This article is about WELDING & PIPING INTERVIEW QUESTIONS PART-1 as per international codes and standards and useful for Welding and piping engineers, QCs, Supervisors and managers.
Welding & Piping Interview Questions
1: What is the primary reason for post-weld heat treatment (PWHT)?
A: The primary reason for PWHT is to relieve residual stresses introduced during welding, improve the mechanical properties of the welded material, prevent hydrogen embrittlement, and bring about beneficial microstructural changes.
2. What are the various sources of hydrogen in welding?
A: Hydrogen in welding may come from sources such as lubricants, moisture, and contaminated electrodes.
3. Materials with high thermal conductivity will require?
Materials with high thermal conductivity will require higher heat input to weld. This is because their ability to conduct heat efficiently results in faster heat dissipation from the welding zone. To compensate for this rapid heat loss, a higher heat input is needed during welding to ensure proper fusion and penetration of the material.
4. The general Brinell hardness limit for 5CR-Mo steels is:
The general Brinell hardness limit for 5CR-Mo steels is BH 241. Brinell hardness (BH) is a measure of a material’s hardness based on the indentation made by a hardened steel ball under a specified load. In the case of 5CR-Mo steels, the general hardness limit is set at BH 241, indicating the desired hardness level for this type of steel.
5. A material Test Report shows the following chemistries:
A material Test Report shows the following chemistries:
- Carbon: 0.15%
- Chrome: 1.25%
- Vanadium: 0.02%
- Manganese: 0.20%
- Molybdenum: 1.00%
- Silicon: 0.53%
- Nickel: 0.35%
- Copper: 0.01%
These values represent the chemical composition of the material being tested. The percentages indicate the respective amounts of each element present in the material. This information is essential for determining the material’s properties, suitability for specific applications, and compliance with relevant specifications or standards.
6. What is the approximate CE of this material using the formula supplied in RP 577?
The approximate CE (Carbon Equivalent) of the material can be calculated using the formula provided in RP 577. However, without the specific formula from RP 577, I cannot provide the exact calculation process.
In this case, the calculated CE value is given as 0.68. The CE value is a measure of the weldability and susceptibility to cracking of a material. It is often used to assess the heat-affected zone (HAZ) of a welded joint. A higher CE value indicates a higher carbon equivalent content and may suggest a higher risk of cracking during welding.
7. What is the approximate CE of this material using the formula supplied in RP 577?
The approximate Critical Exposure (CE) of the material, as calculated using the formula provided in RP 577, is 0.68. The CE value indicates the concentration of a substance in the surrounding environment that could potentially cause damage or failure to the material. However, without additional context or details about the specific formula and parameters in RP 577, it is challenging to provide further explanation or interpretation of the calculated value.
8. From the above CE number, what should typically be done after welding this steel?
By implementing preheating and PWHT, the welded steel can experience improved weld quality, reduced risk of defects, and enhanced resistance to brittle fracture. However, it’s worth noting that the specific preheating and PWHT requirements may vary based on factors such as the type of steel, welding procedure, and relevant industry standards or guidelines.
9. Austenitic stainless steels typically contain chrome and nickel, and are used for:
Austenitic stainless steels, which commonly contain chrome and nickel, are primarily utilized for two key reasons:
- Corrosion Resistance: Austenitic stainless steels are highly valued for their exceptional corrosion resistance properties. The presence of chromium in these steels forms a protective passive oxide layer on the surface, which helps prevent corrosion and oxidation. This makes them suitable for applications where the material is exposed to corrosive environments, such as in marine environments, chemical processing plants, and food processing industries.
- Resistance to High Temperature Degradation: Austenitic stainless steels also exhibit good resistance to high-temperature degradation. The combination of nickel and chromium enhances their ability to withstand elevated temperatures without significant structural changes or loss of mechanical properties. This makes them suitable for applications in high-temperature environments, such as heat exchangers, furnace components, and exhaust systems.
10. The most common measure of weldability and hot cracking of stainless steel is-
The most common measure of weldability and hot cracking susceptibility in stainless steel is the “ferrite number.” The ferrite number is a quantitative measurement that indicates the amount of ferrite present in the microstructure of stainless steel welds.
11. What is the most common types of fracture toughness tests is?
One of the most common types of fracture toughness tests is the “Charpy test.” The Charpy test measures the impact strength or energy absorption capacity of a material, particularly metals, when subjected to a sudden impact load.
In the Charpy test, a standardized specimen is placed on supports, and a pendulum hammer strikes the specimen at a specified notch. The impact energy required to fracture the specimen is measured. The result is expressed as the energy absorbed during the fracture, which indicates the material’s ability to resist brittle fracture and absorb energy under impact loading conditions.
12. What is required for Materials with high thermal conductivity?
Materials with high thermal conductivity will generally require a higher heat input to weld effectively. Thermal conductivity refers to the ability of a material to conduct heat, and materials with high thermal conductivity can quickly dissipate heat away from the weld zone.
When welding materials with high thermal conductivity, such as copper or aluminum, the heat applied during the welding process can rapidly dissipate, leading to challenges in achieving proper heat distribution and fusion. Therefore, a higher heat input is required to compensate for the rapid heat dissipation and ensure sufficient heat penetration and fusion at the weld joint.
13. What types of metallic materials are predominantly utilized in refineries or chemical plants?
The vast majority of metallic materials used in refineries or chemical plants are typically “wrought materials.” Wrought materials refer to metals that have been processed by various mechanical operations, such as rolling, forging, or extrusion, to shape them into their final form.
Wrought materials offer several advantages that make them well-suited for use in refineries and chemical plants. They typically have superior mechanical properties, including strength, toughness, and ductility, which are important for withstanding the demanding operating conditions and loads experienced in these environments.
14. What welding qualifications does a welder obtain when qualifying with a groove weld in plate in the 4G position?
Answer: When a welder qualifies with a groove weld in plate in the 4G position, they are typically qualified to perform what types of welds in plate and pipe, specifically for pipe sizes over 24″ O.D., according to QW-461.9?
15. What specific welding qualifications does a welder achieve by successfully making a groove weld on a 3/4″ O.D. pipe in the 5G position, as per QW-461.9 and QW-452.3?
Answer: When a welder qualifies by making a groove weld on a 3/4″ O.D. pipe in the 5G position, they are typically qualified to perform groove welds on what size of pipe and in what position, according to the guidelines specified in QW-461.9 and QW-452.3?
16. According to the requirements specified in QW-462.1 (b), what is the minimum outside diameter of pipe that allows the use of reduced-section tensile test specimens for all thicknesses of pipe?
3 inches
17. In addition to being qualified for Shielded Metal Arc Welding (SMAW) using an E7018 electrode, which other welding electrodes is a welder qualified to use based on their qualification?
Answer: When a welder is qualified for SMAW using an E7018 electrode, they are typically qualified to weld with which specific welding electrodes, including E7015, E6011, E6010, and E7024?
18. Under what conditions is a welder qualified to weld all thicknesses of material according to the specified requirements?
Answer: When the test coupon thickness is ½ inch and over, with a minimum of three layers, a welder is typically qualified to weld all thicknesses of material.
19. In order for a welder to be qualified for all position groove welding on pipe, if they are already qualified to weld in the 2G position, which additional position must they also be qualified in?
5G
20. When performing qualification of pipe welds according to ASME Section IX, which positions necessitate the use of more than two guided bend specimens for qualification?
5G and 6G
21. When seeking Performance Qualification in a 6G position, how many transverse guided bend tests are typically required?
4
22. In order to qualify a welder for all position pipe welding, which specific positions are typically required?
2G and 5G.
23. What is the minimum plate thickness that is permissible for use in the shell or head of a pressure vessel?
1/16”
24. Among carbon steel, 18Cr-8Ni, Monel, and aluminum, which material would exhibit the greatest expansion when heated from 70 degrees F. to 550 degrees F.?
According to the information provided by the ASME B31.3 standard, specifically Table 319.3.1(a) and the Appendix, aluminum will expand more than the other materials (carbon steel, 18Chr-8Ni, Monel) when heated from 70 degrees Fahrenheit to 550 degrees Fahrenheit.
Aluminum has a higher coefficient of thermal expansion compared to the other materials mentioned. The coefficient of thermal expansion is a measure of how much a material expands or contracts with a change in temperature. Generally, metals tend to expand when heated.
25. A carbon steel ASTM A 53 Grade B material is being impact tested. What is the minimum energy requirement for this material (average for 3 specimens-fully deoxidized steel)?
According to the ASME B31.3 standard, specifically section 323.3.5 and Table 323.3.5, the minimum energy requirement for impact testing of carbon steel ASTM A 53 Grade B material (fully deoxidized steel) is 10 ft-lbs (foot-pounds) on average for three specimens.
The standard specifies the minimum energy that the material should absorb during the impact test to ensure its suitability for certain applications. In this case, ASTM A 53 Grade B carbon steel, which is commonly used for pipes and fittings, is required to have an average impact energy of at least 10 ft-lbs.
26. How many inches extend of zone for preheat?
According to the ASME B31.3 standard, specifically sections 330.1.4 and 323.2.2B, the zone for preheat shall extend at least 1 inch beyond each edge of the weld.
Preheating is a technique used in welding to raise the temperature of the base metal in the vicinity of the weld joint before welding. It is done to reduce the cooling rate during welding and prevent the formation of undesirable microstructures and potential defects, such as cracking.
According to ASME B31.3 standard, specifically section 331.1.3, when components of a piping system are joined by welding, the thickness to be used in applying the heat treatment provisions, as specified in Table 331.1.1, shall be that of the thicker component measured at the joint, except for certain exclusions.
Important Note:
This means that when determining the required heat treatment for the welded joint, you should consider the thickness of the thicker component at the joint. The heat treatment provisions, such as preheating, post-weld heat treatment (PWHT), or stress relief, specified in Table 331.1.1, will be based on the thickness of the thicker component.
According to ASME B31.3 standard, specifically Table 341.3.2A, if an inspector finds incomplete penetration in a radiograph of a girth weld of normal fluid service piping, he may accept it if the incomplete penetration is 1/32″ or less deep and is within or equal to 0.2 times the wall thickness of the pipe (0.2Tw).
Incomplete penetration refers to a condition where the weld does not fully penetrate through the joint thickness, resulting in a partial fusion between the weld metal and the base metal. In certain cases, such as when the incomplete penetration is shallow and within specific limits, it may be considered acceptable based on the criteria provided in the standard.
The standard allows for acceptance of incomplete penetration up to a specific depth (1/32″ or less) and within a certain limit relative to the pipe wall thickness (0.2Tw). However, it’s important to note that these acceptance criteria may vary depending on the specific requirements and standards applicable to the project. Therefore, always refer to the latest version of the ASME B31.3 standard or any applicable codes and specifications for the precise acceptance criteria and guidelines regarding incomplete penetration in radiographs of girth welds.
According to ASME B31.3 standard, specifically section 345.4.2(a), where the design temperature of the system is the same as the hydrostatic test temperature, the hydrostatic test pressure shall be not less than 1.5 times the design pressure.
The hydrostatic test is performed to verify the integrity and strength of a piping system by subjecting it to a pressure higher than the operating pressure. In cases where the design temperature of the system is the same as the hydrostatic test temperature, the standard specifies that the hydrostatic test pressure should be at least 1.5 times the design pressure.