API RP 581 - 3rd Ed.2016 - Add.2-2020 - Risk-Based Inspection Methodology
2-122 API RECOMMENDED PRACTICE 58117.9 FiguresOperatingTemperatureSTEP 1: Determine the susceptibility usingTable 17.2.DriverCrackspresent?YesHighSusceptibilityCracksRemoved?NoSTEP 2: Determine the Severity Index usingTable 17.3.YesNoFFSSTEP 3: Determine the in-service time, age,over which external corrosion may haveoccurred.STEP 4: Determine the number of inspectionsand the corresponding inspectioneffectiveness category for all past inspectionsusing Table 2.C.10.2.STEP 5: Determine the base damage factorfor external CLSCC using table 6.3.STEP 6: Calculate the escalation in thedamage factor based on the time in-servicesince the last inspection using Equation(2.76).Figure 17.1—Determination of the External ClSCC DF18 External CUI ClSCC DF—Austenitic Component18.1 ScopeThe DF calculation for insulated austenitic stainless steel components subject to CUI ClSCC is covered inthis section.18.2 Description of DamageInsulation can be a source of chlorides and/or cause the retention of water and chloride concentrating underthe insulation. CUI ClSCC can be caused by the spray from sea water and cooling water towers carried bythe prevailing winds. The spray soaks the insulation over the austenitic stainless steel components, thechloride concentrates by evaporation, and cracking occurs in the areas with residual stresses (e.g. weld andbends). Other cases of cracking under insulation have resulted from water dripping on insulated pipe andleaching chlorides from insulation. Mitigation of CUI ClSCC is best accomplished by preventing chlorideaccumulation on the stainless steel surface. This is best accomplished by maintaining the integrity of theinsulation and by preventing chloride ions from contacting the stainless steel surface with a protectivecoating. An immersion grade coating suitable for stainless steel is the most practical and proven method of
RISK-BASED INSPECTION METHODOLOGY, PART 2—PROBABILITY OF FAILURE METHODOLOGY 2-123protection. However, wrapping of the stainless steel with aluminum foil that serves as both a barrier coatingand a cathodic protection (CP) anode has also proven to be effective.CUI damage in austenitic stainless steels occurs at temperatures between 50 °C and 175 °C (120 °F and350 °F) although exceptions have been reported at lower temperatures.a) Below 120 °F (50 °C), it is difficult to concentrate significant amounts of chlorides.b) Above 350 °F (175 °C), water is normally not present and CUI damage is infrequent.c) Austenitic stainless steel piping that normally operates above 500 °F (260 °C) can also suffer severeExtClSCC during start-up if the insulation is soaked from deluge system testing or rain during downtime.Heating and/or cooling intermittently into this range creates the conditions for CUI ClSCC to occur.18.3 Screening CriteriaIf all of the following are true, then the component should be evaluated for susceptibility to CUI ClSCC.a) The component’s material of construction is an austenitic stainless steel.b) The component is insulated.c) The component’s external surface is exposed to chloride-containing fluids, mists, or solids.d) The operating temperature is between 50 °C and 150 °C (120 °F and 300 °F) or intermittently operated inthis range.18.4 Required DataThe basic component data required for analysis are given in Table 4.1, and the specific data required fordetermination of the DF for CUI ClSCC are provided in Table 18.1.18.5 Basic AssumptionThe DF for external CUI ClSCC is based on the method in Section 12.18.6 Determination of the DF18.6.1 OverviewA flow chart of the steps required to determine the DF for external CUI ClSCC is shown in Figure 18.1. Thefollowing sections provide additional information and the calculation procedure.18.6.2 Inspection EffectivenessInspections are ranked according to their expected effectiveness at detecting the specific damagemechanism. Examples of inspection activities that are both intrusive (requires entry into the equipment) andnonintrusive (can be performed externally) are provided in Annex 2.C, Table 2.C.10.4.If multiple inspections of a lower effectiveness have been conducted during the designated time period, theycan be equated to an equivalent higher effectiveness inspection in accordance with Section 3.4.3.
