81099215 Pipe Stress Analysis

PIPE STRESS ANALYSIS

REVISION DATE ORIG. BY APP. BY SIGNATURE

FOSTER WHEELER ENGINEERING STANDARD 01 June 99

D1 July 99

A. CLIPSTONE A. CLIPSTONE A. CLIPSTONE

A. CLIPSTONE A. CLIPSTONE

6960-8230-SP-0004 PAGE: 1 OF 32 REV: D1

D2

Contract:

1-14-6960/89

Client’s Name:

VIETROSS

Project Title:

VIETROSS REFINERY PROJECT

Project Location:

DUNG QUAT, VIETNAM

Doc. Sequence No:

760

Document Category:

CLASS 1

CONTENTS SECTION 1 2

SUBJECT PURPOSE SCOPE

3

REFERENCES

4

OUTLINE EXECUTION

5

ORGANISATION

6

BASIC RESPONSIBILITIES

7

GUIDELINES FOR STRESS ANALYSIS

8

ANALYSIS REQUIREMENTS

9

DETAIL STRESSING CONSIDERATIONS

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FOSTER WHEELER ENGINEERING STANDARD


ATTACHMENTS RD1

RD1

1. EXTENT OF ANALYSIS- Piping Connected to Equipment other than Rotating Machinery Air-coolers and Tanks 2. EXTENT OF ANALYSIS- Piping Connected to Rotating Machinery or Air Fin Coolers 3. EXTENT OF ANALYSIS- Piping Connected to Tanks (No Flexible

Joints) 4. EXPANSION COEFFICENTS 5. EXPANSION COEFFICENTS 6. NEMA CHECK DATA SHEET 7. STRESS LOOP SIZING FOR PIPERACKS 8. LOOP FORCES AND STRESSES

1.

PURPOSE

1.1

To define the working practices and responsibilities that relate to the stress analysis for the designed piping systems. To define the actions to be performed in order to satisfy these requirements together with the actions necessary to prove functional integrity of the piping systems in accordance with the relevant codes and standards.

2.

SCOPE

2.1

The scope of this standard is to establish the base level of stress analysis to be undertaken, by Contractor, for all process and utility piping systems. It outlines the primary working methods, design considerations, documentation, and guidelines associated with the required analysis in order to form the standard for adoption by Contractor.

2.1.2

The stress analysis of piping systems shall include all necessary supports, ancillaries, loads, pre-applied forces and the like needed to examine and resolve the loads in accordance with those stated as acceptable by the listed codes and standards




3.

REFERENCES

3.1

National Codes and Standards ASME B31.1 ASME B31.3 ASME B31.4 Hydrocarbons, ASME B16.5 API 610 API 618 Nema SM-23/ API 611 API 661 WRC 107 API 620/ API 650

3.2

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Power Piping Chemical Plant and Petroleum Refinery Code Liquid Transportation Systems for LPG, Anhydrous Ammonia, and Alcohols Steel Pipe Flanges and Flanged Fittings Centrifugal Pumps Reciprocating Compressors Steam Turbines Air Fin Coolers Welding Research Council Bulletin Storage Tanks

VietRoss Standards 6960-8300-SP-0001 Wind, Earthquake and Snow and Ice Loading 6960-8230-SP-0001 Piping Material Specification 6960-8230-SP-0002 Piping Layout and Design 6960-8411-SP-0001 Centrifugal Pumps for Heavy Duty Services 6960-8411-SP-0002 Positive Displacement Reciprocating Pumps 6960-8411-SP-0003 Positive Displacement Pumps - Controlled Volume 6960-8411-SP-0004 Special Purpose Centrifugal Compressors 6960-8411-SP-0005 Special Purpose Reciprocating Compressors 6960-8411-SP-0008 General Purpose Steam Turbines 6960-8411-SP-0009 Special Purpose Steam Turbines 6960-8411-SP-0021 Centrifugal Pumps for General Duty Services 6960-8480-SP-0001 General Requirements for Shell & Tube Heat Exchangers 6960-8480-SP-0002 General Requirements for Air Cooled Heat Exchangers 6960-8480-SP-0003 General Requirements for Double Pipe & Multi-Tube Heat Exchangers 6960-8480-SP-0004 General Requirements for Plate & Frame Heat Exchangers


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6960-8430-SP-0001 General Requirements for Welded, Unfired Pressure Vessels. 6960-8430-SP-0003 API Storage Tanks 4.

OUTLINE EXECUTION Contractor is responsible for the mechanical integrity of all the designed piping systems. Contractor shall demonstrate the above by under taking and providing the following requirements:

4.1

Specific Stress Analysis Procedure Contractor shall prepare and issue a Stress Analysis Procedure. This will take due account of the project, national and VietRoss standards as defined herein. The document should be based on the requirements of this standard, supplemented and amended where necessary to include all related design considerations. It shall be submitted to VietRoss for approval prior to the commencement of any stress analysis.

RD1

4.2

Review of Project Engineering Data Contractor shall review the Piping and instrument Diagrams, Line Classification List and the Basic Engineering Data Sheets for potential piping design problems and inconsistencies. Particular care shall be taken in the review of the Line Classification List, which forms the basic design document for all piping systems stress analysis.

4.3

Stress Critical Line List and Approval Index. Contractor shall prepare and provide the Stress Critical Line List. This is a summary and status document of all the lines requiring formal analysis, whether by computer or other means. Contractor shall prepare and complete a Line Stress Approval Index in order to establish that all the above lines and stress related components (including elements such as support springs) have been examined, checked and approved by Contractor’s Stress Engineer.

