Saudi Aramco Interview Questions for Welding Inspector PDF

This article is about Saudi Aramco Interview Questions for Welding Inspector.

Saudi Aramco Interview Questions for Welding Inspector

31) Mention the drying temperatures for low hydrogen Shielded Metal Arc Welding (SMAW) electrodes.

Answer: The drying temperatures for low hydrogen SMAW electrodes vary depending on the specific classification. Here are the general drying temperature ranges:

SFA A5.1: Low hydrogen electrodes – 260-430°C (500-800°F) for a minimum of 2 hours.
SFA A5.5: Low hydrogen iron powder electrodes – 370-430°C (700-800°F) for a minimum of 2 hours.
Stainless steel and non-ferrous electrodes – 120-250°C (250-480°F) for a minimum of 2 hours.

These drying temperatures are important to ensure that moisture and hydrogen are eliminated from the electrode coating, as excessive moisture can lead to hydrogen-induced cracking during welding.

32) What are the test positions for groove welds?

Answer:
Plate Positions:

1G: Flat Position (Welding is done on a horizontal surface)
2G: Horizontal Position (Welding is done on a vertical surface, with the weld axis in a horizontal plane)
3G: Vertical Position (Welding is done on a vertical surface)
4G: Overhead Position (Welding is done on the underside of a horizontal surface)

Pipe Positions:

1G: Flat Position (Pipe axis is horizontal, and welding is done with the pipe rolled during welding so that the weld metal is deposited from above)
2G: Horizontal Position (Pipe axis is vertical, and welding is done with the weld axis in a horizontal plane; the pipe is fixed)
5G: Multiple Positions (Pipe axis is horizontal, and the weld groove is in a vertical plane; the pipe is fixed)
6G: Multiple Positions (Pipe with its axis inclined at a 45-degree angle to the horizontal; the pipe is fixed)

These test positions are used to evaluate a welder’s ability to perform welding in various orientations and are commonly used in qualification tests.

33) What are the test positions for fillet welds?

Answer:
Plate Positions:

1F: Flat Position (Welding is done on a horizontal surface)
2F: Horizontal Position (Welding is done on a vertical surface, with the weld axis in a horizontal plane)
3F: Vertical Position (Welding is done on a vertical surface)
4F: Overhead Position (Welding is done on the underside of a horizontal surface)

Pipe Positions:

1F: Flat Position (Pipe axis is horizontal, and welding is done on a horizontal surface)
2F and 2FR: Horizontal Position (Pipe axis is vertical, and welding is done on a vertical surface or in a horizontal position with a fillet weld on the top side)
4F: Overhead Position (Welding is done on the underside of a horizontal surface)
5F: Multiple Position (Pipe axis is horizontal, and the weld groove is in a vertical plane)

These test positions are used to evaluate a welder’s ability to perform fillet welds in various orientations and are commonly used in qualification tests.

34) What are the types of mechanical tests?

Answer:
There are several types of mechanical tests performed to evaluate the mechanical properties of welded joints and materials. Here are some common types of mechanical tests:

Tension Tests: Tensile tests are conducted to measure the tensile strength, yield strength, and elongation of a material. A test specimen is subjected to axial pulling forces until it fractures.
Guided Bend Tests: Guided bend tests assess the ductility and soundness of a weld. A specimen is bent to a specified angle and examined for any cracks or defects.
Fillet Weld Tests: Fillet weld tests evaluate the quality and strength of fillet welds. The specimen is subjected to tensile or bending forces to assess the integrity of the weld.
Notch Toughness Test: Notch toughness tests, such as Charpy V-notch or Izod impact tests, measure the ability of a material to absorb energy and resist fracture under impact loading.
Stud Weld Test: Stud weld tests verify the strength and integrity of stud welds used in various applications. The weld is evaluated based on its load-carrying capacity and resistance to failure.

35) What is the equation for carbon equivalent?

Answer:
The carbon equivalent (CE) is a calculated value used to estimate the hardenability and weldability of steels. The equation for carbon equivalent is as follows:

CE = C + (Mn)/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

Where:

C represents the carbon content of the steel.
Mn represents the manganese content of the steel.
Cr, Mo, V represent the chromium, molybdenum, and vanadium content, respectively.
Ni, Cu represent the nickel and copper content, respectively.

