Literature survey
The safety of oil and gas flowline has increasingly considered day by day to their vulnerability.
flowline play a very critical role in the transportation of oil and natural-gas. As they have become
the veins of oil industries, the productive design and analysis became more important. This
made them more vulnerable to terrorist attacks. Although it is impossible to design flowline to
withstand any conceivable damage due to external (terrorist attacks, seismic effects) and
internal effects (design and manufacturing defects), it is possible to improve the performance of
flowline. By understanding the design criteria, it saves lots of money and more over human lives
and also protects the product in flowline, which cannot be recovered and which is more and
more scares day by day. This research aims:
1)
To understand the different types of flowline damages, reasons for their occurrence and
their effects on the flowlines, such as mechanical damages, material defects, cracks,
manufacturing defects.
2) To understand the explosions in flowlines, internal or external explosions and seismic
distress.
3)
To do research and literature review in analytical and numerical methods which allow
researching the influence of shock waves (explosions, seismic).
4)
To develop description of experimental research of flowlines subjected to shock waves
(explosions, seismic).
5)
To establish an effective methodology (develop mathematical model) to study the risk
management in flowline, exploitation which can be subjected to such conditions like shock
waves (caused by explosions, seismic, as well as mining activities) on flowline systems
(buried, on surface, or underwater).
6)
to establish criteria for risk management. This paper includes a review of the related
literature covering the first two goals.
Abstract
Geological circumstances along long distance pipelines are complex. The geometrical
properties such as diameter, thickness, span length considered during the design and analysis
of the piping layout. The variation of the pipe material density with respect to change of
pressure and temperature of the operating medium used to vary the span length between the
supports and the number of supports optimized. The variation of the pipe material density with
respect to change of pressure and temperature of the operating medium used to vary the span
length between the supports and the number of supports optimized.
A stress analysis model of pipelines was developed. Because of the CAESAR II, software used
to analyze the stress and displacement of a section of parallel oil and gas pipelines that run
through above ground and underground and stress and displacement distribution laws drawn
from the analyses.
The project focuses on stress analysis that performed for flowlines that is move from the original
location due to more stress and the less flexibility. Stress analysis and identification of piping
problems by ensuring that weight, thermal, and pressure stresses are at acceptable levels
specified in engineering design standards. Provide safe pipe support in pipeline based on the
loads given by the stress analysis report and recommendations. In vigorously producing oilfield
industry, flowlines connect to a single wellhead. Their determination is to move the raw fluid
product from the wellhead to the gathering lines. They carry crude oil, gas, water and sand.
Normally no more than 8” diameter in size.
Based on the research, the company trying to analyze the flowline failures, flowline stresses
and up grading the material by changing even size, shape, model even though mechanical
properties.
Table of Contents
Abstract ......................................................................................................................................................... 1
Nomenclature ................................................................................................................................................ 4
1.
Introduction............................................................................................ Error! Bookmark not defined.
3.2 Design Process ............................................................................. Error! Bookmark not defined.
2.2 Pipe failure Analysis .................................................................................................................. 12
2.3 Piping Stress Analysis .............................................................................................................. 13
CAESAR II Calculation .................................................................................................................... 15
Manual Calculation Result. ............................................................................................................. 19
4.2. Result and Analysis of CAESAR II. ....................................................................................... 20
5.1 Conclusion .................................................................................................................................. 22
5.2 Recommendation ...................................................................................................................... 22
List of figures
List of Tables
Nomenclature and abbreviation
Manual Calculation:
The computed stress range, SE in piping system shall not exceed the allowable displacement stress range,
SA (ASME B31.3)
Allowable Displacement Stress for Thermal Expansion:
𝑆𝐴 = f (1.25 𝑆𝑐 + 0.25 𝑆ℎ )
3.1
Where:
𝑆𝐴 : Allowable Displacement Stress Range.
𝑆𝑐 : Allowable stress of pipe on minimum working temperature.
𝑆ℎ : Allowable stress of pipe on maximum working temperature.
f: Stress range factor.
