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DNV-OS-E303 Offshore Mooring Fibre Ropes
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CHAPTER 1
Introduction
Ch.1
SECTION 1
GeneralCh.1 Sec.1
A. About this standard
Ch.1 Sec.1
A 100 Introduction
Ch.1 Sec.1 A
101 This Standard covers requirements to certification of fibre-rope
assemblies for offshore mooring.
Ch.1 Sec.1 A
102 Chapter 1 (this chapter) provides a general introduction with
overview, definitions, general provisions and references relevant
for Chapter 2 and Chapter 3. Chapter 2 provides the technical provisions
of this standard. Chapter 3 covers the process of certification.Ch.1 Sec.1
A 200 Objective
Ch.1 Sec.1 A
201 The objective of this standard is to ensure that the design
and manufactured quality of fibre-rope assemblies meet the requirements
of designated locations, handling and service scenario for offshore applications,
thereby providing the basis for ensuring reliable fibre-rope moorings.Ch.1 Sec.1
A 300 Scope
Ch.1 Sec.1 A
301 This standard specifies the requirements for the materials,
design, manufacture and testing of offshore mooring fibre ropes,
which are subject to classification or certification. It may also
serve as a technical reference document in contractual matters between
user and manufacturer. Ch.1 Sec.1
A 400 Application
Ch.1 Sec.1 A
401 This standard is applicable for fibre ropes used as taut mooring
lines on offshore units. It may also be used for semi-taut and catenary
mooring systems where only a portion contains fibre-rope segments
Typical applications are long-term mooring of floating production
systems and mooring of mobile offshore units. It also applies to
fibre-rope mooring lines for other offshore installations, such
as wave-, wind- or current energy plants.
Ch.1 Sec.1 A
402 Application is limited to cases where the cyclic ranges do
not exceed 40% MBS. Qualification for applications with
larger cyclic loadings can be performed based on DNV-RP-A203. Ch.1 Sec.1
A 500 Types of Offshore Mooring Fibre
Rope Assemblies
Ch.1 Sec.1 A
501 The fibre-rope assembly includes fibre rope segment with termination
hardware. Normally thimbles are used in spliced eyes, and the connecting
element is outside the scope of this standard.
Ch.1 Sec.1 A
502 The jacket on the fibre-rope segment shall be permeable so
as to ensure that the rope is free flooded. For conditions with
exposure to sunlight, such as application in shallow water and onshore
storage, the jacket shall be sufficiently dense to protect the load-bearing
core rope from sunlight.
Ch.1 Sec.1 A
503 Fibre-rope segments of mooring lines can be of various constructions.
Some examples of different types of rope constructions are shown
in Figure 1.
(A) Parallel-Subrope rope.
(B) Six-Strand rope.
(C) Thirty-Six-Strand rope.
(D) Parallel-yarn rope.
Fig. 1 Overview of types of rope
Ch.1 Sec.1 A
504 At the time of this standard, the most commonly used type
of fibre rope for offshore moorings consists of parallel subropes
held together by a braided jacket. The subropes consist of strands
in helical (laid) or braided arrangement. The helical subropes typically
use three or four strands, whereas the braided subropes typically use
eight or twelve strands. The size and number of subropes to make
up the load-bearing core of the fibre rope varies between manufacturers.
Rope constructions resembling steel-wire rope are also used, either
as subropes or as the fibre rope.
Ch.1 Sec.1 A
505 Fibre-rope segments in mooring lines are normally protected
by an outer sheathing. A filter should be incorporated in this sheathing
to protect the load-bearing subropes from particles.
Ch.1 Sec.1 A
506 In mooring lines containing chain or torque-neutral wire rope,
a torque-neutral fibre rope should be used. Torque-neutral fibre
ropes either have braided subropes or helical subropes where 50% are
S-lay and 50% Z-lay. In mooring lines containing
6-strand wire rope or similar, the fibre rope should be constructed
with similar torque/rotation characteristics as the remainder
of the mooring line.
Ch.1 Sec.1 A
507 Fibre ropes are normally terminated with spliced eyes to make
up the fibre rope segment.Guidance note:
For other types of fibre-rope terminations than the spliced
eye an appropriate level of qualification is required as defined
in DNV-RP-A203. ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Ch.1 Sec.1 A
508 The eye size is usually determined as the dimension from the
inside back of the eye to the crotch of the eye with two legs of
the eye close together. The profile of the spool should also be
specified.
