Underwater welding 1816715 223842126 2008-07-06T02:43:31Z Gene Hobbs 3121896 Merge proposal {{mergefrom|Hyperbaric welding|Talk:Underwater welding#Merger proposal|date=July 2008}} [[Image:Underwater_welding.jpg|thumb|right|200px|Underwater welding]] '''Underwater welding''' refers to a number of distinct [[welding]] processes that are performed [[underwater]].<ref name=keats>{{cite book |author=Keats, DJ |year=2005 |title=Underwater Wet Welding - A Welder's Mate |publisher=Speciality Welds Ltd |url=http://www.specialwelds.com |isbn=1-899293-99-X. |Pages=300 }}</ref><ref name=caryhelzer>{{cite book |author=Cary, HB and Helzer, SC |year=2005 |title=Modern Welding Technology |location=Upper Saddle River, New Jersey |publisher=Pearson Education |isbn=0-13-113029-3 |pages=677-681 }}</ref> The applications of underwater welding are diverse&mdash;it is often used to repair [[ship]]s, offshore [[oil platform]]s, and [[Pipe (material)|pipelines]]. [[Steel]] is the most common material welded. The two main categories of underwater welding techniques are wet underwater welding and dry underwater welding, both are classified as [[hyperbaric welding]]. For deepwater welds and other applications where high strength is necessary, dry underwater welding is most commonly used. Research into using dry underwater welding at depths of up to 1000 [[metre|m]] are ongoing.<ref>{{cite journal |author=Bennett PB, Schafstall H |title=Scope and design of the GUSI international research program |journal=Undersea Biomed Res |volume=19 |issue=4 |pages=231–41 |year=1992 |month=July |pmid=1353925 |doi= |url=http://archive.rubicon-foundation.org/2596 |accessdate=2008-07-05}}</ref> In general, assuring the integrity of underwater welds can be difficult (but is possible using various [[nondestructive testing]] applications), especially for wet underwater welds, because defects are difficult to detect if the defects are beneath the surface of the weld. == Dry underwater welding == In dry underwater welding the weld is performed at the prevailing [[pressure]] in a chamber filled with a gas mixture sealed around the structure being welded. For this process, [[gas tungsten arc welding]] is often used, and the resulting welds are of high integrity. For the structures being welded by wet underwater welding, inspection following welding may be more difficult than for welds deposited in [[air]]. Assuring the integrity of such underwater welds may be more difficult, and there is a risk that defects may remain undetected. == Wet underwater welding == In wet underwater welding, a variation of [[shielded metal arc welding]] is commonly used, employing a waterproof [[electrode]].<ref name=caryhelzer/> Other processes that are used include [[flux-cored arc welding]] and [[friction welding]].<ref name=caryhelzer/> In each of these cases, the [[welding power supply]] is connected to the welding equipment through cables and hoses. The process is generally limited to low [[carbon equivalent]] [[steel]]s, especially at greater depths, because of [[hydrogen embrittlement|hydrogen-caused cracking]].<ref name=caryhelzer/> == Risks == The risks of underwater welding include the risk of [[electric shock]] to the welder. To prevent this, the welding equipment must be adaptable to a marine environment, properly insulated and the welding current must be controlled. [[Professional diving|Commercial divers]] must also consider the [[Diving hazards and precautions|safety issues]] that normal divers face; most notably, the risk of [[decompression sickness]] following [[saturation diving]] due to the increased pressure of inhaled [[breathing gas]]es.<ref name=usn>{{cite book |title=US Navy Diving Manual, 6th revision |year=[[2006]] |publisher=US Naval Sea Systems Command |location=United States |url=http://www.supsalv.org/00c3_publications.asp?destPage=00c3&pageID=3.9 |accessdate=2008-07-05 }}</ref> Another risk, generally limited to wet underwater welding, is the buildup of [[hydrogen]] and [[oxygen]] pockets, because these are potentially [[explosive]]. Many divers have reported a metallic taste that is related to the breakdown of [[Amalgam (dentistry)|dental amalgam]].<ref>{{cite journal |author=Ortendahl TW, Dahlén G, Röckert HO |title=Evaluation of oral problems in divers performing electrical welding and cutting under water |journal=Undersea Biomed Res |volume=12 |issue=1 |pages=69–76 |year=1985 |month=March |pmid=4035819 |doi= |url=http://archive.rubicon-foundation.org/3030 |accessdate=2008-07-05}}</ref><ref>{{cite journal |author=Ortendahl TW, Högstedt P |title=Magnetic field effects on dental amalgam in divers welding and cutting electrically underwater |journal=Undersea Biomed Res |volume=15 |issue=6 |pages=429–41 |year=1988 |month=November |pmid=3227576 |doi= |url=http://archive.rubicon-foundation.org/2486 |accessdate=2008-07-05}}</ref><ref>{{cite journal |author=Ortendahl TW, Högstedt P, Odelius H, Norén JG |title=Effects of magnetic fields from underwater electrical cutting on in vitro corrosion of dental amalgam |journal=Undersea Biomed Res |volume=15 |issue=6 |pages=443–55 |year=1988 |month=November |pmid=3227577 |doi= |url=http://archive.rubicon-foundation.org/2485 |accessdate=2008-07-05}}</ref> There are also long term [[musculoskeletal]] and [[cognitive]] effects reported in underwater welders from breathing the fumes in their closed environments.<ref name=hse>{{cite journal |title=Further investigation of possible musculoskeletal and cognitive deficit due to welding in divers identified in the ELTHI diving study |year=2005 |author=Macdiarmid JI, Ross JAS, Semple S, Osman LM, Watt SJ, Crawford JR |journal=Health and Safety Executive |volume=Technical Report rr390 |url=http://www.hse.gov.uk/research/rrpdf/rr390.pdf |accessdate=2008-07-05}}</ref> ==References== {{Reflist|2}} ==External links== * [http://www.hse.gov.uk/diving/ Health and Safety Executive] - Performs research on long term health effects from underwater welding. * [http://www.twi.co.uk/j32k/protected/band_3/ksdja001.html Process overview at The Welding Institute] {{Metalworking - Welding}} [[Category:Welding]] [[Category:Underwater diving]] [[fa:جوشکاری زیر آب]]