Preventative measures to minimize the potential for brittle fracture in existing equipment are limited to controlling _______ and ________, minimizing pressure at ambient temperatures during start-up and shutdown and periodic inspections at high stress locations.
Corrosion under insulation becomes more severe at metal temperatures between ________ and ________, where water is less likely to vaporize and insulation stays wet longer.
Formation of a metallurgical phase known as sigma phase results in a loss of _________ in some stainless steels as a result of high temperature exposure.
Surface initiated cracks caused by environmental cracking of 300 Series SS and some nickel based alloys under the combined action of tensile stress, temperature and an aqueous chloride environmental is called ________. The presence of dissolved oxygen ___________ the propensity for cracking.
Geometry, stress level, number of cycles and _________ are the predominate factors in determining the fatigue resistance of a component.
Atmospheric corrosion is of greatest concern in:
A 6”, A106 Gr B, flanged line carrying caustic wash water at 200º F has signs of atmospheric corrosion. Which of the following may have help accelerate the corrosion?
A form of corrosion that can occur at the junction of dissimilar metals when they are joined together in a suitable electrolyte is __________.
With sulfidation, the presence of oxygen ________ corrosion
MIC is often characterized by _______ within pits in carbon steel.
300 series stainless steel heater tubes in an oil-burning furnace in the hydrocracker began to leak and the furnace was brought down. What was the probable cause of the cracking?
Improved resistance to erosion is usually achieved through increasing substrate ________ using harder alloys, hard facing or face-hardening treatment.
Stainless steels have higher coefficients of thermal expansion than carbon steel or low alloy steel or nickel based alloys and are more likely to see _________.
Oxygen and iron in the wash water injected into reactor effluent can lead to __________ corrosion and fouling.
Hydrogen blisters may form as surface bulges on the ID, the OD on within the wall thickness of a pipe or pressure vessel. Blistering occurs from hydrogen generated by ______, not hydrogen gas from the process stream.
Wet H²S services or _________ acid services are process where hydrogen diffuses into the steel and hydrogen embrittlement (HE) is an issue.
In general, the resistance of iron and nickel based alloys to sulfidation is determined by the ________ content of the material.
Low creep ductility is __________ severe in high tensile strength materials and welds.
Which of the following materials are susceptible to polythionic acid SCC?
Units where graphitization may be suspected are the FCCU and the _____ unit.
Cooling water corrosion can result in many different forms of damage including general corrosion, pitting corrosion, ________, stress corrosion cracking and fouling.
Erosion-corrosion is a description for the damage that occurs when corrosion contributes to erosion by removing protective films or scales, or by exposing the metal surface to further ________ under the combined action of corrosion-erosion.
With cooling water corrosion, _________ oxygen content tends to ________ carbon steel corrosion rates.
If the BHN is 400-500 it may indicate __________.
What structure is 410 stainless steel?
Cracking can occur at low caustic levels if a concentrating mechanism is present. In such cases, caustic concentrations of ________ ppm are sufficient to cause cracking.
Amine stress corrosion cracking is most often associated with lean amine services. The pure alkanolamine does not cause cracking. Cracking in rich amine services are most often associated with _______ problems.
________ of a component is the most important factor in determining a components resistance to mechanical fatigue.
With chloride stress corrosion cracking, __________ temperatures ________ the susceptibility for cracking.
Hydrogen permeation or diffusion rates have been found to be minimal at pH _______ and increase at both higher and lower pH’s.
For carbon steel, common velocity limits are generally limited to _________ fps for rich amine and _______ fps for lean amine.
Hydrogen stress cracking is the same mechanism that is responsible for sulfide stress corrosion cracking in wet H²S environments except that HF acid is generating the __________.
Which of the following materials are subject to mechanical fatigue?
Corrosion under insulation is more severe between ________ and ____________.
Short term overheating is a permanent deformation occurring at relatively _________ stress levels as a result of localized overheating. This usually results in bulging and failure by stress rupture.
Regular and controlled carbon grades of stainless steels such as types 304/304H and 316/316H are particularly susceptible to sensitization in the weld HAZ. Low carbon “L” grades are less susceptible and usually can be welded without sensitizing. The “L” grades will not sensitize provided long term operating temperatures do not exceed about __________.
Which of the following materials is susceptible to CO² corrosion?
Sulfide stress cracking (SSC) is defined as cracking of metal under the combined action of tensile stress and corrosion in the presence of _________ and _________.
Spheroidization and graphitization are competing mechanisms that occur at overlapping temperature ranges. Spheroidization tends to occur preferentially above _______ while graphitization predominates below this temperature.
Cl SCC usually occurs at metal temperatures above ________.
Changing to a more corrosion resistant and/or higher hardness material _________ improve cavitation resistance.
_________ is a selective corrosion mechanism in which one or more constituents of an alloy are preferentially attacked leaving a lower density often porous structure.
Damage from sigma phase appears in the form of ________.
Which of the following alkanolamine systems is the most aggressive in causing amine corrosion?
Nickel based alloys usually contain ________ nickel.
Which of the following can be affected by 885º F Embrittlement?
Vessels constructed after December, 1987 are subject to the requirements of ________ of ASME Section VIII, Division 1.
Naphthenic acid corrosion is a form of high temperature corrosion that occurs primarily in crude and vacuum units and downstream units that process certain fractions that contain naphthenic acid. Which of the following materials is susceptible to naphthenic acid corrosion?
SSC is a form of hydrogen stress cracking resulting from the absorption of ________ that is produced by the sulfide corrosion process on the metal surface.
Atmospheric corrosion:
Which of the following materials is susceptible to sigma phase embrittlement?
________ significantly increases the probability and severity of blistering, HIC and SOHIC damage.
In HF service, carbon steel operating above ________ should be closely monitored for loss in thickness and may need to be upgraded to Alloy 400.
Which of the following materials is susceptible to carburization?
Caustic embrittlement is a form of stress corrosion cracking characterized by surface-initiated cracks that occur in piping and equipment exposed to caustic, primarily adjacent to non-PWHT welds. Which of the following materials is the most resistant to embrittlement?
The best way to prevent failures by atmospheric corrosion is to:
A form of thermal cracking, __________, can occur when high and nonuniform thermal stresses develop over a relatively short period of time in a piece of equipment due to differential expansion and contraction.
Amine units are used in refineries to remove H²S, CO² and _________ from process streams originating in many units including the coker, crude, FCC and hydrogen.
Sulfur and chlorine species in fuel will form sulfur dioxide, sulfur trioxide and hydrogen chloride within the combustion products. At low enough temperatures, these gases and the water vapor in the flue gas will condense to form _________ acid.
Damage due to __________ is not visible and can only be observed by metallographic examination.
_________ is surface initiated cracks caused by environmental cracking of 300 Series SS and some nickel based alloys under the combined action of tensile stress, temperature and an aqueous chloride environment. The presence of dissolved oxygen increases the propensity for cracking.
Metal dusting is preceded by ________ and is characterized by rapid metal wastage.
The accepted way to test for temper embrittlement is ________.
A prime location for erosion is:
Amine cracking has been reported down to ambient temperatures with some amines. __________ temperatures and stress levels _______ the likelihood and severity of cracking.
The loss in strength from spheroidization (Softening) is usually accompanied by a(n) _________ in ductility, which allows for deformation at stress concentrations.
SSC is a form of ________ stress corrosion cracking.
At high temperatures, metal components can slowly and continuously deform under load below the yield strength. This time dependent deformation of stressed components is known as _______?
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