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API571 > Module 5 Hydrogen cracking > Flashcards

Module 5 Hydrogen cracking Flashcards

1
Q

Hydrogen Embrittlement

description loss of?

A

loss of ductility , strength, and/or fracture toughness

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2
Q

Hydrogen Embrittlement

what happens to the H+?

A

H+ get between grain boundaries

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3
Q

Hydrogen Embrittlement
affect material?
AND _____ STEELS

A
  • Carbon steel
  • Low alloy steels,
  • HIGH STRENGTH steels,
  • 400 Series SS,
  • Precipitation hardenable stainless steel,
  • Duplex stainless steel
  • Some high-strength nickel-based alloys
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4
Q

Hydrogen Embrittlement

which material is not affected?

A

300 SS

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5
Q

Hydrogen Embrittlement

critical factor? (4)

A
  1. concentration
  2. Stress
  3. Temp
  4. Material
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6
Q

Hydrogen Embrittlement

effects of temperature?

A

effects decrease with INCREASING temps

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7
Q

Hydrogen Embrittlement

temperature range?

A

AMBIENT temp is most pronounced …. decrease rapidly at 150F and disappears >300F

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8
Q

Hydrogen Embrittlement

strength and hardness

A

must be high

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9
Q

Hydrogen Embrittlement

hydrogen must be at critical ____

A

concentration

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10
Q

Hydrogen Embrittlement

where does hydrogen come from? (6)

A
  1. electrodes
  2. corrosion reactions
  3. high temp >400F in h2 gas
  4. cleaning and pickling
  5. high strength bolts plated with cadmium
  6. cathodic protection
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11
Q

Hydrogen Embrittlement

is HE reversible and when?

A

Yes/ when no cracking has occured

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12
Q

Hydrogen Embrittlement

when temp to bake out Hydrogen

A

600F

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13
Q

Hydrogen Embrittlement
affected equipment?
1. service that contain ____ OR _____
2. corrosive service containing _______and/or
contaminated with recombination poisons
3. hydrogen service above _________ after cool down
4. weld HAZ with HB____________
5. storage sphere b/c ______________
6. ____and _____made of high strength are more prone

A
  1. wet H2s or sour water
  2. sulfur
  3. e above 400F
  4. > 225
  5. > 70KSi
  6. bolts and spring
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14
Q

Hydrogen Embrittlement

what are the corrosion reaction ? (2)

A

sulfur and arsenic - they act as atomic H2 recombination plosions and form h2 gas

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15
Q

Hydrogen Embrittlement
appearance?
cracking is typically _____. In high strength steels it is often _______

A

branched / intergranular

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16
Q

Hydrogen Embrittlement

a. HE____ visible only appear when cracking
b. can initiate ____but most is ____
c. HE at ____stress
d. little evidence of ____

A

a. is not
b. subsurface / surface
c. high
d. deformation

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17
Q

Hydrogen Embrittlement
• Maximum hardness is often held to _____HB.
• High strength bolts, such as ASTM A 193 Grade
B7, should _____ used.

A

200

not be

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18
Q

Hydrogen Embrittlement

HE is ____cumulative

A

not

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19
Q

Hydrogen Embrittlement
A. heavy wall equipment in hot hydrogen service require _____S/D & S/u to control the pressurization sequence as a function of temp.

A

CONTROL /

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20
Q

Hydrogen Embrittlement
If the source of hydrogen is a low-temperature aqueous environment, hydrogen flux can be monitored using ______
.

A

specialized instruments.

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21
Q

Hydrogen Embrittlement

NDE to use?

A

B. PT MT WFMT, Angle Beam,

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22
Q

Hydrogen Embrittlement

NDE to not use

A

c. RT/UT not to be used

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23
Q

Wet H2S

4 damage?

A
  1. Hydrogen blistering
  2. HIC
  3. SOHIC
  4. SSC
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24
Q

Wet H2S -
description?
Form of HE but occurs in high ____
steels or at local high ____areas (such as HAZ)

A

hardness / hardness

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25
Q

Wet H2S -

critical factors? (4)

A
  1. Environmental conditions (pH, H2S level, contaminants, & temperature),
  2. material properties
  3. stress
  4. Water
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26
Q

Wet H2S -

Must have ____presense

A

WATER

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27
Q

Wet H2S -

related to _____and ____of h2

A

absorption / permeation

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28
Q

Wet H2S -
Hydrogen permeation increases with increasing _____partial pressure Partial Pressure = (H2S Concentration X Operating Pressure)

A

H2S

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29
Q

Wet H2S -

min PPM of H2S?

