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Gas Welding Chapter 5.

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1 Gas Welding Chapter 5

2 Objectives Describe the history of oxyacetylene welding (OAW).
List and describe the properties and distribution systems for the gases used for OAW. Explain the safety issues of OAW. List the equipment used for the OAW process.

3 Oxyacetylene Welding Definition:
Join metal by heating surfaces to be joined to melting point with gas flame Fusing metal into homogeneous mass Letting it solidify into a single unit Flame in cone reaches temperatures as high as 5800º to 6300ºF Filler rod may or may not be used to intermix with molten pool

4 Oxyacetylene Process During first part of the 20th century it was used as a major welding process both for fabrication and construction, maintenance and repair Today its use is limited for industrial production purposes Still used for brazing, soldering, metalizing; welding metals with low melting points; general maintenance and repair work

5 History of Oxyacetylene Welding
Early Egyptians, Greeks, and Romans used alcohol or oil flame to fuse metals In nineteenth century various gases tested Used in laboratory in working with precious metals In 1847, Robert Hare fused platinum with oxyhydrogen flame In 1880, production of oxygen and hydrogen through electrolysis of water made distribution of gases in cylinders under pressure Late 1800s experiments done with oxygen-coal gas and air-hydrogen flames

6 Discoveries Leading to the Oxyacetylene Process
In 1836, Edmund Davey discovered acetylene gas In 1862, acetylene gas produced from calcium carbide In 1895, Thomas L. Willson produced calcium carbide commercially Used for residential lighting In 1895, LeChatelier discovered that combustion of acetylene with oxygen produced flame hotter than any other gas flame

7 Discoveries Leading to the Oxyacetylene Process
In 1900, Edmond Fouche invented high pressure acetylene torch Later designed low pressure torch (worked on injector principle) In 1906, Eugene Bourbonville brought first welding torch to this country Process first used for maintenance and repair During World War I oxyacetylene welding became production tool

8 Gases Oxyacetylene welding process uses two principal gases
Oxygen and acetylene Other gases can be used for cutting and heating Propane Natural gas Mapp® gas Stored in different size cylinders

9 Various Fuel Gas Efficiencies
Normal Btus Usable heat Flame Oxygen velocity Fuel Gas (ft3) (s/ft2) temp. per ft3 of fuel (ft/s) Acetylene , ,420ºF Mapp® , ,301ºF Propane , ,190ºF Natural gas , ,000ºF (Mpls./St.Paul) Hydrogen , ,600ºF

10 Various Gas Cylinders Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

11 Oxygen Gaseous chemical element in air
Necessary for life Most abundant chemical element in crust of Earth No color, odor, or taste Does not burn, but supports combustion Substances that do not burn in air will in oxygen

12 Oxygen Production Two commercial processes used in production of oxygen Separation of water into oxygen and hydrogen by electrolysis of water Separation of air into oxygen and nitrogen by liquefying air Commercial oxygen production

13 Oxygen Distribution Aluminum cylinders Steel cylinders
Used for medical gases (smaller size) Made of high strength 6061-T6 alloy Steel cylinders Made from single plate of high-grade steel Heat treated to develop maximum strength and hardness Seamless, drawn-steel vessels with iron neck ring shrunk on at top and cylinder value screwed into neck High pressure – undergo rigid testing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

14 Valve Mechanisms Must be opened to release oxygen
Double-seated valve perfectly tight when completely open or closed Another type of valve requires only a turn or two to open Valve protected from damage by iron cap that screws on neck ring Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15 Gas Cylinders Charged with oxygen at pressure of about 2,200 p.s.i. at 70ºF Gas temperature Increase: gas expands and increases pressure Decrease: gas contracts and reduces pressure Safety device on cylinder valve to blow off oxygen when excess pressure Occurs, oxygen lost DO NOT store where cylinder can be overheated

