3) VT and UT for thk loss. delayed cracking. . 3) Cracking in 300 SS typical transgranular and difficult to distinguish from Cl-SCC. API 571 helps link these technologies and collate the information into one source document. 5) UT is not good for detecting damage. 2) Ignition temp for most alloys are near melt point in non flow condition. L grades do not sensizie if long term temp < 750F All non-PWHT carbon steel piping and eqpt in lean amine service including contactors. Appear in HAZ initiating from HIC or SSC. 5) Max cyclical stress ampliude is determined for 106-107 cylces (desired in lifetime) 7) Inclusions in metal (dirty steel) have accelerating effect on FC. DamagePlus™ software, from E 2 G|The Equity Engineering Group, Inc., has been updated to the newest edition of API RP 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry, 2 nd Edition, April 2011.. With a technical basis in the updated API RP 571 and WRC 489, the new DamagePlus™ software is a … fired heater tubes + PV components hot formed during fabrication can be affected. DE cracks magnetite.. Found that residual stress. 1) Heat flux & fluid flow critical factors 2) Flame impingement from damaged or misdirected burners 3) on Water side anything that restricts flow (condensate. sour water if welds not susccetible to embrittlement. phase below 200F (93C). 3) CE occur due to steam cleaning in caustic service. The … no cracking in deaerated cond + max potential in water content 0. above threshold 2) Storage sphere made with 2) H2 can come from welding by wet slighly HS steel more electrode / flux (delayed cracking) + susceptible.1-0. 2) WFMT for SB cracks. some 300 Series SS and Cu based alloys Increasing temp incr CR upto point where CO2 is vaporized Carbon steel and low alloy steels 300 SS are highly resistant 400 SS and DSS also resitant . proper burner management to prevernt flame impingement. NH3 incr pH significantly results in alkaline sour water and NH4HS corrosion. Ti and some Ni base alloys have good resistance to dilute HCL. 1) RC requires high stresses and more likely in thick sections 2) RC occurs at ET where creep ductility is insufficient to accomodate strain.7. occurring under ammonium chloride or amine salt deposits. .Carbonate Stress Surface breaking cracks occur adjacent to CS Corrosion Cracking welds under the combined action of tensile (ACSCC) stress and corrosion in systems containing free water phase with carbonate (some H2S also present). Use of PWHT 1100 followed by rapid cooling. H2 assisted cracking. 4) check pipe supports and spring hangers 5) Damage to insul jacketing can cause CUI. 2) UT and RT for loss of thickness. 3) In cycling boiler. trucks. 1) Likely decrease by PWHT or applying coating 2) Avoid design with local tensile stress. 800. damage.000 psi pp). 10-15 years to cause tube leak . LRUT for long pipe run. • API 571 –Damage Mechanisms Affecting Fixed Equipment in the Refining Industry (2ndEdition 2011) • NBIC Part 2 Section 3 Corrosion and Failure Mechanisms (2017 Edition) • API 580/581 Risk Based Inspection/RBI Technology BRD • API 584 Integrity Operating Window (1stEdition 2014) • API 970 Corrosion Control Documents (Draft) 7) Nitrided layer magnetic. H2CO3 etc. DSS. 1) Most often found in HX. SSC is form of H2 Embrittlement + Amine cracking & Carbonate crackign are simlair and also confused sometimes with wet H2S cracking Same mechanism that is responsible for SSC in wet H2S environ except that HF acid generating the H2 . 2) 300 SS & NI alloy have very thin dark scale (generally no metal loss) 3) Monitor process cond for HT trend 4) Monitor temp with IR scan or skin TC 5) Measure thk loss with external UT 1) Resist generally achieved by upgrading to higher Cr alloy 2) Eqpt constructed with clad or solid 300 + 400 SS. matl exhibit very high surface hardness. Ni alloys also affected depends on Cr % Cu alloys form sulfide at lower temp than CS Typically above 1100F to allow C diffusion in to metal Carbon steel.4. Loss in ductility of high strength steels due to the penetration of atomic H2 can lead to brittle cracking, Surface initiated cracks of CS under comb action of tensile stress and fuel grade ethanol (FGE ASTM D4806) or FGE / gasoline blend. H2 reformers & FCC units). 1) Cracking typically parallel to weld in base metal.1) Cracking effective prevented by PWHT of CS @10050F (repair welds. Al brass) in some brackish and sea water. 3) Piping may be inspected by inline insp by inline inspection devices, guided UT, pressure testing (indirect) or visually. piping manifold. but mostly SB. high nickel CI . 