panel 1 flory presentation

8/10/2019 Panel 1 Flory Presentation

1/21

1

MooringSystemIntegrity

InExposedLocations

AndNarrowChannels

JohnFlory,TTILLC

SteveBenfield,

TTI

Ltd.

Presentedat

3rd ASME/USCG

Workshop

OnMarineTechnologyandStandards

July,2013


2/21

2MooringSystemIntegrity

Introduction

TensionTechnologyInternational

Largervesselsarenowbeingmooredatterminals

exposedtohighwaves

andsubjectedtopassingshipforces.

Thistalk

discusses

someoftheproblems

and

someofthesolutions.


3/21


Introduction


FiveTopicswillbediscussed:

WaveInduced

Vessel

Motions

and

Tails

HighPerformanceFiberRopeMooringLines

LowFriction,

Low

Abrasion

Fairlead

Liners

PassingShipSituations

MooringArrangementComputerAnalysis


4/21


WaveInducedVesselMotions



5/21

5MooringSystemIntegrityTensionTechnologyInternational


Ajettylocatedoffshore,exposedtowavesandswell


6/21


WaveInducedVesselMotionsandTails

Syntheticfiberropetailsareemployed

ontheendsofmooringlines

toreduce

wave

motion

induced

forces.

11m(36ft)longnylontailsweresuggestedby

theOil

Companys

International

Marine

Forum

(OCIMF)MooringEquipmentGuidelines(MEG).

Thissuggestion

was

taken

as

obligatory

by

manyterminalsandports.


7/21



Onvessels

moored

in

high

waves,

using

short

nylontailsonwireandHMPEmooringlines,

themooringlinesandthetailswerefailing

duetohightensions.

ATTIstudyrecommendedtheuseoflonger

tails,either

polyester

or

nylon.

ThenewMEG3rd editionnowstates

Longer tails may be required

for exposed berths


8/21



Polyesterropes

are

much

more

durable

than

nylonropesinwetcondition.

Butpolyester

tails

are

also

stiffer.

Longerpolyestertailscanprovidethesame

stretchcharacteristics

as

short

nylon

tails.

Newlyintroducednylonropedesigns

have

good

durability

and

may

be

preferred.


9/21

9

Polyestertail

replaced

by

nylon

tail

at

about

0700

hrs.

TensionTechnologyInternational MooringSystemIntegrity



10/21



HighPerformance

Fibers

are

usually

called

HighModulus,buttheyarealsostronger.

Theyinclude:

Aramid (Kevlar*, Twaron*, Technora*)

HMPE(HighModulusPolyethylene)

(Spectra*, Dyneema*)

LCAP(LiquidCrystalAromaticPolyester)

(Vectran*)* Trademarks


11/21



Highperformance

fiber

rope

has

about

the

samestrengthaswireropeofthesamesize.

Ithas

more

than

twice

the

stretch

of

wire

rope.

Itweighsmuchlessandismuchmoreflexible.

Itdoes

not

have

protruding

broken

wires.

Itismucheasierandsafertohandle.

Itcan

be

handled

by

fewer

people.

Itreducesaccidentsandinjuries.


12/21



Becausehigh

performance

fiber

rope

hasmorestretchthanwire,

itsusereducespeakmooringloads.

Butthisalsoincreasesmotionthroughfairlead.

Fiber

rope

is

also

more

vulnerable

toabrasiondamageonthefairlead.

Alowfriction,lowabrasionnylon

fairleadlinerhasbeendeveloped

tosolvethisproblem


13/21



Fiberropemooringlinewearingonsteelfairlead.


14/21


NylonFairleadLiner

TTIdeveloped

anylon

fairlead

liner

to

overcometheproblemoffairleadabrasion.

TTIhad

been

successfully

used

the

nylon

materialtoeliminateabrasionproblems

inoffshore

netting

systems.

TTIthenconductedropeabrasiontests

over

new

and

corroded

steel

fairleadsandoverthenylonmaterial.


15/21


ResidualStrength

After

1500

cycles

between

10

and

30%

of

new

strength.

NylonFairleadLiner


16/21


NylonFairleadLiner

Thenylon

fairlead

liner

is

molded

in

two

parts

whichcanbefittedinexistingfairleadsonships.


17/21


NylonFairleadLiner

Thelowfriction,lowabrasionnylon

fairleadlinerinstalledonboardaship.


18/21


PassingShipProblems

Therisk

of

passing

ship

problems

increases

aslargershipsenterintoand

mooralongside

confined

channels.

Paststudiesofpassingshipforcesmodeled

onlythe

open

water

case.

TTIandCoastal&HarborEngineering

have

now

conducted

computer

modelingofalongsidequayandconfinedchannelcases.


19/21


PassingShipinNarrowChannel

FXmax FYmax MXYmax

OpenWater 59t 363t 57tm

Narrow Channel 452t 140t 18tm


20/21


PassingShipProblems

Comparedto

the

open

water

case:

Surgeforcesessentiallydouble

alongsideasolid

quay

wall.

Surgeforcesagainessentiallydouble

alongsideaquay

wall

in

anarrow

channel,

Resultinginessentiallyquadruplingof

surgeforces


21/21


MooringArrangementComputerAnalysis

Theeffects

of

waves

and

passing

ships

can

be

determinedbydynamiccomputeranalysis.

OCIMFand

SITTGO

mooring

guidelines

nowrecommendcomputeranalysisof

tankerand

gas

carrier

terminal.

Somegascarrierterminalsnowrequirethat

each

vessels

mooring

arrangement

be

vettedbycomputeranalysis.

panel 1 flory presentation

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