JAPAN P& I CLUBVol.36 October 2015

P&I Loss Prevention Bulletin
The Japan Ship Owners Mutual Protection & Indemnity Association Loss Prevention and Ship Inspection Department

CRANES, THEIR OPERATION AND
REASONS FOR FAILURES

INDEXIntroduction …………………………………………… 2

Normal operation of cranes ……………………… 11

General guidance on inspections and maintenance … 4

Incidents involving damage to a crane ………… 14

Wire ropes and their ancillary equipment ……… 5

Grabs and their use ……………………………… 15

Crane structures …………………………………… 9

Grab capacity and safe working load ………… 17

Crane machinery ………………………………… 10

Safety ……………………………………………… 19

Introduction
Cargo handling cranes, commonly pedestal mounted jib cranes, are fitted on board most handy-size bulk carriers,
most general cargo ships and some other smaller or larger bulk carriers. These cranes appear to be fairly robust units
which will continue to work when only a minimum of maintenance is carried out, but, in fact, they are highly complex
pieces of machinery which incorporate numerous components manufactured to very fine tolerances, all of which must
function correctly throughout a working period for the crane, as a unit, to be operated as the manufacturers intended.
The cranes should be properly maintained, and should be inspected at specified intervals to ensure that they operatecorrectly and safely. Additionally, all other equipment used in association with a crane should, likewise, be properly
maintained and should be inspected as appropriate. If the equipment is not in the appropriate good condition, failures
are likely to occur during cargo operations.

Centre of rotation
Slewing
Hoisting

Lowering
Luﬃng
(up)

Jib

Rotating
turretLuﬃng(down)
Slew ringconnection

Operatorsʼ
cab

Fixed
pedestal

Radius (hook or load)

Fig.1 The general movement of a pedestal crane
Each crane will comprise components, as follows:

Wire ropes

Structures

Machinery

Usually a hoist wire and a
luf fing wire (although onsome cranes the luffing of
the jib might be by meanso f one or t wo hydr aulicc y l i n d e r s) a n d v a r i o u sancillary equipment.

Including a p e de s t al, ahousing and a jib, w it has s o cia t e d m o u n t in g s ,bearings and foundations
for winches, motors,
pumps, etc.

Including electrical control
equipment and systems,
various winches, motors,
pumps, etc., limit switches,
cut-out switches and otherpieces of equipment.

Additionally, some ships are ﬁtted with bulk handling grabs for use with the shipsʼ cranes.

−2−

JAPAN P& I CLUB

Photo 1 General view of two cranes

Any failure of any part of the crane will lead to delays in the cargo operations, and any such delay is likely to haveother consequences. Additionally, the renewal of parts or the carrying out of repairs might be necessary, which islikely to be expensive and cause further delays.
The failure of a cargo handling crane is likely to involve one or more of the following:

1

Failure of a hoist or luﬃng wire
The result of poor maintenance of the wire leading to weakening of the wire over time or inappropriate operation of the crane and incorrect use of the wire leading to damage being sustainedby the wire.

２

Failure of the structures
The result of poor maintenance of the various elements leading to weakening of the structures
or incorrect use of the crane leading to damage being sustained by the structures.

３

Failure of the machinery
The result of poor maintenance leading to the failure or incorrect use of the crane leading tooverloading of the piece of machinery.

Some general guidance on good practice for the inspection and maintenance of the various parts of ships' cranes isgiven in the article, together with guidance on the operation of cranes and the maintenance and use of grabs.

−3−

General guidance on inspections andmaintenance
There should be on board every ship fitted with cranes a manual produced by the manufacturers of the cranes giving
recommendations and guidance with regard to the operation of the cranes and details of inspections and maintenancewhich should be carried out, as a minimum. There should also be a planned maintenance regime which should include
the recommendations set out in the manufacturers' manual. Additionally, there should be a regime for the inspectionof each crane and its machinery and structures within the Safety Management System procedures. All the required
maintenance, the appropriate inspections, and the testing of each crane and all its various parts, should be carried out
at appropriate intervals. Records should be kept of all maintenance, all inspections, and the renewal of any parts, andthose records should be held for future reference. More detailed comments, with regard to the various parts of a crane,
are dealt with below.