A

50 ppm of H2S as min concentration

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30
Q

Wet H2S -

min pH? and increase at both high and lower pH

A

7

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31
Q

Wet H2S -

effects of contaminants?

A
  • salt or other than decrease pH (increasing CR will increase hydrogen permeation).
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32
Q

Wet H2S -

effect of HCN (Cyanide)?

A

increase CR (weakens protective films)

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33
Q

Wet H2S -

temperate range?

A
  • ambient to 300°F (though sometimes higher) - Blistering, HIC and SOHIC
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34
Q

Wet H2S -

Hardness – Primarily an issue with SSC when weld hardness >____ HB

A

237

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35
Q

Wet H2S -
• Blistering and HIC are strongly affected by the presence of ____and _____which provide sites for diffusing hydrogen to accumulate.

A

inclusions / laminations

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36
Q

Wet H2S -
prevention?
• Use ____, ____ steel

A

a. clean / resistant (killed)

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37
Q

Wet H2S -
prevention?
b) PWHT
c) Control weld hardness to less than ____HB. (NACE RP0427)
d) Use ASTM _____ bolts. They are softer and lower strength than B7 bolts.
e) Use carbon steels with Carbon Equivalents (CE) less than ____

A

200

A B7M

0.43.

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38
Q

Wet H2S - Hydrogen Blistering

appearance?

A

Bulges and/or cracking (both can be internal or external) - primarily on ID surface

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39
Q

Wet H2S affected material? for blistering / HIC/ SOHIC

A

• Carbon steel, and in the case of SSC, low-alloy steels, and martensitic stainless steels

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40
Q

Wet H2S - Hydrogen Blistering

description?

A

hydrogen diffuses into the steel

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41
Q

Wet H2S - Hydrogen Blistering

where is it rare to see it?

A

seamless pipes

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42
Q

Wet H2S - Hydrogen Blistering

common to see it where?

A

vessels and larger diameter seam- welded pipe (which are usually made from plate

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43
Q

Wet H2S - Hydrogen Blistering

temperature for Blistering, HIC and SOHIC

A

ambient to 300°F (though sometimes higher) -

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44
Q

Wet H2S - Hydrogen Blistering / HIC are affected by? (2)

A

inclusion and laminations

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45
Q

Wet H2S

blistering, HIC, SOHIC damage are NOT related to _______

A

hardness.

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46
Q

Wet H2S - blistering / HIC, and SOHIC.

critical factors?

A

a. ammonium bisulfide concentration >2% increase the potential for blistering/HIC and SOHIC

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47
Q

Wet H2S - blistering / HIC, and SOHIC.

_____increase the probability and severity of blistering, HIC, and SOHIC

48
Q

Wet H2S - blistering
appearance
a. Blisters: show on the ID (typically)
b. Internal separations ________to the surface of the steel (for HIC as well - not SOHIC)

49
Q 
Wet H2S - blistering / HIC and SOHIC prevention?
Effective \_\_\_(3)\_\_\_\_ can prevent blistering HIC, and SOHIC.
A

barriers, including alloy cladding and coating,

50
Q

Wet H2S - blistering / HIC

Blistering and HIC can develop _________ stress.

A

with or without

51
Q

Wet H2S - HIC

appearance

A

“step wise cracking”

52
Q

Wet H2S for blistering and HIC

Key Factors: (2)

A

(1) Steel Cleanliness and

(2) Reduction of Discontinuities

53
Q

Wet H2S

- late stage HIC or SOHIC will create surface breaking ____

54
Q

Wet H2S

SOHIC or surface breaking HIC may be seen visually through ___(3 NDE) ___ in early stage

A

WFMT, ECT, ACFM

55
Q

Wet H2S SOHIC-

description is -

A

HIC under stress

56
Q

Wet H2S SOHIC-

appearance?

A

array of HIC stacked on top of each other

57
Q

Wet H2S SOHIC-

is more damaging form of cracking than HIC because of it relatively high rate of developing a ______

A

thru-wall crack

58
Q

Wet H2S SOHIC-

High stress, most commonly in base metal _____to HAZ.

