Question1: Different organisms thrive on different nutrients including inorganic substances (Sulfur, H²S), and organic substances (Hydrocarbons, Organic acids). In addition, all organisms require a source of carbon, nitrogen and _______ for growth.
Question2: Stainless steel cyclones, piping ductwork and valves in high temperature FCC regeneration service are susceptible areas for _________.
Question3: Geometry, stress level, _________ and material properties are the predominate factors in determining the fatigue resistance of a component.
Question4: Which of these cast irons are not susceptible to graphitic corrosion?
Question5: In general, the resistance of iron and nickel based alloys to sulfidation is determined by the ________ content of the material.
Question6: 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?
Question7: Caustic stress corrosion cracking typically propagates _______ to the weld in adjacent base metal but can occur in the weld deposit or heat affected zone.
Question8: Inspecting for high-cycle fatigue can be difficult since:
Question9: Amine cracking has been reported down to ambient temperatures with some amines. __________ temperatures and stress levels _______ the likelihood and severity of cracking.
Question10: Corrosion under insulation becomes more severe at metal temperatures between ________ and
________, where water is less likely to vaporize and insulation stays wet longer.
Question11: Thermal fatigue cracks usually initiate on the _________ of the component. They are generally wide and filled with oxides due to the elevated temperatures.
Question12: Equipment that is temper embrittled may be susceptible to _______ during start-up and shutdown.
Question13: With high temperature hydrogen attack, ________ using a combination of velocity ratio and backscatter have been the most successful in finding cracking.
Question14: Cracks associated with brittle fracture will typically be _________.
Question15: A prime location for erosion is:
Question16: Ammonium chloride salts are hydroscopic and readily absorb water. A ________ amount of water can lead to very aggressive ammonium chloride corrosion.
Question17: If wet electrodes or high moisture content flux is used, ________ can be charged into the steel resulting in delayed cracking.
Question18: In vessels and piping, creep cracking can occur where high metal temperatures and _________ occur together.
Question19: With sour water corrosion, at a given pressure, the H²S concentration in the sour water _________ as temperatures ________.
Question20: Which of the following materials is susceptible to CO² corrosion?
Question21: What structure is 409 stainless steel?
Question22: In design and fabrication, it is advisable to avoid sharp changes in cross section, such as short radius fillets or undercut that can give rise to _________.
Long-seam welds are particularly susceptible to reheat cracking due to mismatch caused by fit up problems.
Question23: Which of the following can be affected by 885º F Embrittlement?
Question24: Although the loss of toughness from temper embrittlement is not evident at operating temperatures, equipment that is temper embrittled may be susceptible to ________ during start-up and shutdown.
Question25: With creep, increased stress due to loss in thickness from corrosion will ________ time to failure.
Question26: 300 Series SS is susceptible to LME when it comes in contact with molten ________.
Question27: 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.
Question28: Damage due to __________ is not visible and can only be observed by metallographic examination.
Question29: To prevent hydrogen embrittlement, use lower strength steels and _________ to temper the microstructure, improve ductility and reduce residual stresses.
Question30: 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 __________.
Question31: MIC is often found in _________, bottom water of storage tanks, piping with stagnant or low flow and piping in contact with some soils.
Question32: Which of the following is not a critical factor that contributes to a brittle fracture?
Question33: Most brittle failures appear as:
Question34: Thermal fatigue cracks usually:
Question35: Caustic embrittlement cracking can be effectively prevented by means of PWHT at a temperature of
_______.
Question36: __________ is a form of damage found mostly in older vintage carbon steels and C-0.5 Mo low alloy steels under the combined effects of deformation and aging at an intermediate temperature.
Question37: Weld heat affected zone graphitization is most frequently found in the heat affected zone adjacent to welds in a narrow band, corresponding to the low temperature edge of the heat affected zone. In multi-pass welded butt joints, these zones overlap each other covering the entire cross section. Because of its appearance, this type of graphitization is called________.
Question38: PWHT is ___________ in preventing caustic SCC.
