A maintenance welder is performing a demolition cut on a rusty, painted steel I-beam using oxy-fuel equipment. They notice that preheating takes an unusually long time, and the cutting action is sporatic, with the flame frequently extinguishing. What is the most likely reason for these difficulties?

Question: A maintenance welder is performing a demolition cut on a rusty, painted steel I-beam using oxy-fuel equipment. They notice that preheating takes an unusually long time, and the cutting action is sporatic, with the flame frequently extinguishing. What is the most likely reason for these difficulties?

Answer options:

• The cutting oxygen pressure is set too high.
• The acetylene pressure is too low for the tip size. ✅ The cutting tip orifice is partially plugged with slag.
• The I-beam material is high carbon steel, requiring more preheat.

Correct answer: The cutting tip orifice is partially plugged with slag.

Explanation: A partially plugged cutting tip orifice (especially the preheat orifices or the cutting oxygen orifice) will restrict gas flow, leading to insufficient preheat flame intensity and poor cutting oxygen jet action, which would cause sporadic cutting and flame extinguishing. While acetylene pressure is important, if the tip is plugged, flow will be affected regardless of proper regulator setting.