MACHINE SHOP 3:

GAS AND ELECTRIC

WELDING
(A Comprehensive Guide for Marine Engineering Students)

3/E Ombao, Ian Jonathan Villaraza

Faculty Member, Department of Maritime Education
 MACHINE SHOP 3
(Gas and Electric Welding)

University of Saint Anthony

Topic
Learning Outcomes
CO 1. Work Permits: Overview
1
Welding Safety
● Potential hazards and risks:
− Radiation
− fumes
− burns
− electric shock
● Emergency procedures
PPE
Risk Assessment

LO1.1: Explain the principles of welding safety based on standard practices

LO 1.2: (LAB) Conduct pre-work safety checks and proper selection of PPE for hot
works in accordance with the Code of Safe Working Practices for Merchant
Seafarers
2. Material Selection considering:
● Compatibility
● Strength
● intended application
Workpiece Preparation as follows:
● Cleaning
● Degreasing
removing any surface contaminants or oxides

LO1.3. (LAB) Perform pre-arc welding preparation processes, such as material

selection and workpiece preparation based on institutional practice
3. Shielded Metal Arc Welding (SMAW)
Principle of shielded metal arc welding

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AC-DC inverter welding equipment

Concept of electric arc formation:
- heat generation
- metal fusion
Types of arc welding
Components of arc welding
Types of welding electrodes
- Process of classification
- Coating
- storage requirement
- selection technique
LO1.4. Explain the principles of Shielded Metal Arc Welding including the different
types of electrodes based on the ISO 3834:2021
4. Arc Welding Equipment
Safe operation
LO1.5. (LAB)Demonstrate the preparation, use, and maintenance of Shielded Metal
Arc Welding equipment and components based on the manufacturer’s manual
LO1.6. Explain the different shielded metal arc welding techniques considering
bead profiles and mechanical properties in accordance with ISO 3834:2021.
5. Tools use in welding
● Welding techniques
● Weaving
● Stringer
● Filler Welding
Types of Welding joints
Position and techniques

LO1.7.Safely perform a straight even bead weld profile on a given flat bar and
maintain a stable arc, ensuring heat control and penetration, with the guidance of the
code of safe working practices.
6. Causes of welding faults:
● Improper Welding Parameters

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● Incorrect Electrodes Section

● Inadequate preparation of the join
● Improper welding technique

Inspection and checking

● Visual inspection
● Mechanical Inspection
● Crack Inspection
● Magnetic inspection
● Ultrasonic inspection
LO1.8. Explain the inspection processes to detect and evaluate welding faults in
accordance with ISO 3834.2021
CO 7. Post-arc Welding Inspection:
1
Common welding faults
− Porosity
− incomplete fusion
− undercutting
− slag
− inclusions
Causes of welding faults:
− improper welding parameters
− incorrect electrode selection
− inadequate preparation of the joint
− improper welding technique
Inspection and checking
− visual inspection
− mechanical inspection
− crack inspection
− magnetic inspection
− ultrasonic inspection

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LO1.9. Explain the inspection processes to detect and evaluate welding faults in
accordance with ISO 3834:2021.
LO1.10. (LAB)Perform electric arc welding inspection in accordance with ISO
3834:2021.
8. Oxy-acetylene welding and cutting techniques
Components of Oxy-acetylene welding equipment
Position and techniques
LO1.11. Explain the principle of oxy-acetylene welding including the different
types of gas based on the ISO 3834:2021.
LO1.12. Explain the different oxy-acetylene welding and cutting techniques
considering bead profiles and mechanical properties in accordance with ISO
3834:2021.
LO1.13. Perform oxy-acetylene welding, cutting and inspection in accordance with
ISO 3834:2021.
9. Soldering and Brazing on Copper Tubes
LO1.14. Safely perform soldering and brazing operation on various dimensions of
copper tubes, with the guidance of the Code of Safe Working Practices
CO 10. Emergency Repair
2
− Concept
− Purpose
− equipment/ machinery failure
Structural damage pipeline leaks precautions and protection
Welding in Difficult Situation
− Aloft
− Overboard
− confined spaces the presence of combustibles materials in adjacent areas
LO 2.1. Describe common emergency repair scenarios where welding may be
necessary
LO2.2. (LAB) Safely perform the emergency repair by fabrication of replacement
pipe using Electric Arc Welding, including leak test with the guidance of the ISO
3834:2021.
CO 11. Oxy-acetylene welding in emergency repairs
2

