Millwright Level 1 Practice Exam

What causes a flashback during gas welding?

1. Excessive gas flow

2. Grossly unequal pressures

3. Inadequate oxygen supply

4. Overheating of the tip

The correct answer is: Grossly unequal pressures

A flashback during gas welding is primarily caused by a sudden reverse flow of the flame into the torch or hoses. This phenomenon typically occurs when there is a significant imbalance in pressures within the system. When the pressure of the oxygen in the system is much greater or less than that of the acetylene, it can lead to a condition where the flame follows the path of least resistance back into the equipment, creating a flashback. The presence of highly unequal pressures can create situations where the fuel can effectively be pushed back into the torch and ignite. Maintaining balanced gas pressures is critical to preventing a flashback. Proper setup and adjustment of the equipment ensure that gas flow rates are within safe limits, further minimizing the risk of flashbacks. While excessive gas flow, inadequate oxygen supply, and overheating of the tip can each contribute to other hazards in welding operations, they are not the primary causes of flashbacks caused by pressure imbalance. Understanding the dynamics of gas flow and pressure in welding applications is essential to ensure safety and efficiency in the welding process.