Patent Description:
The flexible pipe is used to transport production fluids, such as oil and/or gas and/or water from one location to another. The flexible pipe is generally formed of a plurality of layers that are concentric and superposed. The flexible pipe is for example a flexible pipe of a type that is not bonded (or "unbounded"). It is considered "unbounded" since the tensile armor layers of the pipe are free to move relative to each other during a flexion of the flexible pipe, i.e. the tensile armor layers are not embedded in a bonding material such as an elastomer.

In particular, the flexible pipe is a flexible pipe disposed across a body of water, between a bottom assembly designed for collecting a fluid at the bottom of the body of water, and a surface assembly designed for collecting and distributing the fluid. The surface assembly may be a semi-submersible platform, a floating production storage and offloading unit (FPSO), a ship, or any other floating unit such as a ship.

The flexible pipe is generally formed by an assembly of a flexible pipe body and at least one end fitting arranged at an end of the flexible pipe body. The end fitting provides a mechanical device forming a transition between the flexible pipe and a connector. Various layers of the flexible pipe are introduced to the end fitting and are sealingly engaged with a portion of the end fitting.

Generally, a hang-off system is provided to assemble the flexible pipe onto the surface assembly. The hang-off system allows transferring the vertical loads from the flexible pipe to the surface assembly. In particular, the hang-off system holds the end fitting in place in case of reaction due to an abrupt rupture of the flexible pipe top section.

Indeed, in use, the end fitting of the flexible pipe is subject to various forces including high tension and compression loads due to environmental factors such as temperature and pressure fluctuations and/or underwater currents. Moreover, the weight of the flexible pipe may also cause high stresses and strains in the end fitting. Through the lifetime of the flexible pipe, these forces may lead to structural failures of the flexible pipe, if used outside the design conditions and qualification envelope, or possible failure modes depending on the operational conditions.

It is then crucial to monitor forces acting on the top section of the flexible pipe over time to allow appropriate servicing when needed. Prior art hang-off systems and related techniques are disclosed in the following documents: <CIT>, <CIT>, <CIT>, <CIT> and <CIT>. In particular document <CIT> discloses a hang-off system for measuring a top tension in a flexible pipe where an annular collar comprises one top and one bottom plate. Strain gauges are provided at equal spacing around the circumference of the hang-off. Each strain gauge is provided adjacent a longitudinal cavity extending from the radially inner surface to the radially outer surface of the hang off.

An object of the invention is to provide a hang-off system fulfilling the requirements in term of structural resistance and allowing a reliable monitoring of the deformation of the top section of the flexible pipe and an easy installation on the surface assembly.

To the end, the subject-matter of the invention relates to a hang-off system for measuring a top tension in a flexible pipe, said flexible pipe comprising a flexible pipe body and a top end-fitting arranged at an end of the flexible pipe body, the hang-off system being intended to maintain the top end-fitting on a surface assembly, the hang-off system comprising :.

The hang-off system according to the invention may comprise one or more of the following features, provided they are within the scope of the dependent claims:.

The subject-matter of the invention also relates to an assembly comprising:.

The subject-matter of the invention also relates to a method for assembling a top end-fitting of a flexible pipe on a surface assembly with a hang-off system as described above, said method comprising the following steps:.

The method according to the invention may comprise one or more of the following features, provided they are within the scope of the dependent claims:.

The invention will be better understood upon reading the description which will follow, given solely by way of example, and with reference being made to the accompanying drawings in which:.

An assembly <NUM> according to the invention is shown in <FIG> and <FIG>. The assembly <NUM> comprises a flexible pipe <NUM>, a surface assembly <NUM> and a hang-off system <NUM> for maintaining an end <NUM> of the flexible pipe <NUM> on the surface assembly <NUM>. In the example of <FIG>, the assembly <NUM> further comprises a bottom assembly <NUM> submerged in a body of water <NUM>.

The flexible pipe <NUM> is used to transport production fluids, such as oil and/or gas and/or water from one location to another. The flexible pipe <NUM>, also referred as a riser, is intended to transport fluids from the bottom assembly <NUM> to the surface assembly <NUM>.

The flexible pipe <NUM> comprises a flexible pipe body <NUM> and one or more end fittings <NUM> along its length. An example of a flexible pipe body <NUM> is shown in <FIG>. The flexible pipe <NUM> comprises a top end fitting <NUM> maintained on the surface assembly <NUM> by the hang-off system <NUM>.