RD1

4.4

Equipment Specification




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Contractor shall review and (as necessary) comment on equipment standards/specification where these form part of the piping system analysis. (E.g. heavy duty base plates on pumps, all heat exchanger nozzles to have reinforcing pads, compressor nozzle loading 1.85 x NEMA as a minimum). 4.5

Initial Flexibility Checks The initial flexibility checks may be carried out by Contractor using recognised graphical means as nomographs and/or related charts, with particular attention being given to those lines contained within the project Critical Line List. Lines on this list should have specific stress input during routing.

4.6

Formal Analysis As a minimum, formal flexibility analysis shall be undertaken on lines (including terminations) as defined in the Critical Line List.

4.7

Equipment Nozzle Loading Contractor shall ensure the suitability of piping loads at the equipment nozzles (or equipment skid interfaces) and the support locations for inclusion in their overall design.

4.9

Civil and Structural Loading Contractor shall ensure the suitability and co-ordination of the design and structural loading for pipe support foundations required by all relevant civil and structural works.

4.10

Interface Piping Contractor shall liase, agree and formalise design basis at other contractor battery limits, packaged unit limits and at VietRoss interfaces. This includes piping, services and ductwork designed by others.

5.

ORGANISATION Contractor shall perform all stress calculation work employing highly competent stress engineers experienced in similar work and projects. In general, the personnel shall be in a group (task force) environment with the piping design team.


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6.



BASIC RESPONSIBILITIES Stress analysis forms an integral part of piping engineering, and as such, Contractor shall report progress and other prescribed administrative matters to representatives of, or directly to VietRoss.



RD1


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7.

GUIDELINES FOR STRESS ANALYSIS

7.1

Introduction

7.1.1

The Contractor shall ensure that piping systems are safe for all specified design conditions. These guidelines are concerned with the piping flexibility aspect of this function, other related activities include piping design for pressure containment.

7.1.2

This standard, by emphasising the need for demonstrating engineering integrity, does not seek to restrict the use of sound engineering judgement based on Contractor’s experience. Computer usage should be resorted to where accurate assessment of loading and stresses are essential for line approval or where an alternative (recognised) method of calculation, as identified in Contractor’s approved procedure, would be more costly in terms of time or resources. Where computer calculation is used, consideration shall be given to the form of input data, which must give verifiable results within the completed calculation report.

7.1.3

Whatever the method used for reviewing piping flexibility and stress calculation, the results should be clearly identified and documented for subsequent audit by either VietRoss or by a third party.

7.2

General

7.2.1

Piping systems may be subjected to many diverse load conditions. Stresses induced by pressure, weight of pipe, equipment vibration, fittings and fluids, external loadings such as wind loads, seismic loads, settlement, solar/frost temperature effects and thermal expansion and contraction are significant in the stress analysis of piping systems. Generally most piping movements are due to thermal expansion, but all the above criteria shall be taken into consideration during stress analysis.

7.2.2

Piping systems shall be designed to be adequately flexible and wherever possible this should be achieved by the natural flexibility of the pipework. If necessary the route of the piping should be modified (or expansion loops incorporated) in order to obtain sufficient flexibility. Only in exceptional cases where it is impractical to increase the system flexibility (to reduce the stress range to an acceptable level or to reduce equipment loading) should an expansion joint or similar be considered as for a design solution. The use of expansion joints shall require the prior written approval of VietRoss


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RD1



7.2.3

When carrying out a flexibility analysis, the worst process design conditions shall be considered, including steam-out. Practical engineering judgement shall be used to decide the worst load case scenario and consideration must be given to running the worst load case. Process conditions which give rise to impulse loading such as pressure surge, relief discharge reaction or two phase flow shall also be taken into account.

7.2.4

Strain sensitive equipment (vessels, heat exchangers, reactors, tanks, pumps and compressors) at which pipe systems terminate shall be considered rigid for pipe stress analysis. The loads shall be calculated at the vessel nozzle/shell interface for all classes of equipment with the exception of rotating machines, where the nozzle is recommended for inclusion within the pipework analysis and treated as rigid. 7.2.4.1. The acceptance or approval of nozzle loads shall be the responsibility of Contractor’s Specialist Equipment Engineer. 7.2.4.2. In the case of tanks, the nozzle loads shall be referred to Contractor’s Specialist Vessel Engineer for review. Design shall follow the requirements of API 650 unless otherwise stated within the listed documents. 7.2.4.3

In all cases Contractor shall be responsible for the structural integrity of piping flanges. Flange leakage calculations shall be performed as required by the relevant Code

7.2.4.4. Piping connected to machinery shall be flexible to ensure that the piping loads transmitted to the machine are acceptable under all design conditions. 7.2.5

Boundary conditions at other Contractor or VietRoss interfaces must be clearly defined before detail commencement of design work. This should include, but is not limited to, the movements, forces and pipe support provisions at boundaries. See also paragraph 4.10.

8.

ANALYSIS REQUIREMENTS

RD1 8.1

General All Systems shall be analysed in accordance with Attachments 1, 2 and 3. These out-line the methods of examination required for all piping systems covered by this standard and diagrammatically represent the potential need for computer or




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other analysis. Contractor shall develop these for all cases of pipe schedules and conditions within the detailed design. 8.1.2

Visual inspection or approximate calculation methods may be applied only if they are used in the range of configuration for which their adequacy has been demonstrated. Approximate calculations may include the use of approved charts, nomographs and simplified formulae. The objective of using these methods is to demonstrate that recourse to more precise methods is not required.

