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The electronic pdf versions of the documents found through http://www.dnv.com/ are the officially binding versions. Copyright Det Norske Veritas.
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DNV-OS-E303 Offshore Mooring Fibre Ropes |
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| Ch.2: Technical provisions |
Ch.2
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Reference is made to DNV-OSS-101 and DNV-OSS-102 with regard
to in-service inspection of mooring lines for mobile and long-term
moorings.
For materials exhibiting stress rupture, tension measurements
will provide vital input for assessment of progression of damage.
(Applicable to polyester, para-aramid, polyamide and LCAP.)
For materials exhibiting creep failure, length measurements
will provide vital input for assessment of progression of damage.
(Applicable to HMPE.)
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Test material is taken by cutting off a short length and re-terminating
the rope segment.
Ch.2
| — | requirements to length of fibre-rope assemblies as-new and during the service life |
| — | in-service condition control scheme |
| — | service requirements and operational boundaries for the finalised mooring system |
| — | design life |
| — | highest and lowest occurring sea-water temperature |
| — | minimum bending diameter during transport and installation |
| — | torque and rotation characteristics |
| — | evaluation of sea-bed particles (e.g. sand and mud) experienced by the fibre-rope assembly during installation. |
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Service requirements and operational boundaries comprise installation
sequence, pre-tension, loading scenario including the maximal occurring
cyclic loading.
If any of the components in the mooring line are not torque
neutral, then an analysis of the torque / rotation interaction shall
be submitted. Documentation in the form of analyses and/or
test results should be submitted to demonstrate no adverse affects.
Mixing torque-generating steel-wire rope with torque neutral
fibre rope is mainly a concern for the cyclic endurance of the steel-wire
rope. As a general rule, mooring chain should not be subjected to
excessive torque in operation. Swivels should be used with caution.
| — | rope design description |
| — | testing specification |
| — | procedure for handling and installation |
| — | specification of material for the fibre rope sheathing, consisting of filter and jacket |
| — | specification of load bearing yarns |
| — | documentation of the materials for spliced-eye protection |
| — | documentation of the termination hardware. |
| — | manufacturer and manufacturing plant |
| — | designation |
| — | sheathing weight/thickness |
| — | permeability to water |
| — | permeability to sunlight |
| — | UV resistance |
| — | seawater hydrolysis resistance |
| — | resistance to chemicals. |
Ch.2
| — | manufacturer and manufacturing plant |
| — | yarn designation |
| — | linear density |
| — | boundary conditions for cyclic loading range |
| — | yarn breaking strength |
| — | wet yarn-on-yarn abrasive performance |
| — | marine finish designation |
| — | seawater hydrolysis resistance |
| — | stress-rupture properties for polyester, polyamide, LCAP and aramid yarn materials |
| — | creep failure resistance for HMPE yarn materials. |
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Reference is made to DNV-OS-E301 for notes on stress rupture
and creep failure.
The design range stated in the yarn certificate shall be verified
to be within the intended operations of the mooring system.
It is a requirement of ISO 18692 that the load-bearing rope
should be manufactured from yarns of average tenacity not less than
0.78 N/tex.
| — | the rope jacket |
| — | the filter, if applicable. |
| — | manufacturer and manufacturing plant |
| — | designation of yarns and fabrics |
| — | sheathing weight and thickness |
| — | permeability to water |
| — | permeability to sunlight |
| — | seawater hydrolysis resistance. |
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
If the fibre rope segment is intended to be opened for later
inspection, such as a service insert or test specimen, then the
segment should be equipped with sufficient cloth beneath the PU
coating such that the splice area can be opened as a loose carcass.
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
A test unit is defined as items from the same heat of steel
and same heat-treatment batch.
Ch.2
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
If the lowest result fails to meet the MBS requirement then
it should be evaluated if the actual strength is adequate for the
service. It should be observed that if the difference is not too
large, it may be beneficial not to increase the linear density since
this can have other, undesirable effects such as increased fatigue
exposure of steel components.
If the lowest result should be an out-layer compared to the
other results then it can be disregarded provided the manufacturer
produces a technical report with detailed analysis and explanation
of the cause of the low result, and demonstrates the measures to
be implemented to prevent the same error to occur during production.
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Flange bending should be included in the load case.
If fibre-rope assemblies are break tested without termination
hardware from the actual delivery, then the interface to the fibre-rope
eye shall be identical to that of the termination hardware.
The cyclic endurance testing should be performed using thimbles
from the actual delivery.
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
On certain conditions a larger rope can cover the cyclic-endurance
test requirement of a smaller rope. It is recommended to perform
testing on a fibre-rope assembly that covers more than just one
delivery of the same yarn material and type of subrope.
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
It is not possible to cover the effects of interaction in
the rope eye if a scaled specimen is used, even if subropes are not
scaled.
Ch.2
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
The following sampling rates may be taken as advice:Break test at loads above 75% MBS: 0.5 seconds between points. Dynamic stiffness: 20 - 30 points per cycle. Fast changes in load level: 2 seconds between points. Initial parts of static measurements: 1 - 10 seconds between points. Final parts of static measurements: 1 minute - 1 hour between points.
