New Mexico Pipe Fitter Journeyman (JPF) Practice Exam

When an icy-acetylene flame has no excess acetylene or oxygen it is called?

1. Carburizing flame

2. Neutral flame

3. Oxidizing flame

4. Inert flame

The correct answer is: Neutral flame

A neutral flame in oxy-acetylene welding is characterized by the balanced ratio of acetylene and oxygen, meaning neither gas is in excess. In this type of flame, the cone of the flame is well-defined, and it produces a clear blue inner cone surrounded by a lighter outer envelope. This flame achieves optimal combustion of the gases, providing the right temperature for welding without altering the chemical composition of the base metals being worked on. It is ideal for most welding applications, especially when working with ferrous and nonferrous metals, as it prevents oxidation or carbonization of the weld area. In contrast, the other types of flames represent different ratios of the gases. A carburizing flame, for example, has an excess of acetylene, leading to a flame that has a reducing effect, which can introduce carbon into the metal being welded. An oxidizing flame, on the other hand, has an excess of oxygen, which can lead to oxidation of the weld and discoloration. An inert flame usually refers to a flame produced by gases like argon or helium, not typically associated with oxy-acetylene processes. Understanding these different flame types is crucial for pipe fitters and welders to ensure they are using the appropriate flame for their specific applications.