Replacement / Repair Plates (A14.15)

Question 1

All proposed design, work execution, materials, welding procedures, examination, and testing methods must be approved by ?

Answer 1

the authorized inspector or by an engineer experienced in storage tank design.

Question 2

What repair is no hydrotest- either AI or Engineer

Answer 2

Minor Repair

Question 3

What repair has to be approved by Engineer

Answer 3

Major Repair

Question 4

Inspection hold point & associated specific activities

Answer 4

authorized inspector or by an engineer

Question 5

Minimum Thickness of Replacement Shell Plate

Answer 5

thickness of the replacement shell plate shall not be less than the greatest nominal thickness of any plate in the same course adjoining the replacement plate except where the adjoining plate is a thickened insert plate

Question 6

Minimum Dimensions of Replacement Shell Plate

Answer 6

12 in. or 12 times the thickness of the replacement plate, whichever is greater.

Question 7

Where one or more entire shell plates or full height segments of shell plates are to be removed and replaced, what requirements?

Answer 7

the minimum spacing requirements specified in Figure 9.1 for vertical weld joints shall be maintained.

Question 8

Prior to welding the new vertical joints, what must be done?

Answer 8

1. the existing horizontal welds shall be cut for a minimum distance of 12 in. beyond the new vertical joints. The vertical joints shall be welded prior to welding the horizontal joints.
2. cut existing shell-to-bottom weld for a
   minimum of 12 in. beyond the new vertical joints. The cut shall extend past or stop short of existing bottom plate welds by at least 3 in. or 5t. Weld the shell- to-bottom weld last.

Question 9

min weld spacing of toes of welds for replacement plates R/B/H/V/A/C Values for T< (or equal) .5”

Answer 9

6” / 6” / 3” / 6” / 12” / Greater of 3 in. or 5t

Question 10

min weld spacing of toes of welds for replacement plates R/B/H/V/A/C Values for T> .5”

Answer 10

Greater 6” or 6t / 10” or 8t / 10” or 8t/ 10” or 8t / 12” or 12t / Greater of 3 in. or 5t

Question 11

What is the toes?

Answer 11

The junction of the weld face and the base metal

Question 12

What has more stress?

Answer 12

vertical stress is higher

Question 13

What are acceptable form of lap patch repairs?

Answer 13

acceptable form of repair for (1) buttwelded,

(2) lap-welded, and (3) riveted tank shells,

Question 14

When can Lapped patch shell repairs shall not be used?

Answer 14

On any shell course thickness (original construction) that exceeds ½ in., nor to replace doorsheet or shell plates.

Question 15

What is the maximum vertical and horizontal dimension of the repair plate? and min repair plate dim?

Answer 15

V48 in. and H72 in.

The minimum repair plate dimension is 4 in.

Question 16

prior to application of a lapped patch shell repair, what must be done?

Answer 16

the areas to be welded shall be ultrasonically inspected for plate defects and remaining thickness

Question 17

When can the repair plate may cross any butt-welded vertical or horizontal shell seams that have been ground flush,

Answer 17

Only when there is an overlap a minimum of 6 in. beyond the shell seam.

Question 18

Repair plates positioned on the shell interior shall be located such that ?

Answer 18

the toe-to-toe weld clearances are a minimum of 6 in. to the shell-to-bottom weld

Question 19

When can lapped patch repair plates may be used?

Answer 19

(1) existing shell openings or
(2) the removal of severely corroded or eroded areas.
(3) used to reinforce areas of severely deteriorated shell plates

Question 20

All corners, except at the shell-to-bottom joint, shall be rounded to a minimum radius of ?

Answer 20

2”

Question 21

When can Repair plates may extend to and intersect with the external shell-to bottom joint

Answer 21

if the vertical sides intersect the tank bottom at a 90° angle and the shell-to-bottom weld

Question 22

lapped patch repair plates closure of holes? requirement

Answer 22

• E< (equal)0.7 ,
• 1/16 (equal) < t < .5,
• D- > (equal) 2”
• overlap of max 8t or min 1”

Question 23

lapped patch repair plates severely corroded? requirement

Answer 23

• E< (equal)0.35
• 1/8 >(equal) < t < 1/3t of shell
• t

Question 24

When can Lapped patch repair plates may be used to repair small shell leaks, or minimize the potential from leaks from severely isolated or widely scattered pitting

Answer 24

• Lapped patch repair plates may be used to repair small shell leaks, or minimize the potential from leaks from severely isolated or widely scattered pitting
• The repair plate is designed to withstand the hydrostatic pressure load between the repair plate and the shell assuming a hole exists in the shell using a joint efficiency of 0.35

Question 25

When can lapped patch repair not be used?

Answer 25

• presence of product between the shell plate and repair plate will prevent gas freeing from the tank to perform hot work
• not be used if exposure of the fillet welds to the product will produce crevice corrosion or if a corrosion cell between the shell plate and repair plate is likely o occur

Question 26

What are some repair methods?

Answer 26

(1) Grind with smooth contour,
(2) localized depositions,
(3) replacement plates,
(4) lap welded patch plates.

Question 27

For lap patch repair what are weld size?

Answer 27

Full fillet welds