Example PipeLay Models

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Example PipeLay Models

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The following articles describe a number of examples that demonstrate many of the modelling and analytical capabilities of PipeLay. This introductory article contains the following sections:

Overview’ gives a brief overview of the examples articles.

How to Use these Articles’ gives guidelines on running the examples described in the articles and where the PipeLay project files for the examples can be located.

Description of Examples’ briefly describes the PipeLay examples included here.

 

Overview

The examples in these articles cover a wide range of program applications, including:

Normal Lay (S-Lay, J-Lay and Reel-Lay configurations)

Abandonment & Recovery

Start-up scenarios (via Stab & Hinge, via Sheave, Dead Man Anchor, Davit Lift, SCR Initiation)

Structure installation

As-laid span analysis

SCR Transfer

Articulated S-Lay

Pipe-in-pipe configurations

The examples in these articles are intended to provide a representative sample of the capabilities of the program. There are, however, many program features that are not described in the examples and the range of application of the program is by no means limited to the models described here. Also note that if you are using the Starter Edition of PipeLay then certain advanced program features are disabled and therefore some of the examples are simplified accordingly. Where this occurs a suitable note is provided in the relevant example article outlining the extent of the simplification and its impact on how you should interpret the article.

 

How to Use these articles

A total of sixteen example PipeLay projects and one step-by-step guide, in the form of a worked example, are described in the following articles. Each one presents a description of the key project components used in the example. All relevant input data (structure properties, environmental data etc.) is presented in tabular format for ease of reference. The analysis is described in detail, and a brief discussion of some of the more pertinent results of the various analyses follows, together with some sample plots.

All of the PipeLay project files and additional analysis input files required to run the examples are located in the Examples subdirectory of your PipeLay installation directory. A list of the files associated with each example is given in the respective example articles.

If you have not had much experience using PipeLay or feel the need to re-familiarise yourself with some of the steps required to use the software effectively, it is advised that you complete the steps described in the Worked Example. This step-by-step guide which will allow you to become familiar with the process of creating a model and running an analysis in PipeLay. Subsequently, it is recommended that, for the remaining examples that are of interest, you should first read the relevant article and sub articles to familiarise yourself with the installation scenario under consideration. It is worth taking the time to examine the various components that go to making up the model, the environmental and loading conditions and the analysis component itself. The components used in the project are hyper-linked to the relevant articles to further explain the significance of the various inputs. You can of course change the input data in the components to examine the effect of, for example, changing structure properties, or you may wish to specify customised postprocessing to examine certain results in more detail. The flexible nature of the PipeLay project database allows you to save altered or new components using different names so that there is no need to overwrite the original example components or start a new project.

 

Description of Examples

Worked Example

The Worked Example gives a step-by-step guide to the abandonment scenario modelled in Example 3 and is meant as an introduction to PipeLay. The example is described in detail, from model creation to the examination of analysis output. It is not intended to be a comprehensive reference for all data inputs, or indeed, for all the capabilities of PipeLay – instead it is intended to guide you through all the steps involved in setting up and performing a typical analysis. The 'Software Components & Operation' article and sub-articles provide a detailed description of all aspects of the program. If you are an experienced PipeLay user, you will already be familiar with the majority of the concepts explained here. However you may still find it useful to read through the Worked Example article, as it provides a sound overview of the program operation in general.

Example 1

Example 1 simulates a normal S-Lay installation scenario. The S-Lay model includes a lay vessel equipped with an S-Lay stinger fitted with V-shaped roller boxes. A pipeline runs along a set of vessel supports before passing over the stinger and down onto the seabed. The pipeline is restrained on the vessel deck by a tensioner. A static analysis and two dynamic analyses, one with a regular wave loading and the other a random sea loading, are included in the example. A top tension of 5000 kN is specified as the installation criteria for the static configuration.

