API 570 Quiz (ASME 31.3 – MDMT and Impact Test)

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The inspector should be able to:
a) Determine the minimum metal temperature of a material (MDMT), which is exempt from impact testing (ASME B31.3, Section 323.2.2, Figure 323.2.2A & Table A-1).
b) Determine the minimum required Charpy V-notch impact values of a given material. (ASME B31.3, Section 323.3, Table 323.3.5)

Question 1: What is the minimum design temperature for a pipe made in A516 Gr55 containing liquid petroleum gas at 150 psig that is 30 mm thick?
(a) 0°C
(b) -10°C
(c) -15°C
(d) -20°C

Answer: C, B31.3: minimum design temperatures, B31.3 graph 323.3.2A. Curve C at 30 mm thick shows –15°C

Question 2: If the material has a design stress of 160 psig and the internal pressure that produces a stress of 64 psig, what reduction can be made in the minimum design temperature without impact testing the material?
(a) 20°C
(b) 40°C
(c) 60°C
(d) 80°C

Answer: C, B31.3 graph 323.3.2B. Stress ratio = 64/160 = 0.4 gives a temperature reduction of 60°C

Question 3: What is the minimum value of Charpy impact required for steel made of fully deoxidized API 5L Gr. B pipe?
(a) 18 joules
(b) 14 joules
(c) 10 joules
(d) 7 joules

Answer: B, B31.3 section 323.3.5. Checking strength from B31.3 table A-1 gives 60 ksi. Looking in table 323.3.5 for 65 ksi and less gives a minimum Charpy value of 14 J.

Question 4: An A 381 Y-35 pipe is 1.0” thick and is installed in a system operating at 150 psi. A replacement pipe will be ordered, and will be the same material (not normalized or quenched/tempered). If the design minimum temperature is 400°F and the nominal pressure stress is 10,000 psi (10 ksi), what temperature can this material be operated at without impact testing?
a. +7° F
b. -7° F
c. 68° F
d. 61° F

Answer: A, From Fig.323.2.2A, Not-normalized A 381 will be still used by curve A as indicated in Table A-1.

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