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TECHNICAL REPORT

Document No. 859 063351

Project PROVIDENCIA

Author (s) Stoll V

Date 21/07/2011

Via Daniele Manin, 16/18

I-36015 Schio (VI) Italia

Title

Calculation Report Bifurcation

Summary

The present report on the structural analysis of the inlet bifurcation of PROVIDENCIA shows that its

design fulfils all requirements according to the standard ASME B.P.V.C. VIII-2 AD, Appendix 4, Article

4.1 e Appendix 5, Article 5.1 applying the Design Pressure pk = pnom +30% = 0,5898 [MPa], theNominal Pressure pnom = 0,4537 [MPa] amd the Test Pressure pT = pk +50% = 0,8847 [MPa]. The

Nominal Pressure is determined by the Static Head (51 m) and the difference of Centerlines of Turbine

(250,64 masl) and Biforcation (256,50 masl). The following table summarizes the results obtained:

Stress Range Eff. Value Allow. Limit Approval

Primary General Membrane, pk 63 [MPa] 163,3 [MPa] OK

Primary General Membrane, pT 95 [MPa] 310,5 [MPa] OK

Primary Local Membrane, pk 72 [MPa] 245,0 [MPa] OK

Primary Bending, pk 146 [MPa] 245,0 [MPa] OK

Primary Membrane + Bending, pk 72 [MPa] 163,3 [MPa] OK

Primary Local + Secondary, pk 104 [MPa] 490,0 [MPa] OK

Max. Total Primary Stress, pT 224 [MPa] 490,0 [MPa] OK

Cumulative Usage Factor (fatigue) 0,025 1 OK

Copy to: CompleteReport

Page. 1only

Copy to: CompleteReport

Page.1 only Author::

Stoll/V

Verified by:

Cristian Vanzin

HIDRO PROVIDENCIA SA

ANDRITZ Hydro Srl.

2

1

Proj. Manager (F. Trentin)

Tech.Proj.Man. (E. Zordan)

1

1

Approved by:

G. Pasqualotto

Relative report(s): Number of pages, incl. header: 18

Calculation File(s):Associated Drawing n

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Content

1. CALCULATION DATA ...............................................................................3

1.1MATERIALS .................................................................................................................. 3

1.2LOADSDEFINITION OF LOAD CASES ............................................................................ 3

2. MODELLING..............................................................................................4

2.1GEOMETRY AND MESH.................................................................................................. 4

2.2LOADS AND CONSTRAINS .............................................................................................. 5

3. CRITERIA ..................................................................................................7

3.1CRITERIA FOR THE STATICANALYSIS ............................................................................. 7

3.2DEFINITION OF THEADMISSIBLE LIMITS........................................................................... 8

3.2.1 Limiting Stress Sm ........................................................................................................8

3.2.2 Limiting Stress Sps........................................................................................................8

3.2.3 Limiting Stress Exceptional..........................................................................................8

3.3CRITERIA FOR THE LIFE STRESSANALYSIS ..................................................................... 9

4. RESULTS ................................................................................................10

4.1LOCALIZING OF STRESS ZONES ................................................................................... 10

4.2LOAD CASE #1:DESIGN PRESSURE PK ........................................................................ 10

4.2.1 Primary General Membrane............................................................................................10

4.2.2 Primary Local Membrane ................................................................................................11

4.2.3 Primary Bending..............................................................................................................12

4.2.4 Primary Combined (Membrane & Bending) ....................................................................12

4.2.5 Secondary Combined (Secondary Membrane & Bending) .............................................13

4.2.6 Deformation.....................................................................................................................14

4.2.7 Conclusion.......................................................................................................................15

4.3LOAD CASE #2:NOMINAL PRESSURE PNOM ................................................................... 16

4.4LOAD CASE #3:TEST PRESSURE PT ............................................................................ 16

4.5.LOAD CASE #4:LIFE STRESSANALYSIS ...................................................................... 18

5. CONCLUSION.........................................................................................18


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1. Calculation Data

1.1 Materials

The bifurcation is realized in steel plates S355J2G3 EN 10025Note with its mechanical properties

depending on the size of steel plates as indicated in the following table:

Thickness s

[mm]

Tensile Strength

RmMPa]

Min. Tensile

Strength Rm[MPa]

Applicable

parts

Effective Thickness

of parts [mm]

Tensile

Strength

3 < s100 490 630 490 All 10 - 30

Table 1.1.1

Thickness s

[mm]

Min. Yield

Strength Rs[MPa]Applicable parts

Effective Thickness

of parts [mm]

10 < s16 355 Pipe Downstream 10

10 < s16 355 Pipe Upstream 12

10 < s16 355 Steel Cones 15

Yield

Strength

16 < s40 345 Rib (Scythe) 30

Table 1.1.2

The general properties of carbon steel used for the FE- analysis:

- youngs modulus E = 210.000 [MPa]

- poisons ration = 0,3

- density = 7.850 [kg/m3]

