Replacement / Repair Plates (A14.15) Flashcards
All proposed design, work execution, materials, welding procedures, examination, and testing methods must be approved by ?
the authorized inspector or by an engineer experienced in storage tank design.
What repair is no hydrotest- either AI or Engineer
Minor Repair
What repair has to be approved by Engineer
Major Repair
Inspection hold point & associated specific activities
authorized inspector or by an engineer
Minimum Thickness of Replacement Shell Plate
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
Minimum Dimensions of Replacement Shell Plate
12 in. or 12 times the thickness of the replacement plate, whichever is greater.
Where one or more entire shell plates or full height segments of shell plates are to be removed and replaced, what requirements?
the minimum spacing requirements specified in Figure 9.1 for vertical weld joints shall be maintained.
Prior to welding the new vertical joints, what must be done?
- 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.
- 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.
min weld spacing of toes of welds for replacement plates R/B/H/V/A/C Values for T< (or equal) .5”
6” / 6” / 3” / 6” / 12” / Greater of 3 in. or 5t
min weld spacing of toes of welds for replacement plates R/B/H/V/A/C Values for T> .5”
Greater 6” or 6t / 10” or 8t / 10” or 8t/ 10” or 8t / 12” or 12t / Greater of 3 in. or 5t
What is the toes?
The junction of the weld face and the base metal
What has more stress?
vertical stress is higher
What are acceptable form of lap patch repairs?
acceptable form of repair for (1) buttwelded,
(2) lap-welded, and (3) riveted tank shells,
When can Lapped patch shell repairs shall not be used?
On any shell course thickness (original construction) that exceeds ½ in., nor to replace doorsheet or shell plates.
What is the maximum vertical and horizontal dimension of the repair plate? and min repair plate dim?
V48 in. and H72 in.
The minimum repair plate dimension is 4 in.
prior to application of a lapped patch shell repair, what must be done?
the areas to be welded shall be ultrasonically inspected for plate defects and remaining thickness
When can the repair plate may cross any butt-welded vertical or horizontal shell seams that have been ground flush,
Only when there is an overlap a minimum of 6 in. beyond the shell seam.
Repair plates positioned on the shell interior shall be located such that ?
the toe-to-toe weld clearances are a minimum of 6 in. to the shell-to-bottom weld
When can lapped patch repair plates may be used?
(1) existing shell openings or
(2) the removal of severely corroded or eroded areas.
(3) used to reinforce areas of severely deteriorated shell plates
All corners, except at the shell-to-bottom joint, shall be rounded to a minimum radius of ?
2”
When can Repair plates may extend to and intersect with the external shell-to bottom joint
if the vertical sides intersect the tank bottom at a 90° angle and the shell-to-bottom weld
lapped patch repair plates closure of holes? requirement
- E< (equal)0.7 ,
- 1/16 (equal) < t < .5,
- D- > (equal) 2”
- overlap of max 8t or min 1”
lapped patch repair plates severely corroded? requirement
- E< (equal)0.35
- 1/8 >(equal) < t < 1/3t of shell
- t
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
- 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
When can lapped patch repair not be used?
- 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
What are some repair methods?
(1) Grind with smooth contour,
(2) localized depositions,
(3) replacement plates,
(4) lap welded patch plates.
For lap patch repair what are weld size?
Full fillet welds
