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1、U,nR,eg,is,te,re,d,Welding,Cutting and Brazing,U,nR,eg,is,te,re,d,l,Introduction,Welding,cutting,and brazing are exceptionally dangerous.Compressed gases are often used to create an extremely hotflame.Different welding techniques can cause other hazards.,The welder can be injured or cause damage to
2、the work area innumerous ways including fire,explosion,gas,and fume hazards.,Good work practices must be followed in all welding,cutting,andbrazing techniques to prevent injuries,fires,and explosions.,This module covers the following sections:,Compressed Gases,l General Requirements,l Oxygen-Fuel Ga
3、s Welding and Cuttingl Arc Welding and Cuttingl Resistance Welding.,U,nR,eg,is,te,re,d,l,l,l,l,Introduction-Objectives,At the end of this Welding,Cutting,and Brazing module,you shouldbe able to:,Understand the general requirements concerningcompressed gases,l Identify the general safety requirements
4、 for all types of weldingl Understand the general characteristics for the various types of,welding,l Identify the specific safety requirements for:,Oxygen-fuel gas welding and cuttingArc welding and cuttingResistance welding.,U,nR,eg,is,te,re,d,Compressed Gases-Introduction,Many welding and cutting
5、operations,require the use of compressed gases.Tounderstand these hazards,we mustunderstand that compressed gases are,stores of potential energy.It takes energy tocompress and confine the gas.That energyis stored until purposely released to performuseful work or until accidentally released bycontain
6、er failure or other causes.,Some compressed gases,acetylene forexample,have high flammability,characteristics.Flammable compressedgases,therefore,have additional storedenergy besides simple compression-,release energy.Other compressed gases,such as nitrogen,have simple asphyxiatingproperties.Some co
7、mpressed gases,suchas oxygen,can augment or compound firehazards.,U,nR,eg,is,te,re,d,l29,l29,l,l,l,Compressed Gases-Introduction,Compressed gases are regulated by many standards.Two primary standards are:,CFR 1910 Subpart Q Welding,Cutting,andBrazing covers the handling,storage,and use ofcompressed
8、gases,such as oxygen-fuel gas,whenthey are consumed in the welding process.,CFR 1910 Subpart H Hazardous Materials,1910.101-1910.105 covers the general,requirements for the handling,storage,and use ofcompressed gases other than those consumed in thewelding process.The General Requirements section of
9、1910.101 is concerned with:,Cylinder inspection to include required markingsHandling,storage,and utilization,Installation and maintenance of safety reliefdevices,U,nR,eg,is,te,re,d,Compressed Gases GeneralRequirements,In addition to the Occupational Safety and Health,Administration(OSHA)regulations
10、found in Subparts Qand H of 29 CFR 1910 there are other applicableregulations and information.These include the,Department of Transportation(DOT)regulations,and theCompressed Gas Association(CGA)pamphlets.Thesesources provide the requirements for the generalcategory of compressed gases and certain s
11、pecificcompressed gases.,An important aspect of these regulations is the safety ofcompressed gas storage containers.Specific,requirements are made of employers for the inspection ofthe compressed gas cylinders.Visual inspections arerequired to ensure that the cylinders are safe.The nextpage will go
12、into more detail regarding visual,examinations of compressed gas storage containers andthe safety of these containers.,U,nR,eg,is,te,re,d,Compressed Gases GeneralRequirements,Employees shall determine that compressed gas cylinders under theircontrol are in a safe condition to the extent that this ca
13、n be determined byvisual inspection.Visual and other inspections are required,but otherinspections are not defined.These inspections must be conducted asprescribed in the Hazardous Materials Regulations of the DOT contained in49 CFR Parts 171-179 and 14 CFR Part 103.Where these regulations arenot ap
14、plicable,these inspections shall be conducted in accordance withCGA Pamphlets C-6 and C-8.,According to DOT regulations:A cylinder that leaks,is bulged,has,defective valves or safety devices,bears evidence of physical abuse,fire orheat damage,or detrimental rusting or corrosion,must not be used unle
15、ss itis properly repaired and requalified as prescribed in these regulations.,The term cylinder is defined as a pressure vessel designed for pressureshigher than 40 psia(pounds per square inch absolute)and having a circularcross section.It does not include a portable tank,multi-unit tank car tank,ca
16、rgo tank,or tank car.,U,nR,eg,is,te,re,d,1.,2.,3.,4.,5.,6.,7.,DOT Marking Requirements,Each DOT marking identified on this page must appear on all cylindersand must be maintained so that it is legible.,The circled numbers on the graphic correspond to the numbereddefinitions provided below.,ICC or DO
17、T marking may appear:,ICC:Pre-existing marking ICC 3AA20153AA-specification from 49 CFR 178.372015-marked service pressure.,DOT:new manufacture marking must read DOT.49 CFR 171.14.A35798641:Serial number-no duplications permitted with anyparticular symbol-serial number combinations.PST:Symbol of man
