08 - Mechanical Design - Pressure Containment Part1

Shawn Kenny, Ph.D., P.Eng.Assistant ProfessorFaculty of Engineering and Applied ScienceMemorial University of [email protected]

ENGI 8673 Subsea Pipeline Engineering

Lecture 08: Mechanical Design – Pressure Containment: Part 1

2 ENGI 8673 Subsea Pipeline Engineering – Lecture 08© 2008 S. Kenny, Ph.D., P.Eng.

Lecture 08 Objective

To examine pressure containment requirements for mechanical design


Pi

Pe

Pressure Containment Parameters

Pipeline Section ResponseInternal Pressure, Pi

External Pressure, Pe

Nominal Internal Diameter, Di

Nominal External Diameter, De

Nominal Wall Thickness, t


Wall Tension

Pipeline ExampleD = 1.0m, Pi = 10MPa and Pe = 0MPa1,000 tonnes wall force

Pi

PeσH σH

Pi

Pe


Hoop Stress

Free Body Diagram

Thin Wall TheoryMean circumferential stressUniform wall stressTangential stress constantValid for D/t ≥ 20t ≤ 0.10 inner pipe radius

Pi

Pe

σH σH

Pi

Pe

2 0h i i e ot p D p Dσ − + =


Hoop Stress (cont.)Code Requirements

General• External pressure credit• Product type, density• Elevation profile, water depth• Pressure reference

Design factors• No specific technical argument• Historical use• Simple, conservative• Code inertia

Design factors and parameter variation• Safety and cost implication• Wall thickness

Nominal versus minimumFabrication toleranceCorrosion allowance

• DiameterNominal, outside, internal

2i o

h SMYSp D

tσ φ σ= ≤

Pi

Pe

2i i e o

h SMYSp D p D

tσ φ σ

−= ≤


Pressure ContainmentDNV OS-F101

Section 5 D200• plx ≡

pli during operation or plt during system test (Sec.3 B300 and Sec.4 B200)

• pb ≡

pressure containment resistance (Sec.5 D203, Eqn.5.8)

• t1 ≡

characteristic wall thickness (Sec.5 C202, Table 5-2)

• γm ≡

material resistance factor (Sec.5 C205, Table 5-4)

• γSC ≡

safety class resistance factor (Sec.5 C206, Table 5-5)

( )1blx e

m sc

p tp p

γ γ− ≤


Pressure Containment (cont.)Design Process

Safety class• Sec.2 C200, C300 and C400

Partial factors• γinc ≡

Sec.3 B304• γm ≡

Sec.5 C205 Table 5-4• γSC ≡

Sec.5 C206 Table 5-5• αU ≡

Sec.5 C206 Table 5-5Loads (Demand)• Local pressure (Sec.4 B202; Sec.5 B203 & D203)

Resistance (Capacity)• Wall thickness tolerance (Sec.7 G307 Table 7-18)• Material derating (Sec.5 C300 Figure 2)

( )1blx e

m sc

p tp p

γ γ− ≤


Pressure Containment (cont.)

Safety ClassSec.2 C200



Safety Class(cont.)

Sec.2 C300



Safety Class(cont.)

Sec.2 C300



Safety Class(cont.)

Sec.2 C403



Partial FactorsIncidental to design pressure • Sec.3 B300• Pressure control and pressure safety systems



Partial Factors(cont.)