Question39: Characteristic stress corrosion cracks have many branches and may be visually detectable by a
__________ appearance on the surface.
Question40: Sulfidation is primarily caused by:
Question41: A steam actuated soot blower has condensate in the first steam exiting the soot blower. What type of damage can be expected to be found when the furnace is brought down for maintenance and inspection?
Question42: Stress levels and __________ are the critical factors causing carbonate stress corrosion cracking.
Question43: Start-up and shutdown of equipment increase the susceptibility of thermal fatigue. There is no set limit on temperature swings; however, as a practical rule, cracking may be suspected if the temperature swing exceeds about _________.
Question44: High strength steels are susceptible to LME when they come in contact with molten ________.
Question45: The dewpoint of hydrochloric acid depends on the concentration of hydrogen chloride. It is typically about
_________.
Question46: Titanium should not be used in known hydriding services such as _____ or ______.
Question47: Which of the following is not a primary factor contributing to erosion-corrosion?
Question48: A fatigue fracture is brittle and the cracks are most often __________.
Question49: Which of the following materials are the least susceptible to caustic embrittlement?
Question50: Mechanical fatigue can cause cracks that initiate from the surface and often form a:
Question51: Graphitization can be prevented by using chromium containing low alloys steels for long-term exposure above ________.
Question52: Which of these materials are susceptible to brittle fracture?
Question53: The loss in strength from spheroidization (Softening) is usually accompanied by a(n) _________ in ductility, which allows for deformation at stress concentrations.
Question54: The most common method used for monitoring underground structures is measuring the structure to soil
______ using dedicated reference electrodes near the structure.
Question55: The sudden rapid fracture under stress (residual or applied) where the material exhibits little or no evidence of ductility or plastic deformation is called _________.
Question56: Convert these temperatures - 156º C and 450º F
Question57: Which of the following is not a method used to prevent brittle fracture?
Question58: Titanium Hydriding damage occurs primarily in sour water strippers and amine units in the overhead condensers, heat exchanger tubes and other titanium equipment operating above _________.
Question59: With chloride stress corrosion cracking, __________ temperatures ________ the susceptibility for cracking.
Question60: Resistance to sulfidation increases as the:
Question61: Protection in a boiler from boiler feed water corrosion is accomplished by:
Question62: When caustic stress corrosion cracking is a concern, steam out of _________ carbon steel piping and equipment should be avoided.
Question63: Atmospheric corrosion:
Question64: For galvanic corrosion to take place, three conditions must be met, presence of an electrolyte, two different materials or alloys and ___________.
Question65: Which if the following materials are not susceptible to hydrogen stress cracking?
Question66: ASME Section VIII had few limitations concerning brittle fracture prior to:
Question67: What is the chemical symbol for propane or propylene?
Question68: Steel hardness, __________ and stress are critical factors in causing hydrogen stress cracking.
Question69: For carbon steel, common velocity limits are generally limited to _________ fps for rich amine and
_______ fps for lean amine.
Question70: ____________ is often found in piping and equipment that handles caustic, including H²S and mercaptan removal units, as well as equipment that uses caustic for neutralization in sulfuric acid and HF acid units.
Question71: High temperature H² / H²S corrosion damage is minimized by using alloys with high _________ content.
Question72: Which of the following materials is affected by high temperature corrosion?
Question73: With sour water corrosion, streams with a pH below ________ indicate the presence of a strong acid.
Question74: Which of the following materials is not susceptible to Cl SCC?
Question75: Ammonium chloride salts may be whitish, greenish or _________.
Question76: Carbonate cracking typically propagates _________ to the weld; the pattern of cracking observed on the surface is sometimes described as ________.
Question77: Susceptibility of an alloy to sulfidation is determined by its ability to form protective _________.
Question78: ________ significantly increases the probability and severity of blistering, HIC and SOHIC damage.
Question79: In HF service, carbon steel forms a protective _________ scale in dry concentrated acid. Loss of the protective scale through high velocities or turbulence will result in greatly accelerated corrosion rates.
Question80: The amplitude and frequency of vibration as well as the _________ of the components are critical factors in vibration-induced fatigue.
