The Oxy-Acetylene Flame


The heat source for this process is a chemical reaction resulting from the combustion of acetylene with oxygen. This is an exothermic reaction in which equal volumes of acetylene and oxygen supplied by the blowpipe react to produce carbon monoxide, and hydrogen as products of the first stage of combustion. The reaction is as follows:

Neutral Flame

As the supply of oxygen to the blowpipe is further increased, the flame contracts and the white cone becomes clearly defined, assuming a definite rounded shape. At this stage approximately equal quantities of acetylene and oxygen are being used and combustion is complete, all the carbon supplied by the acetylene is being consumed and the maximum heat given out. The flame is now neutral, and this type of flame is the one most extensively used by the welder, who should make himself thoroughly familiar with its appearance and characteristics.

Carburising Flame

This is a flame in which an excess of acetylene is burning, i.e. combustion is incomplete and unconsumed carbon is present. When lighting the blowpipe the acetylene is turned on first and ignited, giving a very smoky yellow flame of abnormal size, showing two cones of flame in addition to an outer envelope; this is an exaggerated form of the carburising flame, but gives out comparatively little heat and is of little use for welding. When the oxygen is turned on and the supply is gradually increased, the flame, though still of abnormal size contracts towards the blowpipe tip where an inner white cone of great luminosity commences to make its appearance. If the increase in the supply of oxygen is stopped before the cone becomes clearly defined and while it is still an inch or so long, the result is a carburising flame which is mainly used for hard surfacing and should not be employed for welding steel as unconsumed carbon may be introduced into the weld and produce a hard, brittle, deposit.

Oxidising Flame

A further increase in the oxygen supply will produce an oxidising flame in which there is more oxygen than is required for complete combustion. The inner cone will become shorter and sharper, the flame will turn a deeper purple colour and emit a characteristic slight "hiss", while the molten metal will be less fluid and tranquil during welding and excessive sparking will occur. An oxidising flame is only used for special applications, and should never be used for welding.

Depending on the type of attachment, the Oxy/Acetylene torch can be used for heating and bending, welding, or cutting metal. The Plasma Cutter will also cut through metal, but only up to 3/8" thick.

  • Follow the cutting chart for proper cutting speeds (similar to the plasma cutter) if using the cutting head
  • Cutting/Welding tips will still be hot after use, be careful where you put the torch handle
  • Always use the right size tip for cutting and welding
  • Extra tips should be put away when not in use
  • The rosebud torch is best for heating metal for bending



Lighting Procedure

  1. Be ready to be safe
  2. Stand to the side of the Regulators and slowly turn the Oxygen tank valve to its fully opened position (sudden blast of oxygen can blow regulator apart)
  3. Slightly open the Oxygen valve on torch handle
  4. Begin to tighten the oxygen regulator adjustment valve until the dial reads between 5 and 8 PSI
  5. Once appropriate pressure has been set, turn the Oxygen valve on torch handle off
  6. Standing to the side of the regulators, open valve on the Acetylene tank ¼ of a turn (for fast emergency shut off)
  7. Slightly open the Acetylene valve on torch handle
  8. Turn the Acetylene regulator adjustment valve in slowly until dial reads the same or less than the Oxygen. Warning: Never set Acetylene regulator over 8 PSI. It becomes unstable and can explode!!!
  9. Close Acetylene valve on torch handle
  10. Point torch handle away from your self and any bystanders
  11. Turn Acetylene valve on torch handle, ¼ of a turn
  12. Using the proper flint striker provided, light the gas and adjust the gas just so the flame stops producing black soot
  13. Turn the Oxygen valve slowly until flame is blue, the little blue flame in the centre sticks out around ¼" from the tip of the torch
  14. To turn off the torch shut off the Acetylene torch valve first, then the Oxygen valve.
  15. Shut off both tank valves completely
  16. Open torches valves and purge the lines
  17. Slacken off regulator valves
  18. Shut off valves on torch


Safety Procedures

  1. Eyes must be protected by Welding Goggles with darkened glass lens
  2. Steel melts at nearly 3000 degrees F, Human Flesh Burns at a lot less
  3. Always wear protective Gloves, Aprons, and Arm Protection
  4. NOTE:  Some molten metals will stick to your skin
  5. Never wear frayed clothing; sparks and flames could catch it on fire
  6. Never wear Synthetic Materials that could melt to your skin
  7. Never keep a lighter in your pocket when using the torch. !!!!!
  8. Gas Cylinders must be kept Chained Down, and capped if not in use
  9. Only use the tank dolly to transport tanks. Tanks must be chained in dolly
  10. Make sure that the colour coded hoses go to the right place (Red: Acetylene / Green: Oxygen)
  11. NEVER, NEVER, EVER  oil the threads of a gas cylinder when hooking up gauges!!!!  This can cause a serious explosion!!
  12. Acetylene is an extremely flammable gas and it will take away breathing air if used in a confined space. Make sure Ventilation is Turned On
  13. Mark freshly heated work as HOT!!! Or stand guard wile it cools
  14. Feel for heat before you grab vice grips, clamps, pliers, or metal