59
Q

Wet H2S SOHIC-

Interconnecting crack is usually _______to surface but may follow high stress.

A

perpendicular

60
Q

Wet H2S SOHIC-SSC

-SOHIC and SSC damage MOST OFTEN associate with _______

61
Q

Wet H2S SOHIC

____can help minimize susceptibility to SOHIC.

62
Q

Wet H2S SOHIC

SOHIC occurs in the _____metal alongside the weld. If found in the weld, they are likely fabrication weld flaws.

63
Q

Wet H2S - SSC definition

A

Sulfide Stress Cracking

64
Q

Wet H2S - SSC

Cracking under the combined action of ______ and corrosion in the presence of ____and _____.

A

tensile stress

water / H2S

65
Q

Wet H2S - SSC

SSC is a form of _____Embrittlement.

66
Q

Wet H2S - SSC

Factors (3)

A

Factors:

(1) Hard Weld Cracking
(2) Weld Chemistry
(3) Weld Procedure Related

67
Q

Wet H2S - SSC

SCC greatest at ____F and generally a concern _<__F-

A

70 / <200F.

68
Q

Wet H2S - SSC
_____is primarily an issue with SCC
-stress is needed to cause SSC

A

hardness

-

69
Q

Wet H2S - SSC

how to minimize?

A

PWHT (and also SOHIC)

70
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

a. due to _____of atomic hydrogen

A

penetration

71
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

Cracking under the combined action of ____ and corrosion in the presence of ____and HF.

A

tensile stress / water

72
Q 
Hydrogen Stress Cracking in Hydrofluoric Acid 
affected materials (2)
A

Carbon Steel and low-alloy steels.

73
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

Susceptibility increases with increasing _____. Steels with levels above (HB ____) are highly susceptible

A

hardness / 237

74
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

a. Primarily_______in carbon steel but may be intergranular in high strength steels.
b. Typically associated with _____.
c. can only be confirmed by _____ examination
d. surface breaking flaws

A

a. trans granular
b. weldments
c. metallographic

75
Q

Hydrogen Stress Cracking in Hydrofluoric Acid
1. Weld procedure qualification, chemistry controls, and PWHT are the methods used to avoid high-hardness HAZs.
a) PWHT
b) Control weld hardness to less than _____HB & localized zones above 237 HB.
(NACE RP0427)
c) Use ASTM A B7M bolts. They are softer and lower strength than B7 bolts.
d) Control of Residual Elements (RE). Controls are same as for HF Acid Corrosion
e) Use carbon steels with Carbon Equivalents (CE) less than 0.43

76
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

_____is not susceptible to this form but may be susceptible to SCC

77
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

Serious corrosion can occur around ______ where dry chloride containing streams mix

A

mix points

78
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

Corrosion can occur where a cool stream forces _____ of the HCl.

79
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

Relate mech?

A

• Blistering, HIC and SOHIC damage in HF acid is similar to that found in wet H2S

80
Q

Hydrogen Stress Cracking in Hydrofluoric Acid

_______ damage in HF acid is similar to that found in wet H2S

A

• Blistering, HIC and SOHIC

81
Q

High-Temperature Hydrogen Attack (HTHA)

At high temperatures atomic H+ diffuses in steel, reacts with carbon to form ________and results in cracking.

A

methane (CH4)

82
Q

High-Temperature Hydrogen Attack (HTHA)

Methane cannot migrate through steel. As methane content increases, internal pressure . _________

83
Q

High-Temperature Hydrogen Attack (HTHA)

increasing resistance ->

A

as welded CS/ non welded CS / CS with PWHT / C-0.5Mo , 2.25 CR (with increasing Cr)

84
Q

High-Temperature Hydrogen Attack (HTHA) -

_________and higher are typically not susceptible in refinery conditions

85
Q

High-Temperature Hydrogen Attack (HTHA)
Higher ______ → higher resistance to HTHA
(stabilizes carbide stability → minimizes methane formation)

86
Q

High-Temperature Hydrogen Attack (HTHA)

• See API ____Nelson curves

87
Q

High-Temperature Hydrogen Attack (HTHA)

HTHA damage is ____and ______. Exposure time is cumulative

A

permanent / irreversible

88
Q

High-Temperature Hydrogen Attack (HTHA)

Not detectable during _______ which may vary from hours to years.

