Transactions 1986, Koninklijk Instituut van Ingenieurs MarTec, The Netherlands

(ONINKLIJK INSTITUUT VAN INGENIEURS

P1986-4

TRANSACTIONS

1986

TABLE OF CONTENTS

Preface

Ir. H.J. Westers

Chairman K.I.V.I.-MARTEC

Deep sea heavy transports

Ir. J.M.O. v.d. Werf International Transport Contractors Holland B.V.

- International Maritime Organization

Ir. W.A.Th. Bik Nedlloyd Rederij

Diensten, Rotterdam

-2-Large slow-running propellers

Ir. J.H. Wesselo

Dr. Ir. P. van Oossanen

G.J. Reynolds, B.Sc., M.Sc. Ir. M.F. Sinnema Ir. W. Stout

SWDiesel Amsterdam

MARIN, Wageningen

MARIN, Wageningen

MARIN, Waaeningen

V.d. Giessen-de Noord,

Krimpen a/d IJssel

Prediction of seakeeping characteristics

and workability of offshore support vessels

Ir. R.P. Dallinga

MARIN, Ocean Engineering

Division, Wageningen

Drs. A.B. Aalbers

MARIN, Ocean Engineering

Division, Waaeningen

Jaarverslag

K.I.V.I. - MARTEC 1985

Financieel jaarverslag 1985

Sponsors

Ledenlijst

K.I.V.I. - MARTEC

(september 1986)

or/ ec

KONINKLIJK INSTITUUT VAN INGENIEURS

/

,

TRANSACTIONS 1986

Voorwoord

-3-Voor de

tweede,

en voor

mij

_tevens

_{laatste maal}

_heb

_ik

_de

gelegenheid om

via een

voorwoord in

de Transactions

van

onze

afdeling MARTEC

een kort

overzicht van

de stand

van zaken

te

geven wat betreft de uitgave

van deze vorm van communicatie

met

de leden.

In de

eerste

uitgave

van

1985 heb

ik

u

in

een

bloemrijke

beeldspraak verzocht het bestuur van

MARTEC uw oordeel over

ons

initiatief kenbaar te

maken. Het aantal

ontvangen reakties

kan

(helaas) niet de kwalificatie

overweldigend krijgen. Toch

waren

de reakties

van dien

aard

dat het

bestuur heeft

besloten

de

uitgave van de Transactions te continueren.

De

financiering

is

nog

steeds

een

moeizaam

gebeuren.

Een

oplossing

hiervoor

met

de

befaamde

eigenschappen

van

het

tweesnijdend zwaard, zou een

sterke vergroting van ons

ledental

zijn.

Enerzijds levert dat meer tientjes per lid

uit de KIVI-kas

op,

anderzijds wordt het

dan interessanter voor

bedrijven om in

de

Transactions te adverteren.

Ledentalvergroting

is

gezien

het

totale

bestand

van

scheepsbouwkundig ingenieurs

in

Nederland slechts

in

beperkte

mate

mogelijk

in

eigen

kring;

nog

geen

200

van

de

550

afgestudeerde scheepsbouwers is lid.

Dat leidt dus tot rondkijken buiten die eigen kring,

en dan

valt

te constateren

dat de

omvang van

gemeenschappelijke

belangen.

interessen en

de

professionele

raakvlakken

het

grootst

zijn

tussen de

Maritieme

en de

Offshore

Techniek, en

niet

tussen

Maritieme Techniek en Werktuigbouwkunde. De politieke

_beslissing

om aan de Technische

_{Universiteit Delft doze laatste}

_kombinatie

te creeren valt hooguit te verklaren en te verdedigen

_{vanuit het}

-4-geografisch gegeven dat Maritieme

Techniek het "ouderlijk"

huis

niet heeft verlaten, zulks in tegenstelling tot

Vliegtuibouwkunde

(thans

Lucht-

en

Ruimtevaart

geheten)

en

dat

er

zodoende

bezuinigingen op bestuurlijk en administratief gebied te

behalen

ware n.

Aangezien deze

laatste

overwegingen voor

onze

overeenkomstige

KIVI-afdelingen juist in

tegengestelde richting

wijzen denk

ik

dat wij als afdeling MARTEC twee zaken moeten nastreven:

Zoveel mogelijk leden werven uit het aanwezige

bestand van

scheepsbouwkundig (Maritiem Technische) ingenieurs.

Pogingen in het werk (blijven) stellen am tot een

vruchtbare

nauwe samenwerking of zelfs een fusie

te komen tussen

Maritieme Techniek en Offshore Techniek.

lk hoop voor dit streven niet

alleen weerklank te vinden bij

u,

maar ook uw aktieve steun bij het nastreven van de twee

genoemde

zaken, omdat daardoor mijns inziens de belangen van

de

Maritieme

Techniek en

de Offshore

Techniek in

alle opzichten

het

beste

behartigd

kunnen

worden,

met

inbegrip

van

onze

problemen

betreffende publikaties op het (gezamenlijke)

vakgebied.

Jr.

H.J. Westers

Voorzitter afdeling MARTEC

29 september 1986

-5-DEEP SEA HEAVY TRANSPORTS

Ir. J.M.O. v.d. Werf

International Transport Contractors

Holland B.V.

Resume:

Start and development of the heavyload transport

Description of equipment

Systems applied, constructive consequences Stability consideration, seagoing

behaviour

Cribbing, stanchions, seafastening design

Bending moments in legs of jackups

Coneideration wet tow, dry tow and pontoon

transport versus selfpropelled, submersible heavyload ship

Various special projects

Preamble

Dear Sirs, good evening.

Tonight's

subject is heavy transports

across the sea.

I consider it an honor having been Invited

to inform you about my discipline.

Tonight's program looks as follows.

