Lockhart day 1 training Flashcards
What are the 5 major components of a tank?
- Foundation
- Shell
- Bottom
- Roof
- Nozzles/Penetrations
What are the 2 major welds?
- Shell to bottom welds
2. Shell to roof welds
Foundation is requirement to prevent settlement that could lead to failure (2)
- settlement can cause high stresses to the shell to bottom joint
- Settlement could cause the tank shell to disfigure and prevent the floating roof from functionion
2 basic types of foundation?
- foundation with concrete ring wall
2. foundation without ring wall
Some important notes on foundation with concrete ring wall? (5)
1. clean wash sand (min 3") 2, slope 1inch in every 10 feet toward center 3. Concrete/ringwall width of 12" min 4. 1" / 2" taper of concrete (OD/ID) 5. 1feet above ground level
Plate extension min?
2”
Annual plate min radius width?
24”
3 plate lap in tank shall be min distance away?
min 12” from each other.
Bottom plates can be? (6)
- can be single weld lap joints
- reasonably rectangle
- attached with full fillet welds
- corroded thickness not less than 0.236”
- nominal width of 72”
- slope of 1:120
Sketch plates can be? (6)
- can be single weld lap joints
- butt welded sketch plates shall be ground flush where shell plate rest on it
- Attached with full fillet welds
- if square grooves are used the root opening shall be no less than 1/4”
- shall have a corroded thickness not less than 0.236”
- Extend no less than 2” outside the shell.
annular plates can be ? (6)
- weld shall be ground flush where shell plate rest on it
- weld connecting it to the bottom shall be no closer than 12” to a 3 lap joint
- shall be butt welded and have a radial width of 24”
- Weld shall have full joint penetration
- If squire groove is used it shall have a 1/4” root opening
- min toe - toe distance of 12” between a 3 lap joint and other bottom plate to annual plate welds
When is annular plate used? and exceptions
- Group IV,IVA, V, VI materials
Exceptions (lap welded bottom plates can be used)
- first course shell is «_space;23,200 psi
- max hydrotest for first shell course «24,900 psi
annular plate design table when to use API650 or 653 table?
API653 is used for SG < 1.0
What is API 2201?
Safe hot tapping practices
ASNT SNT-TC-1A
NDE personnel qualification/certs
break over point?
area on bottom where settlement beings
Welding (2)
- welding sequenced such to minimize distortion
2. Bottom to shell joint welded prior to finish welds in bottom plates
What inspection for bottom plates? (4)
- vacuum test
- Tracer Gas
- Hydro (min 6’ of water height)
- VI
Vacuum box test ? (6)
1. size of box is 30" x 6" 2 partial vacuum of 3-5 psi, if 2nd test 8-10 Psi 3. 2" min of overlap 4. temp 40F to 125F 5. min of 100 foot candles (1000 lux) 6. held for at least 5 seconds
Vacuum box operator (2)
- have an annual vision exam (jaeger 2)
2. be competent
bottom to shell weld joint are what?(2)
- highest stressed part of the tank
- failure of this weld can be by cracking due to high stresses from settlement/corrosion / poor design/maintenance/frabrication
bottom to shell weld with (t < 1/2”(4)
- shall be fillet welds
- max size is 1/2” (each leg)
- min size cannot be less than the thinner of the 2 plates (each leg)
- Figure api650 5.1.5.7
annular part bottom to shell weld with (t >1/2”)
- fillet/groove weld plus fillet weld shall be = annular plate thickness but NOT exceed shell plate thickness.
NDE Inspection for bottom to shell weld? (5)
- MT (can be done on both side)
- Solvent type (water soluble type) die penetrant to tank ID and developer to OD
(1hr dwell) - diesel to OD and inspection ID (4 hr)
- Right angle vacuum from ID
5, gap between 2 welds can be pressurized with 15PSIG
candidate tank?
corrosion rate not known
what is API620?
design of large, welded, low pressure storage tanks
Shell penetration consider as major repair/alteration?