More detailed comments with regard to the various parts of a crane.
1

Cranes, and other lifting appliances and theirloose gear, are required to be thoroughly
inspected annually, with a further thoroughinspection and a proof load test every five
years. Those inspections and testing are
in accordance with the ship's Flag State requirements, although it is common procedure
for the classification society surveyor tocarry out the required inspections and tests.
Details of the surveys should be recorded in
the ship's Register of Lifting Appliances andCargo Handling Gear. Also, there should beon board an appropriate test certiﬁcate for all

wire ropes on board;t ha t is, f o r all o f
those in use and forall spare wire ropes.
The cer tificatesshould give the dateof manufacture, thema t e r ial s t r e ng t h,
the construction of the rope and the breaking
load test of a sample. There should be an
inventor y of all wire ropes on board andrecords of the dates of renewal of the wires
in use on all cranes.

Wire ropes, motors, electrical control systems
and other pieces of machinery and equipment
wear out or might be damaged during theoperation of a crane. It is therefore necessary
for a number of spare parts to be maintainedon board at all times. The trading pattern of
the ship will, to an extent, dictate what type
and what number of spares will be required.
If the ship is trading in very hot or very cold
areas, or if the cranes are frequently used
for cargo handling, the hoist wires and winch
motors might not last as long as if the ship

is trading in less harsh environments. For
example, even ignoring misuse, the hoist
wire might be heavily worn with broken wires
after only two years in use if self-loading
and self-discharge is a routine procedure,
whereas the hoist wire of a crane on a ship
which is trading between terminals with onshore loading and off-loading facilities might
require renewal
at only five year
intervals.

2

Maintenance and inspections of the cranes, their wire ropes and their various pieces of machinery and equipment are
essential to ensure that the operation of the crane is reliable and that there is a minimum of wear and damage.
−4−

JAPAN P& I CLUB

Wire ropes and their ancillary equipment
Steel wire rope is constructed in a number of different arrangements, each arrangement of the outer strands and thecore having different characteristics. Those characteristics will provide resistance to one or more of the following:1

Rotation２

The torque or turning motion generated whena load is applied or is removed.

３

Deterioration as a result of working, bending
and straightening around sheaves or a barrel
when it is under load.

Abrasive wear

４

Which takes place between a wire rope and thesheaves it passes over, and between a rope andthe barrel, or adjacent ropes on the barrel, as itis paid out or hauled in.

５

Fatigue

Crushing
Crushing of a wire rope will occur when there
are multi layers of a rope on the barrel.

Corrosion
A galvanised coating of the wires is normal for
wires fitted to ships' cranes to minimise theeﬀects of corrosion due to contact with sea
water.

Fig.2

Compacted outer strands compared with strands of a normal wire rope(by courtesy of Certex (UK)).

−5−

Wire ropes fitted to deck cranes should be designed for the purpose and should incorporate resistance to rotation,
fatigue, corrosion and abrasive wear. Resistance to abrasive wear is achieved by the construction incorporatingcompacted outer strands. That is, the strands are made up with wires of a particular cross section, not circular, so as
to produce a smooth outer surface to the strands which might look as if the wire is worn overall. There should be on
board an appropriate test certificate for all wire ropes and there should be an inventory showing the date of fitting of
all wires in use on all the cranes and the status of all spare ropes. The master and the chief officer, and appropriatecrew members, should have full knowledge of the status of crane wires and of the construction of wires fitted tothe deck cranes. The wire ropes in use should be of the correct diameter and construction, as specified by the cranemanufacturer, because only the correct wires will run smoothly and correctly over sheaves and on the winch barrels.
Wire ropes of incorrect diameter and/or construction will deteriorate rapidly when in use and may cause damage toother parts of the crane.
The period of safe use of a wire rope will depend to alarge extent upon the manner in which it is maintained
and cared for while it is in use. If the wire is regularly
inspected and lubricated, and if the other parts of thecrane are properly maintained, the wire will suffer lessdamage than if proper maintenance is not carried out.