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LO2.3. (LAB) Safely perform the emergency repair by patching leaks in copper
pipes (tubes) using oxy acetylene welding, including leak test with the guidance of
ISO 3834
CO 12. Soldering/Brazing in emergency repairs
2
LO2.4. (LAB) Safely perform soldering or brazing operation to patch a hole on a
copper plate, and on a tube or pipe with the guidance of the Code of Safe Working
Practices.

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TOPIC 1
WORK PERMITS: OVERVIEW

WELDING SAFETY
Welding is a critical industrial process that involves joining materials, typically
metals, by melting their edges and fusing them together. While welding is essential for many
industries, it can also be hazardous if proper safety measures are not followed. Welding
safety is paramount to protect welders, bystanders, and the environment from potential risks.
Below are the key principles of welding safety based on standard practices:
Training and Education
Welders must receive proper training and education in welding techniques, equipment
operation, and safety procedures. This includes understanding the types of welding processes,
the properties of different metals, and the potential hazards associated with welding.
Personal Protective Equipment (PPE)
Welders should wear appropriate PPE to shield themselves from the various hazards
of welding. Common PPE includes:
1. Welding Helmet with Proper Lens: Protects the eyes and face from intense light,
sparks, and debris. The lens should have the appropriate shade for the welding process
being performed.
2. Safety Glasses with Side Shields: Worn under the welding helmet for additional eye
protection.
3. Flame-Resistant Clothing: Clothing made from flame-resistant materials to protect
against sparks, heat, and UV radiation.
4. Welding Gloves: Heat-resistant gloves that provide protection from burns and sparks.
5. Respiratory Protection: Depending on the welding process, adequate respiratory
protection may be necessary to prevent inhalation of harmful fumes and gases.
Ventilation and Fume Extraction
Adequate ventilation and fume extraction systems are crucial to remove welding
fumes and gases from the work area. Welding fumes can contain toxic substances that, if
inhaled, can lead to serious health issues over time. Local exhaust ventilation should be used
to capture and remove fumes at the source.
Fire Prevention and Protection
Welding involves high temperatures and sparks, which can pose a fire hazard. The
following precautions are essential:
1. Clear the work area of flammable materials.
2. Have a fire extinguisher rated for both electrical and flammable material fires within
easy reach.
3. Use fire-resistant welding blankets to protect surrounding areas from sparks.

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Electrical Safety
Welding equipment uses high currents, and proper electrical safety practices must be
followed:
1. Inspect welding cables and connectors for damage before use.
2. Keep welding cables dry and protected from damage and foot traffic.
3. Ground welding equipment properly to prevent electrical shock.
Safe Work Environment
Maintain a clean and organized work area to prevent tripping hazards and ensure a
clear escape route in case of emergencies.
Preventing Electric Shock
Welders must be aware of the dangers of electric shock. Avoid touching live electrical
parts with bare hands or wet clothing, and always insulate yourself from the workpiece and
ground.
Eye Protection
Intense welding arcs emit harmful UV and infrared radiation that can cause eye
injuries. Properly shaded welding helmets and safety glasses must be worn to protect the
eyes.
Safe Handling of Materials
Be cautious when handling hot materials after welding. Use appropriate tools such as
pliers or tongs to move or manipulate hot metal.
Proper Equipment Setup
Ensure that welding equipment is set up correctly and is in good working condition.
Follow the manufacturer's guidelines for proper equipment setup and maintenance.
First Aid and Emergency Preparedness
Have a first aid kit readily available and ensure that workers are trained in basic first
aid. Additionally, establish an emergency response plan in case of accidents or injuries.
Regular Inspections
Conduct routine inspections of welding equipment, PPE, and the work environment to
identify potential hazards and address them promptly.
Communication
Proper communication among team members is crucial for ensuring safety. Alert
others in the vicinity before starting welding to prevent accidental exposure to hazards.
Adhering to these principles of welding safety is vital to create a secure working
environment for welders and others present in the vicinity. Following industry standards,
regulations, and guidelines can significantly reduce the risks associated with welding
operations.