> 12”
Installing a bottom penetration within what distance of the shell is major repair/alteration?
<12”
Remove or replacing or adding a shell plate beneath the design liquid level where the longest dimension exceeds?
> 12”
Remove/replacing/adding a section of annual plate ring is consider a major repair/alteration
> 12”
Removal and replacement of annual ring weld / vertical shell weld is consider a major repair/alteration?
> 12”
remove and replacing part of weld attaching the shell to bottom in excess of what amount is major repair/ alteration
50% of the weld
tank roof shall be repair/replaced when the thickness in 100 in2 is less than?
0.09”
what must be repaired on a floating roof if discovered during inspections? (3)
- cracked
- punctured area
- area that may hole before next inspection
APi 650 annex C?
external floating roofs
API 650 annex H?
internal floating roofs
misalignment allowed for vertical welds?
>5/8”
«5/8”
- > 5/8” = not exceed 10% of plate thickness or 1/8” (lessor)
- «_space;5/8 = 10% not exceed 1/16”
misalignment allowed for horizontal welds?
>5/16”
<5/16
- > 5/16 = Upper plate shall not project beyond the face of the lower by more than 20% of upper plate thickness, max 1/8”
- < 5/16 = 20%,, max 1/16”
max undercut for vertical/attachment/flush type opening and shell to bottom welds?
1/64”
max undercut for horizontal , horizontal attachment, and annular plate butt joints
1/32”
peaking at what type of joints?
vertical
banding at what type of joints
horizontal
peaking/band should not exceed what for new tanks?
1/2”
peaking/banding for reconstructing tanks should not exceed?
peaking = 1/2" banding = 1"
When is RT required? (3)
shell butt welds, annular butt welds, flush type connection (butt weld)
What appendix for frangible roofs?
API 650 Annex F
650 Appendix M is applicable to?
200F to 500F
What is yield strength for shell material unknown at elevated temp?
30 KSI
What type of roof is more prone to sinking?
pan type
What type of roof is most common?
cone roof
Cone roof requirements. (4)
- 3/16” nominal thickness
- CA must be added for supported / unsupported roofs
- slop is 1:16” or greater
- frangible roof is restrict slope max is 2:12
type of fixed roof? (3)
- cone roof - up to 60 feet self support.
- umbrella - usually self support
- geodesic - self support
what is a frangible roof design?
designed for the roof to fail before the shell to bottom joint during an overpressure
Calculation the pressure needed to lift a roof?
Drl = 2.55 X (# of 16ths) ./ 144
width x thickness
When will a fixed roof sit on rafters (not welded) fail-at what pressure?
when the internal pressure exceed the weight of the roof.
what is in contact with shell (part of a roof)?
metallic shoes/mechanic
what is min roof plate thickness?
=3/16” + CA
Methods to test roof? non gas tight (1) gas tight (2)
- VT on non gas tight type roof
GAS TIGHT - Internal pressure and bubble test welds (not exceeding the weight of the roof plates)
- vacuum test joints
What type of welds are not permitted on roof?
Butt type welds
What type of welds are permitted on roof?
Full fillet welds
Required min thickness for bottom plates NEW?
- not less than 0.236”
min width of bottom plates?
> > 72”
min diagnostic length of RT?
6”
how to inspect welding repairs on bottom tank?
VI –> Vacuum/tracer test –> MT/LP
what to do if crack found in the shell to bottom weld?
cracks to be remove
reason for distortion of anchor bolts and concrete?(2)
- over pressure
2. settlement
welding identification shall be marked adjacent to the weld at what inervals?
not exceeding 3feet , physical record in lieu of stamping is allowed
how to qualify steel from existing tank if material is unknown?
use test coupon from existing plate
UT qualifications?
Level II/III, with supervision for level 1
tank reconstruction new vertical joints in adjacent shell can be offset by what distance?
5t (thicker plates)
vertical joints in new tank should be offset by ?
5t of thicker plate
single/double welded lap joint min allowed lapped?
5t of thinner plate or 1 (single) /2” (double)(lessor)