Recommended Personal Safety Equipment while working with the Oxy/Acetylene Torch
Head/Face/Eyes Clothing Hands Feet Ear Respirator


Hardened Shaded Welding Goggles, Shade 5


Leather welding jacket and long pants


Leather welding gloves


Leather top shoes


NO tennis shoes, open toed shoes, or shoes with nylon




Ear Plugs or Ear Muffs

Recommended if using cutting torch

Required if forging metal


NIOSH-Approved N95 Disposable Particulate Respirator


Initial lighting of the acetylene gas produces large amounts of soot


Operating Safety

  • There are two sets of regulators and valves; one for oxygen (color code = green) na one for the acetylene (color code = red)
  • THERE ARE TWO GAUGES ON EACH REGULATOR. ONE ON THE RIGHT, INDICATES TANK PRESSURE, AND ONE ON THE LEFT INDICATES GAS PRESSURE IN THE LINE. (See photo below)
  • CHECK ALL CONNECTIONS before lighting the torch
  • NEVER stand directly in front of or behind a regulator when opening the cylinder valve
  • TURN BOTH CYLINDERS OFF IMMEDIATELY when the torch flashes back, or is burning on the inside
    • First oxygen and then acetylene
  • NEVER open both fuel(acetylene) and oxygen valves before lighting the preheat flame
  • ALWAYS turn the oxygen cylinder valve all the way open
  • Open the acetylene cylinder valve not more than one turn. One-half turn is preferred
  • ALWAYS place the welding tip so that it points to the side of the torch to which the acetylene hose is attached
  • ALWAYS weld at least 5 feet from the cylinders
  • DO NOT use any oil or grease on any oxygen or acetylene connections
  • NEVER hammer on oxygen or acetylene regulators or stuck valves
  • DO NOT light a torch with a match or open flame. Use a striker
  • BEFORE LIGHTING TORCH, be positive that hose, tanks, or any inflammable material will not be exposed to heat, flame, or sparks
  • BEWARE OF HIGH ACETYLENE PRESSURE. NEVER USE ACETYLENE GAS WHEN THE PRESSURE IS GREATER THAN 15 POUNDS PER SQ. IN. (acetylene gas when compressed to more than 15 pounds per sq. in. becomes a very high explosive.)
  • DO NOT hold welding or cutting tip too close to your work
  • NEVER USE a tip that gets too hot
  • NEVER USE a torch that leaks
  • NEVER LEAVE TORCH BURNING AND GO AWAY FROM IT
  • NEVER leave torch valves open
  • DO NOT adjust, alter, change, build, or do any experimental work on cylinders, regulators, torches, or any other gas equipment.
  • DO NOT LIFT cylinders by the caps or valves
  • DO NOT TRANSPORT the cylinders without the caps in place
  • CYLINDERS MUST BE STORED IN UPRIGHT POSITION AND CHAINED TO THE WALL
  • KEEP VALVES CLOSED on empty cylinders
  • NEVER WELD A CLOSED OR JACKETED VESSEL WITHOUT AN AIR VENT
  • NEVER WELD A VESSEL THAT HAS CONTAINED ANY EXPLOSIVE OR FLAMMABLE MATERIAL UNTIL YOU ARE POSITIVE THAT IT HAS BEEN THOROUGHLY EMPTIED AND PURGED, AND THEN USE EXTREME CARE
  • REFER to instruction manual for further information (RTFM)


Flashback arrestors

from BuyWeld.com

Flashback arrestors and reverse flow check valves provide additional protection against flashbacks. Victor recommends the use of these devices when ever possible. Victor addon flashback arrestors contain both a reverse flow check valve and a flashback arrestor. Due to the high flow requirements of Victor Heavy Industry torches, it is important to use flashback arrestors that have sufficient flow capacity.

    It is important to understand the difference between reverse flow check valves and flashback arrestors.
  • Reverse Flow Check Valves: Helps to prevent the reverse flow of gases from traveling past the check valve.
  • Flashback Arrestors: Prevents a flame from traveling past the flashback arrestor in the event of a flashback.

Note: The use of both regulator and torch mount flashback arrestors with heavy industry apparatus requiring high gas volume is not recommended because it may cause excessive flow restriction. It is always better to place the safety devices at the rear of the torch than at the regulator.



Cutting Tip Guide

Metal Tip Tank Pressures
Size Size Acetylene Oxygen
1/8" 000 3-5 20-25
¼" 00 3-5 20-25
3/8" 0 3-5 25-35
½" 0 3-5 30-35
¾" 1 3-5 30-35
1" 2 3-6 35-40
2" 3 4-8 40-45



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