Specification for Piping Stress Analysis - REFERENCIA CRITERIO

SPECIFICATION FOR PIPINGSTRESS ANALYSIS

TCM IDENTIFICATION CODE

3507-XH-SG-002

PROJECT DOCUMENT NUMBER

&TCM-L-SE-000002.200

Plant: LDPE Plant Client : POLIOLEFINASINTERNACIONALES C.A.

Location: El Tablazo -Estado Zulia Venezuela Page 1 of 18 Issue 02




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1. INTRODUCTION 32. NORMATIVE REFERENCES 3

2.1 BASIC CODES .................................................................................................................... 32.2 REFERENCE STANDARDS.................................................................................................... 32.3 CLIENT’S PROJECT SPECIFICATIONS ................................................................................... 3

3. SCOPE OF STRESS ANALYSIS VERIFICATIONS 44. CATEGORIES OF LINES AND STRESS ANALYSIS LEVELS 4

4.1 CATEGORY 1 ..................................................................................................................... 44.2 CATEGORY 2 ..................................................................................................................... 44.3 CATEGORY 3 ..................................................................................................................... 4

5. ACTIONS COMING FROM STRESS ANALYSIS VERIFICATION 56. DEFINITION OF SIGNIFICANT ACTIONS FOR STRESS ANALYSIS

CALCULATIONS 56.1 WEIGHT ............................................................................................................................ 66.2 TEMPERATURE .................................................................................................................. 6

6.2.1 Definitions .................................................................................................................... 66.2.2 Flexibility analysis........................................................................................................ 66.2.3 Equipment and machines reactions ............................................................................... 76.2.4 Flanged couplings loads ............................................................................................... 76.2.5 Spring supports sizing................................................................................................... 7

6.3 PRESSURE.......................................................................................................................... 76.4 DISPLACEMENT OF RESTRAINTS (DIS) ............................................................................... 86.5 OCCASIONAL LOADS ......................................................................................................... 8

6.5.1 Wind ............................................................................................................................. 86.5.2 Earthquake ................................................................................................................... 8

6.6 TEST CONDITION VERIFICATION ...................................................................................... 106.7 ALTERNATIVE CONDITION................................................................................................ 106.8 DISPLACEMENTS AT BATTERY LIMITS .............................................................................. 106.9 LOAD COMBINATION CASES ............................................................................................ 10

7. PULSATION STUDY 118. LEAKAGE ANALYSIS FOR FLANGES 129. COEFFICIENT OF STATIC FRICTION 1210. SPRING SUPPORT 1211. EXPANSION JOINTS 1312. VERIFICATION OF EQUIPMENT AND MACHINES REACTIONS 1313. LOADS TRANSMISSION TO CIVIL DEPARTMENT 1414. STRESS ANALYSIS REPORT 1515. GENERAL REQUIREMENTS FOR NUMERICAL MODEL AND FOR CALCULATION

15APPENDIX 1: CATEGORIES OF LINES ................................................................................. 16APPENDIX 2: TABLE FOR ALLOWABLE EQUIPMENT NOZZLE LOADS ......................... 18



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1. INTRODUCTION

Scope of the present document is to explain the practices establishing the minimum requirementsthat the piping stress analyst shall adhere to when performing activities intended to ensureadequate engineering review of piping systems. The general scope of these activities is to verifythat every piping arrangement is sufficiently flexible to allow each line to thermally expand orcontract without overstressing pipes or connected equipment, and adequately supported so that nodamage occurs due to loads resulting from weight, pressure, wind, earthquake, shocks, foundationsettlement etc. The purpose of this specification is to ensure the sound and uniform approach to thereview of the mechanical safety of piping and related systems, and to give guidelines to producingevidence that this has been done satisfactorily.

2. NORMATIVE REFERENCES

2.1 Basic Codes

The following ASME Code shall be entirely applied as the basis of the piping system stress analysisin conjunction with this specification.