Core of steel or ﬁbre

Wire

Corewire in the strandof steel or ﬁbre

The planned maintenance regime is likely to requirethat inspections of the wire ropes are carried out at
set intervals and that the ropes are lubricated with anappropriate grease at the same or at a different interval.
During routine inspections and maintenance of the wire
ropes they should be inspected over their full lengthand their fittings should also be inspected. Inspections
and maintenance should be carried out in respect of thefollowing:

StrandSteel wire rope

Fig.3 Wire construction (by courtesy of Certex (UK))

1

The wire rope over its
full length

Inspections should be carried out toidentify defects (as set out below)
and the rope should be lubricatedoverall with particular attention toparts of the rope in way of sheaves
when the crane is stowed for sea,end ferrules and end terminations.

２

Swivels

These should be in soundcondition without defects
and should turn easily byhand, if not they should bedismantled, cleaned, re-built
and greased.

−6−３Ancillary equipment

Including hooks, cargo blocks,
shackles and other loose gear
- should be in sound condition
without defects and all moving
parts should be free and appropriately greased.

JAPAN P& I CLUBIf any defects or damages are found, repairs should be carried out if appropriate, or the item should be removed fromthe crane and a new item should be fitted.
Wire ropes should be examined for defects and if those defects are excessive advice should be obtained and/or therope should be discarded, as follows:1

Number of broken
wires

When broken wires are found,the number of broken wires
within a part of the wire rope,for example, within a length
equal to six diameters, should
be assessed. If an excessive
number of wires within that
length are broken, the wire rope
should be discarded (see ISO
4309 and below).

４

External andinternal corrosion

If there is excessive corrosion,
either internally or externally,
the strength of the wire will
be adversely af fected and it
may be appropriate to discard
the wire rope; specialist advice
should be sought.

２

Fractured strands

If a complete strand is fractured, the wire rope should
be discarded.

５

Decrease inelasticity

Although this is dif ficult to
defect by ship's staf f, if thewire rope is found to have a
reduced diameter or if there iselongation of the lay or the wirerope is found to be more stiff
than expected, specialist advice
should be sought.

３

External andinternal wear

I f t h e r e is e x c e s si v e w e a r,either internally or externally,
the strength of the wire will be
adversely aﬀected and it may beappropriate to discard the wirerope; specialist advice should besought６

Kinks and othermechanical damages

If any kinks, distortions or otherdamages are found, their severity should be assessed and it
might be appropriate to discard
the wire rope; specialist advice
should be sought.

Fig.4 Inspections of rope for internal and external damage (by courtesy of Certex (UK))−7−

The international standard ISO 4309, "Cranes - Wire ropes - Care, maintenance, installation, examination anddiscard", sets out a comprehensive list, with photographs, of defects that affect wire ropes. Guidance with regard to
how inspections should be carried out is shown, and what should be looked for is given, for example how to carry out
an internal examination of a wire using specialised tools. Also, the discard criteria for wire ropes of different types are
given, for example, the number of broken wires in a specified length of the wire rope which would warrant discard.
Following completion of an inspection of a crane wire, the wire should be lubricated by the application of an appropriate grease or dressing. It might be necessary, if required by the age of the previous dressing or by the procedures ofthe lubricant manufacturer, for the wire to be cleaned to remove any old and de-natured dressing, in which case an appropriate cleaning product should be used. The lubricant should cover all parts of the rope and it might be necessary
to work the dressing into the core of the rope in order to ensure the proper working of the lubricant.
Records of all inspections, maintenance and renewals of crane wires should be kept for future reference.

−8−

JAPAN P& I CLUB

Crane structures
The structures of a crane include: (a) the pedestal upon which the crane is mounted; (b) the housing of the craneincluding all strength structures within the housing and all sheaves, and their mountings, at the top and at any otherlocation on the crane; (c) the slewing ring at the base of the housing and its associated mechanisms; and (d) the crane
jib including the heel bearings, the strength structures of the jib itself and the sheaves, and their mountings, at the jib
head and at any other location. Additionally, the foundation structures of the winches, motors, pumps, etc., also form
part of the structures of a crane.
Routine maintenance of the various parts of the structures, and of the fittings and support structures, is essential for thecontinuing correct operation of the crane. In accordance with the planned maintenance regime, inspections and testingof the various parts should be carried out and the repair and any renewal of parts should be undertaken as follows:

1

２

３

The main structures of the crane should be inspected to establish if any damage has been sustainedor if there are any defects in the form of fractures or corrosion of the steelwork. Repairs and/or
renewals should be carried out as appropriate.

