API API-571 Corrosion and Materials Professional Online Training

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1. _________ is the main concern during start-up, shutdown and/or hydro testing for equipment/piping operating at elevated temperatures. This event can also occur in an auto refrigeration event in units processing light hydrocarbons.

2. Fatigue will not occur in carbon steel if stresses are below the:

3. ________ has been a major problem on coke drum shells.

4. The “L” grade of stainless steels will sensitize if exposed more than several hours above _______ or long term above _____.

5. Once cracking from LME has occurred, grinding out the affected area ______ an acceptable fix.

6. Ferritic stainless steels are usually not used in __________ applications.

7. In general, the resistance of carbon steel and other alloys to High temperature corrosion is determined by the ________ content of the material.

8. Conditions favoring carburization include a high gas phase carbon activity and _______ oxygen potential.

9. It is generally accepted that stresses approaching _________ are required for SCC to occur so that thermal stress relief is effective in preventing caustic SCC.

10. Low creep ductility is __________ severe in high tensile strength materials and welds.

11. Many thermal fatigue cracks are filled with:

12. 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 _________.

13. 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.

14. ____________ 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.

15. SOHIC is driven by localized stresses so that __________ is somewhat effective in preventing SOHIC damage.

16. Which of these materials are not susceptible to Spheroidization?

17. A form of corrosion that can occur at the junction of dissimilar metals when they are joined together in a suitable electrolyte is __________.

18. Proper application of ________ will control but not eliminate microbes that cause MIC so that continued treatment is necessary.

19. At elevated temperature, the carbide phases in certain carbon steels are unstable and may decompose into _______. This decomposition is known as graphitization.

20. Which of these materials are susceptible to brittle fracture?

21. Soils having high moisture content, high dissolved salt concentrations and high ________ are the most corrosive.

22. Susceptibility to temper embrittlement is largely determined by the presence of the alloying elements manganese and _______.

23. 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.

24. Sulfidation of iron-based alloys usually begins at metal temperatures above _____.

25. The rate of creep deformation is a function of the material, load and temperature. The rate of damage is sensitive to both load and temperature. Generally, an increase of about _______ or an increase of ________ on stress can cut the remaining life in half.

26. Which of the methods are effective for finding thermal fatigue cracks?

27. The best way to prevent 885º F embrittlement is to use low ________ alloys, or to avoid exposing the susceptible material to the embrittling range.

28. 300 Series SS can be used for sour water service at temperatures below ____________, where Chloride SCC is not likely.

29. Sigma phase in welds can be minimized by controlling ferrite in the range of _________ for Type 347 SS.

30. Naphthenic acid is _____ by catalytic reactions in downstream hydro processing and FCC units.

31. 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?

32. A 5Cr-1Mo piping system in the hydrogen unit shows significant internal wall loss after 2 years in service due to CO² corrosion.

Which material would be best suited to use to install a new pipe system?

33. In order to minimize and prevent amine SCC, PWHT all carbon steel welds in accordance with API RP _____.

34. _________ 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.

35. 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.

36. Sulfidation is also known as ____________.

37. For some materials such as titanium, carbon steel and low alloy steel, the number of cycles to fatigue fracture decreases with ________ until an endurance limit is reached. Below this endurance limit, fatigue cracking will not occur, regardless of the number of cycles.

38. Which of the following materials are susceptible to nitriding?

39. 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.

40. What is the chemical symbol for propane or propylene?

41. Non-stressed relieved __________ is susceptible to stress corrosion cracking when in contact with moist HF vapors in the presence of oxygen.

42. Sigma phase occurs in Ferritic, martensitic, austenitic and duplex stainless steels when exposed to temperatures in the range of _____.

43. The major factors affecting high temperature sulfidation are the temperature, the presence of hydrogen, the H²S concentration and the ________.

44. ________ greatly increases the probability and severity of blistering, HIC and SOHIC damage.

45. All piping and equipment exposed to HF acid at any concentration with hardness levels above the recommended limit (237 BHN) are subject to _________.

46. The primary factors affecting high temperature oxidation are metal temperature and _______.

47. 300 Series SS can suffer pitting corrosion, crevice corrosion and ________ in fresh, blackish and salt water.