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TOPIC 2
SHIELDED METAL ARC WELDING
SMAW DEFINITION AND PRINCIPLES
Shielded Metal Arc Welding (SMAW), also known as Manual Metal Arc Welding
(MMA), is a welding process that uses a consumable electrode covered with a flux to create
an electric arc for joining metal pieces. ISO 3834:2021 provides guidelines for ensuring the
quality of welded products. Here are the principles of SMAW and electrode types based on
ISO 3834:2021:
Principles of SMAW:
Electric Arc Generation: SMAW uses a power source to generate an electric arc
between the electrode and the workpiece. This arc produces the heat needed to melt the
electrode and the base metal.
Consumable Electrode: The electrode is made of a metal core that provides the filler
material for the weld. It also has a flux coating that protects the weld from atmospheric
contamination, stabilizes the arc, and adds essential elements to the weld pool.
Shielding Gas: The flux coating on the electrode decomposes during welding,
releasing gases that create a protective shield around the molten metal. This shield prevents
oxidation and other impurities from contaminating the weld.
Manual Operation: SMAW is a manually operated process, with the welder
controlling the movement of the electrode and the welding parameters.
Types of Electrodes (ISO 3834:2021):
ISO 3834 classifies electrodes into various types based on their characteristics and
intended applications:
Rutile Electrodes (Type R): These electrodes have a flux coating containing rutile
(titanium dioxide). They are known for producing welds with good quality and appearance,
making them suitable for general-purpose welding.
Basic Electrodes (Type B): Basic electrodes have a coating that contains calcium
carbonate and calcium fluoride. They are ideal for welding high-strength steel and critical
applications where weld quality and mechanical properties are essential.
Cellulosic Electrodes (Type C): Cellulosic electrodes have a coating with cellulose.
They are often used for welding pipes and are known for their deep penetration, making them
suitable for root passes.
Iron Powder Electrodes (Type I): These electrodes contain iron powder in their
coating, which increases the deposition rate and efficiency. They are commonly used for
welding thick sections and in situations where high productivity is required.
Stainless Steel Electrodes (Type S): These electrodes are designed for welding
stainless steel materials and have a flux coating tailored to prevent chromium carbide
precipitation and ensure corrosion resistance.

