Page 29 - CITS - Welder - Trade Theory

WELDER - CITS

Oxy-Acetylene Gas Cutting: Parameters and Faults
Oxy-Acetylene Gas Cutting is a widely used method for cutting metals, offering versatility and efficiency. To
achieve optimal results, it’s essential to understand the key parameters involved in the process and be aware of
common faults that may occur. Here’s an overview:
Cutting Parameters
1 Gas Pressures: Proper adjustment of oxygen and acetylene pressures is critical for effective cutting. The
oxygen pressure typically ranges from 20 to 70 psi, while the acetylene pressure ranges from 5 to 15 psi.
Higher pressures can lead to faster cutting speeds, but excessive pressure may cause overheating and rough
cuts.

2 Cutting Speed: The speed at which the torch moves along the cutting path is crucial. Too slow can result in
excessive heat buildup and slag accumulation, while too fast may lead to incomplete cuts or poor edge quality.
Finding the right balance is essential for achieving clean and precise cuts.
3 Tip Size: The size and type of cutting tip used in the torch affect the width of the cut and the amount of heat
delivered to the work piece. Selecting the appropriate tip size for the material thickness and desired cut quality
is essential for achieving optimal results.
4 Preheating: Preheating the metal before cutting can improve efficiency, especially for thicker materials. Proper
preheating reduces the time required to achieve full penetration and minimizes distortion along the cut edge.
The preheating flame should be adjusted based on the material type and thickness.
5 Torch Angle: Maintaining the correct angle of the torch relative to the work piece is essential for achieving
clean and accurate cuts. Improper torch angle can result in uneven heat distribution, leading to angularity
errors or poor cut quality.

Common faults in cutting
1 Slag Inclusions: Excessive slag buildup along the cut edge is a common issue caused by improper cutting
parameters or torch manipulation. Slag inclusions can weaken the integrity of the cut and require additional
finishing operations to remove.
2 Incomplete Penetration: Insufficient heat or incorrect cutting parameters may result in incomplete penetration
of the metal, leading to a jagged or uneven cut surface. Proper preheating and adjustment of cutting parameters
can help prevent this issue.
3 Warping and Distortion: Overheating or uneven heating of the work piece can cause warping and distortion
along the cut edge, compromising dimensional accuracy and surface finish. Proper preheating and control of
cutting parameters can help minimize this issue.
4 Backfires and Flashbacks: These are safety hazards that occur when the flame travels back into the torch
or hoses. They can be caused by improper gas pressures, leaks, or blockages in the equipment. Regular
maintenance and inspection of equipment are essential for preventing backfires and flashbacks.
By understanding and controlling these parameters while being aware of common faults, operators can achieve
high-quality cuts consistently in oxy-acetylene gas cutting operations. Regular training, proper equipment
maintenance, and adherence to safety protocols are crucial for successful cutting outcomes.

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CITS : C G & M - Welder - Lesson 4&5