1. STUDY REPORT ON
OFFSHORE PIPELINE ENGINEERING
BY
KAARTHIK SARAVANAN
Department of Mechanical Engineering
Velammal Engineering College, Chennai.
Study work done at McDermott, Middle East Inc. Dubai
as a part of Summer Internship from
19th
June – 28th
July 2016.

2. PREFACE:
The primary objective behind this report was to gain knowledge about
Pipeline Engineering in Offshore Industry. The report deals with
the basics of the ideas and techniques used in this field to help clarify
the approach towards it. I have tried to keep the report error free and
presented it to the best of my ability. Any suggestions for further
improvement of this work will be acknowledged.
All the images used in this report are taken from the net source
for easy understanding and reference.

3. ACKNOWLEDGEMENT:
I have great pleasure in presenting this report which has been done as a part of
Summer Internship at McDermott Inc. which finds it name among the world’s
top most oil field service companies.
The experience which I got in McDermott Industry was extremely valuable to
my career development. I am highly indebted to Mr. ManojKulshrestha,
Manager, Subsea Dept. for his constant supervision and advice throughout my
intern period. I’m very thankful to Mr. Harshad Phadnis, Pipeline Engineer
for taking time out to hear and guide me giving assignments during this project.
I express my gratitude sense to the whole McDermott Subsea Dept. staffs if I
didn’t mention here by their names who helped me to gather information in
various ways towards the project.
I would like to thank my parents too for their immense supportwithout which I
would not be able to compile this report.
Thank you all.

4. COMPANY PROFILE:
 McDermottInternational is a leading American EPCI(Engineering,
Procurement, Construction and Installation) company focused on
offshore oil and gas projects.
 It has its operating locations and fabrication yards in about 20 countries in
the Middle East, Atlantic and Asia Pacific regions.
 It has fabricated and installed various structures, laid pipelines and
exported facilities to Europe and Africa.
 It is a premier leader of the global offshore engineering and construction
industry through innovations and marine services while achieving the
highest industry performance in terms of safety, quality and ethics.

5. PIPELINE ENGINEERING:
INTRODUCTION:
The function of Pipeline Engineering is to apply the knowledge of
Engineering drawings will be implemented and using the data from it materials
will be purchased, fabricated and assembled into piping systems thus fulfilling
the process requirements.
Fluid flow Stress analysis
Material
properties
Engineering
specifications
Process

6. PIPELINE TRANSPORTATION:
 Pipelines are means of transportation of materials over long distances.
 Any chemically stable fluid substancecan be sent. (Eg: fuels)
PURPOSE OF OFFSHORE PIPELINES:
1.Export of offshore resources.
2.Flowlines totransferproducts fromplatforms toexportlines.
3.Water or chemical injectionflowlines
4.Pipeline bundles connecting subseamanifolds andwells.

7. Advantages of pipelines compared to other modes of
transportation (rail, truck, barges):
 Large volume transportation (high energy density)
 Can be laid through difficult conditions under water
 Low energy consumption and requires little maintenance
 Safe and environment friendly
 High reliability
 Negligible loss of productin transit.
Thus pipelines are the most convenient, economical and efficient
way of transporting oil, natural gas and refined products.
Working sectors of offshore industry:
Upstream: Exploration and Geological Surveys
Midstream:Transportation of resources
Downstream:Refining of resources

8.  Upstream: Searching for potential underwater crude oil and natural gas
fields by survey, seismic and drilling activities. Thus subsequently
operating the wells that can be recovered.
 Midstream: Setting up of offshore structures and pipelines to transport
the products obtained from the sites to the refineries followed by
downstream distributors.
 Downstream: Refining of the crude products and then processing it
followed by distribution. Thus marketing the derived products of crude
oil and gas.

9. OFFSHORE STRUCTURES:
 Offshore deals with the energy location and processes carried out at a
distance awayfrom shore.
 Basically it is about drilling of oil and gas reservoirs.
The various offshore structures are:
JacketsPlatforms
Riser
Tie-in
spool
UmbilicalValve skid

10. 1. Platforms:
 Large structures either built on seabedor left floating with anchors or
wires depending on circumstances.
 Also known as rigs.
 Has facilities to drill well, provides all equipments for the oil and gas
processes and has oil storagesbeforeit is brought to onshore for refining
followed by transportations.
 Services for a very long period of years.
 Some major platform types depending on the operating depth are Fixed,
FPSO (Floating production, Storage and offloading system), Tension
leg, Jackup-rig, Semisubmersible and SPAR.

11. 2. Jackets:
 Steel tubular structures supporting the platform deck.
 Rests on the seabed through piling.
 As a cage it protects the piping.

