Section
11 Anchor winches and windlasses
11.1 General
11.1.1 This Section applies to winches and windlasses designed actively to
control anchor line tensions in-service, or to release anchor lines in an
emergency.
11.1.2 Special consideration will be given to requirements for winches and
windlasses for passive mooring systems, or permanent mooring systems.
11.1.3 Machinery items are to be constructed to recognised design Codes and
Standards. The relevant requirements of Pt 5 Main and Auxiliary Machinerymay be used as guidance for small and simple equipment,
but, special analysis techniques such as finite element methods (or equivalent) are
considered to be more appropriate.
11.1.5 Along this Section the maximum break load refers to the maximum break
strength (as new and based on expected maximum break strength plus two standard
deviations) of the main component (steel wire rope, chain or fibre rope) directly
acting on or closest in the load path to the structure under consideration and is
generally not to be taken lower than 110% of the nominal minimum break strength of
the component.
11.2 Materials
11.2.1 Materials are to comply with the Rules for Materials. Alternatively,
materials which comply with national or proprietary specifications may be accepted,
provided that these specifications give reasonable equivalence to the requirements
of the Rules for Materials, or are approved for a specific application. Generally,
survey and certification are to be carried out in accordance with the requirements
of the Rules for Materials.
11.2.2 For the selection of material grades, individual components of anchor
winches and windlasses are to be categorised as primary or secondary.
11.2.3 Components where the failure would result in the loss of a primary
function of the winch or windlass are considered to be ‘primary components’, see
also
Pt 3, Ch 10, 11.2 Materials 11.2.5.
11.2.4 All other components where the failure would not result in the loss of a
primary function of the winch or windlass are to be categorised as ‘secondary
components’.
11.2.5 Primary components which are designed with an adequate degree of
redundancy in their operation will be specially considered and may be categorised as
secondary.
11.2.6 Material grades for all components are in general related to the
thickness of the material, the structural category and the minimum design air
temperature and are to be selected to provide adequate notch toughness.
11.2.7 Material grades for welded plate components are in general to comply
with Pt 4, Ch 2, 4 Steel grades For thicker plates and/or lower
design temperature the steel grades will be specially considered.
11.2.8 Material grades for components which are not subject to welding will be
specially considered.
11.2.9 Castings and forgings are to comply with Ch 4 Steel Castings and Ch 5 Steel Forgings of the Rules for Materials respectively and the requirements
for notch toughness in relation to the design air temperature will be specially
considered.
11.2.10 Non-ductile materials are not to be used for torque transmitting items or
for those elements subject to tensile/bending stresses.
11.2.12 The use of grey iron castings will be subject to special consideration.
Where approved, they are to comply with the requirements of Ch 7, 2 Grey iron castingsof the Rules for Materials. This material is not to be
used for gear components.
11.2.13 Brake lining materials are to be compatible with operating environmental
conditions.
11.3 Brakes
11.3.1 Each anchor winch or windlass is required to have one primary braking
system and one secondary braking system. The two systems are to operate
independently. The requirements of Pt 3, Ch 10, 11.5 Winch/windlass performance are to be complied with.
11.3.2 The braking action of the motor unit may be used for secondary braking
purposes where the design is suitable.
11.4 Stoppers
11.4.1 If the winch motor is to be used as a secondary brake then a stopper is
to be provided to take the anchor line load during maintenance of the primary
brake.
11.4.2 The stopper may be one of two different types: a pawl stopper fitted at
the cable lifter/drum shaft, or a stopper acting directly on the anchor line.
11.4.3 Where the stopper acts directly on the cable, its design is to be such
that the cable will not be damaged by the stopper at a load equivalent to the
nominal minimum breaking strength of the cable (as new).
11.5 Winch/windlass performance
11.5.1 The primary brake is required to hold a static load equal to the maximum
break strength of the anchor line (at the intended outer working layer of wire rope
on storage drum winches). The static load capacity of the primary brake can be
reduced to 80 per cent of the nominal minimum break load of the mooring line (as
new) when a stopper, capable of holding maximum breaking strength of the line, is
fitted.
11.5.2 The secondary brake is required to hold a static load equal to 50 per
cent of the nominal minimum breaking strength of the anchor line (as new).
11.5.3 For passive or permanent positional mooring systems the primary brake is
required to hold a static load equal to 150 per cent of the winch/windlass capacity,
when isolated from operational/survival mooring line loads using a stopper. A
secondary brake is not required in this case.