8.1.3

Acceptable comprehensive methods of analyses include computer and analytical methods, which include stress intensification and flexibility factors for all components other than pipe, and provide an evaluation of the forces moments and stresses caused by piping displacement.

8.2

Visual, Chart or Informal Checking Methods

8.2.1

Piping flexibility can be checked by visual inspection and the use of approved reference charts e.g. stress nomograph, expansion loop charts, or analogy. Piping loads on equipment shall be avoided by adding suitable guides, restraints and/or anchors.

8.2.2

At pumps having end suction nozzles it may be possible to restrain/anchor the piping close to the pump. However this restraint/anchor should not be more than 1 metre from the fixed point of the pump casing and should be designed such that adjustment can be made when bolting the pipe flange to the pump nozzle. Loads on the restraint/anchor must be minimised by the location of guides further upstream e.g. in the piperack. This design option should be used with care as poor support specification and installation can generate large forces.

8.2.3

Piping which connects the tube bundles of air cooler exchangers can be checked and the terminal loads evaluated usually by basic hand calculations. Loadings on structures can be estimated by approximate methods. Computer analysis may be necessary in the following cases:

8.2.3.1. Where items of equipment are particularly strain-sensitive, e.g. compressors and very thin walled vessels. 8.2.3.2. For large pipes, diameters greater than 24” NPS. 8.2.3.3. Where movements are large, particularly when due to extraneous causes e.g. differential settlement of foundations, overhead lines rising with tower expansion.


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8.3

Comprehensive Methods of Analysis

8.3.1

Before resorting to formal calculations and computer analysis, check that the proposed piping configuration is approximately correct by visual appraisal and by reference to an approximate method. If the stress in the pipe itself is the only criterion, further calculation may be unnecessary, but care must be taken, as the presence of components subject to intensified local stresses such as branches, and reduced size piping may cause stresses in excess of those suggested by the nomograph. In general, computer analysis will be required for that listed below. The listing is not intended to be exhaustive and address every eventuality, however and experienced, engineering judgement shall prevail. 8.3.1.1. Lines connected to strain sensitive equipment to evaluate the magnitude of the terminal loads with sufficient accuracy for final review by the specialist Engineers. Engineering judgement shall be used to decide as to which equipment should be treated as strain sensitive. 8.3.1.2. Rotating equipment with nozzles 2” NPS and above with a design temperature of 80 °C and above. 8.3.1.3.

Large diameter (24” NPS and above) or heavy wall pipes, and also lines with design conditions for ferrous and alloy piping above 350 °C and for Stainless Steel above 270 °C.

8.3.1.4. Thin walled vessels (e.g. corroded thickness less than 5mm) with a design temperature of 80 °C and above. 8.3.1.5. Heat exchangers with a design temperature of 80 °C and above. 8.3.1.6. Piping systems operating at temperatures minus 40 °C and below 8.3.1.7. All piping with a wall thickness greater than standard weight, considered on it’s individual case. 8.3.1.8. Where movements are large due to extraneous causes, e.g. differential settlement of foundation, etc.



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8.3.1.9. Piping which connects together the tube bundles of air-cooled exchangers. 8.3.1.10. Lines subject to large displacements imposed on them by the movements of other lines or equipment to which they are connected, even though they may be below the limits recommended 8.3.1.11.Jacketed pipework. 8.3.2

Computer Analysis - Normally, the computer input should include the following information:

8.3.2.1. contained.

Physical

characteristics

of

the

piping

and

fluid

8.3.2.2. Rate of expansion. 8.3.2.3. Terminal movements. 8.3.2.4. Details of restraints, including fixed supports, which will significantly affect vertical movement of the pipe. 8.3.3

Computer analysis for lines, which are likely to impose significant loads on equipment, are to include all relevant effects (e.g. pressure, weight, and thermal expansion). However, Contractor is cautioned that the computer analysis normally treats nozzle connections as rigid anchors so that very small deflections of pipe between supports may cause indicated bending moments at the nozzle which, in practice, will disappear with very small rotations.

8.3.4

The interpretation of computed forces and moments must take account of the movements from which they originate, and Contractor must make a distinction between loadings which are sustained over a large range of movement and can cause gross distortion, and secondary loading which cause only minor strains.

9.

DETAIL STRESSING CONSIDERATIONS

9.1

Temperature Conditions

9.1.1

The Line Classification List indicates for each line a design temperature and an operating temperature. Stress analysis shall be carried out on the basis of the design temperature. In instances where the design temperature is exceptionally high


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when compared with the operating temperature, Contractor should establish the mode of operation at the higher temperature and the extent to which the system is affected. Note: The ASME Code B31.3 does not permit an increase in allowable stresses in the piping for short-term variations above the normal design temperature. However, it may be possible to allow higher loads on equipment especially if that equipment is not itself subject to the higher temperature. 9.1.2

Steam Tracing - Tracing can cause the temperature of the line to rise above normal, during periods when the line is empty or when no flow occurs. Piping design must take this into account when calculating movements.

9.1.3

Steam Out - Lines in hydrocarbon service may occasionally be steamed out and pipe stressing must take into account the resulting rise in temperature. Note that the equipment is also steamed out and in the case of columns, the resulting vertical expansion may cause large movements in the connected piping, which may remain at ambient temperature.

9.1.4

Solar Radiation - Long straight uninsulated pipe runs, especially off-site pipelines may be subject to significant movements as a result of solar radiation. Due allowance shall be made for this.