Question81: ___________ cooling water outlet temperatures and/or process side outlet temperatures tend to
__________ corrosion rates as well as fouling tendency.
Question82: The severity of hydrochloric acid corrosion ________ with _________ HCl concentration and increasing temperatures.
Question83: Which of these materials exhibit an endurance limit below which fatigue cracking will not occur?
Question84: What structure is 410 stainless steel?
Question85: If weld repairs are required, the effects of temper embrittlement can be temporarily reversed (de- embrittled) by heating at ______ for 2 hours per inch of thickness and rapidly cooling to room temperature.
Question86: 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.
Question87: With high temperature sulfide corrosion (Sulfidation), noticeable increases may be found downstream of
_________ injection points.
Question88: ________ is a form of carbon that may promote carburization, particularly during decoke cycles where temperatures exceed the normal operating temperatures.
Question89: A quick test for embrittlement from _________ is a bend test or crush test. Unaffected material will be crushed in a ductile fashion while embrittled components will crack with no signs of ductility.
Question90: Temper embrittlement can be identified by a(n) shift in the ductile-to-brittle transition temperature measured in a Charpy impact test.
Question91: Units where graphitization may be suspected are the FCCU and the _____ unit.
Question92: Amine cracking is ________ likely to occur in lean MEA and DEA services than in MDEA and DIPA services.
Question93: 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?
Question94: Corrosion from oxygen tends to be __________ type damage and can show up anywhere even if only very small amounts break through the scavenging system.
Question95: In HF service, carbon steel operating above ________ should be closely monitored for loss in thickness and may need to be upgraded to Alloy 400.
Question96: Corrosion rates of the anode will be less affected if there is a _________ anode to cathode ratio.
Question97: 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.
Question98: Which of the following materials are subject to mechanical fatigue?
Question99: 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.
Question100: Wet H²S services or _________ acid services are process where hydrogen diffuses into the steel and hydrogen embrittlement (HE) is an issue.
Question101: Creep damage is found in high temperature equipment operating above the ________. Fired heater tubes and components, Catalytic reactors, FCC reactors and FCC fractionator and regenerator internals all operate in or near this.
Question102: Corrosion by HF (Hydrofluoric) acid can result in high rates of general or localized corrosion and may be accompanied by hydrogen cracking, blistering and ________.
Question103: Cooling water corrosion and __________ are closely related and should be considered together.
Question104: Thermal fatigue is caused by:
Question105: __________ caustic concentrations and ________ temperatures increase the likelihood and severity of cracking with caustic embrittlement.
Question106: ________ has been a major problem on coke drum shells.
Question107: 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.
Question108: Damage from sigma phase appears in the form of ________.
Question109: __________ are the most common type of equipment susceptible to carburization in the refining industry.
Question110: Time to failure by thermal fatigue is primarily affected by:
Question111: In general, the resistance of carbon steel and other alloys to High temperature corrosion is determined by the ________ content of the material.
Question112: Fatigue cracks usually initiate on the surface at notches or __________ under cyclic loading.
Question113: 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.
Question114: Carbon steel is susceptible to SCC when used in ___________ service.
Question115: Exposure to high solution strength caustic can result in general corrosion or high corrosion rates above
________.
Question116: Key factors affecting thermal fatigue are the magnitude of the temperature and the __________.
Question117: What treatment is used to prevent boiler feed water corrosion?
Question118: Which of the following does not increases the likelihood of atmospheric corrosion?
Question119: Carbonate SCC can occur at relatively low levels of ________ but usually occurs at welds that have not been stressed relieved.
Question120: Stress relief and stabilization heat treatment of 300 Series SS for maximizing chloride SCC and PASCC resistance can cause ____________ problems, especially in thicker sections.
Question121: _________ is a mechanical form of degradation that occurs when a component is exposed to cyclical stresses for an extended period, often resulting in sudden, unexpected failure.
Question122: Since all fuels contain some amount of sulfur, sulfuric and sulfurous acid __________ can occur if the metal temperature is below this temperature.
Question123: In order for PASCC to occur the material must be ______.
