API653 API575 Flashcards
atmospheric pressure code?
API650
definition of low pressure storage tanks?
operate at pressures in their gas or vapor spaces exceeding the 2.5 pounds per square inch gauge
pressure permissible in API Standard 620
API2000?
Venting requirement
External corrosion (5)
a. External (underside) tank bottom corrosion results from contamination in the pad. Cinders contain sulfur compounds that become very corrosive
when moistened.
b. Electrolytic corrosion (pitting type) results when clay, rocks, oyster shell, wooden grade stakes, etc., come in contact with the underside bottom, as
they attract and hold moisture.
c. Poor drainage from faulty pad preparation.
d. Lower external shell corrosion due to:
i. Settlement, with corrosion at soil grade line
ii. Casual water collection point
iii. Insulation moisture “wicking”.
e. Shell appurtenances are subject to crevice corrosion at non-seal welded
joints (angles/flats).
internal corrosion (4)
a. Primarily dependent on product stored.
b. Corrosion resistant linings are most common preventative.
c. Normal locations and causes are:
i. Vapor space (above the liquid). Most commonly caused by H2S vapor,
water vapor, oxygen or a combination of the three.
ii. Liquid area. Most commonly caused by acid salts, H2S or other sulfur
compounds.
d. Other forms of internal attack, considered as forms of corrosion are:
i. Electrolytic corrosion.
ii. Hydrogen blistering.
iii. Caustic Embrittlement.
iv. Graphitic corrosion (cast iron parts). (?)
v. Dezincification (brass parts). (?
areas covered by the stored liquid, corrosion is commonly due to (4)
acid salts, hydrogen sulfide or bottom sediment and water
internal inspection test for FULL bottom? (3)
inspection of the entire tank bottom by using
- Magnetic Flux Leakage
- UT type techniques
- Hammer testing
Protective Coating failure (5)
Rust spots, blisters, peeling, cracking and coating due to lack of adequate bond, are all types of common paint failure.
Cracks can result from a wide variety of causes. The more frequent causes are: (5)
i. Faulty welding.
ii. Unrelieved stress concentrations (i.e., stress raisers) around fittings or
appurtenances.
iii. Stress caused by settlement or earth movement, especially differential settlement
iv. Vibration
v. Poorly designed repair or “sloppy” craftsmanship.
CUI is most aggressive at what temp?
170-230F
How to detect hot spots in piping? (2)
- thermography
- neutron back scatter
except for cast iron parts, coils and support should be…inspected by NDE (2)
UT or Hammer tested
Thoroughly method of inspection non metallic lining?
Holiday testing
grounding connection should not exceed … ohms?
25
How often should flame arrestors be inspected? (2)
- appropriate intervals
- after an explosion in a tank connected to a gas collecting system
cone roof can be as large as?
300 feet
API620 - atmosphere pressure means not exceeding what?
internal pressure not exceeding the weight of the roof plates
API650 atm pressure define?
up to 2.5 psi
API 650 atm pressure mean?
not exceeding 2.5 psi
api 572
inspection of PV
2 most common types for tank roofs?
- fixed
2. floating
cone roof are normally self-supporting for what diameters?
60 feet or less
What external floating roof is not permitted per Annex C or API650?
Pan type
What is pan type roof flaw?
Prone to sinking
definition of low pressure storage tanks?
exceeding 2.5 psig but not greater than 15 psig
cone/domed roofs are typically designed for up to what pressure
up to 5 psig
Which type of roof is typically constructed with Aluminum?
geodesic
most common type of floating roof seal?
shoe seal
API 620 appendix R addressed product from what temperature?
40 to (-)60F
What is a recognized tank inspection standards? (4)
- API STD 12R1
- API 653
- EEMUA 159
- STI SP001
chemical in the cinder would cause corrosion?
sulfur
What is not recommend sealant for tanks?
Asphalt impregnated fiberboard
concentration cell corrosion can occur at?
rivet tanks niches
API 571?