9.1.5

Ambient Temperature - The minimum ambient design temperature will be given in the Project Basic Engineering Design Data (BEDD). This is the temperature, which is to be used as the basis for expansion and analysis purposes.

9.2

Equipment Considerations

9.2.1

Piping connected to pumps - Pipework at two-pump sets shall be analysed with both pumps in operation first. A further oneoff case, one pump in operation, one pump on standby shall be run after consideration has been given to which of the pumps operating will produce the worst case. The temperature of the line to the standby pump shall be considered as either: 9.2.1.1. 75% operating temperature where check valve bypass is specified. 9.2.1.2. Minimum maintained temperature where specified in line list. 9.2.1.3. Minimum ambient temperature.



RD1


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9.2.1.4. Where applicable the maximum piping load allowed at the operating pump nozzle shall conform to API 610. This is a pump manufacturer’s standard, which allows double the permitted piping loads (in accordance with Appendix F of that standard). This option may be noted in Engineering Std. 8411-SP-0001– ‘Centrifugal Pumps for Heavy Duty Services’ and Contractor shall ensure that compliance with this standard is being observed. For large pumps that are outside the scope of API 610, refer to NEMA Std SM23 (Mechanical Drive Steam Turbines) and the allowable nozzle loads have to be increased by at least a factor of 1.8. (Note this factor may be able to be increased on negotiation with the Vendor). Pumps which are purchased in accordance with Engineering Std. 8411-SP–0021 ‘Centrifugal Pumps for General Duty Services’, may not conform to API 610. Allowable loadings must be requested at an early date from the pump manufacturer. When in doubt about allowable piping loads on pump nozzles, the calculated loads resulting from the desired piping arrangement should be sent to the manufacturer for approval. In situations where space restrictions make it especially difficult to achieve satisfactory nozzle loadings the following measures can be considered: A bleed to maintain temperature in the stand-by pump piping thus reducing the differential expansion in the piping legs to the two (or three) pumps. Eliminating or reducing any difference in size between the pipe and the pump nozzle. Either case must be approved by VietRoss.

9.2.2

Turbine and Centrifugal Compressor Piping - Nozzle displacements for turbine and compressor nozzles should be obtained from the supplier. For turbines, minimum nozzle loads may be obtained from NEMA SM-23, whilst a factor of 1.85 may be applied to obtain minimum nozzle loads for centrifugal compressors. Refer to Attachment 6 - NEMA Check Data Sheet for calculation requirements. Note: Higher allowable loads for turbines and compressors may be obtained from the vendor.


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9.2.3



Air-Cooler Piping - For piping loads at air-coolers the Contractor should refer to API 661 and for equipment requisitions twice the load given by API 661 should be used. With multi-bundles it is generally advantageous to connect the piping inlet manifold as close as possible to the exchanger nozzles and allow thermal expansion to shift the tube bundles laterally. At ‘even-pass’ units the flexibility of the outlet piping must allow for this movement. At ‘odd-pass’ units the outlet piping must allow for a possible failure of a single fan thus causing a differential temperature along adjacent tube bundles. The exchanger manufacturer should be required to provide low friction pads under tube bundles as a matter of routine for all multi-bundle air-fin coolers. To limit the vertical pipe loads on the inlet nozzles it may be necessary to extend the air-cooler support steelwork upwards between the bundles in order to carry the weight of the manifold for both hydrostatic test and for operating (normally vapour) conditions. Should the force required to shift the tube bundles exceed the maximum allowed on the nozzles, the following alternative solutions may be considered: 9.2.3.1. Request the vendor to provide mechanical links between the tube bundles at the inlet header boxes so that expansion across the entire air-cooler matches that of the inlet-piping manifold. This device can only be used where distance between adjacent header boxes is minimal and expansion across both piping manifold and header boxes is identical. 9.2.3.2. Support the inlet manifold on a separate structure and connect it to the air-cooler inlet nozzles by pipe loops of adequate flexibility.

9.2.4

Transfer Lines from Heaters - These require special attention and a computer analysis should be considered as routine practice. The vendor usually specifies allowable loads conservatively on heater nozzles. If these cannot be achieved, the Contractor shall liase directly with the vendor and submit the calculated loads for further consideration by the vendor. Lateral movement of the connecting piping can, to some extent, be absorbed by allowing the terminal tubes to shift a small amount (approx. 25-mm). The vendor should be asked to include this feature in their design. Vertical movement of piping connections to horizontal tubes can be similarly




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incorporated in the heater design by pre-setting the tube upwards, i.e. lifting it off the nearest supports. Check also the location of the fixed ends of the tubes to determine the movement of the heater terminals and whether a change in the heater design would reduce the problems resulting from overall expansion of the pipe and tubes. Transfer lines carrying a mixed phase fluid can be subjected to severe vibrations. The Contractor shall check for this possibility and, if necessary, add restraints to prevent movement from this source. Depending upon the type and function of the heater, the contents of the transfer line may be vapour during operation, but liquid during start-up or shutdown when the operating temperature is less than normal. The design and location of supports to meet the two weight conditions must be taken into account when designing and analysing the transfer line. Information with regard to the weight of liquid and the temperature/pressure characteristics of transition to vapour phase shall be obtained from the process design 9.2.5.

Piping at Storage Tanks – Differential settlement at tanks is particularly important and data must be obtained prior to the design of piping on the following:

9.2.5.1.

Amount of settlement.

9.2.5.2.