Question124: The more noble material, called the ________, is protected by sacrificial corrosion of the more active material, called the ________. The more active metal corrodes at a higher rate than it would if it were not connected to the more noble metal.
Question125: Temper embrittlement is a metallurgical change that is not readily apparent and can be confirmed through
________.
Question126: At elevated temperature, the carbide phases in certain carbon steels are unstable and may decompose into _______. This decomposition is known as graphitization.
Question127: ______ is similar to HIC but is a potentially more damaging form of cracking which appears as arrays of cracks stacked on top of each other. The result is a through thickness crack that is perpendicular to the surface and is driven by high levels of stress.
Question128: Thermal fatigue damage is in the form of cracking that may occur anywhere in a metallic component where relative movement is constrained, particularly under repeated __________.
Question129: Once cracking from LME has occurred, grinding out the affected area ______ an acceptable fix.
Question130: Vessels constructed after December, 1987 are subject to the requirements of ________ of ASME Section VIII, Division 1.
Question131: ____________ are characterized by a localized loss in thickness in the form of pits, grooves, gullies, waves, rounded holes and valleys. These losses often exhibit a directional pattern.
Question132: The accepted way to test for temper embrittlement is ________.
Question133: The creep threshold temperature for carbon steel is ________.
Question134: HCL acid corrosion is found in several units, especially _______ and ________, units, hydroprocessing units and catalytic reformer units.
Question135: For pressure vessels, inspection should focus on welds of ________ operating in the creep range.
Question136: The endurance limit is usually about:
Question137: Corrosion from oxygen in boiler feed water usually creates:
Question138: Which of the following are affected by sulfidation?
Question139: The creep threshold temperature for 1 ¼, 2 ¼, 5 and 9 Cr is ________.
Question140: With very few exceptions, cooling water should always be on the ________ side to minimize stagnant areas.
Question141: Naphthenic acid corrosion is most severe in _________ flow; in areas of high velocity or turbulence and in distillation towers where hot vapors condense to form liquid phase droplets.
Question142: Creep and stress rupture is more likely in a _________ grained material than a _______ grained material.
Question143: Inspection for wet H2S damage generally focuses on _____ and ______.
Question144: Annealed steels are more resistant to Spheroidization than normalized steels. _________ grained steels are more resistant than ______ grained steels.
Question145: At elevated temperatures, dissimilar weld metal cracking is aggravated by the diffusion of carbon out of the weld metal and into the base metal. The temperature at which carbon diffusion becomes a concern is above ________.
Question146: Corrosion in boiler feedwater and condensate return systems is usually the result of dissolved gases, oxygen and ________.
Question147: The presence of _________ can destabilize the scale and turn it into a nonprotective scale.
Question148: Sulfidation is also known as ____________.
Question149: Where is PASCC normally located?
Question150: A form of fatigue cracking in which cracks develop under the combined effects of cyclic loading and corrosion is called _______. Cracking often initiates at stress concentrations such as a pit in the surface.
Question151: When connected to a more anodic material, titanium may suffer severe __________.
Question152: With sulfuric acid corrosion, mix points with _______ cause heat to be released and high corrosion rates can occur where the acid becomes diluted.
Question153: Heat treatment can have a significant effect on the toughness and hence fatigue resistance of a metal. In general, ________ grained microstructures tend to perform better than _________ grained.
Question154: _________ is a change in the microstructure of certain carbon steels and 0.5Mo steels after long-term operation in the 800º F to 1100º F range that may cause a loss in strength, ductility and/or creep resistance.
Question155: Thermal fatigue cracks propagate ________ to the stress and are usually dagger shaped, transgranular and oxide-filled.
Question156: Metal dusting is preceded by ________ and is characterized by rapid metal wastage.
Question157: For furnaces, to prevent PASCC, keep the firebox heated above the dewpoint to keep ________ from forming.
Question158: SSC is a form of hydrogen stress cracking resulting from the absorption of atomic hydrogen that is produced by the ______ corrosion process on the metal surface.
Question159: _________ is most likely found in hard weld and heat-affected zones and in high strength components.