16 Capacity of Cylinder Three cylinder sizes used for welding and cutting
Gas suppliers fill tanks with varying amounts Large size: 220–244 cubic feet of oxygen Full: 148 to 152 pounds; Empty: 130–133 pounds Middle size: 110–122 cubic feet of oxygen Full: 89 to 101 pounds; Empty: 79–93 pounds Small size: 55–80 cubic feet of gas Full: 67 pounds; Empty: 60 pounds

17 Safety Precautions Take special care to keep oil and grease away from oxygen When using, do not place cylinders where oil might drop on them from overhead bearings Never use oxygen in pneumatic tools or to start internal combustion engines Never use oxygen to blow out pipe or hose lines, dust clothes or create head pressure in tank of any kind

18 Safety Precautions Do not store oxygen cylinders near acetylene generator, carbide, acetylene, or other fuel-gas cylinders Do not use cylinder as roller or lift it by cap Keep cylinders away from welding operation and close cylinder valve when work completed Keep cylinders away from any electrical contact

19 Acetylene Most widely used of all fuel gases
Both welding and cutting Generated as result of chemical reaction that takes place when calcium carbide comes in contact with water Tests show oxyacetylene flame temperatures up to approximately 6,300ºF Very rapid rate of preheating Burns with smoky flame, gives off carbon, has peculiar odor

20 Characteristics of an Effective Welding Fuel Gas
High flame temperature High rate of flame propagation Adequate heat content Minimum chemical reaction of flame with base and filler metal Acetylene most closely matches all these requirements and is used for welding purposes.

21 Acetylene Production and Distribution
Commercial acetylene made from calcium carbide – referred to as carbide Gray, stonelike substance Product of smelting coke and lime in electric furnace Several sizes available Distributed in standard steel drums 100 pounds for use in acetylene generators

22 Acetylene Cylinders Constructed differently from oxygen cylinders
Free acetylene should not be stored at pressure above 15 p.s.i. Safety solved by packing cylinders with porous material saturated with acetone Acetone: liquid chemical having property of dissolving or absorbing many times the volume of acetylene Strong steel container (packed completely full) Handle with care

23 Three Basic Acetylene Cylinders
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24 Valve Mechanisms Acetylene drawn off through valve
Some cylinders valve located in recessed top Others valve located on convex top Simpler in construction than oxygen valve Does not have to stand high pressure Opened only about 1-1/2 turns Can be turned off quickly in case of fire Safety fuse plugs also provided

25 Capacity of Cylinder Full cylinder of acetylene has pressure of about 225 p.s.i. Two sizes used for welding and cutting Large size contains 300 cubic feet of acetylene and weighs about 232 pounds when full Small size contains 100 cubic feet and weighs 91 pounds when full Two special sizes (10 cubic ft. and 40 cubic ft.) Not all acetylene in cylinder can be used

26 Safety Precautions Remember acetylene will burn.
Do not leave acetylene cylinders on their sides Store valve end up Store cylinders in well-protected, ventilated, dry location Away from highly combustible material or sources of heat Keep valve cap on when not in use Remember acetylene will burn. It will form explosive mixture with air.

27 Safety Precautions Handle acetylene cylinders carefully
Use warm (not boiling) water on the valve if it becomes clogged with ice (Never a flame!) Fusible safety plugs melt at boiling point of water Handle acetylene cylinders carefully Damages could cause leakage Advise supplier immediately if acetylene leaks around valve spindle when valve opened Close spindle and move cylinder to outside area Never tamper with fuse plugs

28 Propane Gas Hydrocarbon present in petroleum and natural gas
Used primarily for oxyfuel heating, cutting, soldering and brazing Sold and transported in steel cylinders containing from 20 to 100 pounds of liquefied gas Also supplied by tank car and bulk delivery Oxypropane flame temp less than oxyacetylene Takes longer to bring steel to melting point Used for soldering and alloy brazing

