Pipeline Welding - African Fusion Magazine - March 2011

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Cover storyPipeline welding– the complete set of solutionsAs a result of ongoing oil and gas supply and security issues,the construction of pipelines is accelerating all over the globe.African Fusion talks to Nahanni Nagle of Lincoln Electricabout the pipeline industry, his company’s long historyin pipeline welding and the comprehensive range ofsolutions now available from Lincoln Electric.Lincoln Electric’s experience withpipeline welding began in 1930using Fleetweld 5 on the construction of a 20-inch pipe 32 mileslong in the USA. Pipeline weldingreally came of age, though, when theTrans-Alaska Pipeline System (TAPS)was built between 1974 and 1977after the oil crisis caused by the YomKippur war. This war, along with anassociated oil embargo against theWest, caused a sharp rise in the oilprice, from about US 3,00 per barrelto over US 12,00 by the end of 1974,and firmly entrenched OPEC as thenew controller of crude oil prices. “Eversince then, the pipeline industry hasbeen a very important business for us,”says Nagle. Lincoln supplied muchof the equipment and consumablesused to weld the Alaskan pipeline,the cellulose 6010 electrodes and itstrue DC generators, the equivalents ofLincoln’s current Classic range of DCwelding generators.“Welding is a critical component ofany pipeline project and we at Lincolnlike any project where welding is critical because this gives our equipmentand consumables the best opportunityto be differentiated.”In South Africa, such an opportunity arose with the recent NewMulti-Product Pipeline (NMPP) fromDurban to Gauteng, currently nearingcompletion at an estimated cost ofR23,4-billion. “Pipeline welding is anindustry within an industry, and if youdon’t understand it, you won’t be ableto participate.”Pipeline industry drivers andtrendsThe use of Lincoln’s STT GMAW solution not onlyoffers productivity advantages, it also obviates theneed to remove ‘wagon tracks’ associated with anSMAW root. This can significantly reduce the amountof rework required.16The demand for clean energy has ledto a rise in world gas consumption of435% since 1965. The Energy Information Administration, part of the USDepartment of Energy, forecasts thatby 2030: world energy demand willhave grown by 55%; gas consumptionby 2,4% per year; oil consumption by1,4% per year; and gas will accountfor 26% of global energy use. “Thediscovery of huge shale gas reservesin the US is drastically changing theenergy equation there,” Nagle informsAfrican Fusion, “and new technologyis now available to access these reserves. Similarly in South Africa, Shellhas been given rights to explore some185 000 km2 of the Karoo basin forshale gas.”As a direct impact of the US shale gasdiscoveries, natural gas is predicted todouble its share of the energy market,from 20 to 40%, by 2050. Within 10years, it will account for more than50% of the US gas supply. Breakevencosts on recovery are now down to 4,00/MMbtu and estimates are thatthe discovery can supply US demandfor 90-115 years. “It is not yet clearif shale gas will impact on the futureAlaska Gas Pipeline Project, butalready, the building of new LNG terminals to cater for imports to the UShas been halted. Instead, developersare hoping to use these terminals toexport shale gas,” says Nagle.In order to increase flow rates inpipelines to meet energy demands,higher operating pressures, higherstrength pipe materials and consumables, and larger pipe diameters arebeing used. “The Industry is going forhigher and higher strength steel, eitherto run at higher pressures, to reducethe wall thickness, or a combination ofboth,” explains Nagle. “We used to useX60 pipe, now X70 and X80 are common, and several test loops of X100and X120 have already been installedin North America. The compositionchanges of these higher-strengthsteels means that consumables haveto evolve too. There is now much moreuse of low hydrogen electrodes because, in some applications, traditionalcellulose 6010 pipeline electrodesmay not be the best choice, due tothe cracking potential of such steels,”he warns.Following media coverage of several serious pipeline incidents, theindustry is also facing increased attention with respect to environmentalprotection and public safety issues.According to Nagle, this translatesAFRICAN FUSION — MARCH 2011