Question160: 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.
Question161: Sigma phase occurs in Ferritic, martensitic, austenitic and duplex stainless steels when exposed to temperatures in the range of _____.
Question162: The "L" grade of stainless steels will sensitize if exposed more than several hours above _______ or long term above _____.
Question163: Corrosion of the anode may be significantly higher ________ to the connection to the cathode, depending on solution conductivity.
Question164: In piping and equipment, creep cracking can occur where high metal temperatures and _________ occur together. Creep cracking, once initiated, can progress rapidly.
Question165: SOHIC is driven by localized stresses so that __________ is somewhat effective in preventing SOHIC damage.
Question166: For a specific material, HTHA is dependent on temperature, hydrogen partial pressure, time and
_________.
Question167: With cooling water corrosion, _________ oxygen content tends to ________ carbon steel corrosion rates.
Question168: In order to minimize and prevent amine SCC, PWHT all carbon steel welds in accordance with API RP
_____.
Question169: Cavitation is best prevented by avoiding conditions that allow the absolute pressure to fall below the
___________ of the liquid or by changing the material properties.
Question170: Low alloy steels contain a maximum of _______ chrome.
Question171: In most cases, brittle fracture occurs only at temperatures below the Charpy impact transition temperature.
Steel cleanliness and ________ have a significant influence on toughness and resistance to brittle fracture.
Question172: With hydrofluoric acid corrosion, corrosion rates increase with _______ temperatures and ______ HF concentrations.
Question173: The effects of hydrogen embrittlement ___________ with _________ temperatures.
Question174: Liquid metal embrittlement can occur if 300 Series SS comes in contact with molten _______.
Question175: Carburization can be confirmed by substantial increases in _______ and loss of __________.
Question176: Carbon dioxide (CO²) corrosion results when CO² dissolves in water to form ________.
Question177: Sulfidation is primarily caused by ________ and other reactive sulfur species as a result of the thermal decomposition of sulfur compounds at high temperatures.
Question178: General or localized corrosion of carbon steels and other metals caused by dissolved salts, gases, organic compounds or microbiological activities is called ________.
Question179: With short term overheating, time to failure will ___________ as internal pressures or loading decrease.
Question180: What is the chemical symbol for ethane or ethylene?
Question181: A form of corrosion caused by living organisms such as bacteria, algae or fungi is _______ .
Question182: All piping and equipment exposed to HF acid at any concentration with hardness levels above the recommended limit (237 BHN) are subject to _________.
Question183: 300 Series SS, 400 Series SS and duplex SS are subject to pitting and localized corrosion under insulation. In addition, __________ are also subject to SCC if chlorides are present, while _________ are less susceptible.
Question184: The best way to prevent 885º F embrittlement is to use low ________ alloys, or to avoid exposing the susceptible material to the embrittling range.
Question185: Amine cracking is a form of ________ stress corrosion cracking.
Question186: With Cl SCC, ________ levels of chloride ________ the likelihood of cracking.
Question187: Mitigation of CUI is best achieved by _________.
Question188: __________ is a change in the microstructure of certain carbon steels and 0.5 Mo steels after long term operation in the 800º F to 1100º F range.
Question189: _________ corrosion rates are found in a gas oil desulfurizers and hydrocrackers than naphtha desulfurizers and hydrocrackers by a factor of almost "2".
Question190: __________ is usually found in aqueous environments or services where water is sometimes or always present, especially where stagnant or low-flow conditions allow the growth of microorganisms.
Question191: Which of the following is not a major factor associated with corrosion by sulfidation?
Question192: 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 __________.
Question193: Naphthenic acid is _____ by catalytic reactions in downstream hydro processing and FCC units.
Question194: Many thermal fatigue cracks are filled with:
Question195: Dissimilar weld metal cracking occurs because the coefficients of thermal expansion between ferritic steels and 300 Series stainless steels differ by ________ or more.
Question196: What test is used to determine a material's toughness?
Question197: At a given pressure, the H²S concentration in the sour water _________ as temperature _________.