Axial Load
Normal Stress in Axial Direction
𝑆𝐿 = 𝐹𝐿 / 𝐴𝑚
Where:
𝑆𝐿 : Normal Stress.
𝐹𝐿 = Axial Force
𝐴𝑚 = π (𝑑𝑜 + di) t / 2 (Based on average diameter)
= π (𝑑𝑜 t) (Based on outer diameter)
3.2
Internal / External Pressure
𝐹𝐿 = P (π𝑑𝑖 2/ 4)
Axial Stress
3.3
𝑆𝐿 = P 𝑑𝑜 / (4t)
P = Pressure.
t = Thickness of the pipe.
𝑑𝑜 = Outer diameter.
𝑑𝑖 = Inner diameter.
Bending Load
Bending moment for practical pipe configurations 𝑀𝑚𝑎𝑥 = w 𝐿2 / 10
The maximum. Tensile stress 𝑆𝐿 at outer radius = Mb 𝑟𝑜 /I = Mb / Z
Where (Z = I/𝑟𝑜 ) is the section modulus of the pipe.
Moment of inertia of the pipe cross-section I = (𝑑𝑜 4- 𝑑𝑖 4) /64
𝑟𝑜 = Outer Radius
3.4
Introduction:
Once oil and gas are located and the well is successfully drilled and completed, the
product must be transported to a facility where it can be produced/treated, stored,
processed, refined, or transferred for eventual sale.
The well flowline, or simply flowline, is the first “pipeline” system connected to the
wellhead. The flowline carries total produced fluids (e.g., oil, gas, and production water)
from the well to the first piece of production equipment, typically a production separator.
The flowline may carry the well-production fluids to a common production battery, a
gathering pipeline system, process facility, or other.
The transmission pipeline is a “cross-country” pipeline that is specifically designed to
transport petroleum products long distances. The transmission pipeline collects the
specific petroleum products from many “supply” sources along the pipeline (such as
gathering pipelines) and “delivers” the product to one or more end users. As the world
population is growing, the demand for pipeline networks to transport the various fluids is
increasing. There are many hazards happening during the transportation due to the
failure of the pipeline. The failure happened because of the more stress developed in
the line due to the operational problems and other problems also.
Design of the piping system is essential to ensure that the piping well supported and
does not fall or deflect under its own weight. The deflections controlled, when thermal
and other loads are applied. Thermal expansion always creates the stress of the piping
system. The great challenge is to provide the reasonable flexibility to absorb the thermal
expansions. Determine the support span, pipe flexibility to compensate thermal stress
and structural analysis.
This analysis will help to provide safe pipe support during design layout and construct in
off plot piping. This analysis will help industrials plant to plan the maintenance schedule
and enchants it increase or extend in operating life of the operating plants. In addition, it
can also minimize the cost spend unnecessary maintenance and shutdown of the
operating plants.
Underground oil and gas pipelines made of under pressure, and when damage
happens, the consequences can be disastrous. According to the results of Caesar II
software, the stress and movement of underground oil pipelines in high and steep
slope areas drastically reduced and the safety greatly enhanced.
Water hammer in piping systems results in unstable forces, particularly between
changes in direction such as elbow pairs, and changes in area such as valves, reducers
and other inline components. Water hammer event caused by the partial closing of a
valve in a relatively simple system. The hydraulic transient analysis performs using AFT
Impulse™, and the mechanical system response evaluated using Caesar II pipe stress
analysis software.
The load received by piping systems can be reduce by making adequate piping
flexibility, so all the loads can be transmitted homogenously throughout the pipe without
load concentration at certain point. The analysis performed using Caesar II software
based finite element method.
A general problem identified with the oil-gathering Flowline for optimum production the
line failure happened due to over stress or corrosion and any other defects, it will also
lead to the hazardous situation around the place and major environmental issues. There
is an evidence that many of the production losses happened due to pipe line leakages
and heavy loss due to the unavoidable regular maintenance.