ASME B31.3 “Process Piping”

2.2 Reference Standards

The following standards (according to &ZA-A-LX 0001 “Codes & Standards for Olefinas III yPolietilenos Ana Maria Campos Complex”) shall be applied in conjunction with the requirements setforth in this specification.

ANSI B16.5 “Pipe flanges and flanged fittings“API 560 “Fired Heaters for General Refinery Service”API 610 “Centrifugal Pumps for Petroleum, Heavy Duty Chemical, and Gas Industry

Services”API 611 “General-Purpose Steam Turbines for Petroleum, Chemical, and Gas

Industry Services”API 617 “Centrifugal Compressors for Petroleum, Chemical, and Gas Service

Industries”API 618 “Reciprocating Compressors for Petroleum, Chemical, and Gas Industry

Services”API 650 “Welded Steel Tanks for Oil Storage”API 660 “Heat Exchangers for General Refinery Services“API 661 “Air-Cooled Heat Exchangers for General Refinery Services”NEMA SM 23 “Steam turbines for Mechanical Drive Service”

2.3 Client’s Project Specifications

No stress specification has been issued by Client or PMC.

otorres

Note

Standard API 560 doesn't appear in &PMC-A-LX 0001.001 "List of Codes & Standards"



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3. SCOPE OF STRESS ANALYSIS VERIFICATIONS

The main purposes of stress analysis activities are the following:

• To identify, basing on the criteria described in paragraph 4, all those piping systems that arecritical from the thermal behaviour point of view, or require deep verifications because ofparticular operating conditions.

• To identify according to the different grades of line criticality the most suitable verificationmethod.

• For piping systems classified as critical (as per paragraph 4.3):

- to verify that the maximum stress levels are below the maximum allowable values statedby the governing code for the different load combinations;

- to verify that reaction forces on machines and equipment nozzles are below the limitsdescribed in paragraph 12;

- to calculate the loads transferred to the structures by the piping supports, in order toallow the civil designer to verify them;

- to verify that the piping thermal expansion or contraction will not cause interference withadjacent pipes and structures.

• For piping systems belonging to the categories described in paragraphs 4.1 and 4.2, toperform visual check or simplified analysis based on the routing of the line.

4. CATEGORIES OF LINES AND STRESS ANALYSIS LEVELS

All pipes of the plant shall be reviewed during the design. The level of investigation can be more orless detailed as specified below, according to the category each line belongs to.

4.1 Category 1

These lines are characterized by a combination of temperature – diameter as shown in appendix 1(figure 1, category 1). A visual investigation (based on knowledge / experience) or a simplifiedmethod analysis can be carried out for this piping.

4.2 Category 2

These lines are characterized by a combination of temperature – diameter as shown in appendix 1(figures 1 and 2, category 2). A simplified method analysis can be carried out for this piping.

4.3 Category 3

Formal computer analysis (by means of calculation software CAESAR II) shall be performed onlines belonging to this category taking into account the pipe diameter, the maximum temperature



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expected in any condition, the type of equipment or machine the pipe is connected to, the type offluid, the pipe material. A report of this analysis shall be produced according to what specified inparagraph 13.

This category includes:

• air cooler piping 4” and larger;• lines connected to rotating machines with the couple of values (NPS, ∆T) as per appendix 1

(figure 2, category 3);• lines 3” and larger connected to equipment (tanks) or structures subject to excessive

settlement and/or displacements;• lines subject to mixed phase flow (liquid and vapor) and identified as critical by Process

Department, because of dynamic phenomena such as slug flow, vibrations occurrence etc.;• lines identified as vibrating service (reciprocating compressors suction and discharge); • lines connected to pressure safety valves, selected by Stress Analysis Engineer basing on

valve size and potential reaction;• lines defined as category III in the appendix 1 (figure 1);• all high pressure piping (PN 500 and above), except tubing.

All the lines belonging to this category shall be grouped in stress systems and listed in a “StressCritical Line List” indicating all relevant information for each line involved in the analysis.

