A WELDING REVIEW PUBLISHED BY ESAB VOL. 57 NO.1 2002
A W E L D I N G R E V I E W P U B L I S H E D B Y E S A B V O L. 5 7 N O. 1 2 0 0 2World Wide Welding
A welding review published by ESAB AB, Sweden No. 1, 2002Articles in Svetsaren may be reproduced without permission but withan acknowledgement to ESAB.PublisherBertil PekkariEditorLennart LundbergEditorial committeeKlas Weman, Lars-Göran Eriksson, Johnny Sundin, Johan Elvander, Lars-Erik Stridh,Owe Mayer, Stan Ferree, Ben Altemühl, Manfred Funccius, Dave Meyer, Donna Terry.AddressESAB AB, Box 8004, SE-402 77 Göteborg, SwedenInternet addresshttp://www.esab.comE-mail: info@esab.seRepair & Maintenance.Printed in Sweden by Geson Skandiatryckeriet, KungsbackaContents Vol. 57 No. 1 2002310131620Tank construction in Saudi ArabiaBuilding tank farms - the logistics of processchange, productivity, fabrication techniquesand distortion control as well as climateconditions are discussed in this article fromSaudi Arabia.South Korea is today’s leading shipbuildingnationSouth Korea is in the top of the world’sshipbuilding league after a spectacular growthover the past 30 years.Welding components for the petrochemicalindustry at Sirz Montaggi srlItalian company Sirz Montaggi srl isfabricating components for the petrochemicalindustry in different parts of the worldStubends & SpatterShort newsESAB/Capitol Steel case studyWith installation of new technology as a keypart of its philosophy the US Capitol Steelcompany cuts labour costs and stayscompetitive22273133Modern cutting machines and techniques inthe shipbuilding industryIn addition to cutting, marking plays animportant role at shipyards. This paperdescribes different methods for marking as wellas processors for the surface cleaning of primedmaterial and new Windows-based controllers.Welding penstocks and coiled boxes for ahydropower plant using ESAB flux-coredwireAn aggressive environment with a hightemperature, high-humidity equatorial climatein the Amazon region in Brazil makes thechoice of welding process very importantESAB Automation North AmericaA new business unit within ESAB Canada willsell and service automation equipment andproducts throughout the USA, Mexico andCanada.ESAB in the automotive industryESAB developments within welding processes,consumables, power sources, automationequipment and robot interfaces pave the wayfor the automotive industry
Tank construction in SaudiArabiaby Howard J. Hatt, Sen. M. Weld. IBuilding tank farms with automated welding processes iscertainly not new or innovative, but it was to the fabricatorinvolved in the contract discussed in this article. The logisticsof process change, productivity, fabrication techniques anddistortion control are discussed, as well as the influence of theextreme climatic conditions.Tank contractFigure 1. A general view of the site during the early stagesof construction which adequately shows the size of the tanksand the number of welded joints involved.BackgroundThe contractor, Al-Khadari Heavy Industries (KHI),based in Dammam, is active in a variety of multi-milliondollar activities which are fairly diverse and includehighway construction and street cleaning, as well as steelfabrication. The company is owned and managed by theAl Khadari brothers and was founded during the early1950s by their late father. It has grown progressivelyever since and entered the steel fabrication industry in1985 with the erection of the main fabrication complex,also in Dammam. This division is managed by Mr AliAl-Khadari, an energetic US-educated engineer, who isdedicated to improving the scope and technical abilityof the company. The company was recently audited byAramco (Arabian American Oil Co), which demandsvery high standards from its suppliers and their employees, but ultimate accreditation will provide access toa massive new market.KHI has built small tanks on site previously, althoughnothing on the scale of the current contract, whichinvolves the construction of four tanks 90 metres indiameter and 20 metres in height. The contract wasawarded by the Royal Commission and this organisationis responsible for the provision and construction of allthe civil amenities within the eastern province of thekingdom. The steel construction projects are managedwithin the commission by the consultants Bechtel, whoalso act as the QA authority for the client at the site.The tanks are for the drinking water authority andare being built to expand the capacity of an existingfacility adjacent to the site, which is located in theindustrial city