425
1 INTRODUCTION
There are numerous criteria that can be used for
estimating the ‘safety of navigation’, ‘safety of
shipping’aswellasestimating‘safespeed’(velocity)
when maneuverings and shiphandlings on
navigational waters including restricted sea areas. If
we say that something has a particular quality by
definition, it mea
ns that it has this quality simply
becauseofwhatitis.Unfortunatelythereallifeisnot
so easy especially with reference to the
communication link between the old and new
generation of seafarers from the international i.e.
multicultural crew. Have we forgotten that the old
captainshadtobeunderstoodwhentheygaveorders
totheircrew,whomtheyhadshanghaied?
Shipstyleandcompanystylehaschangednowto
Standard Operation Procedure (SOP) same as
seam
anship has changed to competence and so on.
Nowadays we expect from the seamen to have the
adequate knowledge, skills,competences and
proficiency. They have to be familiar with the
standardproceduresaswellaswiththestandardized
int
ernational terminology used for the official
communicationonthebridge.
Knowledge can be defined as a clear certain
perception of something including the act, fact or
state of knowing and understanding. Skill can be
definedas anart
,craft orscience, especiallytheone
involving the useofthehandorbody (motor skill).
Being competent means answering all requirements
aswellasbeingfitforthepurpose.Proficiencyentails
skillfulnessobtainedintheprocessofgainingspecial
knowledge.
According to the STCW95 the minimum
ma
ndatorystandardsofcompetenceformastersand
chiefmatesofshipsof3000grosstonnageormoreare
maneuvering/handlingshipinallconditions(STCW
95,tableA2/II).Bearinginmindthatthemasterhas
the ultimate responsibility for the safety of the ship,
its passengers, crew and cargo, and tha
t the chief
mate shall be in a position to assume that
responsibility at any time. It means that all officers
(especiallycaptainsandchiefofficers)areexpectedto
have adequate knowledge, skill and competences
with reference to ship maneuvering and ship
handlinginallcondition.
According to ColRegs (International Rules and
Reg
ulationsforPreventionofCollisionsatSea)[4],every
vesselshallatalltimesproceedatasafespeedsothat
Determining Ship’s Safe Speed and Best Possible Speed
for Sea Voyage Legs
G.Rutkowski
GdyniaMaritimeUniversity,Gdynia,Poland
ABSTRACT:Thepurposeandscopeofthispaperistodescribefactorstoconsiderwhendeterminingtheship’s
safespeedaswellasthebestspeedfortheseavoyagelegsincludingdirectionsrelatedtovesselspeedthatare
given in ColRegs, voyage orders and charter pa
rties. Author also tried to describe the definition for the
followingnotions:shipmaneuvering,shiphandling,safespeed,bestpossiblespeedforseavoyagelegs.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 10
Number 3
September 2016
DOI:10.12716/1001.10.03.07
426
she can take proper and effective action to avoid
collision and be stopped within a distance
appropriate to the prevailing circumstances and
conditions. Bearing in mind that as per voyage
instruction and charter party requirements every
vesselshallalsoundertakesherpassageatseaatthe
best possible speed, weather
and safe navigation
permitting,unlessotherwiserequired.
Additionally, we need to accept the fact that the
maritime terminology has been developed over
centuries and the meaning of the following notions
like‘safespeed’, ‘best possible speedfor sea voyage
legs’, ‘ship maneuvering’ or ‘ship handling’ in
restrictedsea areas is
notalways the sameand now
theremightbeaneedforsomedefinitions.
2 SHIPMANEUVERINGANDSHIPHANDLING
When we talk about ship maneuvering we basically
thinkaboutchangesincoursesand/orspeedinopen
water,usuallytoavoidothershiptraffic.
Theshiphandling(comparetoshipmanoeuvring
definition), is a very special one and means close
quarterworkdoneprimarilybypilots.Shiphandling
is the control and navigation of ship by use of
engines,rudders,thrustersandtugsasneeded,taking
into account the environmental factors such as tide,
current,wind,seawavesandweatherforecast.
Ship
handling may be also explained as the use of forces
under control (like engine, propellers, rudders,
anchor,moorings,thrusters, tugs)toovercomeforces
thatarenotundercontrol(wind,current,wavesetc.).
However, we also need to remember that there are
some forces and momentum under indirect control
(i.e. ship’s
hull, hydrodynamic inertia and
hydrodynamic momentum e.g. from tugs) which
mustbetakenalsotoourconsideration.Ashipcanbe
more successfully and safely handled by taking
advantageof,andcooperatingwith,theelementsto
the fullest extent‐instead of disregarding and
workingagainstthem.