Cover storyA hydrogen crack in the part of a repair weld completedwith a standard electrode (9010) as opposed to a lowhydrogen electrode.The self-shielded flux-cored wires, Pipeliner NR-207s and 208s, are often thesimplest wire solution. There is no stub loss, no gas shielding is required and thesewires can be used to weld pipe grades of up to X80.into more rigorous inspection requirements on pipeline projects and muchmore emphasis on rehabilitation andmaintenance of existing infrastructure. “In the US, Chevron was fined 423 000 for spilling 33 000 gallonsof oil into a Salt Lake City creek andin June 2010, an Enbridge pipelineleaked a million gallons of oil, whichcost them 400-million to clean up,not including fines,” he says.Also changing the nature of pipeline construction is the large numbersof construction projects that havetaken place over the last three years.To accommodate productivity needs,the lack of skilled welders and highlabour costs, contractors are increasingly turning towards the use of semiautomatic and automatic weldingprocesses. “Most pipelines (45%) arestill welded using shielded metal arc(SMAW) with stick electrodes, but atotal of 40% are now welded usingflux-cored electrodes, with more thanhalf of that (25%) being welded usingself shielded flux-cored electrodes. TheUS and Canada, though, have a hugestick legacy, while flux-cored weldingpredominates in Latin America, Europe,Russia and Asia,” says Nagle.He is expecting a very fast expansion in the number of pipeline projectsacross Africa. Lincoln worked on theWest African Gas Pipeline to supplygas from Nigeria's Escravos region ofthe Niger Delta area to Benin, Togo andGhana, the first regional natural gastransmission system in sub-SaharanAfrica. “Nigeria has an insane amountof natural gas!” Nagle exclaims.have a very low tolerance for problems with welding machines, equipment or consumables. “You have tobe able to support your consumableswith certificates of composition andcompliance, for example,” says Nagle.To achieve the required productivityand quality and to satisfy the materialproperty demands, premium quality isthe minimum acceptable, and technicalsupport, imperative. “Customer serviceand value via technical solutions areour key focus areas,” says Nagle.“Lincoln is the only welding company in the world to have designed,developed and packaged weldingsolutions especially for pipeline welders,” he claims. “We have a productline called ‘Pipeliner ’ that is specifically engineered to suit the demands ofpipeline contracts.” The copper woundtrue DC generators are just the firstexample. “Very few people outside ofLincoln make these. They have been apart of Lincoln’s stable for more than50 years and are still perfect for welding in places like Nigeria. They areinsanely robust, have no PC boardsand are very easy to fix. In many placesof the world, these are still the mostappropriate solution. When you rectifyAC, you don’t get a clean DC signal,you get ripple, and pipe welding is verysensitive to ripple. Good pipe welderscan always tell the difference andthe true DC generator has long beena differentiator for us in the pipelinebusiness,” he adds.Stepping up from these, Lincolnhas developed DC Chopper , a technology which substantially smoothesthe ripple that you get out of a rectifiedAC generator. “Choppers can approachtrue DC welding characteristics whenusing the input supply from a standardAC generator. The welding machinesare a lot cheaper, though, and you getaccess to AC power, to run a grinderfor example."Modern inverters are also makingtheir way into the pipeline industry.“Inverters produce very good arccharacteristics and are now definitelyrobust enough for use in the field onpipeline projects,” Nagle suggests.Lincoln’s pipeline weldingsolutionsBeing a mission-critical process forpipeline projects, project engineersAFRICAN FUSION — MARCH 2011An overview of the growth in global pipeline construction between 2007 and 2010.17