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
For change-in-length measurements on the full fibre rope,
the extensometer should be attached on the outer jacket with fixations
that are gripping or squeezing the whole cross section. However,
measurement on single subrope is the preferred method, and the accuracy
when measuring on fibre rope shall therefore be justified. It must
be ensured that the jacket follow the changes in length of the load-bearing
subrope bundle.
The gauge length for stretch measurements needs to be commensurate
with the accuracy of the length-measurement device. Advice is provided
in CI 1500.
The following applies to testing carried out during manufacturing
of the yarns for the actual delivery.
Ch.2 Sec.5 B
101 In order that test results obtained are reproducible and give
reliable information about the material, the sampling must be true
and representative. The sampling procedure should be designed to
take account of the known sources of variability such as the variation
between spindles, the variation along the length of the bobbin,
etc. Sampling may be based on ASTM D2258.
Ch.2 Sec.5 B
102 The manufacturer should carry out testing according to Table
B1 as a minimum and keep records of all testing.
Ch.2 Sec.5 B
103 The test methods, number and selection of parallels, acceptance
criteria, minimum frequency of control for each parameter for quality
control are given in Table B1.
Ch.2 Sec.5 B
| Table B1 Requirements to tests at yarn manufacturer for the delivery | ||||||||
| Control on | Test standard 1) | Acceptance Criteria | Minimum level of verification | Frequency of control | ||||
| Visual | Specified by the manufacturer | Specified by the manufacturer | Results documented in production log | Continuous during production | ||||
| Chemical composition | Specified by the manufacturer | Specified by the manufacturer | Results documented in production log | Specified by the manufacturer | ||||
| Linear density | ASTM D885M | Mean ± 2 sdev within manuf. Nominal value ± 5% | Results documented in production log | Each day | ||||
| Moisture content | ISO 3344 | Manufacturer's specified value | Results documented in production log | Each day | ||||
| Marine finish | Specified by the manufacturer | Manufacturer's specified value | Results documented in production log | Each day | ||||
| Glass-rubber transition | Specified by the manufacturer | N/A | Results documented in production log | Specified by the manufacturer | ||||
| Force vs. stretch | ASTM D885M | Manufacturer's specified value, not more than ± 5% of nominal value | Results documented in production log | Each day | ||||
| Yarn-on-yarn abrasion | CI 1503 | Specified by the manufacturer | Results documented in production log | According to test standard | ||||
| Time-to-rupture 2) | Specified by the manufacturer | Specified by the manufacturer | Results documented in production log | Specified by the manufacturer | ||||
| Creep testing 2) | Specified by the manufacturer | Specified by the manufacture | Results documented in production log | Specified by the manufacturer | ||||
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Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
TTR testing is
applicable to polyester, polyamide and aramid. Creep testing is
applicable to HMPE.
Ch.2 Sec.5 C
| Table C1 Requirements to test specimens for mobile mooring | |
| Type of test | Number of test specimens |
| Breaking strength, mobile mooring | 5 subropes & 3 fibre-rope assemblies |
| Change-in-length performance | Minimum 3 subropes |
| Splice integrity | 3 subropes |
| Torque and rotation | 1 fibre rope, if applicable |
| Soil ingress resistance | 1 fibre rope |
| Linear density | 2 subropes |
| TTR testing. | To be determined on case-by-case basis, if applicable |
| Creep testing. | To be determined on case-by-case basis, if applicable |
| Additional requirements to test specimens for long-term mooring | |
| Type of test | Number of test specimens |
| Breaking strength | 2 fibre-rope -assemblies |
| Cyclic endurance test | 1 fibre-rope segment with termination hardware from the actual delivery |
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
TTR testing is applicable to polyester and aramid ropes. Creep
testing is applicable to HMPE ropes.
| — | loading 6 000 cycles between 5% and 50% MBS |
| — | loading 14 000 cycles between 5% and 44.1% MBS. |
The cycling speed of the test machine may be as fast as possible;
however care should be taken with respect to hysteresis heating.
The specimen should be irrigated to mitigate heating during the
test.
Ch.2 Sec.5 D
503 Examination of specimen:
| — | dimensions and external condition of splice and eye |
| — | condition of specimen interior |
| — | perform break testing of 5 selected subropes |
| — | tests as required by the pre-qualification testing for the insert-free in-service condition assessment scheme, if applicable. |
Guidance note: ---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
For ropes containing less than 10 subropes the examination
and testing program will have to be established on a case-by-case
basis.
| — | force vs. pin-pin stretch curve of first 10 cycles, cycle 20, 50, 100, 200, 500, 1000, etc. and last 5 cycles of part 1 |
| — | force vs. pin-pin stretch curve of first 10 cycles, cycle 20, 50, 100, 200, 500, 1000, etc. and last 5 cycles of part 2 |
| — | photographic documentation from examinations |
| — | break test reporting requirements for the subropes |
| — | documentation based on the force vs. stretch plots for pin-pin, that the splice is self locking |
| — | other reporting requirements, as applicable. |
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