Oxy-Acetylene Welding: Techniques, Equipment & Safety

Posted on Mar 30, 2025 in Telecommunication Sciences and Technologies

Welded Joints: An Introduction

Welded joints: These are created through a welding process, generally joining two pieces by using a heat source to achieve fusion. There are two main types:

  • Homogeneous
  • Heterogeneous

Oxy-Acetylene Torch Welding

Oxy-Acetylene Torch: This involves reaching the fusion temperature at the edges of the pieces being welded, or reaching the appropriate temperature to melt the filler rod when welding materials of different natures (heterogeneous welding).

Gases Used in Oxy-Acetylene Welding

  • Acetylene: This is the fuel. It’s stored in special bottles dissolved in acetone at a pressure of 15 bar.
  • Oxygen: This is the oxidizer. It’s stored in special bottles at a pressure of 150 bar.

Welding Equipment Checklist

Welding Equipment:

Essential equipment includes an oxygen bottle, an acetylene bottle, an oxygen hose (typically blue), an acetylene hose (typically red), two oxygen safety valves and one acetylene safety valve, two pressure regulators, a blowtorch, and a cart for transporting and supporting the oxy-acetylene setup.

Important Safety Note: Never grease the oxygen valves or handle them with rags that have been exposed to grease. These materials can ignite instantly in contact with pure oxygen.

Safety Valves: Preventing Backfires

Safety valves: These prevent the flame from recoiling into the hoses and bottles, which could cause fires and explosions. They should be placed as close as possible to the torch.

Oxygen Pressure Regulator

Oxygen Pressure Regulator: Typically blue, it consists of:

  • Two Gauges: These indicate the gas pressure from the bottle and the pressure reaching the torch.
  • Pressure Regulator: Used to control the pressure reaching the torch.
  • Scales: Ranging from 0 to 300 kg/cm2 and from 0 to 15 kg/cm2.

Acetylene Pressure Regulator

Acetylene Pressure Regulator: Typically red, it comprises:

  • Two Gauges: These indicate the gas pressure from the bottle and the pressure reaching the torch.
  • Pressure Regulator: Used to control the pressure reaching the torch.
  • Scales: Ranging from 0 to 25 kg/cm2 and from 0 to 2 kg/cm2.

Note: 1 kg/cm2 is approximately equal to 1 bar.


Types of Flames in Oxy-Acetylene Welding

  • Neutral Flame: The proportion of oxygen and acetylene in the mixture is well-balanced, resulting in complete combustion of the gases.
  • Oxidizing Flame: Starting from a neutral flame, adding more oxygen creates an excess of oxygen in the mixture. This flame is characterized by a shorter, more intense inner cone.
  • Reducing Flame (or Fuel-Rich Flame): This flame is characterized by an elongated, undefined, white, and extended plume.

Pressure Regulation: Oxygen and Acetylene

Pressure Reducing Regulator (Oxygen): With the torch open, adjust the pressure regulator to increase or decrease the pressure. The pressure should be between 1.0 and 1.5 kg/cm2. Close the oxygen tap.

Acetylene Torch: Repeat the process, this time adjusting the acetylene pressure regulator to set the gas pressure between 0.3 and 0.5 kg/cm2.

Flow Regulation: Maintaining the Flame

Flow Regulation: When increasing the flow, maintain the same proportions of oxygen and acetylene to keep a neutral flame. To control this, slightly open the acetylene tap, lengthening the inner cone. Then, slowly open the oxygen tap to shorten the cone and achieve a neutral flame.

To reduce the flow, starting from a neutral flame, slowly close the acetylene tap to return to a neutral flame with less heat output.

Troubleshooting Common Welding Issues

  • Flame Deregulation: Often caused by overheating the nozzle.

Solution: Re-regulate the flame.

Irregular Inner Cone: Obstruction at the nozzle.

Solution: Clean the obstruction by gently rubbing the torch on a piece of wood.

Cracking Noises with Metal Projection: Low solder flow or blockage in the nozzle.

Solution: Increase the flow or clean the nozzle.

Clicking, Dry, Repeated Noises: Overheating the solder nozzle at close range.

Solution: Cool the nozzle.

Popping Off Dry with Flame: Flashback, which is dangerous.

Solution: Close the taps and wait. Quickly check the equipment’s condition.