Machining Level I: Flame Cutting and Welding
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Questions and Answers

What is the primary purpose of using a gas pressure regulator?

  • To filter impurities from the gas
  • To allow the gas to be stored at higher temperatures
  • To increase the gas pressure to cylinder levels
  • To provide a steady flow of gas under varying pressures (correct)

What should be the maximum operating pressure for acetylene at the welding torch?

  • 35 psig
  • 25 psig
  • 15 psig (correct)
  • 10 psig

What happens if an acetylene cylinder is laid down?

  • The gas stabilizes effectively
  • There is no effect on the gas
  • It may cause the gas to become unstable (correct)
  • The cylinder pressure increases

Which type of regulator is commonly used for both oxygen and acetylene in oxyacetylene welding?

<p>Single stage regulator (A)</p> Signup and view all the answers

What is a consequence of using a single stage regulator in cold weather?

<p>It may freeze due to rapid cooling (B)</p> Signup and view all the answers

What are the two pressure gauges on a pressure regulator used for?

<p>To indicate cylinder pressure and reduced pressure (C)</p> Signup and view all the answers

What is a defining feature of a two stage regulator compared to a single stage regulator?

<p>It reduces pressure in multiple stages (B)</p> Signup and view all the answers

What pressure should an oxygen regulator typically be set to at the welding torch?

<p>35 psig (D)</p> Signup and view all the answers

What is the primary purpose of a check valve in welding equipment?

<p>To prevent flame or gas mixture backflow (B)</p> Signup and view all the answers

What is a notable advantage of using a high pressure blow torch?

<p>It does not suffer from backfires as much as others. (A)</p> Signup and view all the answers

Which of the following can cause a backfire in a welding torch?

<p>Dirty or damaged tip (C)</p> Signup and view all the answers

Which factor is NOT important in selecting the appropriate welding nozzle?

<p>The color of the welding torch. (C)</p> Signup and view all the answers

What occurs during a flashback?

<p>Flame traveling backward into hoses and cylinder (D)</p> Signup and view all the answers

How can flashbacks be prevented in welding equipment?

<p>By installing a flash arrestor (B)</p> Signup and view all the answers

What determines the size of a welding tip?

<p>The diameter of the opening or orifice in the tip. (C)</p> Signup and view all the answers

To achieve a greater amount of heat when welding, what adjustment is required?

<p>Increase the orifice size. (A)</p> Signup and view all the answers

What type of welding torch is suitable for use with acetylene dissolved in cylinders at 117 psi?

<p>High pressure type (A)</p> Signup and view all the answers

What should be done to maintain the welding tips properly?

<p>Clean the nozzle orifice with specially designed tip cleaners. (C)</p> Signup and view all the answers

What situation could cause the flashback arrestor to remain inactive?

<p>When reset by a user (C)</p> Signup and view all the answers

How does acetylene behave under excessive temperatures or pressures?

<p>It decomposes (B)</p> Signup and view all the answers

What is the role of filler metals in welding?

<p>To supply additional material to the weld pool. (B)</p> Signup and view all the answers

What might happen if welding tips are handled carelessly?

<p>They can easily get damaged. (B)</p> Signup and view all the answers

Which of the following describes a low pressure blowpipe?

<p>Uses acetylene at approximately 0.3 psi (B)</p> Signup and view all the answers

What is commonly provided by manufacturers to guide proper welding tip usage?

<p>A chart giving sizes of tips and pressures used. (C)</p> Signup and view all the answers

What is the relationship between nozzle size and metal thickness in welding?

<p>Larger nozzles are appropriate for thicker metals. (C)</p> Signup and view all the answers

What may occur if welding thick metal using a small nozzle with increased gas pressure?

<p>The flame may leave the end of the nozzle. (C)</p> Signup and view all the answers

What indicates that the gas pressure is too low when using an oversized nozzle?

