api 579-2_5.6 ffs

API 579-2, 5.6API 579-1 Fitness-For Service AssessmentPage1

Plant IDA PlantEquipment Number: ABC-1234Equipment: LP SeparatorEquipment Type:VesselDate: 5th September 2014

IntroductionThe following Level 2, Fitness-For-Service assessment was carried out on A Plant Production Platform, ABC-1234, LP Separator, Nozzle: N-01, in accordance with API 579-1, Part 5, for Type 'B' pressurized components subject to local metal loss resulting from internal corrosion, using the methods outlined in API 579-2, 5.6.

A region of local internal corrosion was found in the NPS-14, Schedule 140 nozzle during inspection of the pressure vessel (see inspection data).

The vessel was constructed to the ASME B&PV Code, Section VIII, Division 1, 1988 edition and is not in the fatigue service.

A Level 2 assessement was performed because the corrosion is at a major structural disconitnuity, that is, at a nozzle.

The assessement was performed, to determine if the vessel is acceptable for continued operation, using the Limit Analysis Method. This method is effective for evaluating a region of local metal loss at nozzles where the average thickness is used to represent the metal loss in the nozzle reinvorcement zone (see Figures A.6 and A.7).

The zone for thickness averaging has been calculated in accordance with API 579-1, Part 4, paragraph 4.3.3.4, details of which can be found in Appendix 1 of this report.

SummaryThe area reinforcement calculation using the limit analysis approach is acceptable based on the corroded dimension of the nozzle configuration and the stated design conditions.

The Level 2 Assessment criteria are satisfied.

The vessel is acceptable for continued operation.

API 579-1 Fitness-For Service AssessmentPage2


Nomenclature

cnLOSSn + FCAn.csLOSSs + FCAs.d1nozzle diameter (for required spacing between two openings calculation).d2nozzle diameter of nearest opening.dicurrent inside diameter of the nozzle including the specified FCA.dmnozzle or branch pipe mean diameter corrected for LOSS and FCA as applicable.dooutside diameter of the nozzle corrected for LOSS and FCA as applicable. Dinside shell diameter corrected for LOSS and FCA as applicable.Dinominal inside shell diameter, not corrected for LOSS and FCA.Dooutside diameter corrected for LOSS and FCA as applicable.Dmvessel or run pipe mean diameter corrected for LOSS and FCA as applicable.FCAnnozzle future corrosion allowance.FCAsshell future corrosion allowance.Laxial length of nozzle with thickness tn .Lndimension to define the height of the reinforcement zone (see Figure 4.9).Lvdimension to define the width of the reinforcement zone (see Figure 4.9).LOSSnmetal loss in the nozzle from prior periods of operation equal to the nominal (or furnished thickness if available) minus the minimum measured thickness at the time of the inspection.LOSSsmetal loss in the shell from prior periods of operation equal to the nominal (or furnished thickness if available) minus the minimum measured thickness at the time of the inspection.nozzle calculation parameter. Pinternal design pressure.Rsinside radius of small cylinder at a conical transition corrected for LOSS and FCA as applicable.Snallowable stress for the nozzle. Svallowable stress for the vessel.the average nozzle thickness in the nozzle reinforcement zone.the average shell thickness in the nozzle reinforcement zone.tshell thickness.tenominal thickness of the reinforcing pad = 0.00. (See Appendix 2 formulas).trrequired thickness of the vessel wall computed with E = 1.0.tnfurnished nozzle wall thickness (see Figures A.6 and A.7) For an integrally reinforced nozzle (see Figure A.7),tpfurnished wall thickness of the pipe section for an integrally reinforced nozzle (see Figure A.7). tvfurnished vessel thickness.tstdnominal thickness of ANSI B36.10 standard weight pipe. UTSultimate tensile strength.YSyield stress.



Vessel Shell Design DataNotes

MaterialSA-516, Grade 70, year 1988Allowable Stress (Sv)17500psiDesign Conditions (P)185psig @350 FInside Diameter (Di)60.000inMax. Design Temperature350FInside Diameter (Do)60.250inInside Radius (Rs)30.000inNominal Thickness (t) (tv)0.600inCorrosion Allowance (FCAs)0.125inMetal Loss (LOSSs)0.000inWeld Joint Efficiency (E)1.0Cylindrical VesselYES

Nozzle Design Data

MaterialSA-106, year 1988Ferrous materialYESYES or NOAllowable Stress (Sn)17500psiDesign Conditions (P)185psigMinimum Specified Yield Strength (YS)38000psiMin. Specified Ultimate Tensile Strength (UTS)70000psiMax. Design Temperature350FTemp. limit (API 579-2, Table A.2)800FNominal Pipe Size (NPS)14inInside Diameter (Do) (d1) (di)14.000inNominal Thickness (tn) or (tp)1.250inFigures A.6 and A.7Corrosion Allowance (FCAn)0.125inMetal Loss (LOSSn)0.000inAxial Length of Nozzle with Thickness tn (L)5.000inWeld Joint Efficiency (E)1.0Nozzle Loads0.0NegligibleThickness Re-pad (te)0.000inDistance to Nearest Structural Discontinuity45.00inOD of Nearest Major Structural Discot. (d2)12.75inIs the Opening CircularYESIs Nozzle Normal to the Surface of the VesselYESIs the Vessel CylindricalYESNom. Tkns ANSI B36.10 Std. Weight Pipe (tstd)0.375inSee Limitations (x), below



Inspection Data

A sketch of the nozzle and metal loss are shown below.

The average nozzle thickness in the nozzle reinforcement zone is 0.875 in. The corrosion is uniform for all inspection planes.

A Level 2 assessment is performed as per API 579-1 paragragh 5.4.3.5 because the corrosion is at a major structural discontinuity (a nozzle). The assessment procedure in Part 4, paragraph 4.4.3.3. is used.

From the inspection data:

0.875in

0.600in

Required thickness of shell:

0.320inAPI 579-1 REFERENCE?

Determine the corroded shell and nozzle mean diameters:

61.200in

60.250in

60.725in

14.000in

12.500in

13.250in



The following assessment is performed using the limit analysis method:(See API 579-1, Annex A, A.3.11.b).

Limitations

(i) Temperature Limits; API 579-1, Table A.2.Maximum Design Temp =350FTemperature Limit =800FAre the temperature limits satisfied:YES(ii)Are the nozzle and shell fabricated from ferrous material:YESWith, YS = minimum specified yield strength, and UTS = minimum specified ultimate tensile strength.YS = 38000psiUTS = 70000psiIs YS/UTS < 0.80: YES(iii)Does the opening not exceed NPS 24: YES

(iv)with0.2182and101.2083

ifthenFALSE

or ifthenTRUE

Do either of the parameters meet the above requirements:YES(v)The opening is not subject to cyclic loading:YES(vi)The opening is in a cylindrical vessel:YESwith0.125inIs the opening located at a distance of

from any major structural discontinuities:YESDistance9.6673inDistance to nearest structural disconinuity =45.00in



(vii)The spacing between two openings:withd1 = 14.000inandd2 = 12.75inRequired spacing = 40.125inDoes the spacing meet minimum requirements:YES(viii)Is the opening circular:YESIs vessel cylindrical:YES

Is nozzle normal to the surface of the cylindrical vessel:YES

(ix)If L

api 579-2_5.6 ffs

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