Module 9 (General Erosion) Flashcards
Erosion / Erosion Corrosion
affect metals? / mostly?
all metals, but mostly CS and cooper alloys
Erosion / Erosion Corrosion
critical factor? (4)
- velocity
- impacting particles
- hardness
- angle of impact
Erosion / Erosion Corrosion
softer alloys such as ____(2) __may subject to _____metal loss under high velocity
- Cu / Al
2. severe
Erosion / Erosion Corrosion
increasing the hardness of eroding metal component can ________rate of erosion damage. However _____ be effective where corrosion plays a signification role
increase / MAY NOT
Erosion / Erosion Corrosion
affected equipment? (4)
- __________piping may be subject to erosion-corrosion by ammonium bisulfide
- _________ piping and vessels exposed to naphthenic acids in some crude oils
- Erosion-corrosion is common in________
- Erosion by water droplets in steam systems can be very _______
- Hydroprocessing reactor effluent piping may be subject to erosion-corrosion by ammonium bisulfide
- Crude and vacuum unit piping and vessels exposed to naphthenic acids in some crude oils
- Erosion-corrosion is common in acid alkylation systems
- Erosion by water droplets in steam systems can be very damaging.
Erosion / Erosion Corrosion
appearance? (2)
- localized loss in thickness in the form of grooves, gullies, waves, rounded holes, valleys,
- These losses often exhibit a directional pattern
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. shape, geometry, and materials
B. resistance
c. corrosion-resistant alloys and/or altering the process environment
d. impingement plates
Dissimilar weld metal cracking
most common affected material? ___material welded to _____
ferritic material weld to austenitic SS
Dissimilar weld metal cracking
why does cracking occur?
high differential thermal expansion stress if having different thermal coefficients
Dissimilar weld metal cracking
thermal expansion differ ____ to ____% = cracking
25-30%
Dissimilar weld metal cracking
thermal expansion > ____F can occur
500
Dissimilar weld metal cracking
what material has a coefficient close to CS? resulting in ____
Ni / lower stress
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
- narrow region
- fusion
- ferritic
Dissimilar weld metal cracking ***
crack form ______ of the weld in the ____ of the ____material
- at the toe
- HAZ
- ferritic
Dissimilar weld metal cracking
what based filler is best?
Ni
Dissimilar weld metal cracking
inspection? Location/ method
near the ID
/
PT WFMT or angle beam
Thermal shock
occurs when?
colder liquid contact a much warmer metal surface
Thermal shock
affectsed material
all metals
Thermal shock critical factor (2)
- magnitude of temp differential
and
2.coefficient
Thermal shock
What metal has higher coefficient than carbon and alloy steel or nickel based alloys and more likely to see high stress?
SS
Thermal shock
loss of what properties is more susceptible to thermal shock?
Cr-Mo (due to temper embrittle ment)
Thermal shock
preventition
minimize situation where rain or fire water deluge can contact hot equipment
Thermal shock
related mech? (2)
- thermal fatigue
2. short term overheating
Cavitation
affected equipment? (2)
- piping down stream of orifices’ or CV
2. temp approaching boiling point
Cavitation
____accelerated the caviation?
corrosion (cavitation corrosion)
Cavitation
appearance? (2)
share edge pitting
but may also be a gouge appearance
Cavitation
prevention?
avoid condition that allow absolute pressure to fall below the vapor pressure
Cavitation
inspection? (4)
VT/UT/RT
Acoustic
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. Refractory design, selection, and installation
b. Dryout schedules, cure times, and application procedures
f) thermal coefficient
g) oxidation
h) sulfurous acid
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_______
PWHT / in service at elevated temp
Stress Relaxation cracking (Reheat cracking) NL affect material (3)
a. Cr-Mo especially 2 - 1/4 - 1mo with vanadium added
b. low Cr
Stress Relaxation cracking *** NL
what is very susceptible
HSLA
Stress Relaxation cracking (Reheat cracking) NL
critical factor?(6)
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.
Stress Relaxation cracking (Reheat cracking) NL
affected equipment
high stress area (thickner)
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.
large grain
Gaseous O2 enhanced ignition and combustion (NL)
what o2 % needed ?
> 25%
Gaseous O2 enhanced ignition and combustion (NL)
affected material and pressure (2)? and what is fire resistance? (2)
CS - 15PSIG
SS- 200PSG
Cu-Ni are fire resistance
Gaseous O2 enhanced ignition and combustion (NL)
what material is avoided? (2)
Ti and Al
Gaseous O2 enhanced ignition and combustion (NL)
prevention (2)
d) Minimize lubricants and use only “oxygen-compatible” lubricants
g) Minimize sudden changes in pressure in the system.
Gaseous O2 enhanced ignition and combustion (NL)
inspection?
Most commercial oxygen is dry and non-corrosive at normal ambient temperatures. this type of damage CANNOT be inspected for in advance
Dealloying NL
description
SELECTIVE corrosion mechanism in which one or more constituents of an alloy are preferentially attacked, leaving a lower-density (dealloyed)
Dealloying NL
appearance
porous structure.
Dealloying NL
affected material
Cu-alloys as well as alloy 400
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. dealloying
Graphite corrosion of Cast Iron
description
Attack results in a porous structure with a loss of ____(3)_____It usually occurs under (2)
strength, ductility, and density
low- pH and stagnant conditions,
Graphite corrosion of Cast Iron
affect material and not affected?
a. Primarily gray cast iron,
b. White iron is not subject to this damage because there is no free graphite.
Graphite corrosion of Cast Iron critical factor (5)
exposure conditions, including temperature, degree of aeration, pH, and exposure time.
Graphite corrosion of Cast Iron
occurs in the presence of _____ and below ___F
moisture or an aqueous phase,
below 200 °F (95 c) c.
Graphite corrosion of Cast Iron
Damage _____with ____ temperature and aeration, and reduced pH
increase / increase
Graphite corrosion of Cast Iron
occur during ___condition when high concentrations of sulfates are present.
stagnant
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
VT
soft and easily cut or gouged
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
VT
soft and easily cut or gouged
Dealloying NL
Dealloying in brasses is visually evident by a _____ copper color instead of the yellow brass color.
reddish,
Higher ______containing alloys are used for improved resistance to naphthenic acid corrosion
molybdenum
Refractory
(NDE) ___ are used to detect refractory loss on stream.
IR scans