48. What structure is 304 stainless steel?

49. Creep and stress rupture is more likely in a _________ grained material than a _______ grained material.

50. The endurance limit is usually about:

51. Which of the following materials is susceptible to carburization?

52. Mechanical fatigue can cause cracks that initiate from the surface and often form a:

53. __________ 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.

54. 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 _________.

55. 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.

56. Which of the following are susceptible to thermal fatigue?

57. Sour water corrosion in _________ containing environments may be accompanied by carbonate SCC.

58. Carbon steel is susceptible to SCC when used in ___________ service.

59. Which of the following materials are the least susceptible to caustic embrittlement?

60. With CO² corrosion, increasing temperatures _________ corrosion rates up to the point where CO² is vaporized.

61. Steel hardness, __________ and stress are critical factors in causing hydrogen stress cracking.

62. With sour water corrosion, at a given pressure, the H²S concentration in the sour water _________ as temperatures ________.

63. 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.

64. Cadmium and lead will cause LME on _____________.

65. Key factors affecting thermal fatigue are the magnitude of the temperature and the __________.

66. Protection in a boiler from boiler feed water corrosion is accomplished by:

67. Ammonium chloride salts may be whitish, greenish or _________.

68. Which of the following is not a primary factor contributing to erosion-corrosion?

69. Steel cleanliness and _______ have a significant influence on toughness and resistance to brittle fracture.

70. With sour water corrosion, streams with a pH below ________ indicate the presence of a strong acid.

71. The best way to prevent failures by atmospheric corrosion is to:

72. Cracks connecting hydrogen blisters are referred to as ________.

73. 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 _______?

74. For carbon steel, common velocity limits are generally limited to _________ fps for rich amine and _______ fps for lean amine.

75. Amine corrosion depends on the design, operating practices, the type of amine, amine concentration, temperature and _________.

76. Temper embrittlement can be identified by a(n) shift in the ductile-to-brittle transition temperature measured in a Charpy impact test.

77. Which of the following materials are susceptible to polythionic acid SCC?

78. _________ significantly increases the probability and severity of blistering, HIC and SOHIC.

79. Corrosion from oxygen in boiler feed water usually creates:

80. For pressure vessels, inspection should focus on welds of ________ operating in the creep range.

81. Amine cracking is ________ likely to occur in lean MEA and DEA services than in MDEA and DIPA services.

82. At high temperatures, metal components can slowly and continuously deform under load below the yield stress. This time dependent deformation of stressed components is known as __________.

83. 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?

84. Corrosion under insulation is more severe between ________ and ____________.

85. Application of a post-fabrication stress relieving heat treatment of about ______ is a proven method of preventing carbonate cracking.

86. Corrosion of carbon steel and other alloys from their reaction with sulfur compounds in high temperature environments is called ______. The presence of hydrogen accelerates corrosion.

87. The removal of surface material by impacting materials is called:

88. Oxidation of carbon steel begins to become significant above _________.

89. Hydrogen permeation or diffusion rates have been found to be minimal at pH _______ and increase at both higher and lower pH’s.

90. ___________ is when oxygen reacts with carbon steel and other alloys at high temperatures converting the metal to oxide scale.

91. Cracks that are typically straight, non-branching, and devoid of any associated plastic deformation are likely associated with which type of failure?

92. Alloy 400 is susceptible to LME when it comes in contact with molten ________.

93. Localized corrosion due to the concentration of caustic or alkaline salts that usually occurs under evaporative conditions is _________.

94. 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.

95. Which of the following is not a major factor associated with corrosion by sulfidation?

96. 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.

97. Which of the following materials is least affected by atmospheric corrosion?

98. Which of these materials are not susceptible to PASCC?

99. The most common method used for monitoring underground structures is measuring the structure to soil ______ using dedicated reference electrodes near the structure.

100. 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.

101. 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.

102. With sulfuric acid corrosion, carbon steel corrosion rates increases significantly if the flow velocity exceeds about ________m fps or at acid concentrations below _________.

103. 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 ________.

104. _________ is a form of carburization resulting in accelerated localized pitting which occurs in carburizing gases and/or process streams containing carbon and hydrogen. Pits usually form on the surface and may contain soot or graphite dust.

105. The sudden rapid fracture under stress (residual or applied) where the material exhibits little or no evidence of ductility or plastic deformation is called _________.

106. The removal of a material’s protective scale by impacting materials is called:

107. With high temperature sulfide corrosion (Sulfidization), noticeable increases may be found downstream of _________ injection points.

