API572 Flashcards
Magnetic flux scanning techniques are also available that provide a fast qualitative technique for the detection of corrosion losses on large surface areas for vessels up to
0.5 in. (1.3 cm) wall thickness.
Radiographs are taken with a ______of known thickness that will show on the developed film of the vessel part in question.
step gauge
API 510 recognizes that corrosion rate, corrosion allowances, rerating, and component assessment by __________ methodology may all be used to establish retirement and next inspection criteria
ASME BPVC Section VIII, Division 2,
API 510 contains additional guidance
on the rating of pressure vessels.
The consequence of possible failure of such parts should be considered when setting these limits. What limtis
minimum thickness values
Safety is the prime factor affecting
retiring thickness
Excessive heat, mechanical shock, corrosion of reinforcing steel, or the freezing of entrapped moisture can cause
cracking in and around supports.
Cracks in concrete or fireproofing may be caused by (5)
excessive heat, poor design or material, mechanical shock, or unequal settlement.
Taking diameter measurements at several points approximately ________ apart can check distortion of cylindrical skirts
60° (1.0 radian)
The inside surface of a skirt sheet is often subject to attack by
by condensed moisture,
Fireproof inspection method (2)
- Visual examination aided by scraping will disclose most defects
- Very light taps with a hammer will disclose lack of bond between concrete fireproofing and the protected steel.
Catalytic reformer equipment operating at temperature more than _____may experience creep embrittlement damage during operation.
900 °F(482 °C)
Recommended resistance is ____ohms or less, and resistanceis not to exceed 25 ohms.
5 ohms
Inspection for CUI should be considered for externally insulated vessels subject to moisture ingress and that operate between __________) for carbon and low-alloy steels, and _____________ for austenitic stainless steels, or are in intermittent service. This inspection may require removal of some insulation. However, visual inspection at ports used for thickness measurement loc
10 °F (-12 °C) and 350 °F (175 °C
140 °F (60 °C) and 400 °F (205 °C)
Under normal conditions, at least ____measurement in each shell ring and one measurement on each head should be taken.
one
Inspect vessels in cyclic service at external supports using either_____(2) for fatigue cracking.
PT or MT
Certain types of corrosion may be found on external surfaces of a vessel. Among these are (4)
atmospheric corrosion, caustic embrittlement, hydrogen blistering, and soil corrosion.
ATM corrosion
In humid areas and in areas where corrosive chemical vapors are present in the air, corrosion of external shell surfaces may be a problem. Vessels operating in a temperature range that will permit moisture to condense are most susceptible. Corrosion of this type is usually found by visual inspection
caustic embrittlement
This type of attack is most likely to occur at connections for internal heating units and in areas of residual or other high stress. The more susceptible areas are around nozzles and in or next to welded seams. Frequently, visual inspection will disclose this type of attack. The caustic material seeping through the cracks will often deposit white salts that are readily visible.
MT (wet or dry), PT, and angle beam UT may also be used to check for caustic embrittlement.
hydrogen blistering
areas below the liquid level in vessels that contain acidic corrosion products are more likely to be subject to hydrogen blistering. Hydrogen blistering is typically found on the inside of a vessel. However, hydrogen blisters may be found on either the ID or OD surface, depending on the location of the void that causes the blistering. Blisters arefound most easily by visual examination. A flashlight beam directed parallel to the metal surface will sometimes reveal blisters. When many small blisters occur, they can often be found by running the fingers over the metal surface.
soil corrosion.
The most severe corrosion will usually be found between ground level and up to several inches below. Visual examination, supplemented by picking and tapping, will disclose most faults. This corrosion will be particularly intense in areas where cinder fills were used or where acid splash-over has occurred.
Unless readily visible, leaks are best found by (2)
pressure or vacuum testing the vessel.
If visual inspection is not sufficient (often the case in the detection of amine and deaerator cracking), ____(7) analysis may be used to locate and provide additional information on the structural significance of cracks or other discontinuities
wet or dry MT, angle beam UT, PT, or acoustic emission .
The wet fluorescent magnetic particle technique (WFMPT) analysis is ____sensitive than dry MT techniques
more
A check of the skin temperature of the metal in the hot spot area can be made by using a (4)
portable thermocouple,
infrared equipment, or
temperature-indicating crayons or
special paints.
Using replication techniques or taking a material sample (a boat or other sample) should be considered if carbon steel temperatures were in the range of________
750 °F to 1000 °F
depending on operating conditions and alloy , or if temperatures in the creep range are suspected, an experienced
metallurgist or engineer should be consulted.
Austenitic stainless steels are particularly susceptible to (2)
polythionic acid stress corrosion cracking (PASCC)
and
chloride corrosion
Areas of the vessel opposite inlet nozzles maybe subject to (2)
impingement attack or erosion.
Vessels in water service, such as exchangers or coolers, are subjected to maximum corrosion where the water temperatures are
highest.
corrosion may occur where dissimilar metals are in
close contact.