The different sources are generating the stress in the piping system, which is Weight,
internal/external pressure, temperature change, occasional loads due to wind and force
due to vibration.it is important to analyze the systems in the operation conditions,
namely the loads on the supports and the displacements. The determination of the
loads caused by the thermal expansion is a much more complex task. There are many
hazards happening during the transportation. Hazardous properties of the products
transmitted through these pipelines, a ruptured pipeline has the potential to do serious
environmental damage.
Aim of the research
The main objective of this project is to study and analysis of oil gathering flowline for optimum
production. This analysis to help to identify the problems and avoid the impact. The detailed
objective of the project includes:
•
To analysis, the stresses occurring in produced oil piping for safe pipe support
design.
•
To minimize the cost of Re-Design and Re-Analysis.
•
To minimize/ avoid shutdown during operation & producing oil period.
•
To ensure structural flowline integrity.
Summery;
Gathering Flowline:
Gathering flowline are used to deliver the oil or gas product from the source or reservoir
to processing plants or storage tanks. These are commonly fed by ‘Flowlines’, each
connected to individual wells in the ground. Additionally, subsea pipes used for
collecting product from deep water production platforms are included in this category.
Typical products carried by gathering flowline include; natural gas, crude oil (or
combinations of these 2 products), natural gas liquids, such as ethane, butane and
propane. In a gathering flowline, raw gas is usually carried at pressures of
approximately 600- 800 psi.
Sizes of flowline in Oil & Gas Industry:
Compared to other flowlines, lengths in this category are relatively short – approximately 200
meters long. They are typically much smaller than transmission flowline, usually under 18”
diameter (but for crude oil typically 2 – 8”), however, recent developments in shale production
have seen gathering lines are being used with diameters as large as 20”.
Material chosen to design flowline:
In order to enhance type of flowline material, company has decided to select the best
material based with what kind of production dealing with and what kind of project deals
to produce the hydrocarbon from the source/ reservoir to the surface to minimize the
failure or shutdown the filed. The existing fluid coming with mixture percentage of water
and other effectives such hydrogen sulfide H2S that can cause damage to the material
itself.
Factors that affect the material;
•
•
•
•
•
•
Corrosion
Erosion
Collapsing
High Temperature
Blasting
And other factors
As pear dissuasion to select the right material to design flowline that dealing based with
the client requirement, Carbon Steel is the best selection.
In this chapter identification of the problem of existing flowline move from the original location and
the line running with some of the temporary supports has been presented. The objectives and
scope of the project which is about the problems facing the oil gathering flowline during the
operation is also presented. Most of the failure studies discuss with the failure analysis and the
project methodology is to perform the stress analysis using CAESAR II software.
•
CAESAR II software:
Is the Pipe Stress Analysis standard against which all others are measured and compared? The CAESAR II
spreadsheet input technique revolutionized the way piping models are built, modified, and verified.
CAESAR II was the first pipe stress program specifically designed for the PC environment. The interactive
capabilities permit rapid evaluation of both input and output, thereby melding seamlessly into the
"design - analyze" iteration cycle.
CAESAR II incorporates a wide range of capabilities, from numerous piping codes, to expansion joint,
valve & flange, and structural databases, to structural and buried pipe modeling, to equipment and
vessel nozzle evaluation, to spectrum and time history analysis. Most of the features of CAESAR II are
available at a keystroke, but at the same time are not imposed upon the analyst.
A menu-driven scroll and select interface provides logical options when and where expected. Contextsensitive help provides instant technical assistance for each data field, with expected units. Data values
presented in the help screens are automatically presented in the current set of units to aid input.
The customization options of CAESAR II have been driven by user requests, code changes, and the need
to benchmark older, existing systems and their initial design. Many of these customization options
enable newer analysis techniques appearing in current literature.
As with all Hexagon PPM products, CAESAR II is continuously maintained and improved by the
engineering staff. The engineering staff of Hexagon PPM have worked in industry, for engineering and
consulting firms. This experience not only guides program development, but provides users with
knowledgeable support. This allows CAESAR II to work the way a typical engineer thinks and solves a
problem. This also means that the technical support provided to users by the engineering staff is almost
instantaneous. Users talk straight to the developers, ensuring an accurate and timely answer.