3 SAFESPEED
ASPERCOLREGS
Accordingto Rule No 6 in ColRegs [4], everyvessel
shallatalltimes proceedatasafespeed so that she
cantakeproperandeffectiveactiontoavoidcollision
andbe stopped withina distanceappropriate to the
prevailing circumstances and conditions. In such
caseswhat
isasafespeedwilldependonthevessel
andcircumstances.
Itis worth restating thatRuleNo6appliesto all
vessels in every situation where the ColRegs apply,
which is on the high seas and all waters connected
therewith navigable by seagoing vessels. Rule 6
requiresfrom
ustomakeourownjudgementonthe
appropriatespeedforourvessel,takingintoaccount
the situation we are in and the situation we are
movingtowards.
Almost all of the foregoing is quite obvious‐if
visibilityispoor,thenitisdangeroustogosofastthat
thereis
toolittletimetoavoidahazard.Agoodrule
istobeabletostopourshipinhalfthedistance we
cansee‐althoughthatdoesnʹtpreventthevesselwe
meetnotbeingabletodothat!
Excessive speed contributes too many collisions.
Rule5inColRegs
onlookoutandRule6areclosely
linked.IfwedonotobeyRule5,wecannotobeyRule
6.Generallya‘safespeed’isareducedspeed,because
in most cases, if either ship reduces speed, their
closest point of approach (CPA) will increase. Then
theriskofcollision
willreduce.Itgivesusmoretime
to think and to act. Time to think and to act is all
important too much speed and too little time can
fatallyimpairourriskassessmentprocesses.Itallows
usto stop more effectively. Ifacollisiondoes occur,
theresulting
damagewillbealotless.
On Fig.1 (as an example) there are presented
manoeuvring stopping tests carried out on tunker
shipbyrunningmainenginefullastern,whenvessel
was proceeding forward with maneuvering speed
half ahead and velocity about 7 knots (3,6 m/s) on
deep water as well as
on shallow water. From the
manoeuvring tests we can seethat on deep water
themostofthevesselsstopsinabout4shipslengths.
Thebridgehashardlylefttheoriginaltrack.Atstop,
the vessel has altered course about 87º to 90º. As a
ruleofthumb:3
knotsequalsastoppingdistanceof1
ship length. However on shallow water the vessel
stops in about 6 ships lengths, and time needed is
about 50% longer! As a rule the stopping distance
usuallyincreasesinshallowwater.Atstop,thevessel
hasalteredcourseabout100ºormore.Notice
thatthe
shiphaslefttheoriginaltrack.Bearingalso in mind
that ship manoeuvring characteristic posted usually
onthebridgeonwheelhousepostersarenotthesame
even on sister’s type ships and as a result of such
measurementsofherstoppingdistances themeaning
andunderstanding of safe
speedcan be different on
different vessels (for reference seealso Table 1 with
manoeuvring stopping test carried out for PS class
containervessel“EmmaMaersk”).
Figure1.Manoeuvringstoppingtests ondeepwater(onthe
left)andshallowwater(ontheright)byrunningfullastern
from7knots.
427
Table1.”CrashStop”/FSAHFAStestestimatedforPSClasscontainervessels”EmmaMaersk”(15000TEU,IMO9321483,
lengthoverallLOA=397.60m,breadthB=56.40m,CB=0.598coefficientfactor,heightHc=76.50m)inacalmsea,withno
currentandSW3°Bwind.Source:MaerskLineShiphandling
8.02.01andShipManeuverabilityL203L210documentation.
[5]
__________________________________________________________________________________________________
MAINRPM LOADEDCONDITIONBALLASTCONDITION
ENGINET
D=16,0m;TR=16,0m,DWT=156907TD=7,12m;TR=10,82m(D122219t)
POSITIONVelocity TimeAdvance Transfer Velocity TimeAdvance Transfer
V[kn] T
Stop[min] PC[m] PB[m] V[kn] TStop[min] PC[m] PB[m]
__________________________________________________________________________________________________
SFH 104 25,7 20,17’7800 1509 27,5 12,75’5170 1000
FH6516,4 14,58’4716 1358 18,1 9,75’3126 900
HH 5012,4 11,67’2900 992 14,1 7,42’1970 675
SH358,65,03’892 184 9,73,42’607 125
DSH 256,03,25’630 110 6,82,25’428 75
__________________________________________________________________________________________________
TheColRegssetoutsomefactorstobetakeninto
account by all vessels and vessels with operational
radar. However the ColRegs ‘bets are hedged’ by
sayingthatthefactorsintherulesare‘among’those
to be taken into account. According to ColRegs in
determining a safe speed
(vSR) the following factors
shallbeamongthosetakenintoaccount:
Byallvessels(v
s):
thestateofvisibility(STV);
thetrafficdensity(TRD)includingconcentrations
offishingvesselsoranyothervessels;
the maneuverability of the vessel with special
referencetostoppingdistanceandturningability
intheprevailingconditions(VM);
atnightthepresenceofbackground
lightsuchas
fromshorelightsorfrombackscatterofherown
lights(PBL);
thestateofwind,seaandcurrent(WSC),andthe
proximityofnavigationalhazards(PNH);
thedraught(T)inrelationtotheavailabledepthof
water(h).