The period of time over which settlement occurs. 9.2.5.3.Amount of settlement and recovery following construction and hydrotest.

that

occurs

When large storage tanks are filled, the walls bulge and nozzles located in the lower course are rotated downwards. Any restraint to this rotation by the stiffness of the connected piping will cause a stress in the tank shell, which must be limited to values defined by the Specialist Vessel Engineer. It is imperative for design to proceed that the values of tank bulge and nozzle rotation and the methods of calculation to be used are agreed early in the project. The definition of these values is the responsibility of the Specialist Vessel Engineer. The combined effects of settlement and nozzle rotation may suggest supporting the piping on springs. However, before pursuing this course a check should be made on the possibility of the line becoming drained during a normal operation cycle. If this should occur the supporting springs may impose an


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excessive upward force on the tank nozzle. Where the line can only be drained when the tank is out of service, instructions shall be issued for the springs to be locked before draining. 9.3.

Surge/Slug Flow

9.3.1.

Check the possibility of surge occurring in off-site lines as a result of valve closure. Install line stops at changes of direction to withstand surge forces and consequent movement of the pipe. The following are conditions that should be considered for slug flow: 9.3.1.1. Slug development due to start-up/shutdown. 9.3.1.2. Slug build-up in condensate lines. 9.3.1.3. Slug development in relief flare systems (liquid relief).

9.3.2.

A slug of liquid, with a mass (kg) and velocity (m/s), being driven along a piping system has a momentum, and if it travels around a sharp bend or elbow, there is a change in momentum. The following formula may be applied to calculate the force acting on elbows:

[ =pav5

(1)

where: p = density of fluid a = internal cross sectional area v = velocity of which slug is travelling [ = Resultant force as slug strikes elbow 2

It should be remembered that this force generated is an impact force and it is suggested that formula (1) should be factored by a dynamic load factor i.e.




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[ =2 x pav5 9.3.3.

A full dynamic analysis should not be attempted if a system is acting close to slug flow condition due to the complexity of predicting the ‘time period’ of slug generation. However, an attempt should be made to increase the first mode of vibration (natural frequency) to a value above 5Hz.

9.4.

Earthquake Forces

9.4.1.

Piping in earthquake zones must be designed on the basis that spring supports should be avoided.

9.4.2.

Lateral movement of the ground requires restraints to be added along the pipe. To calculate the horizontal force on these restraints multiply the dead weight by a factor dependent on the earthquake severity zone.

9.4.3.

A dynamic analysis may be necessary on sensitive lines subject to earthquake design. This technique should be carefully used, as it is generally an iterative process.

9.5

Wind Loading

9.5.1

VietRoss Engineering Standard 6960-8300-SP-001, ‘Wind, Earthquake and Snow and Ice Loading’ is aimed at the structural integrity of buildings and structures to ensure that surface areas that are exposed to wind, including pipes, are designed for. The piping code ASME B31.3 paragraph 301.5.2, ‘Wind’, states ‘The effect of wind loading shall be taken into account in the design of exposed piping. The method of analysis may be as described in ASCE 7-88, Minimum Design Loads for Building and Other Structures, or the Uniform Building Code.’ Therefore, wind loading should be considered on the following pipelines to ensure structural integrity of pipe support structures and vessel shells when the pipe outside diameter (including insulation thickness) is 400 mm and over: 9.5.1.1. Lines that are routed down towers, columns or vertical drums. 9.5.1.2. Inlet lines to Air-coolers.


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9.5.1.3. ‘Flare’ or ‘Run Down’ or similar lines when routed in exposed areas between process units and the flare stack. 9.5.1.4. Lines that are routed over and around exposed platforms such as top platforms on columns or high structures at elevations 10 m and above. RD1

9.6

Foundation Settlement

9.6.1

Differential settlement must be taken into account in piping stress analysis when the following values are exceeded: Pumps to piperacks Pumps to drums and storage tanks Pumps to shell and tube exchangers Pumps to columns Turbines to piperacks Shell and tube exchangers to piperacks Shell and tube exchangers to drums Shell and tube exchangers to columns Columns to piperacks Columns to air-cooler exchangers

5 mm 10 mm 10 mm 5 mm 5 mm 10 mm 10 mm 10 mm 15 mm 15 mm

9.6.2

Where it is necessary to design for greater settlements, the initial amount occurring during construction and testing may be ignored. In such cases it should be clearly noted that piping connections must be made after hydrostatic testing.

9.7

Rack Deflection

9.7.1

It is recommended that piperack deflections concur to the above criteria for modular design and a maximum of 5 mm should be adopted for the lateral deflection of piperacks.

9.8

Buried Piping

9.8.1

Buried piping will expand or contract with temperature changes in the flowing medium or the surrounding soil. This movement will occur regardless of the burial depth or the soil type. The total change in length of the pipeline is dependent on the soil fiction and the passive resistance.

9.9

Control Valve Piping

9.9.1

Control or let down valves cause vibrations in connecting pipework and may sometimes reach dangerous amplitudes or destructive frequencies. In general the connecting pipelines should be guided whenever possible to eliminate such large amplitude vibrations.




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Rigid attachments should be avoided if: 9.9.1.1. Pipelines are subjected to sonic vibrations with highenergy input. 9.9.1.2. Where the pipe wall tends to oval. 9.9.1.3. Wave patterns develop circumferentially. 9.10

Bowing of Pipe

9.10.1

Due to pipelines being subjected to unequal heating across the pipe wall along its length the pipe will bow. This type of bowing is unrelated to column instability resulting from compressive axial loads.

9.10.2

Bowing may occur when the flowing medium, which may be hot or cold, partially fills the pipelines or the sun’s radiation heats the top of large empty pipelines which lay close to frozen ground.