Fig. 2 Fibre-rope segment fitted on spool thimble
This is an illustration. The actual design of the termination
is part of the fibre-rope assembly design as determined by the manufacturer.
Ch.1 Sec.1 A
509 The spliced eyes should be fitted on thimbles. Thimbles act
as the interface between the rope eye and the pin of the connecting
element.
Ch.1 Sec.1 A
510 Termination hardware is required to fit and support the eye
and should be made of steel.
Guidance note:
For termination hardware made from other materials than steel
should be qualification in accordance with DNV-RP-A203 ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Ch.1 Sec.1 A
511 If the fibre rope segment is connected directly to a custom-designed
element, then that element is considered termination hardware.
Ch.1 Sec.1 A
512 Shackles and H-links shall comply with DNV-OS-E302. Sockets
shall comply with DNV-OS-E304.Ch.1 Sec.1
A 600 Load-bearing yarns
Ch.1 Sec.1 A
601 This standard covers fibre ropes that are manufactured using
polyester, polyamide, HMPE, aramid and LCAP yarn materials. The
synthetic yarns shall be suitable for offshore mooring (i.e. offshore
grade).
Ch.1 Sec.1 A
602 The fibre yarns used in mooring ropes shall be fit for the
designated service. The load bearing yarns shall be able to sustain
loading within the entire design range, and have sufficient performance
with respect to stress rupture or creep failure, as well as sufficient
abrasion resistance and sufficiently low variability in force versus stretch
characteristics.Guidance note:
Standard for Certification No. 2.9, Approval Programme No.
322 "Yarns for offshore mooring fibre ropes" has
been formulated to take these aspects into account.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Ch.1 Sec.1
A 700 Service requirements
Ch.1 Sec.1 A
701 Protective tarpaulin applied to cover the fibre-rope segments
on transportation reels should be white.
Ch.1 Sec.1 A
702 The entire length of fibre rope shall be submerged at all
times during service; and the fibre-rope segment shall be free flooded,
including in the eye regions.
Ch.1 Sec.1 A
703 Fibre rope assemblies should in general not be in contact
with the seabed during installation or handling. Provided the protection
against soil ingress has been duly qualified, fibre-rope assemblies
may be placed on the sea bed as part of the installation and handling
procedure, pending retrieval and final hook up.
Ch.1 Sec.1 A
704 The lower parts of the fibre rope shall not be in contact
with the sea bed during service, nor be handled or left in service
in water with emulsified particles that may be transported into
the load-bearing rope by the water that seeps in and out during
loading.Guidance note:
The filter serves as protection for unloaded rope.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Ch.1 Sec.1 A
705 The load bearing parts of the fibre rope shall be adequately
protected from marine growth. Hard marine growth shall not occur
on load-bearing yarns.
Ch.1 Sec.1 A
706 A mobile mooring system shall be operated with the required
margins against failure, ref. DNV-OS-E301. The procedure for handling
and installation shall be adhered to.
Ch.1 Sec.1 A
707 A long-term mooring system shall be operated with the required
margins against failure, ref. DNV-OS-E301. The in-service condition
scheme shall be adhered to.Guidance note:
For a mobile mooring system it is a requirement of DNV-OS-E301
that the margins against stress rupture or creep failure is minimum
3. For long-term mooring, the margin against stress rupture shall
be 5 - 8. These margins are commensurate to the margins
against fatigue failure of steel components.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Ch.1 Sec.1 A
708 The mooring line loading shall be kept within the design range
as stated on the certificate.Ch.1 Sec.1
A 800 Special Service
This standard is applicable to offshore-mooring fibre ropes
in a regular service scenario. The following applications are considered
special service that requires additional qualification activities:
| — | sea-bed contact during the installation
phase |
| — | service with physical contacts to objects such as work
wires |
| — | service in shallow water where ample marine growth occurs |
| — | service where part of the rope is above water. |
Ch.1 Sec.1
A 900 Fibre-rope repair
Ch.1 Sec.1 A
901 Methods exist for repair of fibre-rope assemblies. As a general
rule, the load-bearing subropes in long-term mooring systems should
not be repaired. All repair methods shall be duly qualified. Guidance note:
Information concerning fibre-rope damage assessment and repair
can be found in DNV-RP-E304, API RP2I, ISO 18692 and CI 2001-04.---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Ch.1 Sec.1
B. References
Ch.1 Sec.1
B 100 General
Ch.1 Sec.1 B
101 In case of conflict between requirements of this standard
and a reference document, the requirements of this standard shall
prevail.