Damage mecahnism
crude oil tanks are constructed of what material typically
CS
what causes corrosion in vapor space? (3)
- hydrogen sulfide
- water vapor
- oxygen
caustic cracking is normally on?
coil or heating units
What does it have to contain to causes SCC? (3)
- Ethanol
- DEA
- Caustic
external corrosion can occurs to horizontal tank on
saddle supports
3 late lap welds are prone to ?
leaks
where are crack like flaws typically occur in large storage tanks
shell to bottom welds
large or uneven amount of settle can cause?
nozzles with attached piping become over stressed
API 653 Annex c?
inspection checklist for tanks
inspection plans should be developed by (4)
AI, engineer, CS, and operations
API 580>?
RBI
What are factor of probability of failure (3)
- probable damage mechanisms
- current tank condition
- past inspection effectiveness.
what are factors for consequence of failure? (4)
- potential for injuries
- loss of containment
- environmental impacts
- loss of production
new tanks have their original plate thickness based on? (2)
- specific gravity
- hydro static test requirements
stresses are highest
bottom to shell joint
stresses decrease or increase due to external pressure loadings as you move up in the tank shell?
does not decrease as you move up the tank shell.
pitting of tank bottoms plates is a factor in establish inspection intervals?
YES
pit or a small area corroded down to retirement thickness (4)
- does not weaken the shell plate
- may result in a leak
- does not weaken the shell plate
- should be eliminated
internal inspection is governed by CR at where?
corrosion rate of the tank bottom
similar service is used for what?
tank bottom corrosion rate
product side corrosion is usually cause by
water bottoms
api 2015
safe entry and cleaning
bolts set in concrete is subject to?
crevice corrosion
additional attention should be given to what type of handrails?
tubular
crevices at bracket connections, bolts and nuts, and between stair tread and support angles should be inspected with what (2)
- knife/scrapper
2. hammer
what to do when platform is found to accumulate water?
drill a hole
best way to check for anchor bolt for corrosion? (1)
tapping with hammer
ground connection is govern by what code?
API RP2003 (Protection Against Ignitions Arising Out of. Static, Lightning, and Stray Currents)
which part of the tank experience accerlerated coating failure?
roof
hammer testing should not be done (2)
- hydro
2. in service
special attention should be given to the upper ____ (inch) of uncoated shells of floating tank roofs
24”
wind girders and stiffeners inspection method (2)
VI and hammer
type of deterioration is manifested in tank due to amine or caustic service?
- cracks that start on inside of the tank and progress through the outside
what substances leaking due to cracks caused by caustic?
white salts
what happens if cracks are not thoroughly cleaned caused by caustic?
cracking will get worse
hydrogen blistering normally found where (location )
shell and bottom of tank
hydrogen blister can occur on external and/or internal?
both external / internal
how can you located hydrogen blistering?
VI with light parallels to tank surface
cracks typically occur (3) - what locations
- nozzle connection
- shell to bottom welds
- supports/bracket connections
NDE methods for cracks? (2)
MT or PT
inspection NDE for thinning of head/roof? (2)
UT or MFL
roof inspection by hammer testing what may happens that is NOT good
may dislodge rust scale into store product
how should roof be inspected? What should be put on the roof
plank long enough to span 2 roof rafters
inspector should do walk on?
weld seams
floating roof should be as _____ if volatile liquid is in the tank ..
high as possible
what to do if a tank is half full during the inspection of the floating roof?
(1) perform atm testing if respirator is not worn
2. wear respiratory equipment if no atm testing
3. post a 2nd employee with respiratory equipment
if max operating level is exceed what can happen to the floating roof?
damage to the floating roof seals
what happens if floating roof drains are blocked?
- could sink and/or damage
how many inches of buried piping should removed for inspection?
6-12”
What to do when nozzle distortion is discovered?
clean shell and all seams down to parent metal and examine with PT or MT
flame arrestors routinely ?
inspect for cleanliness and corrosion
if tank is lifted , what test to be done?
hydro
what is a problem for tunneling?
hard to compact the fill in the tunnel area
roof rafters inspected by coupon, requirements?