Cover storyBy using a Bugo Piper-Bug with solid wire STT for the root and gas-shielded FCAW forthe fill passes, 30 joints per day can typically be achieved.Inverters also enable the move into thewhole range of wire welding processes,GMAW and FCAW, in particular. “Weoffer a whole range of suitcase feeders that support all of the GMAW andFCAW processes. For pipe GMAWwelding, they are designed with ahigh/low switch to allow the welderto switch to lower current parameterson-the-fly to adjust for the transitionfrom the vertical down to the overheadposition at 8 o’clock and 4 o’clock.This allows the welder to go all the wayaround the pipe without having to stopbecause the weld metal is falling out.This is typical of a feature born out ofa long engagement with the needs ofpipeline welders,” he confirms.The newest inverter-based pipewelding initiative is the development ofSurface Tension Transfer (STT ) technology. “The traditional way of doingpipe welding is to put in a stick root,which gives a concave weld bead with‘wagon tracks’ on either side caused byundercut at the fusion boundary. Thenyou do a hot pass, with the sole purpose of digging out the wagon tracksthat have been created during rootwelding. This procedure has an inherent risk of quality problems becauseone is putting in defects and then, ifthe welder is skilful enough, diggingthem out again. The STT processcompletely eliminates the undercutting problem and therefore the risk.There are no wagon tracks to dig outand therefore no need for a hot pass.“The use of STT has always beenjustified based on a productivity argument, but there is also a huge qualityadvantage,” Nagle points out. “It’s nowa very, very reliable process, which canusually be coupled with CO2 shielding18gas to give spectacular penetration.STT controls the arc so well that theCO2 becomes much easier to use andspatter is significantly reduced,” headds. The first STT welding machineswere stand-alone machines but Lincolnhas now adopted a modular approachat a much lower cost. “STT can now beadded to our new Power Wave S350simply by adding an optional bolt-onmodule. The latest technology also hasa much better inverter, upgraded from40 to 120 kHz.”Lincoln’s monitoring and recording features, built into all of its PowerWave inverter solutions, are alsohelpful in the drive to enhance pipewelding quality.“True Energy, for example, can helpcontractors to track and record the trueheat input of every weld, which helpswith quality assurance. Also, WeldScore data monitoring gives a full datarecord of the welding parameters andan instant pass/fail indication immediately after each weld is completed.This is a very useful feature for anyweld-critical application,” believesNagle. “If a welder remains betweenthe preset parameters of a good weld,then the procedure used for that weldis deemed acceptable, but if not, thedeviation is highlighted and noted asa possible problem,” he explains. Thistool provides greater traceability andconfidence in making quality welds.“Clearly it doesn’t replace the normalquality acceptance criteria, but ratheradds another indicator for inspectorsand engineers looking for potentialproblems”Turning his attention to Lincoln’sconsumable range, Nagle says thatthe consumable business has changedconsiderably over its 80 years of pipeline welding applications. “Now, highstrength steels are the norm, toughnessrequirements are high and so diffusible hydrogen is a critical issue. Also,because of the need for traceabilityand quality assurance, you need certificates for every consumable used toweld any part of a pipeline. We havetherefore designed a whole range ofwelding consumables to cater for thecurrent needs of the pipeline industry.”One common feature of Lincoln’sPipeliner consumable range is thepackaging: “All consumables are protected in hermetically sealed packagesfor example, sealed pails for fluxes andflux cored consumables, sealed cansfor stick electrodes and vacuum sealedfoil bags for solid GMAW wires. It’s allabout making the packaging robustbecause we know the consumableswill be used for critical applications insome of the harshest environments inthe world, the slopes of Siberia or theforests of the Congo. We know thatproduction requirements demand themost stringent adherence to quality,and any lack of consistency cannotbe tolerated,” says Nagle. A materialtest report is therefore issued for everylot of consumables – stick electrodes,shielded and self-shielded flux coredwires, and solid GMAW wires.