Ch.1 Sec.1 B
102 The latest edition of the referenced document (including amendments)
should apply.Ch.1 Sec.1
B 200 Normative References
Ch.1 Sec.1 B
201 The referenced documents listed in Tables B1 through B3 include
provisions, which through reference in the text constitute provisions
of this standard.Ch.1 Sec.1 B
| Table B1 DNV Offshore
Standards |
| Reference | Title |
| DNV-OS-B101 | Metallic Materials |
| DNV-OS-C401 | Fabrication and Testing of Offshore Structures. |
| DNV-OS-E301 | Position Mooring. |
| DNV-OS-E302 | Offshore Mooring Chain. |
| DNV-OS-E304 | Offshore Mooring Steel Wire Ropes. |
Ch.1 Sec.1 B
| Table B2 DNV Recommended
Practices |
| Reference | Title |
| DNV-RP-A203 | Qualification Procedures for New Technology. |
| DNV-RP-E304 | Damage Assessment of Fibre Ropes for
Offshore Mooring. |
Ch.1 Sec.1 B
| Table B3 Other Reference |
| Reference | Title |
| ASTM D885M | Standard Test Method for Tire Cords,
Tire Cord Fabrics, and Industrial Filament Yarns Made from Manufactured
Organic-Base Fibres |
| CI 1503 | Test Method for Yarn-on-Yarn Abrasion. |
| ISO 3344 | Reinforcement products - Determination
of moisture content |
Ch.1 Sec.1
B 300 Informative references
Ch.1 Sec.1 B
301 The referenced documents listed in Tables B4 through B6 may
be useful to the users of this standard.Ch.1 Sec.1 B
| Table B4 DNV Offshore
Standard |
| Reference | Title |
| DNV-OS-C501 | Composite Components. |
Ch.1 Sec.1 B
| Table B5 DNV Offshore
Service Specifications |
| Reference | Title |
| DNV-OSS-101 | Rules for Classification of Offshore
Drilling and Support Units. |
| DNV-OSS-102 | Rules for Classification of Floating
Production and Storage Units. |
| DNV-OSS-401 | Technology Qualification Management. |
Ch.1 Sec.1 B
| Table B6 DNV Standard
for Certification |
| Reference | Title |
| No.2.9 | Approval Programme No. 321 "Offshore
mooring fibre ropes" |
| No.2.9 | Approval Programme No. 322 "Yarns
for offshore mooring fibre ropes" |
Ch.1 Sec.1 B
| Table B7 Other References |
| Reference | Title |
| API RP 2I | In-service Inspection of Mooring Hardware
for Floating Structures. |
| API RP 2SK | Design and Analysis of station-keeping
systems for Floating Structures. |
| API RP 2SM | Recommended Practice for Design, Manufacture,
Installation, and Maintenance of Synthetic Fibre Ropes for Offshore
Mooring. |
| ASTM D6611 | Standard Test Method for Wet and Dry
Yarn-on-Yarn Abrasion Resistance. |
| CI 1500 | Test methods for fibre rope. |
| CI 2001-04 | Fibre Rope Inspection and Retirement
Criteria |
| ISO 1968 | Fibre ropes and cordage - Vocabulary |
| ISO 18692 | Fibre ropes for offshore station-keeping - Polyester. |
| OCIMF | Guidelines for Purchasing and Testing
of SPM Hawsers. |
Ch.1 Sec.1
C. Definitions
Ch.1 Sec.1
C 100 Verbal forms
Ch.1 Sec.1 C
101 Shall: Indicates a
mandatory requirement to be followed for fulfilment or compliance
with the present standard. Deviations are not permitted unless formally
and rigorously justified, and accepted by all parties.
Ch.1 Sec.1 C
102 Should: Indicates a
recommendation that a certain course of action is preferred or particularly
suitable. Alternative courses of action are allowable under the
standard when agreed between contracting parties, but shall be justified,
documented and approved by DNV.
Ch.1 Sec.1 C
103 May: Indicates permission,
or an opinion, which is permitted as a part of conformance with
the standard.
Ch.1 Sec.1 C
104 Can: Indicates a conditional
possibility.Ch.1 Sec.1
C 200 Terms
Ch.1 Sec.1 C
201 AVS: Average strength,
as determined by the average of a minimum of five break tests.
Ch.1 Sec.1 C
202 Aramid: para-aramid.
Ch.1 Sec.1 C
203 Change-in-length performance: The
stretch and cyclic stiffness of the fibre rope as function of loading sequence
and time.
