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Terms in this set (21)
What monitoring methods have bee used to detect corrosion?
on-line corrosion monitoring electrical resistance
What is erosion?
It is the mechanical removal of surface material as a result of movement between or impact between solids, liquids, vapors or a combination thereof.;
What is erosion-corrosion?
Occurs when corrosion contributes to erosion by removing protective film or scales or by exposing the metal to further corrosion under the combined action of erosion corrosion.
Which materials are affected by erosion-corrosion?
All metals, alloys and refractories.
What does the metal loss depend on for erosion-corrosion?
Velocity of the fluid
Hardness and size of the impacting medium
Concentration of impacting medium
Hardness and corrosion resistance of subject material
Angle of impact
Which softer alloys are more susceptible to mechanical damage due to erosion-corrosion under high velocity conditions?
Copper and aluminum alloys. (They are easily worn from mechanical damage).
Harness of the metal can be used to minimize erosion-corrosion damage, however why is it not always a good indicator of resistance to erosion?
The resistance to corrosion should also be considered since it may also play a big role on the deterioration of the material.
What are some factors which contribute to an increased corrosivity of the environment?
Why would equipment in the FCC be susceptible to erosion-corrosion?
What causes erosion-corrosion in hydrotreating reactors?
Ammonium Bisulfide Salts, its concentration, velocity and the base metal corrosion resistance.
When exposed to what does crude and vacuum piping may suffer from erosion-corrosion?
But it depends on the temperature , sulfur content, TAN level.
What are some ways design can help mitigate erosion-corrosion?
By changing susceptible geometries.
Decrease the velocity by using larger diameters
Streamlining bends to reduce impingement
Increasing the wall thickness
Improved resistance to erosion is usually achieved through ________________________
Increasing the substrate hardness using harder alloys, hard facing, or surface-hardening treatments.
What has been successful on cyclones and slide valves to prevent erosion-corrosion damage?
Erosion resistance refractories
Is resistance to erosion-corrosion generally increased through increasing substrate hardness?
No, modifying the process environment is more effective.
What are some process environment changes that might mitigate erosion-corrosion?
Reduce corrosivity by deaeration, condensate injection or the addition of inhibitors.
What do heat exchangers utilize to minimize the effects of erosion-corrosion?
Impingement plates and tube ferrules
What metallurgy is used to improve resistance to naphthenic acid corrosion?
Higher molybdenum alloys
What is the morphology of erosion-corrosion?
Localized loss of thickness in the form of pits, grooves, gullies, waves, rounded holes and valleys.
These loses often exhibit a directional pattern.
What inspection techniques can be used to detect erosion-corrosion?
VT of suspected or troublesome areas
UT or RT to check metal loss.
How are IR scans used?
To detect refractory loss on stream
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