API RP 575 NDE

Question 1

In ultrasonic thickness measurements, dual-element transducers have the ability to operate from thin sections of ____ inch

Answer 1

0.050 – 1.000

Question 2

In performing ultrasonic thickness measurements _____ transducers are recommended for measurements on penetrations and floors and _____
transducers are recommended on shells where coating thickness may not be
uniform.

Answer 2

Dual-element, Single crystal contact

Question 3

What ultrasonic method can be used to assist in the discrimination between inclusions in the metal and laminations?

Answer 3

Shear wave

Question 4

The pan-type floating roof is the simplest type of floating roof design. Which of the following is the most correct?

Answer 4

This design is susceptible to sinking

Question 5

If soil movement raises the grade level to cover the lower portion of the shell, what would you as the inspector look for?

Answer 5

Severe external corrosion of the shell just above the soil line

Question 6

Why is inspection for cracking of the lower-shell-to-sketch-plate weld critical?

Answer 6

This area is critical because in relatively large or hot tanks, it has more potential for corrosion

Question 7

Inspection of pipe connections to the tank should include bolting at flanged joints. Piping that enters the ground should be inspected at the soilto-
air interface by excavating ___ to ___ inches to permit visual and ultrasonic thickness examination.

Answer 7

6 to 12

Question 8

Grounding connections should be visually checked for corrosion at the point where they enter the earth. What is the approximate total resistance
from the tank to earth?

Answer 8

Should not exceed 25 ohms

Question 9

The inspector finds corrosion during the shell inspection and requires ultrasonic thickness measurements to be taken. How many measurements
would normally be taken?

Answer 9

At least one thickness measurement on each shell ring

Question 10

In obtaining shell thickness measurements, special attention should be given to the upper __ inches of un-coated shells of floating-roof tanks

Answer 10

24

Question 11

Welded tanks that have significant distortions may cause the weld seams to be over-stressed. In addition to the bottom-to-shell joint, what other
welds are susceptible to cracking?

Answer 11

Vertical shell seams

Question 12

When conducting a tank roof inspection on a floating roof, in addition to the recommendation that the inspector walk on weld seams, what other
precaution should be taken?

Answer 12

The roof should be in the high-gauge position if volatile liquid is in the tank

Question 13

When a tank is of welded construction and has significant distortion, weld seams may crack. When cracking is suspected, what is the preferred
method of nondestructive examination?

Answer 13

MT

Question 14

Which of the following is the correct procedure for pressure testing roof drain lines and joints?

Answer 14

First test at about 30 psi for approximately ½ hour then reduce pressure to 5 psi and hold for another ½ hour

Question 15

In conducting a preliminary internal visual inspection, what is the
recommended sequence of the inspection?

Answer 15

roof, internal supports, shell, and bottom in that order

Question 16

Caustic stress corrosion cracking (caustic embritlement) is prevalent when the temperature rises above ____°F.

Answer 16

150F

Question 17

Where would you expect to find significant internal corrosion in a tank in sour refinery fluid service?

Answer 17

In vapor space above the stored liquid

Question 18

When the statistical methods are used to assess the probable condition of a tank bottom, what is the typical amount of the floor that should be
randomly scanned?

Answer 18

5 to 10 percent