Additionally, by vessels with operational
radar
(v
R):
thecharacteristics,efficiencyandlimitationsofthe
radarequipment(LRE);
anyconstraints imposed by the radarrange scale
(RRS)inuse;
theeffectonradardetection(ERD)oftheseastate,
weatherandothersourcesofinterference;
the possibility that small vessels, ice and other
floating
objectsmaynotbedetectedbyradaratan
adequaterange(PD
SO);
the number, location and movement of vessels
detectedbyradar(NLM
VD);
moreexactassessmentofthevisibilitythatmaybe
possible when radar is used to determine the
range of vessels or other objects in the vicinity
(AV
RR).
Taking into account all mentioned above factors
themeaningofthe‘safespeed’asperCOLREGScan
bepresentedusingthefollowingformula:
RSSR
vvv [m/s] (1)
where:
v
SR‐ safe speed determining by ship which is
equippedwithoperationalradar;
v
S safe speed determining by ship without
operational radar, ship not equipped with the radar
orshipnotusing theradaronseapassageorwhen
maneuveringonnavigationalwaters,where:
h
T
PNHWSCPBLVMTRDSTVfv
S
,,,,,,
1
[m/s](2)
v
R‐additionalcomponentofsafespeed,whichneed
tobetakeintoconsiderationbyshipwithoperational
radar,where:
RRVDSOR
AVNLMPDERDRRSLREfv ,,,,,
2
[m/s](3)
InsuchcasesbasedontheColRegsexplanationthe
safespeedcanbedeterminedonlywhenwetakeinto
consideration all factors mentioned above, bearing
also in mind that some extra explanation regarding
determining safety speed can be justified (i.e. for
fishing vessels, background lights, maneuverability,
draughtinrelation
totheavailabledepthofwater).
With reference to the fishing vessels their movements
are often difficult to predict. It can be difficult to state when
the vessels are acting together, which might make it
dangerous to pass between them; their working lights can
make it difficult to keep a good look-out; crews’ attention
can be distracted when working with nets and etc. Taking
all above into consideration the fishing vessels are
specifically mentioned in ColRegs as ships in special
conditions with the separate rules and regulations.
The maneuverability of a vessel in the prevailing
conditions is an important factor. And this is not just the
case for large vessels. In some cases for the example the
smaller power-driven vessels with shallow draught and
high topsides can experience a lot of leeway at low speed.
This can mean that a safe speed for a motor cruiser might
be higher than for a sailing vessel in a marina - just to keep
the control and if needed change the course and/or speed to
avoid collision.
Shore lights can be a particular problem. It can be
difficult to distinguish ship’s lights and navigation marks
from shore lights. A technique used by aircraft pilots can
be very useful in detecting small movement. Instead of
scanning continuously, concentrate on one direction for a
second or two, before moving on to the next “sector”. This
can reveal even very small movement very well. Of course
there is always risk that the hazard may not be moving!
A less obvious factor to be considered is a vessel’s
draught in relation to the available depth of water. In
shallow water even large ships can experience effects when
moving at speed, such as “squatting” - the draught
428
increases and swings toward the shore. The ColRegs
require a vessel constrained by her draught to navigate with
particular caution, having regard to her “special” condition.
However the ColRegs state that only a power-driven vessel
can be constrained by draught.
In determining a safe speed by vessels with operational
Radar there are some additional factors (listed above in
ColRegs), which shall be among those taken into account.
For example, the detection of hazards might well require a
vessel with radar to proceed at a slower speed than one
without. In such cases it is entirely possible for restricted
visibility to be undetected by the unaided eye - especially
on moonless, cloudy nights. A vessel without radar may
be unaware of an approaching vessel concealed by fog and
proceed at a higher speed.