All sheaves, bearings and other moving parts should be inspected to determine whether or not any
wear or deformation of the parts is present. If parts are defective they should be removed and newspare parts should be ﬁtted and then tested for correct operation. Those moving parts should be
lubricated using the appropriate grease in the correct manner.

All foundation structures and mountings should be inspected to determine whether or not any defects
or damages are present and, if any such defects/damages are present, appropriate repairs should be
carried out.

Records of all inspections, maintenance, repairs and renewals should be kept for future reference.

Photo 2 Maintenance on-going at the top of a crane−9−Crane machinery
The machinery of a crane includes all electrical control equipment and systems, all motors, hydraulic oil pumps, filtersand coolers, and winches, together with winch brakes and control gear, all limit switches, cut-out switches and otherpieces of equipment.
Routine maintenance of these various pieces of machinery is essential for their continuing correct operation. In accordance with the planned maintenance regime, inspections and testing of the various parts should be carried out, withrenewal of items, etc., as necessary, as follows:1

２

３

Items such as filters should be cleaned/renewed
at designated intervals and when indicated byincreasing diﬀerential pressure.
Gearbox oil and any hydraulic oil should be changed
and kept to the required level in accordance withthe manufacturers' specification. Additionally,
when appropriate, the oil should be changed
subject to shore-based analysis of samples, toinclude particle count to assess the internal wearof the machinery. This sampling/testing should bedone at about three-monthly intervals, subject tothe on-going use of the cranes.
All limit switches and cut-out switches should be
inspected and tested at appropriate intervals toensure their correct operation and any defective
parts should be renewed.

4５Electrical control equipment and systems should be inspected and tested
at appropriate inter vals and any
defective parts should be renewed.

All motors, pumps and winches, andtheir brake mechanisms, should be
inspected and tested at appropriate
intervals and renewal of any complete
units or parts of those units should be
carried out as required when defects
are found. Defects and developing
problems might be identified by way
of shore-based analysis of samples ofoil, to include particle count, to assess
the internal wear of the machinery.

Records of all inspections, maintenance, repairs and renewals should be kept for future reference.

Photo 3

Part of the machinery and hydraulic systems of a crane− 10 −JAPAN P& I CLUBNormal operation of cranes
When ships' cranes are used for cargo operations, it is likely that they will be used over an extended period and alsothat stevedores' crane drivers will operate the cranes; it is sometimes the case that members of the crew will operate
the cranes during such operations. It is essential that the cranes are in good order and operating satisfactorily at the
beginning of any cargo operations and that the crane drivers are experienced in order that incidents are avoided. If
any incidents do occur, an investigation should be carried out and any appropriate inspections should be completed as
discussed in a separate section below. The general procedures for the normal operation of cranes are set out below.
As discussed above, there should be on board a planned maintenance regime for the inspection and care of the cranes;
the requirements of that regime should be strictly followed. If all the required inspections and necessary maintenanceof the cranes, that is of their machinery, their structures, and their wire ropes and other equipment, are completed, thecranes will be ready for use during cargo operations, or for other tasks, at any time. However, during an extended
period of cargo operations the cranes, and their various components, will be subjected to loads and stresses whichmight lead to damages being sustained by some of the parts even though all the required inspections, maintenance,
renewals, etc. have been carried out. For this reason, inspections of the cranes should be carried out before a period ofcargo operations, on-going inspections should be carried out during those operations and a thorough examination ofeach crane should be carried out after the cargo work has been finished.

Before cargo operations
Before arrival at a cargo operations berth, where the cranes are to be used, or perhaps while the vessel is at anchor
waiting to go alongside if it is safe to do so, a thorough examination should be carried out. Things to look for are as
follows:

Photo 4The control panel in the cab− 11 −

1

All controls and the various limit switches and cut-outs are functioning correctly.

２

All electrical components and gear are dry and operating correctly.

３

All machinery and machinery housings are dry and operating correctly.

４

All wire ropes are satisfactorily lubricated and all swivels move freely.

５

All sheaves are satisfactorily greased and move freely.

If any defects or problems are identified during the inspections, corrective action should be taken without delay. For
example, if it is found that the cargo hook swivel is somewhat stiff it should be greased or, if necessary, dismantled,cleaned, re-built and greased to ensure that it is completely free. Also, parts of any of the wire ropes which appear to
be dry, for example in way of the sheaves when the crane is stowed for the voyage, should additionally lubricated asnecessary.

