6.1Tubes shall be expanded or welded into the tube plate, or secured by a combination of both methods.5.6.2If the tubes are fully expanded only, the process shall be carried out with roller expanders, and the ex-panded portion of the tube shall be parallel throughout the full thickness of the plate.5.6.3In addition to expanded tubes, flared tubes, bell-mouthed tubes or beaded tubes shall be permitted.5.6.4If tubes are welded to the tube plate by welds other than full penetration welds, the unwelded portion of thetube within the tube hole shall be lightly expanded to provide full contact with the tube plate, except as permittedotherwise in EN 12953-3:2002, 6.1d).5.6.5If stay tubes are not provided, the ends of the tubes shall be welded or expanded and beaded at the inletend and welded or expanded only at the outlet end.5.6.6Welding of tubes shall be permitted after stress relief of the boiler.SIST EN 12953-4:2002
EN 12953-4:2002 (E)95.7 Manhole frames and openings5.7.1 Jointing flangesThe jointing flanges of openings and covers shall be machined on the face and edges and on the bearing surfaceof the bolt heads and nuts. Bolts and nuts shall be machined where they are in contact with the flanges.5.7.2 DoorsDoors shall be constructed in accordance with the following requirements.a) Doors shall be formed to fit closely to the internal joint surface and shall be fitted with studs, nuts and crossbars;b) The spigot part, or recess, of manhole and sight-hole doors shall be as neat a fit as practicable. However, in nocase shall the clearance all round exceed 1,5 mm;c) Nuts shall be compatible with the studs.5.8 Connections for mountings5.8.1 MountingsScrewed mountings (valves etc) over 25 mm internal diameter and flanged mountings greater than DN 80 shall notbe attached directly to any boiler plate, but shall be attached to suitably forged, cast or fabricated nozzles.NOTEAlternatively, nozzles can be in the form of either screwed or studded pads, forged or cut from plate or round bar.5.8.2 PadsNozzles in the form of pads in contact with the boiler shall be formed to fit closely to the plate to which they are tobe attached.If pads are used, the jointing surfaces shall be machined. The pads shall have sufficient thickness to allow thedrilling of the stud holes for mountings without the inner surface being pierced and the length of the screwed por-tion of the stud in the pad shall be not less than the diameter of the stud.5.8.3 NozzlesIf nozzles are used, the flanges shall be machined or thermal-cut by machine on the edges. The bolting flangesshall be machined on the jointing and bolting surfaces.5.8.4 Screwed mountingsScrewed mountings not exceeding DN 80 bore shall be fitted to screwed nozzles welded to the boiler. Mountingshall be able to withstand the operating pressure and temperature of the boiler.5.9 Cylindrical furnaces5.9.1Each section of a cylindrical or conical furnace shall be made from one plate. If this is not possible, nomore than two plates shall be used. The longitudinal welds shall be at least 120 apart and shall be full penetrationbutt welds in accordance with 5.12. Alternatively, furnaces shall be made from tubes to prEN 10216-2,prEN 10217-2 or prEN 10217-5. The tensile strength and minus tolerances on thickness shall be taken into ac-count.SIST EN 12953-4:2002
EN 12953-4:2002 (E)10NOTEThe welding procedure and the welder/operator for welded tubes in accordance with prEN 10217-2 orprEN 10217-5 are to be approved by the notified body.5.9.2Finished plain or corrugated furnace tubes shall be subjected to an internal and an external inspection,especially the welds and weld-adjacent zones.5.9.3For plain furnaces, the manufacturing tolerance on diameter shall be ± 5 mm. For corrugated furnaces, themanufacturing tolerance shall be as given in Table 5.9-1. Out of roundness (see 5.3.2 c)), shall not exceed 1 % forcorrugated furnaces or 1,5 % for plain furnaces. Any departure from circularity shall be gradual.Table 5.9-1 — Manufacturing tolerances for corrugated furnacesSymbolDefinitionLimit
deviationsmmdiInternal diameter+ 5, - 20ePlate thickness±
2LcorTotal length of corrugation± 25PcorPitch of corrugation±
5hHeight of corrugation± 10See Figure 5.9-1Keydi internal diametere plate thicknessh height of corrugationsLcor total length of corrugationsPcor pitch of corrugationsFigure 5.9-1 — Corrugated furnaces5.9.4The longitudinal welds of furnaces shall be placed in such a position that they can be examined from thewater side in accordance with inspection category 2 of EN 12953-3.5.9.5Corrugated furnaces and bowling hoops shall be produced by machine. They shall be normalised unlessthe manufacturing process is carried out above the normalising temperature.5.9.6If stiffeners are required, they shall be attached externally by continuous full penetration welds.SIST EN 12953-4:2002
EN 12953-4:2002 (E)115.9.7Forms of furnace connections to end plates are shown in Figure A.15. Where the furnace is inserted into ahole in the end plate, it shall be a good fit around the whole periphery.5.10 Water-cooled reversal chamberThe reversal chamber tube plates and end plates shall be welded to the wrapper plate, e.g. Figure A.14.5.11 Stays5.11.1 Bar staysAll bar stays shall be made from a solid rolled bar without a weld in its length, except those attaching the bar staysto the plates they support.Bar stays that have been hot worked shall be subsequently normalized.If a stay is in position in the boiler, its axis shall be normal to the plate it supports.A tell-tale hole shall be drilled along the axis of all bar stays. The nominal diameter of the hole shall not exceed5 mm and the drilling shall extend a minimum of 15 mm beyond the water surface of the plate.5.11.2 Girder staysThe attachment