29 Mapp® Gas Liquefied acetylene compound
Fuel gas for oxyfuel heating and cutting Strong smell (aid in discovering leaks) Mixed with oxygen, flame is 5,301ºF Heating and cutting somewhat slower Lower temperature Overall expenses lower due to reduced handling costs and lower gas costs

30 Mapp® Gas Use as fuel gas for heating and cutting is growing
Distributed in bulk or steel cylinders Shutoff valve similar to ones on acetylene cylinder Liquefied and stabilized so can be used at pressures as high as 375 p.s.i. at 170ºF Explosive limits lower than acetylene Can be stored in free state and at high pressures

31 Safety in Handling Mapp® Gas
Forms an explosive mixture with air Same general precautions used with handling acetylene cylinders should be observed Safest of industrial fuels Explosive limits of Mapp® gas vapor in air and oxygen much narrower than acetylene, same as propane and natural gas Can smell it at concentrations as low as 0.01%

32 General Cylinder Handling, Storage, and Operation Safety
Regulations 1. All portable cylinders used for the storage and shipment of compressed gases shall be constructed and maintained in accordance with the regulations of the U.S. Department of Transportation, 49 CFR Parts 171– Compressed gas cylinders shall be equipped with connections complying with the American National Standard Compressed Gas Cylinder Valve Outlet and Inlet Connections, ANSI B

33 Regulations General Cylinder Handling, Storage, and Operation Safety
3. Compressed gas cylinders shall be legibly marked, for the purpose of identifying the gas content, with either the chemical or the trade name of the gas. Such marking shall be by means of stenciling, stamping, or labeling and shall not be readily removable. Whenever practical, the marking shall be located on the shoulder of the cylinder. This method conforms to the American National Standard Method for Marking Portable Compressed Gas Containers to Identify the Material Contained, ANSI Z

34 Regulations General Cylinder Handling, Storage, and Operation Safety
4. All cylinders with a water weight capacity of over 30 pounds (13.6 kilograms) shall be equipped with means of connecting a valve protection cap or with a collar or recess to protect the valve. 5. Cylinders shall be kept away from radiators and other sources of heat.

35 Regulations General Cylinder Handling, Storage, and Operation Safety
6. Inside of buildings, cylinders shall be stored in a well-protected, well-ventilated, dry location, at least 20 feet from highly combustible materials such as oil or excelsior. Cylinders should be stored in clearly identified assigned places away from elevators, stairs, or gangways. Assigned storage spaces shall be located where cylinders will not be knocked over or damaged by passing or falling objects, or subject to tampering by unauthorized persons. Cylinders shall not be kept in unventilated enclosures such as lockers and cupboards. 7. The valves on empty cylinders shall be closed.

36 Regulations General Cylinder Handling, Storage, and Operation Safety
8. For cylinders designed to accept a valve protection cap, the cap shall always be in place, hand-tight, except when cylinders are in use or connected for use. 9. For fuel-gas cylinder storage inside a building, cylinders, except those in actual use or attached ready for use, shall be limited to a total gas capacity of 2,000 cubic feet or 300 pounds of liquefied petroleum gas. 10. Oxygen cylinders shall not be stored near highly combustible material, especially oil and grease, or near acetylene or other fuel-gas cylinders, or near any other substance likely to cause or accelerate fire.

37 Regulations General Cylinder Handling, Storage, and Operation Safety
11. Oxygen cylinders in storage shall be separated from fuel-gas cylinders or combustible materials (especially oil or grease), a minimum distance of 20 feet or by a noncombustible barrier at least 5 feet high having a fire-resistance rating of at least one-half hour. 12. Cylinders, cylinder valves, couplings, regulators, hoses, and apparatus shall be kept free from oily or greasy substances. Oxygen cylinders or apparatus shall not be handled with oily hands or gloves. A jet of oxygen must never be permitted to strike an oily surface, greasy clothes, or enter a fuel oil or other storage tank.

