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API571 > Module 9 (General Erosion) > Flashcards

Module 9 (General Erosion) Flashcards

1
Q

Erosion / Erosion Corrosion

affect metals? / mostly?

A

all metals, but mostly CS and cooper alloys

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2
Q

Erosion / Erosion Corrosion

critical factor? (4)

A
  1. velocity
  2. impacting particles
  3. hardness
  4. angle of impact
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3
Q

Erosion / Erosion Corrosion

softer alloys such as ____(2) __may subject to _____metal loss under high velocity

A
  1. Cu / Al

2. severe

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4
Q

Erosion / Erosion Corrosion
increasing the hardness of eroding metal component can ________rate of erosion damage. However _____ be effective where corrosion plays a signification role

A

increase / MAY NOT

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5
Q

Erosion / Erosion Corrosion
affected equipment? (4)

  1. __________piping may be subject to erosion-corrosion by ammonium bisulfide
  2. _________ piping and vessels exposed to naphthenic acids in some crude oils
  3. Erosion-corrosion is common in________
  4. Erosion by water droplets in steam systems can be very _______
A
  1. Hydroprocessing reactor effluent piping may be subject to erosion-corrosion by ammonium bisulfide
  2. Crude and vacuum unit piping and vessels exposed to naphthenic acids in some crude oils
  3. Erosion-corrosion is common in acid alkylation systems
  4. Erosion by water droplets in steam systems can be very damaging.
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6
Q

Erosion / Erosion Corrosion

appearance? (2)

A
  1. localized loss in thickness in the form of grooves, gullies, waves, rounded holes, valleys,
  2. These losses often exhibit a directional pattern
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7
Q

Erosion / Erosion Corrosion
prevention
a. Changes in ______ can help mitigate erosion and erosion-corrosion.
B. Improved _________to mechanical erosion is usually achieved by increasing component hardness,
c. Erosion-corrosion is best mitigated by using more ________ alloys and/or altering the _____ to reduce corrosivity..
d. Heat exchangers utilize _________and occasionally tube ferrules to minimize erosion-corrosion problems

A

a. shape, geometry, and materials
B. resistance
c. corrosion-resistant alloys and/or altering the process environment
d. impingement plates

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8
Q

Dissimilar weld metal cracking

most common affected material? ___material welded to _____

A

ferritic material weld to austenitic SS

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9
Q

Dissimilar weld metal cracking

why does cracking occur?

A

high differential thermal expansion stress if having different thermal coefficients

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10
Q

Dissimilar weld metal cracking

thermal expansion differ ____ to ____% = cracking

A

25-30%

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11
Q

Dissimilar weld metal cracking

thermal expansion > ____F can occur

A

500

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12
Q

Dissimilar weld metal cracking

what material has a coefficient close to CS? resulting in ____

A

Ni / lower stress

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13
Q

Dissimilar weld metal cracking
300SS or Nickle based filler metal result in a ______ (mix zoned) of high hardness along the ______line on the ____steel side

A
  1. narrow region
  2. fusion
  3. ferritic
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14
Q

Dissimilar weld metal cracking ***

crack form ______ of the weld in the ____ of the ____material

A
  1. at the toe
  2. HAZ
  3. ferritic
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15
Q

Dissimilar weld metal cracking

what based filler is best?

A

Ni

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16
Q

Dissimilar weld metal cracking

inspection? Location/ method

A

near the ID
/
PT WFMT or angle beam

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17
Q

Thermal shock

occurs when?

A

colder liquid contact a much warmer metal surface

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18
Q

Thermal shock

affectsed material

A

all metals

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19
Q 
Thermal shock
critical factor (2)
A
  1. magnitude of temp differential
    and
    2.coefficient
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20
Q

Thermal shock

What metal has higher coefficient than carbon and alloy steel or nickel based alloys and more likely to see high stress?

A

SS

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21
Q

Thermal shock

loss of what properties is more susceptible to thermal shock?

A

Cr-Mo (due to temper embrittle ment)

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22
Q

Thermal shock

preventition

A

minimize situation where rain or fire water deluge can contact hot equipment

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23
Q

Thermal shock

related mech? (2)

A
  1. thermal fatigue

2. short term overheating

24
Q

Cavitation

affected equipment? (2)

A
  1. piping down stream of orifices’ or CV

2. temp approaching boiling point

25
Q

Cavitation

____accelerated the caviation?

A

corrosion (cavitation corrosion)

26
Q

Cavitation

appearance? (2)

A

share edge pitting

but may also be a gouge appearance

27
Q

Cavitation

prevention?

A

avoid condition that allow absolute pressure to fall below the vapor pressure

28
Q

Cavitation

inspection? (4)

A

VT/UT/RT

Acoustic

29
Q

Refractory Degradation
critical factor
“a. (_______3) are the keys to minimizing damage
b.___(3)___ should be in accordance with the manufacturer’s specifications and the appropriate ASTM requirements.
f) Anchor materials need to be compatible with the __________ of the base metal.
g) Anchors need to be resistant to _______in high-temperature services.
h) Anchors need to be resistant to condensing _______ in heaters and flue gas environments.”