12. 3. Riser:
 Pipelines developed for vertical transportation of materials from the
seabed(subsea oilwells)to production and drilling facilities above the
watersurface.
 Serves as a conduit (channel) betweenseafloorand facilities.
 Productionmaterials such as hydrocarbons, injection and controlfluids,
gas lifts are sent through it.
 Riser section closestto the seafloor is joined with a pipeline clamped to the
side of the facility and the next sections rise up the facility side to the top.
 While rising, various clamps (Hanger type is the major clamp) are
provided for withstanding weights, giving supports and arrest the
lateral movements.

13. 4. Tie-in spool:
 Elements connecting the offshore pipelines to the Riser followed by other
facilities.
 Provides final connection after pipeline installation (Ties the pipeline to
the structure).
 Its design and shape depends on the distance to fit between the riser bend
and pipeline laydown point.
 Made flexible to allow the pipelines to expand during operational stages
because of temperature changes and thus the risers won’t be disturbed.
 Reduces forces inthe connectors to ensure safe transportation and avoid
leakages.

14. 5. Valve skids:
 Subsea valves are used to governthe material flow through undersea
pipelines or other apparatus. They are designed to work in the marine
environment withstanding the pressure effects, corrosionand debris.
 The working of these valves is isolated and controlled by fluid modules
called valve skids.
 The actuationand recoveryresponse time of the valves is taken care by
the valve skids.

15. 6. Umbilical:
 Bundle ofcables andtubes put togethersurroundedby anoutersheath
that transfers power (hydraulic, electronic), fibre optic and electrical
signals, chemical and gas supply within a field (long distances) or from
topside to subsea.
 Provides a way to communicate with different subsea equipments on
the seabedand thus having control of it.
 Umbilical design varies with the projectrequirements.
 Subsea intervention umbilicals are also used for offshore drilling
activities.

16. OFFSHORE FLOWLINE LAYOUT:

17. PIPELINE DESIGN STAGES:
Requirement to transport product
Operator specific requirements
Codes,Standards and Specifications
Route selection
Geophysical and geotechnical surveys
Material grade selection
Wall thickness
Flowline protection( corrosion coatings )
Flowline installation
Flowline stress analysis
Optimum flowline Inner dia and wall thickness

18. DESIGN REQUIREMENTS:
 Wall thickness
 Material grade selection:
 Cathodic protection
 Suitability to product
 Route selection:
 Minimize flowline length
 Minimize flowline spands
 Minimize number of bends
 Maximum corridor width
 Flowline protection:
 Concrete coating
 Trenching / Burying
 Rockdumping
 Mattresses / Structures
 Flowline stress analysis:
 Hoop and longitudinal stress
 Span analysis and vortex shedding
 Stability and expansion analysis
 Buckling and crossing analysis

19.  Flowline installation analysis:
 Lay analysis
 Welding
 Propagation buckling
 Hydrostatic collapse
 Optimal design
Pipeline route selection:
The route should be selected based on the following parameters:
 Seabed topography
 Obstructions, debris and existing structures
 Marine activities
 Pipeline route radius
 Install ability
 Existing pipeline
 Select direct shortest route.

20. Surveys:
Surveys are conducted on the selected routes to be aware of the conditions
existing there and the soil characteristics so that the structures are safely
designed and built. It is necessary to investigate and evaluate the risks
thoroughly. The two types of surveys are:
1. Geophysical ( Seabed Bathymetry):
 Establishing topography
 Identification of significant seabedfeatures, obstructions and hazards
and determination of surface layer geometry (water depth) through
normal sample collectionand observation.
2. Geotechnical (Stratification):
 Geological characteristics ofdifferent soils and rocks found on site.
 Insitu and laboratory testings through boreholes to find the soil
parameters and affecting properties.

21. Pipeline material selection:
The pipeline material type can be rigid, flexible or composite. The material
selection process is based on the following:
 Identify corrosionthreats
 Define the corrosioncircuits
 Calculate the corrosionrate per year
 Calculate the Service Life Corrosion (SLC) based on design life
 Consider the materials options
 Carry out the Life Cycle Costing (LCC)
 Review the materials selection w.r.t design / operating / constructability
 Finally select the choice materials.
Types of pipe:
Low carbon
steel
Corrosion
resistant
Cladded
Coil tubing
Flexible hose
and pipe

22. The above pipelines are manufactured in different forms:
 Seamless( Manufactured without seams)
 SAW( Submerged arc welding)
 ERW( Electric resistance welded)
 HFIW( High frequency induction welding)
Pipeline Coatings:
The various types of coatings given to pipelines are:
 Corrosioncoatings
 Concrete weight coatings
 Insulation coatings
 Field joint coatings