18、ufacturer,user,or purchaser.,6 56:date of manufacture.Month and year.:disinterestedinspectors official mark.,+:indicates cylinder may be 10%overcharged per 49 CFR 173.302(c).5-61 and 5-66:Retest dates.,*(5 pointed star 0:indicates ten year retest interval.See 49 CFR 173.34(e)(15).,U,nR,eg,is,te,re,d
19、,Compressed Gases GeneralRequirements,In addition to the guidance in the OSHA regulations,Compressed Gas Association(CGA)pamphletsdetermine requirements for handling,storing,andusing compressed gases in cylinders,portable tanks,rail tankcars,and motor vehicle cargo tanks.They alsoidentify how to ins
20、tall and maintain required pressurerelief valves on these containers.,The in-plant handling,storage,and utilization of allcompressed gases in cylinders,portable tanks,railtankcars,and motor vehicle cargo tanks shall be inaccordance with CGA Pamphlet P-1.,Compressed gas cylinders,portable tanks,and c
21、argotanks shall have pressure relief devices installed andmaintained in accordance with CGA Pamphlets S-1.1and S-1.2.,U,nR,eg,is,te,re,d,l,l,l,Compressed Gases SpecificGasesThe OSHA regulations contain some sectionsregulating specific compressed gases,including:,lll,AcetyleneHydrogenOxygenNitrous ox
22、ideAnhydrous ammoniaLiquefied petroleum gases.Other compressed gases are in common useand fall under regulation Subpart H,1910.101.Examples include chlorine,vinyl chloride,sulfurdioxide,methyl chloride,hydrogen sulfide,ethane,compressed air,and nitrogen.,U,nR,eg,is,te,re,d,l,l,l,l,l,General Requirem
23、ents-Introduction,The General Requirements section,1910.252 provides information aboutprotecting individuals during welding,cutting,or brazing operations.This sectioncontains the three topics listed on the left.,Protection of the individual includesmeasures taken to:,Prevent fires from occurringElim
24、inate fires if they occur,Protect personnel by providing appropriateclothing and equipment,Protect personnel when welding or cuttingcontainers,Protect personnel working in confinedspaces.,U,nR,eg,is,te,re,d,l,l,l,General Requirements FirePrevention and Protection,Fire prevention and protection inclu
25、de basicprecautions,special precautions,and safetyprecautions for the unique situations involvingwelding and cutting containers,and welding inconfined spaces.,The basic precautions for fire prevention in welding,cutting,and brazing focus on removal of fire hazards.They include the following:,If the
26、object to be welded or cut cannot readily bemoved,all movable fire hazards in the vicinity shallbe taken to a safe place,If the object to be welded or cut cannot be movedand if all the fire hazards cannot be removed,thenguards shall be used to confine the heat,sparks,and slag,and to protect the immo
27、vable fire hazardsIf the above requirements cannot be met,thenwelding and cutting shall not be performed.,U,nR,eg,is,te,re,d,l,l,General Requirements FirePrevention and Protection,Complying with the basic precautions for prevention of fires in welding is notenough.Special precautions must also be ta
28、ken.These include having theproper fire extinguishing equipment available and having fire watcherspresent,if needed.,Suitable fire extinguishing equipment shall be maintained in a state ofreadiness for instant use.Such equipment may consist of pails of water,buckets of sand,hoses,or portable extingu
29、ishers depending upon the natureand quantity of the combustible material exposed.,Fire watchers are required whenever welding or cutting is performed inlocations where more than a minor fire might develop,or where any of thefollowing conditions exist:,Appreciable combustible materials,in building co
30、nstruction or contents,closer than 35 feet to the point of operation,Appreciable combustible materials more than 35 feet away,but are easilyignited by sparks.,A fire watch shall be maintained for at least a half hour after completion ofwelding or cutting operations to detect and extinguish possible
31、smolderingfires.,U,nR,eg,is,te,re,d,l,l,l,l,l,l,General Requirements FirePrevention and Protection,Even if all of the special precautions have been taken,there arestill certain situations in which welding,cutting,or brazing are notallowed.,Cutting or welding shall not be permitted in:,Areas not auth
32、orized by managementBuildings with impaired sprinkler systems,The presence of explosive atmospheres(mixtures of flammablegases,vapors,liquids,or dusts with air),Locations where explosive atmospheres may develop,such as:,Inside unclean or improperly prepared tanks or equipment whichhave previously co
33、ntained such materials(flammable gasses,vapors,liquids,or dusts),Areas with an accumulation of combustible dusts.,U,nR,eg,is,te,re,d,General Requirements FirePrevention and Protection,Welding and cutting certain containers mayconstitute a special situation that requires,additional safety precautions