<p>Small explosions at the nozzle. (C)</p> Signup and view all the answers

How should nozzle sizes and gas pressures be determined for a specific application?

<p>According to the manufacturer's recommendations. (D)</p> Signup and view all the answers

What is the optimal flame condition for welding?

<p>A soft flame. (A)</p> Signup and view all the answers

What is indicated by the size designation '20' for a welding nozzle?

<p>2 mm diameter. (B)</p> Signup and view all the answers

Why should one consult the manufacturer's information regarding nozzle sizes?

<p>It can vary with different makes of blowpipe. (A)</p> Signup and view all the answers

What happens if gas supply is reduced at the blowpipe valves instead of changing to a smaller nozzle?

<p>It leads to small explosions at the nozzle. (C)</p> Signup and view all the answers

What is the primary purpose of liquid penetrate inspection?

<p>To examine surface defects only (A)</p> Signup and view all the answers

Which group of liquid penetrates is NOT water washable?

<p>Group I (D)</p> Signup and view all the answers

What is the first step before using a liquid penetrate on a weld?

<p>Remove all slag, rust, paint, and moisture (A)</p> Signup and view all the answers

What temperature range should be maintained for the inspection piece and the liquid penetrate?

<p>50°F to 100°F (B)</p> Signup and view all the answers

Why is it important to remove all traces of the cleaning material before inspection?

<p>To prevent contamination of the liquid penetrate (C)</p> Signup and view all the answers

What should be done if a specific finish is required after the inspection?

<p>Perform a final liquid penetrate inspection after the finish (D)</p> Signup and view all the answers

What cleaning method is recommended for preparing a surface before using a liquid penetrate?

<p>Dipping the piece into a solvent or swabbing with a cloth (A)</p> Signup and view all the answers

What is a significant hazard to avoid when maintaining temperature for liquid penetrates?

<p>Using an open flame to increase temperature (B)</p> Signup and view all the answers

What gases are combined in the oxyacetylene welding process?

<p>Oxygen and acetylene (A)</p> Signup and view all the answers

What is the maximum temperature that the oxyacetylene gas mixture can reach?

<p>5800°F (C)</p> Signup and view all the answers

What determines the proper welding tip size to be used in oxyacetylene welding?

<p>Metal thickness and joint design (A)</p> Signup and view all the answers

Which of the following best describes the purpose of adding a filler metal alloy in the oxyacetylene welding process?

<p>To enhance the flow of molten metal (B)</p> Signup and view all the answers

In oxyacetylene welding, what is the role of regulators?

<p>To control gas flow and reduce pressure (A)</p> Signup and view all the answers

What feature allows for a quick change from welding to cutting in oxyacetylene operations?

<p>Changing the welding tip to a cutting tip (A)</p> Signup and view all the answers

What is the function of double line rubber hoses in the oxyacetylene process?

<p>To deliver gas from tanks to torch safely (B)</p> Signup and view all the answers

In oxyacetylene welding, which factor is NOT crucial in affecting the amount of heat applied to the metal?

<p>Type of filler metal (D)</p> Signup and view all the answers

Flashcards

What are key characteristics of Acetylene Cylinders?

Acetylene cylinders are typically short and wide, holding gas at a pressure of 250 PSI when full. They should only be opened 3/4 of a turn and never laid down to prevent instability.

What is a pressure regulator's function?

Pressure regulators are used to decrease the high pressure from gas cylinders to a usable pressure for welding. They provide a stable gas flow, even with varying levels in the cylinder.

What is a single-stage regulator?

A single-stage regulator reduces the pressure in one step, directly from the cylinder pressure to the welding pressure. This is typically sufficient for oxygen and acetylene, but can freeze in cold weather due to rapid gas expansion and cooling.

What is a two-stage regulator?

A two-stage regulator reduces the pressure in two steps, first to an intermediate pressure and then to the final welding pressure. This provides better temperature control and stability, especially in cold conditions.