Program revisions incorporate additional capabilities addressing both technical and operational items.
Users are encouraged to suggest improvements that would help their day to day usage of the software.
See the enhancement list for details of capabilities added for each release of the CAESAR II program.
Operational Features
Menu / Spreadsheet Interface
The menus are set up to present the available program options in a logical order, when they are needed.
Menus govern the overall flow of control throughout the program.
The input spreadsheets provide concise prompts for input data. The piping spreadsheet duplicates
"elemental" data values forward to succeeding elements as the user defines them. When appropriate,
databases can be accessed to obtain values for valves, flanges, and expansion joints. If desired, an
expansion joint modeler can be invoked to build the necessary spreadsheets (with the appropriate tiebar connections) to accurately simulate a variety of expansion joint styles.
CAESAR II does not enforce artificial coding rules on the user during model construction. Models can be
started anywhere and can continue in any direction from tees or anchors.
The unique List Processor provides a concise method to review specific data sets, for example all the
bends in the model. The fields in the List Processor tables are active, allowing user modification of the
data. This processor also enables groups of elements to be "blocked," with further manipulation of the
data in the block. Blocks can be rotated, duplicated, renumbered, or deleted as necessary.
Over 60 restraint types provide the most comprehensive library of boundary conditions available to the
pipe stress analyst today. Support types include all of the expected linear and non-linear directional
restraints, as well as: bottomed out spring hangers, large rotation rods, and bi-linear soil restraints.
The Buried Pipe Modeler allows rapid creation of complex soil models. By simply specifying the soil
characteristics, and which portions of a system are buried, CAESAR II can re-mesh the model, computing
the soil restraint locations, directions, and stiffness’s as necessary.
Through the use of 32 bit compilers, the upper limit on model size is restricted solely by the amount of
free upper RAM. The limits on model size are reported in the input processor, to inform the user during
model construction.
Integrated Error Checking
The CAESAR II program includes an integrated error checker, which is automatically run following the
completion of the input specification. This error checker analyzes the user-specified input and checks it
for consistency from both a "finite element" and "piping" point of view. Two types of messages are
generated by this error checker, warnings and fatal errors. Warning messages are conditions which may
be errors, but are numerically acceptable. For example, warning messages are generated when a change
in direction is encountered, without a bend or tee being specified. Fatal error messages are generated
when the specified input data is inconsistent or illogical, for example if the corrosion allowance is larger
than the corresponding wall thickness.
Jobs can be analyzed with warning messages, but not with fatal error messages.
Interactive Report Review
Once a job has been analyzed, the solution results are available for review at any time. The review
module is interactive, allowing the selective review of individual output reports for individual load cases.
Reports can be generated in any units system simply by altering the configuration. Reports can be
viewed on the terminal screen, or sent to a printer or to a disk file.
Design Process
The flowline is from oil well head to 8” gathering flowline which is routed several kilometers length and
it is reached to gathering stations. Figure 3.4 shows the piping plan for well head pipe line and gathering
flowline. For this project the existing flowline is considered from one battery limit to other battery limit
which is included two expansion loop, two well head piping and around 250 meter of straight length
portion. Stress analysis has been done and the rectification carried out base on the stress analysis report
and recommendations.
2.2 Pipe failure Analysis
According to the study conducted by Tubular Engineering, China National Petroleum Corporation, the
failed mechanically lined pipe is composed of L415 carbon steel and 316L stainless steel with the outer
diameter of 508 mm and wall thickness of outer carbon steel and stainless steel liner is 14.2 and 2.5 mm,
respectively. The welding methods are Gas Tungsten Arc Weld (GTAW) and Shielded Metal Arc Welding
and the X-ray inspection of weld joint judged as Class-I without defect. Prior to operation, the flowline
was conducted strength pressure test and sealing pressure test at 22 MPa and 16 MPa, respectively.