5. ACTIONS COMING FROM STRESS ANALYSIS VERIFICATION

The stress analysis results may require changes of the analyzed piping system. These changes,always substantiated by project savings, process and piping requirements, may include:

• change in piping routing;• introduction of expansion loops in the piping run;• introduction of special items like expansion joints, spring supports, shock absorbers;• use of either different or additional or differently located restraints in contrast with initial

provisions;• development of special supports.

6. DEFINITION OF SIGNIFICANT ACTIONS FOR STRESS ANALYSISCALCULATIONS

The computer-aided analysis shall take into account different internal and external actions, whoseeffects in terms of stress and loads on restraints have to be properly combined.International system of S.I. units shall be used. Exceptions are the following: pressure units inbar(g) and temperature units in Celsius degrees (°C).

otorres

Note

The meaning of the paragraph is not clear (barg and Celsius will be used or they are the "exceptions"?). It is recommended to declare that unit system must fully comply with &PMC-A-LX 0003 "Units System Requirements". According to this document "the system of measurement shall be SI units, with the exception of nominal pipe, diameters respectively wall thickness, which shall be either in inches or schedule".



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6.1 Weight

Weight of piping and its components, including internal fluids and insulation, shall be considered asuniform distributed loads. Other weights as flange, valves or similar can be considered asconcentrated loads.Special consideration shall be given to possible alternative values for fluid density. All possiblevalues shall be defined by Process Department and listed in the Line List. For each possible densityvalue, Process Department shall also define wheter corresponding fluid weight has to beconsidered as a sustained load or as an occasional one (see paragraph 6.5).

6.2 Temperature

6.2.1 Definitions

Tworst = worst temperature scenario for the piping systemTmax = maximum temperature of the lineTope = operating temperature of the line (according to the Line List)Tdes = design temperature of the line (according to the Line List)Tinst = plant installation temperature (defined by project environmental specification)

Tworst is the most severe temperature scenario that the piping system will be subject to during itsoperating life, and it shall be evaluated considering normal operating condition and all possiblealternative conditions (e.g. steam-out, regeneration, shutdown, start-up etc.). Tworst shall be equal toTmax (or to Tdes, if the value of Tmax is not available).

Tinst (installation temperature) shall be assumed to be +28 °C, i.e. the average annual temperatureaccording to document &ZA-A-SB 0001 "Meteorological Conditions for Olefinas III y PolietilenosAna Maria Campos".

Note: metal temperature due to solar radiation shall be assumed to be +87 °C for uninsulated linessubject to solar exposition.

6.2.2 Flexibility analysis

The analysis shall be implemented using the worst differential temperature ∆T, where:

∆T = Tworst - Tinst

For line connected to pumps, temperature decay in the stand-by portion of piping (without warmingby-pass) shall be considered as per the following scheme:

otorres

Note

Is &ZA-A-SB 0001 the document's correct code? According to the table of content, it should be &PMC-A-SB 0001.

Oscar Torres

Sticky Note

According to &PMC-A-SB 0001 "Meteorological Conditions for Olefinas III y Polietilenos Ana Maria Campos", average annual temperature is 27,7ºC, not 28ºC. It is recommended to declare expressly that temperature shall comply with the exact value indicated in &PMC-A-SB 0001 "Meteorological Conditions for Olefinas III y Polietilenos Ana Maria Campos".



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Temperature of stand-by portion to be considered is 50% of operating temperature for insulatedline, and installation temperature for not insulated line.

The steam tracing temperature should be considered for the dead portion of the line (e.g. stand-bypipe or discharge line of a safety valve) that is steam traced.

6.2.3 Equipment and machines reactions

The reactions on equipment and machines nozzles shall be calculated in operating condition, usingthe design differential temperature ∆T, where:

∆T = Tope - Tinst

6.2.4 Flanged couplings loads

The forces and moments acting on flange connection shall be calculated in design condition, usingthe design differential temperature ∆T, where:

∆T = Tope - Tinst

6.2.5 Spring supports sizing

The spring supports shall be set basing on load and travel in operating condition, using operatingdifferential temperature ∆T, where:

∆T = Tope - Tinst

Vendor shall verify that the selected spring support allows the different travel occurring in the worstscenario. For this purpose, spring travel in alternative thermal conditions shall be transmitted toVendor in springs data sheet.

