The picture below shows a plasma cutting machine - NSC Agricultural Technology - Question 4 - 2016 - Paper 1

1. The welding helmet protects the operator's face and eyes against intense ultraviolet and infrared rays emitted during plasma cutting, which can cause serious eye damage.

2. It acts as a barrier against harmful sparks and debris that are generated throughout the cutting process, ensuring the safety and well-being of the operator.

The correct nozzle for plasma cutting can be identified as option C.

1. Metal against metal friction, which can cause wear on the edges and surface of the bucket over time.

2. Serious impact from heavy objects or surfaces, leading to scraping, which can produce dents and bends in the bucket structure.

1. Pre-setting parts can ensure alignment before welding, helping to minimize distortion caused by heat.

2. Employing the welding of patch work can reduce the overall heat input in the affected areas, thereby controlling distortion.

3. Utilizing spot welding techniques can help to control the amount of heat introduced into the material, preventing significant distortion.

1. The number of welding runs can affect heat distribution, influencing how much the material will distort.

2. The degree of resistance of the materials being welded can also impact the amount of heat generated.

3. The thickness of the metal plays a crucial role, as thicker materials tend to resist changes in shape more than thinner ones.

For the horizontal arc welding butt joint, the sketch should show a straight joint configuration with a V-groove that extends downwards. In contrast, the vertical arc welding butt joint should illustrate a joint with a similar V-groove, but oriented in an upright position.

Both sketches should be correctly labelled to indicate the configurations clearly.

1. Set the flame to cutting mode, ensuring the correct proportions of oxygen and acetylene are used.

2. Begin by preheating the steel plate to red hot, which prepares the metal for the cutting process.

3. Increase the oxygen supply with the lever on the cutting attachment to initiate the cutting.

4. The molten iron liquid that results from the cut is cleared by the pressure from the oxygen stream.

5. Follow all safety regulations to prevent accidents during the operation.

Gauge B is used for MIG welding.

1. Galvanising must be removed prior to welding as it disrupts the welding process and may lead to contamination.

2. The presence of galvanising can complicate the arc and make welding more difficult.

3. Gases created when welding galvanised steel are hazardous, which necessitates the use of a gas mask to protect the welder from inhalation.

1. MIG welding is typically limited to thin to medium thickness metals only.

2. The process requires the use of an inert gas cylinder, which can hinder portability.

3. MIG welding is usually less efficient in settings requiring high-duty cycle demands.

To find the number of welding rods needed, we apply the circumference of a circle formula:

$ext{Circumference} = ext{π} imes ext{diameter} = 3.14 imes 100 = 314 ext{ mm}$

Next, divide the total circumference by the length of weld per rod:

rac{314 ext{ mm}}{105 ext{ mm}} ext{ = 2.99}

Since we cannot use a fraction of a welding rod, we round up to 3 rods needed to complete the job.

The drawing should include a robust design with two distinct stations for arc welding.

• Dimensions: Ensure each station is adequately spaced and contains a welding surface.
• Safety Aspect: Incorporate a safety screen to protect operators and other workers from harmful rays.
• Labels: Clearly label each component of the diagram, including the safety screen, welding surface, and measurements.