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API571 > Module 4 Fatigue SCC > Flashcards

Module 4 Fatigue SCC Flashcards

1
Q

Thermal Fatigue

affected material?

A

all

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2
Q

Thermal Fatigue

Magnitude of the __(2)___

A

temperature swing & frequency

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3
Q

Thermal Fatigue

There is no set limit on swings, but cracking may be suspected if the temperature swing exceeds about _____

A

200°F - 300F

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4
Q

Thermal Fatigue

where would most stress be located?

A

c. notches and sharp corners

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5
Q

Thermal Fatigue

affected equipment? (6)

A

a. Mix Points
b. Major Problem in Coke Drums
c. S/D and S/U
d. steam-generating equipment at rigid attachments
e. tubes in high temp that penetrate through the cooler waterfall tubes (tubes in the boiler where water is evaporated to steam)
f. steam actuated soot blowers in heater or boilers

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6
Q

Thermal Fatigue

Cracks usually initiate on the surface of the component __or ___

A

ID or OD.

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7
Q

Thermal Fatigue
Thermal fatigue cracks propagate ______to the stress and are usually________. However, cracking may be axial or circumferential of both

A

TRANSVERSE / dagger-shaped

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8
Q

Thermal Fatigue

NDE? most effective

A

PT/ MT / WFMT / ECT/ ACFM / EMAT/VT

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9
Q

Thermal Fatigue

best prevent through?

A

design / operations

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10
Q 
Thermal Fatigue
other prevention (3)
A

b. Incorporate sufficient flexibility
i. Drain lines should provided on soot blowers
c. a liner or sleeve installed to prevent colder liquid from contacting

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11
Q

Mechanical Fatigue

typically well below the ____ of the material

A

YS

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12
Q

Mechanical Fatigue

affected material?

A

all engineered alloys

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13
Q

Mechanical Fatigue\

___(2)___exhibit an endurance limit below which fatigue cracking will ____occur regardless of the number of cycles

A

CS and Titanium / NOT

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14
Q

Mechanical Fatigue
___(3), and most other non-ferrous alloys have a fatigue characteristic that does NOT exhibit an endurance limit (fatigue fracture can be

A

300 / 400 Series SS, aluminum

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15
Q

Mechanical Fatigue
Heat Treatment can have an effect on fatigue resistant of a metal - _______can improve fatigue resistance of CS/low alloys

A

quenching and tempering

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16
Q

Mechanical Fatigue

The ratio of endurance limit to ___is typically between 0.4 and 0.5

A

UTS

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17
Q 
Mechanical  Fatigue
affected equipment (7)
A

a. socket welds and small bore piping
b. equipment not properly supported
c. safety RV that are subject to chatter
d. high pressure drop CV and steam reducing stations (vibration problems)
e. Rotating shafts on pumps/compressors have stress concentration due to changes in radii and keyways
f. heat exchanger tubes susceptible to vortex
g. transient conditions (S/U & S/D)

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18
Q

Mechanical Fatigue

appearance?

A

clam shells /beach mark

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19
Q

Mechanical Fatigue

best defense?

A

good design

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20
Q

Mechanical Fatigue

_____to rely on the NDE methods for routine. What NDE to use for cracks???

A

impractical / PT , MT , SWUT

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21
Q

Corrosion Fatigue

factor (2)

A

corrosive environment and cyclic loading

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22
Q

Corrosion Fatigue

affected material?

A

all metals/ alloys

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23
Q

Corrosion Fatigue

endurance limit?

A

there is none

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24
Q

Corrosion Fatigue

stress concentration is important?

A

yes

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25
Q 
Corrosion Fatigue
affected equipment (3)
A

Rotating equipment, deaerators, cycling boilers

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26
Q

Corrosion Fatigue

appearance? (4)

A

a. relatively straighter
b. very little plastic deformation
c. in cycling boilers damage appears on the water side of buckstay.
d. transgranular, not branched

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27
Q

Corrosion Fatigue

prevention? for rotating equipment/deaerators/cycling boilers?

A

a. Rotating equipment - upgrade to corrosion resistant material, coating, use corrosion inhibitors
b. Deaerators - ensure the use of proper feed water and condensate chemical control
minimize residual stress
c. Cycling boilers - start up slowly

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28
Q

Chloride SCC

need ____

A

water

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29
Q

Chloride SCC

what material is high resistant?

A

Nickel based /

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30
Q

Chloride SCC

which SS not susceptible?

A

400SS

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31
Q

Chloride SCC

what is susceptible?