5) SWUT where WFMT not feasible + ACFM with less surface prep as in HAZ.1) Use LS steels and PWHT to temper microstructure. measure pH of water from OH accumulator 6) Properly placed corrosion probes + coupons provide rate and extent of potential damage. 2) E-SCC not reported in FGE manufacturer eqpt and tanks or in transportation eqpt (barges. Presence of H2 accelerates (sulfidic) corrosion Caruburization Carbon is absorbed into material at elevated temp while in contact with carbonaceuos material or environment.Corrosion Mechanism Description Oxidation O2 reacts with CS and other alloys at high temperature converting metal to oxide scale. damage only seen with metallography. galv steel. 5) PT not effective for scale filled cracks and should not be used singly. methan formation and cracking.g. hot lean amine piping. 430 & 436). 2) Low creep ductility failures found in weld HAZ at nozzles cat reformer. upgrade to 300 or 400 SS internals in absorber and regnenerators. 4) Refractory resistant to erosion and abrasion and needles compatible with process env. bluish corrosion product. 1) BFW corrosion is usually result of dissolved gases. catalytic reformers. 4) SSC prevented by reducing hardness of weld and HAZ to 200HB (Max) by preheat.1) Effective barrier that protect steel sruface from wet H2S can prevent damage including alloy cladding and coatings. CS. 3) In FH. External treatment system + deaerating equpment + feedwater lines. API 571 Damage Mechanisms Affecting Fixed Equipment in the Refinery This course has 3 parts and provides the learner with the knowledge in the API 571 document. 3) Alloy C276 for high vel area where 316L inadequate 1) General or localized corrosion of CS. 400 Series SS. 3) L grades SS 304L/316L/317L 4) PASCC is inspection challene bec crack may sensitize if several hours above not occur until shutdown.Prevention Inspection / Monitoring 1) If eqpt to be opened. FW piping. Increasing resistance: Carbon steel. LAS in API 941 (reasonably conservative for CS up to 10.Refining Indsutry Affected Equipment Critical Factors HP units.9v sce.3. blistering and HIC/SOHIC as per API RP 751. a- Weld HAZ graph occurs at low temp. 2) Cu and Ni alloys generally not susceptible to ASWC but Cu alloy vulnerabel to corrosin with NH3. relaxation cracking 2) Surface cracks by UT. 321 and 347 are highly resistant 1) Uniform thk loss and FeS scale formation (scale is 5 times volume of metal loss + tightly adherent gray scale) 2) UT. 2) By metallogrpahy. Increasing temperature and stress level incr the likelihood and severity of cracking.1.5. minimize galvanic effect. Surface prep usually not required for ACFM. 3 0 obj
alloy and stress level 2) FISH MOUTH Failures by thinning at fractured surface. 1) Damage (strain rate) is sensitive to load and temp. Cavitation. s/d. 2) if conc mecanism present. wet dry cond conducive to cracking 3) SCC occurs above 2 pH. branched TG cracks difficult to distinguish from NH3 SCC. 4 0 obj
Change in microstructure after long 800-1100 F term oper of CS & 0.Mo steel Loss in strength, ductility & creep Severe > 1000 in 5 yr resistance Slight ≤ 850 in 30-40 yr FeC decompose into graphite nodules. 1) Design: FC initiate at surface notches or 1) Best defense is good design stress raisers under cyclic loading. 1) For Cu alloys: Surface breaking cracks may show Bluish Corrosion product. exposure to fires or HT gases.Decarburization Condition where steel loses strength due to removal of carbon and carbides leaving iron matrix. Steam blanketing can cause caustic corrosion (Causitic Gouging) + Short term Over Heating. but at advanced stage) 1) Rotating Eqpt: Modify corr environ by coatings /inhibitors. Cu. 1) Sulfidation rate increase with incr H2S content and increasing temp.15% wt. 5.2.1. loss of ambent temp properties (toughness / ductility). erosion resistant refractory 3) For EC: Best mitigated by more CR alloy or altering process (not by substrate hardness only) 4) higher Mo for NAC 5) impingment plates and ferrultes in HX 1) Inadequate NPSH (min head required to avoid cavitation). reformers. some LAS. Heat Stable Amine Salts (HSAS) & contaminants. fractionator tower. waste heat boiler. Affected metallurgy Not Affected All 300 Series are highly susceptible. 2) Mix point with water release heat and high CR where acid diluted. Increasing Cr increase resistance to sulfidation (Ni alloys similar to SS with similar Cr content). <>/ExtGState<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/Annots[ 17 0 R] /MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>>