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Check Valve

A safety device that prevents the flame or fuel mixture from being pushed back into the cylinder, which could cause a dangerous backfire, flashback, or explosion.

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Flashback

A sudden, unexpected ignition of the fuel-oxygen mixture within the torch, tip, or hose, caused by improper gas mixture or backfire.

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Flashback Arrestor

A safety device that prevents the shock waves from a flashback from entering the cylinder, potentially rupturing it.

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Backfire

A hazardous event where the flame in a welding torch extinguishes suddenly, potentially causing a flashback.

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Welding Torch

The process of mixing oxygen and acetylene gases in the desired proportions to produce a welding flame.

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High Pressure Welding Torch

A type of welding torch that uses acetylene stored in cylinders under high pressure (117 psi).

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Low Pressure Welding Torch

A type of welding torch that uses acetylene supplied from a generator at low pressure (0.3 psi).

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Mixer

The mixing chamber within a welding torch where oxygen and acetylene gases are combined.

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Oxyacetylene Welding

A welding process that uses a combination of oxygen and acetylene gas to create a high-temperature flame and melt metal to join pieces together.

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Filler Metal

A filler metal alloy that is added during oxyacetylene welding to prevent oxidation and help metals bond together.

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Heat Input

The amount of heat applied to a metal during oxyacetylene welding, determined by factors such as tip size, welding speed, and position.

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Welding Tip

The part of the welding torch that controls the size of the flame used in oxyacetylene welding.

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Cutting Flame

A type of welding flame where the oxygen and acetylene gas mixture ratio is adjusted for cutting metal by creating a high-temperature concentrated jet.

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Regulators

Devices used to regulate the flow of oxygen and acetylene gas during oxyacetylene welding, ensuring proper pressure and control.

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Double Line Rubber Hoses

Rubber hoses used to safely transport oxygen and acetylene gas from the cylinders to the welding torch.

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Temperature Regulation

The ability to adjust the flow of oxygen and acetylene gases to precisely control the temperature of the flame during oxyacetylene welding.

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Welding

The process of joining two metal pieces using heat and filler metal, often employing a welding torch.

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Welding Nozzle

The part of the welding torch that controls the amount of heat output by controlling the flow of gases.

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Welding Nozzle Size

The size of the opening in the welding nozzle, which determines the amount of gas flow and heat output.

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Adjusting Welding Torch Power

Controlling the welding torch by adjusting the nozzle size and gas pressures to achieve the desired heat output.

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Factors for Welding Nozzle Selection

The position of the weld joint, the type of joint, the metal thickness, and the type of metal being welded.

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Care of Welding Nozzles

Copper welding nozzles are delicate and need proper care to avoid damage.

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Liquid Penetrant Inspection (LPI)

A non-destructive testing method used to reveal surface defects in metals by using a colored liquid that penetrates the defect.

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LPI vs. Magnetic Particle Inspection (MPI)

LPI reveals only surface-breaking defects. Unlike magnetic particle inspection, which can detect subsurface defects.

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Surface Preparation for LPI

Remove all foreign matter from the inspection area before using LPI.

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Types of LPI Materials

LPI Group I is dye penetrant that is not water washable, Group II is water washable, and Groups III & IV are fluorescent penetrants.

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LPI Procedures

Follow the specific instructions for each type of penetrant, as procedures and safety precautions vary.

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Temperature Control in LPI

Ensure proper temperature control during the inspection process.

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Ideal Temperature Range for LPI

Maintain the temperature of the inspection piece and the liquid penetrant between 50°F and 100°F.

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Fire Hazard in LPI

Avoid using open flames to increase temperature as some LPI materials are flammable.

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Nozzle Size and Metal Thickness

The size of the welding nozzle is directly related to the thickness of the metal being welded. A larger nozzle is needed for thicker metal to provide sufficient heat.