38 Regulations General Cylinder Handling, Storage, and Operation Safety
13. A cradle, boat, or suitable platform shall be used when transporting cylinders by a crane or derrick. Slings or electric magnets shall not be used for this purpose. Valve-protection caps shall always be in place on cylinders designed to accept a cap. 14. Cylinders shall not be dropped, roughly handled, or struck or permitted to strike each other violently. Rough handling, knocks, or falls are liable to damage the cylinder, the valve, or the safety devices and cause leakage.

39 General Cylinder Handling, Storage, and Operation Safety
Regulations 15. Cylinder valves shall be closed before cylinders are moved. 16. Cylinder valves shall be closed when work is finished. 17. Valve-protection caps shall not be used for lifting cylinders from one vertical position to another. Bars shall not be used under valves or valve-protection caps to pry cylinders loose when frozen to the ground or otherwise fixed; the use of warm (not boiling) water is recommended. Valve-protection caps are designed to protect cylinder valves from damage.

40 Regulations General Cylinder Handling, Storage, and Operation Safety
18. Unless cylinders are secured on a special truck, regulators shall be removed and valve-protection caps, when provided for, shall be put in place before cylinders are moved. 19. Cylinders shall never be used as rollers or supports, whether full or empty. 20. Cylinders not having fixed hand wheels shall have keys, handles, or nonadjustable wrenches on valve stems while these cylinders are in service. In multiple-cylinder installations only one key or handle is required for each manifold.

41 Regulations General Cylinder Handling, Storage, and Operation Safety
21. Cylinders shall be kept far enough away from the actual welding or cutting operation so that sparks, hot dross, or flame will not reach them, or fire-resistant shields shall be provided. 22. The numbers and markings stamped into cylinders shall not be tampered with. 23. No one shall tamper with safety devices on cylinders or valves.

42 Regulations General Cylinder Handling, Storage, and Operation Safety
24. Cylinders shall not be placed where they might become part of an electric circuit. Contacts with third rails, trolley wires, or the like shall be avoided. Cylinders shall be kept away from radiators, piping systems, and layout tables that may be used for grounding electric circuits, such as for arc welding machines. Any practice such as the tapping of an electrode against a cylinder to strike an arc shall be prohibited. 25. No person, other than the gas supplier, shall attempt to mix gases in a cylinder. No one, except the owner of the cylinder or person authorized by the owner, shall refill a cylinder.

43 Regulations General Cylinder Handling, Storage, and Operation Safety
26. A hammer or wrench shall not be used to open cylinder valves. If valves cannot be opened by hand, the supplier shall be notified. 27. Cylinder valves shall not be tampered with nor should any attempt be made to repair them. If trouble is experienced, the supplier should be sent a report promptly, indicating the character of the trouble and the cylinder’s serial number. Supplier’s instructions as to its disposition shall be followed.

44 Regulations General Cylinder Handling, Storage, and Operation Safety
28. Fuel-gas cylinders shall be placed with valve end up whenever they are in use. Liquefied gases shall be stored and shipped with the valve end up. 29. Safety devices shall not be tampered with.

45 General Cylinder Handling, Storage, and Operation Safety
Regulations 30. Before connecting a regulator to a cylinder valve, the valve shall be opened slightly and closed immediately. The valve shall be opened while standing to one side of the outlet; never in front of it. Never crack a fuel-gas cylinder valve near other welding work or near sparks, flame, or other possible sources of ignition. 31. Before a regulator is removed from a cylinder valve, the cylinder valve shall be closed and the gas released from the regulator.

46 General Cylinder Handling, Storage, and Operation Safety
Regulations 32. Nothing that may damage the safety device or interfere with the quick closing of the valve shall be placed on top of an acetylene cylinder when it is in use. 33. If cylinder valves or fittings are found to have leaks that cannot be stopped by closing the valve or fitting, the cylinders shall be plainly tagged and taken outdoors away from sources of ignition. A sign should be placed near the leaky cylinders warning unauthorized personnel not to approach them. The supplier should be promptly notified, and the supplier’s instructions for the return of the cylinders followed.