Example 2

Example 2 simulates a normal J-lay installation scenario. The J-Lay model includes a lay vessel with a J-Lay tower. The pipeline runs from a tensioner at the top of the tower, through the tower supports and down onto the seabed.  Zero-gap supports are used above the hangoff table, while O-shaped rollerboxes of increasing diameter are specified below it. Static, dynamic and fatigue analyses are performed on the configuration. In the static analysis, a desirable static configuration is obtained based on an optimum value of the pipeline departure angle. Two dynamic restart analyses are included to subject the J-Lay configuration to regular wave and random sea loadings. The fatigue analysis is carried out as a postprocessing operation after the random sea analysis has completed.

Example 3

Example 3 simulates an abandonment scenario. It considers the lowering of a pipeline to the seabed from a lay vessel via a winch cable. The lay vessel is equipped with an S-Lay stinger fitted with V-shaped roller boxes. The pipe is restrained by a tensioner on the vessel deck. The analysis procedure is performed as a series of 15 static installation stages where the winch cable is paid-out in finite increments while the vessel simultaneously surges forward. A maximum bending strain of 0.242 % in the sagbend region and a tip separation between 0.8 and 0.9 m are used as the installation criteria for all 15 stages. This example is the reverse procedure to the recovery scenario modelled in Example 4.

Example 4

Example 4 simulates a recovery scenario. It considers a pipeline being raised from the seabed to a lay vessel via a winch cable. The lay vessel is equipped with an S-Lay stinger fitted with U-shaped roller boxes. The cable is restrained by a tensioner on the vessel deck. The analysis procedure is performed as a series of 15 static installation stages where the winch cable is shortened in finite increments while the vessel simultaneously surges backwards. A maximum bending strain of 0.242 % in the sagbend region and a tip separation between 0.8 and 0.9 m are used as the installation criteria for all 15 stages. This example is the reverse procedure to the abandonment scenario modelled in Example 3.

Example 5

Example 5 simulates a structure installation. It considers the transition of an in-line structure along a pipeline, from the lay vessel to the seabed. The lay vessel is equipped with an S-Lay stinger fitted with V-shaped roller boxes. The pipeline is restrained by a tensioner on the vessel deck. A buoy is attached to the structure by means of a cable. The analysis procedure is performed as a series of 7 static analyses where the structure descends along the pipeline to the seabed. A desirable static configuration for each stage is obtained based on an optimum value for the tip separation.

Example 6

Example 6 simulates a start-up via stab and hinge scenario. It considers the paying out of a pipe over a stinger until the end of the pipe makes contact with the seabed. Once contact has been initiated, the end of the pipe is pinned at the seabed and the vessel is offset in the surge direction as more pipe is paid out.  The lay vessel is equipped with an S-Lay stinger fitted with V-shaped roller boxes. The pipe is restrained by a tensioner on the vessel deck. Support locations on the stinger are defined explicitly using coordinates. The analysis procedure is performed as a series of nine static installation stages. The first four stages represent the pipe hanging freely from the vessel as it is lowered to the seabed. In the remaining five stages the pipe is pinned to the seabed and the vessel is incrementally offset as more pipe is paid out. Von Mises stress in the sagbend region is used as the installation criteria for the last five stages.

Example 7

Example 7 simulates a start-up via sheave scenario. It considers a pipeline initiation to the shore via a winch cable, which runs from the lay vessel down to a sheave on the shore before returning back up to the vessel. The winch cable is modelled as two separate cables, one running from the vessel to the sheave (main cable) and the other running from the sheave back up to the vessel (return cable). The lay vessel is equipped with a rigid S-Lay stinger fitted with V-shaped roller boxes, which follow user-defined radii of curvature. The pipe is restrained at the vessel by a tensioner. The analysis procedure is performed as a series of eleven static installation stages in which the pipe is paid-out incrementally (and the length of the main cable is reduced correspondingly). An optimum length for the return cable at each stage is automatically obtained based on the sheave efficiency ratio.

Example 8

Example 8 simulates an as-laid span scenario. It considers a pipeline lying on a seabed with an arbitrary topography. The pipeline is flooded with seawater. Both ends of the pipeline are pinned to the seabed, with one end adjusted to satisfy various tension criteria at the seabed connection point over the course of three installation stages. Multiple static analyses are performed in order to examine the stresses in the as-laid configuration lying on the arbitrary seabed for each tension criteria.