The fluid flowing in flowline is natural gas, the designed pressure is 16 MPa, and the operation pressure
is between 10.5 and 12.5 MPa. The mechanically lined pipe failure occurred after 75 days operation with
operating parameters. The girth weld cracking was observed between straight and bend pipe section and
the crack length is 660 mm and the max width is 30mm. The fracture surface of outer CS is different from
316 liner. Crack source zone and propagation zone can be seen in the outer carbon steel layer and several
pits also. The crack source zone the area closes to the liner by quasi- cleavage fracture and the incomplete
fusion also found. In addition, the small amount of corrosion product found in the crack propagation zone.
The reason behind the crack , the failed pipe area had undergone the heavy rain for two days before the
failure occurred , which caused the ground settlement as result of part pipe section in strained condition.
The straight pipe section is fixed by the retaining wall, while the bend pipe section is pulled by soil
movement. So that the stress concentration occurred in the weld joint due to pulling force.
The external stress would cause the relative motion between outer L414 carbon steel and 316 liners.
However the outer CS and liner was fixed by sealing weld and the relative motion is impeded by the sealing
weld , consequently the sealing pass zone ,as the boundary of outer L415 CS and 316L liner , is a high shear
concentration area. The sealing pass zone is characterized by martensitic structure with high hardness,
which is a typical hard and brittle structure and very susceptible to cracking, which is typical hard and
brittle structure with hardness of HV 350 – 450.
To avoid this type of cracks, it is necessary to optimize the welding procedure, such as the weld joint
structure design, welding rod material selection and heat treatment temperature control.
2.3 Piping Stress Analysis
The following sources are generating the stress in the piping system, Weight, internal / external pressure,
temperature change, occasional loads due to wind and force due to vibration. If a pipe designed for a
particular pressure, increasing the pressure limit the pipe would rupture or failure, when the loads are
always under the limits considered safe. The loads in the piping system broadly classified as primary loads
and secondary loads.
Primary Loads are developed by the imposed loading and are necessary to satisfy the equilibrium
between external and internal forces and moments of the piping system. Primary stresses are not selflimiting. These can be divided into two categories based on the duration of loading.
Sustained loads are expected to be present throughout the plant operation. e,g. pressure and weight.
Occasional loads are present at infrequent intervals during plant operation. e,g. earthquake, winds, etc.
Secondary Loads are developed by the constraint of displacements of a structure. These displacements
can be caused either by thermal expansion or by outwardly imposed restraint and anchor point
movements. Secondary stresses are self-limiting.
Expansion loads are loads due to displacements of piping. e,g .thermal expansion, seismic anchor
movements, and building settlement.
Pipe used for transporting fluid would be under internal pressure load and jacketed pipe or tubes in a
shell & exchanger etc., may be under the external pressure. Both are induces stress in an axial as well as
circumferential directions.
ASME B 31.3 code governs all piping within the property limits of facilities engaged in the processing or
handling of chemical, petroleum or related products. Examples are a chemical plant, petroleum refinery,
loading terminal, natural gas processing plant, bulk plant, compounding plant and tank farm.
The loadings required to be considered are pressure, weight (live and dead loads), impact, wind, earth
quake-induced horizontal forces, vibration discharge reactions, thermal expansion and contraction,
temperature gradients, anchor movements.
Permit and other
arrangements
Design Process
Site Visit
Site survey /
Data collection
Inspection
Identify the
Problems
Failure Analysis/
Stress Analysis
(CAESER II)
Isometric drawing
preparation
Data Input
Stress report
Preparation
Discussion
Conclusion
Recommendation
Project Flow Chart
CAESAR II Calculation
Pipe stress analysis has been carried out using CAESAR II computer application software. Pipe stress
analysis to check the stresses, displacements, forces & moments are within allowable for 8” piping. This
calculation is initiated because the existing crude oil production pipeline moving from the support due
to excess stress. And it is identified that the Guide supports are not located based on the stress report.
So that the guide support given alternate foundations.
Pipe size DN 80 to DN 200 (NPS 3 to NPS 8) with design temperature above 230 °C (450 °F)
Stress system No.
