Welding & Cutting Guide€¦ · required for using the gas welding, cutting and heating equipment supplied in this BOC kit. BOC has accumulated extensive knowledge in the design and

BOC products perform with reliability and the backing of Australia’s leading welding supplier

Welding & Cutting Guide

Welding & Cutting Guide Page 2BOC Product Range Training Manual

Introduction

This guide provides the basic knowledgerequired for using the gas welding, cutting andheating equipment supplied in this BOC kit.

BOC has accumulated extensive knowledge inthe design and manufacture of gas equipmentfor over 100 years. Our involvement in thegases industry dates back to 1886.

Access to a wealth of experience and technicalinformation, built-up over the years makes theBOC range of gas equipment a world leader.

BOC Gas equipment and technical support isavailable through our national BOC CustomerService Centre on 131262 and at any of our 70Gas and Gear Centres.

Information in this catalogue is subject to error, omission or change without notice.

Contents


Protect yourself and others; read and understand the precautions in this guide.They are for your personal safety and the safety of people near the equipment

Safety ...................................................4ResponsibilitiesPrecautionsProtection

Gases Safety ....................................5OxygenAcetyleneLP-GasCare of cylinders

Setting Up.........................................6Commencing weldingOxy-Handigas

Putting Equipment.....................7into Service

Commencing Welding ...............8Lighting upBackfire & flashbacksDismantling

Cutting Attachment...................9Using the cutting attachmentClosing down the cutting attachment

Welding............................................10Welding of steelBraze weldingBrazingSilver brazing

Heating & Cutting ....................11Heating with Oxy-AcetyleneHeating with Oxy-LP-GasCutting steelCutting accessories

Cutting, Cleaning.......................12& HardeningGeneral cuttingPiercing holesFlame gougingFlame cleaningFlame spallingHard facingFlame hardening

Care & Maintenance................13Welding tips & cutting nozzlesCutting attachmentsRegulatorsHoses

Cutting Tables .............................14

Filler Rod & Flux .......................15Reference Table


BOC’s ProMaster, Master andMasterStart kits, in conjunction withcylinders of oxygen and acetylene, providea comprehensive set of metalwork tools.This plant will provide:• Sufficient concentrated heat to melt

steel and other metals to weld surfacestogether.

• A pressurised jet of oxygen to cut steel.• With special tips and nozzles the

versatility to allow heating, brazing,flame cleaning and gouging of surfaces.

Proficiency in the process dependsupon the ability of the operator tocontrol movement of the blowpipe andfiller rod to produce good-quality welds, and a steady hand for smoothflame cutting.

YOUR RESPONSIBILITYYour responsibility is to thoroughly readthis manual. Do not attempt to operatethe gas equipment unless you are familiarwith the operating principles and safepractices outlined in this manual.Careless operation and not followingthe safety precautions may result in fire,explosion, and damage to theequipment and injury to the operator.

COMBUSTIONCombustion requires:• Fuel • Oxygen • IgnitionFuel Gases readily ignite in air and in anenclosed vessel could explode if heated.Oxygen does not burn but supportsand accelerates combustion. In thepresence of high pressure oxygen mostmaterials, including metals, will burn.Ignition can occur from obvioussources like open flames and electricsparks. If high-pressure oxygen is

suddenly released into a regulator,enough heat can be generated to burnout the regulator valve seat.Cylinder valves should always beopened slowly to lessen the shock on theregulator valve seat and pressure gauges.In BOC Gas Equipment design, specialcare is taken to select materialscompatible with the gases and with highresistance to ignition.Oxygen and non-flammable gases haveright-hand threaded fittings while fuelgases have left-hand. For ease ofidentification left-hand threaded fittingshave notches in the corners of thehexagon.

BEFORE YOU START:WORK AREA• Fire-proof floor – dirt, concrete or

wooden covered in sand or wet downis acceptable.

• Protect walls and nearby combustiblesfrom flying hot metal sparks and slagproduced by cutting – use metal orcement sheets.

• Oxygen causes oil and grease to burnviolently – keep away from all oxygenequipment.

• Have adequate ventilation to dissipatefumes.

• A firebrick top workbench isrecommended.

• Cylinders must be secured in a trolleyor to a wall.

PERSONAL PROTECTION• Clothing with long sleeves and a snug

fit at wrists, long pants and leatherboots should be worn. Woollenclothing is preferred to cotton becauseit does not readily ignite. Nylon andsynthetic clothing and open shoesshould not be worn. Leather gloves,apron, spats and welders cap will helpprotect from sparks and spatter.

EYE PROTECTIONThe oxy-acetylene flame produces anintense bright light which causesdiscomfort and possible injury to the eyes.In order to comfortably and safely seethe flame when welding or cutting,welding goggles must be worn.Different lenses are recommended forthe various processes:Shade 4• Oxy-cutting and gouging.• Flame descaling.• Braze welding of light copper and steel.• Silver brazing.

Shade 5• Fusion welding of steel, cast iron,

nickel and copper.• Braze welding of heavy steel and

cast iron.• Hardfacing.Shade 6• Fusion and braze welding of cast iron

and steel castings.

FIRE PROTECTION• Do not work near oil and grease

containers, flammable vapours orcombustible dust.

