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Piping Stress Analysis Review
Document Responsibility: CSD/MED/Piping Unit
Saudi Aramco DeskTop Standards
Table of Contents
1
Scope... 2
2 Conflicts and Deviations... 2
3
References... 2
4 Required Documents for the Review... 3
5 Review of the Design Basis... 3
6 Review Computer Stress Analysis Modeling... 4
1
Scope
1.1
The objective of this best practice is to provide a methodology for reviewing
electronic piping stress analysis files, stress analysis that are generated by design
agencies/offices for Saudi Aramco new projects or existing piping
modifications.
1.2
This best practice is governed by the definitions and mandatory requirements of
SAES-L-120 “Piping Flexibility Analysis”.
1.3
This best practice is intended to be used by Saudi Aramco Engineers who are
directly involved in design review or approval; mainly CSD, PMT and
Operation Engineers.
2
Conflicts and Deviations
2.1
Conflicts with Mandatory Standards
In the event of a conflict between this Best Practice and other Mandatory Saudi
Aramco Engineering Requirement, the Mandatory Saudi Aramco Engineering
Requirement shall govern.
2.2
Disclaimer
This Best Practice is being provided for the general guidance and benefit of
Saudi Aramco engineers and operating facilities. The information or material
contained here will not release the users from the responsibility of safeguarding
and controlling their operations within Saudi Aramco established guidelines
such as GI’s and engineering standards.
3
References
This Best Practice is based on the latest edition of the references below, unless
otherwise noted.
3.1
Saudi Aramco References
Saudi Aramco Engineering Standards
SAES-A-112
Meteorological and Seismic Design Criteria
SAES-L-100
Applicable Codes & Standards for Pressure
Piping Systems
American Society of Mechanical Engineers
ASME B31.1
Power Piping
ASME B31.3
Process Piping
ASME B31.4
Pipeline Transportation Systems for Liquid
Hydrocarbon and Other Liquids
ASME B31.8
Gas Transmission and Distribution Piping
Systems
4
Required Documents for the Review
To be able to conduct a thorough review of piping stress analysis calculations, the
below documents are required:
1)
Safety Instruction Sheet (SIS) of each pipe
2)
Process and Instrumentation Diagram (P&ID) showing all lines
3)
Piping isometric drawings (ISO)
4)
Pipe Stress isometrics
5)
Electronic “Computational Piping Stress Analysis” input files
6)
Expansion Joints data sheets (if applicable)
7)
Spring supports/hangers data sheets (if applicable)
8)
Equipment nozzles allowable per the manufacturer or code(if applicable)
5
Review of the Design Basis
Before stating the review of the design calculations, review of the design basis
documents shall be completed to verify the accuracy of the design parameters that are
used in the calculations, a detailed check list can be found in Appendix A.
5.1
Safety Instruction Sheet (SIS)
SIS is the basis for all the design parameters; the SIS includes detailed
information on Line identification, piping data, operating and design conditions.
5.2
Piping Isometric Drawings (ISO)
The piping isometric provides the actual piping layout, support type and locations,
piping material specification and information to the connected equipments.
5.3
Stress Isometric
The stress isometric is the piping model that shows all equipments, node no.,
material specifications, pipe restraints and other information that are required to
perform the analysis utilizing stress analysis program.
6
Review Computer Stress Analysis Modeling
The quality of the calculation results depends mainly on the accuracy of the input file.
All input parameters are important. However, this best practice is highlighting the most
critical item that the reviewer needs to check/verify as minimum. These items are
addressed in the check list Appendix-A.
Note: the commonly used stress analysis software within Saudi Aramco is CAESAR II, if other
stress analysis software is being reviewed, the reviewer shall request access to the used stress analysis software.
6.1
Load Combinations
When reviewing the computer stress analysis modeling, it is important to verify
if all the possible operational seniors are analyzed, this can result in several load
combinations for the same piping system, each load combination is at different
operational conditions.
Example:
When we have two pumps, pump (1) and Pump (2), one is normally operating
and one is a stand-by, the following load conditions should be considered:
Table 1 – Load Combinations
Pump 1 Pump 2
Load Condition 1 Running (Hot) Running (Hot)
Load Condition 2 Running (Hot) Stand By (Cold)
Load Condition 3 Stand By (Cold) Stand By (Cold)
Similarly in you have three pumps Pump (1), (2) & (3), two are operating and
one is stand by, the following load conditions should be considered:
Pump 1 Pump 2 Pump 3
Load Condition 1 Running (Hot) Running (Hot) Running (Hot)
Load Condition 2 Running (Hot) Running (Hot) Stand By (Cold)
Load Condition 3 Running (Hot) Stand By (Cold) Running (Hot)
Load Condition 4 Stand By (Cold) Running (Hot) Running (Hot)
6.2
Review Calculation Results
The last phase in the review process is evaluating the calculation results; the
purpose of this evaluation is to see if stress, deflection and displacement are
within allowable.