1.2 Loads Defin ition of Load Cases

The following load cases are considered for the analysis based on the standards of Andritz Hydro for

operation of hydraulic turbines:Type of

Application

Load

Case

Type of

caseCondition Description Applied Loads

Intern. Pressure pkPressure at level 256,50 masl

pk= 1,3 x pnom= 0,5898 [MPa]1 Normal Design

Pressure LoadPartial Load* on outlet pipe

60% x Aoutx pk= 1350 [kN]

Intern. Pressure

pnom

Nominal Pressure at level 256,50 masl:

pnom=0,4537[MPa] @ Qmax= 14 [m3/s]

2 Normal Nominal

Pressure LoadPartial Load* on outlet pipe

60% x Aoutx pnom= 1030 [kN]

Static

3 Exceptional Test Test Pressure pTTest Pressure

pT= 1.5*pk= 0,8847 [MPa]

Life Stress

Analysis4 Normal Fatigue

Cycles of pressure

fluctuation

Conventional Life Cycle of 50 years with

500 start-ups per year (from p=0 to pnom)

of which 8000 cycles are considered to

water hammer (pk)

Table 1.2.1

As defined in the above table for the fatigue analysis considers a complete pressure rise and a

depressure to zero for each start-up and stop, which is a conservative approach. Further one third of

the cycles are considered to be under the condition of water hammer. For the load this is a cycle form

p=0 to pnom, and additionally a cycle from pnom to pk.

Nota 1EN 10025: Hot-Rolled Products of Non-Alloyed Structural Steels International Conformity


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2. Modelling

2.1 Geometry and Mesh

The latest manufacturing drawing (dwg. no. 859055104) is the basis of the calculation models. The 3-D

models for the calculation are created in UNIGRAPHICS. For simplification the welds have beenmodelled as part of the sheet metal as they look like after manufacturing. For meshing, calculation and

evaluation of the results the finite element program ANSYS 12.1 was used. The mesh consists of

quadratic tetrahedron with 10 nodes. In total there are 489211 nodes & 254786 elements.

Figure 2.1.1


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2.2 Loads and Constrains

The inlet and the outlet pipes have been added to apply a frictionless bearing at their ends and the

pressure has been applied at the inside of the structure. Further the pressure load effects have been

applied on the outlet pipes. Please note that only 60% of the force created by the pressure load on thearea has been applied, as this is the conventional portion transferred into the structure. The other

portion of 40% is usually transferred into the surrounding oncrete.

The thickness of the steel plate on the upstream side has been considered to be 12 mm in order to

have a safe transmission at the welding between the steel pipe and the inlet cone. However the

penstock does not necessarily have to be 12 mm on its total length. From a level of approx. 265 masl

and above the thickness could be reduced to 10 mm.

Figure 2.2.1


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Pressure only:

Figure 2.2.2

Forcse from pressure load Pressure only:


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3. Criteria

3.1 Criteria for the Static Analysis

The analysis of the static loads is executed according to the standard ASME BPVC VIII-2 Appendix 4applying the method of Stress Categories, which is outlined below:

Figure 3.1.1


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3.2 Definition of the Admissible Limits

3.2.1 Limit ing Stress Sm

The limiting stress Smis defined in ASME II Part as the lower value of 1/3 of the Tensile Strength or 2/3

of the Min. Yield Strength, which gives in our case the following values:

Rib (Scythe): thickness < 40 [mm] Sm= Rm/ 3 = 490 / 3 = 163,3 [MPa]

Steel Cones: thickness < 16 [mm] Sm= Rm/ 3 = 490 / 3 = 163,3 [MPa]

The value of the factor k for the load cases 1 & 2 under the condition Normal according to the definition

in 1.2 equals to k = 1.

3.2.2 Limit ing Stress Sps

With respect to the limiting stress Sps it is proposed in the Appendix 4, 4.134-b to summarize the

primary and the secondary stresses excluding the peak stresses.

Rib (scythe): applying 7.0704.0490

345

==m

s

R

R, follows Sps= 3*Sm= 490 [MPa]

Steel cones: applying 7.0724.0490

355==

m

s

R

R, follows Sps= 3*Sm= 490 [MPa]

These considerations do not release to check in parallel all other criteria, such as the low cycle fatigue

and further that the limiting stress criteria are applied to obtain a safe behaviour even with local effects

in yielding zones which are always based on data from the linear elastic behaviour.

3.2.3 Limit ing Stress Exceptional

Finally the stress limits during the exceptional pressure test are defined by ASME Test Load case and

are therefore based on different limitations (ASME VIII 2, Part AD, AD-151.1):

The primary membrane stress must be less than 90 [%] of Yield Strength Rs:

Rib (scythe): Pm0,9 x 345 = 310, 5 [MPa]

Steel cone: Pm0,9 x 355 = 319, 5 [MPa]

The sum of all Primary Membrane Stresses is based on a function referred to the Primary

Meme bran Stress:

o in case m0,67 x Rsthan Pm+ Pb1,35 x Rs, which means that for:

Rib (scythe): Pm+ Pb466 [MPa] if m231 [MPa]

Steel cone: Pm+ Pb479 [MPa] if m240 [MPa]

o

in case 0,67 x Rs

859063351 00 PROV CalculationReportBifurcazioneFinal

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