Question198: Increasing the chromium in steels offers no major improvement in resistance to CO² corrosion until a minimum of __________ is reached.
Question199: In most cases, brittle fracture occurs only at temperatures _________ the Charpy impact transition temperature.
Question200: All piping and equipment exposed to HF acid at any concentration with hardness levels above ________ are subject to hydrogen stress cracking.
Question201: ________ of a component is the most important factor in determining a components resistance to mechanical fatigue.
Question202: ________ and _______ damage develop without applied or residual stress so that PWHT will not prevent them from occurring.
Question203: With ammonia stress corrosion cracking weld hardness should not exceed _______ BHN.
Question204: Type 304L SS is satisfactory for phosphoric acid concentration of 100% up to about _________. Type 321 is required from there to 225º F.
Question205: 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.
Question206: The regenerator reboiler and the regenerator are areas where the temperature and __________ of the amine stream are the highest and can cause significant corrosion problems.
Question207: Sour water corrosion in _________ containing environments may be accompanied by carbonate SCC.
Question208: What structure is 304 stainless steel?
Question209: ________ eliminates the susceptibility of most common steels to SCC.
Question210: Temper embrittlement _________ be prevented if the material contains critical levels of the embrittling impurity elements and is exposed in the embrittling range.
Question211: Which of the methods are effective for finding thermal fatigue cracks?
Question212: If wet electrodes or high moisture content flux weld electrodes are used to weld carbon steel, hydrogen can be charged into the steel resulting in _________.
Question213: Cracking of dissimilar weld metals occurs in the __________ side of a weld joining 300 Series SS and carbon steel.
Question214: ____________ is the reduction in toughness due to a metallurgical change that can occur in some low alloy steels as a result of long-term exposure in the temperature range of about 650º F to 1100º F.
Question215: Stresses acting on the weldments are significantly ________ when austenitic stainless steel filler metal is used. A nickel based filler metal has a coefficient of thermal expansion closer to carbon steel resulting in significantly lower stress at elevated temperatures.
Question216: 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.
Question217: Which of the following materials are susceptible to nitriding?
Question218: Conditions favoring carburization include a high gas phase carbon activity and _______ oxygen potential.
Question219: Which of these materials are not susceptible to Spheroidization?
Question220: Which of the following materials is susceptible to sigma phase embrittlement?
Question221: Vibration-induced fatigue can be eliminated or reduced through _________ and the use of supports and vibration dampening equipment. Material upgrades are not usually a solution.
Question222: Cracks connecting hydrogen blisters are referred to as ________.
Question223: Hardness is primarily an issue with SSC. Typical low strength carbon steels should be controlled to produce weld hardness less than ________.
Question224: With CUI, corrosion rates __________ with increasing metal temperatures up to the point where the water evaporates quickly.
Question225: Hydrogen blisters may form at many different depths from the surface of the steel, in the middle of the plate or near a weld. In some cases, neighboring or adjacent blisters that are at slightly different depths (planes) may develop cracks that link them together. Interconnecting cracks between the blisters often have a __________ appearance.
Question226: Corrosion rates of the anode can be high if there is a _______ anode to cathode ratio.
Question227: The primary factors affecting high temperature oxidation are metal temperature and _______.
Question228: With decarburization, the decarburized layer will be free of carbide phases. Carbon steel will be ______.
Question229: 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.
Question230: Nitriding is usually confined to the surface of most components and will have a dull, ______ appearance. In more advanced stages, the material will exhibit very hard surface hardness.
Question231: Dissimilar weld metal cracking can be aggravated by _______.
Question232: Hardness levels above ________ are highly susceptible to hydrogen stress cracking (HF). Time-to-failure decreases as the hardness increases.
Question233: Thermal fatigue becomes of concern if the temperature swings exceed:
Question234: Susceptibility to temper embrittlement is largely determined by the presence of the alloying elements manganese and _______.
Question235: Which of the following are susceptible to thermal fatigue?
Question236: ______ is most likely found in hard welds and heat affected zones and in high strength components.