- Page 117 and 118: RISK-BASED INSPECTION METHODOLOGY,
- Page 119 and 120: RISK-BASED INSPECTION METHODOLOGY,
- Page 121 and 122: RISK-BASED INSPECTION METHODOLOGY,
- Page 123 and 124: RISK-BASED INSPECTION METHODOLOGY,
- Page 125 and 126: RISK-BASED INSPECTION METHODOLOGY,
- Page 127 and 128: RISK-BASED INSPECTION METHODOLOGY,
- Page 129 and 130: RISK-BASED INSPECTION METHODOLOGY,
- Page 131 and 132: RISK-BASED INSPECTION METHODOLOGY,
- Page 133 and 134: RISK-BASED INSPECTION METHODOLOGY,
- Page 135 and 136: RISK-BASED INSPECTION METHODOLOGY,
- Page 137 and 138: RISK-BASED INSPECTION METHODOLOGY,
- Page 139 and 140: RISK-BASED INSPECTION METHODOLOGY,
- Page 141 and 142: RISK-BASED INSPECTION METHODOLOGY,
- Page 143 and 144: RISK-BASED INSPECTION METHODOLOGY,
- Page 145 and 146: RISK-BASED INSPECTION METHODOLOGY,
- Page 147 and 148: RISK-BASED INSPECTION METHODOLOGY,
- Page 149 and 150: RISK-BASED INSPECTION METHODOLOGY,
- Page 151 and 152: RISK-BASED INSPECTION METHODOLOGY,
- Page 153 and 154: RISK-BASED INSPECTION METHODOLOGY,
- Page 155 and 156: RISK-BASED INSPECTION METHODOLOGY,
- Page 157 and 158: RISK-BASED INSPECTION METHODOLOGY,
- Page 159 and 160: RISK-BASED INSPECTION METHODOLOGY,
- Page 161 and 162: RISK-BASED INSPECTION METHODOLOGY,
- Page 163 and 164: RISK-BASED INSPECTION METHODOLOGY,
- Page 165 and 166: RISK-BASED INSPECTION METHODOLOGY,
- Page 167: RISK-BASED INSPECTION METHODOLOGY,
- Page 171 and 172: RISK-BASED INSPECTION METHODOLOGY,
- Page 173 and 174: RISK-BASED INSPECTION METHODOLOGY,
- Page 175 and 176: RISK-BASED INSPECTION METHODOLOGY,
- Page 177 and 178: RISK-BASED INSPECTION METHODOLOGY,
- Page 179 and 180: RISK-BASED INSPECTION METHODOLOGY,
- Page 181 and 182: RISK-BASED INSPECTION METHODOLOGY,
- Page 183 and 184: RISK-BASED INSPECTION METHODOLOGY,
- Page 185 and 186: RISK-BASED INSPECTION METHODOLOGY,
- Page 187 and 188: RISK-BASED INSPECTION METHODOLOGY,
- Page 189 and 190: RISK-BASED INSPECTION METHODOLOGY,
- Page 191 and 192: RISK-BASED INSPECTION METHODOLOGY,
- Page 193 and 194: RISK-BASED INSPECTION METHODOLOGY,
- Page 195 and 196: RISK-BASED INSPECTION METHODOLOGY,
- Page 197 and 198: RISK-BASED INSPECTION METHODOLOGY,
- Page 199 and 200: RISK-BASED INSPECTION METHODOLOGY,
- Page 201 and 202: RISK-BASED INSPECTION METHODOLOGY,
- Page 203 and 204: RISK-BASED INSPECTION METHODOLOGY,
- Page 205 and 206: RISK-BASED INSPECTION METHODOLOGY,
- Page 207 and 208: RISK-BASED INSPECTION METHODOLOGY,
- Page 209 and 210: RISK-BASED INSPECTION METHODOLOGY,
- Page 211 and 212: CONTENTSTABLE 2.A.1—LEADERSHIP AN
- Page 213 and 214: 2.A-2 API RECOMMENDED PRACTICE 581T
- Page 215 and 216: 2.A-4 API RECOMMENDED PRACTICE 581T
- Page 217 and 218: 2.A-6 API RECOMMENDED PRACTICE 581T
RISK-BASED INSPECTION METHODOLOGY, PART 2—PROBABILITY OF FAILURE METHODOLOGY 2-123
protection. However, wrapping of the stainless steel with aluminum foil that serves as both a barrier coating
and a cathodic protection (CP) anode has also proven to be effective.
CUI damage in austenitic stainless steels occurs at temperatures between 50 °C and 175 °C (120 °F and
350 °F) although exceptions have been reported at lower temperatures.
a) Below 120 °F (50 °C), it is difficult to concentrate significant amounts of chlorides.
b) Above 350 °F (175 °C), water is normally not present and CUI damage is infrequent.
c) Austenitic stainless steel piping that normally operates above 500 °F (260 °C) can also suffer severe
ExtClSCC during start-up if the insulation is soaked from deluge system testing or rain during downtime.
Heating and/or cooling intermittently into this range creates the conditions for CUI ClSCC to occur.
18.3 Screening Criteria
If all of the following are true, then the component should be evaluated for susceptibility to CUI ClSCC.
a) The component’s material of construction is an austenitic stainless steel.
b) The component is insulated.
c) The component’s external surface is exposed to chloride-containing fluids, mists, or solids.
d) The operating temperature is between 50 °C and 150 °C (120 °F and 300 °F) or intermittently operated in
this range.
18.4 Required Data
The basic component data required for analysis are given in Table 4.1, and the specific data required for
determination of the DF for CUI ClSCC are provided in Table 18.1.
18.5 Basic Assumption
The DF for external CUI ClSCC is based on the method in Section 12.
18.6 Determination of the DF
18.6.1 Overview
A flow chart of the steps required to determine the DF for external CUI ClSCC is shown in Figure 18.1. The
following sections provide additional information and the calculation procedure.
18.6.2 Inspection Effectiveness
Inspections are ranked according to their expected effectiveness at detecting the specific damage
mechanism. Examples of inspection activities that are both intrusive (requires entry into the equipment) and
nonintrusive (can be performed externally) are provided in Annex 2.C, Table 2.C.10.4.
If multiple inspections of a lower effectiveness have been conducted during the designated time period, they
can be equated to an equivalent higher effectiveness inspection in accordance with Section 3.4.3.
Change language