During cargo operations
During all cargo operations the duty deck officers and duty crew members should continually observe the operation of
the cranes and the working of all their parts. If any part appears to be malfunctioning the crane should be stopped andcorrective action should be taken. For example, if the machinery is not functioning correctly and smoothly the chiefengineer should be notified and tests and examinations of the machinery should be carried out, following which any
necessary repairs should be completed. Also, if any of the sheaves or any of the bearings are not functioning correctlyor are making unusual noises, investigations should be carried out and any appropriate repairs or greasing should be
carried out.
Throughout cargo operations all limit switches must be operable and they must not be over-ridden. The over-riding
or by-passing of a limit control must only be carried out in special circumstances and under the direct supervision ofsenior ship's staff and not during normal cargo operations. An example of when over-riding is acceptable is when the
jib is being lowered onto its cradle in the rest position.

− 12 −JAPAN P& I CLUB

Photo 5The controls in the cab

If it is found that the driver of a crane is not operating the crane correctly in any way, the cargo operations should besuspended and an investigation should be conducted.
a

If the driver is a crew member, an internal, onboard assessment of that crew member should be
conducted and either that crane driver should receive further instructions with regard to the operationof the crane or an alternative, fully and properly trained crew member should be directed to drive thecrane during the cargo operations.

b

If the driver of the crane is a stevedores' employee, the master should prepare a letter of complaint
directed to the stevedores and other appropriate parties and should request details of the driver's
experience and copies of any appropriate certiﬁcates of instruction. An investigation should then be
conducted together with representatives of the stevedores to establish why the crane driver was
mis-handling the ship's crane. If appropriate, an alternative, suﬃciently trained, crane driver should bedirected to drive the crane before cargo operations are resumed. Records should be kept of all discussions held, to include the details of all parties taking part, of the discussions and of all decisions taken.

After cargo operations
Following completion of a period of cargo operations during which there have been no particular incidents of note,
there should be a general, overall inspection of the cranes and their equipment to establish whether or not any damage
has been sustained. A record of the inspection should be kept with details of any damages or defects found. If any
damages or defects are found remedial work should be put in hand as appropriate. If structural repairs are carried out,
or if work associated with load bearing systems is done, the crane should be re-tested with a proof load by a competentauthority recognised by the Flag State, or other certifying authority on behalf of the Flag State.
It should be borne in mind that a crane which is fully and properly maintained is less likely to suffer a failure or thedevelopment of a defect during its normal operation. If a defect does develop, records of all inspections, maintenanceand any work carried out will assist with demonstrating that due diligence has been exercised to ensure, so far as
possible, that the crane was apparently in normal working order before the defect was identified.
− 13 −

Incidents involving damage to a crane
When an incident involving one or more of the ship's cranes occurs during cargo operations, be it major or minor in
extent, the crane(s) should be immediately stopped and an investigation and inspections of the crane(s) should bestarted.
Incidents might include failure of electrical or mechanical components, failure of a hoist or luffing wire or failure ofany part of the structure of the crane, any bearings or sheaves. The incident might have been brought about by mishandling of the crane by the crane driver, by contact between the structure of the crane and another object - possibly
the cargo being handled or another crane - or may be the result of an unforeseen failure of the maintenance and repair
system on board.

Photo 6

The jib of this crane collapsed and suﬀered extensive damage as a result of a mechanical failure

The investigation should establish facts as follows:1

The extent of the failure and what parts of the crane(s) are involved.

２

The reasons for the failure.

３

The extent and nature of all repairs which are necessary.

− 14 −JAPAN P& I CLUB

Remedial action should then be started, without delay, and the classification society should be notified. If structural
repairs are carried out, or if work associated with load bearing systems is done, the crane should be re-tested with aproof load by a competent authority recognised by the Flag State, or other certifying authority on behalf of the Flag
State. All broken or failed parts should be retained for future testing and examination. Records of all incidents should
be kept, with details of all findings and remedial action taken. Additionally, a report, including full details, should be
issued to the operators' office.