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Other Special Electrodes: ISO 3834 may also classify electrodes for specific
applications, such as low-temperature applications, surfacing, or hardfacing.
Selecting the appropriate electrode type is crucial for achieving the desired weld
quality and performance in accordance with ISO 3834 standards. Welders must follow the
recommended procedures and best practices outlined in ISO 3834 to ensure the integrity of
welded products.
AC- DC INVERTER WELDING EQUIPMENT
AC-DC inverter welding equipment is a modern welding technology that offers
versatility and efficiency in various welding applications. This equipment combines an
inverter power source with the ability to switch between alternating current (AC) and direct
current (DC) welding modes. Here's an explanation of AC-DC inverter welding equipment:
Inverter Technology: At the core of this equipment is an inverter, which is an electronic
device that converts the incoming AC power supply into a stable DC power source. It uses
high-frequency switching to achieve this conversion. This DC power is then used to create
the welding arc.
AC and DC Modes:
1. Direct Current (DC): In DC mode, the welding machine produces a steady
current flow in one direction. DC welding is versatile and commonly used for
welding a wide range of metals, including steel, stainless steel, and non-
ferrous materials. It offers good control over the welding process, stable arc
characteristics, and minimal spatter.
2. Alternating Current (AC): AC mode alternates the direction of current flow
at a regular frequency, typically 50 or 60 Hz. AC welding is useful for welding
aluminum and its alloys, as well as for specialized applications like some
types of pipe welding. The alternating current helps break up aluminum oxide
on the surface, allowing for proper fusion.
Versatility: AC-DC inverter welding equipment allows welders to easily switch
between AC and DC modes, making it suitable for a wide range of welding tasks. This
versatility is especially beneficial when working with different materials and thicknesses.
Portability: Inverter welding machines are generally compact and lightweight
compared to traditional transformer-based welding machines. This makes them highly
portable and suitable for both shop and field welding jobs.
Energy Efficiency: Inverter technology is known for its energy efficiency. It can
operate at high frequencies, which reduces energy loss and results in lower power
consumption compared to older transformer-based welding machines.
Advanced Control: Many AC-DC inverter welding machines come with advanced
control features, such as adjustable arc parameters, pulse settings, and waveform control.
These features allow welders to fine-tune their welding process for specific applications and
achieve high-quality welds.
Ease of Use: Inverter welding equipment often includes digital displays and user-
friendly interfaces that make it easier for welders to set and monitor welding parameters.
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Weld Quality: The stable and precise output of AC-DC inverter welding machines
contributes to improved weld quality, reduced defects, and better control over the welding
process.
In summary, AC-DC inverter welding equipment utilizes modern electronic
technology to provide welders with a versatile, energy-efficient, and portable solution for
various welding applications. It offers the flexibility to switch between AC and DC modes,
making it a valuable tool in industries where welding of different materials and specifications
is required.
CONCEPT OF ELECTRIC ARC FORMATION: HEAT GENERATION AND
METAL FUSION
The concept of electric arc formation is fundamental to various welding and metal
joining processes. It involves the creation of an intense, sustained electric discharge or arc
between an electrode and the workpiece. This arc generates the heat necessary for metal
fusion in welding.
Electric Arc Formation: An electric arc is formed when an electric current flows
through a conductive path with a gap, typically between an electrode and a workpiece. The
gap acts as a resistor, creating resistance to the flow of electricity. As a result, electrical
energy is converted into thermal energy in the form of intense heat, light, and ionized gases,
creating the visible arc.
Heat Generation: The primary purpose of the electric arc is to generate an extremely
high temperature at its core. The temperature within the arc can reach several thousand
degrees Celsius, depending on the welding process and the current used. This intense heat is
responsible for melting the edges of the metal pieces being joined.
Metal Fusion: Metal fusion occurs when the heat generated by the electric arc causes
the base metal or the edges of the workpieces to reach their melting points. At these elevated
temperatures, the metal undergoes a phase change from solid to liquid. The molten metal
pools together, forming a weld pool or puddle.
Weld Pool Manipulation: The welder's skill lies in controlling the size and shape of
the weld pool through precise movement of the electrode and the angle at which it is held. By
carefully managing the position and motion of the electrode, the welder ensures proper fusion
between the base metals and controls the final shape and quality of the weld.
Metal Solidification: Once the desired fusion has been achieved, the electric arc is
extinguished. As the molten metal cools, it solidifies and forms a solid weld joint. The
cooling rate and solidification process can influence the mechanical properties and the
microstructure of the welded joint, making it crucial to follow proper welding procedures.
In summary, electric arc formation is the process by which an electric discharge
generates intense heat, leading to the melting and fusion of metal. This fundamental concept
is central to various welding techniques, allowing welders to join metal pieces together
effectively and create strong, durable welds for a wide range of applications, from
construction to manufacturing to aerospace.
TYPES OF ARC WELDING