Example 9

Example 9 simulates a SCR transfer via winched cable. The system consists of a SCR hanging from an installation vessel via a winch cable. A second winch cable joins the top of the SCR to a second vessel (TLP). The transfer process involves increasing the length of the cable joining the SCR to the installation vessel while simultaneously shortening the cable running from the SCR to the TLP.  The entire transfer procedure is performed as a series of seven static installation stages.

Example 10

Example 10 simulates an articulated S-Lay installation scenario. The model includes a lay vessel equipped with an articulated S-Lay stinger. The stinger is comprised of two stinger sections with three V-shaped roller boxes on each section. Hinges are placed at the start of each section in order to allow the sections to move independently of one another. The pipeline runs along a set of vessel supports before passing over the stinger sections and down onto the seabed. The pipeline is restrained on the vessel deck by a tensioner. Both static and dynamic analyses are included in the example. Regular wave loading is applied during the dynamic analysis.

Example 11

Example 11 simulates a Davit Lift scenario. It considers the lifting of a pipeline from the seabed to a vessel using multiple winch cables. The initial model consists of a pipeline lying flat on the seabed. The pipeline is connected to the vessel by three winch cables, which are vertical initially. The analysis procedure is performed as a series of 6 static installation stages in which the lengths of the winch cables are adjusted in order to raise the pipeline to the vessel.

Example 12

Example 12 simulates a DMA start-up scenario. It considers a pipeline initiation to the seabed via a cable, which runs from the lay vessel down to an anchor on the seabed. The lay vessel is equipped with an S-Lay stinger fitted with V-shaped roller boxes. The pipe is restrained on the vessel deck by a tensioner. The analysis procedure is performed as a series of 13 static installation stages in which the pipe is paid-out incrementally as the vessel surges forward. A cable tension of between 300 kN and 301 kN is maintained at the anchor throughout the start-up procedure.

Example 13

Example 13 simulates the installation of a pipe-in-pipe line. The S-Lay model includes a lay vessel equipped with an S-Lay stinger fitted with V-shaped roller boxes. A pipeline runs along a set of vessel supports before passing over the stinger and down onto the seabed. The pipeline is restrained on the vessel deck by a tensioner. Both the outer and inner pipes are modelled explicitly – the analytical model simulates interaction in terms of centralisers, bulkheads and gaps. A static analysis and a regular wave dynamic analysis are included in the example.

Example 14

Example 14 simulates an SCR initiation scenario. The initial model consists of a pipeline hanging between an installation vessel and a floating production unit (FPU). Two static analyses are performed – the first to determine the initial static configuration and the second to perform the SCR initiation. Initiation is performed by deploying pipe from the FPU, offsetting the installation vessel and reducing the wire length.

Example 15

Example 15 simulates a shallow water S-Lay scenario. The shallow water model includes an S-Lay vessel equipped with a rigid stinger fitted with V-shaped roller boxes. A concrete coated pipeline runs along a set of vessel supports before passing over the stinger and down onto the seabed. The pipeline is restrained on the vessel deck by a tensioner. A static analysis and two dynamic analyses, one with a regular wave loading and the other a random sea loading, are included in the example. A top tension of 3200 kN is specified as the installation criteria for the static configuration. A pipe bend radius for the stinger region of 250m is also targeted. Fatigue analysis and DNV local buckling checks are performed on the dynamic outputs from the example.

Example 16

Example 16 simulates a reel-lay scenario whereby a model including a lay vessel equipped with a reel-lay ramp simulates reel-lay using the active line length feature in PipeLay. A pipeline coated in corrosion protection runs from a Zero-gap support, through O-shaped roller boxes and down onto the seabed. Static and dynamic analyses are performed on the configuration to demonstrate how the active line length functionality, simulating reel-lay pay-out, can be used in both types of analyses. An initial static analysis and two subsequent restart analyses, one static and one dynamic, are included in the example. In the initial static analysis, a desirable static configuration is obtained based on an optimum value for the tip separation. The two subsequent analyses restart from this optimised configuration and carry out the reel-lay pay-out analysis. DNV local buckling checks are performed on the outputs from the example.