Exam Question
(a) What is the principle of gas cutting? (4)
(b) Describe how gas cutting is carried out with oxygen and acetylene flame? (8)
(c) State the pressure levels for acetylene and oxygen cylinders for gas cutting operations (4)
Class 4 (4th Engineer)
MEP
📅 Mar 2023
Reference Answer
### (a) Principle of Gas Cutting (4 marks)
The principle of gas cutting, specifically oxy-fuel cutting, is a chemical process of rapid, localized, and controlled oxidation of ferrous metals. It is not simply a melting and blowing process.
1. **Pre-heating:** The surface of the steel plate is heated to its kindling or ignition temperature (approximately 870°C, a cherry-red colour) using an oxy-acetylene pre-heating flame. This temperature is critically below the melting point of the steel (approx. 1500°C).
2. **Rapid Oxidation:** Once the kindling temperature is reached, a jet of high-pressure, commercially pure (99.5% or higher) oxygen is directed onto the heated spot. The iron in the steel rapidly oxidizes in an exothermic chemical reaction. The primary reaction is:
The principle of gas cutting, specifically oxy-fuel cutting, is a chemical process of rapid, localized, and controlled oxidation of ferrous metals. It is not simply a melting and blowing process.
1. **Pre-heating:** The surface of the steel plate is heated to its kindling or ignition temperature (approximately 870°C, a cherry-red colour) using an oxy-acetylene pre-heating flame. This temperature is critically below the melting point of the steel (approx. 1500°C).
2. **Rapid Oxidation:** Once the kindling temperature is reached, a jet of high-pressure, commercially pure (99.5% or higher) oxygen is directed onto the heated spot. The iron in the steel rapidly oxidizes in an exothermic chemical reaction. The primary reaction is:
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