: SYS-001
Code
: B 31.3 -2012
Medium
: Oil
Material
: A 106 Gr.B
Design / Pipe Class pressure
: 1380 kpag (200 psi)
Design / Pipe Class temperature
: 190°C / 5°C (374 °F)
Calculation Method
Stress Analysis – As per B 31.3 2012
Software Used
Title
Version
Validation (Y / N / N/A)
CAESAR II
7.00
Y
The stresses in Hydro, sustain and expansion conditions for piping in this systems found within
the allowable limits as per ASME B31.3 and Stress summary results are included in Appendix A.
The Stress Analysis performed using CAESAR II for system under consideration based on 5.2,
Basis of Design for Stress Analysis and the results reported accordingly under Stress Summary
Report.
Computer flexibility analysis carried out using CAESAR II software for all critical lines (as per the
requirement of Basis of Design for Stress Analysis) for compliance of stress requirement in
accordance with ASME B 31.3. Analysis recommends logical supports, provides support load
summary, thermal displacements and nozzle loadings for connected equipment. The table 3.3
shows the design conditions.
Design conditions
Maximum Design Temperature – T1
190 ° C
Minimum Design Temperature – T2
5° C (41 °F)
Design Pressure – P1
1380 kpag
Hydro test Pressure – PH
7650 kpag (1110 psi)
8” –Sch 40
Pipe wall thickness
Table 3.2: Design conditions
Input data
Installation Temperature considered
Rigid weights of all flanges, valves
weights are considered
21°C (70 °F)
From CAESAR Data base /Pipe Data
Friction co-efficient considered
CAESAR II version 7.0 is based
Insulation
0.4
Piping code ASME B 31.3 -2012 version
40 mm thick
Mineral Wool material with density
Fluid density considered
0.00014 kg/cu.m
1000 kg / mtr3 as an conservative approach
Table 3.3: Input Data for CAESAR analysis.
ASME B31.3, contains requirements for piping typically found in petroleum refineries; chemical,
pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related
processing plants and terminals. ... B31.3 is one of ASME's most requested codes.
Meaning of (ASME), The American Society of Mechanical Engineers (ASME) is an American
professional association that, in its own words, "promotes the art, science, and practice of
multidisciplinary engineering and allied sciences around the globe" via "continuing
education, training and professional development, codes and standards.
Assumptions
Wind loads not considered as the pipe elevation is below 10mtr.
Natural frequency is considered
This chapter will discuss the finding and results of the Piping stress analysis. The study project has
carried out the stress analysis of existing piping system of crude production pipeline, which is move from
the existing support due to over stress. The stress analysis has carried out with CEASER II software.
Detail analysis of the results presented.
Allowable Stress for Thermal Expansion
The allowable stress for thermal expansion and other deformation-induced
stresses is substantially higher than for sustained loads. This is due to the
difference between load-controlled conditions, such as weight and pressure, and
deformation-controlled conditions, such as thermal expansion or end
displacements (e.g., due to thermal expansion of attached equipment).
When a load-controlled stress is calculated, it is an actual stress value. It is
governed by equilibrium. For example, the stress in a bar when a tensile force is
applied to it is the force divided by the area of the bar. This is not the case for
thermal stresses. In the case of thermal stresses, it is the value of strain that is
known. The elastically calculated stress is simply the strain value times the
elastic modulus. This makes essentially no difference until the stress exceeds the
yield strength of the material. In that case, the location on the stress-strain curve
for the material is determined based on the calculated stress for load-controlled,
or sustained, loads. The location on the stress-strain curve for the material is
determined based on the calculated strain (or elastically calculated stress divided
by elastic modulus) for deformation-controlled (e.g., thermal expansion) loads.
This is illustrated in Fig. 7.1. Because the stress analyses are based on the
assumption of elastic behavior, it is necessary to discriminate between
deformation-controlled and load-controlled conditions in order to properly
understand the post-yield behavior.
