In this process, the heat source is combustion of acetylene gas. Chemical reaction of acetylene and oxygen produces a great deal of heat and the oxyacetylene flame burns with temperature exceeding 3250°C, enough to melt most metals and alloys.
Two systems are in vogue for oxyacetylene welding:
(i) High pressure system:
In this system, both oxygen and acetylene gases are drawn from cylinders in which these gases are stored at high pressure.
(ii) Low pressure system:
In this system, oxygen gas is drawn from a cylinder as before, but acetylene gas is produced at site at low pressure. Acetylene gas is produced in a sealed container in which water falls drop by drop on calcium carbide. This acetylene gas is drawn for oxyacetylene welding as per requirement.