6.3 Pressure

Calculations shall consider the design pressure as per plant Line List.



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6.4 Displacement of Restraints (DIS)

Movement of restraints (equipment nozzles or others) due to thermal expansion or other causes(e.g. settlement of large equipment foundations) shall be considered in the analysis of pipingsystems.

6.5 Occasional Loads

Occasional loads which piping may be subject to shall be taken into account as static loads whenverifying longitudinal stresses. A proper multiplicative factor for the allowable stress shall beconsidered, as per Code requirements.

Occasional loads may include:

• wind loads;• earthquake loads;• loads caused by safety valves opening;• impulsive loads (e.g. slug flow or water hammer, if specified by Process Department).

Special attention has to be paid to the calculation of distributed forces due to wind and earthquake.

6.5.1 Wind

Wind load shall be considered in the design of this plant according to document &ZA-A-SB 0001and to Code ASCE 7-05.Wind load shall be applied as a static load, in the horizontal direction producing the worst conditionsin terms of loads for the piping system, its supports and equipment nozzles.The shape factor considering the pipe surface properties shall be 0,7 for Caesar calculation.The basic values to be considered in the application of ASCE code are the following:

• basic wind speed = 33.5 m/sec• wind exposure = 3 (exposure C; open terrain with scattered obstruction)• structural damping coefficent = 0.03 (standard value)• structural classification = 3• importance factor = 1.15 (category III / IV)

6.5.2 Earthquake

The earthquake load shall be considered in the design of this plant: it shall be applied to pipingsystems as an equivalent static load acting in each of the four horizontal directions North, South,East and West (not simultaneously). The eartquake load is calculated according to paragraph13.3.1 of Code ASCE 7-05. The coefficient of ground maximum acceleration, which is necessary forthe calculation of the seismic force, is determined according to relevant Venezuelan Code Covenin3621:2000.As per ASCE 7-05, the horizontal seismic design force F� is calculated as a fraction of the weightW� by the following formula:

2

otorres

Note

Is &ZA-A-SB 0001 the document's correct code? According to the table of content, it should be &PMC-A-SB 0001.



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F� � 0.4 · a� · S�� · W� R�/I�� 1 � 2 z

h�

z is the piping element elevation with respect to grade, while h is the structure roof elevation: inorder to guarantee a conservative approach, the ratio z/h is considered as 1.The applicable component importance factor I� is 1.50, as per paragraph 13.1.3 of ASCE 7-05.The parameters a� and R� are determined from table 13.6-1:

a� � 2.5 R� � 6.0

The spectral acceleration at short period S��, at last, can be calculated by determining a value ofspectral acceleration A� (Covenin 3621:2000) which is consistant with the definition of S�� itself(see sections 11.4.1 to 11.4.5 of ASCE 7-05): S�� can be assumed as the maximum value of thedesign response spectra defined in paragraph 7.3 of Code Covenin 3621:2000, i.e.

S�� φ · β� · A�

• φ is the correction factor of the horizontal acceleration coefficient, depending on the soiltype

• !� is the spectral amplification factor (see equation 5), depending on ! (parameter ofspectral form) and ξ (damping factor of supporting structure):

!� � β2.3 · $0.0853 & 0.739 · ln ξ+

• ,� is the coefficient of ground maximum acceleration, which can be calculated as the ratioof the ground maximum horizontal acceleration a to the gravity acceleration g (A� � a/g).

