Stress Analysis Report

Project : ULU PANDAN NEWATER PLANT UPGRADING WORKS

STRESS ANALYSIS REPORT MF FEED SYSTEM KSES DOC.NO: K682_887_02_003_1

1 0 Rev.

19/03/11 08/03/11 Date

EC EC By

Incorporate Client’s Comment For Approval Description

File : 10Name Bukit Batok Crescent Crescent #06-05 The Spire, Spire, Singapore 658079

K682_887_02_003_1_Stress Analysis Report

GCL GCL Check

KHL KHL Appr.

Page : 1

of 153

This document contain confidential and proprietary information belonging to Keppel Seghers Engineering Singapore Pte Ltd. Any disclosure, copying, distribution or the taking of any action in relation to the contents of this document is strictly prohibited.

Ulu Pandan Newater Plant Upgrade Project Stress Analysis of MF Feed System

CONTENTS Section

Page

1.0

Introductio Introduction n .......... ............... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ..... 3

2.0

Referenc References es .......... ............... ......... ......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ........ ... 3

3.0

Input Input Data and Assumptio Assumptions ns .......... .............. ......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ..... 4

4.0

Methodolog Methodology y .......... ............... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ........ ... 4

5.0

Results Results and Discussio Discussions ns .......... ............... .......... .......... .......... .......... .......... ......... ......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ....... .. 8

Appendices Appendix I

Properties of ABS Pipe

Appen pendix dix II

Caesar sar II Input and Outpu tput a. Stress Isometrics b. Input Listing c. Post-Mod Stress Summary d. After Recommendation Stress Summary e. After Recommendation Restraint Summary


CONTENTS Section

Page

1.0

Introductio Introduction n .......... ............... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ..... 3

2.0

Referenc References es .......... ............... ......... ......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ........ ... 3

3.0

Input Input Data and Assumptio Assumptions ns .......... .............. ......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ..... 4

4.0

Methodolog Methodology y .......... ............... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ........ ... 4

5.0

Results Results and Discussio Discussions ns .......... ............... .......... .......... .......... .......... .......... ......... ......... .......... .......... .......... .......... .......... .......... .......... .......... .......... ....... .. 8

Appendices Appendix I

Properties of ABS Pipe

Appen pendix dix II

Caesar sar II Input and Outpu tput a. Stress Isometrics b. Input Listing c. Post-Mod Stress Summary d. After Recommendation Stress Summary e. After Recommendation Restraint Summary


1.0

Intro troduc duction MF Feed Feed Syst System em of Ulu Ulu Panda Pandan n Ne Newa wate terr Plan Plantt consi consist sts s of ten ten (10) (10) identi identical cal trai trains ns of Filt Filtra rate te membr me mbran ane e vess vessel els s each each fed by an elec electri tric c mot motor or drive driven n MF Feed Feed Pump Pump throu through gh a MF Feed Feed Strain Strainer. er. Piping Piping system was fab fabric ricate ated d using using ABS piping piping materia materiall and pipe pipe failure failures s at severa severall locations were observed during normal daily operation. The objective of this analysis is to lower the stresses level at several critical areas so that balance stress distribution distribution in whole system can be achieved. achieved.

2.0

References 2.1

Piping Piping materia materials ls prope propertie rties s are as given given by by manufa manufactu cturer rer,, Eurapi Eurapipe pe and and are atta attached ched under under Appendix I.

2.2 2.2

The follo followi wing ng drawin drawings gs / corr corresp espon onden dence ces s rece receiv ived ed from custo customer mer and suppl supplie iers rs were reviewed and used as the basis for input to the analysis: - KSES/M/MFF/001 Rev0 – MF Feed from MF Feed Pump to Strainer - KSES/M/MFF/002 Rev0 – MF Feed from Strainer No. 1 to MF Train No. 1 - KSES/M/MFF/011 Rev0 – MF Feed from Strainer No. 10 to MF Train No. 10 - K682_402_02_0 K682_402_02_003_2 03_2 Rev2 – MF Feed Piping Pipe Support and Details - PUB/UPWRP/KSES/PS/025 RevA – Pipe Support Layout Plan Pretreatment Area – Part

A Elevation 107.65 to 113.413 - PUB/UPWRP/KSES/PS/026 RevB – Pipe Support Layout Plan Pretreatment Area – Part

B Elevation 107.65 to 113.413 - PUB/UPWRP/KSES/PS/027 RevA – Pipe Support Layout Plan Pretreatment Area – Part

