INTERMEDIATE-TUBESHEET-CALCULATION.pdf

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INTERMEDIATE TUBESHEET CALCULATION

XXREV. N

XXDATE DATE

XXDESCRIZIONE DESCRIPTION

XXEMESSO ISSUED BY CONTROLLATO CONTROLLED BY APPROVATO APPROVED BY


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1. INTRODUCTION1.1 SCOPEScope of the work is the finite element analysis of Intermediate Tube Sheet (ITS) of convection section unit. A complete result element analysis has been developed to investigate the behaviour of tubesheet withstand gravity load, coils weight ad friction loads.

1.2

JOB REFERENCE AND DESIGN CODES

REFERENCE DOCUMENTATION 1. Drawings of Process Datasheet [document number: XX] 2. Drawings of ITS [dwg: XX / XX / XX] DESIGN CODE The design cod is API 560 IV Ed. Agu. 2007 chapter 10. The loads have been assumed according to API 560 Sect. 10.2 in particular tributary length shall be determined in accordance with results and procedures for supporting continuous beams on multiple support. Friction loads shall be based on a friction coefficient of 0.30. MATERIAL SPECIFICATION ITS material have been selected according to reference drawing. According to API 560 Sect. 10.2, the maximum allowable stresses at design temperature shall not exceed the following: 1. DEAD LOAD STRESS: 50% of the average stress required to produce 1% creep in 10000 h 2. DEAD LOAD + FRICTION STRESSES: of the average stress required to produce 1% creep in 10 000 h 3. For casting the allowable stress value shall be multiplied by 0.8 to determine the required casting thickness. The allowable stresses at temperature for the material given in Annex D of API 560 Code.

1.3

PERFORMANCE OF FEM ANALYSIS

In order to perform the Stress analysis of ITS, a FEM Analysis has been executed with the following proprieties: 1. Tetahedral solid elements have been for mesh of ITS 2. A Jacobian 4 point control has been executed 3. Solver Program: Advance Simulation Technology 4. Solver Type: ANSY SOLVER

MESH SETTINGS The mesh sizing and coarseness are specified by following parameters: 1. Average Size: specify the fraction of models longest axis between adjacent nodes. INTERMEDIATE TUBESHEET CALCULATION

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2. Max Turn Angle: specify the maximum angle for arcs 3. Create Curved Mesh Elements: select to create meshes whit curved edges and faces LOAD AND CONSTRAINT Suitable boundary conditions have been introduced at the interfaces with supports convection section (supports and guides exactly), to allow the real simulation of results. The constraint considered acting on the structure are the follows: 1. SUPPORT CONSTRAINT: surface blocked on the bottom of ITS 2. GUIDE CONSTRAINT: surface locked in the direction normal to the plane of ITS

Figure 1

Typical Support Constraint

Figure 2

Typical Guide Constraint


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The loads considered acting on the structure are the follows: 1. CASTING SELF WEIGHT; 2. COIL LOADS, vertical load applied on the lower point of each hole on the tubesheet web; 3. FRICTION LOADS, horizontal load applied on the lower point of each hole on the tubesheet web; From the above loads the following load conditions has been adopted: 1. CASTING (self weight of steelwork automatically calculated by the program itself. Material density has been assumed equal to r = 8800Kg/m^3 to take into account material added for foundry process as fillets and shrinkage); 2. VERTICAL LOADS (weight of tributary tube length and applied as concentrated loads in correspondence of the contact surface between tube and ITS of each hole on the tubesheet web); 3. FRICTION LOADS (friction action due to tube expanding and applied as concentrated loads in correspondence of the contact surface between tube and ITS of each hole on the tubesheet web); ACTION ON TUBE SHEET (Ats) in section LOAD CALCULATION is the intensity of the loads for each coil.

Figure 3

Typical Dead Load


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Figure 4

Typical Dead + Friction Load

FEM RESULTS The numerical model of structure has been full tree-dimension one, studied in the linear elastic range. The FEM Analysis plot the following results: 1. Von Mises Stresses: combination of loads in the main direction of inertia 2. Displacement: combination of displacement At the end of analysis compare the plot of Von Mises Stresses with the allowable dead load stresses (Sad) and allowable friction stresses (Saf).

2. SUMMARY RESULTSThe results, summarize below, are referred to the FEM Analysis.ALL. STRESS COIL XX Sa (Mpa) 3,61 Sad (Mpa) 2,89 DEAD LOADFEM Res. (Mpa)

2,53

Safety Factor 0,88

DEAD + FRICTION LOAD Saf Safety FEM Res. (Mpa) Factor (Mpa) 5,78 5,27 0,91


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3. INTERMEDIATE TUBE SHEETITS MECHANICAL CALCULATION COIL PROCESSCOIL PROCESS F.G. TEMPERATURE INLET F.G. TEMPERATURE OUTLET FLUID DENSITY XX PROCESS GAS 1065 C 980 C 50 kg/m3

TUBESHEET DESIGN DATATUBESHEET MATERIAL DESIGN TEMPERATURE ALLOWABLE STRESS DEAD LOAD STRESS FRICTION STRESS CORROSION ALLOWANCE type= T= Sa= Sad=(0,8*Sa) Saf=(2*Sad) Ca= 25Cr 35Ni Nb 1120 C 3,61 MPa 2,89 MPa 5,78 MPa 1,3 mm

WEIGHTS ACTING ON TUBE SHEETBARE TUBE DESIGN NUMBER OF ROWS PIPE PER ROWS NUMBER OF TUBES BARE TUBE O.D. BARE TUBE THICKNESS BARE TUBE LENGTH LINEAR WEIGHT OF BARE LINEAR WEIGHT OF BARE (12,5%) FINNED TUBES FINNED HEIGHT FINNED THICKNESS N FINNED LINEAR WEIGHT OF FINNED WEIGHT TUBE WEIGHT TUBES LINEAR WEIGHT OF FLUID WEIGHT FLUID ON TUBE WEIGHT FLUID WEIGHT BEND N BEND WEIGHT BENDS WEIGHT ITS (2 Pieces) TOTAL WEIGHTS type= Nr= Np= Nt=(Nr*Np) Dia= Th= Le= LwT= LwT0,12=(LwT*12,5%) (yes/no) Hfi= ThFi= NFi= LwFi= UWT=(Le*(LwT0,12+LwFi)) WT=(N*UWT) Lwf= UWF=(Le*Lwf) WF=(N*UWF) UWB= Nbe= WB=(UWB*Nbe) WITS= Tw=(WT+WF+WITS+WB) 3" SCH 160 4 15 60 88,9 mm 11,12 mm 7,32 m 21,3 kg/m 23,96 kg/m No 0 mm mm 0 0 n/m 0,00 kg/m 175,41 kg 10524,33 kg 0,17 kg/m 1,28 kg 76,60 kg 5.2 kg 45 234,00 kg 2100,00 kg 12934,93 Kg


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COIL GEOMETRICAL DATA

N TUBESHEET DISTANCE BETWEEN END SUPPORT DISTANCE BETWEEN INTERMEDIATE SUPPORT

Nts= L= L1=

2 7,32 2,44 m m

TUBESHEET GEOMETRICAL DATA

TUBESHEET LENGHT DIA HOLE DISTANCE ROW DISTANCE COLUMN DELTA COLUMN DISTANCDE EXTREME HOLE DISTANCE I HOLE DISTANCE LAST HOLE

ITSLe= DH= DsR= DsC= DelC=(DsC/2) DsHo=(Dsc*(Np-1)) DsIHo= DsLHo=

2970 102 128,8 161,2 80,6 2337,4 316,3 316,3

mm mm mm mm mm mm mm mm


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LOAD CALCULATIONTOTAL FORCE DISTRIBUTED LOAD TWF=(Tw*9,81) Dlo=(Tw/L) 126.892 17.335 N N/mFriction Load

Dead Load

REACTION ON END TUBESHEET 1 REACTION ON TUBESHEET 1 REACTION ON TUBESHEET 2 REACTION ON END TUBESHEET 2

ReaETS1=(L1*Dlo*4/10) ReaITS1=(L1*Dlo*11/10) ReaITS2=(L1*Dlo*11/10) ReaETS2=(L1*Dlo*4/10)

16.919 46.527 46.527 16.919

5.076 13.958 13.958 5.076

N N N N

Dead Load

Friction Load

LOAD ON TUBESHEET DISTRIBUTED LOAD ON ITS REACTION ON TUBESHEET MAX MOMENT IN L/2 MAX SHEAR IN I HOLE MOMENT IN I HOLE SHEAR IN II HOLE MOMENT IN II HOLE

LoTs= (MAX ReaITS) DloTs=(LoTs/DsHo) RTs=(LoTs/2) Mmax= Tmax= MIHo= TIIHo= MIIHo=

46.527 19,91 23.263 20.952 23.263 7.358 20.700 10.189

13.958 5,97 6.979 6.286 6.979 2.207 6.210 3.057

N N/mm N Nm N Nm N Nm


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STRESS CALCULATION

TUBESHEET DIMENSIONS TUBESHEET HEIGHT TUBESHEET WIDTH DISTANCE DISTANCE DISTANCE DISTANCE DISTANCE THICKNESS THICKNESS THICKNESS THICKNESS THICKNESS TUBESHEET THICKNESS RESISTANT AREA NEUTRAL AXIS INERTIA X INERTIA Y DEAD LOAD STRESS FRICTION STRESS STRESS RESULTS SIGMA DEAD LOAD SHEAR DEAD LOAD STRESS RESULTS DEAD LOAD RATIO

H=

B= a1=a2 = a3 = a4 = a5 = t1 = t2 = t3 = t4 = t5 = t6 = Ares = E=

L/2 551,4 400 17,5 151 279,8 408,6 539,9 35 28 0 0 23 22 7643 221 8,28E+06 2,29E+06 2,89 5,78

I HOLE 551,4 240 17,5 151 279,8 408,6 539,9 35 28 0 0 23 55 19107 250 6,19E+06 8,43E+05 MPa MPa

II HOLE 551,4 280 17,5 151 279,8 408,6 539,9 35 28 0 0 23 55 19107 246

mm mm mm mm mm mm mm mm mm mm mm mm mm mm2 mm

Wx = Wy = Sad= Saf=

6,94E+06 mm3 1,14E+06 mm3

sD= tD=sRD = sqrt(sD^2+3*tD^2)

2,53 0,00 2,53 0,88

1,12 1,22 2,39 0,83

1,39 1,08 2,34 0,81

MPa MPa MPa

sRD / Sad


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PASSED DEAD LOAD SIGMA FRICTION LOAD SHEAR FRICTION LOAD STRESS RESULTS FRICTION LOAD RATIO PASSED DEAD + FRICTION LOAD

OK 2,54 0,00 5,67 0,86 OK

OK 2,54 0,47 5,81 0,89 OK

OK 2,53 0,42 5,72 0,87 OK MPa MPa MPa

sRF / Saf RATIO < 1

STRESS ANALYSIS CALCULATIONLOAD CONDITIONVERTICAL LOAD (y direction) FRICTION LOAD (z direction) GRAVITY LOAD (mass proprieties) 46.527 13.958 1040 Mesh of solid elements 0.01 30 Selected High 146124 252820 740 mm3 N N kg

MESH INFOTYPE OF MESH AVARAGE SIZE MAX TURN ANGLE CREATED CURVED MESH ELEMENTS MESH QUALITY ELEMENTS N NODES N ELEMETS MEDIUM VOLUME

STRESS ANALYSIS RESULTS dead loadThe results, summarize below, are referred to dead load combination, according to per API 560. 1. Max Von Mises value: 2,53 MPa 2. Max Displacement value: 0.073 mm The figure show than the Von Mises stresses are less of allowable ones.


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Figure 5

Dead Load Analysis: Von Mises Stress

Figure 6

Dead Load Analysis: Von Mises Stress at tubesheet web

Figure 7

Dead Load Analysis: Von Mises Stress at tubesheet top


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Figure 8

Dead Load Analysis: Displacement

STRESS ANALYSIS RESULTS dead + friction loadThe results, summarize below, are referred to dead plus friction load combinations, according to per API 560. 1. Max Von Mises value: 5,27 MPa 2. Max Displacement value: 0.117 mm The figure show than the Von Mises stresses are less of allowable ones.

Figure 9

Dead+Friction Load Analysis : Von Mises Stress


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Figure 10

Dead+ Friction Load Analysis: Von Mises Stress at tubesheet web

Figure 11

Dead+ Friction Load Analysis: Von Mises Stress at tubesheet top

Figure 12

Dead + Friction Load Analysis: Displacement


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CHECK WITH MATERIAL ALLOWABLE STRESSESDEAD LOAD CONDITION Corrected all. Stress for Casting factor (Sad) : 2,89 MPa Evaluated Stress by FEM (SaFEM): 2,53 MPa Safety factor (SaFEM / Sad)= 0.88 Dead load analysis shows that the critical areas are reduced at the bottom of the plate. The critical areas within the limits of tolerance. The complete finite element analysis performed shows that the stress levels are within the allowable ones. ITS is verified. FRICTION + DEAD LOAD CONDITION Corrected all. Stress for Casting factor (Saf) : 5,78 MPa Evaluated Stress by FEM (SaFEM): 5,27 MPa Safety factor (SaFEM / Saf)= 0.91 Dead plus friction load analysis shows that the critical areas are reduced at the bottom and the top of the plate. The critical areas within the limits of tolerance. The complete finite element analysis performed shows that the stress levels are within the allowable ones. ITS is verified.


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4. SUPPORT MECHANICAL CALCULATIONScope of this section is the mechanical dimension of support for ITS and relative bolts. The figure show the geometric parameters for mechanical dimension.

Figure 13

Support geometrical scheme

ITS SUPPORT SUPPORT CHECKSUPPORT MATERIAL DESIGN TEMPERATURE ALLOWABLE STRESS DEAD LOAD STRESS SUPPORT DIMENSIONS SUPPORT HEIGHT SUPPORT WIDTH SUPPORT HEIGHT DISTANCE DISTANCE DISTANCE THICKNESS THICKNESS THICKNESS RESISTANT AREA NEUTRAL AXIS INERTIA X type= T= Sa = Sad = (Sa*0,8) 25Cr 35Ni Nb 1035 C 7,15 MPa 5,72 MPa

h1 =

B= h2 = a1=a2 =

a3 =t1 = t2 = t3 = Ares = E=

290 320 100 145 310 380 40 40 30 13200 261 1,38E+06

mm mm mm mm mm mm mm mm mm mm2 mm mm3

Wx =


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SUPPORT LOAD LOAD ARM MOMENT REACTION STRESS RESULTS NORMAL STRESS SHEAR STRESS STRESS RESULTS RATIO PASSED

SuL=(RTs*1,3) d= MR=(SuL*d)

30243 126 3810557

N mm Nmm

sN= tT= sR=sqrt( sN^2+3*tT^2) sR / Sad RATIO < 1

2,76 2,29 4,84 0,85 OK

MPa MPa MPa

BOLT CHECKBOLT SIZE BOLTS TYPE BOLTS NUMBER SECTION AREA DESIGN TEMPERATURE ALLOWABLE STRESS BOLT DISTANCE ACTION ON ONE BOLT MOMENT REACTION NORMAL FORCE ON ONE BOLT STRESS RESULTS NORMALE STRESS SHEAR STRESS STRESS RESULTS RATIO PASSED ACTION ON ONE BOLT MOMENT REACTION NORMAL FORCE ON ONE BOLT STRESS RESULTS NORMALE STRESS SHEAR STRESS STRESS RESULTS RATIO PASSED sN= tT= sR=sqrt( sN^2+3*tT^2) sR / Sa RATIO < 1 17,97 20,67 40,06 0,52 OK MPa MPa MPa sN= tT= sR=sqrt( sN^2+3*tT^2) sR / Sa RATIO < 1 ACBo=(SuL/NBo) MR = Fa = (MOBo/Db) 10730 5407846 9324 11,12 14,57 27,58 0,36 OK N Nmm N MPa MPa MPa M= 30 type= ASTM SA193 B8M Cl. 1 NBo= 4 Ax= 519 mm2 T= 538 C Sa= 77 MPa dB= 330 mm ACBo=(SuL/NBo) 7561 N MR = 3810557 Nmm Fa = (MOBo/Db) 5774 N


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5. GUIDE MECHANICAL CALCULATIONScope of this section is the mechanical dimension of guide for ITS and relative bolts. The figure show the geometric parameters for mechanical dimension.

Figure 14

Guide geometrical scheme

ITS GUIDE GUIDE CHECKSUPPORT MATERIAL DESIGN TEMPERATURE ALLOWABLE STRESS DEAD LOAD STRESS SUPPORT DIMENSIONS GUIDE HEIGHT GUIDE HEIGHT DISTANCE DISTANCE THICKNESS THICKNESS RESISTANT AREA NEUTRAL AXIS INERTIA X type= T= Sa = Saf = (Sa*0,8*2) 25Cr 35Ni Nb 1120 C 3,61 MPa 5,78 MPa

h1 =

h2 = a1=a2 = t1 = t2 = Ares = E=

90 95 45 105 35 30 4200 74 1,13E+05

mm mm mm mm mm mm mm2 mm mm3

Wy =


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SUPPORT LOAD LOAD ARM MOMENT REACTION STRESS RESULTS NORMAL STRESS SHEAR STRESS STRESS RESULTS RATIO PASSED

GuL=(SuL *0,3/ 2) d= MR=(GuL*d)

4536 126 571584

N mm Nmm

sN= tT= sR=sqrt( sN^2+3*tT^2) sR / Saf RATIO < 1

5,04 1,08 5,38 0,93 OK

MPa MPa MPa

BOLT CHECKBOLT SIZE BOLTS TYPE BOLTS NUMBER SECTION AREA DESIGN TEMPERATURE ALLOWABLE STRESS BOLT DISTANCE ACTION ON ONE BOLT MOMENT REACTION NORMAL FORCE ON ONE BOLT STRESS RESULTS NORMALE STRESS SHEAR STRESS STRESS RESULTS RATIO PASSED sN= tT= sR=sqrt( sN^2+3*tT^2) sR / Sa RATIO < 1 4,41 7,00 12,90 0,17 OK MPa MPa MPa M= 24 type= ASTM SA193 B8M Cl. 1 NBo= 2 Ax= 324 mm2 T= 538 C Sa= 77 MPa dB= 200 mm2 ACBo=(GuL/Nbo) 2268 N MR = 571584 Nmm Fa = (MOBo/Db) 1429 N


INTERMEDIATE-TUBESHEET-CALCULATION.pdf

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