In this topic (most difficult part in EXAM), we will try one by one of the Open/Close questions on Module ASME 31.3 – Design pipe thickness as a part of in-the-exam API 570 Body of knowledge (BOK)

If you don’t know how API 570 Certification scheme, See API 570 Certification Instructions

INTERNAL PRESSURE / MINIMUM THICKNESS OF PIPE
The inspector should be able to determine:
a) The minimum required thickness or pressure design thickness of a straight pipe section for internal pressure only (ASME B31.3 Section 304.1.1 and 304.1.2);
b) The minimum required thickness of a permanent blank for a given design pressure (ASME B31.3 Section 304.5.3);
c) The “MAWP” of corroded pipe, compensating for expected corrosion loss at the next inspection (API 570, Par., 7.5)
The inspector should also be able to compensate for the corrosion allowance. (Add “+” or subtract “-“ based on requirements from the exam problem).

Before going to applied the design formulas from ASME B31.3, you must understand the basic standardized and concept allowance in API 570 (e.g API 574)

Question 1: Piping size (NPS) made by rolling plates and welding the seams is normally larger than __ inches outside diameter.
a. 10
b. 16
c. 14
d. 12

Answer: B – See API 574, 4.1

Question 2: Steel and alloy piping are manufactured to standard dimensions in nominal pipe sizes (NPS) up to __ inches.
a. 24
b. 36
c. 48
d. 50

Answer: C – See API 574, 4.1

Question 3: Steel and alloy piping are also manufactured to standard thicknesses designated as SCHEDULES in nominal pipe sizes (NPS) up to _ inches.
a. 24
b. 36
c. 48
d. 50

Answer: B – See API 574, 4.1

Question 4: For all nominal pipe sizes (NPS) of __ inches and above, the size refers to the nominal Outside diameter (OD).
a. 10
b. 12
c. 14
d. 16

Answer: C – See API 574, 4.1

Question 5: From ASME B31.3, Para.304.1.2, in the equation, tm = t + c, pick the correct definition of the value “t”.
a. minimum required thickness, including mechanical, corrosion, & erosion allowances.
b. pressure design thickness, as calculated for internal pressure.
c. pipe wall thickness (measured or minimum per purchase specification.
d. minimum design temperature of the pipe.

Answer: B

Question 6: A run of straight piping is 12 NPS (12.75” O.D.), and is designed for 350 psig @ 300°F using A-106 B seamless pipe. With a 1/8” corrosion allowance, what is the minimum thickness of the pipe?

a. 0.236
b. 0.111
c. 0.125
d. 0.225

Answer: A (Minimum thickness in ASME B31.3 is included with Corrosion Allowance)

The weld quality factor E has been explained in API 570 Quiz (ASME 31.3 – Quality Factor of Weld-joint and Casting)

Question 7: What is the maximum design pressure on in-service piping that is 14” O.D., ASTM A335 Grade P5 seamless 3/8” (0.375) thick (with 1/8” (0.125) corrosion allowance) and operating at 600°F?

a. 650 psig
b. 600 psig
c. 625 psig
d. 675 psig

Answer: B