47 Manifold Distribution
Supplies both oxygen and fuel gas to number of work stations Acetylene manifolds must be equipped with flash arrester to prevent flashback through manifold into cylinders Each cylinder connected to manifold by means of an individual pigtail flash arrester and backcheck valves

48 A typical station outlet for both oxygen and acetylene pipelines from the source.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

49 Thermadyne Industries, Inc.
Manifold Regulator Reduces pressure to 50 or 75 pounds in line that goes to station outlets in shop Full pressure of 2,000 p.s.i. in oxygen manifold pipes Work station also equipped with acetylene and oxygen regulator for further pressure control Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

50 Oxygen Manifold Installation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

51 Thermadyne Industries, Inc./Victor Equipment Company
Manifold Systems Piping Acetylene: should be steel or wrought iron Oxygen: can use copper Range from very simplistic to highly sophisticated automatic systems For virtually any gas control requirement Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc./Victor Equipment Company

52 Acetylene Cylinder Manifold System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

53 Acetylene Generators Two general types
Calcium carbide dropped into water Water allowed to drip on carbide Carbide-to-water generators used to produce acetylene gas for welding and cutting Water absorbs heat given off by chemical reaction Gas purified by bubbling through water

54 Acetylene Generator Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Rexarc

55 Acetylene Generators Two classes of generators
Low pressure (less than 1 p.s.i.) Medium pressure (1 to 15 p.s.i.) Generating capacities range from 30 cubic feet of acetylene per hour for small portable 6,000 cubic feet acetylene per hour for medium-pressure generator

56 Required Oxyacetylene Welding Equipment
Oxygen regulator Acetylene regulator Oxygen welding hose Acetylene welding hose Hose couplings Single-purpose cutting torch or welding torch Cylinders and cart for portability Flash arrestor and check valves (protective equipment) Flint lighter to ignite torch

57 Approved Protective Equipment
Installed in OAW system to prevent: Backflow of oxygen into fuel-gas supply system Passage of flashback into fuel-gas supply system Excessive back pressure of oxygen in fuel-gas supply system

58 Protective Equipment Functions may be combined in one device or provided by separate devices Located in main supply line, head of each branch line in manifold system, or at each location where fuel gas withdrawn Backflow protection should be provided to prevent fuel gases from flowing into oxygen system Flashback protection should be provided to prevent flame from passing into fuel-gas system

59 Equipment Setup for Welding
Portable tank outfits are mounted on a truck. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

60 Pressure Regulators Reduce high cylinder pressure to relatively low pressure of 0 to 45 p.s.i. used for welding Maintain pressure without variation during welding Flame remains steady and uniform Two pressure gauges mounted on body of regulator One shows pressure in cylinder, other pressure of gas being supplied to torch

61 Thermadyne Industries, Inc.
Pressure Regulators Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

62 Thermadyne Industries, Inc.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 5-23 Thermadyne Industries, Inc. The working pressure is adjusted by means of a hand screw. When this screw is turned to the left, or counterclockwise, the valve mechanism inside the regulator is shut off, and gas cannot pass through the regulator to the torch. Turning the pressure-adjusting screw to the right, or clockwise, presses it against the regulator mechanism. The valve opens, and gas passes through the regulator to the torch at the pressure shown on the working pressure gauge. Any pressure can be set up by turning the handle until the desired pressure is indicated.

63 Safety Precautions Inspect all nuts and connections for leaks
Before opening valve of cylinder to which regulator has been attached, check pressure adjusting screw is completely released Never attempt to connect acetylene regulator to cylinder containing oxygen or vice versa Do not force connections, and check if tight Use regulators only for gas and pressures they are intended Have regulators repaired only by skilled trained mechanics

64 Regulator Construction
Internal mechanism of oxygen regulator Oxygen enters regulator at left at 2,200 p.s.i. and must leave regulator at desired pressure for welding – 10 p.s.i. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