According to ColRegs we are responsible for
proceeding at a safe speed all the time. If an alteration of
speed is necessary, we do not have to ask permission.
Radar and ARPA are not infallible. They may miss some
targets altogether or they may show large targets as weak
echoes. Navigational aids such as ECDIS and GPS can be
equally suspect. Never rely on one instrument or on one
technique – always cross-check. In such cases we need
constantly monitor our speed – the situation at sea is always
changing and a safe speed in one situation can be too fast in
another. And the situations can be changed suddenly.
Unfortunately in the real life depends of the human
perception and experiences the meaning of safe speed can
be recognized in different way by different seafarers and
not always with appropriate understanding
(comprehension) as it shall be expected in ColRegs.
4 VOYAGESPEEDANDCHARTERPARTY
REQUIREMENTS
Normally a vessel undertakes her passage at sea at
thebestpossiblespeed,weatherandsafe navigation
permitting, unless otherwise required. This may be
adjusted according to environmental conditions,
specific ship’s
owner and/or ship’s manager
instructionsortomeetcharterpartyrequirements.
With reference to charter party requirements
under a voyage charter, usually there is no direct
penalty for failing to meet the speed requirements
specifiedinthecharterparty.Theremay,however,be
incidental claims against ship’s owner or ship’s
managerifthevesselisinordinatelydelayed. Before
the vessel has actually entered a charterer’s service
under contract, the vessel may be advised on
adjustingherspeedandroutedappropriatelytomeet
the “laycan” requirements for the voyage. Upon
enteringacharterer’sservice,thevesselmustcomply
withtheappropriate
charterparty(C/P)speedclause
or charterer’s voyage instructions. However, an
average speed of plus or minus 0.5 knots (±0.257
meter/second)isacceptable.
Under a time charter party, a vessel’s speed is
subjecttotherelevantC/Prequirements,andspecific
penalties result if these requirements are not met.
There may
also be specific routing requirements
wherespecificdistanceshavebeenagreedinadva nce.
Maintain relevant records and documentation to
provideadequatereasoningtosupportrouteselection
oranydeviationfromC/Prequirements.
UndertheCarriageofGoodsbySeaAct(COGSA),a
vesselmaydeviatefromhercontractedpassageonly
to save life at sea. This is incorporated into most
charter parties and bills of lading. Deviation of the
vesselfor other purposes can compromise insurance
coverageofthevesselaswellashercargo.
Generally it means that deviation from the
contractedoragreedrouteisnotpermittedunlessfor
reasons of safety or rescue. All deviations must be
communicatedtotheshipteam,shipownerandship
insurance department. Vessels who participate in
weather routing who are recommended to deviate
fromtheir originaltrackmaydosoasthiswouldbe
considered reasonable. More information is usually
available in
“Voyage Orders and Instructions” plus
companyspecificprocedurei.e.inTeekayprocedure
SP0496[1].
If requested to slow down the vessel or vary the
Estimated Time of Arrival (ETA) to suit the
charterer’s or terminal scheduling, which may cause
significant loss of lay time in port, the Master must
immediately advise
ships team management (both
commercial and technical operations). Written
confirmation will be sought from the charterer to
safeguardagainstanycommercialloss.Ifadiversion
is required, the Master must discuss with both
technical and commercial operations and
arrangementswillbemadeaccordingly.
WhenvesselisunderTimeCharter(TC)
theremay
beclaimsforover/underperformanceagainstspeed
or consumption warranties. Under charter party
exclusions, those periods when speed had to be
reducedduetoinclementweather(subjecttocharter
party agreement on applicable sea state) as well as
those periods when ordered to do so by the
time
chartererwillnotbesubjecttoanyclaims.Therefore,
itismostimportanttomaintainrelevantrecordsand
documentationtosupportrouteselectionandanyre
billablecostsandclaims.
ProceedingatTCP(timecharterparty)speedmeans
that the vessel is to attain a speed over the
ground
equal to that specified in the time charter party
warrantyofperformance.Thevoyageorder:“Proceed
at TCP speed 14 knots”, means that the vessel is to
attain proceed to next port of call with speed over
ground equal to 14 knots (7.207 meter/second) and
thenall exceptions of the
relevant charter party will
apply.
Proceeding at econ speed according to the new
voyageorders meansthespeedthatwillproducethe
lowest tones per mile consumption of main engine
and boiler fuel, consistent with weather, safe
navigation, and prudent machinery operating
practices.