The carbon equivalent is a useful parameter for assessing the susceptibility to cracking during welding and determining the appropriate preheat and heat treatment requirements.

36) What is the equation for heat input?

Answer:
The equation for heat input (H) is commonly used to calculate the amount of heat energy applied during welding. The equation is as follows:

H = 60EI / 1000S

Where:

H represents the heat input measured in kilojoules per millimeter (kJ/mm).
E represents the arc voltage in volts.
I represents the welding current in amperes.
S represents the travel speed in inches per minute.

The heat input calculation is important for controlling the heat input during welding processes, as it can influence the microstructure, mechanical properties, and distortion of the welded joint.

37) What are the different factors that cause hydrogen-induced cracking (HIC)?

Answer:
Hydrogen-induced cracking (HIC) is a type of cracking that occurs in metals due to the presence of hydrogen. Several factors contribute to the occurrence of HIC, including:

Sensitive Microstructure: Certain microstructures, such as those found in some steels, can be more susceptible to HIC due to their composition and grain structure.
Sufficient Level of Hydrogen: The presence of hydrogen, either from the welding process or environmental sources, can contribute to the formation of hydrogen-induced cracks. Hydrogen can enter the material during welding, corrosion, or exposure to hydrogen-containing substances.
High Level of Stress: Residual stresses or applied stresses acting on the material can promote the initiation and propagation of hydrogen-induced cracks. High-stress areas in the welded joint or components can be particularly vulnerable to HIC.

Controlling these factors through proper welding techniques, material selection, preheating, and post-weld heat treatment is essential to minimize the risk of hydrogen-induced cracking in welded structures.

38) Advantages of Argon vs. Helium as shielding gas:

Argon:

Good arc starting: Argon provides a stable arc with easy ignition.
Good cleaning action: It helps remove oxides and impurities from the weld zone.
Good arc stability: Argon promotes a steady and controlled arc.
Focused arc cone: The arc is concentrated and precise.
Lower arc voltage: Argon requires lower voltage for operation.
Moderate flow rate: Argon typically requires a flow rate of 10-30 cubic feet per hour (cf/h).
Cost-effective: Argon is generally more affordable compared to helium.

Helium:

Faster travel speeds: Helium allows for faster welding speeds.
Increased penetration: Helium provides deeper penetration into the base metal.
Higher arc voltages: Helium requires higher voltages for operation.
Higher flow rates: Helium typically requires twice the flow rate compared to argon.
Suitable for certain applications: Helium is commonly used for welding thick sections and non-ferrous metals.
Higher cost: Helium is generally more expensive than argon.

Argon/Helium Mix:

Improved travel speed and penetration: The mix combines the advantages of both gases for enhanced welding performance.
Closer cleaning properties to argon: The mix provides better cleaning action compared to using pure helium.
Improved arc starting and stability: The mix offers improved ignition and arc stability compared to pure helium.
Focused arc cone: The arc cone shape is more concentrated compared to pure helium.
Higher flow rate: The mix generally requires a higher flow rate than pure argon.
Higher cost: The cost of the argon/helium mix is higher than using pure argon.

39) What are the general types of welding and joining processes?

There are several general types of welding and joining processes, which can be classified as follows:

Fusion:

Arc welding: Uses an electric arc to melt and join metals, such as shielded metal arc welding (SMAW), gas metal arc welding (GMAW/MIG), and tungsten inert gas welding (GTAW/TIG).
Gas welding: Utilizes a flame generated by a fuel gas and oxygen to heat and join metals, such as oxy-fuel welding and cutting.
Power beam welding: Involves using high-energy beams, such as lasers or electron beams, to melt and join metals.
Resistance welding: Joins metals by applying pressure and passing an electric current through the workpieces, such as spot welding and seam welding.

Thermo-mechanical:

Friction welding: Creates heat through friction between two workpieces to join them.
Flash welding: Generates heat by resistance heating and subsequent flashing off of the molten material to join the workpieces.