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High Gas Pressure

Smaller nozzles with higher gas pressures can cause the flame to detach from the nozzle, making a loud and unstable flame.

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Low Gas Pressure

Larger nozzles with lower gas pressures can cause small explosions at the nozzle due to gas buildup and pressure imbalance.

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Proper Nozzle Selection

Using a nozzle that is too small or too large for the metal thickness can create unstable flames, cause explosions, or make it impossible to achieve a proper weld.

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Manufacturer's Instructions

Always refer to the manufacturer’s instructions regarding nozzle sizes and gas pressures for specific applications.

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Flame Heat

The amount of heat supplied by the flame is determined by the nozzle size and gas pressure.

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Soft Flame

A 'soft' flame is a stable and controlled flame, achieved by using the correct combination of nozzle size and gas pressure.

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Nozzle Size Measurement

Nozzle sizes are typically measured in tenths of a millimeter.

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Study Notes

Machining Level I Module

  • Module Title: Perform flame Cutting and welding.
  • Module code: IND MAC1 M 07 0322
  • Nominal duration: 50 hours
  • Prepared by: Ministry of Labour and Skill
  • Date: August, 2022
  • Location: Addis Ababa, Ethiopia

Table of Contents

  • Introduction to the module: Oxy-fuel welding, also known as oxy-welding or gas welding, is a metal joining process using a high-temperature flame created by mixing oxygen and acetylene gases.
  • Unit one: cutting welding and operations: This unit covers welding and cutting requirements, welding equipment and consumables, and material preparation.
  • 1.1. Welding and cutting requirements: This section describes the characteristics of the oxy-acetylene welding process, including its use of dual gases, its ability to quickly switch to a cutting process, the high temperature it attains, the use of regulators and tanks, melting of materials, and adjustable gas flow. It also defines different flame types: neutral, oxidizing, and reducing (carburized).
  • 1.2. Welding equipment and consumables: This unit covers cylinders (oxygen and acetylene), pressure regulators, gas hoses, and clamps. It also includes safety precautions and important details about each of these items.
  • Unit Two: Set up oxyacetylene cutting outfit and welding: This unit covers assembling and setting up equipment, welding symbols and working pressure.
  • 2.1. Welding symbols: This unit details the elements of a welding symbol including the reference line, arrow, basic weld symbol, dimensions, supplementary symbols, finish symbols, and specifications.
  • 2.2 Assembly and setup of cutting equipment: This unit provides procedures for assembling and setting up oxy-acetylene welding equipment and includes safety checks for cylinders, hoses, and valves.
  • Unit Three: Perform Cutting and welding using oxyacetylene: This unit covers cutting positions, component inspection, before weld cleaning, welding, and post-welding cleaning, and OHS procedures.
  • 3.1. Cutting and Welding Positions: This unit describes horizontal, vertical, and overhead welding positions, plus considerations for each.
  • 3.2. Components inspection: This unit mentions the general visual inspection procedures.
  • 3.3 Before weld cleaning: This unit explains various methods for cleaning metal prior to welding, including sandpaper, abrasive blasting, and wire brushes. Chemical cleaning methods are mentioned.
  • Unit Four: Assure quality and clean up: This unit covers inspection of weld seams, cleaning methods, and quality assurance procedures, plus details on NDT (Nondestructive Testing) methods such as visual inspection, magnetic particle inspection, liquid penetrate inspection, radiographic inspection, and eddy current testing.
  • 4.1. Cleaning and inspection of weld seams: This unit details preparation for the next weld pass and cleaning the weld area from slag, flux, loose scale, oil, and dirt. Inspection methods, such as visual inspections, are also shown.

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M-07 Perform Flame cutting and welding PDF

Description

Explore the essential techniques and processes of flame cutting and welding in this comprehensive module. You'll learn about oxy-fuel welding, equipment requirements, and the characteristics of the welding process. This course is designed for individuals looking to enhance their skills in metal joining.

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