As shown in <FIG>, the flexible pipe body <NUM> is formed by a combination of layered materials delimiting a central passage <NUM> for circulation of fluids. For example, the flexible pipe body <NUM> comprises metallic layers, polymeric layers, composite layers, or a combination of different materials.

The flexible pipe body <NUM> comprises a pressure sheath <NUM> and an optional innermost carcass layer positioned inside the pressure sheath <NUM>.

The carcass layer is used to prevent collapse of the pressure sheath <NUM> due to pipe decompression, external pressure, and tensile armor pressure and mechanical crushing loads. The carcass layer is for example a metallic layer, formed from stainless steel. The carcass layer may also be formed from composite, polymer or other material, or a combination of materials. Flexible pipe bodies <NUM> may be used without a carcass layer and are referred as smooth bore. Alternatively, pipe bodies may be used with a carcass layer and are referred as rough bore.

The pressure sheath <NUM> acts as a fluid retaining layer and comprises a polymer layer ensuring internal fluid integrity. The pressure sheath <NUM> may comprise itself several sublayers.

The flexible pipe body <NUM> may comprise an optional pressure armor layer <NUM> around the pressure sheath <NUM>. The pressure armor layer <NUM> is a structural layer that increases the resistance of the flexible pipe <NUM> to internal and external pressures. The pressure armor layer <NUM> is for example made of metal, such carbon steel. The pressure armor layer <NUM> is for example made of a round or profiled wires helically wound along the length of the flexible pipe body <NUM> at a lay angle typically between about <NUM>° to <NUM>°. The profiled wires are preferably interlocked. The pressure armor layer <NUM> may also be formed from composite, or other material, or a combination of materials.

The flexible pipe body <NUM> may comprise an optional first tensile armor layer <NUM> and an optional second tensile armor layer <NUM>. Each tensile armor layer <NUM>, <NUM> is used to sustain tensile loads and internal pressure. The tensile armor layers <NUM>, <NUM> are generally formed by a plurality of metallic wires helically wound along the length of the flexible pipe body <NUM> at a lay angle typically between about <NUM>° to <NUM>°. The tensile armor layers <NUM>, <NUM> are often counter-wound in pairs. The tensile armor layers <NUM>, <NUM> are for example metallic layers. They could also be formed from composite, polymer or a combination of materials.

The flexible pipe body <NUM> also typically comprises optional layers of abrasion-resistant or anti-wear and insulation and an outer sheath <NUM> surrounded the inner layers. A carcass <NUM> may be disposed externally to the outer sheath <NUM>. Said layers comprises a polymer layer used to protect the pipe against penetration of seawater, corrosion, abrasion and mechanical damage.

The end fitting <NUM> is located at one end <NUM> of the flexible pipe body <NUM>. The end fitting <NUM> extends along a first axis A1. The end fitting <NUM> comprises and end fitting body <NUM> delimiting an internal bore running along the first axis A1, and a casing assembled to the end fitting body <NUM>, for example through bolts or other securing members.

The casing is sealed to the flexible pipe body <NUM> and in particular to the outer sheath <NUM> of the flexible pipe body <NUM>.

The end fitting body <NUM> extends from a first end <NUM> delimiting an open-mouth region receiving an end <NUM> of the flexible pipe body <NUM>, to a second end <NUM>, forming a connector <NUM>.

The connector <NUM> is a substantially disk-liked flared region. The connector <NUM> may be connected to a matching connector of a further end fitting body of an adjacent flexible pipe, or to a pipe of the surface assembly <NUM>.

In the example of <FIG>, the flexible pipe <NUM> is disposed across the body of water <NUM>, between the bottom assembly <NUM> designed for collecting a fluid at the bottom of the body of water <NUM>, and the surface assembly <NUM> designed for collecting and distributing the fluid. The surface assembly <NUM> may be a semi-submersible platform, a floating production storage and offloading unit (FPSO), a ship, or any other floating unit such as a ship.

The hang-off system <NUM> is provided to maintain the flexible pipe <NUM> onto the surface assembly <NUM>. The hang-off system <NUM> allows transferring the vertical loads from the flexible pipe <NUM> to the surface assembly <NUM>. In particular, the hang-off system <NUM> holds the end fitting <NUM> in place onto the surface assembly <NUM> in case of reaction due to an abrupt rupture of the flexible pipe <NUM>.

In the example of <FIG> and <FIG>, the surface assembly <NUM> comprises a support <NUM> projecting from a surface <NUM> of the surface assembly <NUM>. The support <NUM> is for example a cylindrical tube <NUM>, referred in the prior art as "I-Tube", protruding from the surface <NUM> of the surface assembly <NUM> according to the first axis A1 substantially perpendicular to the surface <NUM>. The support <NUM> delimits a conduit in communication with the body of water <NUM> and allowing the passage of the flexible pipe <NUM>. The support <NUM> comprises a top annular surface <NUM> connected to the hang-off system <NUM>. Preferably, the top annular surface <NUM> defines a plurality of holes receiving fasteners for assembling the hang-off system <NUM> to the support <NUM>.

According to the invention, the hang-off system <NUM> comprises an annular collar <NUM> extending along the first axis A1, and a data acquisition system <NUM>.

As schematically shown in <FIG> and <FIG>, the annular collar <NUM> delimits a central passage <NUM> receiving the flexible pipe <NUM>, and in particular the end fitting <NUM> of the flexible pipe <NUM>. The annular collar <NUM> is arranged around the top end fitting <NUM> of the flexible pipe <NUM>. The annular collar <NUM> entirely surrounds the end fitting <NUM>. Preferably, the annular collar <NUM> mechanically cooperates with an annular grove <NUM> defined in the side wall <NUM> of the end fitting <NUM>. The annular collar <NUM> is fixed above the support <NUM> of the surface assembly <NUM> in contact with the top annular surface <NUM> and fixed to the support <NUM> with a plurality of fixation members.

According to the invention, the annular collar <NUM> is formed by at least two parts <NUM> assembled to each other. Each part <NUM> surrounds a portion, in particular an angular portion, of the side wall <NUM> of the end fitting <NUM> around the first axis A1.

In the first embodiment, the annular collar <NUM> comprises exactly three parts <NUM> assembled to each other to form the annular collar <NUM>. Each part <NUM> of the annular collar <NUM> extends along a circular arc in a plane substantially perpendicular to the first axis A1 between a first end <NUM> and a second end <NUM>, around the end fitting <NUM>. In the first embodiment, the circular arc has an angle substantially equal to <NUM>°.

According to the invention, each part <NUM> comprises a top plate <NUM> and a bottom plate <NUM> assembled to the top plate <NUM>. The top plate <NUM> and the bottom plate <NUM> delimit an intermediate space <NUM> between them. At least one part <NUM> comprises at least one load cell <NUM> arranged in the intermediate space <NUM> and sandwiched between the top plate <NUM> and the bottom plate <NUM>.

The top plate <NUM> is arranged above the bottom plate <NUM> according to the first axis A1. The top plate <NUM> extends in a first plane substantially perpendicular to the first axis A1. The top plate <NUM> extends along a circular arc in the first plane between a first end <NUM> and a second end <NUM>. In the first embodiment, the circular arc has an angle substantially equal to <NUM>°. The top plate <NUM> defines a top surface <NUM> and a bottom surface <NUM> arranged opposite the top surface <NUM>. The top surface <NUM> is oriented towards the connector <NUM>. The bottom surface <NUM> is oriented towards the intermediate space <NUM>. The top surface <NUM> and the bottom surface <NUM> are substantially parallel to each other.

Preferably, the top plate <NUM> comprises at least a first upper assembling portion <NUM> located at the first end <NUM> and a second upper assembling portion <NUM> located at the second end <NUM>. For example, the first upper assembling portion <NUM> and the second upper assembling portion <NUM> protrude from the top surface <NUM> of the top plate <NUM> opposite the intermediate space <NUM>. Preferably, the first upper assembling portion <NUM> and the second upper assembling portion <NUM> extend in respective radial planes relative to the first axis A1. In addition or alternatively, the top plate <NUM> comprises at least a first lower assembling portion <NUM> located at the first end <NUM> and a second lower assembling portion located at the second end <NUM>. For example, the first lower assembling portion <NUM> and the second lower assembling portion protrude from the bottom surface <NUM> of the top plate <NUM> towards the intermediate space <NUM>. Preferably, the first lower assembling portion <NUM> and the second lower assembling portion extend in respective radial planes relative to the first axis A1. Preferably, the first upper assembling portion <NUM> and the first lower assembling portion <NUM> extend in the same radial plane. Preferably, the second upper assembling portion <NUM> and the second lower assembling portion extend in the same radial plane.

The top plates <NUM> of the parts <NUM> of the annular collar <NUM> are assembled to each other through the first upper and/or lower assembling portions <NUM>, <NUM> and the second upper and/or lower assembling portions <NUM>. For example, the assembling portions <NUM>, <NUM>, <NUM> of the parts <NUM> are bolted to each other.

The top plate <NUM> may also comprise lifting members <NUM>, such as lifting hooks, protruding from the top surface <NUM> of the top plate <NUM> to ease the handling of the hang-off system <NUM> with a hoisting device (not shown).

The bottom plate <NUM> is arranged below the top plate <NUM> according to the first axis A1. The bottom plate <NUM> extends in a second plane substantially perpendicular to the first axis A1 and substantially parallel to the first plane. The bottom plate <NUM> extends facing the top plate <NUM>. The bottom plate <NUM> extends along a circular arc in the second plane between a first end <NUM> and a second end <NUM>. In the first embodiment, the circular arc has an angle substantially equal to <NUM>°. The bottom plate <NUM> defines a top surface <NUM> and a bottom surface <NUM> arranged opposite the top surface <NUM>. The top surface <NUM> is oriented towards the intermediate space <NUM>. The bottom surface <NUM> is oriented towards the support <NUM>. The top surface and the bottom surface are substantially parallel to each other.

Preferably, the bottom plate <NUM> comprises at least a first upper assembling portion <NUM> located at the first end <NUM> and a second upper assembling portion <NUM> located at the second end <NUM>. For example, the first upper assembling portion <NUM> and the second upper assembling portion <NUM> protrude from the top surface <NUM> of the bottom plate <NUM> towards the intermediate space <NUM>. Preferably, the first upper assembling portion <NUM> and the second upper assembling portion <NUM> extend in respective radial planes relative to the first axis.

The bottom plates <NUM> of the parts <NUM> of the annular collar <NUM> are assembled to each other through the first upper assembling portions <NUM> and the second upper assembling portions <NUM>. For example, the assembling portions <NUM>, <NUM> of the parts <NUM> are bolted to each other.

The bottom plate <NUM> is preferably bolted to the support <NUM> and in particular to the top annular surface <NUM> of the support <NUM>.

Advantageously, each part <NUM> comprises at least one fastener <NUM>, preferably two fasteners <NUM>, and associated locknuts <NUM> to assemble the top plate <NUM> and the bottom plate <NUM> to each other. Each fastener <NUM> extends through the intermediate space <NUM> along an axis substantially parallel to the first axis A1. For example, the fasteners <NUM> are regularly distributed angularly around the first axis A1. In addition, the fasteners <NUM> may be arranged along a plurality of radial directions relative to the first axis A1.

The fasteners <NUM> and the locknuts <NUM> are critical for the hang-off system <NUM> since they allow controlling the alignment of the top plate <NUM> with respect to the bottom plate <NUM>. As it will be described in details later, they allow the creation of an independent measurement module formed by a part <NUM> of the annular collar <NUM> avoiding any kind of loose parts and complex assembly during the offshore installation. The fasteners <NUM> and locknuts <NUM> allow a proper preparation of each part <NUM> of the annular collar <NUM> avoiding inaccurate and unequal tightening effect from one part <NUM> to another one. This improve the reliability and the accuracy of the measurements performed with the hang-off system <NUM>. Each part <NUM> is pre-assembled with its top plate <NUM> and bottom plate <NUM> onshore after factory acceptance test. The fasteners <NUM> and the locknuts <NUM> ensure that the hang-off system <NUM> is assembled offshore, using the same parts in the same place. This improves the traceability. The fasteners <NUM> and the locknuts <NUM> also have a key role regarding the structural integrity. The fasteners <NUM> and the locknuts <NUM> allow fulfilling the requirements to resist explosion, i. e, unpredicted and abnormal force applied in the upward direction. The fasteners <NUM> and the locknuts <NUM> do not allow lateral or angular movements between the top plate <NUM> and the bottom plate <NUM>.

Preferably, each part <NUM> comprises at least one load cell <NUM> arranged in the intermediate space <NUM> and sandwiched between the top plate <NUM> and the bottom plate <NUM>. In the first embodiment, the hang-off system <NUM> comprises exactly three load cells <NUM>. Each part <NUM> comprises exactly one load cell <NUM> arranged in the intermediate space <NUM>. Preferably, the load cells <NUM> are regularly spaced around the first axis A1. Using three load cells <NUM> is advantageous since they provide a stable support for the top plates <NUM>. The leveling of the load cells <NUM> is also easier. However, in a variant, each part <NUM> comprises several load cells <NUM>, for example a number of load cells <NUM> comprised between <NUM> and <NUM>. In any case, the loads cells <NUM> are leveled to each other.

Each load cell <NUM> is configured to sense a parameter representative of an axial load applied between the top plate <NUM> and the bottom plate <NUM>. Each load cell <NUM> is configured to convert a load applied between the top plate <NUM> and the bottom plate <NUM> into a corresponding electrical signal sent to the data acquisition system <NUM>. For example, each load cell <NUM> comprises at least one load sensor, preferably a plurality of load sensors for redundancy. For example, each load cell <NUM> is a vibrating wire load cell comprising at least one vibrating wire sensor, preferably a plurality of vibrating wire sensors. In a variant, the load cell <NUM> is a strain gauge load cell, a pneumatic load cell, a capacitive load cell, a hydraulic load cell or a piezoelectric load cell.

Each load cell <NUM> rests against the bottom surface <NUM> of top plate <NUM> and against the top surface <NUM> of the bottom plate <NUM>. Each load cell <NUM> extends according to an axis substantially parallel to the first axis A1. Advantageously, the bottom surface <NUM> of the top plate <NUM> and/or the top surface <NUM> of the bottom plate <NUM> define a convex surface <NUM> (<FIG>) protruding towards the intermediate space <NUM> and in contact with the load cell <NUM>. This allow to ensure a good contact between the load cell <NUM> and the top plate <NUM>/bottom plate <NUM> and reduce additional measurement uncertainties that a flat-to-flat contact may induce.

Advantageously, at least one part <NUM> of the annular collar <NUM> may comprise at least one shim <NUM>, schematically shown in <FIG>, arranged between the top surface <NUM> of the bottom plate <NUM> and the load cell <NUM> to compensate machining tolerance which can generate a difference between the heights of the load cells <NUM> and affect the data reliability. During the onshore assembly of the part <NUM>, if required, the operator easily compensates the height difference of each load cell <NUM> by using a circular shim of a thickness comprised between <NUM> and <NUM> for example. In other words, the shims allow leveling the load cells <NUM> between each other.

Each load cell <NUM> is connected to the data acquisition system <NUM> to monitor the time variations of the parameter representative of the load applied between the top plate <NUM> and the bottom plate <NUM> of each part <NUM> of the annular collar <NUM>. The data acquisition system <NUM> may comprise a memory to record the values of the parameter representative of the load applied between the top plate <NUM> and the bottom plate <NUM>, and/or a display device (not shown) to display the values of the parameter.

Advantageously, each part <NUM> of the annular collar <NUM> comprises at least a first reinforcement element <NUM> protruding from the top plate <NUM> towards the intermediate space <NUM>, and a second reinforcement element <NUM> protruding from the bottom plate <NUM> towards the intermediate space <NUM>. The first reinforcement element <NUM> is arranged facing the second reinforcement element <NUM> along a direction substantially parallel to the first axis A1. When the hang-off system <NUM> is assembled, the first reinforcement element <NUM> and the second reinforcement element <NUM> are separated by a gap comprised between <NUM> and <NUM>.

The reinforcement elements <NUM>, <NUM> are conservative features to avoid operational problems caused by an unexpected and unpredicted abnormal load. They act as a support and do not allow vertical deflection, improving the structural resistance of the hang-off system <NUM> in case a load cell <NUM> structurally fails. The reinforcement elements <NUM>, <NUM> allow not depending on the load cell <NUM> integrity to ensure operational continuity and the correct functioning of the hang-off system <NUM>.

Preferably, each part <NUM> comprises a plurality of first reinforcement elements <NUM> and a plurality of second reinforcement elements <NUM> arranged around the first axis A1.

For example, at least a part of the first reinforcement element <NUM> may be formed by the lower assembling portions <NUM> of the top plate <NUM>. At least a part of the second reinforcement elements <NUM> may be formed by the upper assembling portions <NUM>, <NUM> of the bottom plate <NUM>.

A method <NUM> for assembling a top-end fitting <NUM> of a flexible pipe <NUM> on a surface assembly <NUM> with a hang-off system <NUM> as described above is now described in reference to <FIG>.

The method <NUM> comprises a preparation step <NUM> preferably performed onshore. During this step <NUM>, each part <NUM> of the annular collar <NUM> is assembled independently from each other. In particular, for each part <NUM> of the annular collar <NUM>, the top plate <NUM> and the bottom plate <NUM> are assembled to each other without torque using the fasteners <NUM> and the locknuts <NUM>. The at least one load cell <NUM> is arranged in the intermediate space <NUM>. In the first embodiment, three independent assembled parts <NUM> are obtained.

Advantageously, the preparation step <NUM> comprises a factory acceptance test and/or a site acceptance test and/or a calibration test <NUM>. In particular, preferably, the preparation test <NUM> comprises pre-assembling <NUM> the parts <NUM> of the annular collar <NUM> to each other before performing the factory acceptance test and/or the site acceptance test and/or the calibration test <NUM>, and disassembling <NUM> the parts <NUM> from each other after the factory acceptance test and/or the site acceptance test and/or the calibration test are completed.

The hang-off system <NUM> may now be assembled to the end fitting <NUM> offshore during an assembling step <NUM>. During this step <NUM>, the annular collar <NUM> is formed by assembling the parts <NUM> to each other around the end fitting <NUM> and by assembling the parts to the surface assembly <NUM> via the top surface <NUM> of the support <NUM>. For example, each part <NUM> is moved using a hoisting device.

The assembling method <NUM> is very advantageous since each part <NUM> of the annular collar <NUM> is independently pre-assembled, tested and calibrated, preferably onshore. The offshore installation is easier since it only requires assembling the parts <NUM> between each other. The method <NUM> ensures traceability a low risk of losing parts.

A second embodiment is now described in reference to <FIG>. This embodiment is described by differences with respect to the first embodiment.

In this embodiment, the annular collar <NUM> is formed by exactly two parts <NUM> assembled to each other. Each part <NUM> of the annular collar <NUM> extends along a circular arc in a plane substantially perpendicular to the first axis A1 between a first end <NUM> and a second end <NUM>, around the end fitting <NUM>. In the second embodiment, the circular arc has an angle substantially equal to <NUM>°. In the second embodiment, the hang-off system <NUM> comprises exactly three load cells <NUM>, preferably regularly spaced around the first axis A1. A first part <NUM> among the two parts <NUM> comprises one load cell <NUM> and a second part <NUM> among the two parts <NUM> comprises two load cells <NUM>.

The assembling method <NUM> described above is similar for this embodiment.

In a variant of the first embodiment and of the second embodiment, the assembly <NUM> may comprise an apparatus (not shown) for inspecting and monitoring the internal structures of the flexible pipe, specifically the armor layers <NUM>, <NUM> of the flexible pipe body <NUM>. The apparatus comprises optical sensors, such as strain gauges based on Fiber Bragg Grating (FBG) technology attached to each wire of the outer armor layer. The strain measurements provided by these sensors make it possible to identify broken wires and detect events associated with wire ruptures. <NPL>, <CIT> and <CIT> disclose an example of such kind of apparatus called MODA (for "Monitoring based on Optical fiber attached Directly on Armor wires") and developed by the company Petrobras.

Advantageously, in this variant of the first and second embodiments of the invention, the load cells <NUM> of the hang-off system <NUM> according to the invention are fiber optic load cells. The data acquisition system <NUM> is then connected to both the loads cells <NUM> of the hand-off system <NUM> and the optical sensors of the apparatus for inspecting and monitoring the internal structures of the flexible pipe <NUM>. This is particularly advantageous since only one single data acquisition system <NUM> is used to record both kind of measurements.

Claim 1:
A hang-off system (<NUM>) for measuring a top tension in a flexible pipe (<NUM>), said flexible pipe (<NUM>) comprising a flexible pipe body (<NUM>) and a top end-fitting (<NUM>) arranged at an end of the flexible pipe body (<NUM>), the hang-off system (<NUM>) being intended to maintain the top end-fitting (<NUM>) on a surface assembly (<NUM>), the hang-off system (<NUM>) comprising :
- an annular collar (<NUM>) extending along a first axis (A1), the annular collar (<NUM>) being intended to be arranged around the top end-fitting (<NUM>), the annular collar (<NUM>) being formed by at least two parts (<NUM>) assembled to each other, each part (<NUM>) comprising a top plate (<NUM>) and a bottom plate (<NUM>) assembled to each other, said top plate (<NUM>) and bottom plate (<NUM>) delimiting an intermediate space (<NUM>) between them, at least one part (<NUM>) comprising at least one load cell (<NUM>) arranged in the intermediate space (<NUM>) and sandwiched between the top plate (<NUM>) and the bottom plate (<NUM>), the bottom plate (<NUM>) being intended to be assembled on the surface assembly (<NUM>),
- a data acquisition system (<NUM>) connected to the load cell (<NUM>).