65 Regulator Construction
Force that opens valve provided by tension of spring Force that closes valve provided by high gas pressure from tank When two forces balanced, constant flow of oxygen to torch results Designated as single-stage and two-stage Single-stage regulators used with manifold systems

66 Three Typical Regulator Designs
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

67 Line Regulator Regulator springs made of good grade of spring steel
Diaphragm of brass, sheet spring steel, stainless steel or rubber Individual oxygen and acetylene regulators required at each station when serviced by line gas system Smaller than cylinder regulators Not subject to high cylinder pressure

68 Difference in Internal Construction of a Tank and a Line Regulator
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

69 Welding Torches Apparatus for mixing oxygen and acetylene in proportions to carry on welding operation Provides handle so welder can hold and direct the flame Two inlet gas connections: oxygen and acetylene Valve controls volume of gas passing through Wide range of welding tip sizes

70 Two Types of Oxyacetylene Welding Torches
Injector Acetylene carried through torch and tip at low pressure by suction force Higher oxygen pressure passing through small orifice of injector nozzle Mixing head and injector integral part of tip Equal (balanced-pressure) Both gases delivered at equal pressures Mixing head separate replaceable unit in body of torch

71 Injector Torch Linde Division, Union Carbide Corp. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The acetylene is carried through the torch and tip at low pressure by the suction force of the higher oxygen pressure passing through the small orifice of the injector nozzle.

72 Balanced-pressure Type Mixer
The two gases are fed in at points (1) fuel gas and (2) oxygen. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The gases are mixed, beginning at point (3), throughout the mixing chamber.

73 Injector Type Mixer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The oxygen passing through the Venturi (1), aspirates the fuel gas available in chamber (2). The gases are mixed, beginning at point (3), throughout the mixing chamber.

74 Equal-pressure (Balanced-pressure) Torch
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

75 Self-contained System
Lightweight portable type work – requires no outside source of power Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc./Victor Equipment Company

76 Torch Tips Size measured by diameter of end opening
Marked on side of tip Most common system: numbers from 000–15 Larger the number, larger hole in tip and greater volume of heat provided Tips for injector torches provided with individual mixers so mixer and tip one unit Most made of pure drawn copper Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

77 Safety Precautions Do not remove tip with pliers (manufacturers wrench should be used at all times) Never insert or remove tip while tip tube hot Keep orifice at end of tip clean at all times Clean with tip cleaners Do not use tip as hammer Protect seat of the tip Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ©David A. Tietz/Editorial Image, LLC.

78 Gas Economizer Provides place to hang torch – safety issue
Eliminates need of constantly relighting torch and readjusting flame Saves gas Has pilot light Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gases shut off automatically, when the lighted torch is hung on the hook. When torch is taken off hook and passed over pilot light, the gases turn on and torch relights to previous flame setting. Equipped with pilot light and has passages through which oxygen and acetylene pass before entering torch ©David A. Tietz/Editorial Image, LLC.

79 Oxygen and Acetylene Hose
Especially manufactured for purpose Strong to resist internal wear Flexible so it does not interfere with welder’s movement Abe to withstand abrasive wear on job Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ©David A. Tietz/Editorial Image, LLC.

80 Hose Construction Three layers of construction
Inner lining of high grade gum rubber Middle layer of rubber-impregnated fabric Outside layer made of colored vulcanized rubber Plain or ribbed Color used for identification Green for oxygen Red for acetylene Black for inert gas and air

81 Hose Size Different sizes for different types of welding and cutting operations Depends on amount of gas required, length of hose used, and pressures needed Sizes available: 3/16, 1/4, 3/8, and 1/2 inch 3/16 I.D. (inside diameter) hose very flexible, and light; used for light welding 1/2 I.D. used for heavy cutting Can be single or double Double actually two pieces joined by web

