What is the first step when performing oxyacetylene welding?

The initial step in performing oxyacetylene welding involves closing the regulator valves while opening the cylinder valves. This sequence ensures that the gas supply is safely controlled before it is directed to the regulator. By opening the cylinder valves first, you allow the gas to flow into the system without risking an uncontrolled release, as the regulator valves can then be opened to manage the gas pressure effectively.

When the cylinder valves are opened first, it prepares the system for gas flow while keeping the pressure management within safe limits through the regulator. This practice also helps maintain safety by preventing potential gas buildup within the hoses before they can be properly regulated and utilized.

Choosing to open both the cylinder and regulator valves simultaneously can create a hazardous situation that may lead to excessive pressures or leaks, while closing the cylinder valves prematurely wouldn’t allow the gas to flow necessary for the welding operation. Thus, the correct approach is to first close the regulator valves and then proceed to open the cylinder valves, establishing a secure method of gas control for the welding process.