According to paragraph 7.2.1 of Covenin 3621:2000 (equation 2), a can be calculated as follows:

a � a�.& ln$1 & P0+120/3

where the parameters a� and γ can be obtained from the Map of Seismic Hazard (see figures 1 and2 of paragraph 7.1), and P0 is the annual probability of exceedance, given in Table 1 depending onthe degree of risk.Basing on the location of the plant in the seismic risk charts, the following values can be consideredfor a� and γ:

a� � 25cm/s8γ � 3.25

For a degree of risk B, P0 is equal to 1029, which leads to the following value for a and A�:

a � 209.4 cm/s8A� � a/g � 0.214



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According to the final report by Tivenca “Soil study for detailed engineering project concerning sitepreparation for the Ana Maria Campos Olefin III and Polyethilene Plant”, the area associated withthe project presents a category S2 spectral form, which means ! � 2.6 according to table 3 ofCovenin 3621:2000. For a damping factor ξ � 3%, the following value can be calculated for !�:

!� � 3.026

According to the same report by Tivenca, the factor φ can be assumed as follows:

; � 0.95

Therefore, the spectral acceleration at short period is

S�� φ · β� · A� � 0.615 Therefore, the total design lateral seismic force is

F� � 0.4 · a� · S�� · W� R�/I�� 1 � 2 z

h� � 0.4 · 2.5 · 0.615$6.0/1.5+ $1 � 2+W� � 0.46 W�

6.6 Test Condition Verification

An additional load case shall be foreseen when the Line List indicates that hydraulic test is required.In this case the calculations shall be performed considering erection temperature, internal fluidweight, test pressure, excluding insulation weight and corrosion.Results of the analysis may require hydraulic test on the ground or the use of temporary supports,in order to avoid overloads on equipment and structures.

6.7 Alternative condition

Additional load cases shall be foreseen when the Line List indicates design alternative conditions(e.g. steam-out, regeneration etc.).Steam-out conditions are defined in Equipment Process Data Sheets.

6.8 Displacements at Battery Limits

As a general rule, axial stops and guides will be provided on pipes near Battery Limits to reduce asmuch as possible piping displacements on the Battery Limit points.

6.9 Load Combination Cases

The calculation of forces and moments acting on restrains and of the stress level of the pipingsystem shall be based on the following load combinations, according the prescriptions stated by thecode ASME B31.3 – 2002 Edition:

otorres

Note

In this paragraph it is not established the same criteria indicated in &PMC-L-SE 0003 "Interface Requirements Piping Design". According to this document (&PMC-L-SE 0003), piping shall be designed for zero expansion at battery limit. Therefore a pipe support (anchor type) shall be installed close to physical battery limit defined as pipe stress analysis limit point. Is there any reason not to follow the same criteria?

otorres

Note

According to &PMC-A-LX 0001.001 "List of Codes & Standards" it must be 2005 edition. It is important to mention that ASME B31.3 "Process Piping", 2008 edition, is the latest version of this standard.



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No. Load Cases StressType Load Type Comb.

MethodL1 W+P1+T1+D1+H OPE Normal Operating Condition AlgebraicL2 W+P1+T2+D2+H OPE Design Condition AlgebraicL3 W+P1+T3+D3+H OPE Alternative Operating Condition (if any) AlgebraicL4 W+P1+T1+D1+H+WIND OPE Operating plus Wind AlgebraicL5 W+P1+T1+D1+H+U OPE Operating plus Earthquake AlgebraicL6 W+P1+T1+D1+H+F OPE Operating plus Occasional Loads AlgebraicL7 W+P1+H SUS Sustained AlgebraicL8 WW+HP HYD Hydraulic Test AlgebraicL9 L1-L7 EXP Displacement Stress Range AlgebraicL10 L2-L7 EXP Displacement Stress Range AlgebraicL11 L3-L7 EXP Displacement Stress Range AlgebraicL12 L4-L1 OCC Wind net Deflection AlgebraicL13 L5-L1 OCC Earthquake net Deflection AlgebraicL14 L6-L1 OCC Occasional Loads net Deflection AlgebraicL15 L12+L7 OCC Occasional Stress due to Wind ScalarL16 L13+L7 OCC Occasional Stress due to Earthquake ScalarL17 L14+L7 OCC Occasional Stress due to Occasional Loads Scalar

