lockhart day 3 training Flashcards
single lap welded joint are allowed?
- bottom plates
2. roof plates
min size of fillets? T > 3/16 and t < 3/16
- t >3/16 = shall be less than 1/3 of thickness of thinner plate and ATLEAST 3/16”
- t «_space;3/16 = full fillet
when is a lap patch not allowed? what thickness?
when t > 1/2”
what is min lap patch thickness?
3/16” but not greater than 1/2”
Max size for lap patch?
48” x 72”
min size for lap patch
4”
joint efficiency for a lap patch ? (2)
0.7 / 0.35
lap patch overlap min/ max?
min = 1" max = 8t
hot tapping requirements? (3)
- 3feet below liquid level
- <7000 psi
- reinforcement thickness = shell thickness
hot tapping with unknown metal limitation?
- limited to 4”
what is hot tapping procedure?
API 2201
when do you need a reinforcement pad ?
when NPS > 2”
when is hot tap not allowed?
not allowed when PWHT is required
how to calculate hydro pressure?
1.5 X 0.433 X liquid height
min radius for a lap patch ?
2”
overlap distance requirement for lap patch CROSSES an existing butt weld?
6”
how close can the horizontal weld of a repair plate be to the shell to bottom weld?
6”
min required overlap of a bottom lap patch to cover a corroded area?
2”
min dimension for a welded on patch for the tank bottom that overlaps a 3 lap seam?
12”
max dimension of a bottom lap patch that is within the critical zone
24”
min required distance a bottom lap patch must be from an existing bottom plate weld
2”
max taper for a shell patch
1:4
require shape of a floor patch that is within 6” of a shell
tombstone
max thickness of a lap patch in critical zone
1/4”
min allow roof rim thickness before replacing? new roof thickness?
0.1” / 3/16” + CA
when should settlement survey be conducted?
prior to hydro, EXCEPT for tanks with acceptable settlement history.
max measurement points OD / ID for bottom settlement
32 feet / 10 feet
NDE method for hot tap nozzles?
MT or PT (for all attachment welds)
when dismantling a tank, how close to an existing weld can the tank bottom plates be cut if they are going to be reused?
2”
when dismantling a tank, how much of the existing weld should be cut out?
lessor of( 1/2” of weld metal width OR 1/4 each side)
shell rings maybe be dismantle by cutting a min of what distance form existing welds?
6”
when dismantling a tank how should roof plates be cut out?
deseaming 2” away
how many set of punch work required to facilitate proper alignment during reconstruction
2 set
At what temp is welding not allowed
Less than 0 F
when are settlement measurement support to be measure? (2)
- during filling
2. when water is 100%
Welding consumables conform to which specs?
AWS
new material for tank reconstruction shall comply with?
current applicable standards
when is it necessary to remove tack welds?
when manual welding process is used
When is it not necessary to remove the tank welds?
SAW process (submerged arc process)
when to use low h2 electrodes for what materials (2)
- Group Iv , Iva , v, Vi
2. group I / II/ III if t > 1/2”
max out of plumbess?
1/100 of tank total height MAX - 5”
lowest design metal temperature
15 F ABOVE lowest one day mean temp
concrete ring wall NOT used out of levelness allowed?
1/8’ in any 10 feet circumference and 1/2” of average elevation
concrete ring wall IS used out of levelness allowed?
1/8’ in any 30 feet circumference and 1/4” of average elevation
WPS / PQR is accordance to?
ASME IX, API 653, API650
when can preheat or CDW in lieu of PWHT be used for a tank repair?
repairs on nozzles
impact test NOT required, preheat requirement applicable to which material?
P1
impact test IS required, applicable to which material and use what method?
CDW , P1/P2/P3
what welding process can be substitute preheat for the code required PWHT?
SMAW, GMAW, FCAW, GTAW
what min require preheat temp and max interpass temp? if impact testing is not required and CDW?
300F / 600 F
impact testing is not required (CDW) how far past the weld must preheat be checked?
4” or 4t (greater)
NDE method for new/existing penetration
PT or MT
projection of the bottom plate beyond the outside toe of the shell to bottom weld shall be at least….
3/8”
when can lap patch not be used?
When presence of the produce in the crevice between the lap patch AND shell prevent gas from freeing
lap patch repairs should be? (type of welds)
Full fillet welds - (match the thickness of thinner plate)
NDe required for (2)existing bottom to shell weld
- MT or PT for fulling length under a welded on patch plate
2. additional 6” on each side examined
NDe requirement for bottom plate repair?
VI –> MT/PT –>vaccum box and tracer
what can lap patches NOT be installed over?
rivets, unrepaired cracks, other lap patches , lap welded seams
what is critical zone min thickness requirement?
small of (1/2 t bottom or 50% of tmin of lower shell course), NOT less than 0.1”