A

“incubation period”,

89
Q

High-Temperature Hydrogen Attack (HTHA)

Use______and ____safety factor when using curves.

A

25-50 F

25 psia to 50 psia hydrogen partial pressure

90
Q 
High-Temperature Hydrogen Attack (HTHA)
crtical factor (3)
A
  • Hydrogen partial pressure
  • temperature
  • metallurgy (more chrome the better)
91
Q

High-Temperature Hydrogen Attack (HTHA)

affected units

A

hydro processing units

92
Q

High-Temperature Hydrogen Attack (HTHA)

found in weld HAZ as well as ____metal away from welds.

93
Q

High-Temperature Hydrogen Attack (HTHA)

______commonly found in weld metal.

94
Q

High-Temperature Hydrogen Attack (HTHA)

internal _______can lead to internal fissuring and cracking.

A

decarburization

95
Q

High-Temperature Hydrogen Attack (HTHA)

non stress relieved carbon steel is more _____that stress relieved and non welded components

A

susceptible

96
Q

High-Temperature Hydrogen Attack (HTHA)

While _____can detect, most equipment has decarburized surface , micro void and fissures may be absent.

97
Q

High-Temperature Hydrogen Attack (HTHA)
C-1/2 Mo curve removed in 1990
added a new lower curve with CS with no PWHT (RP941)

98
Q

High-Temperature Hydrogen Attack (HTHA)

non stress relieve carbon steel is more susceptible that stress relieved and non welded components

99
Q

High-Temperature Hydrogen Attack (HTHA)

Properly metallurgically bonded SS overlay and cladding can prevent HTHA

100
Q

High-Temperature Hydrogen Attack (HTHA)

New equipment should be designed so the base material is inherently resistant to HTHA

101
Q

High-Temperature Hydrogen Attack (HTHA)

Experience shown that removal of metal up to ___” may be needed for finding HTHA.

102
Q

Wet H2s - Blistering

Blistering only results from hydrogen generated by ________, not from hydrogen gas in the process stream.

103
Q

High-Temperature Hydrogen Attack (HTHA)
____ and ______ have been found to be unreliable techniques for HTHA detection and should not be used as primary inspection methods.

A

Ultrasonic attenuation and velocity ratio

104
Q

Wet H2s - SSC
SSC can initiate on the ____of steels in highly localized zones of high hardness in the weld metal
and heat affected zones.

105
Q

Wet H2s
Conditions which are known to promote blistering, HIC, SOHIC and SSC are those containing
free water (in liquid phase) and:
• >50 wppm dissolved H2S in the free water, or
• free water with pH <4 and some dissolved H2S present, or
• free water with pH >7.6 and 20 wppm dissolved hydrogen cyanide (HCN) in the water
and some dissolved H2S present, or
• >0.0003 MPa (0.05 psia) partial pressure of H2S in the gas phase

106
Q

Wet H2s
An arbitrary value of ____wppm H2S in the water phase is often used as the defining concentration
where wet H2S damage becomes a problem.

107
Q

Wet H2s -SOHIC

PWHT can also help to ____susceptibility to SOHIC.

108
Q

Wet H2s -SSC

PWHT is highly ____in preventing or eliminating SSC by reduction of both hardness and residual stress.

109
Q

Wet H2S

Inspection for wet H2S damage generally focuses on _____

A

weld seams and nozzles.

110
Q

Wet H2S
Although cracks may be seen visually, crack detection is best performed with ______
techniques.

A

WFMT, EC, RT or ACFM

111
Q

High Temperature Hydrogen Attack (HTHA)

The loss of _______causes an overall loss in strength

112
Q

High Temperature Hydrogen Attack (HTHA)
Cracking and fissuring are ____and occur adjacent to pearlite (layers of ferrite and iron carbide) areas in carbon steels.

A

intergranular

113
Q

High Temperature Hydrogen Attack (HTHA)

affect units? (3)

A

hydrotreaters (desulfurizers) and hydrocrackers, catalytic reformers

114
Q

High Temperature Hydrogen Attack (HTHA)

what has been removed on the nelson curve?

115
Q

High Temperature Hydrogen Attack (HTHA)

Damage may occur ___in the base metal, weld HAZs, and occasionally in welds.

116
Q

High Temperature Hydrogen Attack (HTHA)

_________ is not a proven method for the detection of damage.

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