OxyFuel Equipment

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OxyFuel Equipment
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Introduction

• Oxyfuel welding is a welding process where the
  heat for fusion is supplied by an torch using
  oxygen and a fuel gas.
• Several different fuel gasses can be used

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Fuel Gasses

• Propane (LPG)
• Natural Gas
• Acetylene
• MAPP
• Hydrogen

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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.

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OxyFuel Safety

• The hazards of oxyfuel welding are primarily
  compressed gas cylinders, flammable gases and
  open flame.
• Common concerns are (pg 294)
• 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

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OxyFuel system

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

• Oxygen safety disc
• Oxygen cylinder valve
• Oxygen cylinder pressure gauge
• Oxygen working pressure gauge
• Oxygen regulator
• Oxygen regulator adjusting screw
• G. Acetylene cylinder safety disc
• H. Acetylene cylinder valve
• I. Acetylene cylinder pressure gauge

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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

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Oxygen Cylinder

• One piece, seamless construction.
• Each cylinder has unique serial number and number
  is recorded in national registry.
• Scheduled inspection required.
• 2,200 psi when filled
• Safety disc, nut, releases at 3,000 psi.
• 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.

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Oxygen Cylinder Valve

• Special double seat valve.
• Must be opened all of the way when in use.
• Right hand threads

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Acetylene Cylinder

• 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.

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Acetylene Valve

• Acetylene cylinders are low pressure cylinders,
  therefore the valve packing can contain the
  cylinder pressure and only a single seat is used.
• Fuel cylinders are left hand threads.

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LPG Gas Cylinders

• Simpler hollow steel containers.
• New regulations require float shut-off.
• Because gas is under pressure, cylinder contains
  both liquid and vapor.
• Equipped with spring loaded pressure relief
  valve.
• Newer style fitting being adopted.
• Common sizes are 30, 70, and 100 pound.

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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.
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Regulators

• Oxyfuel welding and cutting uses two types
• Single stage
• Two stage
• Correct use
• Insure adjusting screw is back off when shut
  down. Check before starting.
• Set correct working pressure.
• Two potential problems
• Regulator creep
• Gauge not returning to zero

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Regulator ProblemsRegulator Creep

• Regulator creep is a potentially dangerous
  condition that occurs when the regular does not
  maintain working pressure.
• When the system is on, and no gas is flowing, the
  working pressure slowly increases.
• Potential outcomes
• Rupture of regulator safety relief valve.
• Explosion of low pressure gauge.
• Rupture of gas hose.
• Causes
• Foreign material inside the regulator.
• Failure to release the regulator adjusting screw
  before opening the cylinder.
• Normal wear

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Regulator ProblemsNot Returning To Zero

• The bourdon tube inside the regulator can be
  damaged, distorted.
• When this occurs, the gauge needle does not
  return to zero.

• Causes
• Opening cylinder with the regulator adjusting
  screw turned in.
• Hard impact.

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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.

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Welding Tip Size
Example welding tip selection and working
pressure chart.
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Backfire Flashback

• Backfire indicated when the torch goes out with
  a loud pop.
• Caused by hot metal in the tip.
• The gasses rapidly combust inside the tip and
  cause a burst of high pressure.
• When it occurs, stop and inspect the tip and
  clean if necessary.
• Flashback occurs when the flame burns inside of
  the torch.
• Usually accompanied by a shrill hissing or
  squealing sound.
• May have puffs of black smoke coming out of the
  tip.
• A potentially serious condition. If not stopped
  the flame can travel up the hoses and into the
  regulator.
• Primary cause is a blocked tip and unequal
  working pressures.
• The potential harm of both backfires and
  flashbacks is controlled through the use of check
  valves and flashback arrestors.

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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.

• The torch valves should only be hand secured, not
  tightened.
• The valve stem packing should be tightened if
  gasses leak past or when the torch valve becomes
  too easy to turn.

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Oxyfuel Torches

• Safety codes require torches to have check valves
  and flashback arresters.
• Note this is a relative new code. Older torches
  will not have check valves or flashback arresters
• If not included, they should be added in line
  between the regulator and the torch.

Check valves
Flashback arrestor
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Oxyfuel Welding Tips

• What is normally called a welding tip is actually
  a welding tip and a mixing chamber.
• Some manufacturers put the mixing chamber in the
  torch, Victor are in the welding tip.

• Tips have different sizes of orifices.
• Size usually indicated by number.
• Manufacturers use different number systems.
• When fuel gas other that acetylene is used a
  larger size tip is required.

• Tips for heating may have multiple orifices.
• Tips require periodic cleaning.
• A dirty tip will have a forked outer envelope.
• Tip orifice should be cleaned with a tip cleaner.

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Using Tip Cleaner

• Start with the smallest size that will enter the
  orifice without excessive force and work up to
  orifice size.
• Be careful, a broken tip cleaner usually means a
  destroyed tip.
• Clean the face of the tip with the included file.

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Airacetylene 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.

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Hoses and Connections

• Requires special nonporous hoses.
• Hoses are color coded.
• Green oxygen
• Red or Black fuel gas
• Connections
• Oxygen right hand
• Acetylene left hand
• Hoses should be protected from hot metal and
  physical damage.

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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

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Setting Up Oxyfuel System

• Extinguish all open flames and stop processes
  that produce sparks.
• Steps (assuming new system)
• Secure cylinders
• Remove caps
• Crack cylinder valves
• Connect regulators
• Open cylinder valves
• Connect hoses to cylinders
• Connect hoses to torch body
• Connect welding tip to torch body
• Set working pressures
• Check system for leaks.

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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.

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Questions?