where:• W = weight (see par. 6.1)• WW = water filled weight (see par. 6.6)• T1, T2, T3 = temperature (see par. 6.2)• P1 = pressure (see par. 6.3)• HP = hydrotest pressure (see par. 6.6)• D1, D2, D3 = displacements (see par. 6.4)• H = concentrated permanent forces (such as spring forces)• F = external forces (see par. 6.5)• WIND = wind loads (see par. 6.5.1)• U = uniform loads (earthquake) (see par. 6.5.2)

The cyclic factor to be used is 1 (corresponding to 7000 operating cycles).

7. PULSATION STUDY

All process lines connected to reciprocating compressors must be analyzed by the equipmentVendor according to API 618. The Vendor will perform acoustical and mechanical analysis, in order to prevent the occurrence ofany resonance phenomena by the optimization of piping routing and supports.In order to provide the Vendor with all necessary information, TCM will collect and transmit thefollowing documents:

• Reports of static stress calculations for all piping systems involved;• Piping isometric drawings;• Civil drawings of all structures used to provide piping supports.



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After the analysis, the Vendor shall prepare a calculation report detailing all relevant comments.TCM will then update piping routing and supports accordingly.

8. LEAKAGE ANALYSIS FOR FLANGES

To avoid leakage in flanges, bending moments and forces on flanges with rating ≥ 300#, diameterDN ≥ 12″ and ∆T ≥ 250 °C, shall be limited according to Equivalent Pressure Method: theequivalent pressure shall be limited to 1.5 times the rating allowable pressure. If this analysis givesnegative result, detailed investigation shall be done according to criteria mentioned in Appendix S,ASME Section VIII Division 1.∆T will be evaluated as per paragraph 6.2.4.

9. COEFFICIENT OF STATIC FRICTION

Friction coefficient must be considered to calculate the horizontal reactions due to the vertical forceon each resting point; the values to be considered shall be those reported in the table below:

Surfaces Coefficient of static frictionSteel on steel 0.3

Steel on Teflon or graphite 0.1

10. SPRING SUPPORT

Spring supports shall be used to support dead weight only. Load variation shall be in accordancewith the following limits:

• Lines connected to rotary machines: variation 8 - 12%• Lines connected to static equipment:

Pipe operating temperature VariationT = 80 ÷ 230°C 15 - 20%T = 231 ÷ 400°C 10 - 15%

T > 400°C 8 - 12%

In all other cases, load variation shall be limited within the maximum value of 25%.All the spring supports defined for the plant shall be listed in data sheets showing all the functionaldata.



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11. EXPANSION JOINTS

Line flexibility requirements shall be as far as possible satisfied by changes of direction, loops etc.The use of expansion joints shall be limited to those cases in which routing modifications aredifficult or impossible for the following reasons:

• excessive pressure drops;• insufficient space available;• excessive loads on structures or terminal equipments.

In any case such solution shall be preventively submitted to approval by Process Department.All the expansion joints defined for the plant shall be listed in data sheets showing all the functionaldata.The design of the metallic expansion joints shall comply with the requirements stated by EJEMAStandard.

12. VERIFICATION OF EQUIPMENT AND MACHINES REACTIONS

Equipment reactions shall be calculated considering the piping thermal expansion in operatingcondition, other external forces acting on the piping (weight, friction) and the displacementsimposed to the piping by connected equipment.The allowable forces and moments on equipment nozzles shall comply with the following applicablestandards, when manufacturer’s data are not available. In any case the manufacturer’s specifiedvalues shall govern.Loads on nozzles eventually exceeding allowable loads defined in the following paragraphs shall betransmitted to equipment Vendor for verification and approval.

a) Pumps designed with API 610(1) The nozzle loads on centrifugal pumps with suction nozzles of NPS 16 nominal diameter orless shall comply with the load criteria of API 610.(2) For nozzle diameters greater than NPS 16, the allowable load values shall be obtained fromthe manufacturer.