Photo 7

These wires failed when overloaded

Grabs and their use
Bulk cargoes are handled either by some sort of conveyor system with either a spout for delivery or a suction or
bucket leg for off-loading, or by grabs. The grabs might be stevedores' equipment fitted to on-shore stevedores'
cranes, might be stevedores' grabs fitted to ship's cranes, or might be ship's grabs fitted to ship's cranes.
Although the grabs used by stevedores in conjunction with shore-side cranes might be any one of a number of types
and designs, grabs used in conjunction with ship's cranes are usually of the clamshell type, connected to and liftedby the crane hook with the opening and closing mechanisms within the upper part of the grab. Usually, the opening
and closing mechanism is by hydraulic cylinders powered by an electric pump, powered either from the ship via anumbilical cable plugged into the ship's electrical supply system or by a power pack incorporated into the machinery of
the grab and operated via a radio control system. Occasionally, mechanical grabs with a wire and latch opening andclosing system, sometimes known as dump grabs, are used.

− 15 −

Grabs from ashore
If grabs are provided from ashore, before they are taken into use with ship's cranes they should be fully inspected toestablish whether or not they display any damages or defects; if any damages or defects are found, details of theseshould be recorded for future reference. The grabs should then be properly fitted to the crane hook or cargo block,as appropriate, and should then be fully tested to ensure that the grabs function correctly. If a grab fails to function
correctly, it should be removed from the crane's hoist wire and returned ashore. Only fully functioning grabs shouldbe put into service.

Ship's grabs
With regard to ship's grabs, they should be the subject of part of the ship's planned maintenance regime and routine
inspections and maintenance should be carried out. That routine maintenance and inspection regime should include
the thorough inspection of all structures of the grabs and their mechanical parts, and of any associated equipment,
including any umbilical cables and control systems to ensure, as follows:1

All moving parts are free and well greased.

２

All machinery and control systems are functioning correctly.

３

Hydraulic oil reservoirs are ﬁlled to the appropriate level.

4

All parts are without defect or damage.

If any defects or damages are found, corrective action should be taken without delay. A record of all inspections
carried out and the findings of the inspections, of all maintenance done, and of any repairs or renewals, should be kept
for future reference.
Before each ship's grab is taken into use for cargo operations, it should be rigged to the cargo hoist wire of the ship's
crane and should be fully tested to demonstrate its fully functioning capability. A record of that testing should be
kept.

− 16 −JAPAN P& I CLUBGrab capacity and safe working load

The technical specification for a clamshell grab will include its capacity in cubic metres, its weight in tonnes, its
dimensions in metres and details of its operation. The capacity might be a single figure, or might be two or more
figures, if spill plates or moveable panels are fitted to the grab, which can be removed or put in place to alter thecapacity of the grab when closed. The capacity of typical grabs used for the loading and discharging of bulk cargoes
using ship's cranes ranges from about 4m3 to about 16m3. The weight of the grab might be about 2 tonnes or as muchas 12 tonnes. This should be shown on the name plate attached to the grab.
The weight of cargo which can be lifted by a grab depends upon the capacity of the grab and the density, or the stowage factor, of the commodity. When calculating the weight of cargo lifted by a grab, it should be remembered that
it is likely the surface of the cargo in the grab will be slightly peaked or crowned, such that a greater weight than thevolume of the grab might indicate will be lifted. An allowance for this of 25% should be included in any calculation.

All ships' cranes are designed for particular operations
and are certified to have a particular safe working load(SWL), dependent upon the strength of the structures of
the crane and the strength of the wires which are fitted.
That safe working load will be for hook operation, thatis, for the loading and off-loading of cargo lifted byslings attached to the cargo hook. For pedestal cranes
the SWL is also only applicable between the maximum
and minimum working radii.
If the crane is designed for both hook operation and forgrab operation, it is likely to be given two different SWL
ratings by the manufacturer, one for hook operations andone for grab operations. It is usual for the grab operation
rating to be 20% less than the hook operation rating.
For example, a crane having a safe working load of 35
tonnes for hook operation will be down rated by 20%,or by 7.0 tonnes, such that its SWL for grab operation
would be 28.0 tonnes. It must be remembered that thisSWL includes the mass of the grab. The two SWL
ratings should be stated on the plate on the crane jib.

Eg.

Total lift taken by the crane wire
For example, for a grab of capacity 10m3
and weight 4 tonnes, handling a cargo ofdensity about 2.0 tonnes/m3 or stowage
factor 0.5m3/tonne, the grab would lift 25
tonnes of the cargo (that is 20 tonnes
plus the 25% allowance of 5 tonnes),such that the total lift taken by the cranewire would be 29 tonnes.

total lift taken by the crane wire
would beGrab capacity

Cargo density

10m

2.0 tonnes/m3

Stowage factor

Grab weight3

4 tonne3

0.5m /tonne− 17 −

29 tonnes.

Photo 8

The plate on the side of the jib shows a SWL for hook work of 35
tonnes and a SWL for grab work of 28 tonnes.

The allowance given by the crane manufacturer is for a number of reasons, some of which are technical and some areoperational. When a crane is used with a grab fitted to the hoist wire, the crane will lift and transfer a loaded grab in
one direction and, after the load is released, it will lift and transfer an empty grab in the other direction, such that thecrane will be transferring a load at all times when in operation, whereas in hook operation a load is transferred in only
one direction. In order to compensate for those increased loadings on the structures and mechanisms of the crane, adown rating is applied. From the operational point of view, when a grab is closed in order to take a load from the pilealongside or in the hold, the grab will bite into the pile and become partly submerged. When the hoist wire motor is
engaged the wire will be tensioned as the weight of the grab and of cargo is taken and that weight will be, effectively,
greater than the weight of the grab and the weight of the cargo it can hold, as discussed above. Initially, there is likely
to be some cargo on the shoulders of the grab, or in the grab, in addition to the 25% allowance, to increase the weight,
and because there will be an amount of suction between the lower part of the grab and the cargo beneath the grab in
the pile, there will be a further increase in the weight being lifted. Additionally, there might be a very rapid take-up
of weight by the hoist wire as the full grab is lifted or a rapid release of the load when the grab is opened, such that asnatch loading might be applied to the hoist wire, its structures and the mechanisms of the crane itself. These various
factors are taken into account by the application of a small down rating of the safe working load of the crane for grab
operation.
For grab operation of a crane which is not specifically designed for grab operation and is therefore not given a grab
operation safe working load, consideration should be given to applying an allowance whenever grabs are used for theloading or off-loading of bulk commodities.

− 18 −JAPAN P& I CLUB

SafetyThe safety management system for the ship should include a manual in which there are all the various procedures
to be adopted for safe working practices during cargo operations and during maintenance and repair of the cranes orderricks on board. Those procedures and any other or additional procedures should be followed. Maintenance ofcargo handling equipment should be planned and work assessments should be completed, and all appropriate personalsafety equipment and appropriate working equipment should be available and in good condition. Where appropriate, apermit to work should be issued. Before cargo operations are begun, discussions should be held to plan the operationand to identify any risks or problems which might arise.

− 19 −

With Collaboration from Brookes Bell
Brookes Bell - Liverpool Oﬃce
Martins Building Water Street Liverpool, U.K. L2 3SX
Telephone: +44 (0)151 236 0083
http://www.brookesbell.com

JAPAN P& I CLUB
Websitehttp://www.piclub.or.jp● Principal Office（Tokyo） 2-15-14, Nihonbashi-Ningyocho Chuoh-ku, Tokyo 103-0013, Japan
Tel：03-3662-7229 Fax：03-3662-7107● Kobe Branch

6th Floor Shosen-Mitsui Bldg. 5, Kaigandori Chuoh-ku, Kobe, Hyogo 650-0024, Japan● Fukuoka Branch

6th Floor Meiji-Dori Business Center 1-1, Shimokawabata-machi, Hakata-ku, Fukuoka 812-0027, Japan● Imabari Branch

2-2-1, Kitahorai-cho, Imabari, Ehime 794-0028, Japan● Singapore Branch

80 Robinson Road #14-01B SINGAPORE 068898

Tel：078-321-6886 Fax：078-332-6519
Tel：092-272-1215 Fax：092-281-3317
Tel：0898-33-1117 Fax：0898-33-1251
Tel：65-6224-6451 Fax：65-6224-1476● Japan P&I Club (UK) Services Ltd

38 Lombard Street, London EC3V 9BS U.K.
Tel：44-20-7929-3633 Fax：44-20-7929-7557− 20 −