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 _______

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.

Module 9 (General Erosion) Flashcards by Wynne liu

Erosion / Erosion Corrosion

affect metals? / mostly?

all metals, but mostly CS and cooper alloys

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Erosion / Erosion Corrosion

critical factor? (4)

velocity
impacting particles
hardness
angle of impact

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Erosion / Erosion Corrosion

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

Cu / Al

2. severe

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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

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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.

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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

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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

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Dissimilar weld metal cracking

most common affected material? ___material welded to _____

ferritic material weld to austenitic SS

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Dissimilar weld metal cracking

why does cracking occur?

high differential thermal expansion stress if having different thermal coefficients

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Dissimilar weld metal cracking

thermal expansion differ ____ to ____% = cracking

25-30%

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Dissimilar weld metal cracking

thermal expansion > ____F can occur

500

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Dissimilar weld metal cracking

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

Ni / lower stress

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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

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Dissimilar weld metal cracking ***

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

at the toe
HAZ
ferritic

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Dissimilar weld metal cracking

what based filler is best?

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Dissimilar weld metal cracking

inspection? Location/ method

near the ID
/
PT WFMT or angle beam

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Thermal shock

occurs when?

colder liquid contact a much warmer metal surface

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Thermal shock

affectsed material

all metals

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Thermal shock
critical factor (2)

magnitude of temp differential
and
2.coefficient

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Thermal shock

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

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Thermal shock

loss of what properties is more susceptible to thermal shock?

Cr-Mo (due to temper embrittle ment)

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Thermal shock

preventition

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

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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

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