C Elevation 107.65 to 113.413 - PUB/UPWRP/KSES/PS/028 RevA – Pipe Support Layout Plan Pretreatment Area – Part

A Elevation 113.413 to 120.454 - PUB/UPWRP/KSES/PS/029 Rev- – Pipe Support Layout Plan Pretreatment Area – Part

B Elevation 113.413 to 120.454 - PU PUB/U B/UPWR PWRP/K P/KSES SES/M/0 /M/025 25 Rev0 Rev0 – Piping Piping Layout Plan MF Area Area – Part Part A Elevat Elevation ion

107.65 to 113.413 - PU PUB/U B/UPWR PWRP/K P/KSES SES/M/0 /M/026 26 Rev0 Rev0 – Piping Piping Layout Plan MF Area Area – Part Part B Elevat Elevation ion

107.65 to 113.413 - PU PUB/U B/UPWR PWRP/K P/KSES SES/M/0 /M/027 27 Rev0 Rev0 – Piping Piping Layout Layout Plan Plan MF Area Area – Part Part C Elevat Elevation ion

107.65 to 113.413 - PU PUB/U B/UPWR PWRP/K P/KSES SES/M/0 /M/028 28 Rev0 Rev0 – Piping Piping Layout Plan MF Area Area – Part Part A Elevat Elevation ion

113.413 113.413 to 120.454 - PU PUB/U B/UPWR PWRP/K P/KSES SES/M/0 /M/029 29 Rev0 Rev0 – Piping Piping Layout Plan MF Area Area – Part Part B Elevat Elevation ion

113.413 113.413 to 120.454 - PU PUB/U B/UPWR PWRP/K P/KSES SES/M/0 /M/030 30 Rev0 Rev0 – Piping Piping Layout Layout Plan Plan MF Area Area – Part Part C Elevat Elevation ion

113.413 113.413 to 120.454 - Supplement Information of Surge & Stress Analysis – Data provided by customer on 27

Dec 2010


- Expansion Bellow Data – Data provided by customer on 27 Dec 2010 - Miscellaneous email correspondences - Eurapipe Catalogue Issue 1 Revision 1

3.0 3.0

Inpu Inputt Da Data ta and and Assum ssumpt ptio ions ns The following information and assumptions were used for analysis: a. The highest and lowest temperature temperature during during day and night time is assumed to be 31°C and 26°C 26°C respectively. b. Un Unba bala lanc nce e force forces s used used in the the ana analy lysi sis s to simul simulate ate the the surge surge effects effects are are take taken n from from surg surge e analysis report KSES DOC.NO: K682_887_02_002_0.

4.0

Metthodo Me odology ogy 4.1

General The piping configurations of the ten (10) trains of MF Feed are generally similar at the pump area up to the strainer and Filtrate Train areas from the piperack. The piping configuration for each train along the piperack runs differently from flexibility point of view with the legs of each turn varying from train to train. Among the ten trains of MF Feed, two trains were selected for analysis. They are piping from MF Feed Pump to MF Feed Train No.1 and Train No.10. The two trains were chosen because their piping configurations represent the most extreme conditions in the group from the perspective of flexibility. Hence conclusion arrived at for any one train shall be extrapolated for the rest of the trains. The software used for the stress analysis is the Caesar II software package, version 5.20, by Coade Inc. The program analyses flexibility under the assumption that displacement strains will produce propor proportio tional nal stress stress over over a suffic sufficien iently tly wide wide range. range. This This assumpt assumption ion of elasti elastic c beh behavi avior or appears app ears valid for ABS with the pipe manufact manufacture urer’s r’s confirmati confirmation on that “ABS is a ductil ductile e materia materiall and the mode of failur failure e resembl resembles es tha thatt of soft copper” copper” (Refere (Reference nce:: Eurapip Eurapipe e Catalogue Issue 1 Revision 1). As the ASME B31.3 piping code which was used for the design does not specify any stress-limiting criteria or methods of stress analysis applicable for plastic pipe systems and the safe limits for computed stresses (refers to as allowable stresses) are also not available from manufacturer, the method proposed by Coade, the software developer, in their April 1991 article in “Mechanical Engineering News” is adopted in this analysis. The method suggested by Coade for determining the allowable stresses for plastic pipe is based on the allowable span given by manufacturer. A straight pipe, filled with water, sitting on rest supports spaced at the maximum span stated by the manufacturer’s catalo catalogue gue is analys analysed ed using using Cae Caesar sar II and the largest largest code stress stress and largest largest bending bending stress at the support location are taken as the limits to the bending and code stresses that should be allowed in the operating system. However, the allowable stresses for piping so obta obtain ined ed appe appear ar to be very very low low simpl simply y beca becaus use e the the pipe pipe allow allowabl able e span span tab table le is too too conservative. Adopting these values would require many span corrections to be performed, which does not make sense as many of the failures did not occur at over-spanned section of the pipe. On the other hand, based on the allowable midspan deflection of 1/500 given by