Material resistance• Sec.5 C205

Table 5-4Safety class• Sec.5 C206

Table 5-5



Partial Factors (cont.)Material strength• Sec.5 C306 Table 5-6



LoadsPressure definitions• Sec.4 B200



Loads (cont.)Local Incidental Pressure• Operations, pli

• System test, plt



Loads (cont.)Local incidental pressure



ResistanceSec.7 G307 Table 7-18



Resistance (cont.)Derating• Sec.5 C300

Figure 2


Pressure Containment (cont.)Pressure Containment Resistance, pb

Sec.5 D203

Wall thickness• Sec.5 C202• Sec.5 D203• Sec.6 D203

Diameter• D ≡

nominal outside diameter Sec.1 D200

( ) 2 23b cb

tp t fD t

=−

( )1blx e

m sc

p tp p

γ γ− ≤


Engineering Design T. Zimmerman, C-FERPRCI R&D Forum April 2003


Probabilistic Basis

LoadDemand

ResistanceCapacity

Target SafetyLevels


DNV OS-F101 LRFD Format

Risk Basis for Design

Sec.2 C100-500


DNV OS F101 ⇔ Traditional Codes

LRFD versus Working StressSec.13 E400


Example 8-01

Calculate the minimum wall thickness to meet pressure containment requirements using DBNV OS-F101 (2007) for a subsea oil pipeline beyond the 500m platform excursion limit.


Example 8-01 (cont.)

Pipeline System ParametersPIPELINE SYSTEM PARAMETERS

Nominal Outside Diameter Do 324mm:=

Initial Selection Nominal Wall Thickness (Sec.5 C203 Table 5-3) tnom 15.9mm:=

Fabrication Process (Sec.7 B300 Table 7-1) [SMLS, HFW, SAW] FAB "SAW":=

Corrosion Allowance (Sec.6 D203) tcorr 3mm:=

Elastic Modulus E 205GPa:=

Specified Minimum Yield Stress (Sec.7 B300 Table 7-5) SMYS 450MPa:=

Speciifed Minimum Tensile Stress (Sec.7 B300 Table 7-5) SMTS 535MPa:=

Coefficient of Thermal Expansion αT 1.15 10 5−⋅ C 1−

:=

Poisson's Ratio ν 0.3:=

Pipeline Route Length Lp 0.75km:=

Linepipe Density ρs 7850kg m 3−⋅:=

Concrete Coating Thickness tc 50mm:=

Concrete Coating Density ρc 3050kg m 3−⋅:=



Operational Parametersg tc 50mm:=

Concrete Coating Density ρc 3050kg m 3−⋅:=

OPERATATIONAL PARAMETERS

API Gravity API 30:=

Product Contents Density

ρcont 1000 kg⋅ m 3−⋅141.5

131.5 API+⋅:= ρcont 876.2m 3.0− kg⋅=

Design Pressure (Gauge) Pd 12MPa:=

Safety Class (Sec.2 C200-C400) [L, M, H] SC "M":=

Design Pressure Reference Level href 10m:=

Temperature Differential ΔT 75 C⋅:=

Maximum Water Depth hl 120− m:=

Seawater Density ρw 1025kg m 3−⋅:=

Hydrotest Fluid Density ρt 1025kg m 3−⋅:=



DNV OS F101 Partial FactorsDNV OS-F101 PARTIAL FACTORS

System Operations Incidental/Design Pressure Factor (Sec 3B 304) γinc_o 1.10:=

System Test Incidental/Design Pressure Factor (Sec 3B 304) γinc_t 1.00:=

Material Resistance Factor (Sec.5 C205 Table 5-4) γm 1.15:=

Safety Class Resistance Factor (Sec.5 C206 Table 5-5) γSC 1.138:=

Material Strength Factor (Sec.5 C306 Table 5-6) αU 0.96:=



DNV OS F101 Wall Thickness ToleranceWALL THICKNESS FABRICATION TOLERANCE (SEC.7 G307 TABLE 7-18)

tfab 0.5mm FAB "SMLS" tnom 4mm≤∧if

0.125 tnom⋅ FAB "SMLS" tnom 4mm>∧if

0.125 tnom⋅ FAB "SMLS" tnom 10mm≥∧if

0.100 tnom⋅ FAB "SMLS" tnom 25mm≥∧if

3mm FAB "SMLS" tnom 30mm≥∧if

0.4mm FAB "HFW" tnom 6mm≤∧if

0.7mm FAB "HFW" tnom 6mm>∧if

1.0mm FAB "HFW" tnom 15mm>∧if

0.5mm FAB "SAW" tnom 6mm≤∧if

0.7mm FAB "SAW" tnom 6mm>∧if



:= tfab 1.000mm=



DNV OS F101 Material DeratingMATERIAL DERATING (SEC.5 C300 FIGURE 2)