• Move all combustibles at least 10 maway from the work site. Otherwiseprotect with flame proofed covers.

• Have a fire extinguisher or water andsand available.

• After welding/cutting is completed,carefully inspect for sparks andsmouldering material before leaving the area.

SPECIAL WARNINGSNever weld, heat or cut on containersthat have held flammable substancesuntil they have been thoroughly steamcleaned. Flammable vapours mayexplode. Even after cleaning, thecontainers should be filled with waterbefore welding or cutting. Make surethe space above the water is vented forescape of heated air.Do not weld or cut painted, platedor coated parts unless special precau-tions have been taken with ventilation.Toxic fumes may be given off.

Safety

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Gases Safety


THE GASES USEDOxygen (black cylinder) is compressedto 17,500 kPa. The pressure in thecylinder is directly related to thequantity of gas stored. If pressure fallsto half, then half the contents remains.• If cylinder pressure rises as a result of

fire a bursting disc safety device willfracture before the increased cylinderpressure can rupture the cylinder.

• Oxygen under pressure acceleratescombustion.

• Oil, grease and rust will igniteviolently in oxygen and must not bepermitted to contaminate oxygenconnections or equipment.

Acetylene (maroon cylinder) is ahighly flammable gas in both air andoxygen. The cylinder is filled with aporous mass and acetone. The acetylenegas is dissolved in the acetone hence thename dissolved acetylene or ‘DA’. Thisallows acetylene to be stored safely upto 1800 kPa.• Acetylene reacts with copper to form

unstable copper acetylides, so purecopper must not be used withacetylene under pressure. Copperwelding tips and nozzles are OKbecause the oxy-acetylene mixture isdownstream of the mixer.

• DA cylinders have fusible plugs in theneck ring; these will melt in the eventof a fire.

• Acetylene is lighter than air so leakedacetylene will dissipate.

• The oxy-acetylene flame at 3100°C isthe hottest flame available for weldingmild steel.

• High pressure acetylene gas isunstable. The maximum pressureoutside the cylinder is restricted to150 kPa.

• Tips and nozzles for acetylene arestamped ‘A’.

LP-Gas (Handigas silver cylinder)Liquefied Petroleum Gas is a flammablegas stored as liquid in the cylinder. Thepressure is less than 1000 kPa.• LP-Gas cylinders have a spring loaded

safety device that releases gas in theevent of the cylinder being overheatedor overfilled.

• Heavier than air so LP-Gas leaks flowinto low-lying recesses and will remainfor a considerable time.

• Accumulated gas can ignite andexplode. An odourant is added to givean unpleasant smell as a warning tocheck for leaks and avoid sources ofignition.

• The oxy-LP-Gas flame is not suitablefor welding steel, but is for heating,brazing and cutting of steel.

• Mixer, tips and nozzles for use withLP-Gas are stamped ‘P’ (Propane)and must not be used with acetylene.

CARE OF CYLINDERS• Cylinders must be handled carefully

as they contain gas compressed at highpressure.

• A pressure-reducing valve or regulatormust be used to reduce cylinderpressure to operating pressure.

• Always open cylinder valves slowly,two full turns is sufficient, and tightlyclose after use.

• Gas pressure increases as temperaturerises so cylinders must be kept awayfrom sources of heat.

• Cylinders have safety devices to ventpressure build-up in excess of safeoperating conditions.

• Cylinders must be stored and used inthe upright position – oxygen, DA andLP-Gas.

• If for any reason the cylinder valve orsafety device starts to vent, if possibletake the cylinder outside and awayfrom ignition sources, where the gasmay dissipate. Promptly report theincident to BOC.

• If an acetylene cylinder becomes hot,close the cylinder valve and clear allpersonnel from the area. From aprotected position, cool the cylinderwith water until the cylinder is cool –revealed by the water not drying-off.Notify the fire brigade and BOC.

NOTE: If the acetylene or LP-Gas isburning and no secondary damage isbeing caused, do not extinguish theflame – this prevents the spread ofunburned gas. Use water to cool thecylinder from a safe position.• A leaking cylinder creates an

atmosphere of concentrated gas thatwill cause a fire hazard unless there isadequate ventilation. A cloud ofoxygen will accelerate any fire and acloud of fuel gas (acetylene or LP- Gas)may explode.

Oxy-Handigas permits brazing, heating,cutting and gouging but not welding.


Setting UpTO COMMENCE WELDING & CUTTINGIn addition to the BOC kit, thefollowing are required:• Oxygen cylinder• Acetylene cylinder• Trolley• Leather gloves• Welding filler rods• Welding flux

The BOC ProMaster contains:1. Welding blowpipe handle2. Welding mixer – W3.Welding tips – sizes:

W(6), 8, 10, 12, 15, 20, (26)4. Cutting attachment5. Cutting nozzles – sizes:

C-A, 8, 12, 15, 20, (24, 32)6. Heating tip – size HTW-A1 & barrel7. Flashback arrestors – oxygen and

acetylene to fit blowpipe inlets8. Combination spanner9. Flint lighter10.Twin hose with fittings oxygen

(BLUE), acetylene (RED)11. Tip and nozzle cleaners12. Oxygen 8000 regulator – 1000 kPa

maximum13. Acetylene 8000 regulator – 150 kPa

maximum14. Welding goggles15. BOC Welding & Cutting manual16.Toolbox and lift-out tray with

snap-in recessesSizes ( ) not included in ProMaster –available as extra items see chart below.The BOC Master and MasterStartoutfits contain fewer tips and nozzlesbut the toolbox tray has spare recessesfor the extra items.