the manufacturer, the span allowed under such deflection can go to a value as high as twice that stated by the manufacturer. Hence the allowable stress used to assess the flexibility of the ABS system for this report is based on the allowable midspan deflection rather than allowable pipe span. This approach is considered to be more realistic and practical in this situation. In the same token, the allowable bending stress and code stresses for bends and elbows are determined based on the allowable displacement for an expansion loop configuration given by the supplier. supplier. Stre Stress ss Inte Intensi nsifi fica cati tion on Facto Factorr (SIF (SIF)) of 2.3 2.3 wa was s also also prop propos osed ed by Co Coade ade for all all fitti fitting ng connec connectio tions ns (inclu (includin ding g bends bends and tee tees) s) to accommo accommodat date e complex complex stress stress distri distribut bution ion at fitt fittin ings gs.. It is wo wort rth h not notin ing g that that this this valu value e is only only a Co Coade ade sugges suggesti tion on not not based based on any experimental findings. The B31.3 code prescribes different value of SIF for bends and tees. Hence using a common value for both fittings appears to be too conservative at least for tees. For example, B31.3 SIF factor for 400ND elbow and tee are 2.2 and 4.0 respectively. In order that the possible cause of failure can be identified, an analysis was carried out on the current piping system which has been modified following following various incidences incidences of failure. failure. It appears app ears that the these se modific modificati ations ons have have not been success successful ful in preventi preventing ng failur failures. es. The analys ana lysis is (termed (termed “Post“Post-mod mod analys analysis” is”)) will will be based based on the actual actual piping piping and support support configuratio configuration n currently currently installed. installed. These modification modifications s were performed by the customer in response to numerous failures without the benefit of stress or surge analysis. The purpose of this analysis is to identify the possible causes of failures and provide recommendations which will help mitigate these failures.

4.2

Nome omenclature ure Coordinate System: The direction of x, y, and z coordinates are as defined below: -

X coordinate positive from Grid J to M

-

Y coordinate positive vertical upwards

-

Z coordinate positive from Grid 10 to 8

Support Types: Nomenclature Nomenclature for support support used in analysis, analysis, ANC

– Anchor hor, tran ransla slational and rotational mo mov veme men nts are not not all allow owe ed.

REST RE ST (+Y (+Y)

– Re Rest stin ing g supp suppor ort, t, vert vertic ical al dow downw nwar ard d mo move veme ment nt is rest restra rain ined ed..

Y

– Vertical downward/upward movement is restrained.

GUID GUIDE E

– Guid Guided ed supp suppo ort, rt, late latera rall mo move veme ment nts s are are rest restra rain ined ed for for hori horiz zonta ontall pipe; both horizontal horizontal direction movements are restrained for vertical pipe.

LIMI LIMIT T STOPP STOPPER ER

– Axial Axial moveme movement nts s are are not not allow allowed. ed.

+Z

– Movement in -Z direction is restrained (Z coordinate positive from Grid 10 to 8).


Y/GUIDE

4.3

– U-Bolt.

Load Cases Case No

Load Case

Stress Category

Output

1

W+T1+P1

OPE

Disp/Force/Stress

2

W+T1+P1+F1

OPE

Disp/Force/Stress

3

W+T1+P1+F2

OPE

Disp/Force/Stress

4

W +P1

SUS

Disp/Force/Stress

Where:

4.4 4.4

W

is:

Pipe and contents weight

T1

is:

Operating Temperature

P1

is:

Operating Pressure

F1 and F2

is:

Forces due to surge

Allow llowab able le Stre Stress sses es Allowable stresses used for this analysis are computed based on the procedures described in 4.1 above. Allowable bending stress for straight pipes The allowable stress values are computed based on maximum spacing between supports such such as the mid-sp mid-span an defl deflec ecti tion on does does not exceed exceed 1/500 1/500 of the the span. span. A summar summary y of maximum spacing between supports for various pipe size used in this analysis is given in Table 4.1.

