LIGHTNG THE WELDING TORCH

                                                                 

 1) Crack the cylinder valve on oxygen and cylinder by opening the valve and closing it quickly in order to blow out foreign matter.

2)Attach the oxygen and acetylene pressure regulator to the respective oxygen and acetylene cylinders.

3)Attach the hoses to the pressure regulators.

4)Attach the other ends of the two hoses to the welding torch.

5)Select the proper tip(nozzle) and mixing head and attach it to the welding torch.

6)Back off the regulator screws on both units until the screws turns freely.This is necessary to eliminate a
sudden surge of excessive pressure on the working side of the regulator when the cylinder is turned on.
7)Make sure that both torch needle valves are turned off  (clock-wise).

8)Open the acetylene cylinder valve 1/4 to 1/2 turn. Open the oxygen cylinder valve all the way.

9)Open the acetylene (torch) needle valve one full turn.Turn the adjusting screw on the acetylene pressure regulator clockwise until acetylene gas comes from the torch tip.

10)Light the welding torch using a spark lighter.

11)The acetylene pressure regulator screw should then be adjusted until there is a gap of about 6mm between the torch tip and the flame.This is the proper pressure for the size of the tip being used regardless for the gauge pressure shown on the working pressure gauge on the regulator.

12)Oxygen needle valve on the torch is then opened to adjust the welding flame.

TYPES OF WELDING FLAMES

To Ignite a Flame
Open the acetylene control valve of the welding torch and after the system has been flushed to clean the torch nozzle the gas is ignited. At this stage enough oxygen is drawn in from the atmosphere to burn acetylene partially.
The acetylene control valve is then adjusted until the flame ceases to smoke. The oxygen control valve of the welding torch is then opened in order to adjust the proportion in which acetylene and oxygen are required to mix and burn.
Types of Flame:

                                                                     fig-1

                                                                         fig-2

1-Neutral flame (Acetylene Oxygen in equal proportions)
2-Oxidising flame (Excess of Oxygen)
3-Reducing flame (Excess of Acetylene)

In oxy-acetylene welding flame is the most important tool.All the welding equipment simply serves to maintain and control the flame.The correct type of flame is essential for the production of satisfactory welds.
The flame must be of proper size,shape and condition in order to operate with maximum efficiency. 

GAS WELDING PROCESS AND EQUIPMENTS

Gas welding is a fusion welding processes which joins metals using the heat oh combustion of an oxygen/air and fuel gas (i e. acetylene,hydrogen,propane or butane ) mixture. The intense heat (flame) thus produced melts and fuses together the edges of the parts to be welded, generally wit the addition of filler metal.

OXY-ACETYLENE WELDING

When acetylene is mixed with oxygen wit appropriate proportion in the welding torch and ignited, the flame resulting at the tip of the torch is sufficiently hot to melt and join the parent metal.
The oxy-acetylene flame reaches a temperature of about 3200 degree Celsius and thus can melt all commercial metals during welding,actually flow together to form a complete bond. A filler metal rod is generally added to the molten metal pool to build up the seam slightly for greater strength.
Oxy-Acetylene welding does not require the components to be forced together under pressure until the weld forms and solidifies.