OXY-HANDIGASThe following items are necessary forcutting and heating with oxy-Handigas.• LP-Gas regulator – 400 kPa

maximum.• Cutting nozzles – sizes:

C-P, 8, 12, 15, 20, 24, 32.• Tips and mixer – W for brazing.• Heating mixer – HT or HTP.• Heating tips – sizes:

HT-PI, HT-P2, HTP-P3, HTP-P4.It is recommended LP-Gas compatiblehose be used – colour coded orange.

WARNING:LP-Gas regulator, mixer, tips and nozzles must not be used withacetylene.

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PUTTING THE EQUIPMENT INTOSERVICE1. Ensure your hands and gloves are

free of grease, oil and flammablesolvents.

2. Inspect both cylinder valve outlets fordamage and freedom from dirt, oiland grease. If required wipe with aclean lint-free cloth.

3.Wearing eye and ear protection,momentarily open and close theoxygen cylinder valve to blow outdust – ‘cracking the valve’. Repeat forfuel gas valve – the area must be wellventilated and away from open flamesand other ignition sources.

4. Remove the plastic protective capfrom the oxygen regulator inlet.Inspect the connection threads ando-rings for damage and freedom fromoil and grease. Attach the regulator tocylinder valve by hand, then tighten(right-hand thread) with the spanner.

5. Ensure regulator valve is fully closedby backing off the knob (anti-clockwise) until the screw is loose.

6. Open the cylinder valve slowly, twofull turns is sufficient. The inletpressure gauge (on right-hand side)pointer moves slowly to a maximumreading. Do not stand directly infront of or behind the regulator whenopening the cylinder valve.

7. Check for leakage by closing thecylinder valve. If the pressure gaugepointer drops there is a leak at theinlet connection – retighten.

8. Repeat previous steps with theacetylene regulator – left-hand thread.

9. Connect the blue hose to the outlet ofthe oxygen regulator and the red hoseto the outlet of the acetylene regulator.Tighten fittings with spanner.

10. Separately for each gas, purge dustfrom the hose by screwing theregulator knob in to open theregulator valve. Back off knob toclose regulator seat. Ensure no openflames are nearby.

11. If included, connect the flashbackarrestors to the BOC blowpipeinlets and tighten with spanner.

12. Connect the blue hose to theoxygen flashback arrestor and thered hose to the fuel flashbackarrestor and tighten. If flashbackarrestors are not included couplethe hoses to the O and F blowpipeinlets.

13.With the blowpipe valves closed,turn regulator knob clockwisesetting each regulator to about 50 kPa.

14. Check for oxygen leaks by closingthe oxygen cylinder valve. If thereare no leaks the 50 kPa set willremain steady. If there is a pressuredrop search for the leak using aleak-detecting solution applied to allconnections. A soft or liquid soapin water applied to the connectionswill reveal most leaks.

15. Repeat 14 for the fuel gas regulatorand connections.

16. Inspect the welding mixer to seethat both o-rings are present andthey are free from dust and othercontaminants. Insert the mixer intothe blowpipe by a combination ofpushing and twisting. Hand tightenthe mixer nut until the mixer teeth lock.

17. Select the welding tip appropriate tothe work as specified in Table 1.Firmly hand tighten the tip in themixer. Release the mixer nut toallow the tip to be rotated to thedesired position. Retighten themixer nut.

Putting the Equipment into Service



Commencing WeldingTO COMMENCE WELDING1. Set the specified operating pressure

on each regulator (Table 1) In theWELD zone (50 – 100 kPa) for oxy-acetylene welding.

2. Purge the blowpipe and hoses of anyair by separately opening, for about10 seconds, and closing eachblowpipe valve in turn. Deliverypressures should be maintained whilethe gas is flowing, if not re-adjust theregulator knob.

LIGHTING UPWith the system now free of leaks:1. Put on the welding goggles and cap.2. Open fuel gas blowpipe valve F

slightly and light the acetylene flamewith the flint lighter (do not usematches or cigarette lighter).Continue to open the valve until theblack smoke and soot cease andbefore the flame leaves tip end.

3. Open valve O until a neutral clearflame is produced with a brightlydefined inner cone.

4. A neutral flame is used for most workto avoid oxidising the weld surface.A carburising flame with excessacetylene (shown by a feather on theinner cone), and an oxidising flamewith excess oxygen (sharp pointedbluish inner cone) have specialapplications.

WARNING:If a FLASHBACK occurs and theflame goes out. Shut both valves, checkthe connections and then relight. It maybe the result of flow too low, touchingthe tip on the job, overheating or theoxygen cylinder being empty.A BACKFIRE OR SUSTAINEDBACKFIRE (squealing or hissing)occurs when the flame continuesburning back inside the tip or blowpipe.Immediately close the oxygen valve tostop internal burning, then close off thefuel valve.