Table 4.1 – Maximum Maximum Spacing Spacing Between Supports Maximum Span (m) Pipe Size

Allowable

Manufacturer

(DN)

Deflection

Allowable Span

Criteria

Criteria

DN100

3.45

1.89

DN150

4.40

2.13

DN200/OD225

4.75

2.48

DN225/OD250

5.10

2.60

DN300/OD315

5.90

2.77

DN375/OD400

6.80

3.32

As stated in Section 4.1, the allowable deflection criteria are used in this report for flexibility analysis.


Allowable Bending Stress for Bends/Elbows Allowable bending stress for bends/elbows is obtained based on maximum allowable displacement for an expansion loop configuration provided in supplier’s catalogue. Figure 4.1 and Table 4.2 show the configuration and allowable displacement of an expansion loop for each pipe size given in Eurapipe’s catalogue.

Figure 4.1 – Expansion Loop Configuration

Table 4.2 – Expansion Loop Leg Length (mm) Pipe Size

Expansion ΔL/2 (Fig. 4.1) (mm)

(DN)

25

50

75

100

150

200

DN100

1400

2200

2500

2900

3500

4200

DN150

1800

2600

3100

3700

4500

5000

DN200/OD225

2500

3600

4700

5300

6200

7200

DN225/OD250

2600

3700

4800

5400

6300

7300

DN300/OD315

2800

4200

5200

6000

7100

8800

DN375/OD400

4400

6400

8000

9300

10300

-

Allowable Hoop Stress Allowable hoop stress is computed by taking into consideration of Pressure/Temperature Derating factor as shown in Figure 4.2.

Figure 4.2 – Pressure/Temperature Derating Curve


The allowable hoop stress is determined based on derating pressure at operating temperature. PN12 curve is used for pipe size DN100 and DN150, while for pipe size DN200(OD225), DN225(OD250), DN300(OD315) and DN375(OD400), PN9 curve is used for more conservative approach since PN10 curve is not available.

Allowable Code Stresses The allowable combined stress (Code Stress) based on the maximum principal stresses combination of longitudinal stress due to pressure, bending and torsion is arrived at on the same principle as that of the allowable bending stress.

Based on different criteria mention above, various allowable stresses are obtained and summarized in Table 4.3 below.

Table 4.3 – ABS Allowable Stress

Pipe Size (DN)

5.0

Pipe Rating (PN)

Temperature

Caesar II Method PIPE/TEE

Derating

ELBOW

Combine

Bending

Combine

Bending

Stress

Stress

Stress

Stress

31°C Hoop Stress

(mm)

(bar)

(MPa)

(MPa)

(MPa)

(MPa)

(MPa)

DN100

12

4.29

1.42

2.80

1.64

5.51

DN150

12

4.44

1.57

2.54

1.52

5.53

DN200/OD225

10

5.69

1.97

3.75

1.50

6.99

DN225/OD250

10

5.73

2.04

3.78

1.18

6.95

DN300/OD315

10

5.86

2.17

3.97

1.28

6.98

DN375/OD400

10

5.93

2.27

4.53

1.31

6.99

Results and Discussions Figure 5.1 and 5.2 show the locations of some highlighted nodes used in the following discussion for Train 1 and Train 10 respectively. For complete listing of nodes and their location, please refer to the stress isometrics in Appendices.

Post-mod Analysis for MF Feed System.

Train 1 Table 5.1 and 5.2 below show the stresses at key locations in the MF Feed system for Train 1.


Table 5.1 – Stresses in key areas of Train No. 1 (without Surge Loads) Post-mod Analysis Node

Type

Stress

Allowable

Ratio

(kPa)

(kPa)

%

285

elbow

2189.7

1310

167.2

137

elbow

1346.3

1310

102.8

80

tee

1482.2

2270

65.3

55

elbow

700

1310

53.4

209

elbow

688

1310

52.5

Table 5.2 – Stresses in key areas of Train No. 1 (with Surge Loads) Post-mod Analysis Node

Type

Stress

Allowable

Ratio

(kPa)

(kPa)

%

285

elbow

2227.4

1310

170.0

137

elbow

1362.7

1310

104.0

272

elbow

1000.4

1310

76.4

259

elbow

959.9

1310

73.3

270

elbow

911.3

1310

69.6

80

tee

1482.5

2270

65.3

Figure 5.1 – Nodes for MF Feed Pump to Train No. 1


Train 10 Table 5.3 and 5.4 below show the stresses at key locations in the MF Feed system for Train 10. Table 5.3 – Stresses in key areas of Train No. 10 (without Surge Loads) Post-mod Analysis Node

