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The heavy steel pipe shown is first rolled into shape and is to be completed by welding - Leaving Cert Engineering - Question 5 - 2017
Question 5
The heavy steel pipe shown is first rolled into shape and is to be completed by welding. (a) (i) Select a suitable automated welding process for joining the seams a... show full transcript
Worked Solution & Example Answer:The heavy steel pipe shown is first rolled into shape and is to be completed by welding - Leaving Cert Engineering - Question 5 - 2017
Step 1
Select a suitable automated welding process for joining the seams along the length of the heavy steel pipe. Justify your selection.
Answer
The most suitable automated welding process for this application is Submerged Arc Welding (SAW). SAW is known for its ability to produce high-quality welds at high speeds, making it ideal for thick steel structures like large pipes.
Justification:
- Efficiency: SAW allows for continuous welding, which is crucial for lengthy welds on pipelines.
- Quality: The process is shielded from atmospheric contamination, reducing defects such as porosity.
- Cost-effectiveness: Lower production costs are achieved due to minimal handling and rework.
- Minimal Heat Affected Zone: This results in enhanced structural integrity and reduced warping.
Step 2
Describe, with the aid of diagram(s), the main principles of operation for the selected welding process.
Answer
Submerged Arc Welding (SAW) operates using a bare wire electrode that is fed automatically from a spool. The main components are:
- Electrode: Acts as the filler material, melting during the welding process.
- Flux: A mixture of minerals that cover the weld pool, protecting it from contaminants and providing insulation.
- Control Unit: Regulates the power to ensure consistent welding parameters.
Principles of Operation:
- Welding Preparation: The heavy steel pieces are positioned and prepared for welding.
- Electrode Feeding: The bare electrode is continuously fed into the weld area, where it is melted by the heat generated from the arc.
- Flux Coverage: The flux covers the weld area and absorbs any excess molten metal, forming a slag that can be removed after cooling.
Diagram: It is important to provide a diagram showing these components and their arrangement during the welding process.
Step 3
Describe the term dissolved acetylene.
Answer
Dissolved acetylene refers to acetylene gas that is stored under pressure in a cylinder, dissolved in acetone. This method is employed to make acetylene safer to handle, as the gas is highly flammable and unstable at atmospheric pressure. In this form, acetylene can be absorbed effectively, allowing for controlled release when needed for various applications, such as oxy-acetylene welding.
Step 4
Outline the reasons for porosity in welding.
Answer
Porosity in welding can arise due to several factors:
- Moisture and Contaminants: Presence of water or oil on the base materials can lead to gas bubbles in the weld pool.
- Poor Shielding: Inadequate gas shielding can cause atmospheric gases to become entrapped in the molten metal, leading to voids in the weld.
- Improper Welding Parameters: Incorrect heat settings can result in unstable weld pools, causing gas to become trapped.
Step 5
Describe two hazards which may be encountered in underwater welding.
Answer
Underwater welding involves significant risks, such as:
- Electrical Hazards: The risk of electric shock due to wet conditions and faulty equipment, which can result in serious injury or death.
- Decompression Sickness: Rapid ascent can cause nitrogen bubbles to form in the diver's bloodstream, leading to life-threatening conditions if not properly managed.
Step 6
Outline three safety features integrated into oxy-acetylene welding equipment.
Answer
Important safety features of oxy-acetylene welding equipment include:
- Colour Coding of Cylinders: Oxygen and acetylene cylinders are colored distinctly to prevent mix-ups.
- Flashback Arrestors: These devices prevent flames from traveling back into the cylinders, reducing the risk of explosions.
- Pressure Relief Valves: These valves are designed to relieve excess pressure in the cylinder, ensuring safety during operation.
Step 7
Give two benefits of using resistance seam welding in the production of house radiators.
Answer
Benefits of using resistance seam welding in the production of house radiators include:
- Automated Process: The technique is highly automated, making it suitable for mass production and ensuring consistency in quality.
- Cost Efficiency: This method reduces production costs due to faster cycle times and less material waste.
Step 8
The transformer-rectifier circuit used in manual metal arc welding.
Answer
The transformer-rectifier circuit converts high voltage AC electricity from the mains to a lower voltage suitable for welding.
Components:
- Transformer: Steps down the voltage, making it safe for welding.
- Rectifier: Converts AC to DC by allowing current to flow only in one direction, providing a stable power supply.
- Capacitor: Smooths out the current output to ensure a steady arc.
Diagram: Inclusion of a schematic diagram showing the interaction between these components is essential.
Step 9
The essential differences between Metal Inert Gas (MIG) welding and Tungsten Inert Gas (TIG) welding.
Answer
MIG and TIG welding are both inert gas welding methods, yet they have distinct differences:
- Electrode Type: MIG uses a consumable wire electrode, while TIG uses a non-consumable tungsten electrode.
- Filler Material: MIG directly feeds filler into the weld pool, whereas in TIG, the operator can manually add filler as needed.
- Weld Pool Control: TIG allows for greater control over the weld pool, making it preferable for thin materials and intricate work, while MIG is more suited for thicker materials and faster production.