b) Compressors designed with API 617Nozzle loads shall comply with the load criteria of API 617.

c) Pressure Vessels and Heat ExchangersAllowable loads on nozzles of pressure and non-pressure equipment shall be in accordancewith TM 300.1 (see appendix 2 for quick reference).

otorres

Highlight

otorres

Highlight

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Note

The code's title must be checked. According to &PMC-A-LX 0001.001 "List of Codes & Standards", correct title is "EXPANSION JOINT MANUFACTURERS ASSOCIATION" (EJMA).

otorres

Note

In paragraph 4.3 it is stated that formal analysis shall be carried out by means of calculation software CAESAR II. For pressure vessels: Caesar II and &PMC-A-LX 0001.001 "List of Codes & Standards" declare the compliance with WRC Bulletin 107 and WRC Bulletin 297, to estimate local stresses in vessel/attachment junctions and stresses in the nozzle itself. In the case of air cooled heat exchangers, caesar II perform the corresponding analysis according to API 661. For Closed Feedwater Heaters, caesar II provides a method for evaluating the allowable loads on shell type heat exchanger nozzles based on HEI bulletin (The method employed by HEI is a simplification of the WRC 107 method). Is there any reason to declare that analysis shall be carried out in accordance with TM 300.1 instead of the codes mentioned above? In order to improve understanding, it is suggested to indicate in "reference standards" the name of this reference together with its code.



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13. LOADS TRANSMISSION TO CIVIL DEPARTMENT

Once all critical systems to be supported by one structure have been analyzed, piping loads on thisstructure have to be transmitted to Civil Department for check and approval. For this purpose, anew document shall be issued, basing on the structure one-line drawing (document 3507-AI-DU-xxx). Stress Engineer shall comment this document with all significant piping loads due to criticalsystems, by means of the following tables, to be filled in for each support.

VL = maximum operating vertical loadVL (test) = hydro-test loadHL N-S = thermal horizontal load in South to North directionHL E-W = thermal horizontal load in West to East directionHL N-S (W) = wind horizontal load in South to North directionHL E-W (W) = wind horizontal load in West to East directionHL N-S (E) = earthquake horizontal load in South to North directionHL E-W (E) = earthquake horizontal load in West to East directionVL (SF) = vertical shaking forceHL N-S (SF) = shaking force in North – South directionHL E-W (SF) = shaking force in East – West directionVL (OD) = occasional dynamic load in vertical directionHL N-S (OD) = occasional dynamic load in South to North directionHL E-W (SF) = occasional dynamic load in West to East direction

Wind and earthquake loads have to be considered as net, i.e. not including weight of pipe /insulation / fluid content nor the effect of thermal expansion.The Civil document, so commented with piping loads, shall be issued by Stress Engineer as a newdocument, whose number will be 3507-XX-DF-xxx.If a preliminary issue of this XX-DF document is needed, including only some of the critical lines tobe supported by the structure, then this document must include a note clearly detailing which lineshave been taken into consideration.



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14. STRESS ANALYSIS REPORT

The report of each calculation shall have the following composition:

COVERCHECKLISTSTRESS SKETCHES

INPUT:• Title• Plot• Element• Unit

OUTPUT:• Restrain summary (SUS), (OPE), (OCC)• Code Compliance (SUS), (EXP), (OCC)• Spring Report (if any)

Input and output files shall be in MM units. All the output report shall be in 132 columns type.

15. GENERAL REQUIREMENTS FOR NUMERICAL MODEL AND FORCALCULATION

• Equipment shall be modeled either by defining a displacements vector at each nozzleconnected to analyzed piping system, or by considering the equipment itself as a rigidsystem, with proper temperatures, dimensions and materials.

• For all vertical vessels the shell temperature between two adjacent outlet nozzles shall becalculated as the average of the temperatures of those two nozzles (as per Line or StreamList).