Ch.1 Sec.1 C
204 Core: The term core
usually refers to the assembly of load-bearing, parallel subropes.
Ch.1 Sec.1 C
205 Design Range: The difference
between the highest occurring tension and the lowest occurring tension
in the mooring line.
Ch.1 Sec.1 C
206 FEM: Finite Element
Modelling.
Ch.1 Sec.1 C
207 Fibre rope: The full-size
rope without splices and eyes, constituted by all subropes and sheathing.
Ch.1 Sec.1 C
208 Fibre-rope assembly: Fibre-rope
segment with designated termination hardware.
Ch.1 Sec.1 C
209 Fibre-rope segment: Finished
fibre rope with spliced terminations, and splice-area protection.
Ch.1 Sec.1 C
210 Full rope: Refers to
the bundle of subropes with sheathing, either as Fibre Rope, Fibre-Rope
Segment or Fibre-Rope Assembly.
Ch.1 Sec.1 C
211 Guidance Note: Advice
which is not mandatory under this standard, but with which DNV,
in light of general experience, advises compliance. The client may
decide whether to apply the note or not. Guidance Notes can also
contain statements provided for additional information to the reader.
Ch.1 Sec.1 C
212 HMPE: High-Modulus
PolyEthylene.
Ch.1 Sec.1 C
213 ITP: Inspection and
test plan, which is a plan for the various steps in making the fibre-rope
assemblies, describing the involvement of QA department and external
surveyor.
Ch.1 Sec.1 C
214 In-service condition assessment
scheme: Inspection plan and activities performed regularly
during the service life in order to assess the condition of the
mooring system.
Ch.1 Sec.1 C
215 Insert: A short fibre-rope
segment that is intended for retrieval to assess the condition of
the mooring system during the service life. It can also be a cut
off from a long line which is re spliced and returned to service upon
retrieval of the test length.
Ch.1 Sec.1 C
216 Linear Density: A measure
of rope mass per unit length. Linear density is used as a measure
of the load-carrying cross section of the rope and should be tested
under specific conditions according to a standard such as CI 1500.
Ch.1 Sec.1 C
217 Long-term mooring system: Mooring
system that is installed for a design life of five years or more.
Ch.1 Sec.1 C
218 MBS: The Minimum Breaking
Strength is the required strength of the delivery, i.e. not a property
as such of the fibre-rope assembly. The lowest result obtained in
the break testing shall meet or exceed the MBS.
Ch.1 Sec.1 C
219 Mobile mooring system: Mooring
system that is installed for a design life of less than five years,
or a mooring system utilised by mobile units such as Mobile Offshore
Drilling Units; characterised by intermittent use of the mooring
lines that allows hands-on inspection at limited time intervals.
Ch.1 Sec.1 C
220 Mooring line: The entire
line that transfers tension between the floating unit and the anchor.
Ch.1 Sec.1 C
221 ROV: Remotely Operated
Vehicle.
Ch.1 Sec.1 C
222 S: The letter 'S' is
used to denote the left-hand orientation of a subrope strand. The
same definition is also used for yarns.
Ch.1 Sec.1 C
223 Sheathing: Protective
jacket and soil barrier.
Ch.1 Sec.1 C
224 SSA: Safe Service Assessment
is a method for assessing residual life based on design curve for
Time To Rupture. This is a new method subject to confidentiality
at the time of this standard.
Ch.1 Sec.1 C
225 Termination hardware: The
steel component inserted in the rope eye to transfer the line loads
from the fibre-rope segment to the rest of the mooring line. The
spool thimble is most commonly used.
Ch.1 Sec.1 C
226 Test unit: For manufacturing
of termination hardware, a test unit is defined as items from the
same heat of steel and same heat-treatment batch.
Ch.1 Sec.1 C
227 User: The company that
buys the fibre-rope assemblies from the manufacturer.
Ch.1 Sec.1 C
228 Z: The letter 'Z' is
used to denote the right-hand orientation of a subrope strand. The
same definition is also used for yarns.
Ch.1 Sec.1 C
229 Cyclic Endurance: The
ability to withstand prolonged cyclic loading without deterioration
of strength or other performance criteria.
Ch.1 Sec.1 C
230 Qualification: Confirmation
by examination and provision of evidence that the new technology
meets the specified requirements for the intended use. Hence, qualification
is a documented set of activities to prove that the technology is
fit for purpose.
Ch.1 Sec.1 C
231 Offshore grade of yarn: Yarns
that through adequate processing and treatment is deemed fit for
service in offshore mooring applications and where this is documented
by testing.
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