11.5.4 The anchor winch or windlass is to have adequate dynamic braking
capability. The two brake systems in joint operation are to be capable of fully
controlling without overheating, the anchor lines during:
- all anchor handling operations;
- adjustment of anchor line tensions. (This is particularly
relevant where the mooring system has been designed and sized on the basis
of active adjustment of anchor lines in extreme conditions, to minimise line
tensions.)
11.5.6 Means are to be provided to enable the anchor lines to be released from
the unit after loss of main power.
11.5.7 On Offshore Mobile Units, the pulling force of the winches or windlasses
is to be sufficient to carry out anchor pre-loading on location, to the necessary
level. A minimum low-speed pull equal to 40 per cent of the anchor line nominal
minimum breaking strength is recommended.
11.6 Strength
11.6.1 Design load cases for the winch or windlass assembly and the stopper,
when fitted, are given in Table 10.11.1 Design load cases . The associated maximum
allowable stresses are to be based on the factors of safety given in Table 10.11.2 Load case factors of
safety .
Table 10.11.1 Design load cases
| Load
case
|
Condition
|
Anchor line load
|
| 1
|
Winch braked
|
Maximum break strength, see Note
|
| 2
|
Stopper engaged
|
Maximum break strength
|
| 3
|
Winch pulling
|
40% of nominal minimum break load (as new)
or specified duty pull if greater
|
| Note:
|
| Where a
stopper is fitted, the anchor line load in Case 1 may be taken as
the brake slipping load, but is not to be less than 80% of the
nominal minimum break strength of the anchor line (in as new
conditions).
|
11.7 Testing
11.7.1 Tests are to be carried out at the manufacturer’s works in the presence
of the Surveyor, on at least one of the winches or windlasses out of the total
outfit for the unit. The tests to be carried out are given in Table 10.11.3 Winch/windlass tests . Alternatively, where a
prototype winch has been suitably tested, consideration will be given to the
acceptance of these results.
11.7.2 The residual braking capability is to be verified in accordance with
Pt 3, Ch 10, 11.5 Winch/windlass performance 11.5.4.
Table 10.11.2 Load case factors of
safety
| Stress
|
Load case
|
| 1 and 2
|
3
|
| Factor of safety
|
| Shear
|
1,89
|
2,5
|
| Tension, compression,
bending
|
1,25
|
1,67
|
| Combined
|
1,11
|
1,43
|
| NOTES
|
| 1. Factors of safety relate to tensile yield stress.
|
2. Combined
stress = 
Where σX and σY are the combined axial and bending
stresses in the X and Y directions respectively and τ is the
combined shear stress due to torsion and/or bending in the X–Y
plane.
|
Table 10.11.3 Winch/windlass tests
| Test
|
Test load
|
| Static brake – Primary
|
Maximum break strength
(or 80% of nominal minimum break strength of mooring
line (as new) where stopper is fitted,see 11.5.1)
|
| Static brake – Secondary
|
50% anchor line nominal minimum break
strength of mooring line (as new)
|
| Stopper (where fitted)
|
Maximum break strength
|
| Motor stall test
|
Specified stall load
|
11.7.3 Each winch or windlass is to be tested on board the vessel in the
presence of the Surveyor, to demonstrate that all main aspects including dynamic
brakes function satisfactorily.
A static overload test to 125% of the winch´s Nominal Load (defined as
the chain or rope tension that the winch is able to maintain continuously when
hauling at nominal speed, measured either at the cable-lifter exit, or at the rope
exit of the first layer in the case of a wire-drum shall be considered in addition
to functional testing carried out on board.. Further guidance on testing to be
carried out can be gained from BS 7464:1991/ISO 9089.
The proposed test programme is to be submitted.
11.7.4 Mooring winches and windlasses are to be regularly tested during service
as part of the inspection maintenance and repair plan. Note that winches used in
support of inspection, maintenance and repair plan (e.g. to shift chain links in the
stopper during inspections) should be maintained as well as winches used in support
of mooring line failure or loss of station keeping capability. The failure response
procedure is to be kept in good working condition and regularly tested.
11.8 Type approval
11.8.1 Winches or windlasses may be Type Approved in accordance with LR’s
Type Approval Scheme. Where this Type Approval is obtained, the
requirements of Pt 3, Ch 10, 11.7 Testing may not be applicable.
|