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Arc welding is a welding process that uses an electric arc to melt and fuse metals
together. There are several types of arc welding methods, each with its unique characteristics
and applications.
Shielded Metal Arc Welding (SMAW) or Stick Welding:
SMAW is one of the oldest and most versatile arc welding processes. It uses a
consumable electrode coated with a flux. The arc is shielded by the flux, which creates a
protective gas cloud, preventing atmospheric contamination.
Stick welding is widely used in construction, maintenance, and repair work. It's
suitable for various metals and can be used in outdoor and adverse weather conditions.
Gas Metal Arc Welding (GMAW) or MIG Welding:
GMAW employs a continuous wire electrode fed through a welding gun. A shielding
gas, typically a mixture of argon and CO2, is used to protect the weld from contamination.
MIG welding is versatile and commonly used in manufacturing, automotive, and
general fabrication due to its high productivity and ability to weld a wide range of metals.
Gas Tungsten Arc Welding (GTAW) or TIG Welding:
GTAW uses a non-consumable tungsten electrode to create the arc. A separate filler
metal may be used if needed. The weld is shielded by a flow of inert gas, often argon.
TIG welding is known for its precision and ability to produce high-quality, clean
welds. It's used in applications where aesthetics and weld quality are critical, such as
aerospace, pipe welding, and artistic welding.
Flux-Cored Arc Welding (FCAW):
FCAW is similar to GMAW but uses a tubular flux-cored wire electrode instead of a
solid wire. The flux inside the electrode provides the shielding gas and can contain alloying
elements.
FCAW is suitable for heavy-duty applications, including structural steel, shipbuilding,
and pipeline welding, thanks to its high deposition rates and deep penetration capabilities.
Submerged Arc Welding (SAW):
SAW is a high-productivity welding process where the arc is submerged beneath a
layer of granular flux. This process is typically mechanized or automated.
SAW is commonly used in welding thick sections of steel in industries like
shipbuilding, pressure vessel fabrication, and bridge construction.
Plasma Arc Welding (PAW):
PAW is a precise welding process that uses a constricted, high-temperature plasma
arc to melt metals. It often requires a separate filler metal.
PAW is used in applications where high precision and control are necessary, such as
aerospace and electronics.

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These are some of the primary types of arc welding, each with its advantages and
suitable applications. Welders select the appropriate method based on the specific
requirements of the welding project, including the type of metal, joint design, thickness, and
desired weld quality.
PROCESS OF CLASSIFICATION, COATING, STORAGE REQUIREMENT AND
SELECTION TECHNIQUE OF SMAW
The Shielded Metal Arc Welding (SMAW) process involves several important
aspects, including classification, electrode coating, storage requirements, and selection
techniques. Let's delve into each of these aspects:
1. Classification of SMAW Electrodes:
SMAW electrodes are classified based on a standardized coding system. For example,
an electrode classification like "E6013" provides essential information:
"E" stands for electrode.
The first two digits (e.g., "60") indicate the tensile strength in thousands of pounds per square
inch (psi).
The third digit (e.g., "1") signifies the welding position for which the electrode is suitable (1
for all positions, 2 for horizontal and flat positions only).
The fourth digit (e.g., "3") indicates the type of electrode coating and power supply (3 for
alternating current, 4 for alternating or direct current).
2. Electrode Coating:
SMAW electrodes have a flux coating that serves multiple purposes:
1. It creates a shielding gas when burned, protecting the weld from atmospheric
contamination.
2. It stabilizes the electric arc, preventing spatter.
3. It adds alloying elements to the weld pool, improving weld quality.
The composition of the flux coating varies depending on the type of electrode, such as
rutile, basic, or cellulosic coatings, each offering specific benefits for different applications.
3. Storage Requirements:
Proper storage of SMAW electrodes is crucial to maintain their performance:
1. Electrodes should be stored in a dry place to prevent moisture absorption, which can
lead to defects and poor weld quality.
2. They should be kept in their original, sealed packaging until ready for use.
3. Electrodes should be stored off the ground on shelves or pallets to prevent contact
with moisture or dirt.
4. Humidity and temperature conditions should be monitored, as some electrodes are
more sensitive to environmental factors than others.
4. Selection Techniques:

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Choosing the right SMAW electrode involves considering factors such as the base
metal, joint design, welding position, and desired weld properties:
1. Base Metal: Select an electrode that matches or is suitable for the base metal's
composition and thickness.
2. Joint Design: Consider the type of joint (e.g., butt joint, fillet joint) and the required
welding position (e.g., flat, horizontal, vertical, overhead).
3. Electrode Diameter: Choose the appropriate electrode diameter for the welding
application, as different diameters provide varying levels of current and heat.
4. Coating Type: Select the electrode coating type (rutile, basic, cellulosic) that best
suits the welding requirements.
5. AWS Classification: Refer to the American Welding Society (AWS) classification
system to ensure you are using the correct electrode for the job.
In summary, SMAW electrode classification, coating, storage, and selection
techniques are vital aspects of the welding process. Welders must understand and apply this
knowledge to ensure the successful execution of welding projects, including proper electrode
choice, storage, and handling for achieving high-quality welds.

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