of girder stays welded directly to the crown plates shall be by means of full penetration welds.5.11.3 Tube staysTube stays shall be made from seamless or welded tube.NOTEIf appropriate, tube stays can be fitted in accordance with the requirements of bar stays as given in 5.11.1.5.12 Design of welded joints5.12.1 Weld depositionThe design of the welded joints shall be such as to provide adequate access to enable the deposition of weld metalto meet the requirements laid down in this European Standard.5.12.2 Weld crosses5.12.2.1 Pressure partsJoints shall not be permitted where more than two welded seams meet at one point.If a component is made of two or more shell sections, the longitudinal seams shall be completed before commenc-ing the adjoining circumferential seam(s). The longitudinal seams of each adjacent section shall be staggered by atleast 100 mm and they should, if possible, be located in the top half of the boiler (i.e. between 9 and 3 o'clock of thecircumference).5.12.2.2 Non-pressure partsAttachment of non-pressure parts by welds that cross, or for which the minimum nominal distance between theedge of the attachment weld and the edge of the existing main welds or nozzle welds is less than twice the thick-ness of the pressure part, or 40 mm, which ever is the smaller, shall be avoided.SIST EN 12953-4:2002
EN 12953-4:2002 (E)12If such welds cannot be avoided, they shall cross the main weld completely rather than stopping abruptly near themain or nozzle weld in order to avoid stress concentrations in these areas.5.12.3 PropertiesThe material properties of all pressure parts shall not be adversely affected by the welding of nozzles, pads,branches, pipes, tubes, and non-pressure parts to the pressure parts.5.12.4 Types of welds5.12.4.1 Full penetration weldsA full penetration weld is one in which the components of the joint shall be completely fused together through thefull depth of the joint and there shall be no unwelded lands.The following welds shall be of the full penetration type:a) longitudinal and circumferential main seams in cylindrical shells, furnaces and reversal chamber wrapperplates, see Figure A.1;b) seams in flat end plates, see Figure A.1;c) unflanged flat end plates or tube plates where they are welded.1) to shells, see Figures A.13 a) and A.13 b);2) to furnaces, see Figure A.15;3) to reversal chamber wrapper plates, see Figures A.14 a) to A.14 c); and4) to access tubes, see Figure A.16 a) and A.16 b);d) attachment of flanged end plates, see Figure A.13 c);e) welds of branches, nozzles and pads greater than DN 80 considered to be reinforcing, see Figures A.4 toA.10;f) weld neck flanges to pipes, see Figure A.12;g) manhole frames, gusset stays, furnace stiffeners, and reversal chamber girder stay attachment welds.5.12.4.2 Internal fillet welds (back welds)When unflanged flat end plates or tube plates are welded to shells, furnaces and reversal chamber wrapper plates,the internal fillet welds shall be deposited for the full circumference of the seam, except as permitted for small boil-ers in accordance with EN 12593-3:2002,Table 10.2-3, water-walls of vertical boilers and electric boilers.Other requirements for fillet welds shall be dictated by consideration of accessibility for welding. Notwithstandingthese requirements, the fillet welds shall be inserted for the full circumference of the seam, whenever it is possible,to provide the requisite quality of the finished weld.The profile of the fillet welds shall be such as to minimise harmful notch effects.If sections of the fillet welds are omitted in accordance with EN 12953-3:2002, Table 10.2-3, special considerationshall be given to the welding technique to ensure sound root conditions, which shall be proved by procedure tests.5.12.4.3 Other weldsWelds other than full penetration welds shall be permitted for welding stay tubes to tube plates, plain tubes to tubeplates, bar stays to tube plates, and fillet welds attaching compensating plates.SIST EN 12953-4:2002
EN 12953-4:2002 (E)135.12.5 Weld preparationsThe dimensions and shape of the edges to be joined shall permit sound welds (see 5.12.1).5.12.6 Welding plates of unequal thicknessIf plate edges of unequal thickness are abutted, and if the difference between the surfaces on either side exceedsthat specified in 5.15.9, the thicker plate shall be trimmed to a smooth taper
15°, including the width of the weld ifso desired.5.13 Openings in or adjacent to weldsOpenings in or adjacent to welded seams shall be avoided, especially if the seams are not stress relieved. Theminimum distance from the centreline of the welded seam to the nearest point of the weld of the connection, oredge of the opening, shall be 60 mm, or four times the shell plate thickness, whichever is the larger.NOTEIf this is not possible, it is recommended that the opening seam should cross the welded seam completely and sothat the tangent at the point where the axis of the seam meets the edge of the opening is this axis as close as possible to 90.Crossing welded seams shall be non-destructively examined for a length of 60 mm, or four times the shell platethickness, whichever is the larger, on each side of the opening.5.14 Fillet WeldsFillet welds may be employed as strength welds for pressure parts provided the limitations as given in annex Ashall be observed. In order to ensure complete fusion at the root of the fillet welds, particular care shall be taken inthe layout of joints with fillet welds.5.15 Fabrication5.15.1 GeneralThe weld quality shall be in accordance with the requirements of this standard. The methods of welding mainseams shall provide full penetration and it shall be demonstrated by welding procedure tests tha
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