Type

Stress

Allowable

Ratio

(kPa)

(kPa)

%

285

elbow

1843.5

1310

140.7

249

elbow

1058.7

1310

80.8

137

elbow

915.4

1310

69.9

80

tee

1482.2

2270

65.3

207

elbow

832.1

1310

63.5

Table 5.4 – Stresses in key areas of Train No. 10 (with Surge Loads) Post-mod Analysis Node

Type

Stress

Allowable

Ratio

(kPa)

(kPa)

%

207

elbow

2542.3

1310

194.1

249

elbow

2497.2

1310

190.6

285

elbow

2412.3

1310

184.1

252

elbow

1902.7

1310

145.2

80

tee

1481.1

2270

65.2

Table 5.1 to 5.4 show that tee near the pump discharge (Node 80) is one of the key area in MF Feed system where actual failure occurred. Results above show that the stress level is within the allowable if SIF of 2.3 is used. However if the SIF of 4.0 is used, the stress ratio would increase to 111% which implies that the value of 2.3 for tee may be too low. If this is true, it suggests that stress may be a contributing factor to observed failure at this tee. Therefore, measures needed to be taken to reduce the stress level at this tee. The value of stress ratio at Node 80 during surge loads does not show any increase from operation without surge, indicating that surge is unlikely a factor that cause actual failure at this tee.


Figure 5.2 – Nodes for MF Feed Pump to Train No. 10

The high stress ratios for the elbows in Table 5.1 to 5.4 would suggest that failure may occur at those elbows. Since none of the elbows suffer any sign of failure, it may also suggest that the allowable displacements given by manufacturer for the expansion loops are conservative. Nevertheless it is recommended that measures be taken to reduce the stress level at these elbows to the allowable calculated. Recommendation High stresses at elbows/bends are mainly caused by thermal expansion and can be solved by modifying some of the supports to allow for more flexibility in the piping system. Our recommendation for tee at Node 80 is to remove some of the U-bolts around the tee (Node 77, 82) and that at the elbow upstream of the tee (Node 69) to regain some flexibility to the piping system. This will relieve the stresses at the tee from 65.3% to 30.3%. At this level, overall stress would still be within 100% even if SIF factor of 4.0 is used. This recommendation should also be applied to the other trains. For the elbows, the recommendation is to remove any extra U-bolts that restrict elbow flexibility or relocate support to a location directly at the elbow using dummy type support. Table 5.5 and 5.6 below summarized the support modifications required to reduce the stresses at Train 1 and Train 10 respectively. These are also indicated on the marked up isometrics provided in Appendix II. Table 5.5 – Supports Modification Summary for MF Feed Pump to Train No.1 Support Node

Recommendation

Remarks

69, 77, 209

REST

Remove U-Bolt


Support Node

Recommendation

Remarks

82

+Z

Remove U-Bolt

139(137), 279(285)

REST

Support Shifted

Table 5.6 – Supports Modification Summary for MF Feed Pump to Train No.10 Support Node

Recommendation

Remarks

REST

Remove U-Bolt

82

+Z

Remove U-Bolt

279(285)

REST

Support Shifted

69, 77, 170, 205, 209, 252

The above modifications are recommended to reduce the stresses in the piping to achieve more balance stress distribution in the system. See Table 5.7 and 5.8 for stress ratio after implementation of the proposed modifications. Table 5.7 Stress Ratio After Mitigation Train 1 Train 1 (with Surge Loads) Node

Type

Stress

Allowable

Ratio

(kPa)

(kPa)

%

285

elbow

68.9

1310

5.3

137

elbow

437.2

1310

33.4

272

elbow

527.9

1310

40.3

259

elbow

919.1

1310

70.2

270

elbow

636.4

1310

48.6

80

tee

688

2270

30.3

Table 5.8 Stress Ratio After Mitigation Train 10 Train 10 (With Surge Loads) Node

207

Type

elbow

Stress

Allowable

Ratio

(kPa)

(kPa)

%

249.2

1310

19


Train 10 (With Surge Loads) Node

Type

Stress

Allowable

Ratio

(kPa)

(kPa)

%

249

elbow

335.1

1310

25.6

285

elbow

90.6

1310

6.9

252

elbow

147.8

1310

11.3

80

tee

688

2270

30.3

Customer has to also ensure support design is able to withstand the calculated restraint loadings given in Appendix II.

Stress Analysis Report

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