of Jubail. Desalinated water from theGulf is treated, stored and pumped by this facility tothe capital Riyadh, which has minimal natural waterresources.Western or S-E Asian contractors are no longerable to compete with local companies for this type ofwork, so, in this case, TTN of Japan supplied the designsand all the steelwork. The roof supports, floor platesand shell plates arrive virtually in kit form, havingbeen cut to size and, where appropriate, pre-rolledwith machined weld preparations, all to a high standardof accuracy.To date, KHI’s experience of tank building hasfocused on MMA stick electrodes, a process which isstill predominant in the Middle East. As with mostcontracts of this size, completion dates have to becomplied with and the imposition of penal clausesadds to the incentive. There is insufficient labour withthe required skills available locally, so personnel arerecruited from agencies, usually in India, Pakistan andthe Philippines. So the use of MMA on a contract ofthis kind would be extremely labour intensive with lowsvetsaren nr 1-2002 3
The Railtrac FW1000 machine is driven by the 40Vauxiliary power supply from a MIG power source andan electronic interface permits the remote controlof welding parameters. The equipment is capableof welding in the vertical, horizontal and overheadpositions and has a pre-programmable memory whichsimplifies on-site operation. It can also be used forcutting when fitted with a suitable burning torch. MMAwould still be extensively employed on joints unsuitedto automation and as a back-up where necessary tomaintain the production schedule.Welding consumablesThe consumables for all the welding processes wereselected from the ESAB range as follows:ProcessMMAFigure 2. An A2 Circotech machine welding the horizontaljoint between the second and third courses.productivity and aggravated by a higher incidence ofdefects, especially in site conditions with welders ofvarying capability.In this situation, KHI had to review the options forthe introduction of higher productivity processes.ProcurementUltimately, it was decided that investment in fullyautomatic welding equipment to weld all the joints oneach tank was not justified, especially if the machineswere under- utilised after completionESAB was chosen as the manufacturer from whomto seek advice due to the vast product range andexperience available. The local ESAB agent Medcocarries large stocks of consumables and spare parts andhas knowledgeable aftersales personnel and serviceengineers. In addition, this is backed up by ESABMiddle East in Dubai. No other welding house in theregion could offer such comprehensive support.The submerged arc process was selected for allthe tank floors and circumferential joints on the shellsand this was provided by the ESAB A2 Minitrac deckwelders and the ESAB A2 Circotech single-sided girthwelders with ESAB LAF1000 DC power sources.The use of fully automatic MIG/MAG with gasshielded, flux-cored wire was the preferred option forthe vertical joints to be provided by the ESAB RailtracFWR1000 machine, together with the ESAB LAW400power sources and MEK4 wire feeders. This packagewas considered to be more cost effective than the moreproductive electrogas process, as the equipment ismore versatile and infinitely portable, allowing it to beadapted for a wide range of alternative applications.4 svetsaren nr 1-2002FCAWSAWConsumableOK 46.00OK 48.00OK Tubrod 15.14AOK 12.32 / OK Flux 10.71AWSE6013E7018E71T1EH12KMMAThe use of an E7018 MMA electrode was specified forthe shell because basic low-hydrogen types produce highpurity weld metal with more dependable mechanicalproperties than rutile types. The only disadvantage is thehigher degree of welder skills required and the storageof these electrodes in site conditions is more critical. Inview of the latter and the high humidity, especially inJuly/August, all the OK 48.00 was supplied in Vacpacs.FCAWWhen high productivity is required for large volumes ofvertical-up welding, the most cost-effective consumableis the rutile E71T1 flux-cored wire. It will only operate inthe spray transfer mode, which ensures high depositionrates and produces a rapidly freezing slag to maintaingood control of the molten weld metal and produce aflat profile. OK Tubrod 15.14A has exceptional runningcharacteristics and produces minimal spatter with CO2Figure 3. Vertically welded joint showing the flat and smoothprofile produced by the Railtrac machine and OK Tubrod15.14A. The minimal spatter also simplifies preparation forpainting.