23. Corrosion coatings:
Pipelines get corrodedas they are continuously exposedto sea atmosphere.
To prevent the corrosionand increase its service period, various corrosion
coatings are given. The commonly used corrosion coatings are
 Fusion bonded epoxy(FBE)
 3 layer polypropylene (3LPP)
 3 layer polyethylene (3LPE)
 Neoprene
Concrete weight coatings:
Pipelines will have impact due to the sea waves. To ensure the stability of
the pipe againstwave loads, concrete weight coatings are given to add
weight to the pipe thus making it stable in seabed.

24. Insulation coatings:
Insulation coatings are provided to keep the conveyed fluid warm. Pipeline
should be heated either by active or passive methods.
Active heating includes electric heating and circulating hot water.
Passive method consists of insulation coating, Burial and Additional cover.
Field joint coatings:
As offshore pipelines are welded together either in single or double joint
segments on the offshore vessel, there is a need for coating at the weld
locations for corrosioncontrol. These coatings are called field joint coatings.
The liquid applied materials used are:
 Epoxies
 Urethanes
 Heat shrinkable sleeves
 Fusion bonded epoxy.

25. Pipeline wall thickness:
Pipeline wall thickness is an important criteria to considered and calculated in
the pipeline design. It decides the pressure conditions undergone by the pipe.
The factors influenced by wall thickness are:
 Internal and external pressure ( Hydrotesting and Burst operations)
 Local buckling and propagation( loads imposed on the pipe bends
causing it to collapse at extreme conditions)

26. Stress analysis diagram
Buckled pipeline segment

27. Pipeline thermal expansion:
 Pipelines develop expansion and contractiondue to temperature
changes and pressure effects
 As they are laid on seabed, the friction interaction between pipeline and
soil will resist expansion.
 So the pipelines have to be spaced properly in such a way that there is an
enough allowance forthem to expand during operationalstages.

28. Pipeline On bottom stability:
Pipelines are subjected to wave impact and pressure due to water depth. This
analysis has to be done to ensure the Lateral and Verticalstability.
1. Lateral Stability:
 Assessed bytaking the Metoceandata into consideration.
 The three main wave parameters are the height, time period and current
speed(Significant and maximum case).
 These data are recorded for a period of 1, 10, 50 and 100yrs from which
the wave directionality nature and force can be found.
2. Vertical stability:
 It is calculated to determine the expectedsettlementof the pipeline.
 It has to be ensured that the pipeline is not lifting up and unstable due
to buoyancy.
 The settlement calculations are based on the ultimate bearing capacity.

29. Pipeline Crossings:
 In case of existing pipelines or other offshore structures, the new
pipelines have to be setup in such a way that it satisfies the allowance
criteria thus not disturbing the existing structure.
 The supports which are used to setup are called crossings.
 Crossings can be in the form of sleepers, weightblocks, bridges or
mattresses (forcables).

31. Pipeline Free span analysis:
 Free span is the segmentof the pipe which can be left unsupported as
it can sustain the conditions on its own without supports.
 The analysis is performed to determine the maximum allowable free
span length and to assess whether the allowable free span length will be
exceededunder any load combinations.

32. Bottom roughness analysis:
 It is done to analyze the seabed profile ( tendency of being soft or
rough)
 The roughness of the locations along the pipeline route are found
considering the stress criteria.
 In general the analysis’s are performed on the following conditions:
 As laid ( Empty pipeline)
 Hydrotest ( Testing it by injecting water)
 Operating ( Actual working conditions )

33. Global Buckling design:
 As discussed earlier pipelines are subjected to buckling. A pipeline’s
capacity to withstand the lateral buckling without getting collapsed is
analyzed using Hobb’s analyticalmethod.
 It is a detailed FE (Finite element) analysis.
 The effective forces in a pipeline as a function of variations in design
pressure, operating temperature and seabedfriction shall be analyzed.
 After analysis mitigations will be implemented to controlbuckling.