IF A BACKFIRE OR SUSTAINED BACKFIRE OCCURS• Let the equipment cool for at least

1 minute.• Inspect the mixer o-rings for damage.• Check the regulator settings.• Purge the oxygen and acetylene

separately before attempting to relight.The use of FLASHBACKARRESTORS is recommended tolimit the damage that may result if aflashback occurs. If not stopped, aflashback will melt the equipment close

to the mixer and may travel back to thecylinder. Flashback arrestors have avery sensitive non-return valve thatstops the gas flow and a fine sinteredmetal filter that quenches the flame.

CLOSING DOWN1. Close fuel gas blowpipe valve F.2. Close oxy blowpipe valve O.

IF LEAVING EQUIPMENTUNATTENDED:3. Close acetylene cylinder valve.4. Close oxygen cylinder valve.5. Open fuel gas blowpipe valve F (valve

O closed) drain the line until bothpressure gauges read zero. Release theacetylene regulator knob until loose,then close the blowpipe valve F.

6. Open oxygen blowpipe valve O (valveF closed) drain the line. Release theoxygen regulator knob until loose,and then close the oxygen blowpipevalve O.

Always close the cylinder valves whennot in use.

DISMANTLING THE SYSTEM1. Undo the hose connections at

regulator outlets and blowpipe inlets.2. Unscrew welding tip from the mixer.3. Replace tips (cold), blowpipe and

flashback arrestors (if fitted) in therecesses in the tray.

4.The regulators may be either left inposition on the cylinders or removedand placed in the toolbox.

REMEMBER1. Check for leaks.2. Purge both lines separately.3. Lighting up – first fuel then adjust

oxygen to produce a neutral flame.4. Closing down – close fuel first then

oxygen.5. Close cylinder valve and drain system.6. Release regulator knobs and close

blowpipe valves.

Table 1:Welding - W MixerPlate Tip DA Oxymm Size kPa kPa

0.8 6 50 501 8 50 50

1.6 10 50 502.5 12 50 503.5 15 50 505 20 50 508 26 50 50

Using the Cutting AttachmentUSING THE CUTTINGATTACHMENT1. Follow the set-up instruction for

connecting the welding blowpipe.2. Close the oxygen O and fuel gas F

blowpipe valves.3. Inspect the cutting attachment to see

both o-rings are present.4. Insert the cutting attachment into the

welding handle and hand tighten(teeth locked), cutting head/nozzleperpendicular to the handle.

5. Inspect the nozzle seat in the torchhead. The seat surface must be freeof dirt, dents and scratches.

6. Select the cutting nozzles to suit themetal thickness to be cut (Table 2).Tighten nozzle securely with spanner.

7. Set regulator pressure (Table 2)acetylene & oxygen in the CUT zone.

8. Put on goggles, gloves & welder’s cap.9. Close PH valve O on side of cutting

attachment.10. Fully open the rear oxygen blowpipe

valve O. The cutting attachmentvalve O is used to control thepreheat flame (PH).

11. Open PH valve O half a turn anddepress the cutting oxygen (CO)lever. Adjust oxygen regulator to COpressure in Table 2 while oxygen isflowing. This purges the oxygen line.

12. Release CO lever and close PH valve.13. Open fuel valve F for 10 seconds

then close. This purges the fuel gasline. Do not do this near open flames.

14. Open valve F slowly and ignitepreheat flames at the nozzle withthe flint lighter. Continue to openuntil all smoke and soot cease. Donot use matches or cigarette lighters.

15. Adjust to a neutral flame byopening the oxygen PH valve untilcones are sharp and clearly defined.

16. Depress the CO lever (the preheatwill change slightly) readjust preheatsto neutral by opening PH valve.

CLOSING DOWN CUTTINGATTACHMENT1. Close blowpipe valve F.2. Close oxygen PH valve.

If leaving equipment unattended:3. Close blowpipe valve O.4. Close both cylinder valves.5. Open blowpipe valve F (valve O closed)

drain the DA line until both gaugesread zero. Release the DA regulatorknob then close blowpipe valve F.

6. Open the PH valve and the blowpipevalve O (valve F closed) drain theline, release oxygen regulator knob,then close the PH valve and blow-pipe valve O.

If you experience a BACKFIRE or aFLASHBACK immediately close thePH valve and then close valve F.• Allow the cutting attachment to cool.• Tighten the nozzle.• Check the regulator pressures.• Purge before attempting to relight.

Causes of Flashback:• Dirty nozzle seating.• Not purging gas lines.• Incorrect pressures.• Flow of oxygen or DA too low.• Nozzle too close to work.• Nozzle overheating.

Table 2: CuttingPlate Tip DA Oxymm Size kPa kPa

0.8 6 50 501.0 8 50 501.6 10 50 502.5 12 50 503.5 15 50 505.0 20 50 508.0 26 50 50

BOC Product Range Training Manual Page 9


WeldingWELDING OF STEELThe oxy-acetylene flame has sufficienttemperature and intensity to melt steeland weld edges together forming a jointas strong as the parent metal.1. Choose the welding tip suitable for

the metal thickness from Table 1.2. Clean the edges of the steel & prepare

the joint for welding see Table 3.3. Light the acetylene and set a neutral

flame.