- 12 x 12
2. round corners
leakage in the roof deck or in the pontoons can cause (2)
- unbalance and
2. roof hang up on the shell
how to control pyrophoric deposition is found in API?
2015
pyrophoric deposition is to be kept
moist
98% sulfuric acid , where would most severe corrosion occur? and why?
liquid to vapor interface, water will float
pipeline breakout tank where is susceptible?
behind floating roof seals
corrosion on floating seals typically occurs as a band of corrosion , and most severe at ?
hAZ
incomplete penetration of circumferential shell weld seams were permitted when?
tank built prior to 7th edition of api650
where in CS tanks are more prone to hydrogen blistering?
contains lamination or slags
SCC thrives at what temp
> 150F
MFL cannot detect?
sharp isolated pitting
what is recommend for assessing soil side corrosion?
coupon
statistical analysis method , how much of tank must be scanned
0.2% to 10% of tank bottom
when using scanning methods to check for tank bottom corrosion, what else should be included?
outer circumference next to the shell
top side and bottom side corrosion is present, what is best inspection?
- MFL and coupon removal
cracks in shell or shell to bottom welds, liquid penetrant or diesel dwell time?
24 hours
aluminum legs should be?
isolated from CS to prevent corrosion
drain lines can be hydro at what pressure for at least 30 min
30 PSIG
if drain lines contain swing joints what pressure tested after 1st test of 30 PSIG
5 PSIG
structural members inside the tank can experience what rate of corrosion?
2x the corrosion on the shell/roof
what to use to measure corrosion on structural members (3)
- UT
- Transfer calipers
- steel rule
check for soundness of structural memebers?
light hammer taps
steam coils should be checked for ?
condensate grooving
what to consider for hydrotesting high strength or high alloy steels
Chloris SCC
if no water for hydo, what pressure can is to be set for pneumatic pressure?
no more than 2” of water pressure
what can be missed for vaccum box for roof seams?
large and small leak may not be detected
APi 334?
leak detection for AST
how many procedure associated with determining the hydraulic integrity?
11
How close must the eyes be for VI
24”
What angle for VI?
angle of not less than 30 degree
VI lumens? general / small anomalies
min 15 foot candles / 25 lumens / 50 foot candles/100 lumens
min dwell time for using penetrating oil/dye penetrant for shell to bottom weld
12 hours
air pressure requirement? for checking the inside surface with an indicator solution
no more than 3” of water pressure
air pressure requirement? for checking the inside surface with 6” of level of water, with an indicator solution
max 9” of water pressure
how to increase effectiveness of tank bottom leak testing?
tapping entire bottom with an air operated hammer
leak testing can be achieved by installing a clay dam around the perimeter of tank and filling with and how many inches?
6 “ height of water
another testing method for bottom tank is use inert gas, what is advantage?
repairs can be made without removing the inert gas and retest is immediate.
key element for to mass balancing is (2)
pressure and temperature
marker chemical leak detection method key is?
injecting a volatile chemical into the process or hydrotest water, and detectors installed below the tank bottoms
chemical marker solution to be ?
1-10 ppm
chemical marker sensor to be what distance away?
no more than 20feet from tank bottom
what sensors are used for AET?
accelermeter
what is limitation of AET?
distinguishing the sound from the leak from ground sounds
leaking rivet can be repaired by ? (3)
- welding
- bolting or re-riveting
- caulking/coating
weld repair on rivet heads or seam should (5)
- use small diameter electrodes
- set welding machine at low amperage
- keep weld beads small
- use back step bead application
- lightly ring weld rivet heads
risk associated with weld repair on rivets
- leak in adjacent seams
- leak in adjacent rivets
- leaks develop at the stopping point of the weld repair
what needs to be done if a door sheet is cut all the way down to shell to bottom weld?
hydro
dual element transducers can measure what “
.05-1”
UT overlap requirement?
min 10% of transducer diameter
large diameter transducer
will not detect small diameter pits
phased array UT? (3)
ultra high data point density , corrosion mapping, discrimination of mid wall anomalies
tanks bottom scanning can successfully scan what % of tanks?
80% of the tank bottom