108. The presence of _________ can destabilize the scale and turn it into a nonprotective scale.

109. What is the chemical symbol for butane of butylenes?

110. General or localized corrosion of carbon steels and other metals caused by dissolved salts, gases, organic compounds or microbiological activities is called ________.

111. Geometry, stress level, _________ and material properties are the predominate factors in determining the fatigue resistance of a component.

112. Nickel based alloys usually contain ________ nickel.

113. Higher __________ containing alloys are used for improved resistance to naphthenic acid corrosion.

114. With CUI, corrosion rates __________ with increasing metal temperatures up to the point where the water evaporates quickly.

115. Temperature, ________ and stress are critical factors of stress rupture. This is usually found in furnaces with coking tendencies and fired heater tubes.

116. Geometry, stress level, number of cycles and _________ are the predominate factors in determining the fatigue resistance of a component.

117. High strength, low allow steels such as A193-B7 bolts and compressor parts are susceptible to hydrogen stress cracking. A193-B7M bolts are susceptible if __________.

118. In HF service, carbon steel forms a protective fluoride scale in dry concentrated acid. Loss of the protective scale through high _________ or turbulence will result in greatly accelerated corrosion rates.

119. Corrosion rates of the anode will be less affected if there is a _________ anode to cathode ratio.

120. Contrary to a pure mechanical fatigue, there is no _________ load in corrosion-assistant fatigue. Corrosion promotes failure at a lower stress and number of cycles than the materials normal endurance.

121. Corrosion by HF (Hydrofluoric) acid can result in high rates of general or localized corrosion and may be accompanied by hydrogen cracking, blistering and ________.

122. Which of the following alkanolamine systems is the most aggressive in causing amine corrosion?

123. Which of the following are affected by sulfidation?

124. 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.

125. Corrosion due to acidic sour water containing H²S at a pH between 4.5 and 7.0 is called sour water corrosion. Carbon dioxide (CO²) may also be present. Which of the following materials is susceptible to sour water corrosion?

126. All ________ based materials and low alloy materials, 300 Series SS and 400 Series SS are susceptible to Sulfidation.

127. Which of the following materials are generally not suitable for HF service?

128. Titanium should not be used in known hydriding services such as _____ or ______.

129. Metallic components form a surface __________ when exposed to sulfur compounds. This may react with air (oxygen) and moisture to form sulfur acids (polythionic acid).

130. With hydrofluoric acid corrosion, corrosion rates increase with _______ temperatures and ______ HF concentrations.

131. ______ is most likely found in hard welds and heat affected zones and in high strength components.

132. Carburization can be confirmed by a substantial increase in hardness and a _______ in ductility.

133. Decarburization results in a __________, which can be confirmed by hardness testing.

134. If the BHN is 400-500 it may indicate __________.

135. Cooling water corrosion is a concern with water-cooled __________ and cooling towers in all applications across all industries.

136. With sour water corrosion, corrosion increases with __________ NH4HS concentration and __________ velocity.

137. Carbonate stress corrosion cracking is the term applied to surface breaking or cracks that occur adjacent to carbon steel welds under the combined action of ____________ and ___________ in carbonate containing systems.

138. A form of corrosion caused by living organisms such as bacteria, algae or fungi is _______ .

139. The accepted way to test for temper embrittlement is ________.

140. What test is used to determine a material’s toughness?

141. Ammonium chloride corrosion is the general or localized corrosion, often pitting, normally occurring under ammonium chloride or amine salt deposits. All commonly used materials are susceptible to ammonium chloride corrosion. A small amount of _________ can lead to very aggressive corrosion.

142. 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?

143. Changing to a more corrosion resistant and/or higher hardness material _________ improve cavitation resistance.

144. The major factors affecting high temperature sulfidation are the temperature, the presence of hydrogen, the concentration of H²S and the __________.

145. 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.

146. Susceptibility to sulfidation is determined by the _________ of the material.

147. Which of these materials is susceptible to 885º F embrittlement?

148. Increasing the chromium in steels offers no major improvement in resistance to CO² corrosion until a minimum of __________ is reached.

149. Which material does not have an endurance limit?

150. 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.

151. With Cl SCC, ________ levels of chloride ________ the likelihood of cracking.

152. In susceptible materials, the primary factor that affects sigma phase formation is the ________ at elevated temperatures.