9.10.3

The requirement to include bowing in the analysis should be considered if the differential temperature across the pipe wall is 50 °C or greater.

9.11

Stress Loops

9.11.1

Stress loops within piperacks can be sized using nomograph methodology. Refer to Attachment 7 – Stress Loop Sizing for Piperacks

9.11.2

Refer to Attachment 8 – Loop Forces and Stresses for calculation requirements. Loads on piperack bents should be transmitted to the Civil Engineers to enable them to complete the piperack design.

9.12

Support Design

9.12.1

Contractor shall provide a comprehensive pipe support standard. This shall use stress loads calculated and integrate them fully with design range of the piping systems and the requirements of this standard. Contractor shall provide for design of support trunnions (including reinforcement as required) in accordance with the requirements of the codes and documents listed. Trunnion diameters shall normally be one pipe size down on line size.

9.12.2.

9.13

Branch Reinforcement


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To be in accordance with ASME 31.3. 9.14

Expansion Joints

9.14.1

In cases where it is impractical to increase the flexibility of a pipeline to reduce the stress range and/or termination loads to an acceptable level, the Specialist Stress Engineer may specify the use of bellows or expansion joints as a design solution. (See also paragraph 7.2.2.)

9.14.2

If it is found that an expansion joint is required then the technical requirements shall be identified and listed.

9.14.3

Contractor shall to obtain written approval for the use of expansion joints or flexible hoses from VietRoss prior to proceeding with the requisitions.

9.15

Spring Supports

9.15.1

Spring supports shall be avoided as an easy solution for piping which is affected by vertical thermal expansions or mechanical movements. An alternative is to reposition supports or re-route the piping. VietRoss approval is required for the use of spring supports.

9.15.2

If spring supports are necessary in a pump system, the pre-set reaction force is set to the value required when the system is filled with liquid. Prior to start-up this reaction could be applied to an empty piping system. If the pump or piping is unable to accept such loading the spring must be pre-set at a value between the piping system being full and empty. If this still fails to meet the acceptable loads, the piping will require re-routing.

9.15.3

Spring supports are ideal for situations where vertical expansions or mechanical movements are restricted by solid supports, which results in unacceptable reactions or stresses. Spring supports must be used on hot piping systems adjacent to pumps, turbines and compressors when solid supports prove to be unsatisfactory.

9.15.4

Care should be taken that springs are accessible for the release of ‘gags’ during commissioning.

9.16

Other Considerations



9.16.1


6960-8230-SP-0004 PAGE: 21 REV: D1

The following considerations have been included as an aide memoir to cover other specific areas of detailed analysis requirements. 9.16.1.1. Firewater systems, whereas these are not subject to high thermal loads they are often subject to large surge loads. The pipework must therefore, include adequate restraint.

RD1

9.16.1.2. Impulse loading to relief valve discharges venting to atmosphere. The Specialist Instrument Engineer normally determines relief valve forces after valve throat sizing. Note: For relief valve discharges relieving into a closed vent or flare header, impulse loadings can be ignored. Relief valve piping, however, still needs restraint but in this case analysis is not required. 9.16.1.3 Thin walled piping is to be considered for shortened spans. 9.16.1.4. Flare systems must be reviewed with consideration given to the full temperature range, and the possibility of slugging and shock loading criteria. Branch connections, tie-ins, for flare systems should be at 90 degrees for maximum strength for stress analysis. Unless process requirements dictate otherwise the following stress intensification factors should be applied:-

3

Where:

%

90 60 45 30

Degrees Degrees Degrees Degrees

SIF SIF SIF SIF


x x x x

1 1.25 2.25 3.5

6960-8230-SP-0004 PAGE: 22 REV: D1





6960-8230-SP-0004 PAGE: 23 REV: D1


ATTACHMENT 1 – EXTENT OF ANALYSIS Piping Connected to Equipment other than Rotating Machinery, Air-coolers and Tanks

Note: Chart is based on Standard Wall Thickness

∆T °C

2

400 ∆T ≥ 330 °C ∆T < 330 °C ∆T ≥ 230 °C ∆T < 230 °C

1 300

200

∆T ≥ 180 °C ∆T < 180 °C

∆T ≥ 80 °C ∆T ≥ 80 °C

3

100

2

0 0

2

4

6

8

10

12

14

16

18

20

3 Nominal Pipe Size (Inches)

22

24

∆T ≥ 230 °C

∆T ≥ 230 °C

LEGEND:

1

Indicates computer analysis required

2

Indicates chart/nomograph analysis is adequate

3

Indicates visual inspection is probably adequate


∆T ≥ 40 °C ∆T < 40 °C

6960-8230-SP-0004 PAGE: 24 REV: D1



ATTACHMENT 2 – EXTENT OF ANALYSIS Piping Connected to Rotating Machinery or Air Fin Coolers Note: Chart is based on Standard Wall Thickness

∆T °C 400

2 1

300

∆T ≥ 180 °C

200

∆T < 180 °C

2

100

3

∆T ≥ 80 °C ∆T < 80 °C

2

0 0

2

4

6

8

10

12

14

16

18

20

Nominal Pipe Size (Inches)

LEGEND:

1


2


3

Indicates visual inspection is adequate


22

24


6960-8230-SP-0004 PAGE: 25 REV: D1


ATTACHMENT 3 – EXTENT OF ANALYSIS Piping Connected to Tanks (No Flexible Joints) Note: Chart is based on Standard Wall Thickness