hardness near fusion line with ferr and 3) Consider buttering on ferr susceptible to H2 cracking or SSC. Fe4N) only confirmed by metallography. . sulfurous and sulfuric acid DP corrosion can occur if metal temp is below DP. units & catalytic reformers + brittle surface that may crack or spall on ethylene pyrolosys and steam cooling. high dissolved salt conc. Proper selection of refractory. 2) In significant flow. 4) Cracks may be mistaken for SSC or SOHIC but further away from weld toe. Chloride SCC and Organic acid corrosion of tower OH system . RFEC. fissureing and decarb near surface (but decarb may be due to HT). 3) CS and LAS subject to high corr when exposed to any conc of HCL at pH < 4. turb & d/s units exposed to acid causes high CR. H2. . CS is susceptible to SCC in anhydrous NH3. Alloy 20.Primarily affects carbon steel SS. denicklification and graphitic corrosion. 316L and Alloy C276. matl can be cut with knife. PWHT is effective to prevent SCC. gas.2.Refining Affected Equipment Critical Factors 1) HE tubes. 3) OH sys of regenertors on CO2 removal plant 1) increasing partial press of CO2 causes lower pH and higher CR. H2S below 50. ammonia &cyanides concentrati ons.HAZInterganula r. Hardness testing Carbonate >200F Stress Susceptibili Corrosion ty Cracking increases with pH and carbonate concentrati onPropagate parallel to welds. 5) Change in surface color to Dull gray. blisters. . bellows). Range (F) Affected metallurgy Not Affected Iincreasing resistance: CS. EMBEDDED cracks found only through UT. cyclone. 2) Large grain size less result in less ductile HAZ making matl susceptible to RC. holes and valleys (directional pattern). UT for internal and UT scans or profile radiography for external. pipign & eqpt in refrg & some LO refining process. ko drum.free water pH<4 and dissovled H2S . Ni base alloys. 2) Filming amines can prevent corrosion if it doesn’t react with OA.1) 300 SS can be used at temp < 140F as Cl-SCC not likely. 2) Attack may be uniform (layer type) or localized (plug type). . solid or clad with 300SS. 1. that handle phenol-water. fire water piping.g. 3) Transverse cracks occured in 2. 5) Metallography required to confirm DE. sulfidation. high salinity. use low stress improves FR). 1) Often difficult ot predict cond for dealloy in particular environment. piping and Ti eupt operate > 2) Occurs over time as H2 absorbs and 165F & also above 350F (177C) reacts to form embrittling hydride. venturis. -- Pump casings. matl like Zn galvinzing. OD or within wall thk. then internal decarb.) 3) Sulfur inhibits carburization and often added in small amounts into process streams of steam/ gas crackers of olefin & thermal hydroalkylation units 1) Depth of carburization confirmation by metallography 2) Carburiz can be confirm by substantial increase in hardness and loss of ductility 3) Volumteric increase in advance stage 4) Incr in Ferromagnetism of some alloys. Ti or Al HX comp. H 2 is formed due to corrosion.use CS with Carbon equivalent (CE) <0. found in crude oils can crack may pass thru wall in seconds of condense embrittling brass. 5) PWHT can minimize SOHIC but not blistering and HIC. but reported as low as 350F. sanding to remove tight deposit. 2) Cracking may also occur in weld. species alloys of 50Cr50Ni show improved resistance Nitrid begins > 600F Nitrid severe > 900F Ni base alloys (containg 30 to 80% Ni) are more resistant (>750F. The table was reconstructed in a manner that illustrated these claims. . 3 cond must be met. FCC. low alloy Alloys with steels. these collapsing bubbles exert severe localised impact forces and result in metal loss Machanical degradation that occurs when component exposed to cyclic stresses for an extended period. 2) BFW treatment to prevent restricted fluid flow 3) VI of tubes for bulging. castable. Hydrogen diffuses into titanium to form hydride (brittle)PH<3. 3) SSC most likely in hard weld and HAZ. 2) Decarb layer free of carbide. 5) Cladding or non metallic coatings for barrier to H2 diffu will prevent cracking. 1Cr-0. heater supports) 1) CS. 1) Damage minimized by using alloys with high Cr content 2) 300 SS such as Types 304L. 3) High quality non metallic coatings provide long term protection. 3) Control local press drop to minimize flashing. 2)Material with lost ductility such as CrMo (temper embr) more susceptible.All metals & Alloys -- 1) FCC cokers. bows. 3) UT and RT inspection for thk loss. 4) Special care with steam tracing & steam out of non PWHT CS eqpt. History. non branching devoid of plastic deformation (cleavage) 2) Inspection normally NOT USED to mitigate BF. 2) Very small quantity of molten metal 2) LME couples (SS300 rub with sufficient to cause LME w/o high TS. 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