The picture below shows a plasma cutting machine - NSC Agricultural Technology - Question 4 - 2016 - Paper 1
Question 4
The picture below shows a plasma cutting machine. Answer the questions that follow.
4.1.1 Explain what will happen when water enters the torch of the plasma cutter ... show full transcript
Worked Solution & Example Answer:The picture below shows a plasma cutting machine - NSC Agricultural Technology - Question 4 - 2016 - Paper 1
Step 1
Explain what will happen when water enters the torch of the plasma cutter nozzle.
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Answer
When water enters the torch of the plasma cutter nozzle, it can cause internal arcing or a short circuit. This arcing can lead to damage of the nozzle and affect the cutting efficiency, resulting in an inconsistent or poor quality cut.
Step 2
Give TWO reasons for using the welding helmet when doing plasma cutting.
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The visor blocks the ultraviolet rays emitted during the cutting process, protecting the eyes.
It safeguards the face and eyes against flying sparks and molten metal that can be hazardous.
Step 3
Identify the nozzle that is used for plasma cutting.
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The nozzle used for plasma cutting is identified as nozzle C.
Step 4
Name TWO kinds of wear that the bucket of the front-end loader may be subjected to when working.
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Metal against metal friction leading to wear on the bucket edges.
Serious impacts from rocks or heavy debris causing dents and structural fatigue.
Step 5
State THREE preventative measures to control distortion of the welded joints.
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Utilize pre-setting to ensure proper alignment before welding.
Execute welding of patch work to minimize heat concentration.
Implement spot welding to control the amount of thermal input.
Step 6
State THREE factors that influence the amount of distortion of a welded joint.
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The number of welding runs can impact heat accumulation.
The degree of resistance of the materials being welded affects how heat is transferred.
The original state or condition of the parts to be welded can influence distortion.
Step 7
Draw TWO labelled sketches to indicate the difference between a horizontal arc welding butt joint and a vertical arc welding butt joint.
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A horizontal arc welding butt joint will typically have the weld pattern on the side while a vertical arc welding butt joint will display the weld running vertically, often requiring a V-groove to manage the bead.
Step 8
Describe the procedure that must be followed to cut a 10 mm steel plate when using the oxyacetylene apparatus.
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Set the flame to cutting mode.
First bring the material to red hot.
Oxygen should be released with the lever to cut.
The steel melts to form a liquid that is cleared by pressure from the oxygen stream.
Follow safety regulations throughout the process.
Step 9
Identify which gauge (A or B) above is used for MIG welding.
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Gauge B is used for MIG welding.
Step 10
Describe the factors that must be considered when MIG welding is done on galvanised steel.
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The galvanising must be removed prior to welding as it can interfere with the arc.
The fumes produced during welding galvanised steel can be toxic, requiring protective gear.
Suitable ventilation must be ensured to prevent harmful gas buildup.
Step 11
State THREE disadvantages of MIG welding.
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MIG welding is generally limited to thin to medium thickness metal.
The use of inert gas cylinders makes this method less portable.
Higher equipment setup costs and maintenance are required.
Step 12
Calculate how many welding rods the welder needs to complete the job.
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To calculate the number of welding rods required:
Circumference of the pipe = π x diameter = 3.14 x 100 mm = 314 mm.
The distance to be welded is 105 mm.
Therefore: 314 mm / 105 mm ≈ 2.99, which rounds up to 3 welding rods.
Step 13
Design and draw a neat freehand sketch of a two-station arc welding work table.
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The work table should include a safety screen to protect against sparks and should be built to accommodate two welding stations. The dimensions and labels should indicate the height, width, and safety features prominently.