∆T °C 400

1

300 ∆T ≥ 230 °C ∆T < 230 °C

200

∆T ≥ 180 °C ∆T < 180 °C

2

100

∆T ≥ 80 °C ∆T < 80 °C

3

0 0

4

2

6

8

10

12

14

16

18

20

Nominal Pipe Size (Inches)

LEGEND:

1


2


3

Indicates visual inspection is adequate


22

24

6960-8230-SP-0004 PAGE: 26 REV: D1

RD1



ATTACHMENT 4 - EXPANSION COEFFICIENTS FOR CARBON STEEL Note: Material will be subject to temperature and stress limitations

DEG C -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

mm/M DEG C mm/M DEG C mm/M DEG C mm/M DEG C mm/M DEG C mm/M DEG C mm/M DEG C -0.32 100 0.92 200 2.2 300 3.61 400 5.16 500 6.81 600 8.49 700 -0.27 105 0.98 205 2.27 305 3.69 405 5.24 505 6.89 605 8.57 705 -0.22 110 1.04 210 2.34 310 3.76 410 5.32 510 6.98 610 8.65 710 -0.16 115 1.11 215 2.41 315 3.84 415 5.4 515 7.06 615 8.73 715 -0.11 120 1.17 220 2.48 320 3.91 420 5.49 520 7.14 620 8.81 720 -0.05 125 1.23 225 2.54 325 3.99 425 5.57 525 7.22 625 8.89 725 0 130 1.29 230 2.61 330 4.06 430 5.65 530 7.3 630 8.97 730 0.05 135 1.35 235 2.68 335 4.14 435 5.74 535 7.38 635 9.04 735 0.11 140 1.42 240 2.75 340 4.22 440 5.82 540 7.47 640 9.13 740 0.17 145 1.48 245 2.82 345 4.29 445 5.9 545 7.55 645 9.21 745 0.22 150 1.55 250 2.89 350 4.37 450 5.99 550 7.64 650 9.29 750 0.28 155 1.61 255 2.96 355 4.45 455 6.07 555 7.72 655 9.37 0.33 160 1.67 260 3.03 360 4.52 460 6.15 560 7.81 660 9.45 0.39 165 1.74 265 3.1 365 4.6 465 6.23 565 7.9 665 9.54 0.45 170 1.8 270 3.18 370 4.68 470 6.31 570 7.98 670 9.62 0.51 175 1.87 275 3.25 375 4.76 475 6.4 575 8.06 675 9.71 0.56 180 1.94 280 3.32 380 4.84 480 6.48 580 8.15 680 9.79 0.62 185 2 285 3.39 385 4.92 485 6.57 585 8.23 685 9.88 0.68 190 2.07 290 3.46 390 5 490 6.65 590 8.32 690 9.96 0.74 195 2.14 295 3.54 395 5.08 495 6.73 595 8.41 695 10.04 0.8 0.86


mm/M 10.13 10.21 10.29 10.38 10.46 10.54 10.63 10.71 10.8 10.88 10.97


RD1


6960-8230-SP-0004 PAGE: 27 REV: D1

ATTACHMENT 5 - EXPANSION COEFFICIENTS FOR A312 TP321 STAINLESS STEEL

Note: Material will be subject to temperature and stress limitations

DEG C -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

mm/M DEG C mm/M DEG C mm/M DEG C mm/M DEG C mm/M DEG C -0.49 100 1.35 200 3.1 300 4.93 400 6.83 500 -0.41 105 1.43 205 3.19 305 5.03 405 6.93 505 -0.33 110 1.52 210 3.28 310 5.12 410 7.03 510 -0.24 115 1.61 215 3.37 315 5.21 415 7.13 515 -0.16 120 1.69 220 3.46 320 5.31 420 7.23 520 -0.08 125 1.78 225 3.56 325 5.4 425 7.32 525 0 130 1.87 230 3.65 330 5.5 430 7.42 530 0.08 135 1.95 235 3.74 335 5.59 435 7.52 535 0.16 140 2.04 240 3.83 340 5.68 440 7.62 540 0.25 145 2.13 245 3.92 345 5.78 445 7.72 545 0.33 150 2.22 250 4.01 350 5.87 450 7.82 550 0.41 155 2.3 255 4.1 355 5.97 455 7.92 555 0.5 160 2.39 260 4.19 360 6.06 460 8.01 560 0.58 165 2.48 265 4.28 365 6.15 465 8.11 565 0.66 170 2.57 270 4.37 370 6.25 470 8.21 570 0.75 175 2.66 275 4.47 375 6.34 475 8.31 575 0.83 180 2.75 280 4.56 380 6.44 480 8.41 580 0.92 185 2.84 285 4.65 385 6.54 485 8.51 585 1 190 2.92 290 4.75 390 6.64 490 8.61 590 1.09 195 3.01 295 4.84 395 6.74 495 8.71 595 1.18 1.26


mm/M DEG C 8.81 600 8.92 605 9.02 610 9.12 615 9.23 620 9.33 625 9.43 630 9.53 635 9.64 640 9.74 645 9.84 650 9.94 655 10.04 660 10.14 665 10.25 670 10.35 675 10.45 680 10.55 685 10.66 690 10.76 695

mm/M DEG C 10.86 700 10.96 705 11.06 710 11.17 715 11.27 720 11.38 725 11.48 730 11.58 735 11.68 740 11.78 745 11.89 750 11.99 755 12.09 760 12.19 765 12.29 770 12.39 775 12.49 780 12.59 785 12.7 790 12.8 795