Welding without using a filler rod4. Rotate the flame in a small circle

until molten metal puddle forms.5. Oscillate the tip across the joint in a

circular motion. The tip of the innercone should be 2-3 mm above thepuddle as the tip is moved forward.

Welding with a filler rodincreases the strength of the weld.1. Dip the end of the filler rod into the

puddle. The heat of the puddle willmelt the rod.

2. Hold the rod 2-3 mm above thepuddle and 10 mm from the flame.Oscillate the tip across the joint atthe same time moving the rod and tipforward in the direction of welding.

3. Dip the filler rod into the puddle toadd metal to the weld. The rod mustnot be held continuously in the puddle,but just above it in the secondary coneof the flame to avoid oxides forming.

4. For best results on steel 3 mm orthicker grind a bevel of 30° on eachplate edge.

There are two techniques of welding.1. Forehand – where the rod is movedahead of the tip in the direction ofwelding, for thickness under 5 mm.

2. Backhand – where the rod is movedbehind the tip in the direction ofwelding, used for thickness over 5 mm.

BRAZE WELDINGThe advantage of braze welding overfusion welding is that different metalscan be joined without melting the parentmetal. Repairs can be made on cast iron.1. Before braze welding the surfaces

should be clean and have a good fit up.2.The metals to be joined are preheated

above the melting point of the rod.3. Clean flux is applied on the joint

surfaces to reduce oxidation and float oxides.

4. Heat the rod and dip it into the flux,which sticks to the rod.

5. Heat the joint until both pieces aredull red then insert the rod into thejoint allowing it to melt and flow intoand around the joint.

A neutral flame may be used but aslightly oxidising flame will reduce theflux required.Avoid breathing the fumes.

BRAZINGBrazing and braze welding have similartechniques. A closer fit up is required forbrazed joints as the molten filler metal isdrawn into the joint by capillary attraction.The surfaces must be clean. Mostmetals can be brazed. The commonbrazing filler metals are:• silver base alloys• copper phosphorus alloys• aluminium.The joint clearance (other thanaluminium) should be 0.05 to 0.15 mm,and for aluminium 0.15 to 0.25 mm. Lapjoints produce the most reliable results.

SILVER BRAZINGSilver brazing is faster than bronzebrazing because silver has a lowermelting point than bronze.Silver will not bridge a gap as well asbronze so tight fit up of joints isimportant.Silver brazing is one of the most reliablemethods to join parts with a strong leakproof joint and neat finish.Thorough pre-cleaning of the parts isone of the secrets of successful brazing.1. Apply flux directly to joint.2. Use a ‘soft’ neutral flame.3. Heat the parts uniformly and

gradually – avoid overheating.4.When heat has dehydrated the flux it

will melt and becomes water clear.5. Remove the flame and apply the silver

alloy to the joint, by capillary actionthe silver alloy will follow the heat.When the silver has visibly flowed allaround the joint remove flame.

Do not breathe the fumes.

Table 3:Welding Joints -Tip Sizes

Heating & Cutting


HEATING WITH OXY-ACETYLENEUse a suitable size heating tip. Toosmall takes excessive heating time, toolarge wastes gas.The ProMaster kit has 5 single holewelding/heating tips and a multi-holeheating tip HTW-A1 that will all operatewith the standard W mixer. Acetylenecylinders are restricted in draw-off flow,to a maximum of 1⁄7th of the contentsper hour of operation. Excess draw offcan result in acetone withdrawal thatshows as ‘spitting’ and a green flame.This lowers the pressure in the cylinderand the temperature of the flame.

For a typical 7m3 DA cylinder themaximum draw off is 1m3 per hour (17 L/min).Higher flows will require a number ofDA cylinders manifolded together. Useonly manifolds from a gas equipmentsupplier. This limitation of DA is one ofthe reasons why heating is often donewith LP-Gas.

HEATING – OXY/LP-GasHigh output LP-Gas heating tips HT-PIand HT-P2 (300 & 400 mJ/h) areavailable with a heavy duty HT mixerfor the BOC welding blowpipe. Forhigher output there is an HTP injectorfor the HTP-P3 and HTP-P4 (800 &1000 mJ/h) tips.High flows of LP-Gas will requirecylinders to be manifolded to avoidfreezing as a result of the high draw off.See your BOC supplier.

CUTTING STEELOxy-fuel gas cutting is a thermochemicalreaction in steel where the surface is firstpreheated to an ignition temperature of800°C (cherry red). Then a jet of pureoxygen is directed through the flame,rapidly burning the steel and removingthe molten oxide.This produces a narrowcut or kerf as the nozzle is moved forward.The cutting attachment and nozzles forthe BOC blowpipe are able to cut steelthickness from 2 to 200 mm. See Table 2.Cutting blowpipes are also availablefrom BOC that will cut to 300 mm.

To Cut SteelPlace the steel to be cut where flammablematerials can not be ignited by sparksand molten metal. Sparks can fly up to10 m. Be sure hoses are clear of moltenmetal and sparks. Use a metal tray orsand trough to confine the molten slag.Before starting, the plate should becleaned of dirt, paint, oil, scale and rust.Mill scale can be removed by movingthe preheat flame over the line of cut.

