OXYFUEL WELDING

INTRODUCTION

• Oxyfuel welding is a welding process where the heat for fusion is supplied by a torch using oxygen and a fuel gas.

• Several different fuel gasses can be used:

FUEL GASSES Propane (LPG) Natural Gas Acetylene MAPP Hydrogen

USES Traditionally oxyfuel equipment was used for:

Brazing Fusion welding Flame hardening Metalizing Soldering Stress relieving Cutting Bending

New technologies in the GMAW process has almost eliminated the need for oxyfuel welding. Primary uses today are heating, brazing and cutting.

OXYFUEL SAFETY

The hazards of oxyfuel welding are primarily compressed gas cylinders, flammable gases and open flame.

Common concerns are : PPE (shade 4 face shield/goggles, gloves). Store and handle cylinders correctly.

Keep caps on cylinders whenever regulators are not attached. Never use oil, grease, or any hydrocarbons on fittings. Store cylinders in a locked enclosure.

Check system for leaks Follow correct procedures for turning on and off. Remove combustible materials from area.

Cutting slag can travel 35 feet on concrete Insure adequate ventilation

OXYFUEL SYSTEM Before discussing how the system works, it is important to know the name of the parts.

A. Oxygen safety discB. Oxygen cylinder valveC. Oxygen cylinder pressure

gaugeD. Oxygen working pressure

gaugeE. Oxygen regulatorF. Oxygen regulator adjusting

screwG. Acetylene cylinder safety discH. Acetylene cylinder valveI. Acetylene cylinder pressure

gauge

OXYFUEL SYSTEM--CONT.J. Acetylene working pressure gauge

K. Acetylene regulator

L. Acetylene regulator adjusting screw

M. Acetylene hose

N. Oxygen hose

O. Oxygen torch valve

P. Acetylene torch valve

Q. Torch

R. Welding tip

S. Acetylene cylinder

T. Oxygen cylinder

OXYGEN CYLINDER• One piece, seamless construction.

• Each cylinder has unique serial number and number is recorded in national registry.

• Scheduled inspection required.

• Must not be dropped.

• Should not be used as a roller.

• Never use any lubricates on threads or any part of the cylinder.

• Three common sizes are 244, 150 & 80 cubic feet.

• The valve should never be left exposed. It must always have the regulator attached or the cap on.

ACETYLENE CYLINDER

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• Acetylene cylinders are filled entirely with a porous materials which must be able to stop the propagation of an acetylene decomposition within the cylinder initiated by a backfire or an external heating of the acetylene cylinder.

• 250 psi when filled.

• Protected by fuse plugs that melt at 212 oF.• The cylinder should be opened only 1/2 to 3/4 of

a turn when in use.• The withdrawal rate in cubic feet per hour

should never exceed 1/7 times the cylinder capacity.

• Common sizes are 300, 120 and 75 cubic feet.• The cylinders must always be used, transported

and stored upright.

• Special cylinder because acetylene is unstable above 15 psi.

• Acetylene is shock sensitive.

PRESSURE REGULATORS

Gas systems must have a pressure regulator to reduce the pressure from the high pressure in the cylinder down to the working pressure.

Many different designs are used.

They range from simple fixed output, commonly used for gas grills and camping stoves,

to double stage regulators used for oxyfuel welding.

WORKING PRESSURE

Oxygen and fuel gas working pressure should be set according to manufactures recommendations for the job being performed.

Potential problems with excessive pressure. Harsh flame Damaged equipment Increased potential of flashback.

Potential problems of insufficient pressure. Insufficient heat Unstable flame Increased plugging of welding or cutting tip.

WELDING TIP SIZE Size selection chart for Victor welding tips.

Metal Thickness

Tip Size

Oxy Pressure

Acet Pressure

Acet cfh

1/6 4" 000 5 5 1 1/3 2" 00 5 5 2 3/6 4" 00 5 5 2 1/1 6" 0 5 5 3 5/6 4" 0 5 5 3 3/3 2" 1 5 5 5 1/8" 2 5 5 8

3/1 6" 3 7 7 14 1/4" 4 8 8 21 3/8" 5 9 9 31 1/2" 5 10 10 31 3/4" 6 11 11 41 1" 7 12 12 52

1- 1/4" 7 12 12 52 2" 8 12 12 65 3" 10 20 14 94 4" 12 23 15 130

Example welding tip selection and working

pressure chart.

OXYFUEL TORCH The oxyfuel torch is the handle for holding and controlling the system. It the controls the flow rate of the gasses and delivers them to the welding tip,

or cutting attachment.

AIR ACETYLENE TORCH

Burns a mixture of acetylene or MAPP and air.

As fuel gas flows through torch it draws in the correct amount of air.

Lower temperature than oxyacetylene.

Primary use is in soldering and brazing copper piping.

HOSES AND CONNECTIONS Requires special nonporous hoses. Hoses are color coded.

Green: oxygenRed or Black: fuel gas

ConnectionsOxygen: right handAcetylene: left hand

Hoses should be protected from hot metal and physical damage.

PPE• Use protection for:

• Eyes• Body

• Eyes• Correctly shaded lens--not sun glasses.• Shade 4 or 5

• Body• Fire resistant gloves• Long sleeves• Button shirt

SETTING UP OXYFUEL SYSTEM Extinguish all open flames and stop processes that produce sparks. Steps (assuming new system)

1. Secure cylinders2. Remove caps3. Crack cylinder valves4. Connect regulators5. Open cylinder valves6. Connect hoses to cylinders7. Connect hoses to torch body8. Connect welding tip to torch body9. Set working pressures10.Check system for leaks.

SHUTTING DOWN SYSTEM Close cylinder valves Open torch valves

Leave open until regulator gauges read zero.Some sources recommend doing fuel first and

oxygen last. Close torch valves Release tension on regulator adjusting screw. Roll up hoses and place torch in a safe position.