Question237: __________ is a form of cracking that results when certain molten metals come in contact with specific alloys. Cracking can be very sudden and brittle in nature.
Question238: ________ usually occurs when a colder liquid contacts a warmer metal surface.
Question239: Geometry, stress level, number of cycles and _________ are the predominate factors in determining the fatigue resistance of a component.
Question240: SCC tendency ________ towards the alkaline pH region
Question241: Steam blanketing is when the heat flow balance is disturbed; individual bubbles join to form a steam blanket, a condition known as Departure from Nucleate Boiling (DNB). Once a steam blanket forms, tube rupture can occur rapidly, as a result of _________.
Question242: Foul smelling water may be a sign of fouling and/or _______
Question243: It is generally accepted that stresses approaching _________ are required for SCC to occur so that thermal stress relief is effective in preventing caustic SCC.
Question244: Susceptibility to hydrogen stress cracking __________ with __________ hardness.
Question245: The best method to inspect for SCC is ____.
Question246: Ferritic stainless steels are usually not used in __________ applications.
Question247: Which of the following materials are generally not suitable for HF service?
Question248: Cavitation is a form of erosion caused by the formation and instantaneous collapse of innumerable tiny vapor bubbles. Temperatures approaching the boiling point of the liquid are _________ to result in bubble formation.
Question249: Which of these materials is not susceptible to amine cracking?
Question250: Galvanized steel components should not be welded to ________ due to LME.
Question251: Lean amine is generally not corrosive because they have either low conductivity and/or high pH. Corrosion rates increase with increasing temperatures, particularly in rich amine service. Temperatures above
_________ can result in acid gas flashing and severe localized corrosion.
Question252: A carbon steel bundle from the overhead condenser in the crude unit operates at 300º F and is in hydrochloric acid service. It showed severe pitting type corrosion when pulled for inspection. What type of material would be best suited for this service?
Question253: Alloys with increased amounts of _______ show improved resistance to naphthenic acid corrosion.
Question254: Spheroidization and graphitization are competing mechanisms that occur at overlapping temperature ranges. Spheroidization tends to occur preferentially above _______ while graphitization predominates below this temperature.
Question255: ___________ is the result of cyclic stresses caused by variations in temperature.
Question256: _________ is accelerated high temperature wastage of materials that occurs when contaminants in the fuel form deposits and melt on the metal surfaces.
Question257: Dew point corrosion can occur if the metal temperature is below the dew point. The dew point of sulfuric acid is __________.
Question258: A condition where steel loses strength due to the removal of carbon and carbides leaving only an iron matrix is called decarburization. This occurs during high temperatures, during PWHT and from exposure to fires. Which of the following materials is not affected by this?
Question259: Cracking of dissimilar weld metals occurs on the _________ side of a weld between an austenitic and a Ferritic material operating at high temperatures.
Question260: The extent and depth of decarburization is a function of temperature and ______.
Question261: Soil corrosion of carbon steel can be minimized through the use of special backfill, coatings and _______.
Question262: Hydrogen permeation or diffusion rates have been found to be minimal at pH _______ and increase at both higher and lower pH's.
Question263: ____________ is a form of environmental cracking that can initiate on the surface of high strength low alloy steels and carbon steels with highly localized zones of high hardness in the weld metal and HAZ as a result of exposure to aqueous HF acid service.
Question264: Changing to a more corrosion resistant and/or higher hardness material _________ improve cavitation resistance.
Question265: 300 Series SS, 5Cr, 9Cr and 12Cr alloys are not susceptible to ________ at conditions normally seen in refineries.
Question266: Which of the following metals is the most anodic?
Question267: Temperature, ________ and stress are critical factors of stress rupture. This is usually found in furnaces with coking tendencies and fired heater tubes.
Question268: SCC usually occurs at pH values above two (2). SCC tendency __________ toward the alkaline pH region
Question269: With steam blanketing, failure occurs as a result of _________ in the tube from the internal steam pressure at the elevated temperature.
Question270: The level of creep damage is a function of the material and the coincident _________ level at which the creep deformation occurs.
Question271: Most brittle failures occur: