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“ STRESS ANALISIS PADA SISTEM PERPIPAAN DENGAN PROGRAM CAESAR II”
Pustandyo Widodo
KENAPA KITA PERLU MELAKUKAN ANALISIS TEGANAGAN PIPA ?
Mencegah terjadinya kegagalan pipa / support akibat overstress atau fatique Untuk menjaga agar tegangan di dalam pipa dan fitting memenuhi code yang diijinkan. Untuk menjaga beban pada peralatan yang dipasang memenuhi code yg diijinkan dari pabrik atau sesuai dg standar (spt API 661, API 650 dll) Untuk menghitung design beban/load untuk support dan restraints Untuk menentukan piping displacement. Untuk memecahkan permasalahan dinamik di dalam memasang pipa, yaitu.: mechanical and acoustic vibration , transient flow and relief valve discharge Untuk mengoptimalkan desain perpipaan. Untuk mencegah kebocoran pada flange joint / sambungan pipa.
Design of Piping Typically piping is categorised:
Hot system , design temp. > 1500F (660C) Cold system, design temp. < 1500F (660C)
Piping loads: Sustained Load, seperti pressure, weight/berat. Expansion Load, seperti thermal expansion, diff. anchor
displacement. Occasional Load, seperti. wind, earthquake
The stresses on the piping: Normal stresses: longitudinal stress, hoop stress, radial
stress Shear stresses, berkaitan dg shear load and torsion.
+ +
+ +loop
+ +Expansion joint
+ +
DESIGN SISTEM PERPIPAAN MEMPERTIMBANGKAN FLEKSIBILITAS
Method of Analysis:1. Category 3
Using computer program such as: Caesar II (Coade), Autopipe (Bentley), PIPANL-3 (SSD) etc.
2. Category 4Using approximate methods such as: the Kellogg, Grinnell or Tube Turn methods.
3. Category 5Visual inspection with or without the aid of guided cantilever chart or similar short cut methods.
Ref: KBR Design Manual Subject No: 4100
Pipe Stress Analysis Category
Where:
σ = Stress (kg/cm2)
ε = Strain
E = Young’s Modulus (kg/cm2) Allowable stress is the yield strength divided by safety factor.
I.E : Carbon Steel Pipe below creep range commonly has allowable stress is 2/3* σy or ¼* σu. For detail see Table A-1 in B31.3
E x ε σ
Tegangan akibat gaya axial σ = F / A
F = Axial force acting on cross section (kg)A = Cross-sectional of pipe (mm2)
Tegangan akibat bending & Torsi σb = Mb / Zσt = Mt / 2ZMb = Bending moment (kg-mm)Mt = Torsional moment (kg-mm)Z = Section modulus of pipe (mm3)
Tegangan akibat tekanan internal σH = PDi / 2t (Hoop)
σL = PDi / 4t (Longitudinal)P = Design pressure (kg/mm2)Di = Inner diameter (mm)t = Thickness of pipe (mm)
FF
Mt
Mb
σL σH P
Ekspansi Thermal δ = ΔT x α x L ; (mm) Carbon Steel +/- 1 mm/m for 100oC Stainless Steel +/- 1.35 mm/m for 100oC
Tegangan Thermal σ = ε x Ε = δ/L x E = ΔT x α x E
Reaction ForceF = σ x A
Example: 1meter length of 8” NPS CS Pipe STD at 100oC.
T ambient = 20oC1. δ = (100-20)x12x10-6x1000 = 0.96 mm2. σ = (100-20)x12x10-6x20000 = 19.2 kg/mm2
3. F = 19.2 x π x (2192-2032)/4 = 27.6 ton
δ (Pushed)
Force
Piping Design Code ASME B31.1 Power Piping ASME B31.3 Process Piping ASME B31.4 Pipeline
(Hydrocarbon) ASME B31.8 Pipeline (Gas) ASME Section III Nuclear
Component Design
ASME: The American Society of Mechanical Engineers
API: American Petroleum Institute
NEMA: National Electrical Manufacturers Association
WRC: Welding Research Council
Related Code for Nozzle Evaluation
API Std 610 Centrifugal Pump API Std 611 Steam Turbines API Std 617 Centrifugal
Compressor API Std 618 Reciprocating
Compressor API Std 650 Welded Steel Tanks API Std 560 Fired Heaters
(Furnace) API STD 661 Air-Cooled Heat
Exchangers (AFC) NEMA SM23 Steam Turbines ASME SEC VIII Pressure Vessel WRC 107, WRC 297 Local Stress
on Nozzles
7.2. Code Stress Equations
• 7.2.1. B31.1 Power Piping 7.2.2. B31.3 Process Piping
HoA
sus St
PdZiM.S
4750
)25.125.1( SUSHCAC
EXP SSSfSZ
iMS
HoBA
OCC kSt
PdZiM
ZiMS
475.075.0
Where:MA = Resultant moment due to sustained, kg-mm
SH = Allowable stress at operating temperature, kg/mm2
i = Intensification factor
Mc = Resultant moment due to expansion, kg-mm
SA = Allowable expansion stress, kg/mm2
MB = Resultant moment due to occasional, kg-mm
k = occasional factor
= 1.2 for loads occurring less than 1% of the time
= 1.15 for loads occurring less than 10% of the time
SC = Allowable stress at installation temperature, kg/mm2
Hoooii
m
axsus S
tPd
ZMiMi
AFS
4])()[( 2/122
)25.125.1(]4)()[( 2/122*
2*
SUSHCATooii
EXP SSSfSZ
MMiMiS
HlSUSOCC SSSS 33.1
Where:Fax= Axial force due to sustained, kg
Mi = In-plane bending moment due to sustained, kg-mmMo = Out-plane bending moment due to sustained, kg-mm Mi* = Range of in-plane bending moment due to expansion, kg-mmMo* = Range of out-plane bending moment due to expansion, kg-mmSH = Allowable stress at operating temperature, kg/mm2
ii ,io = In-plane, out-plane intensification factorMT = Torsional moment due to expansion, kg-mmSA = Allowable expansion stress, kg/mm2
SC = Allowable stress at installation temperature, kg/mm2
Sl = Bending stress due to occasional loads such as wind/earthquake f = Stress range reduction factor
7.2.3. B31.4 Liquid Transportation Piping
Yieldblpsus x S. x .SSS 720750
YieldtbEXP SSSS 72.0)4( 2/122*
YieldSUSEXPHOPE SFSSSvTEaFS 9.0)1(
YieldblpOCC x k x S. x .SSS 720750**
Where:Slp = Longitudinal pressure stress, kg/mm2
Sb = Bending stress due to sustained, kg/mm2
Sb* = Range of bending stress due to expansion, kg/mm2
St = Range of torsional stress due to expansion, kg/mm2
Sb** = Bending stress due occasional, kg/mm2
Syield = Specified minimum yield stress material, kg/mm2
F = 1 (under ground pipeline); 0 (above ground pipeline)
E = Modulus of Elasticity
a = Thermal expansion coefficient
ΔT = Temperature change of pipe from ambient
v = Poisson’s ratio
SH = Hoop stress kg/mm2
k = Occasional load factor
7.2.4. B31.8 Gas Transportation Piping
T S x F x .SSS blpsus 750
SSSS tbEXP 72.0)4( 2/122*
SSSS SUSEXPOPE
x T x k x S x F.SSS b**lpOCC 750
Where:Slp = Longitudinal pressure stress, kg/mm2
Sb = Bending stress due to sustained, kg/mm2
Sb* = Range of bending stress due to expansion, kg/mm2
St = Range of torsional stress due to expansion, kg/mm2
Sb** = Bending stress due occasional, kg/mm2
S = Specified minimum yield stress material, kg/mm2
F = Construction type
T = Temperature derating factor
k = Occasional load factor
Kriteria Analisis Tegangan 350
300
250
200
150
100
oC
3 4 6 8 10 12 14
Detail calculation required
B
NPS
300
250
200
150
100
80
oC
2 3 4 6 8 10 1412
Calculation not required
Detail calculation required
2 3 4 6 8 10 1412
Calculation not required
Class 600 and higher
Detail calculation required
NPS NPS
Kriteria Desain Support
Anchor
PadShoe
Spring Hanger Assembly
Eye Bolt
Spring HangerTurnbuckle
Pipe Clamp
Structure
Adjustable Support
Tiga macam hanger yg biasa digunakan adlh : Rigid support atau rod hanger yang harus dapat menahan setiap
gerakkan sepanjang sumbu hanger. Variabel support atau spring hanger menyediakan gaya support
yang sama dengan hot load dan memungkinkan defleksi. Constant support atau constant effort hangers yang menyediakan
gaya konstan saat terjadinya siklus termal. Idealnya support hanger yang konstan tidak akan meregang saat gerakkan bebas dari system dan tidak akan menimbulkan tegangan pada pipa.
Support Around Control Valve
Control ValveSliding SupportTight Support
Variable Spring Support Adjustable Guide
Spring and Adjustable Support
Stress Analysis using Caesar II
K-3301A
K-3301B
K-3301C
V-1001
V-1002
Spring Hanger (Typ. 12ea)
Spring Support
Vertical Guide
Trunnion (Typ. 3ea)
Guide (Typ. 3ea)
Required Data:
• Piping Configuration complete with dimension.
• Material Spec. :Size, Thickness, Material Properties, method of bracing, etc.
• LDT (Line Designation Table): Pressure, Temperature, Insulation Thickness, Density etc.
• Equipment Drawing to determine nozzle movement.
• Wind and earthquake loading.
• Standard valve and flange weight.
• Number of operating cycles if any.
• Misc. item drawing such as silencer etc.
Item need to be concerned:
• Boundary Condition.
• Operating Case, i.e: pump, run or stand-by.
• Friction.
PENGGUNAAN PROGRAM CAESAR II
START
DATA :1. Sistem Proses 2. Gb P & ID 3. Gb Isometric 4. Dok.Kontrak 5. Pipeline List
INPUT / EDIT DATA
PROSES & ANALISIS DG CAESAR II :-Analisis beban, Displacemen, Stress
KRITERIAPENERIMA
AN
Sesuai
Tdk Sesuai
PROSES ULANG *
VALIDASI
SELESAI
PIPING INPUT DENGAN PROGRAM CAESAR II
Restraint Summary Static Output
Displacement Static Output
Stress Static Output
PRAKTIKUM DG CAESAR II
LIHAT FILE PRAKTIKUM