“The Pipeliner consumable rangeis a large family of products,” saysNagle. It begins with the original cellulosic range, Pipeliner 6P , 7P and8P . “With diffusible hydrogen of 40ml/100g, these are not low hydrogenproduct, though,” he points out.The low hydrogen range of mildsteel and low-alloy stick electrodesincludes the Pipeliner 16P,17P and18P, for X60 and X70 pipe and forthe new X80 and X90 pipe materials, Pipeliner LH-D80, LH-D90 andLH-D100. All of these are low hydrogen electrodes and come withCharpy V-notch test certificates downto -29 C.For GMAW, Lincoln offers thePipeliner 70S-G, 80S-G and the80Ni1 with root pass capability onThe STT process completely eliminatesundercut. The root thickness is also large(5,6 mm), which eliminates burn throughon next weld pass.AFRICAN FUSION — MARCH 2011

Cover storyProductivity gains (deposition rate operating factor) for different pipeline weldingprocesses.The use of Lincoln’s true DC generatorswith its Pipeliner range of SMAWelectrodes remains the most appropriatepipe welding solutions in many places ofthe world.X100 steel and Charpy V-notch valuesof between 68 and 95 J at -50 C.These wires are all designed to givea good back bead shape when usingLincoln’s STT process.“The self-shielded flux-cored wires,Pipeliner NR-207s and 208s, areoften the simplest wire solution. Designed for vertical-down fill passes, theprocess is continuous and therefore offers productivity advantages over stickelectrodes,” says Nagle. “There is nostub loss, no gas shielding is requiredand these wires can be used to weldpipe grades of up to X80.”Completing the consumable rangeare the gas shielded flux-cored wires,the Pipeliner G70M, G80M andthe new 81M, These are suitable forvertical-up fill passes using Argon/CO2 shielding gas mixtures. They offerimproved toughness and strengths ofup to that of X100 pipe. “But to usethem you will need shielding gas and,in the field, a tent for protection againstwind,” Nagle suggests.driving contractors towards automation. Internationally, there is also a lackof skilled pipeline welders.Nagle describes two basic approaches to mechanisation on pipelinecontracts. “There are some weldingservices contractors, like CRC-Evans orSerimax, who will not only supply thenecessary pipe-welding equipment, butthey will also take responsibility for thewelding itself,” he says.Using narrow groove GMAW witha relatively expensive bevelled weldpreparation, a welding services subcontractor with high expertise andexpensive mechanised systems cantypically produce 100 to 150 jointsper day on 36-inch pipe. “This is anexpensive, high-risk, high reward scenario,” Nagle advises.But by using a lower cost solution,Bug-O Piper-Bug, for example, withSTT for root welding and fill passesusing gas shielded FCAW, 30 joints perday can typically be achieved. “Thisis a much simpler automation optionand much more suitable for Africa.It’s a medium risk, medium rewardalternative to full scale automation,”he suggests.“There are going to be a lot ofopportunities for pipeline contractorsall over the African continent,” Naglepredicts. “The people who offer the solutions best suited to the environment,be they simple, robust and reliable ormechanised, effective and productive,are going to be chosen as partners,”he says.“We believe that Lincoln Electrichas, more than anybody else, the experience and the solutions to meet thedemands of pipeline welding anywherein the world,” he concludes.The move towards automationProductivity in pipeline welding is allabout achieving a high number of quality joints per day. Deposition rate andthe arc-on time (operating factors) ofdifferent processes are key drivers ofproductivity. Continuous productivityimprovements are essential becauseof ever tighter project schedules andbudgets and an abundance of plannedprojects. Higher quality requirements,the need to reduce repair rates, smallerallowable defects and the need for consistent weld properties are all factorsAFRICAN FUSION — MARCH 2011Lincoln’s VRTEX 360 virtual welding solution is an ideal tool for training and qualifyingpipe welders in this scarce skill.19

STT controls the arc so well that the CO 2 becomes much easier to use and spatter is significantly reduced,” he adds. The first STT welding machines were stand-alone machines but Lincoln has now adopted a modular approach at a much lower cost. “STT can now be added to our new Power Wave S350 simply by adding an optional bolt-on module.