TO START A CUT1. Select the cutting nozzle appropriate

to the metal thickness. Set the oxygenand fuel gas pressures according toTable 2 – CUT zone on the gauge.

2. A neutral oxy-fuel flame is used forpreheating as described for operatingthe cutting attachment.

3.To start, hold the inner cones of thepreheat flame just above the edge ofthe plate until it becomes cherry red.

4. Slowly depress the cutting lever (CO)to commence flow of oxygen andbegin cutting. Move the torchuniformly along the line of cut whilemaintaining the preheat cones 5 mmabove the metal. The sound ofsputtering and a steady stream ofmolten metal indicate a good cut.

5.To stop the cut, release the CO lever.Close the blowpipe valve F, close PHoxygen valve.

If use of the cutting attachment is to bediscontinued, close the blowpipe valveO at the rear.The quality and speed of freehandcutting depends upon the steadiness ofthe operator.

Flame SettingsFor acetylene, set preheat flames toneutral.For LP-Gas, set preheat neutral byprogressively increasing both LP-Gasand oxygen until the preheat conescease to shorten.

CUTTING ACCESSORIESA roller guide attached to the cuttingnozzle will assist the operator to maintaina constant distance from the plate.A circle cutting attachment fitted to aradius bar & roller guide provides a simplemeans to produce clean circular cuts.

Experience will soon show the optimum flame setting, nozzle height and speed ofmovement to produce a smooth surface.

Cutting, Cleaning & HardeningGENERAL CUTTINGThin Steel (6 mm or less)Use the smallest nozzle 6C or a specialsheet metal nozzle with single preheat6SM.

Thick SteelIf the cut cannot be started easily theoperator may try to start by angling thenozzle. As the corner is cut, move thenozzle to a vertical position until thetotal thickness is cut.

Painted or Galvanised SteelClean the surfaces as much as possiblebefore starting. This will minimise toxiczinc-oxide fumes. If the nozzle is held ata slight angle it will help to undercutpaint and scale.A respirator should be worn.

PIERCING HOLES IN STEEL1. Set neutral flame.2. Hold nozzle just above plate and heat

a spot to bright red.3. Slowly depress the CO lever and

raise the nozzle to about 12 mmabove the plate so that slag will notblow back into the nozzle. The nozzleis then moved slightly to one side andtilted to start a small spiral motion.

4.When a hole has burnt through,lower the nozzle to normal height,6mm above the plate and proceedwith the cut.

FLAME GOUGINGFlame gouging provides a means forcutting U-shaped grooves for theremoval of defects and welds.Special gouging nozzles can be usedwith standard cutting equipment. Thesenozzles deliver a large jet of oxygen atlow velocity. If the nozzle is properlymanipulated a smooth groove can begouged out of the plate surface. Varioussize nozzles are available for gouginggrooves of different widths. Variousgrooves can be produced by varying thespeed of travel, oxygen pressure and thenozzle angle, see Table 4.1.To start, set a neutral flame. Hold the

nozzle at approximately. 20-30° to thesurface, pointing along the line of cut.

2.The preheat flames cause the startingspot to become bright red.

3. Gradually depress the CO lever, as thecut progresses reduce the angle of thenozzle to about 5°. If the angle is toolow, the groove will become too shallow.If too high the slag will flow backwards,or the groove may be too deep.

4. Hold the nozzle above the surfacewith the preheat cones 5 to 10 mmbehind the spot where cutting isoccurring. The nozzle should be heldso that it does not ride on the bottomof the groove. Bent gouging nozzles(GB) allow easier control.

Gouging may be done using either oxy-acetylene or oxy-LP-Gas withappropriate nozzles.Only use LP-Gas nozzles marked Pwith torches fitted with propane ‘P’mixers. These must not be used withacetylene. Severe flashbacks will result.

Note: Purging before lighting isimportant because cutting torchpassages usually retain mixed gas. Thereis also more likelihood of blocking theend of the nozzle when cutting inconfined spaces, which will cause aflashback. Flashback arrestors arerecommended. Assembly, setting upand lighting follow the same steps asgiven for the cutting attachment.

FLAME CLEANINGSpecial tips with high temperature andhigh velocity oxy-acetylene flames areused to remove rust, scale and paint. Atthe same time moisture is removed andthe warm surface aids the application ofprotective paint. The normal weldingblowpipe is used with the heavy dutyHT mixer.The rust and scale is removedby dragging and scrubbing the flameover the surface. Paint is best removedby pushing the flame across the surface.A highly oxidising flame is used with ato and fro scraping motion of the tip to

remove heavy scale and rust. Protectiveclothing and goggles are necessary toguard against hot flying particles.

FLAME SPALLINGThe high temperature ‘Flame Cleaning’tips may be used to roughen concrete.The flame is moved over the surfacecausing fragments to expand and flyleaving small craters. Protectiveequipment is essential to guard againstflying heated particles. A highly oxidisingflame is best, with flow rates of oxygenand acetylene increased until the flameis burning just off the nozzle orifices.

