API 510 Welding Inspection 5 — Questions and Answers
Question 1: Under API 510, a 'hot tap' welding procedure on an in-service pressure vessel requires special consideration primarily because:
- Hot taps never require welder qualification
- Welding is performed on equipment containing fluid under pressure and temperature, requiring special heat input controls to prevent burn-through (Correct answer)
- Hot taps are exempt from all code requirements
- Only visual inspection is needed for hot tap welds
Correct answer: Welding is performed on equipment containing fluid under pressure and temperature, requiring special heat input controls to prevent burn-through
Hot tap welding on in-service equipment requires strict heat input controls and procedure qualification to prevent burn-through of the pressurized, potentially fluid-filled shell.
Question 2: When reviewing radiographs of a pressure vessel longitudinal seam weld, the inspector identifies elongated dark linear indications aligned with the weld axis. This most likely represents:
- Scattered porosity
- Slag inclusions or incomplete fusion (Correct answer)
- Tungsten inclusions
- Base metal laminations
Correct answer: Slag inclusions or incomplete fusion
Elongated linear indications aligned with the weld axis in radiographs are characteristic of slag inclusions or incomplete fusion, both of which are rejectable planar discontinuities.
Question 3: Per API 510 and ASME Section IX, a welder's performance qualification (WPQ) expires if the welder has not welded using the qualified process for a period exceeding:
- 3 months
- 6 months (Correct answer)
- 12 months
- 24 months
Correct answer: 6 months
Per ASME Section IX QW-322, a welder's qualification expires if they have not used the qualified process within any 6-month period.
Question 4: An inspector notices that a weld repair on a pressure vessel shell was made with heat input significantly higher than qualified in the WPS. The primary concern with excessive heat input in carbon steel is:
- Increased risk of underfill
- Grain growth in the HAZ leading to reduced toughness and potential cracking susceptibility (Correct answer)
- Faster weld completion and reduced cost
- Improved corrosion resistance of the weld metal
Correct answer: Grain growth in the HAZ leading to reduced toughness and potential cracking susceptibility
Excessive heat input causes grain growth in the heat-affected zone, which reduces toughness and increases susceptibility to brittle fracture, particularly at low temperatures.
Question 5: Per API 510, who is responsible for verifying that welders performing repair work on a pressure vessel are currently qualified for the applicable WPS?
- The welding foreman only
- The repair organization and the Authorized Pressure Vessel Inspector (Correct answer)
- The plant owner only
- The jurisdiction authority only
Correct answer: The repair organization and the Authorized Pressure Vessel Inspector
Both the repair organization (who must maintain welder records) and the Authorized Pressure Vessel Inspector share responsibility for verifying current welder qualifications.
Question 6: When examining a weld repair on a pressure vessel for hydrogen-induced cracking (HIC), the inspector should schedule NDE examinations:
- Immediately upon weld completion while the metal is still warm
- At least 24-48 hours after welding is complete and the weld has cooled to ambient temperature (Correct answer)
- Only if the weld appears visually suspicious
- Before post weld heat treatment is performed
Correct answer: At least 24-48 hours after welding is complete and the weld has cooled to ambient temperature
Hydrogen-induced cracking is a delayed phenomenon that can occur hours or days after welding; NDE should be performed at least 24-48 hours after weld cooling to allow any HIC to develop and become detectable.
Question 7: A pressure vessel repair weld on a P-No. 4 (Cr-Mo alloy steel) material requires PWHT. If the PWHT cannot be performed due to equipment constraints, which API 510 alternative technique might be considered for a localized repair?
- Skip PWHT entirely and rely on visual inspection
- Apply temper bead welding technique per approved engineering procedures (Correct answer)
- Use a lower-strength filler metal to avoid the PWHT requirement
- Perform a hydrostatic test instead of PWHT
Correct answer: Apply temper bead welding technique per approved engineering procedures
Temper bead welding is a recognized alternative to conventional furnace PWHT for localized repairs on alloy steels when properly engineered and approved per API 510 and ASME Code Case provisions.
API 510 Welding Inspection 5
Under API 510, a 'hot tap' welding procedure on an in-service pressure vessel requires special consideration primarily because: