Api spec 17j 2014 (american petroleum institute)

17J e4 Covers fm P ro vi de d by w w w s pi c ir L ic en se e N IS O C L ib ra ry Specification for Unbonded Flexible Pipe API SPECIFICATION 17J FOURTH EDITION, MAY 2014 EFFECTIVE DATE NOVEMBER 2014 C[.]

Terms and Definitions

For the purposes of this document, the following terms and definitions apply.

Components attached to flexible pipes serve several essential functions, including controlling the pipe's behavior, providing structural transitions to adjacent structures, and preventing excessive curvature They also facilitate the attachment of other structures, connect flanges or proprietary connectors, and offer protection or repair for the flexible pipe Additionally, these components create a seal between the flexible pipe and the inner walls of I-tubes or J-tubes, effectively preventing the escape of corrosion-inhibiting seawater.

Space between two extruded polymer layers, for example, the internal pressure sheath and external sheath that is sealed in the end fitting

NOTE Permeated gas and liquid are generally free to move and mix in the annulus

A polymer, fabric, wire, fiber, or other reinforcement wound around the tensile armors, compressing the wires/strips against the pipe body to resist radial buckling of these wires/strips

6 Lloyd’s Register EMEA, 71 Fenchurch Street, London EC3M 4BS, United Kingdom, www.lr.org.

7 NACE International (formerly the National Association of Corrosion Engineers), 1440 South Creek Drive, Houston, Texas 77084-4906, www.nace.org.

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Nonmetallic layer, either extruded thermoplastic sheath or tape wrapping, normally used to minimize wear between structural layers

Part of a guide tube, formed in the shape of a bellmouth, and designed to prevent overbending of the flexible pipe

Any device used to restrict bending of the flexible pipe

NOTE Bend limiters include bend restrictors, bend stiffeners, and bellmouths

Radius of curvature of the flexible pipe measured from the pipe centerline

NOTE Storage and operating minimum bend radius (MBR) are defined in 5.3.1

Mechanical device that functions as a mechanical stop and limits the local radius of curvature of the flexible pipe to a minimum value

The ancillary conical component is designed to locally minimize bending stresses and curvature in pipes, ensuring they remain within acceptable limits This component is typically affixed to an end fitting or a support structure, facilitating the transition of the flexible pipe through the bend stiffener.

A structure or mechanism that allows a riser bend stiffener to be connected to a structure allowing the bending to be transferred from the riser bend stiffener to that structure

The bending resistance of a flexible pipe is determined by the product of its effective elastic modulus and moment of inertia Additionally, the bending stiffness can fluctuate based on factors such as tension, pressure, and temperature.

Flexible pipes feature integrated steel reinforcement bonded to a vulcanized elastomeric material, incorporating textile elements for enhanced structural support or to separate elastomeric layers.

The buckling of tensile armors can occur in both radial (birdcaging) and lateral directions due to axial compression, also known as true wall compression This phenomenon may be influenced by factors such as pipe bending, twisting, or torsion, and is further affected by the condition of the annulus, whether it is flooded or dry.

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Weak points in the outer sheath designed to burst when the gas pressure in the annulus exceeds a specified value

NOTE The weak point is induced by reducing the thickness of the sheath over a localized area

Interlocked metallic construction serves as the innermost layer in rough bore pipes, effectively preventing the collapse of the internal pressure sheath or pipe This design safeguards against various forces, including pipe decompression, external pressure, tensile armor pressure, and mechanical crushing loads.

NOTE The carcass may be used externally to protect the external surface of the pipe; this is referred to as “abrasion protection.”

3.1.16 choke and kill line jumpers

Flexible pipe jumper located between a marine drilling riser steel choke line and kill line and blowout preventer

Device used to provide a leak-tight structural connection between the end fitting and adjacent piping Connectors include bolted flanges, clamped hubs, and proprietary connectors

NOTE They may be designed for diver-assisted makeup or for diverless operation using either mechanical or hydraulic apparatus

Flexible flowline crossing another pipe already laid on the seabed

NOTE 1 The underlying pipe may be a steel pipe or another flexible pipe

NOTE 2 It is normally necessary to support the overlying pipe to prevent overbending or crushing of the new or existing pipes

During the installation and retrieval of pipes, compressive guidance-induced loads or localized compressive loads are applied by typical laying equipment, including tensioners, wheels, sheaves, chutes, gutters, and handling collars These loads also occur under operating conditions when the pipeline is bent under tension, particularly in areas such as J-tube bends, bellmouths, and mid-water arch gutters.

The difference between design external pressure and design pressure

NOTE Design pressure is defined in 4.4.2

Maximum external pressure applied to a pipe during installation, operation, or retrieval, after considering tidal and wave effects, which is the maximum pressure acting external to a sheath layer

NOTE It can be either the full external pressure or the maximum annulus pressure acting on a sheath, whichever is larger

A consistent approach to the design of a component or system

An evaluation report by an independent verification agent (IVA) confirms the suitability and appropriate limits of a specific manufacturer's design methodologies, manufacturing processes, and materials during an initial review.

NOTE This report may include occasional amendments or revisions to address extensions beyond previous limits or revisions of methodologies

Maximum tensile load applied to a pipe during installation, operation, or retrieval, after considering the associated internal fluid density and pressure

The difference between the local internal pressure and the external hydrostatic pressure at each cross section

Tested in air at conditions defined by the international standard atmosphere

Service in which flexible pipe is exposed to a large number of cyclically varying loads and deflections during permanent operation

A structural and mechanical device is designed to effectively terminate various layers of piping, ensuring the load is transferred between the flexible pipe and the connector while sealing all internal and external fluid containment layers.

An event due to infrequent loads (e.g pressures in excess of the design, accidental conditions)

An event that produces responses having a low probability of being exceeded in the lifetime of the riser [e.g an event with a return period (RP) of 100 years]

An event of short duration due to infrequent loads (e.g pressures and environments in excess of operating plan, accidental conditions)

An event such as plan of operation; normal; in-place pressure testing; connected operation; and integrity, maintenance, and repair

An event of limited duration, such as transport, installation, retrieval, and field test

An event involving conditions that exceed extreme design events where fluid containment is just maintained (i.e material strength utilization is permitted to reach unity)

Fishscaling refers to the tendency of a wire or strip to not lay flat against the underlying layer, which is often a result of improper preforming during the armor winding process This issue can manifest in various layers, including tensile armor, pressure armor, or carcass layers.

A flexible pipe, either partially or entirely resting on or buried beneath the seafloor, is utilized in static applications In this context, the term "flowline" refers generically to flexible flowlines.

The assembly of a pipe body and end fittings involves a composite of layered materials that create a pressure-containing conduit, designed to accommodate significant deflections in its structure.

NOTE 1 Normally, the pipe body is built up as a composite structure composed of metallic and polymer layers

NOTE 2 The term “pipe” is used in this document as a generic term for flexible pipe

A flexible riser serves as a crucial connection between a platform, buoy, or ship and a flowline or seafloor installation It can be configured in various ways, including being freely suspended in a catenary shape, partially restrained by buoys or chains, or fully enclosed within a tube, such as I- or J-tubes.

An independent party or group, chosen by the manufacturer, is tasked with reviewing and certifying the specified product concept, such as the pipe and end fitting design, as well as the flexible pipe This includes evaluating associated design, manufacturing methods, material qualifications, and prototype performance based on the technical literature, analyses, and results provided by the manufacturer to determine the product's range of applicability.

NOTE An agent may also be called upon to witness some measurements and tests related to material qualification, manufacturing process control, validation of design methodologies, and prototype tests

Additional layer added to the flexible pipe to increase the thermal insulation properties, usually located between the outer tensile armor layer and the outer sheath

Extruded polymer layer located between internal pressure and outer sheaths, which may be used:

⎯ as a barrier to external fluids in smooth bore pipes;

⎯ as a barrier from external fluids for insulation layers, avoiding water absorption and creep and thus avoiding reduction in the pipe thermal exchange coefficient (TEC); or,

⎯ in avoiding flooding of an inner annulus when an outer annulus is flooded due to an outer sheath breach

Polymer layer excluding any sacrificial layers that ensures internal-fluid integrity This layer may consist of a number of sublayers, excluding sacrificial layers

Short flexible pipes are utilized in both subsea and topside applications, accommodating static and dynamic needs Dynamic topside jumpers represent a category of flexible pipes that respond to vessel motion, such as in turret applications.

Acronyms, Abbreviations, and Symbols

CIV corrected inherent viscosity DSC differential scanning calorimeter FAT factory acceptance test

HV hardness on Vickers scale

IPU integrated pipe umbilical IVA independent verification agent

MBR minimum bending radius MPI magnetic particle inspection NDE nondestructive examination OBR operating bend radius

OHTC overall heat transfer coefficient OLT offshore leak test

PE polyethylene PSL product specification level PVC polyvinyl chloride PVDF polyvinylidene fluoride RAO response amplitude operator

SIT structural integrity test S-N curves showing stress range vs number of cycles

SR storage minimum bend radius SSC sulfide stress cracking TAN titrated acid number TEC thermal exchange coefficient

UV ultraviolet WPS welding procedure specification XLPE crosslinked polyethylene

F y anchoring system capacity n permissible stress utilization factor t thickness of component σe equivalent stress (von Mises or Tresca) σt tensile hoop stress σ y material yield stress σ u material ultimate stress

General

The purchaser shall specify the functional requirements for the flexible pipe The purchasing guidelines in

Annex B give a sample format for the specification of the functional requirements

Manufacturers must specify any functional requirements that are not explicitly stated by the purchaser, as these can influence the design, materials, manufacturing processes, and testing of the pipe.

If the purchaser does not specify a requirement, and the above does not apply, the manufacturer may assume that there is no requirement.

Overall Requirements

The manufacturer must demonstrate that the flexible pipe meets essential functional requirements, including providing a leak-tight conduit, withstanding all design loads and combinations as outlined in Section 5, ensuring performance throughout its specified service life, and using materials that are compatible with the surrounding environment.

The manufacturer must ensure that the end fittings of the flexible pipe fulfill specific criteria: they should create a structural connection between the flexible pipe and the support structure, and when necessary, they must also connect the flexible pipe to bend-limiting devices such as bend stiffeners, bend restrictors, and bellmouths, ensuring that these devices perform their intended functions effectively.

General Design Parameters

The purchaser must outline specific design requirements for the project, which include the nominal internal diameter (ID), the length and length tolerances of the flexible pipe along with end fittings, and the expected service life It is important to note that the length tolerance may be defined symmetrically around the nominal measurement or skewed to one side, depending on the system's criticality.

Internal Fluid Parameters

The buyer must define the internal fluid parameters relevant to the application, as detailed in Table 1 Additionally, any anticipated changes in these parameters throughout the service life should also be outlined.

Table 1—Internal Fluid Parameters Parameter Comment

Fluid composition See 4.4.4 Fluid/flow description Fluid type and flow regime

Flow rate parameters Flow rates, fluid density, viscosity, minimum inlet pressure, and required outlet pressure Thermal parameters Fluid heat capacity

The internal pressures that are relevant to the design, testing, and operation of an unbonded flexible pipe are defined in Figure 1 and Table 2

The following internal pressures shall be specified by the purchaser: a) design pressure, b) maximum operating pressure, c) incidental pressure

Purchasers must specify several key internal pressure data for their systems, including the operating pressure profiles throughout the pipe's service life, the system design pressure, and the pressure requirements for FAT, OLT, and offshore SIT as mandated by certifying authorities Additionally, it is essential to outline the maximum pressurization and depressurization rates, the number of extreme pressure cycles, and the minimum pressure, including any relevant vacuum pressure.

The internal temperatures that are relevant to the design, testing, and operation of an unbonded flexible pipe are defined in Table 3

The temperatures shown in Table 3 and the duration of the incidental temperature shall be specified by the purchaser

When specifying operating and design temperatures, it is essential to consider a minimum set of permanent operating factors, including the number and range of upset temperatures, the effects of gas cooling characterized by time/temperature curves, the thermal and flow characteristics of the fluid, as well as the conditions for storage, transport, and installation Additionally, the frequency of extreme temperature cycles, which may involve transitions from maximum to minimum operating temperatures and back, should also be taken into account, particularly in relation to pressure cycles.

Inc re a si n g Pres su re

Minimum pressure The minimum internal pressure experienced by the pipe during its life (installation and operating conditions) A conservative estimate is to assume a vacuum

Operating pressure The internal pressure profile experienced by the pipe during permanent normal operation over its service life

The maximum internal pressure, at a reference location (2) , to which the pipe is subjected during permanent normal operation

Design pressure The maximum internal pressure, at a reference location, including planned shut-in pressure and associated surge

System design pressure The lowest maximum internal pressure of the pipe system

The maximum internal pressure at a reference point is the highest level that is unlikely to be surpassed throughout the pipe's lifespan, even in cases of abnormal operation, unintended shut-in pressure, surge pressure, or other temporary incidental conditions.

Unless otherwise specified by the purchaser, the maximum incidental pressure is 1.1 times the design pressure

The internal pressure applied to the pipe or pipe section during testing after manufacture to test for latent defects

For flexible risers and topside jumpers, the Factory Acceptance Test (FAT) pressure is set at 1.5 times the design pressure, while for flexible flowlines and subsea jumpers, it is 1.3 times the design pressure If relevant, the maximum differential pressure may be utilized in place of the design pressure.

The internal pressure applied to the pipe or pipe section during testing after installation to test for leak tightness

Unless otherwise specified by the purchaser, the OLT pressure is 1.1 times either (a) the design pressure of the pipe or (b) system design pressure, whichever is lower

SIT (on-board integrity test) (3)

The internal pressure applied to the pipe or pipe section during testing on-board the installation vessel to test the structural integrity of the pipe

Unless otherwise specified by the purchaser the structural integrity test (SIT) pressure shall be as per the FAT pressure

The internal pressure applied to the pipe or pipe section during testing in situ after installation to test the structural integrity of the pipe

Unless otherwise specified by the purchaser the SIT pressure shall be 1.25 times either (a) the design pressure of the pipe or (b) system design pressure, whichever is lower

Burst pressure The pressure at which loss of fluid containment in the pipe occurs due to pipe or end fitting failure

NOTE 1 The pressure can be a function of location along the pipe and/or time

For injection or export risers, the reference location is typically at the topside, while for production risers, it should be at the wellhead or the equipment where the flexible pipe connects to a manifold, PLET, or PLEM.

The on-board structural integrity pressure test is essential when the pipe is completely retrieved and repaired on the installation vessel, particularly if the reinforcement layers or end-termination pressure containment components have been compromised.

The offshore structural integrity pressure test is essential after installation if the pipe has been repaired in situ, particularly when the integrity of reinforcement layers or end-termination pressure containment components is compromised This test is also necessary to evaluate the integrity in cases of suspected damage or reduced resistance.

Table 3—Temperature Definitions Temperature Definition

Operating temperature The internal (1) temperature profile experienced by the pipe over its service life during permanent normal operation

Maximum/minimum operating temperature The maximum and minimum internal temperature to which the pipe is subjected during permanent normal operation

Design temperature The maximum and minimum internaltemperature to which the pipe is subjected during permanent operation

Incidental (2) temperature The maximum and minimum internal temperature that is unlikely to be exceeded during the life of the pipe

NOTE 1 At the inner surface of the pipe

NOTE 2 Incidental temperatures should be specified on the basis of abnormal operating considerations, including unplanned transient events

NOTE 3 “Permanent” operating conditions are defined in Table 6

The purchaser must detail the composition of produced fluids, injected fluids, and both continuous and occasional chemical treatments, specifying dosages, exposure times, concentrations, and frequency The internal fluid composition should include parameters defining service conditions, such as the partial pressure or concentration of H₂S and CO₂, organic acids, pH of the aqueous phase, titrated acid number (TAN), and water content with ionic composition Additionally, it should cover gases like oxygen, hydrogen, methane, and nitrogen; liquids including oil composition and alcohols; aromatic components; corrosive agents such as bacteria and chlorides; injected chemical products for corrosion and scale inhibition; and solids like sand and biofilm Finally, it should also account for drilling, completion, or workover fluids, including dissolved oxygen concentrations.

External Environment

The buyer must define the external environmental parameters for the project, as outlined in Table 4 The design water depth will be determined by the maximum depth to which the pipe section may be subjected.

System Requirements

The purchaser is responsible for defining the system functional requirements for the project, with Annex B available for reference as a guideline Unless specified otherwise in section 4.6.1, the minimum system requirements outlined in sections 4.6.1.2 to 4.6.1.12 must be provided by the purchaser.

The flexible pipe system must include specifications for flowlines, risers, jumpers, and ancillary components It is essential to define the application of the flexible pipe as either static or dynamic, along with the anticipated number of load cycles and their magnitudes for dynamic scenarios Additionally, the global configuration of the flexible pipe should be clearly outlined.

Location Geographical data for the installation location

Water depth Design water depth, variations over pipe location, and tidal variations

Seawater data Density, salinity, pH value, and minimum and maximum temperatures

Air temperature Minimum and maximum during storage, installation, and operation

This article provides a comprehensive overview of soil data, focusing on key factors such as shear strength, internal friction angles, and friction coefficients related to seabed scour It describes various soil types, ranging from soft to hard, including sand and clay, while also addressing thermal conductivity, roughness, and grain size Additionally, it highlights soil stability, the potential for liquefaction, and the submerged or dry unit weight of soil The discussion includes the impact of sand waves and variations encountered along the pipe route.

Backfill and cover soil are essential materials characterized by their type, density, and key properties, which are crucial for UHB and related calculations and analyses Additionally, marine growth exhibits variations in density and thickness that depend on water depth, impacting overall assessments in marine environments.

Ice Maximum ice accumulation or drifting icebergs and ice floes

Sunlight exposure Length of pipe exposed during operation and storage conditions and time of exposure

Current data As a function of water depth, direction, and return period, and including the known effects of local current phenomena

Wave data encompasses significant and maximum wave heights, associated periods, wave spectra, spreading functions, and scatter diagrams, all analyzed based on direction and return period Wind data is evaluated according to direction, height above water level, and return period.

Corrosion protection for flexible pipes must address several key requirements, including internal and external protection for end fittings, implementation of a cathodic protection system, and specifications for protection voltage, current source, and current density Additionally, it is essential to consider protection measures for both on-shore and subsea storage, as well as installation processes Finally, compatibility with adjacent corrosion protection systems is crucial to ensure overall effectiveness.

The performance specifications for flexible pipes regarding heat loss or retention must be clearly defined The overall heat transfer coefficients (OHTC) should be determined based on the nominal internal diameter of the pipe, taking into account the pipe's characteristics as well as external factors, such as the soil cover for pipes that are buried.

A gas-venting system is essential for preventing excessive pressure buildup in the pipe's annulus Key specifications for gas venting include the components of the system, the required vented gas flow rate, and restrictions on venting locations Additionally, it is important to outline interface requirements, implement a gas-monitoring system, and consider underwater vent valves when applicable The back pressure of the vent system connected to the pipe and the integrity inspection of the annulus are also critical factors to ensure safety and efficiency.

4.6.1.6 Pigging and Through Flowline (TFL) Requirements

Any performance requirements for allowing tools for pigging, TFL, workover, or other operations through the flexible pipe, including ID, bend radius, and end-fitting transitions shall be specified

When specifying fire resistance requirements for a purchase, it is essential to include details such as the fire temperature, source, and surrounding materials, as well as the need for extinguishing or cooling the pipe structure Additionally, the fire-extinction method, required duration for pipe survivability, and the nature of the transported medium must be outlined Consideration should also be given to the heated steel in contact with polymeric materials in the flexible pipe, the pipe-abandonment facility and its fire protection capabilities, the pipe's function, the flashpoint of the transported medium in case of a leak, and the depressurization time.

Any piggyback requirements for the flexible pipe shall be specified, including details of the piggyback pipe(s) and pipe-operating conditions

The connector requirements for both end fittings in the flexible pipe shall be specified, including, as a minimum, connector type, welding specification, seal type, and sizes

The purchaser must specify various interface details, including applicable regulations, codes, and standards, along with definitions of code breaks Additionally, geometric and dimensional data, as well as imposed loading information, should be provided The purchaser is also responsible for supplying installation aids, equipment, pull-in and connection tools, and terminations Furthermore, details regarding vessel or platform interface structures, such as I-tubes and bellmouths, must be included, along with interfacing subsea equipment like christmas trees and manifolds Lastly, the scope of supply from the manufacturer should be clearly defined.

The requirements for the manufacturer to design and implement flexible pipe inspection, monitoring, and condition assessment systems and procedures shall be specified by the purchaser

Any requirements for shipping, storage, and handling with respect to all conditions, facilities, equipment, and procedures involved shall be specified

Performance requirements for installation and retrieval services must be clearly defined, including load restrictions, clamping and tensioner loads, vessel motions, and port facility limitations for purchaser-led operations Additionally, when the manufacturer is responsible for installation and retrieval, the purchaser should outline requirements related to seasonal conditions, environmental factors, vessel limitations, and the scope of installation activities, which encompass trenching, burial, testing, inspection, surveying, and documentation It is also essential to specify the handling of empty or flooded pipes and the anticipated number of operations.

Requirements for recoverability and reusability of the flexible pipe within its service life shall be specified

For effective pipe-cleaning operations utilizing exothermal chemical reactions, it is essential to define key parameters, including flow rate, pressure variation, maximum heat output, chemical composition, maximum temperature achieved during the reaction, temperature profile along the pipe, duration of the cleaning process, and the total number of cleaning operations planned throughout the pipe's service life.

The purchaser must specify additional requirements for the design and analysis of the flowline and riser (or jumpers) system to the manufacturer, taking into account the parameters outlined in Table 5 as a minimum, in addition to the requirements stated in Section 5.

Loads and Load Effects

The pipe design is based on the information supplied by the purchaser (see guidelines in Annex B), with reference to the requirements of Section 4

Loads are classified as functional (permanent and variable), environmental (external), or accidental Typical load combinations and load classes are listed in Table 6 and Table 7, respectively

The design load cases must be established to evaluate the impact of functional, environmental, and accidental loads on flexible pipes For analysis techniques related to these loads, refer to API 17B, which provides essential guidelines.

The flexible pipe design must demonstrate compliance with the design requirements outlined in section 5.1.3, considering all specified load combinations It is essential to evaluate the loads acting on the flexible pipe according to the conditions detailed in Table 6 Additionally, an analysis of the temporal and spatial variations of these loads, along with the load effects from the flexible pipe system and its supports, as well as environmental and soil conditions, is required.

The design load conditions to be analyzed include permanent operation (both normal and extreme), abnormal, temporary, and survival events Load combinations are specified in Table 6, with those having a yearly probability of occurrence less than \$10^{-4}\$ being disregarded The manufacturer will define FAT load combinations according to FAT procedures It is essential to consider various load combinations for extreme, interference, and fatigue analyses.

Design checks must be conducted for temporary conditions, including testing (FAT, OLT, SIT), installation, abandonment, retrieval, handling, and storage, as specified by the purchaser or manufacturer, in accordance with the design criteria outlined in Table 8.

The definition of simultaneous load combinations is essential, with the purchaser able to specify probabilities based on project-specific conditions Additionally, probabilities for accidental and installation-related events should also be provided by the purchaser In the absence of specified probabilities, the manufacturer will suggest appropriate probabilities for each individual event.

These specified probabilities must be consistent with the probabilities shown in Table 6 and mentioned above

The design load cases analyzed shall be derived from the load combinations in Table 6

Design loads give rise to tension/compression, bending, and torsion, which shall be considered in pipe design

In the pipe design, the manufacturer shall account for the effects of internal and external pressures

Hydrodynamic load effects must be assessed using validated methods that consider the kinematics of seawater and the interaction of various environmental phenomena, as outlined by API.

17B for guidelines on analysis methods

For effective fatigue analysis, it is essential to consider the complete distribution of loads throughout the pipe's service life, incorporating all relevant load parameters Simplified methods may be utilized, provided that the resulting load distribution is demonstrated to be conservative.

Accidental loads or their combinations can compromise the integrity of flexible pipes, making them unserviceable Load cases that involve such accidental loads, like increased offsets from anchor line or thruster failures, must adhere to the limits outlined in Table 8 to ensure safety Additionally, certain accidental loads, such as those resulting from fire and explosion, may pose challenges for analysis in accordance with established requirements.

Table 8 In such cases, testing shall be used to define safe working times of other limits associated with the accidental load

Design load cases must account for an intact annulus filled with condensed water and an annulus flooded with deaerated seawater, along with the relevant gas species for each scenario If the manufacturer, with the purchaser's agreement, can demonstrate through design and calculations a low likelihood of seawater entering the annulus, the flooded annulus condition may be treated as an accidental case.

In addition, the annulus flooded with aerated seawater shall be regarded as an accidental case

Table 5—Flowline and Riser Parameters

Flowline routing — Route drawings, topography, seabed/soil conditions, obstacles, and installed equipment and pipelines X X

— Specification of any requirements for the configuration, including description (lazy S, steep wave, etc.), layout, and components

— Selection of configuration or confirmation of suitability of specified configuration

— Functional, environmental and accidental load cases and combined yearly probability for permanent operation (normal and extreme), abnormal, temporary (e.g installation), and survival events

— Proposed geometry of guides, I-tubes, J-tubes, hangoff, and bellmouths through which flowline and riser is to be installed and mid- water arches

Pipe attachments — Bend restrictors, bend stiffeners, clamps, buoyancy modules, and attachment methods X X

— Descriptions of upper and lower connection systems, including quick disconnection systems and buoy disconnection systems, connection angles, and location tolerances

— Trenching, rock dumping, mattresses, external coatings, and extent of protection requirements over length of pipe

— Design impact loads, including those from trawl boards, dropped objects, and anchors/anchor chains

On-bottom stability — Allowable displacements X

Upheaval buckling — Specification of design cases to be considered by manufacturer X

Crossover requirements — Crossing of pipes (flexible and rigid), including already installed pipes and gas lines X X

Interference requirements — Specification of possible interference areas

— Definition of allowable interference/clashing X

The article discusses essential data for attached floating vessels, which encompasses vessel specifications such as dimensions, drafts, and headings, as well as static offsets It also includes first-order response amplitude operators for extreme and fatigue analyses, second-order motions, vessel motion phase data, and reference points Additionally, it addresses mooring system interface data and position tolerances.

Table 6—Load Combinations of Load Classes, Load Conditions

Load Conditions Operating Conditions Nonoperating Conditions

Temporary Normal Extreme Normal Extreme (2)

Permanent functional Permanent functional load associated with the corresponding load condition

Max./Min operating temp Design temp ≤ Incidental temp Purchaser-specified temperature

Environmental Operating plan ≥10 –2 ≤10 –2 Seasonal (8) Specified by purchaser ≥10 –4

NOTE 1 See Table 7 for details

NOTE 2 The environment cannot be controlled or the variable functional loads exceed the maximum incidental values

NOTE 3 Combined probability of occurrence, P c , refers to the combination of independent environmental conditions and accidental events only The occurrence probabilities refer to “yearly probability of occurrence.”

NOTE 5 “Assoc.” implies the functional loads associated with the load condition under consideration

NOTE 6 For extreme operating condition, the event itself may represent the condition following an accidental event (e.g with a mooring line failure)

NOTE 7 “X”—to be considered; see Table 7 for details of typical accidental loads

NOTE 8 Purchaser-specified return period If not specified assume a three-month return period

1) Loads due to weight and buoyancy of pipe, contents, and attachments, both temporary and permanent

3) External soil or rock reaction forces for trenched, buried, or rock dumped pipes

4) Static reaction and deformation loads from supports and protection structures

5) Temporary installation or recovery loads, including applied tension and crushing loads, impact loads, and guidance-induced loads

6) Residual installation loads, which remain as permanent loads in the pipe structure during service

7) Loads and displacement due to pressure and tension-induced rotation

8) Testing pressures, including installation, commissioning, and maintenance pressures

9) Interaction effects of bundled or clamped pipes

10) Loads due to rigid or flexible pipe crossings, or spans

11) Loads due to positioning tolerances during installation

12) Loads from inspection and maintenance tools

13) Loads from multiphase flow slugging, where applicable

14) Loads from restraint due to packaging (e.g FAT testing)

15) Internal pressure as specified in 4.4.2

16) Loads from pressure and temperature variations

1) Loads caused directly or indirectly (e.g VIV) by all environmental parameters specified in Table 4

2) Second-order slow drift motions and/or vortex induced motions of the floating facility or subsurface equipment to which the flexible riser is attached, where applicable

Loads and motions caused directly or indirectly by accidental occurrences involving external loads acting on the pipe, including the following

4) Compartment damage or unintended flooding of vessel compartment

8) Failure of turret drive system

9) Failure of relevant ancillary equipment that is likely to impact on the configuration of the pipe (e.g buoyancy or ballast module)

10) Internal pressure differential across a hydrate plug, where applicable

11) Interference between flexible pipe and other structures

S PECIFICATION FOR U NBONDED F LEXIBLE P IPE 27

Table 8—Flexible Pipe Layer Design Criteria

Inner liner smooth bore Collapse (1) Load

For every polymer material used in static and dynamic applications, the manufacturer must specify the permissible limits for collapse They are responsible for providing documentation that confirms the material meets the design requirements under the specified load conditions.

The maximum permissible reduction in wall thickness throughout the service life, due to deformation into gaps in the supporting structural layer, must not exceed 30% of the minimum design value under all load combinations.

For every polymer material used in static and dynamic applications, the manufacturer must specify the permissible bending strain and provide documentation confirming that the material satisfies the design requirements at that strain.

The maximum allowable bending strain for materials is 7.7% for polyethylene (PE) and polyamide (PA), 7.0% for polyvinylidene fluoride (PVDF) in static applications and during storage in dynamic applications, and 3.5% for PVDF in dynamic operational conditions.

Loss of interlock breakage Stress 0.67 0.85 0.85 0.67 0.91 (9) 0.85 0.97 (5)

Wire disorganization Displacement The cumulative radial gap between each tensile armor and its adjacent layers shall not exceed half the wire thickness

For every polymer material used in static and dynamic applications, the manufacturer must specify the permissible bending strain and provide documentation confirming that the material satisfies the design requirements at that strain.

Antibuckling tape Birdcaging (7) Stress or strain (8) 0.67 0.67 0.85 0.85 0.85 0.85 0.91

Pipe Design Methodology

The design methodology must encompass several key elements: a theoretical foundation with calculation procedures for pipe design parameters; a comprehensive calculation method for all pipe layers and components; and verification of the theoretical basis through prototype testing, ensuring the capacity of all structural layers Simplified conservative analysis methods are permissible for noncritical layers, provided they do not compromise the reliability of stress calculations in other layers Additionally, the methodology should include the basis for stress concentration factors related to steel materials, addressing stress concentrations at end-fitting interfaces, clamped accessories, and rigid surface contacts, as well as manufacturing tolerances and load-induced gaps It is essential to consider manufacturing tolerances, induced stresses or strains, welds, and other factors affecting structural capacity Verification of the service life methodology must adhere to specified requirements, and all layer material properties should align with the relevant tables Finally, material qualifications must comply with the designated tables for both the pipe and its components.

The pipe design methodology will be verified by an Independent Verification Authority (IVA) during initial assessments and subsequent revisions The IVA will determine the applicability range for each design methodology and ensure that the manufacturing process is adequately controlled to meet design requirements A certificate and a report outlining the limits and constraints of the design methodology will be issued by the IVA, and this verification report will be accessible for review by the purchaser.

The design methodology must consider the impacts of wear, corrosion, manufacturing processes, dimensional changes, creep, and aging caused by mechanical, chemical, and thermal degradation across all layers, unless the pipe design is explicitly documented to be unaffected by these factors.

Utilization levels outlined in Table 8 are determined by nominal dimensions and end-of-life conditions It is essential to demonstrate that any dimensional variations within manufacturing tolerances for the metallic and antibuckling layers do not result in utilization values exceeding the specified values in Table 8 by more than 3%.

The calculation of the thickness for all metallic layers shall include allowances for wear and uniform corrosion rates calculated for the service life

For a new pipe design, manufacturers must conduct adequate prototype testing to validate the design methodology and secure a revision or amendment of the design methodology verification report from an Independent Verification Authority (IVA).

The manufacturer must update the fabrication specifications to ensure that the design requirements are satisfied within the applicable design methodology range Prototype testing is essential to confirm the fitness-for-purpose of design parameters that fall outside the previously validated envelope For detailed guidelines on necessary tests and recommended procedures, refer to API 17B.

Pipe Structure Design

The pipe layers shall be designed to the criteria specified in Table 8, subject to the requirements of Section 5

The internal pressure sheath's utilization must be determined by considering the maximum allowable creep and strain of the polymer material, in accordance with the specifications outlined in section 5.3.2.1.

The manufacturer must assess buckling failure modes in the carcass, pressure armors, and tensile armors, confirming through analysis and testing that these layers fulfill design requirements Hydrostatic collapse calculations for the carcass should incorporate the support from the pressure armor layer The buckling load utilization for the internal carcass is determined by the differential pressure divided by the hydrostatic collapse resistance The methodology for calculating hydrostatic collapse resistance must be documented and based on the minimum value derived from a validated design approach, considering all sources of ovalization from manufacturing, testing, installation, operation, and loading in both axial and radial directions.

The manufacturer must assess the collapse failure mode caused by gas pressure accumulation between the pressure sheath and nearby sacrificial layers, ensuring that all design criteria are satisfied through analysis Additionally, the manufacturer should outline any operational limits on decompression rates related to this failure mode.

The calculation of utilization for the pressure and tensile armor layers can be determined through two methods: a) stress utilization, which is the average stress in the actual layer divided by the structural capacity; and b) load utilization, defined as the applied load divided by the load required to induce yielding or instability.