34、 beyond basic andspecial precautions.,No welding,cutting,or other hot work shall beperformed on used drums,barrels,tanks,or othercontainers until they have been thoroughly cleaned.,Cleaning must remove all flammable materialspresent or any substances such as greases,tars,acids,or other materials whi
35、ch might produceflammable or toxic vapors when subjected to heat.,Any pipeline or connections to the drum or vesselbeing welded shall be disconnected or blanked.,U,nR,eg,is,te,re,d,General Requirements FirePrevention and Protection,Working in confined spaces involves additional safetyprecautions bey
36、ond the basic and specialprecautions.,A confined space is defined in 29 CFR 1910.252 as arelatively small or restricted space such as a tank,boiler,pressure vessel,or small compartment of aship.,Adequate ventilation is a prerequisite to work inconfined spaces.,When welding or cutting is being perfor
37、med in anyconfined space,the gas cylinders and weldingmachines shall be left on the outside.When arc,welding is to be suspended for any substantial periodof time,such as during lunch or overnight,all,electrodes shall be removed from the holders.Theholders shall be carefully located so that accidenta
38、lcontact cannot occur and the machine shall bedisconnected from the power source.,U,nR,eg,is,te,re,d,General Requirements FirePrevention and Protection,When suspending gas welding or cutting operations,eliminate the possibility of gas escaping through thenozzle by closing the torch valves.The gas su
39、pply tothe torch must be positively shut off at some pointoutside the confined area whenever the torch is notto be used for a substantial period of time,such asduring lunch hour or overnight.Where practicable,the torch and hose shall also be removed from theconfined space.,Where welders must enter a
40、 confined space througha manhole or other small opening,means shall beprovided for quickly removing them in case of,emergency.An attendant with a pre-planned rescueprocedure shall be stationed outside to observe thewelder at all times and shall be capable of puttingrescue operations into effect.,U,n
41、R,eg,is,te,re,d,l,General Requirements Protectionof PersonnelProtection of personnel focuses on protectingthe welder from hazards other than generalfire protection.Protection of personnel inwelding or cutting operations can involve fallprotection,eye protection,and protectiveclothing.When working at
42、 heights,a welder or helperworking on platforms,scaffolds,or runwaysshall be protected against falling through theuse of:,lll,RailingsSafety beltsLife linesSome equally effective safeguards.,U,nR,eg,is,te,re,d,General Requirements Protectionof Personnel,Welding,cutting,or brazing operations conducte
43、d without proper eyeprotection create a serious eye injury hazard.,Helmets and hand shields shall be arranged to protect the face,neck,and ears from direct radiant energy from the arc.They shall be usedduring all arc welding or arc cutting operations,excluding submerged arcwelding.helpers or attenda
44、nts shall be provided with proper eyeprotection.,Helmets and hand shields shall be made of a material which is aninsulator for heat and electricity.Helmets,shields,and goggles shall notbe readily flammable and shall be capable of withstanding sterilization.,Where the work permits,the welder should b
45、e enclosed in an individualbooth or in a non-combustible screen painted with a finish of lowreflectivity such as zinc oxide(an important factor for absorbing ultra-violet radiation)and lamp black.Booths and screens shall permit,circulation of air at floor level.People adjacent to the welding areas s
46、hallbe protected from the rays by non-combustible or flameproof screens orshields or shall be required to wear appropriate goggles.,U,nR,eg,is,te,re,d,General Requirements Protectionof Personnel,Because of the danger of burns and clothing catching fire,employees exposed to the hazards created by wel
47、ding,cutting,or brazing operations shall be protected bypersonal protective equipment in accordance with therequirements of 29 CFR 1910.132.,Appropriate protective clothing required for any weldingoperation will vary with the size,nature,and location of thework to be performed.Welders should always
48、selectclothing materials which will provide maximum protectionfrom sparks and hot metal.,The shirt should have full sleeves,no pockets,and shouldbe worn outside the trousers with collar buttoned.Thetrousers should have no cuffs and should extend welldown to the safety shoes.Safety shoes and fire-res
49、istantgauntlet gloves are also needed.,U,nR,eg,is,te,re,d,l,l,l,General Requirements HealthProtections and VentilationRegardless of the precautionary measures taken,some materialsrequire special ventilation because they are particularlyhazardous.Mechanical ventilation and other specific controlmeasu
50、res are required when welding or cutting is done with thefollowing materials:Fluorine compounds,lllll,ZincLeadBerylliumCadmiumMercuryCleaning compoundsStainless steel,U,nR,eg,is,te,re,d,Oxygen-Fuel Gas Welding andCutting-IntroductionIn this Welding,Cutting,and Brazing module,three specific types of