82 Thermadyne Industries, Inc.
Hose Connections Standard hose connection Nipple inserted in end of hose Nut that attaches nipple to torch or regulator Threading prevents attaching wrong head to wrong regulator Oxygen coupling has right-hand thread Acetylene coupling has left-hand thread Nuts marked STD. OXY for oxygen and STD. ACET for acetylene Clamps or ferrules connect hose tightly to nipple to ensure leakproof connection Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

83 Care of Hose Always use hose to carry only one kind of gas
Test hose for leaks frequently by immersing hose at normal working pressure under water Clamp all hose connections or fasten them securely to withstand pressure of 300 p.s.i. without leakage Repair or replace all hose showing leaks, burns, worn places, or other defects

84 Care of Hose Do not attempt to repair hose with tape
Handle hose carefully when welding Avoid dragging on greasy floor Avoid contact with flame or hot metal Protect from falling articles or being stepped on Should not be kinked sharply Roll up hose and hang it out of the way at the end of day or job

85 Thermadyne Industries, Inc.
Lighters Use friction spark lighter to light welding torch Flints easily replaced at small cost Safety note: Never use matches Puts welder’s hand too close to torch tip where it may be burned when gases ignite Never carry matches in pockets May ignite during welding Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

86 Filler Rod Most gas welding done with filler rod
Provides additional metal to form larger weld bead Many diameters, available in bundles of 50 or 100 pounds and boxes up to 300 pounds net weight 36 inches long Steel rods copper coated to prevent rusting Some aluminum rods flux coated Both steel and aluminum 28 inches long

87 American Welding Society
Set up AWS classification numbers for steel gas-welding rods RG-65, RG-60 and RG-45 R indicates welding rod and G indicates gas welding Numbers designate approximate tensile strength of weld metal (thousand pound per square inch) Example: RG-60 is welding rod with tensile strength of approximately 60,000 p.s.i.

88 Gas Rod Characteristics
Produce welds of varying tensile strengths depending upon nature of base metal Welds made on alloy steels produce weld composition between base metal and filler metal Can be used in all positions Limited only by skill of welder

89 Class RG-65 Gas Welding Rod
Low alloy steel composition Used to weld sheet, plate, tubes and pipes of carbon and low alloy steels Produce welds in range of 65,000 to 75,000 p.s.i.

90 Class RG-60 Gas Welding Rod
Low alloy composition Used to weld carbon steel pipes for power plants, process piping, and other severe service condition Produce welds in range of 50,000 to 65,000 p.s.i. Used extensively as general-purpose rod Highly satisfactory welds in carbon steels, low alloy steels and wrought iron

91 Class RG-45 Gas Welding Rod
General-purpose welding rods Low carbon steel composition Used to weld mild steels and wrought iron Produce welds in range of 40,000 to 50,000 p.s.i.

92 Fluxes Cleaning agent used to dissolve oxides, release gases, and slag and cleanse metal surfaces for welding, soldering, and brazing Function of flux Combine with oxides to form fusible slag having melting point lower than metal Flows away from weld area No one flux satisfactory for all metals

93 Fluxes Melting point of flux must be lower than either metal or oxides formed Available as dry powders, pastes, thick solutions, and coatings on filler rod Differ in composition and way they work according to metals with which they are used

94 Oxyhydrogen Welding (OHW)
Form of gas welding once used extensively Today have limited use Flame produced by burning two volumes of hydrogen with one volume of oxygen Temperature of ~ 4,100ºF Almost invisible Similar equipment to that used for oxyacetylene welding Need regulator specifically designed for hydrogen

95 Oxyhydrogen Welding (OHW)
Relatively low flame temperature Used principally in welding metals with low melting points Used extensively in welding of lead Thicknesses of lead up to 1/4 or 3/8 inch No deposit of carbon

96 Fuel Gases Propane, butane, city gas, and natural gas
Can use standard oxyacetylene welding equipment Need special fuel gas regulator Variety of suitable heating and cutting tips available Not suitable for welding ferrous materials Oxidizing nature of flame and relatively low flame temperature Used extensively for manual and mechanized brazing and soldering operations