Cracks in vessels are most likely to occur where there are sharp changes in shape or size or near welded seams, especially if ______is applied.
high stress
When materials flow at high velocities in exchanger units, an ________can be expected if changes are made in the direction of flow.
accelerated attack
Shells of vessels _____to inlet impingement plates are susceptible to erosion
adjacent
If large areas are deeply corroded, _____may be necessary.
abrasive blasting
_______ of the vessel should be inspected for corrosion, erosion, hydrogen blistering, deformation, cracking, and laminations.
All areas
Pitting corrosion can usually be found by scratching suspected areas with a __________
pointed scraper.
When cracks are suspected or found, their extent can be checked with (2)__NDE_______.
PT or MT (wet or dry) techniques.
_______inspection methods provide a volumetric inspection of potential flaw areas.
Angle beam UT
The most sensitive method of locating surface cracking is the ______method. Other valuable methods are the dry MT, PT, UT, or radiographic methods.
WFMPT
Examination for cracking should include pressure boundary welds and heat-affected zones up to ___ from the welds.
4”
____ is the primary recommended internal examination method for Deaerators . Other techniques include ACFM and surface eddy current.
WFMPT
Erosion is characterized by a ________ marked absence of the erosion product, and metal loss,
smooth, bright appearance,
Areas directly above and below the liquid level in vessels with a process containing acidic components may be subject to
hydrogen blistering
High-temperature hydrogen attack (HTHA) is a damage mechanism that reduces the______ and___(2) of steel by a high temperature reaction of absorbed hydrogen with carbon in the steel resulting in decarburization and internal fissuring.
strength and ductility
Shell and tray surfaces in contact with tray packing should be examined for possible _________
loss of metal by corrosion.
MT inspection cannot be used on ____materials.
austenitic
metallic liner inspection (2)
- UT thickness instrument.
2. remove a small section and check it with calipers
Bulges and buckling often occur in metallic linings and usually indicate that _____or ____exist in the bulged section of the lining or that ____ exist in the adjacent welds.
cracks or leaks / pin holes
The bulges are formed either by the expansion or buildup of a material that seeps behind the lining during operation or by __________
differential thermal expansion.
An AUT can provide the most reliable NDE of flaws detected in the lining or base material. Although these techniques can be applied at ambient or elevated vessel temperatures, flawsizing is most accurate at or near __________
ambient temperatures.
Removal of representative lining sections to permit visual examination of the vessel wall is always
preferred if feasible.
(3) are all indications that openings exist in the non metallic lining.
Bulging, blistering, and chipping
Considerable care should be exercised when working inside vessels lined with (4)________. These coatings are highly susceptible to mechanical damage.
glass, rubber, plastic sheets, or paint
. Bulging can be located visually and is usually accompanied by __________
cracking.
The sound and feel of ______ on loose concrete lining usually make such looseness evident.
light hammer tapping
_____examination will reveal most mechanical damage (dents, gouges, and cracks).
Visual
ET, alternating current field measurement, and UT methods are available for the detection of ________
surface breaking flaws.
(2) are used to analyze flaws, usually in welded seams, that are not visible on the surface of the metal.
Radiography and angle beam UT
(3)_______ are three methods of detecting metallurgical changes.
Hardness, chemical spot, and magnetic tests
_____ can be used to detect faulty heat-treating, carburization, nitriding, decarburization, and other processes that cause changes in hardness.
Portable hardness testers
It is not recommended to hammer test objects under
pressure.
_______analysis has been developed for use in conjunction with pressure testing or during equipment cooldown
acoustic emission
(2) methods should be used on major repairs, and if required by the applicable construction code, (2) should also be performed.
MT and PT / radiographic, or angle beam UT examination
The two most common types of trays are _____
cascade trays are shed trays and disk/donut trays.
sieve trays can be subdivided into (2)
single-flow and dual-flow trays.
Dual-flow trays are customarily used for processes that exhibit______
heavy fouling due to the formation of precipitates or polymers.
Valve trays can be subdivided into (2)
fixed valve and floating valve trays. .
Bubble caps remain in service throughout the industry in systems where ____liquid flow rates and ____variations in vapor flow and resistance to heavy fouling are required.
low / high
packing has the advantage of being able to handle ____liquid rates with _____efficiencies and with lower-pressure drop than all but the newest of the high-capacity trays
larger / higher
Most structured packing isinstalled such that each succeeding layer is ____ out from the previous layer
90°
structured packing provides ____capacity and ____pressure drop than crosscurrent trays or random packing.
higher / lower
Skirt Fireproofing—Any crack over ____in. in width, and any crack that has displacement or bulging of theconcrete fireproofing material should be investigated for corrosion under fireproofing (CUF).
0.250
Preliminary, or “dirty inspections” should be performed upon opening th eexternal manways, before
whatever forced ventilation is to be installed is installed.
what metal is more prone to denzintification
brass
Portable hardness testers can be used to detect faulty (4)
heat-treating, carburization, nitriding, decarburization, and other processes that cause changes in hardness.