A

All 300 series SS is highly susceptible (8-12% Ni)

duplex SS are more resistant

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32
Q

Chloride SCC

_____will increase the likelihood for cracking, but there is no identified

A

O2

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33
Q

Chloride SCC
ClSCC usually occurs at pH values above ____
ClSCC tendency ______in the alkaline pH region.

A

2 …./ decreases

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34
Q

Chloride SCC

temp when it occurs?

A

> 140F

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35
Q

Chloride SCC

>35% ni / >45% Ni

A

high resistant / immune

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36
Q

Chloride SCC

% of Ni that is susceptible

A

8-12%

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37
Q

Chloride SCC

appearance (2)

A

c. spider web

d. craze cracking

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38
Q

Chloride SCC

surface breaking cracks in ____ or _____

A

process / externally

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39
Q

Chloride SCC
even if process side has no Chloride, piping or equipment operate _____expose to alternating wet / dry conditions externally

40
Q

Ammonia SCC

wet ammonia critical factors? what metal susceptible

A

i. water required
ii. Oxygen required
Any Temp

Copper

41
Q

Ammonia SCC

Dry ammonia critical factors? what metal susceptible

A

a. Dry Ammonia cracks Steel (<0.2% water)
i. High temp -> increase cracks
ii. Oxygen any small amount

Carbon steel

42
Q

Ammonia SCC

wet ammonia critical factors?(5) what metal susceptible

A 
water required
Oxygen required
Any Temp
stress
pH > 8.5
Copper zinc content (>15%)
43
Q

Ammonia SCC

Dry ammonia critical factors?(3) what metal susceptible

A

a. Dry Ammonia cracks Steel (<0.2% water)
i. High temp -> increase cracks
ii. Oxygen any small amount

Carbon steel

44
Q

Ammonia SCC

what % of zinc is susceptible?

45
Q

Ammonia SCC
for wet
pH >

46
Q

Ammonia SCC

for dry water %?

47
Q

Ammonia SCC

for dry , amount of o2?

48
Q

Ammonia SCC

affected equipment?

A

a. copper zinc alloy tube in heat exchangers

b. where ammonia is present , BFW, CW, acid neutralizer

49
Q

Ammonia SCC

ammonia is used as

A

neutralizer for acid

50
Q

Ammonia SCC

appearance

A

bluish color crack

51
Q

Ammonia SCC

prevention for copper (2) / CS (5)

A 
Copper
a. <15% zinc has improved resistance 
b. 90-10 / 70-30 Cu-Ni have low susceptibilities. 
CS
a. Add water to >0.2% 
b. vapor phases could have less  than 0.2% water present due to partitioning of ammonia in water phases
c. low strength steels (<70 KSI)
d. prevent ingress of o2
e. N2 purge
52
Q

Ammonia SCC

inspection? for copper and CS

A 
Copper 
a. pH and ammonia content draw samples
b. Tubes use ECT or VT
CS
a. WFMT is typically used
b. angle beam UT (SWUT or PAUT) can be performed from the outside surface;
53
Q

Ethanol SCC

affected equipment primarily

A

Carbon Steel

54
Q

Ethanol SCC

ethanol SCC has ____been reported in FGE manufacturers

55
Q

Ethanol SCC

a. cracks both ____ to weld OR ____

A

parallel / transverse

56
Q

Ethanol SCC

_____has been found in FGE meeting ASTM D4806 specs + water content

57
Q

Ethanol SCC

Concentration of Ethanol ppm?

A

as little as 20 ppm

58
Q

Ethanol SCC
water %?

what may be added to __________for ____corrosion?

A

• Water – 0.1 to 4.5% vol%

  • Corrosion inhibitor may be added , but effect is not understood for Mitigation for general corrosion.
59
Q

Ethanol SCC

most important factor?

A

• Aeration (oxygen) is the most important factor for determining ethanol SCC susceptibility.

60
Q

Ethanol SCC

prevention? (2)

A

a. reduce by PWHT

b. apply coating

61
Q

Ethanol SCC

______chloride content tends to increase severity of cracking

A

Increasing

62
Q 
Ethanol SCC
inspection? 
a. \_\_\_\_\_ to predict and detect
b. routine inspection is \_\_\_\_
c. efforts need to be focused on prevention
d. WFMT is \_\_\_\_\_Method
e. ACFM for less surface prep
A

difficult

not effective

PREFERRED

63
Q

Ethanol SCC

related mech

A

Alkanies SCC

64
Q

Ethanol SCC

related mech

A

Alkanies SCC

65
Q

Liquid Metal Embrittlement

how fast can cracking happen with molten metal

A

as quick as seconds

66
Q

Liquid Metal Embrittlement

LME occurs with low melting point metals such as __(6)__

A

zinc, mercury, cadmium, lead , copper and tin

67
Q

Liquid Metal Embrittlement

LME is relevant and of most concern after_______containing mercury that leaks into/onto equipment.