mm/M DEG C 12.9 800 13 805 13.1 810 13.2 815 13.31 13.41 13.51 13.61 13.71 13.82 13.92 14.02 14.12 14.23 14.35 14.46 14.58 14.7 14.81 14.93

mm/M 15.04 15.16 15.29 15.41

6960-8230-SP-0004 PAGE: 28 REV: D1



ATTACHMENT 6 – NEMA CHECK DATA SHEET TYPICAL DATA SHEET



PIPING ENGINEERING

VIETROSS

NEMA CHECK DATA SHEET

FOSTER WHEELER ENERGY LIMITED

Fy Fz

Mz

My

Fx Parallel to Turbine Shaft

+ ve system

Fx

Fz Perpendicular to Turbine Shaft

Mx

1. FORCES AND MOMENTS AT NOZZLE FLANGE FACES Node Nozzl Nozzle e Dia. No. No. (inch )

Tota l

D

Area

Fx

Fy

Fz

Mx

My

Mz

F

3F+M

M

2

(inch (inch) ) 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0

<=500 0 D OK 0 0 0 0

K

Stres s Calc No.

OK OK OK OK

Note: Moments and Forces to be in Foot Pounds and Pounds 2

2

2

F=

Fx + F y + Fz

M =

Mx + My + Mz

2

D = Nom.Dia

2

2

if Nom.Dia ≤ 8"

16 + Nom .Dia if Nom .Dia > 8" 3 π 2 Area = × ( Nozzle bore Dia ) 4

D=

FWEL * * * * / 1


g:\piping\form\2101a6


6960-8230-SP-0004 PAGE: 29 REV: D1


ATTACHMENT 6 – NEMA CHECK DATA SHEET (CONTINUED) TYPICAL DATA SHEET



PIPING ENGINEERING

VIETROSS

NEMA CHECK DATA SHEET


2. FORCES AND MOMENTS AT CENTRELINE OF EXHAUST FLANGE FACE CONNECTION Node No.

Nozzle No.

Fx

Fy

Fz

M

M

x

y

M

z

Line No.

Sum 0 0 0 0 0 0 Allowable 50 D c 125 D c 100 D c 250 D c 125 D c 125 D c = 0 0 0 0 0 0

Area Dia (inch)

Dc Fc Mc Actual Allowable Factor 'K'

0 0 0 0 0 #DIV/0!

Note: Moments and Forces to be in Foot Pounds and Pounds

Dc =

Total Area π 4

up to 9"

 18 + Equiv . Dia  Dc =   3   Fc = Mc =

2

2

Σ Fx + Σ F y + Σ Fz 2

over 9" 2

2

ΣM x + ΣM y + ΣM z

Actual = Fc +

2

Mc 2

Allowable = 125 D c Factor ' K ' =

Actual Allowable

Additional Moment Due to Transposed Forces:

M x = + ( F y × Z ) − ( Fz × Y ) M y = − ( F x × Z ) + ( Fz × X ) M z = + ( Fx × Y ) − ( F y × X ) FWEL * * * * / 2



6960-8230-SP-0004 PAGE: 30 REV: D1



ATTACHMENT 7 – STRESS LOOP SIZING FOR PIPERACKS

TYPICAL NOMOGRAPH



6960-8230-SP-0004 PAGE: 31 REV: D1


ATTACHMENT 8 – LOOP FORCES AND STRESSES

TYPICAL DATA SHEET



VIETROSS

PIPING ENGINEERING LOOP FORCES AND STRESSES


Page 1 of 1

G= W= A

FX

FX H=

R

CL

B ½G

6m (min )

h=

tR r2

6m (min)

S=

k=

β( SIF Inplane ) =

1.65 h 0.9 2

h3 L = 2π RK + 2 H + G − 8R Y = (π RK +W + H − 4 R ) H / L 2

I X = ΣAA , BB ,CC −Y L Where:

( 2W + H − 6 R ) H 2 2 ( H −2 R) 3 BB = 6 AA =

CC =[( H 2 +3R 2 − 2 HR )

π 4

+ HR − 2 R 2 ]4 RK

EC I ∆S 10 5 I X E FX ( HOT ) = H FX EC FX =

σMAX

A

= [( H −Y ) FX ]β / Z if G ≥ 2W

σMAX

B

= Y FX β / Z if G < 2W

FWEL ****/ 1



6960-8230-SP-0004 PAGE: 32 REV: D1



ATTACHMENT 8 – LOOP FORCES AND STRESSES (CONTINUED) TYPICAL DATA SHEET



PIPING ENGINEERING

VIETROSS

LOOP FORCES AND STRESSES


Page 2 of 2

Line No: Input

Fill in this section only

Nominal Size

inches

Wall thickness

inches

Calculation

I

inches

4

Z

inches

3

Material

I

0 cm 4

Z

0 cm 3

h

#DIV/0!

K

#DIV/0!

β (SIF in)

#DIV/0!

Temperature

degC

∆s

∆

mm/m

L

#DIV/0!

m

S

m

Y

#DIV/0!

m

Ec

MN/m

2

2

Y *L

Eh/Ec

#DIV/0!

3

m

AA

0 m3 0 m3

Relbow rad

m

BB

H

m

CC

G

m

W

m

Allowable Force

N

Allowable Stress

MN/m

Ix

0 mm

3

#DIV/0!

m

#DIV/0!

m

3

2

Result Fx Fx HOT σ

#DIV/0! #DIV/0! #DIV/0!

MAX

N N MN/m

2

#DIV/0! #DIV/0! #DIV/0!

FWEL ****/ 1



81099215 Pipe Stress Analysis

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