Hardness, chemical spot, and magnetic tests are three methods of detecting
metallurgical vchanges.
The use of NDE devices for inspection is subject to safety requirements customarily in_______ The use of hydrocarbon-based magnetic particle (MT) and/or liquid penetrant (PT) can change the environment of a confined inspection space.
gaseous atmospheres.
Cracks in concrete or fireproofing may be caused by (4)
excessive heat, poor design or material, mechanical shock, or unequal settlement.
hair-like appearance. on concrete, Such cracks are _______serious unless they expose the steel to corrosion.
not usually
Distortion of anchor bolts may indicate serious
foundation settlement.
_____may also be used to test bolts
UT
_______ is one of the best methods of protecting steel structures from corrosion.
Galvanizing
GUy wire inspection? (2)
Visual examination /
AUT inspection is typically necessary to scan the entire length of guy wires for condition and proper loading.
Guy wires clips should be spaced at least _____ apart to insure maximum holding power.
six rope diameters
If there is any evidence of distortion or cracks in the area around the nozzles,_______
all seams and the shell in this area should be examined for cracks.
(3)are the types of paint failures usually found.
Rust spots, blisters, and film lifting
_________(Paint failure type) is not easily seen unless the film has bulged appreciably or has broken.
Film lifting
The most likely spots to search for paint failure are in _____, in constantly moist areas, and at welded or riveted vessel seams.
crevices
(2) methods can provide an on-stream assessment of areas with high moisture and can provide a screening assessment for CUI.
Neutron backscatter / Thermography
Under normal conditions, at least one measurement in each (2) should be taken.
shell ring and one measurement on each head
areas below the liquid level in vessels that contain acidic corrosion products are more likely to be subject to
hydrogen blistering.
(3) ________ require thorough cleaning over wide areas.
Extensive cracking, deep pitting, and extensive weld damage
The bottom head and shell of fractionators processing high-sulfur crude oils are susceptible to _______
sulfide corrosion.
Cracks occurs (4)
a) attachment weld(s) of an internal component,
b) main weld seams,
c) gasket grooves (ring joint-flanges),
d) nozzle attachment welds
When damage is slight, ______may be sufficient on small vessels, but more measurements should be taken on large vessels.
one thickness measurement on each head and each shell course
When damage appears to be widespread, ______assure an accurate determination of the remaining thickness.
enough readings should be taken to
Shells of vessels _____to inlet impingement plates are susceptible to erosion.
adjacent
Vessels in water service, such as exchangers or coolers, are subjected to maximum corrosion where the water temperatures are
highest.
REboiler - The point where the _____ stream returns to the tower may be noticeably corrode
hot process
wet hydrogen sulfide (H2S) or cyanide environments are susceptible to cracks in their (2) _______
welds and weld heat-affected zones.
vessels where sludge may settle out, _____corrosion sometimes occurs.
concentration cell
welds in vessels constructed (2) ______should be checked for cracks
of high-strength steels [(above 70,000 lbf/in.2
tensile (483 MPa)]
OR
coarse-grain steels
tower trays primary NDE?
visual (UT if needed)
Erosion or corrosion at the baffles of exchangers will often show up as a series of regularly spaced rings when a _________to the shell surface.
flashlight beam is place parallel
Areas directly above and below the liquid level in vessels with a process containing acidic components may be subject to
hydrogen blistering
Out-of-roundness can be caused by _________
welding
Deaerators in boiler feedwater systems can be susceptible to _____from a corrosion fatigue mechanism
cracking
hydrocrackers and hydrotreaters, use complete weld overlay that uses stabilized ________
austenitic stainless steel
Bulging can be located visually and is usually accompanied by ________
cracking.
breaks in coating are sometimes called
holidays.
the _____method of inspection for leaks in paint, glass, plastic, and rubber linings
spark tester
excess thickness of the shell or head plates is used
by the designer as nozzle reinforcement
lined vessels are sometimes subject to severe corrosion due to
condensation on the shell behind the insulation
pressure tested for (3)
integrity and tightness and redistribution at defects
pneumatically, a (2)______ should be used to aid visual inspection.
UT leak detector or soap solution or both
min test temp for <2” and >2”
- 10F ABOVE MDMT
2. 30F ABOVE MDMT
min test temp for <2” and >2”
- 10F ABOVE MDMT
2. 30F ABOVE MDMT
when testing a floating-head exchanger with the pressure in the TUBES, removal of the shell cover will reveal the source if the leak is in (3)
the gasket, stay bolts, or tube rolls at the floating head.
when testing a floating-head exchanger with the pressure in the SHELL, removal with the channel cover off will reveal leaking
- tube rolls at the stationary tubesheet, but will not clearly identify the source of leakage at floating tubesheet rolls or floating head gasket leaks.