97 Air-Acetylene Welding (AAW)
Air 4/5 nitrogen by volume Neither fuel gas nor supporter of combustion With acetylene gives lower flame temperatures Total heat content also lowered Torches designed to draw in proper quantity or air from atmosphere Acetylene flows through torch 2 to 15 p.s.i. Supplied from small cylinder Applications: plumbing and electrical industry

98 Supporting Equipment Welding table with either
Cast iron top, slotted to permit use of hold-down clamps Firebrick top Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

99 Supporting Equipment C-clamps, carpenter clamps, straightedges, metal blocks, steel square Grinders, air-chisels, files, hand chisels Cutting torch, gas or electric, for beveling Carbon, in form of rods, plates, or paste Preheating equipment, material to provide for slow cooling Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. North American Manufacturing Co.

100 Supporting Equipment Wire power brush for cleaning scale and slag
Some jobs may need no finishing of any kind Others require filing, grinding, drilling, or even considerable machining

101 Thermadyne Industries, Inc.
Safety Equipment Welding and Cutting Goggles Welders must wear specially designed goggles Protect eyes from infrared and ultraviolet rays, heat, flying sparks, and particles of hot metal Filter lenses make of special optical glass Various diameters and tinted green or brown Filter out harmful rays Minimize effect of glare Light, medium, dark shades Table 5-3 in text Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

102 Safety Equipment Welding and Cutting Goggles
Outer lens clear glass or plastic 3/64 to 1/16 inch thick Light in weight and fit face Eye shields For welding with electric arc Have clear cover lens and colored filter lens Provide wide range of vision and can be used over eyeglasses Not recommended for welding or cutting No protection from the sides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc.

103 Safety Equipment Protective Clothing and Gloves
Hazards Sparks, molten bits of metal and hot scale Protect body by apron, shop coat, or coveralls that resist fire High-top shoes and hard hats Gloves Made from nonflammable material Light welding – ordinary canvas glove with cuff Keep free from grease and oil

104 Safety Equipment Check Valves
Permit forward flow of gas and closes when gas begins to flow in reverse direction One required for acetylene hose and one for oxygen hose May be attached to torch or to regulators Reverse flow can be caused by blocked torch tip, excess gas or oxygen pressure, lack of pressure or unsafe start-up or shut-down

105 Flashback Arrestors Generally made of sintered metal alloy
Prevents flame from moving upstream of arrestor Does not protect torch or tip Neither does check valve Best way to assure that accidents don’t happen is to follow all safety operating procedures.

106 Internal View of a Check Valve
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Prevents the reverse flow of gases Thermadyne Industries, Inc./ Victor Equipment Company

107 Internal View of a Flashback Arrestor
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thermadyne Industries, Inc./ Victor Equipment Company

108 General Safety Operating Procedures
Protective equipment, hose, and regulators: Equipment installed and used only in service for which approved and recommended by manufacturer. Approved protective equipment installed in fuel-gas piping. Hose for oxy-fuel gas service shall comply with Specification for Rubber Welding Hose, 1958, Compressed Gas Association and Rubber Manufacturers Association.

109 General Safety Operating Procedures
When parallel lengths of oxygen and acetylene hose taped together, not more than 4 out of 12 inches shall be covered by tape. Hose connections shall comply with Standard Hose Connection Specifications, 1957, Compressed Gas Association. Hose connections shall be clamped so they can withstand twice the pressure without leakage (oil-free air or inert gas used for test).

110 General Safety Operating Procedures
Hose showing leaks, burns, worn places, or other defects rendering it unfit for service shall be repaired or replaced. Pressure-reducing regulators shall be used only for gas and pressures for which they are intended. Use skilled mechanics who have been properly instructed to repair regulators or parts of regulators that need repair.

111 General Safety Operating Procedures
Gauges on oxygen regulators shall be marked Use No Oil. Union nuts and connections on regulators shall be inspected before use to detect faulty seats that may leak gas when regulators attached to cylinder valves.


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