HoweverwhenCaptainreceivesthevoyage
order
i.e.:Proceed on laden passage at 12 knots”,this means
that the vessel’s main engine speed is to be set to
enable the ship to attain an average speed over
ground of at least 12 knots (6.177 meter/second) for
the passage. An average speed of within 0.5 knots
(±0.257
meter/second)isnormallyacceptable, weather
andsafenavigationpermitting.Therefore,ifbecause
offavorableconditionsorovercompensationduring
adverseconditions,thecumulativespeedturnsoutto
be higher than target as the vessel approaches her
429
destination,thevessel’sspeedshouldnotbereduced
merelyforthepurposeofattainingtargetspeedover
the passage. Similarly, under a voyage charter, the
vesseldoesnotalwayshavetospeedupbeyondthe
C/P speed to meet the general average speed of 12
knots. The Voyage Manager /
Voyage Operations
Coordinator (VOC) monitor all such cases for
compliance with the charterer’s requirements in
accordancewiththecontract.
The order: Proceed at min slow speed”, means the
minimum sustainable speed on main engine,
consistentwithweather,safenavigationandprudent
machineryoperatingpractices.Ontheotherhandthe
order: Full speed means the maximum sustainable
speed on the main engine, consistent with weather,
safe navigation and prudent machinery operating
practices.
Therearesomefactorswhicharetobetakeninto
consideration regarding expected voyage speed and
responsibilities. Usually in each company Voyage
Manager consults with the Master to
ensure that
voyages can be undertaken as per the contracted
charterpartysafelyandefficiently,inacosteffective
manneratthebestpossiblespeed.
On ship’s side there is a Master, who makes
decisions on the voyage speed so that the voyage is
completedefficiently,costseffectivelyandat
thebest
possible speed, and is always compliant with
international, national, and local laws, conventions,
and regulations governing vessel operations.
However, in all circumstances the main captain’s
responsibilityistoensurethatthesafetyofthevessel,
crew and cargo is not compromised to meet any
requirementsofshipsowner,ship
teammanagement
or the charterer. To do so, he plans and executes
voyages at the best possible speed and as per
charterer and charter party requirements in an
efficientandcosteffectivemanner.Heensuresthata
passageplanhasbeenprepared,andapprovesit.He
is also responsible to
ensure that all navigational
chartsarekeptuptodatewiththelatestcorrections
and navigational warnings, reviews all relevant
weather data, and considers avoiding weather
systems that pose a high risk and taking into
considerationall mentionedabovefactors he adjusts
speedaccordingly.
Heisawareofallchartererand
charterparty(C/P)
requirementsforvoyageroutingandwhenavesselis
not commercially managed by their own ship’s
management team than he is requested to seek
clarification from team management when
instructions from charterers are different from
proceduresusedintheirowncompany.
Navigating Officer designated by Master
maintains
adynamicanduptodatepassageplanat
all times, taking into account any possible changing
conditions,changestodestinationorchangeofcourse
due to weather routing. Whilenavigating the vessel
he needs to comply with ColRegs, navigates the
vessel in accordance with the passage plan and the
Master’s
standingorders.
Duringthe ballast passage leg,if the vessel is on
timechartertheMastershouldfollowthecharterer’s
instructions if deemed safe to do so. In addition he
shouldtakeintoconsiderationthefollowing:
Loading/laycandatesatthenextloadport,ifthe
next
voyagehasalreadybeenfixed.Inthisregard,
itmaybeacceptableforavesseltoarrivehalfway
througha two or three day laycan if this means
that the ballast voyage can be completed at an
economicalspeed.
Ifany repairs are anticipated, either stoppages at
seaor
atanintermediateport.
Market conditions / forward prospects at the
intendedwaitingarea, if thevessel is proceeding
toaplaceorarea“fororders.”
Adjust speed (weather and safe navigation
permitting)foranoptimalarrivaltimewithrespectto
C/P provisions governing how time is counted for
delays due to navigational restrictions at the port,
suchastideordarkness.
When vessel is using SHELLVOY5 (Standard
Form of C/P issued by Shell company), Captain
should adjusts speed to arrive shortly before the
optimum “target” navigational window opens.
Failingthis,heneedstoensurethatthevesselarrives
well
beforethatwindowcloses.
IfvesselisusingASBATANKVOY(StandardForm
ofC/PissuedbyASBA‐AssociationofShipBrokers&
Agents),the “reachableonarrival”provisionin Part
II,Clause9, meansthatthe arrival time isstrictly