153. ___________ is the result of cyclic stresses caused by variations in temperature.

154. With sulfidation, the presence of oxygen ________ corrosion

155. A hard, brittle surface layer will develop on some alloys due to exposure to high temperature process streams containing high levels of nitrogen compounds such as ammonia or cyanides, particularly under reducing conditions, is called _______.

156. High temperature hydrogen attack results from exposure to hydrogen at elevated temperatures and pressures. The hydrogen reacts with __________ in steel to produce _________, which cannot diffuse through the steel. The loss of carbides causes an overall loss in strength.

157. With creep, increased stress due to loss in thickness from corrosion will ________ time to failure.

158. Hydriding of titanium is a metallurgical phenomenon in which hydrogen diffuses into the titanium and reacts to form an embrittling phase. This can result in a complete loss of _________ with no noticeable sign of corrosion or loss of thickness.

159. HTHA is dependant on temperature, hydrogen partial pressure, time and _________.

160. ______ 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.

161. Cracks associated with brittle fracture will typically be _________.

162. SCC tendency ________ towards the alkaline pH region

163. With sulfuric acid corrosion, alloys such as Alloy 20 resist dilute acid corrosion and form a protective ________ film on the surface.

164. ________ eliminates the susceptibility of most common steels to SCC.

165. A fatigue fracture is brittle and the cracks are most often __________.

166. Cooling water corrosion and __________ are closely related and should be considered together.

167. Soil corrosion of carbon steel can be minimized through the use of special backfill, coatings and _______.

168. Most brittle failures occur:

169. Alloys with increased amounts of _______ show improved resistance to naphthenic acid corrosion.

170. Major factors affecting sulfidation are alloy composition, temperature and ________.

171. A brittle fracture:

172. Cracking susceptibility increases with __________ pH and carbonate concentration.

173. With steam blanketing, failure occurs as a result of _________ in the tube from the internal steam pressure at the elevated temperature.

174. ________ usually occurs when a colder liquid contacts a warmer metal surface.

175. Alloys with nickel content above _________ are highly resistant to Cl SCC. The greatest susceptibility is 8% to 12% nickel.

176. Time to failure by thermal fatigue is primarily affected by:

177. Carbon dioxide corrosion results when CO² dissolves in water to form _________ acid.

178. In a pump, the difference between the actual pressure, or head, of a liquid available (measured on the suction side) and the vapor pressure of that liquid is called Net Positive Suction Head (NPSH) available. The minimum head required to prevent cavitation with a given liquid at a given flow rate is called Net Positive Suction Head __________. Inadequate NPSH can result in cavitation.

179. 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.

180. Blistering, HIC and SOHIC have been found to occur between ambient and ________.

181. Amine cracking has been reported down to ambient temperatures with some amines. __________ temperatures and stress levels _______ the likelihood and severity of cracking.

182. Which material below is not susceptible to caustic corrosion?

183. Thermal fatigue cracks usually:

184. Refractory anchor material must be compatible with the _________ of the base metal

185. Mitigation of CUI is best achieved by _________.

186. Carbon steel and low alloy steels are subject to excessive hydrochloric acid corrosion when exposed to any concentration of HCl acid that produces a pH below______.

187. Hardness is primarily an issue with SSC. Typical low strength carbon steels should be controlled to produce weld hardness less than ________.

188. 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.

189. _________ 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.

190. ___________ cracking has been a major problem in coke drum shells.

191. Thermal fatigue cracks propagate ________ to the stress and are usually dagger shaped, transgranular and oxide-filled.

192. What standard refers to Fitness-For-Service evaluations?

193. 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?

194. Thermal fatigue is caused by:

195. Susceptibility to hydrogen stress cracking __________ with __________ hardness.

196. For 5Cr-0.5Mo, what is the threshold temperature for creep?

197. Phosphoric acid corrosion is usually found in ________ areas.

198. Carbonate SCC may easily be mistaken for SSC or SOHIC; however, the carbonate cracks are usually ________ the toe of the weld and have multiple parallel cracks.

199. The level of creep damage is a function of the material and the coincident _________ level at which the creep deformation occurs.

200. Equipment that is temper embrittled may be susceptible to _______ during start-up and shutdown.

201. Which of the following materials is least affected by brittle fracture?

202. Which of the following materials are subject to mechanical fatigue?

203. SCC generally occurs below about _______.

204. 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?