Mechanical:

Fasteners: Uses mechanical fasteners like bolts, screws, nuts, and rivets to join materials.

Solid state:

Adhesive bonding: Joins materials using adhesives that cure and provide a strong bond.
Soldering: Joins metals using a lower temperature filler metal (solder) with a melting point below the base metal.
Brazing: Joins metals using a filler metal with a higher melting point than solder but lower than the base metal.

These welding and joining processes offer different advantages and are chosen based on the specific application, materials being joined, and desired results.

40) What are Different types of electrodes?

Cellulosic electrodes:

Provide deep penetration in all positions.
Suitable for vertical down welding.
Offer reasonably good mechanical properties.
Generate a high level of hydrogen, increasing the risk of cracking in the heat-affected zone (HAZ).

Rutile electrodes:

Produce moderate weld metal mechanical properties.
Create a good bead profile due to the viscous slag.
Slag is easily removable.

Basic electrodes:

Offer low hydrogen weld metal, minimizing the risk of cracking.
Require high welding current or speeds.
Produce a poor bead profile with a convex and coarse surface.
Slag removal can be difficult.

These are just a few examples of electrode types, and there are many variations and specific classifications within each type. The choice of electrode depends on the specific welding application, base metal, desired mechanical properties, and environmental conditions.

41) What are the main metal transfer modes in welding?

There are three main metal transfer modes in welding:

Short-circuiting transfer: In this mode, the welding wire comes into contact with the weld pool and creates a short circuit. The wire melts and small droplets transfer across the arc in a rapid, controlled manner.
Droplet/spray transfer: This mode is characterized by larger droplets of molten metal that are propelled across the arc in a spray-like pattern. It is commonly used in high-current applications and results in higher deposition rates.
Pulsed transfer: Pulsed transfer combines elements of both short-circuiting and droplet transfer. The power source alternates between high and low currents, allowing controlled droplet transfer while reducing spatter and heat input.

Each transfer mode has its advantages and is selected based on the welding process, material type, and desired weld characteristics.

42) What is the function of shielding gas?

The primary functions of shielding gas in welding are:

Stabilizing the arc roots on the material surfaces: Shielding gas protects the arc from atmospheric contamination, preventing oxygen and nitrogen from reacting with the molten metal. This stabilizes the arc and ensures a consistent heat source for the welding process.
Ensuring smooth transfer of molten metal: Shielding gas helps control the metal transfer from the welding electrode to the weld pool, ensuring a stable and controlled weld bead formation.
Forming the arc plasma: Shielding gas ionizes and forms the arc plasma, which is essential for generating the heat required for welding and creating a protective environment for the weld pool.

The choice of shielding gas depends on the welding process, base metal, and specific requirements of the application.

43) What are the commonly used shielding gases in GTAW (Gas Tungsten Arc Welding)?

Commonly used shielding gases in GTAW include:

Argon: Argon is the most commonly used shielding gas in GTAW. It provides good arc stability, excellent weld bead appearance, and can be used for a wide range of materials.
Argon with 2-5% hydrogen: This mixture improves the cleaning action on certain metals, such as stainless steel, and can help eliminate surface oxides.
Helium/Helium-Argon mixtures: Helium is sometimes used as a shielding gas or in combination with argon to increase heat input, penetration, and travel speed. It is particularly useful for welding non-ferrous metals.

The choice of shielding gas depends on the material being welded, the desired weld characteristics, and the specific requirements of the application.

44) What is CTOD (Crack Tip Opening Displacement)?

CTOD stands for Crack Tip Opening Displacement. It is a test method used to measure the toughness and resistance of a material to crack propagation. In the CTOD test, a notched or cracked specimen is subjected to a controlled loading, typically in a three-point bending configuration. The crack propagates under the applied load, and the displacement of the crack tip is measured.

CTOD testing provides valuable information about the fracture behavior of materials, especially those prone to brittle fracture. It is commonly used in industries such as oil and gas, nuclear, and structural engineering to assess the integrity of welded joints and determine the material’s resistance to crack growth.