shielding gas, which is commercially beneficial, as Ar-richgases are very expensive in the region.SAWOK12.32 is a copper-coated solid wire which, when usedin combination with OK Flux 10.71, produces a nominalall-weld metal UTS of 550 N/mm2. The flux is a basicagglomerated slightly alloying silicon and manganesetype with a basicity index of 1.6, which is lower than thefully basic OK Flux 10.62, which has a basicity indexof 3.4. OK Flux 10.71 therefore allows for greaterflexibility with regard to the scope of applications andcombines excellent weldability, weld appearance andslag release.Welding proceduresAll the welding procedures had to be pre-qualified inaccordance with ASME IX and the tank design code,which was API 650. The butt joint procedures were allcarried out on 22 mm plate, which then qualified themfor use on the minimum thickness of 10.5 mm up tothe maximum of 32.5 mm. Other procedures involvedfillet and lap joints.Flexibility was required for the vertical joints, soprocedures were submitted using both MMA and fluxcored wire. The root pass, however, was to be carriedout with MMA in all cases, due to the joints beingdesigned with open gaps to allow full penetration fromone side.None of the procedures required full mechanicaltesting. This was not considered necessary, as the tankswere to be built with ASTM A36 and ASTM A283 lowto medium tensile steels and were for the storage ofwater at relatively high ambient temperatures.Figure 4. Capping passes of horizontal joint welded by 2Circotech with OK 12.32 and OK Flux 10.71. The excellentweld appearance and blending of the three passes is readilyapparent.The acceptance criteria were therefore based on visualand radiographic examination, which also applied tothe welder qualification tests.ProductivityAll the shell plates are 14.5 metres long and 2.5 metreswide. With a tank circumference of 282 metres, 20 platesare required per course, which means that 50 metres ofvertical welding have to be completed on each. Thesejoints are subjected to the lowest productivity thewelding position, so a productivity comparison will bemade between MMA and FCAW on a 15 mm singleV joint.Productivity comparisonDeposition ratesMMAOK 48.00OK 48.002.5 mm@ 90 Amps3.0 mm@ 120 Amps 0.8 kg/hr1.3 kg/hrFCAW1.2 mm@ 190 Amps 2.8 kg/hr 1.41 kg/m0.20 kg/m1.21 kg/mOK 15.14 ATheoretical joint volume@ 180 cm/3Weight of root passWeight of fill and cap(Note: Joint volume includes 3 mm reinforcement.)Arc timesRoot passFill and capTotal arc timeActual time@30% duty cycleMMA15 min/m56 min/m71 min/mFCAW15 min/m (mma)26 min/m41 min/m234 min/m@50% Duty Cycleor 3 hr 54 min82 min/mor 1hr 22minsActual time per joint @ 2.5 m 9 hr 45 minTotal saving by FCAW 3 hr 24 min6 hr 20 min/per jointsvetsaren nr 1-2002 5
Tank constructionFigure 5. A view of the annular plate segments on wich theshell is erected. The fully welded floor can also be seen, but isnot welded to the annular plate at this stage.Annular ringAs with many similar construction projects, the initialactivity involves putting in the concrete foundations.The depth is specified in API 650 and will depend onthe dimensions and weight of the tank when full andon the type of ground, i.e rock, clay, soil or, in thiscase, sand.Steelwork commences with the laying and weldingof the steel segments that form the annular plate whichruns around the outside circumference of the concretebase. It is on this plate that the tank shell is built, butit is not welded to it until the third course is erectedand the shell has been dimensionally checked for theaccuracy of the circumference. Should any distortionhave occurred during the welding of the first two courses,the shell is still floating or free to move. In this way, anycorrection is more easily accomplished.The annular plate is 14.2 mm thick and the sectioninside the shell ultimately becomes an integral part ofthe tank floor, which is only 9 mm.This ensures greaterstructural integrity where it is needed, as the bottomcourse of the shell is 32.5 mm thick. The tank floor itself,however, is only under a compressive load from thetank contents as well as the roof and its supports, hencethe reduced plate thickness.which are more than adequate for the service conditionsand require no expensive weld preparations. A methodof this kind also simplifies production enormously as itallows greater tolerances with regard to fit-up. In fact,as is the case with the majority of tank construction,great reliance is placed on “dogs & wedges” for thepositioning of plates, as they are inexpensive to produceand can be re-used.It is essential that welding of