205. With sulfuric acid corrosion, the presence of oxidizers can _______ the corrosion rate.

206. Which of the following materials is susceptible to CO² corrosion?

207. General or localized corrosion of carbon steels and other metals caused by dissolved salts, gases, organic compounds or microbiological activity is called _______.

208. Cracking of dissimilar weld metals occurs on the _________ side of a weld between an austenitic and a Ferritic material operating at high temperatures.

209. Annealed steels are more resistant to Spheroidization than normalized steels. _________ grained steels are more resistant than ______ grained steels.

210. Corrosion rates of the anode can be high if there is a _______ anode to cathode ratio.

211. Most brittle failures appear as:

212. Weld heat affected zone graphitization is most frequently found in the heataffected 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________.

213. To prevent hydrogen embrittlement, use lower strength steels and _________ to temper the microstructure, improve ductility and reduce residual stresses.

214. PWHT is ___________ in preventing caustic SCC.

215. What standard refers to Risk-Based-Inspection?

216. The most important factors affecting graphitization are the chemistry, stress, temperature and _______.

217. Temper embrittlement is a metallurgical change that is not readily apparent and can be confirmed through ________.

218. Inspection for wet H2S damage generally focuses on _____ and ______.

219. Amine stress corrosion cracking is a term applied to the cracking of steels under the combined actions of ________ and __________ in aqueous alkanolamine systems used to remove/absorb H²S and/or CO² and their mixtures from various gas and liquid hydrocarbon streams.

220. A vacuum tower operating at 740º F is being entered to inspect. Several sets of Type 410 SS trays are bent at various angles. The trays are removed in order to straighten them. When an attempt is made to straighten them cracks form at the bends.

What type of damage mechanism would cause the cracks to form?

221. When carbon is absorbed into a material at elevated temperatures while in contact with a carbonaceous substance it is called carburization. Temperatures usually have to be above __________ for this to occur.

222. 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.

223. High temperature H² / H²S corrosion damage is minimized by using alloys with high _________ content.

224. Corrosion of the anode may be significantly higher ________ to the connection to the cathode, depending on solution conductivity.

225. ____________ 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.

226. 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.

227. __________ is a form of stress corrosion cracking normally occurring during shutdowns, startups or during operation when air and moisture are present. Cracking is due to sulfur acids forming from sulfide scale, air and moisture acting on sensitized stainless steel.

228. Cracking of a metal due to stress relaxation during PWHT or in service at elevated temperatures is called ______. It is most often found in heavy wall sections.

229. High strength steels are susceptible to LME when they come in contact with molten ________.

230. In most cases, brittle fracture occurs only at temperatures _________ the Charpy impact transition temperature.

231. Which of the following metals is the most anodic?

232. 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.

233. The extent and depth of decarburization is a function of temperature and ______.

234. Vessels constructed after December, 1987 are subject to the requirements of ________ of ASME Section VIII, Division 1.

235. 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.

236. ________ injection downstream of the desalter is another common method used to reduce the amount of HCl going overhead.

237. 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.

238. What structure is 410 stainless steel?

239. Sulfidation usually creates:

240. The amplitude and frequency of vibration as well as the _________ of the components are critical factors in vibration-induced fatigue.

241. ________ is a form of carbon that may promote carburization, particularly during decoke cycles where temperatures exceed the normal operating temperatures.

242. Corrosion in boiler feedwater and condensate return systems is usually the result of dissolved gases, oxygen and _______.

243. 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.

244. __________ testing is the best method to determine the susceptibility of a material to hydrogen stress cracking.

245. In fired heater tubes, dissimilar weld metal cracking forms primarily on the _______ of the material.

246. The effects of hydrogen embrittlement ___________ with _________ temperatures.

247. Units where graphitization may be suspected are the FCCU and the _____ unit.

248. Which of the following materials is affected by high temperature corrosion?

249. Which of the following alkanolamine systems is the least aggressive in causing amine corrosion?

250. Areas of vulnerability in sulfuric acid Alkylation units include reactor effluent lines, reboilers, deisobutanizer, overhead systems and the _________ treating system.

251. Caustic embrittlement cracking can be effectively prevented by means of PWHT at a temperature of _______.

252. The best method to inspect for SCC is ____.

253. Characteristic stress corrosion cracks have many branches and may be visually detectable by a __________ appearance on the surface.

254. Dissimilar weld metal cracking forms at the toe of the weld in the heat affected zone of the ________ material.

255. With decarburization, the decarburized layer will be free of carbide phases. Carbon steel will be ______.

256. Atmospheric corrosion:

257. With short term overheating, time to failure will ___________ as internal pressures or loading decrease.

258. ________ of a component is the most important factor in determining a components resistance to mechanical fatigue.

259. For a specific material, HTHA is dependent on temperature, hydrogen partial pressure, time and _________.

260. MIC is often found in _________, bottom water of storage tanks, piping with stagnant or low flow and piping in contact with some soils.

261. 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 __________.

262. __________ caustic concentrations and ________ temperatures increase the likelihood and severity of cracking with caustic embrittlement.

263. Corrosion in boiler feedwater and condensate return systems is usually the result of dissolved gases, oxygen and ________.

264. Damage from sigma phase appears in the form of ________.

265. Nitriding begins above ________ and becomes severe above _______.

266. Corrosion under insulation becomes more severe at metal temperatures between ________ and ________, where water is less likely to vaporize and insulation stays wet longer.

267. Nitriding layers are magnetic. Therefore, _________ should be checked for magnetism as an initial screening for nitriding.

268. Hydrochloric acid corrosion is a general and localized corrosion and is very aggressive to most common materials of construction. Damage in refineries is often associated with dew point corrosion in which vapors containing _______ and hydrogen chloride condense from the overhead stream of a distillation, fractionation, or stripping tower.

269. Wet H²S services or _________ acid services are process where hydrogen diffuses into the steel and hydrogen embrittlement (HE) is an issue.

270. ____________ 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.

271. What method is most used to assure boiler feed water corrosion is not occurring?

272. 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.

273. Sulfidation of iron-based alloys usually begins at about:

274. The graphitization rate ____________ with increasing temperature

275. Reheat cracking is most frequently observed in _______ grained sections of a heat-affected zone.

276. Carburization can be confirmed by substantial increases in _______ and loss of __________.

277. With very few exceptions, cooling water should always be on the ________ side to minimize stagnant areas.

278. The presence of ________ in H²S streams increases the severity of high temperature sulfide corrosion at temperatures above about 500º F

279. 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.

280. Thermal fatigue cracks usually propagate _______ to the stress and they are usually dagger-shaped.

281. ________ is a form of erosion caused by the formation and instantaneous collapse of innumerable tiny vapor bubbles.

282. Where is PASCC normally located?

283. Which of the following does not increases the likelihood of atmospheric corrosion?

284. Liquid metal embrittlement can occur if 300 Series SS comes in contact with molten _______.

285. When connected to a more anodic material, titanium may suffer severe __________.

286. ________ and _______ damage develop without applied or residual stress so that PWHT will not prevent them from occurring.

287. The creep threshold temperature for carbon steel is ________.

288. Cracking of dissimilar weld metals occurs in the __________ side of a weld joining 300

Series SS and carbon steel.

289. Hardness levels above ________ are highly susceptible to hydrogen stress cracking (HF).Time-to-failure decreases as the hardness increases.

290. A prime location for erosion is:

291. Cooling water corrosion can result in many different forms of damage including general corrosion, pitting corrosion, ________, stress corrosion cracking and fouling.

292. Mechanical fatigue is caused by:

293. Which if the following materials are not susceptible to hydrogen stress cracking?

294. 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 _________.

295. Components that have been carburized may have a change in the level of ________.

296. The grain size has an important influence on the high temperature ductility and on the reheat cracking susceptibility. A ________ grain size results in _______ ductile heat affected zones, making the material more susceptible to reheat cracking.

297. Sulfuric acid promotes general and localized corrosion of carbon steel. Carbon steel heat affected zones may experience severe corrosion. Acid concentration, temperature, alloy content and ____________ are critical factors affecting sulfuric acid corrosion.

298. Carbonate SCC can occur at relatively low levels of ________ but usually occurs at welds that have not been stressed relieved.

299. HCL acid corrosion is found in several units, especially _______ and ________, units, hydro processing units and catalytic reformer units.

300. Welds joining dissimilar materials (ferritic and austenetic) may suffer __________ related damage at high temperatures due to differential thermal expansion stresses.


 

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