A

“a. Refractory design, selection, and installation

b. Dryout schedules, cure times, and application procedures
f) thermal coefficient
g) oxidation
h) sulfurous acid

30
Q

Stress Relaxation cracking (Reheat cracking) - NL
description
Cracking of a metal due to stress relaxation via grain boundary strain in the creep temperature range during ___or_______

A

PWHT / in service at elevated temp

31
Q 
Stress Relaxation cracking  (Reheat cracking) NL
affect material (3)
A

a. Cr-Mo especially 2 - 1/4 - 1mo with vanadium added

b. low Cr

32
Q

Stress Relaxation cracking *** NL

what is very susceptible

A

HSLA

33
Q

Stress Relaxation cracking (Reheat cracking) NL

critical factor?(6)

A

a. type of material (chemical composition, impurity elements),
b. grain size
c. weld metal and base metal strength
d. residual stresses from fabrication (cold working, welding)
e. section thickness (which controls restraint and stress state),
f. notches and stress concentrators, and welding and heat treating applied.

34
Q

Stress Relaxation cracking (Reheat cracking) NL

affected equipment

A

high stress area (thickner)

35
Q

Stress Relaxation cracking (Reheat cracking) NL
appearance
SRC is normally more prevalent where _______size exists, particularly in the low-alloy steels. Large grain size means less total grain boundary volume to accommodate the creep strain, i.e. the creep strain is concentrated in a relatively small grain boundary volume.

A

large grain

36
Q

Gaseous O2 enhanced ignition and combustion (NL)

what o2 % needed ?

A

> 25%

37
Q

Gaseous O2 enhanced ignition and combustion (NL)

affected material and pressure (2)? and what is fire resistance? (2)

A

CS - 15PSIG

SS- 200PSG

Cu-Ni are fire resistance

38
Q

Gaseous O2 enhanced ignition and combustion (NL)

what material is avoided? (2)

A

Ti and Al

39
Q

Gaseous O2 enhanced ignition and combustion (NL)

prevention (2)

A

d) Minimize lubricants and use only “oxygen-compatible” lubricants
g) Minimize sudden changes in pressure in the system.

40
Q

Gaseous O2 enhanced ignition and combustion (NL)

inspection?

A

Most commercial oxygen is dry and non-corrosive at normal ambient temperatures. this type of damage CANNOT be inspected for in advance

41
Q

Dealloying NL

description

A

SELECTIVE corrosion mechanism in which one or more constituents of an alloy are preferentially attacked, leaving a lower-density (dealloyed)

42
Q

Dealloying NL

appearance

A

porous structure.

43
Q

Dealloying NL

affected material

A

Cu-alloys as well as alloy 400

44
Q

Graphite corrosion of Cast Iron
description
a) Cast irons are comprised primarily of graphite particles embedded in an iron matrix. Graphitic corrosion is a form of _______in which the iron matrix is corroded, leaving behind corrosion products and porous graphite

A

a. dealloying

45
Q

Graphite corrosion of Cast Iron
description
Attack results in a porous structure with a loss of ____(3)_____It usually occurs under (2)

A

strength, ductility, and density

low- pH and stagnant conditions,

46
Q

Graphite corrosion of Cast Iron

affect material and not affected?

A

a. Primarily gray cast iron,

b. White iron is not subject to this damage because there is no free graphite.

47
Q 
Graphite corrosion of Cast Iron
critical factor (5)
A

exposure conditions, including temperature, degree of aeration, pH, and exposure time.

48
Q

Graphite corrosion of Cast Iron

occurs in the presence of _____ and below ___F

A

moisture or an aqueous phase,

below 200 °F (95 c) c.

49
Q

Graphite corrosion of Cast Iron

Damage _____with ____ temperature and aeration, and reduced pH

A

increase / increase

50
Q

Graphite corrosion of Cast Iron

occur during ___condition when high concentrations of sulfates are present.

A

stagnant

51
Q

Graphite corrosion of Cast Iron
appearance
c) The damage may not be noticeable upon ____ even where the full wall thickness is degraded.
d) Damaged areas will be____(2)___ or gouged with a knife or hand tool

A

VT

soft and easily cut or gouged

52
Q

Graphite corrosion of Cast Iron
appearance
c) The damage may not be noticeable upon ____ even where the full wall thickness is degraded.
d) Damaged areas will be____(2)___ or gouged with a knife or hand tool

A

VT

soft and easily cut or gouged

53
Q

Dealloying NL

Dealloying in brasses is visually evident by a _____ copper color instead of the yellow brass color.

A

reddish,

54
Q

Higher ______containing alloys are used for improved resistance to naphthenic acid corrosion

A

molybdenum

55
Q

Refractory

(NDE) ___ are used to detect refractory loss on stream.

A

IR scans

API571 (13 decks)

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