34. Riser and Tie-in spool analysis:
 The grade of the line pipe, fabrication process, outside diameter,
nominal wall thickness, corrosionallowance, cladding, Specified
minimum yield strength (SMYS) and Specified minimum tensile
strength (SMTS)for the risers and spools are identified.
 Stress analysis of the riser and tie-in spoolis performed using
CAESAR (FEA software). Theanalysis gives the sufficient length
of the pipeline to avoid effects at the boundary or tie in locations.
 Under flexibility analysis riser clamps will also be designed based on
the forces acting on them at the jackets.Thus the clamps will be
located.
Cathodic protection design:
 It is a technique used to controlmetal corrosion bymaking it as the
cathode of electrolysis process.
 The cathodic metal is protected by a sacrificialanode metal which gets
corroded and protects the metal underneath it.
 Pipelines, risers and spools are protected by BraceletAnodes.
 Thus subseastructures are protected against external corrosionby the
combination of external corrosioncoatings andsacrificialbracelet
anode system.

36. Pipeline shore approach:
 Shore approachis where the pipeline crossesorreaches the coastal
line.
 Pipeline require additional protection at the shore.
 Open cut trenches will be given and pull heads will be installed.

37. Some of the other parameters taken into account are :
 Ambient sea water temperature conditions
 Properties such as density and kinematic viscosity
 Marine growth (accumulation of microorganisms, algae, plants or
animals on the subsea structures over years)
 Splash zone ( part between the dry zone and submerged zone which is
exposed to wave action )
 Hydrodynamic coefficients (drag, lift, inertia)
Design loads:
The various functional load cases are:
 Installation: Loads on the pipelines before installation or when the
pipeline is resting on the seabed without internal pressure and prior to
filling the pipelines for hydrotest. The pipeline is filled with air hence
density zero. They include :
 Gravity loads:Pipe weight, coating, buoyancy and attachments.
 Pressure loads : External pressure only
 Thermal loads: Zero thermal loads due to no temperature changes.
 Loads imposed on the pipelines due to transportation.

38.  Hydrotest : Testing the pipelines by water injection and subjected to
flow. The loads are:
 Gravity loads: Additionally water weight will be combined
 Pressure loads: Both external and internal out of which internal
correspondsto hydrostatic case.
 Thermal loads: Occurs due to watertemperature changes.
 Operational: Loads on the pipeline under normal operating
conditions includes all the above along with marine growth content and
settlement loads.
Piping fittings:
These are connectors usedto connectthe various components in a piping
system to regulate the fluid flow. The various fittings are:
 Flanges and gaskets
 Valves
 Bolts and nuts
 Elbows, reducers and pipe branch connectionsupports.
Thus it is the overview of an entire
pipeline design basis report .

39.  Flanges:
 Flanges are used to connectpipes, valves or pumps and other
equipments to form a piping system.
 It provides easyaccess forcleaning, inspectionor modification.
 Flanges are usually welded or screwed.
 Flanged joints are made by bolting two flanges togetherwith a gasket
in-between them to provide a seal. The commonly used flanges are:
 Weld neck flange
 Swivel flange
 Blind flange

40. Blind flange

41.  Gaskets:
 Gaskets are mechanical seals usually formed like a ring and used for
sealing of flange joints.
 In general, gaskets should not be reused.

42.  Valves:
 Valve is a device which regulates, directs or controls the flow of a
fluid by opening, closing or partially obstructing various passage
ways.
 The various valve types are:
 Gate valve
 Plug valve
 Ball valve
 Diaphragm valve
 Check valve
 Butterfly valve.

43.  Bolts and nuts:
 They are fasteners used to tighten and connect the piping components.
 Generally used are stud bolts with ceramic fluoropolymer coating and
corresponding hex nuts with tommy bore holes.
 Reducers:
 These are fittings used to connect the pipes of varying diameters.

44. Reducers
Codes and Standards:
The codes and standards from the following organizations as applicable to
pipeline engineering are incorporated for their reference. The most important
ones are:
 ASME ( American Societyof MechanicalEngineers )
 ASTM ( American Societyfor testing materials )
 ANSI ( American NationalStandardization Institute)
 API ( American Petroleum Institute )
 DNV ( Det Norske Veritas )
Thus the piping material selection and design basis will be done having the
codes and standards in mind for reference to follow. It should not be violatedor
optimized at any case.

45. What I learnt in McDermott?
I was exposed to the activities of the offshore industry. I got an idea about the
EPIC processes carried out by McDermott. I was made to work in a corporate
atmosphere where I had to take initiatives and get assignments from colleagues.
I learnt about how my Subsea Dept. is structured, functioning and the way in
which they are interconnected with the process,instrumentation, mechanical,
piping and structural departments.
I participated in two safety awareness walks in which I was taken to the
fabrication yards and was explained about how things work and especially the
safety measures taken to avoid risks and run job in a smoothway.
I also had a chance to visit Derrick Barge-27 and know its functioning
procedures.
I hereby thank McDermott for giving me this opportunity to work as an intern
and gain the work experience.
THANK YOU