ΔSMYS ΔT 50 C⋅−( )30MPa50 C⋅

⎛⎜⎝

⎞⎟⎠

⋅⎡⎢⎣

⎤⎥⎦

50 C⋅ ΔT< 100C<if

30MPa ΔT 100 C⋅−( )40MPa100 C⋅

⎛⎜⎝

⎞⎟⎠

⋅+⎡⎢⎣

⎤⎥⎦

otherwise

:= ΔSMYS 15.00 MPa⋅=

ΔSMTS ΔT 50 C⋅−( )30MPa50 C⋅

⎛⎜⎝

⎞⎟⎠

⋅⎡⎢⎣

⎤⎥⎦

50 C⋅ ΔT< 100C<if

30MPa ΔT 100 C⋅−( )40MPa100 C⋅

⎛⎜⎝

⎞⎟⎠

⋅+⎡⎢⎣

⎤⎥⎦

otherwise

:= ΔSMTS 15.00 MPa⋅=

fy SMYS ΔSMYS−( ) αU⋅:= fy 418 MPa⋅=

fu SMTS ΔSMTS−( ) αU⋅:= fu 499 MPa⋅=



Engineering AnalysisPRESSURE CONTAINMENT (Sec.5 D200)

Local Incidental Pressure During Operations (Sec.4 B202; Sec.5 D203)

Pli γ inc_o Pd⋅ ρcont g⋅ href hl−( )⋅+:= Pli 14.32 MPa⋅=

Local Incidental Pressure System Test (Sec.4 B202; Sec.5 B203 & D203)

Plt γ inc_t Pd⋅ ρt g⋅ href hl−( )⋅+ γ inc_t Pd⋅ ρt g⋅ href hl−( )⋅+ Pli≥if

1.03 Pli⋅ SC "L"if

1.05 Pli⋅ SC "M"if

1.05 Pli⋅ SC "H"if

:= Plt 15.03 MPa⋅=

External Hydrostatic Pressure

Pe ρw g⋅ hl⋅:= Pe 1.21 MPa⋅=



Engineering Analysis (cont.)Characteristic Yield Resistance (Sec.5 D203)

fcb min fyfu

1.15,

⎛⎜⎝

⎞⎟⎠

:= fcb 417.60 MPa⋅=

Wall Thickness Requirement - Operations (Sec.5 D202 Eqn.5.7)

t1_oDo

12

γ SC γ m⋅ Pli Pe−( )⋅

2

3⋅ fcb⋅+

:= t1_o 5.66 mm⋅=

Minimum Wall Thickness -Operations (Sec.5 C202 Table 5-2)

tmin_o t1_o tfab+ tcorr+:= tmin_o 9.66 mm⋅=

Wall Thickness Requirement - System Test (Sec.5 D202 Eqn.5.7)

t1_tDo

12

γ SC γ m⋅ Plt Pe−( )⋅

2

3⋅ fcb⋅+

:= t1_t 5.97 mm⋅=



Engineering Analysis (cont.)

Minimum Wall Thickness - System Test (Sec.5 C202 Table 5-2)

tmin_t t1_o tfab+:= tmin_t 6.66 mm⋅=

Minimum Wall Thickness Requirement for Pressure Containment

tmin max tmin_o tmin_t, ( ):= tmin 9.66 mm⋅=

Wall Thickness Check

tmin_chk "WALL THICKNESS OK" tnom tmin>if

"INCREASE WALL THICKNESS" otherwise

:= tmin_chk "WALL THICKNESS OK"=


Reading List

Section 5 – DNV (2007). Submarine Pipeline Systems. Offshore Standard, DNV OS-F101, October 2007, 240p.


References

DNV (2007). Submarine Pipeline Systems. Offshore Standard, DNV OS-F101, October 2007, 240p.

Documents

08 - Mechanical Design - Pressure Containment Part1