HARD FACINGThis process is the addition of an alloycoating to new or worn parts thatprovides increased resistance to wearand corrosion.1. Correct preparation is important.

The surfaces must be clean(preferably by grinding) with cornersgrooved, not chamfered and avoidingsharp internal corners.

2. Use a carburising oxy-acetylene flamewith the acetylene feather 2 or 3times the length of the inner cone.The inner cone of the flame is heldabout 3 mm from the surface untilthe surface ‘sweats’.

3.The alloy rod (preheated in theflame) is deposited in the ‘sweat’keeping the inner cone almosttouching the rod.

4.The deposit may be reheated tocause it to flow to a smooth finish.

FLAME HARDENINGA simple process for local hardening oflow carbon steels. The surface is firstheated and then quickly cooled byquenching in water. The oxy-acetyleneflame rapidly heats a thin layer of the steelto above the critical temperature & thenquenching hardens the surface layer.

Table 4: GougingNozzle Fuel Oxy

Size kPa kPa

32GS 100 50032GB 100 50048GB 100 60064GB 100 650

Groove Size (mm)32 8 wide x 4 deep48 10 wide x 6 deep64 13 wide x 8 deep

BOC Product Range Training Manual Page 12

Care & Maintenance


CARE & MAINTENANCE OFWELDING TIPS & CUTTINGNOZZLESThe efficiency of welding and cuttingflames depends upon the condition ofthe nozzle orifices.Welding tips should have a uniformsymmetrical straight flame withoutdistortion of the inner cone and outerenvelope. Cutting nozzles should haveuniform preheat flames with equal innercones, and the CO jet should bestraight and symmetrical.If the holes become obstructed by smallparticles of carbon or hot metal theflame will be distorted. Using the nozzlecleaner supplied can rectify this.• The cleaner should be selected on the

basis of the size that will enter thehole and remove the obstruction. Ifthe next larger will then fit, it shouldbe used to hone the bore.

• Cleaners should only be worked up anddown and not twisted. Be careful notto bell-mouth the outlet of the orifice.

• The orifice must be round with squareedges and no burs. To restore theedge, rub the end on fine emery clothon a flat surface (such as glass), whileholding the nozzle perpendicular tothe flat surface.

• If the preheat still appears short it isprobable there are still obstructions inthe gas passage – repeat cleaning.

• If the flame goes out with a snap whenthe valves are closed it is probable thatthe orifices are still bell-mouthed.

Do not interfere with the taper seatsurface on either the nozzle or thecutting head. Nozzles and tips shouldnot be thrown into a box so thatthey strike one another. The BOCToolbox has snap-in recesses that permiteach item to be identified and protected.

MAINTENANCE OF THE OUTFITYou have an obligation and responsibilityto maintain your equipment in a safecondition. Equipment should beregularly checked and if necessaryrepaired by an authorised BOC repairerusing genuine spare parts.

Blowpipe1. If the valves develop leakage around

the valve spindle tighten the packinggland nut. To alter the turningresistance tighten the gland nut.

2. Check the condition of both o-rings onthe mixer by removing the hook andsliding the nut to expose the o-rings.If they are chipped or worn removethe o-rings with a clean narrow blunttool that will not damage the metalgrooves. Roll in new replacement o-rings and twist to seat in the groove.

3. If the blowpipe valves continue toleak even after removing and wipingthe nose with a clean cloth, the valveshould be replaced by a new assembly.

4. If the metal seating in the valve bodyhas been damaged have an ApprovedRepairer reseat the body.

Cutting Attachment1. If the preheat valve develops leakage

around the spindle tighten thepacking gland nut.

2. If the valve will not close off, removethe assembly and wipe the seatingnose and replace. If this does not stopthe leak replace the valve assembly.

3. Check the condition of the o-rings bydepressing the locking clip and slidethe nut off to expose the o-rings. Ifthey are chipped or worn remove theo-rings with a clean narrow blunt toolthat will not damage the metal grooves.Roll in new o-rings and twist to seat.

4. If the cutting oxygen valve will notsnap closed or is leaking fold back

the lever, undo the hexagon retainerand fit a replacement capsule.

If there is more extensive damage orleakage have an Approved Repairerservice it with genuine spare parts.

Regulators1. If the bullnose o-ring has been

chipped or worn roll out the old onewith clean fingers and fit a genuinereplacement. Note: The bullnose willstill seat if the o-ring is missing.

2. If the delivery pressure gauge pointercontinues to rise (creep) beyond theinitial reading (into the Red band)when the blowpipe valves are closed anew seat capsule is required. A rise of50 kPa is considered excessive.

3. If leakage occurs around the bonnet,the pressure gauge stems, the outlet,the pressure relief valve, and thebullnose connection have anApproved Repairer service theregulator with genuine spare parts.

4. Always protect the oxygen regulatorfrom contamination by oil andgrease. If this occurs return it to yourApproved Repairer for cleaning.

Regulator repairs requirespecialised equipment.Repairs should not be attemptedwithout proper service instructionsand genuine spare parts.

Hoses1. Regularly check hoses for leakage.

The simplest method is immersion ina water bath.