Stress calculations must adhere to the verified design methodology outlined in section 5.2 and meet the design requirements specified in 5.3.2 The calculated stress value should account for dynamic loads and be based on the average stress across the layer, which is determined by uniformly distributing the total layer load over all wires The structural capacity should be chosen as either 0.9 times the ultimate tensile strength or the yield strength, with a maximum limit of 0.9 times the ultimate tensile strength For design purposes, the structural capacity must be either the minimum specified value or the minimum value certified by the supplier, as long as it exceeds the minimum specified value.

Local armor wire stresses can surpass average layer stresses, particularly during bending According to section 5.3.4.3, fatigue analysis must focus on these local armor wire stresses Design considerations must address damage mechanisms that arise when local wire stresses exceed the average stress in the layer, ensuring that these local stresses are evaluated for their acceptability concerning the structural capacity and service life of the pipe.

Potential damage mechanisms include: a) gross yielding or deformation of armor wire cross sections, b) crack initiation in higher stress concentration areas of armor wire cross sections

For methodologies on evaluation of acceptability of local stresses refer to API 17B, Section 5.4.1

The utilization for the outer sheath shall be calculated based on the maximum allowable bending strain, subject to the requirements of 5.3.2.2

The storage minimum bend radius (SR) must be determined based on the minimum bend radius that meets all the criteria outlined in Table 8 Additionally, the bend radius necessary to prevent locking in the interlocked layers is also a critical consideration.

The locking radius (LR) has been calculated by the NISOC Library, and the safety radius (SR) must be at least 1.1 times the LR It is essential that the SR does not cause any damage or disruption to surrounding layers.

Table 9 presents the MBR criteria related to the SR and LR that must be met under various load conditions and combinations Furthermore, it is essential that the MBR is always greater than or equal to the SR for all load scenarios.

Note that a larger MBR than the criteria of Table 9 may be required to comply with the design criteria in

Table 8 or with the fatigue design requirements and factor of safety shown below

Table 9—Minimum Bend Radius Design Criteria

All types 1.0 × storage minimum bend radius (SR)

NOTE 1 Dynamic supported (i.e a flexible pipe on an arch or in a bellmouth)

NOTE 2 Quasi-dynamic loading includes the following cases typically applying to topside jumpers: a) no direct wave load on the flexible, b) predominantly displacement controlled

NOTE 3 Direct wave loading on the flexible pipe

Fatigue life calculations must be conducted for both intact annulus and annulus flooded with deaerated seawater, following the guidelines outlined in section 5.3.4 It is essential that the predicted fatigue life incorporates a safety factor of at least 10 times the expected service life.

A lower safety factor may be used for the annulus flooded with deaerated seawater condition based on expected operating conditions

The manufacturer must prove that the design criteria outlined in Table 8, along with all functional requirements, are met, taking into account the anticipated reduction in the cross-section of structural layers due to progressive wear, corrosion, and erosion by the end of the designated service life.

Reliability-based design serves as an alternative approach, necessitating the consideration of all pertinent design criteria The safety level implemented must receive approval from the purchaser.

5.3.2 Design Requirements for Pipe Layers

The internal pressure sheath must be evaluated for key load cases, including the most critical combination of internal pressure, temperature, operating MBR, and polymer conditions, considering scenarios such as an annulus at atmospheric pressure, an intact annulus, or an annulus flooded with deaerated seawater Additionally, the analysis should include hydrotest pressure at ambient temperature and storage MBR.

The analysis must encompass significant cyclic loading effects, including hysteresis, relaxation, shrinkage, loss of plasticizer, fluid diffusion, and absorption into the polymer matrix Key considerations include: a) creep and strain at operational temperature ranges due to gap bridging in the reinforcement layer; b) stress variations from pressure and temperature cycling caused by fluids within the pipe bore and annulus, including scenarios with unpressurized pipes; c) contact pressure from adjacent carcass and armor layers; d) creep and strain resulting from pipe bending, axial elongation, compression, torsion, and radial expansion; e) the weight of all layers adjacent to the pressure sheath that lack independent support in the end fitting; and f) alterations in material performance or properties due to aging.

The methodology for calculating the wall thickness of the internal pressure sheath must be validated through documented tests or field experience, adhering to specific minimum requirements Firstly, the gap between pressure armor or tensile armor wires used in the calculations should reflect the maximum gap during bending to the operating MBR, while also considering manufacturing tolerances Additionally, the analysis must incorporate factors such as thinning of the polymer layer from bending, stress concentrations from thickness variations, the impact of deplasticization, swelling, and aging on material properties, manufacturing tolerances, the creep behavior of the polymer material, and the termination of the layer at the end fitting.

Tiêu đề	Specification for Unbonded Flexible Pipe
Trường học	American Petroleum Institute
Chuyên ngành	Petroleum Engineering
Thể loại	Specification
Năm xuất bản	2014
Thành phố	Washington, DC

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