API 653 Welding & Metallurgy 4

Question 1

What is 'sensitization' in austenitic stainless steel, and at what approximate temperature range does it typically occur?

Accepted Answer

Chromium carbide precipitation at grain boundaries occurring between 800°F and 1500°F (427–816°C)

Answer

Sensitization occurs when chromium carbides precipitate at grain boundaries in the 800–1500°F range, depleting adjacent areas of chromium and making them susceptible to intergranular corrosion.

Question 2

Per API 653 and ASME Section IX, which of the following is an 'essential variable' that requires weld procedure requalification when changed?

Accepted Answer

Changing the base metal P-Number group

Answer

P-Number is an essential variable in ASME Section IX; changing the base metal P-Number requires a new procedure qualification test because it affects the metallurgical properties of the weld.

Question 3

What characteristic of A36 steel versus A516 Grade 70 steel makes A516-70 preferable for storage tank construction subjected to low-temperature service?

Accepted Answer

A516-70 is specifically manufactured for pressure vessel service with controlled chemistry for improved notch toughness

Answer

A516 is a pressure vessel quality plate with controlled chemistry and specified toughness properties, making it superior to structural A36 for tanks requiring reliable performance at low temperatures.

Question 4

When evaluating a weld repair on a tank shell using magnetic particle testing (MT), what is the primary limitation of the wet fluorescent MT method?

Accepted Answer

It cannot be used on austenitic stainless steel or aluminum alloys

Answer

MT relies on magnetic flux leakage and is only applicable to ferromagnetic materials; austenitic stainless steels and non-ferrous alloys cannot be inspected using this method.

Question 5

In API 653, what is the requirement for welder qualification when a welder has not welded using a qualified process for more than 6 months?

Accepted Answer

The welder must requalify by completing a new performance qualification test

Answer

Per ASME Section IX (referenced by API 653), a welder who has not welded with a qualified process for more than 6 months must requalify before performing production welds.

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

(API 653) API 653 Aboveground Storage Tank Inspector Certification Practice Test

API 653 Welding & Metallurgy 4