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Wilkinson Coutts & Matthews Integrity Training

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Wilkinson Coutts ASME L1/L2 Sample Questions: Answers

Here’s four ASME L1-style Questions

L1 Q1. Damage Mechanisms: Plant inspectors need to know about these

Which of these damage mechanisms (DMs) is not classed as corrosion?

a) Stress corrosion cracking (SCC)
b) Creep
c) MIC
d) Weld attack

Ans b. Creep is not a corrosion mechanism. If you didn’t know what SCC or MIC are look them up in API 571

L1 Q2. Corrosion rate calculations. Yes, unfortunately some codes still use feet and inches as measurement units.

A pipe has the following wall thickness data recorded in its inspection reports. What is the short-term corrosion rate when calculating remaining life?

  • Thickness when new in year 2000 = 1.1in
  • Thickness measured in year 2005 at process change = 0.7in
  • Thickness measured in 2008 = 0.6in
  • Thickness measured in 2010= 0.5in

a) 0.22 in/yr
b) 0.04 in/yr
c) 0.05 in/yr
d) 0.10 in/yr

Ans c. The short-term corrosion rate (CR) rate is the most recent one i.e. from 2008 to 2010.      CR = (0.6in – 0.5in) /2 yrs = 0.05 in/yr

L1 Q3. Written Schemes of Examination (WSE). As a plant inspector you will work to a WSE so you need to be able to decide if their content is correct.

A WSE is being prepared for a recently acquired old, large, BS1500 vessel (MAWP 10 Bar) constructed out of an unknown grade of plain carbon steel, which of the following NDE methods would you not expect to be of much benefit if shown on the WSE for the first inspection?

a) Hardness tests
b) Hydraulic test to 1.3 x MAWP
c) RT of shell-to-shell circ welds
d) PMI test

Ans c. Hardness tests can detect excessive softness or hardness (risk of brittleness) A PMI test will indicate any rogue repair materials that may be present. A hydrotest is useful on a vessel with unknown history. RT on shell-shell circ welds are the least useful. They are low-stress welds and probably the least likely to develop defects except perhaps in H2 service.

L1 Q4. Storage tank inspection.

What is the correct order for checking the integrity of large circular atmospheric storage tank components during a preliminary visual inspection carried out prior to an internal inspection?

a) Bottom, shell, roof
b) Roof, shell, bottom
c) Shell, roof, bottom
d)  It doesn't really matter

Ans b. Inspections normally start at the top of the tank for safety reasons. You don’t want bits of corroded roof falling on your head whilst you are inspecting the shell or bottom.

Here’s four ASME L2-style Questions

L2 Q1. WSE high stress area; Inspectors are not designers but you need to know where to look for defects

A pressure vessel with torispherical ends is subject to an internal corrosive process and mechanical vibration condition. It is fitted with several nozzles set-throughout the shell. Which of the following would require particular emphasis in the WSE?

a) Possible corrosion of the nozzle-to-shell welds
b) Possible buckling of the vessel shell, plus peaking if it operates at high temperature
c) Possible cracking of shell-to-shell SAW welds
d) Possible cracking of shell-to-head welds

Ans d. Vibration fatigue is most likely to cause cracking of nozzle welds but that is not an answer option. The next most likely location would be the head-shell welds.

L2 Q2. Weld overlay lining.If the WSE is not good enough, and you follow it blindly, you won’t find defects that are there.

A vessel has had previous repairs made to its internal weld overlay lining. What site inspection activity should be shown on the WSE to check whether the overlay repair has been previously correctly heat treated?

a) PMI test (XRF or similar method)
b) Replication (metallurgical tests)
c) A sample removed for laboratory testing
d) Surface indentation test

Ans d. A hardness (surface indentation) test is the best indicator or heat treatment. Metallurgical replication is not just a site activity…. (did you read the question properly?)

L2 Q3. Objective of Non-intrusive inspection (NII). May we suggest you think very carefully before just ticking box (d).

On balance, the main objective of replacing internal visual inspection with NII (on-stream inspection under API terminology) is:

a) To save time and effort
b) To save inspection cost
c) To do a better inspection
d) All of the above

Ans b. This is a major principle of NII document DNV RP-103 Non-intrusive inspection. Option (d) sounds convincing but is just there to catch out the guessers. Guessers rarely pass ASME L2.

L2 Q4. Heat exchanger corrosion. These are covered by the TEMA code.

What is the disadvantage of designing a heat exchanger in corrosive service that has a plain carbon steel shell and channel and a stainless-steel tube-sheet?

a) The tube sheet suffers from impingement opposite the fluid inlet
b) The tube sheet and channel will have different inspection intervals
c) The tube sheet suffers from galvanic corrosion
d)  The shell channel suffers from galvanic corrosion

Ans d. Carbon steel is anodic to stainless steel so will suffer the galvanic corrosion. It would be impractical for the components to have different inspection intervals so (b) is not the answer

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