the tank floor iscompleted in a strict sequence from the middle outwardsand even then every third longitudinal seam is leftunwelded until completion of the others. This is to avoiddistortion, which can be exaggerated by the ambienttemperatures that can exceed 45 C in July and 50 Cin August. As an experiment, a check was made on thedegree of expansion by placing a chalk mark at thejunction of the annular plate and the tank floor, beforethe two had been welded. This was done at 1 pmwhen the ambient temperature was 45 C and the platetemperature was 80 C. At 6 pm, a second line was madeat the same junction when the ambient temperature hadgone down but only by 10 C. The result was a gap of 30mm between the two marks, making a total of 60 mm onthe diameter, so the effect of even greater temperaturegradients can be readily appreciated. It is for this reasonthat the welding of the annular ring to the floor is carriedout when the ambient temperature is at its highestand after the bottom shell plate has been welded tothe annular plate.Should a large repair or the replacement of acomplete floor plate be necessary for any reason, theresult would be catastrophic. The affected area woulddome up and recovery might involve the renewal ofthe entire floor.Shell fabricationThe tank wall sections are 2.5 m high, requiring eightcourses to complete the overall design height of 20 m.Internal pressure from the tank contents is progressivelyreduced upwards as is the weight of the shell. Thebottom course in this case is therefore thickest at 32.5Floor areaThis is where welding commences in large volumesand the tanks in question require a large quantity ofplates measuring 9 metres by 2.5 metres to completethe floor area. In all, the weld lengths run into hundredsof metres, which is why SAW was selected as the mostproductive and cost-effective alternative to MMA.As previously mentioned, the floor is only subjectedto compressive loads and so through- thickness buttjoints are not required. All the joints are of the lap type,6 svetsaren nr 1-2002Figure 6. A two-pass lap joint as applied to all floor joints andwelded with OK Autrod 12.32 and OK Flux 10.71.
mm and each successive course in made from thinnerplate because it carries less weight than the previousone until the top, which is only 10 mm.The control of distortion is also vital during shellfabrication. With this in mind, all the lower and thickerplate courses have a double”V” weld preparation,thereby reducing the amount of weld metal to fill thejoint and permitting a balanced welding techniqueto control the distortion. All the courses with 15 mmplate and below have single “V” preparations, as it isimpractical to use double “V”. In all cases, the includedpreparation angle is 45 degrees, serving to reduce weldmetal and the risk of distortion still further.Erection commences with the first two coursesbeing tacked in position on the circumference and thevertical seams were clamped with dogs and wedges soas not to disturb the open gap.All the root passes were welded using 2.5 mm OK48.00 and filling and capping were completed with either3.0 mm OK 48.00 or with the Railtrac FWR1000 andOK Tubrod 15.14A 1.2 mm. It would have been mostbeneficial to use automated FCAW on all the verticaljoints, but a plate shipment delay put the project behindschedule, necessitating the use of MMA in order torectify the situation. In all cases, however, FCAW wasused on the outside seams due to the vastly superiorweld appearance achievable with automatic oscillation.Initially, the capping passes were split weaved,because ASME rules dictate that maximum weavingshould be three times the diameter of the electrode.This had also resulted in complaints from the clientin respect to the valley between the capping passes orexcessive reinforcement, especially with regard to thesubsequent painting. These complaints were principallydirected at the MMA – since OK48.00 is an E7018 type,the welders had difficulty keeping the split beads flatdue to the restricted weave width.At this point, KHI did not have a welding engineerto assist them with the inevitable teething troublesassociated with such an abrupt change of weldingprocesses or to interpret the codes of welding practice.It was at this point that the author came into the pictureand the first change was to adopt full-width weaving ofthe caps, to the complete satisfaction of the client.So often an ESAB client has rejected a recommendation because of a particular rule, but in themajority of cases a clause will eventually appear to theeffect “unless agreed by the client”, which enables sucha change to be made.The use of MMA on the inside and FCAW onthe outside, however, was not without its problems,especially if a repair or two was required to the inside.The higher heat input from the MMA, plus any arc airgouging followed by more welding, could cause the jointto bow out, putting that section too far out of line withthe course above, and this did actually occur on oneoccasion. A problem of this kind contravenes the designcode dimensionally and causes considerable difficultyFigure 7. Guy ropes attached to the strong backs whichserve to reduce distortion, especially where MMA welding.welding the circumferential seam above it, so remedialaction was essential, but how? You learn somethingevery day and the experience of the KHI personnelsolved the problem by removing the outside weld andre-welding. The joint was pulled back into line and wasa classic case of distortion being used to advantagefor a change.The next stage was to weld all the vertical joints onthe second course, still employing MMA on the insideand FCAW on the outside, but additional precautionswere taken to avoid a repeat of the above problem. Byattaching hand-winched steel guy ropes to the strongbacks welded to the inside joints during the MMAwelding, excessive distortion was prevented. Defectswith the automated OK Tubrod 15.14 A were extremelyrare.Welding of the first circumferential joint with theESAB A2 Circotech machines could now proceed. Theoperators had received training in Dammam and thewelding procedures were pre-qualified; no problem.Experience has demonstrated that this, however, is rarelythe case, as welding in production brings difficulties thathave not been foreseen. Since the tank
ESAB Automation North America A new business unit within ESAB Canada will sell and service automation equipment and products throughout the USA, Mexico and Canada. ESAB in the automotive industry ESAB developments within welding processes, consumables, power sources, automation equipment and robot interfaces
6.3 Mechanised/automatic welding 114 6.4 TIG spot and plug welding 115 7 MIG welding 116 7.1 Introduction 116 7.2 Process principles 116 7.3 Welding consumables 130 7.4 Welding procedures and techniques 135 7.5 Mechanised and robotic welding 141 7.6 Mechanised electro-gas welding 143 7.7 MIG spot welding 144 8 Other welding processes 147 8.1 .
seam butt welding resistance butt welding flash butt welding resistance butt welding shielded unshielded other process plasma laser resistance butt welding inert gas welding submerged arc welding atomic hydrogen shielded metal arc welding (coated electrode) esepl w w w . e u r e k a e l e c t r o d e s .
the welding processes most often used in today's industry including plasma arc cutting, oxyfuel gas cutting and welding, Gas Metal Arc Welding (GMAW), Flux-Cored Arc Welding (FCAW), Shielded Metal Arc Welding (SMAW), and Gas Tungsten Arc Welding (GTAW). Flat welding positions and basic joints will be practiced. Pipe and tube welding
3. Classification of Underwater Welding Underwater welding may be divided into two main types: a) Wet welding b) Dry welding Fig. 3.1 Classification of underwater welding 3.1 Wet welding 3.1.1. Wet welding with coated electrode Wet welding is performed at ambient pressure with the welder-diver in the water and no physical barrier
10.6 Braze-welding 460 Exercises 466 11 Joining processes (welding) 467 11.1 Fusion welding 468 11.2 Oxy-acetylene welding 468 11.3 Manual metal-arc welding 490 11.4 Workshop testing of welds 504 11.5 Miscellaneous fusion welding processes 506 11.6 Workholding devices for fusion welding 509 11.7 Resistance welding 515
Welding residual stresses and stress relieve Formation of the weld metal Solidification of the weld metal Phase transformations during welding Basics of welding methods used in welding of zirconium alloys TIC Laser Welding Electron Beam Welding Upset shape welding Resistance Appendix C -R
affected zone. Welding processes that are commonly used with the corrosion-resistant alloys are shown in Table 1. In addition to these common arc welding processes, other welding processes such as plasma arc welding, resistance spot welding, laser beam welding, electron beam welding, and submerged arc welding can be used. Because of
the limited depth of underwater welding. Welding equipment transformed from manual welding to underwater automatic welding. The efficient and low-cost underwater welding was achieved[7]. In order to study the automatic welding technology under larger deep-water environment, the underwater automatic welding system was designed in this paper. The
