Tube ThicknessE3RevClient:OGPECalculation No:FH - 001Project:API RP 530 Sample 6.3.4 CalculationRev :ADate:28-Feb-14Subject:Heater Tube Thickness CalculationBy:KChk'd:App'd:

Design BasisAPI Standard 530 Sixth Edition Sep 2008/ ISO 13704:2007 (E) Errata 21 June 2007

DefinitionsDi=inside diameter of a new tubeDi=inside diameter of a tube without corrosion allowance; used in design calculationsDo=outside diameter of a new tube=stress thickness, thickness to meet allowable stress excluding all allowances=pel*Do/(2el + pel)=pr*Do/(2r + pr)CA=corrosion allowance, thickness added to allow for material loss during the design lifemin=minimum thickness of a new tube, taking into account all appropriate allowances= + CA= + fcorr*CAB = CA/Schedule 40 aw for Ferritic; Schedule 10S for Austeniticav=average thickness of a new tube, taking into account mill tolerancefcorr=corrosion fraction. Accounts for the fact in the initial years corrosion allowance provideshigher thickness; reduces stress; correspondingly, the rupture life is increased

tDL=design life, not necessarily the same as retirement or replacement life, hours=100,000hoursTd=design metal temperature, tube metal or skin temperature used for designTeq=equivalent tube metal temperature (TMT), calculated constant metal temperature that in a given time period produces the same creep as does a linearly changing metaltemperature. Based on start of run and end of run conditions. Not considered here.V = no(T*/T*sor)ln(A/0)N = no(/0)

TA=temperature allowance, included in design metal temperature to account formaldistribution, operating unknowns and design inaccuracies. Default = 15C (25F)

pel=elastic design pressure, press for short periods such as a PSV opening/ pump shut-inel=elastic allowable stress, allowable stress in the elastic rangepr=rupture design pressure, maximum operating pressure during normal operationr=rupture allowable stress, allowable stress for the creep-rupture rangen=rupture exponent, parameter used for design in the creep-rupture range=Owner furnished data

AssumptionsNo consideration included for adverse environmental effects such as graphitization, carburization, orhydrogen attackDesign based on seamless tubes; Assumed tubes do NOT have longitudinal weldsAssumed thin tubes viz. thickness-to-outside-diameter ratio, min/Do, of less than 0.15No considerations included for the effects of cyclic pressure or cyclic thermal loadingDesign for internal pressure only. Stresses from supports, end connections etc not considered.

Material Code:15See Table B138:E156FPS1UnitsSI2UnitsISO 13704PMPagMPaCALCULATION SHEETtCSI unitsT AbsoluteK273HeaterSamplePlantSampleLengthmmCoilRadiant CoilMaterial /ASTM Spec.SA312 TP 347HCalculation of minimum thicknessElastic designRupture designParallel Calculation as a Pipe - Elastic Stress - PV LiteOutside diameter,mmDo =168.3Do =168.3tmin =9.6012mmDesign pressure,MPagpel =6.2pr =5.8tnom =10.9728mmMaximum or equivalent metal temperature,CTmax =705Tmax =705CA =0.5mmTemperature allowance,CTA =TA =CAE =0Design metal temperature,CTd =705.0Td =705.0S =39.46MPaDesign life, htDL =100,000E =1Allowable stress at Td, FigE15MPael =113r =37.3Stress thickness, equation (2) or (4),mm =4.49 =12.14Thickness due to internal pressureCorrosion allowance,mmCA =3.18CA =3.18 =P(D/2-CAE)/(SE+0.4P)Corrosion fraction, Figure 1, n = 4.5B =0.2619214457fcorr =0.558=12.4399mmMinimum thickness, equation (3) or (5),mmdmin =7.67dmin =13.92dmin = + CACalculated Minimum Thickness, min wall,mm13.92=12.9399mmAv. WallCold drawn tubes 0 +22%; hot finished tubes: 0 +28%28%mm15.86Pipes 12.5%mm15.90MAWP for a given thicknessSelected Wall Thickness,mm18.24MAWP =SE(T-CA-CAE)/[(D/2-CAE)-0.4(T-CA-CAE)]Calculation of equivalent tube metal temperature=4.46MPaDuration of operating period, yearstop =1Metal temperature, start of run,CTsor =635MAWP - Cold for a given thicknessMetal temperature, end of run,CTeor =690SA, el at Ambient Temp =137.9Temperature change during operating period,KT =55.0MAWP Cold =SAET/(D/2-CAE-0.4T]Metal absolute temperature, start of run,KT*sor =908.0=16.49MPaThickness change during operating period,mm =0.33Assumed initial thickness,mm0 =8Actual stress for given thicknessCorresponding initial stress, equation (1),MPapr/2*(Do/0-1)0 =58.1el actual =P(D/2-CAE-0.4(T-CA-CAE))/(E(T-CA-CAE))Material constant, Table 3,MPaA =1.23E+06=54.85MPaRupture exponent at Tsor1 FigE15n0 =4.8Temperature fraction, Figure 2,V =2.90N =0.20fT =0.62Hydrotest PressureEquivalent tube metal temperature, equation (6),CTeq =669.1UG - 99 (b) =1.3 times MAWP*SA/SOwner furnished data=20.27MPaUG - 99 (c) =1.3 times MAWP ColdChecks:=21.43MPa1Thin Tube: min/Do =0.083