6.2.1 Maximum Horizontal Displacement
At any point of the piping system, and for any load combination,
horizontal displacement shall be within the limit per the design criteria.
The following is a recommended practice:
1)
In the process unit the maximum movement at each side of the loop
should not be more than 6 inch.
2)
In the offsite area, the maximum movement at each side of the loop
should be no more than 12 inch.
3)
The guideline for the thermal movement at the corner when pipe
changes direction should be limited to a maximum of 6 inch in the
process area and 10 inch in the offsite area.
6.2.2 Equipment Nozzle Loads
The reviewer shall verify that all Equipment nozzel loads are qualified
per the vendor’s allowable or per the applicable code or standard or such
as:
NEMA SM23 Evaluates piping loads on steam turbine nozzles
API 610
Evaluates piping loads on centrifugal pumps
API 617
Evaluates piping loads on centrifugal compressors
API 618
Evaluates piping loads on reciprocating compressors
API 661
Evaluates piping loads on air-cooled heat
exchangers
API 560
Evaluates piping loads on fired heaters
WRC 107
Evaluates the vessel stresses in the immediate
vicinity of a nozzle
WRC 297
Computes stresses in the nozzle in the vessel
(evaluation of stresses in cylinder-to-cylinder
intersections)
Revision Summary
Appendix A – Pipe Stress Analysis Check List
Reviewer’s Name:Calculation No. Including BI No. Review Date:
Item Document
Title Description of item Comments
1 SIS Is the code used in compliance with SAES-L-100?
2 SIS Is the wall thickness calculation utilizing the applicable code? 3 SIS Is the hydrotest pressure calculation per SAES-L-150? 4 SIS Is the design temperature vs. Material allowable based on the
ASTM and the applicable code?
5 Piping
Isometrics
Does the piping and fittings material specification match the information on the SIS?
6 Piping
Isometrics
Does the Piping Iso. Include all valves/equipments that are shown on the P&ID for that line?
7 Stress
Isometric Does the stress Iso match the routings of the piping isometric?
8 Stress
Isometric
Does the stress Isometric drawing include node numbering for computer stress analysis modeling?
9 Stress
Isometric
Does the stress Isometric drawing include dimensions per the piping isometric?
10 Stress
Isometric Does the stress Isometric drawing include material specifications?
11 Stress
Isometric
Does the stress Isometric drawing include insulation type and thickness?
12 Stress
Isometric
Does the stress Isometric drawing include details, type and locations of the restraints?
13 Modeling Are all equipment nozzles are identified as anchors with the equipment’s thermal expansion? 14 Modeling Are all pipe supports and restraints are modeled per the stress
isometric?
15 Modeling Is all pipe support friction factor as per SAES-L-120? 16 Modeling Is the thermal expansion of the equipment considered in the
modeling?
17 Modeling Is the analysis being terminated (stress analysis boundary) at an anchor or at least at a three way restraint?
18 Modeling Are the spring supports modeled correctly (variable, constant, preloading, spring rate….) ? 19 Modeling Are the expansion joints modeled correctly (type, spring rates, displacements…)?
Item Document
Title Description of item Comments
20 Modeling
Are all fittings such elbows, tees, branches,… modeled with the applicable SIF “stress intensification factors”? And if the analysis uses SIF other than those in the applicable code, supporting calculation shall be included.
21 Modeling Does the code that is used match the SIS data
22 Modeling Is the design pressure that is used match the SIS data? 23 Modeling Is the design Temperature that is used matching the SIS data? 24 Modeling Was wind load condition considered in the Model?
25 Modeling Was Seismic load condition considered in the Model? 26 Modeling
Do the load combinations represent all the possible scenarios of operations (design condition, operating condition, hydrostest condition)? See Paragraph 6.1
27 Modeling If the system will be subjected to steam out, was the steam out considered as a load condition?
28 Modeling
Is the modeling of the supports connected to the equipments (Pressure Vessels, tanks…) per the computer Stress analysis technique ?
29 Modeling Are the Differential settlements considered in the modeling? 30 Modeling Are the units consistent that are used in the model?
31 Modeling Is the model considering flexible nozzles?
32 Modeling Did the model utilize the program database for material specifications?
33 Modeling Is the Fluid density used corresponds to the service?
34 Modeling Are the weights of components such as valves, flanges, … etc including bolts inputted correctly?
35 Calculation Results
Are the Maximum stresses for all cases including the combined stress meet the code allowable?
36 Calculation Results
Are the Maximum vertical displacements at any point for any load combination higher than 5/8”?
37 Calculation Results
Are the Maximum horizontal displacements at any point for any load combination within the limit per the design criteria? See Paragraph 6.2.1
38 Calculation Results
Are all Equipment nozzle loads qualified per the applicable code or standard or with-in the vendor’s allowable? See Paragraph 6.2.2 39 Calculation
Results Are the Spring hanger reports match the spring data sheets? 40 Calculation
Results
Are the Expansion Joints displacements and stresses match Expansion Joint data sheets?