• Tanks nozzles shall be modeled according to API 620 / 650, so that nozzles rotationproduced by hydrostatic pressure is taken into account.

• Vessels shell flexibility may be modeled according to WRC 297. This will be subject towritten authorization by TCM, to be demanded case by case.

• The opening reaction on lines connected to pressure safety valves shall be multiplied by theDynamic Load Factor, as per ASME B31.1.

• As a general requirement, rotational restraints on pipes should be avoided. Exceptions maybe allowed in some particular cases where this kind of support is necessary to reduce loadson nozzles (e.g. on compressors discharge lines and on high pressure XV valves). In anycase, any support providing a rotational restraint shall be designed as a special support andsubmitted to TCM for approval.

• No resting support shall lift up because of system thermal expansion. If in some particularcases lifting up cannot be avoided, hot sustained stress shall be checked.

• Wind and earthquake loads shall be considered as acting in each of the four cardinaldirections, each one deserving a separate load case.

• For all traced lines an additional condition shall be considered, when the tracing system isworking and the line is inactive.



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APPENDIX 1: CATEGORIES OF LINES

∆T = Tdes – Tinst

-46 0 100 200 300 400

1"

2"

4"

6"

8"

10"

12"

14"

16"

18"

20"

22"

24"

category I category II category III

∆T [°C]

Nom

inal

Pip

eS

ize

[NP

S]



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A line may be considered as critical (category 3) if:

Line Diameter T≥ 2” ≤ -46°C or ≥ 250 °C≥ 8” ≥ 200 °C

≥ 16” ≥150 °C

Lines connected to pumps, reciprocating compressors, centrifugal compressors and turbinesrequires formal analytical calculations (category 3) if the couple of values (NPS, ∆T) stands abovethe lines show in the diagram.

This is equivalent to the following condition:

9NPS401200

T⋅−≥∆

with:NPS ≥ 3”

All other lines connected to these machines belong to category 2.



3507-XH-SG-002


&TCM-L-SE-000002.200



APPENDIX 2: TABLE FOR ALLOWABLE EQUIPMENT NOZZLE LOADS

For both pressure and non-pressure vessels with formed heads (excluding fixed or floating rooftanks, gas holders, silos, bins etc.), Stress Engineer shall check that loads on equipment nozzlesare within the allowable loads shown in the following table.

NOZZLEDIAMETER DIRECT LOAD [N] MOMENTS [Nm]

NPS DN P TL TC ML MC MT

3 80 1500 1500 1500 600 600 6004 100 2100 2100 2100 1100 1100 11006 150 4600 4600 4600 3400 3400 34008 200 6000 6000 6000 5700 5700 5700

10 250 7600 7600 7600 6900 6900 690012 300 9200 9200 9200 8000 8000 800014 350 10800 10800 10800 9200 9200 920016 400 14600 14600 14600 11300 11300 1130018 450 18500 18500 18500 13500 13500 1350020 500 22300 22300 22300 15600 15600 15600≥ 24 ≥ 600 30000 30000 30000 20000 20000 20000

The loads on this table are valid for equipment having a corroded medium radius R = 1000 mm anda shell thickness t = 10 mm, net of corrosion allowance and material mill tolerance.For equipment with different radius and thickness, the above loads shall be multiplied by thefollowing factor:

t0.= / R�.=

For equipment in stainless steel or in special materials (Ni, Cu, Al, Ti alloys etc.), table values shallbe decreased by 25%.

For nozzles smaller than 3” no check shall be made, because relevant loads have to be consideredas negligible.For nozzles whose size is not listed in above table and in all cases where loads exceed reportedvalues, evaluation by the Equipment Engineer is required.For high pressure vessels the allowable nozzle loads shall be obtained from the manufacturer.

otorres

Note

It is recommended to specify in which standard or practice are based the values of this table.

Date post:	20-Feb-2016
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Specification for Piping Stress Analysis - REFERENCIA CRITERIO

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