A

a fire after a failure instrument

68
Q

Liquid Metal Embrittlement

Most RELEVANT example

A

is refining is 300 SS in or near contact with galvanized steel where zinc melts during a fire and crack SS

69
Q

Liquid Metal Embrittlement

where is mercury found?

A

in some crude oil and can condense in the atmospheric tower overhead

70
Q

Liquid Metal Embrittlement

a. appear as
b. can only be confirmed through metallography

A

brittle cracks in otherwise ductile material

71
Q

Liquid Metal Embrittlement

a. cracks are often _______
b. high density of mercury, ______ can be used to located deposit inside equipment
c. existence through ______

A

a. visually apparent
b. RT
c. Metallography

72
Q

Polythonic Acid SCC aka graindropping
affected material?
normally occur?

A

sensitized 300S and some 800/600 alloys

b. normally occur in s/d & s/

73
Q

Polythonic Acid SCC aka graindropping

description

A

Sulfur reacts with air (oxygen) and moisture to form sulfur acids (Polythionic acid).

74
Q

Polythonic Acid SCC aka graindropping

Material must be in a susceptible or ______condition.

A

“sensitized”

75
Q

Polythonic Acid SCC aka graindropping

a. Low carbon grades “L” (0.03%C) are ____susceptible
b. 304/304H & 316/316H are ______susceptible to sensitizing

A

a. less

b. more

76
Q

Polythonic Acid SCC aka graindropping

Sensitization definition?

A

is the loss of alloy integrity. It results from chromium depletion

77
Q

Polythonic Acid SCC aka graindropping

Sensitization temperature it occurs at?

A

700-1500F.

78
Q

Polythonic Acid SCC aka graindropping

__(2)___ has a significant effect on sensitization susceptibility.

A

carbon content and thermal history

79
Q

Polythonic Acid SCC aka graindropping

__(2)___ has a significant effect on sensitization susceptibility.

A

carbon content and thermal history

80
Q

Polythonic Acid SCC aka graindropping

Sensitization is the loss of alloy integrity. It results from chromium depletion refer to the _________(3)___ dependent formation of Cr carbides .

A

composition/time/temperature

81
Q

Polythonic Acid SCC aka graindropping

. typically occurs ____to welds

82
Q

Polythonic Acid SCC aka graindropping

corrosion or loss in thickness is usually _____

A

negligible

83
Q

Polythonic Acid SCC aka graindropping

Chemically stabilized grades __(2)___ have improved resistance to PASCC.

84
Q

Polythonic Acid SCC aka graindropping

Chemically stabilized grades have small amounts of __(2) ___ added.

85
Q

Polythonic Acid SCC aka graindropping

heated the firebox heated ___ the dew point to prevent acid from forming

86
Q

Polythonic Acid SCC aka graindropping

monitoring PTA SCC cracking operation is ____effective

87
Q

Polythonic Acid SCC aka graindropping

Most effective is managed by ____rather than _____

A

prevention / inspection

88
Q

Polythonic Acid SCC aka graindropping

normally occurs in

A

during S/D and S.U

89
Q

Polythonic Acid SCC aka graindropping

___(NDE)____ is MOST common to detect

90
Q

Polythonic Acid SCC aka graindropping

______can be used to determine the degree and extent of sensitization

91
Q

Corrosion Fatigue

inspection for Deaerators?

92
Q

Corrosion Fatigue

inspection for Rotating equipment?

A

VT as well as UT, PT, and MT

93
Q

Corrosion Fatigue

inspection for cycling boilers

A

The first sign of damage is usually a pinhole leak on the cold side of a waterwall tube at a buckstay attachment.
Highly stressed regions in the boiler where cracking can occur can be inspected using angle beam UT (SWUT or PAUT) or EMAT techniques.

94
Q

Corrosion Fatigue
The fatigue fracture surface will appear brittle, and the cracks will be relatively straight, _____, and unbranched. There may be multiple ______cracks

A

transgranular / parallel

95
Q

LME

_____ contributes to crack propagation rates

A

Tensile stress

96
Q

LME
A susceptible metal in contact with a low melting metal at low temperatures may crack later when the temperature rises ____the melting temperature of the low melting alloy

97
Q

PAA
Cracking may propagate rapidly through the wall thickness of piping and components in a matter of
____

A

minutes or hours

API571 (13 decks)

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