It is considered desirable for the piping system to behave in a substantially
elastic manner so that the elastic stress analysis is valid. Furthermore, having
plastic deformation every cycle carries with it uncertainties with respect to strain
concentration and can be potentially far more damaging than calculated to be in
the elastic analysis. One way to accomplish this would be to limit the total stress
range to yield stress. However, this would be overly conservative and result in
un-necessary expansion loops and joints. Instead, the concept of shakedown to
elastic behavior is used in the Code. The basis for the Code equations is
described by Markl (1960d). Rossheim and MarkI (1960) also provide an
interesting discussion on some of the thinking behind the rules.
The allowable thermal expansion stress in the Code is designed to result in
shakedown to elastic behavior after a few operating cycles. The equation
provided in the Code is (ASME B31.3, Eq. (1a)).
Manual Calculation Result
A) Allowable stress ( Expansion )
As shown in equation 3.1
SA = 𝑓 (1.25 𝑆𝑐 + 0.25𝑆ℎ )
Where:
𝑓
= stress range factor
𝑆𝑐
= allowable stress of pipe on minimum working temperature.
𝑆ℎ
= allowable stress of pipe on maximum working temperature
Stress range factor = 1
𝑆𝑐 = 20 ksi
𝑆ℎ = 20 ksi
Values of (𝑓, 𝑆𝑐 , 𝑆ℎ ) based from Table (Table A-1,ASME B31.3)
SA = 1 (1.25 X 20 + 0.25 X 20)
= 30 Ksi
Convert Ksi to KPa = 30 X 6.895 KPa
= 206.85 X 1000 Pa
SA = 206850 Pa
B) Allowable stress ( Hydrotest load )
Allowable Stress (Yield strength) = 35 Ksi (Table A-1, ASME B31.3)
Convert to Ksi to Kpa = 35 X 6.895 Kpa
= 241.325 X 1000 Pa
SA = 241325 Pa
C) Allowable stress ( Sustain load )
Allowable Stress (sustain from Hot case) = 20ksi (Table A-1, ASME B31.3)
Convert to Ksi to Kpa = 20 X 6.895 Kpa
= 137.9 X 1000 Ka
SA = 137000 pa
4.2. Result and Analysis of CAESAR II.
4.2.1
Stress Summary
The Table 3.4 shows the all Stress summary details of the report
Sustained Load:
Sustain load is the load induced by the installation of piping system always. This
load is mixture of the load caused by internal pressure and weight load.
Displacement Stress:
The displacement stress range SE is the calculated range of secondary stress a
piping system will generate when subjected to thermal expansion or contraction.
Operational Load Case:
Once the operations started, the working fluid will flow through the piping at an
operating temperature and pressure. That will be taking in this load case
consideration.
Occasional Load Stresses:
Occasional load stresses in piping systems are the some of those stresses initiated
by loads such as relief valve discharge, wind and earthquake.
Hydro testing Load Stress:
In this case, the pipe will be full of water for hydro testing, so that the load subjected to
water weight and hydro test pressure.
Conclusion
This study project to Learning from pipeline failures can help us to reduce our pipeline failures, both in
terms of numbers and consequences. Root cause failure of the pipe section is due to the stress developed
in the pipeline section, manufacturing defects and thermal expansion due to the operation condition
changes like sudden rising of pressure and temperature and water hammer. Proper methodology is the
key to the design optimization.
The aim of the project to avoid the failure of the pipelines due to various issues and it is necessary to
optimize the providing proper supports, proper expansion loops, Proper fabrication, and installation
procedure. The objective of this project is to avoid the pipeline damages due to movement of line from
the support. The pipeline moved from the original position due to high pressure, high temperature and
water hammer.
Recommendation
•
CEASER II software analysis has carried out and rectified the pipeline arrangements with a
necessary guide support and line stopper support.
•
Fixed sleeper foundation support (Line stop) should be provide on the straight pipeline portion to
arrest the movement due to sudden raising of pressure and water hammer.
•
Accumulated sands due to sand storm and regular wind in desert area shall be remove from the
sleeper location periodically.
References:
Purchase answer to see full
attachment