2. Factory hose assemblies with crimpedhose ferrules are recommended.

3. If hoses are cut do not repair eitheracetylene or oxygen hoses with make-shift tubing, twisted wire & tape. Theend pull on hoses may cause a leak.Use proper joiners or replace wholeassembly.

4. Keep hoses away from oil and grease &never use with oil lubricated air tools.

5. Use only blue hose with right-handthreaded fittings for oxygen, red hosewith left-hand fittings for acetylene andorange hose for LP-Gas. If hoses areburned in a flashback, discard the hose.

Repair kits are available withinstructions from BOC for competentusers to change faulty components. Moreextensive repairs should be carried outby BOC Repairers.

Serviceable parts


Cutting Tables

W Mixer is used with all tips listed:• To prevent withdrawal of acetone from DA cylinders for 7 m3

(G) cylinder max. draw off 17 L/min - 3.2 m3 (E) cylindermax. draw off 8 L/min.

• If flame becomes green, flows exceed rates for a single cylinder-manifold 2 or more DA cylinders.

Gas consumption and speeds apply to normal workshop conditions.Since these do not always exist in practice variations can be expected.Experienced operators will find they may achieve satisfactory results withlower gas pressures and lower consumption of gases.

Groove Size (mm)32 8 wide x 4 deep48 10 wide x 6 deep64 13 wide x 8 deep

Unacceptable Lock-Up

Comprehensive Cutting Tables

Table 5: Cutting Mild Steel Oxy-Acetylene (DA)Plate Nozzle DA Oxy Speed DA Oxymm Size kPa kPa mm/min L/min L/min

1-5 6 100 180 450 2 116-10 8 100 200 400 3 20

12-20 12 100 220 350 4 4025-40 15 100 250 300 6 6050-80 15 100 350 220 7 80

100-125 20 100 400 150 10 150150-200 24 100 500 120 13 260

Table 9:Welding & Heating Oxy-Acetylene (DA)Plate Tip DA Oxy DA Oxymm Size kPa kPa L/min L/min

0.5-0.8 6 50 50 1.5 1.50.8-1.0 6 50 50 2.0 2.01.0-1.5 10 50 50 3.0 3.01.6-2.4 10 50 50 4.0 4.01.6-2.4 12 50 50 7.0 7.02.5-3.5 15 50 50 12.0 12.04.0-6.5 20 50 50 22.0* 22.0*HEAT HTW-A 150 100 50.0* 50.0

Table 7: Gouging Oxy-Fuel Gas (DA & LPG)Plate Nozzle DA Oxy Speed DA Oxymm Size kPa kPa mm/min L/min L/min

32GS 100 500 15 60 12 9532GB 100 500 15 60 12 9548GB 100 600 18 85 12 12064GB 100 650 20 110 15 150

Table 6: Cutting Mild Steel Oxy-LP-Gas (LPG)Plate Nozzle DA Oxy Speed DA Oxymm Size kPa kPa mm/min L/min L/min

2-5 6 100 180 450 1.5 176-10 8 100 200 400 3.0 30

12-20 12 100 220 350 4.0 5025-40 15 100 250 300 5.0 7550-80 15 100 350 220 5.0 85

100-125 20 100 400 150 6.0 160150-200 24 100 500 120 9.0 300

Table 8a:Welding - W MixerPlate Tip DA Oxymm Size kPa kPa

0.8 6 50 501.0 8 50 501.6 10 50 502.5 12 50 503.5 15 50 505.0 20 50 506.5 26 50 50

Table 8b: CuttingPlate Tip DA Oxymm Size kPa kPa

3 6 100 1806 8 100 200

12 12 100 22025 15 100 25050 15 100 350100 20 100 400200 24 100 500

• Crack cylinder valves before connecting regulators.• Open cylinder valves slowly to pressurise regulators.• Check no leaks are present before ignition.• Purge each hose before lighting up.

Filler Rod & Flux Reference Table


Table 10: Ready Reference – Filler Rod & Flux Selection

Flame N - NeutralSO - Slightly oxidisingSC - Slightly carburisingGP - General purpose

MATERIAL FLAME FILLER ROD FLUX

Fusion WeldingIron N Mild Steel -Mild Steel N Mild Steel -Medium Carbon Steel SC Triple Deoxidised Steel -Cast Steel N Steel -Cast Iron N Cast Iron Cast IronStainless Steel N 347 Stainless steel StainlessCopper, Bronze, Brass SO Tobin Bronze Copper & BrassAluminium N Pure Aluminium AluminiumDie Casting Option Die Cast -

Braze WeldingSteel SO Manganese Bronze Copper & BrassCast Iron SO Manganese Bronze BronzeMalleable Iron SO Manganese Bronze BronzeAluminium N Pure Aluminium AluminiumEverdur N-SO Tobin Bronze Copper & Brass

Silver BrazingCopper, Bronze, Brass N Prosilver 2, 5, 15 & 45 SBA FluxSteel N Prosilver 35 & 45 GP FluxStainless N Prosilver 503 & 402 Stainless Steel Flux

Documents

Welding & Cutting Guide€¦ · required for using the gas welding, cutting and heating equipment supplied in this BOC kit. BOC has accumulated extensive knowledge in the design and