I will try to tell you as much as possible about our engineering, illustrate it by

means of this overhead projector with

sketches and end with some colored slides,

which Is nicer to look at.

The discussion follows after the interval. Should you have difficult questions, please

pose them during the interval, so that I can

consider them carefully before the

discussion starts.

Before closing we will show you a film. Its

an old one, but those amongst you who are

not so familiar with our discipline will get a very good idea. The film shows the loading of a mat supported rig on to a submersible pontoon.

-

6

-I.T.C. history, general outline

Tonight

I am going to give you an

impression about heavyload transport across the sea and in particular about the place of

INTERNATIONAL TRANSPORT CONTRACTORS in this

small world of towage companies and

heavyload transporters.

As over and over again it appears that not

everybody has heard from our company I will

first of all give a brief sketch of the

start of I.T.C.

The company was founded in 1973 by Messr. Jonkman and Burghouwt, both former employees

of Wijsmuller.

Mr. Jonkman had risen there from engineer to

director.

In the salvageworld a method had been

developed to create buoyancy with the aid of compressed air and thus to turn sunken ships into floating ships again.

The transportation of large drilling rigs

increased due to the oilcrisis and their construction in lowwagecountries.

Moreover, with the oildollars huge hydr2ulic engineering works were put out to contract

and loads of dredging equipment had to be

transported across the sea.

Combining these factors the idea was born to

load and transport drilling rigs and dredging equipment on submersible pontoons and thus create a totally new transportsystem.

At Wijsmuller's the young generation had

taken over the reins and they did not like

this idea one bit.

Much against there will the above gentlemen

started off on their own. Their idea proved

to be a golden one and today the new system has become part of the routine.

I.T.C. now operates a fleet of 7 oceangoing

tugs, 15,000 IHP, 3 submersible pontoons

(floating footballfields) and the VLSSHLV "SIBIG VENTURE" (very large semisubmersible

heavyload vessel) with a deadweight of

Activities

Wet tows

Towage of non-selfpropelled floating units, e.g. accommodation vessels, cranebarges, pipelaying barges, drilling rigs, scrap

vessels etc.

Dry tows

Drilling rigs, dredging material, modules, rock transport, small barges (so-called

shuttle transport), cranebarges, pipelaying

barges, jackets etc.

Salvages

For instance in 1984 I.T.C. succesfully rescued:

. 2 laden VLCC's

. 1 new product carrier . 1 loaden freighter . 1 fishing vessel

. 2 bulkcarriers

. 1 combulker

Dockings

The dimensions of most of the drilling rigs

are of such a kind

that they do not fit

in

normal drydocks. Moreover the rigs would

often have to be transported over long

distances. Our SEACAMELS, the submersible pontoons, can easily be towed to the

drilling location and the rig can be docked

for maintenance or repairs without having to be inoperative for a long time.

Engineering

To a lesser extent for the wet, but

definitely for the dry tows and salvages and also for various other activities, such as:

launchings with the aid of submersible

ships

mating operations, assembling of large

floating units

skidding operations, horizontal transport shutes

feasibility studies such as transportation

of MAC., Mobile Arctic Caisson and

Conical Drilling Unit "KULLUK" design:

heavy-load ships ("SIBIG VENTURE")

tugs, anchor-handling tugs fi-fi vessels, etc.

-

7

-The equipment in use for heavy transports

across the sea

A marked development is perceptible in the equipment being used for dry tows. I will outline the technical as well as the economical development. (see fig. 1).

For the very first dry transport a flattop

barge was used with manually operated

valves. On the port and starboard side of the barge's maindeck a number of stanchoins

were placed, through which ran the spindles

of the valves and compressed air connections. The barge engineer went in a

dinghy to the operating point, climbed the

stanchoin, man-handled the valves and then

on to the next. one.

You may understand that when the job is a

hasty one many a time the engineer got wet through.

This type was replaced by the present ''SEACAMELS", which were built around 1975.

They operate according to the pneumatic

deballasting principle, have a forecastle

with engineroom and control panels, and loading takes place by submerging the aft

ship on to the bottom.

For that purpose always a suitable

waterdepth has to be found, the bottom is to

be inspected. Then there is the affect of the tide and the soil conditions. By

submerging on to the bottom quite a bit of

mud enters through the bottom valves, sticks

in the tanks and it

is a problem to remove the mud again.

To eliminate these disadvantages the

competition had built similar pontoons, but

then with bouyancy tanks on the aft ship. After having provided the pontoons with

propulsion, the next development was the

self-propelled heavy-lift ship.

The first generation was the

"SUPER-SERVANT"-class, still a pontoon, but

self-propelled and with accommodation.

The 'MIGHTY-SERVANT" is an enlarged version

of the "SUPER SERVANT".

Dyvi ships are the second generation, real

ships with a superstructure fore and aft.

Yet, before the Mighties and this second

was born to convert a cheap tanker into a

heavylift ship. Unaware of the coincidence

a comparable

heavylift

carrier was developed in Sweden as well as in Holland.

At Haarlem the "SIBIG VENTURE" and in Sweden

the "FERNCARRIER". Both strongly enlarged

versions of the second generation of

submersible heavylift ships. This inspired

one of the naval architects to the following picture (see fig. 2).

Within barely two years the transport

capacity has been increased by four "Dyvl"

ships, three "MIGHTY SERVANTS" plus two

"converted Carriers". Taking into consideration the increased transport

speeds, the capacity had more than doubled. In this period the cargo market did not

increase, on the contrary it rather

decreased. In particular the transportation of modules and dredging material. The

selfpropelled ships took over the cargo of the pontoons and for the latter other

activities had to be found.

The murderous competition, caused by the extraordinary increase of the capacity,

adversely affected the prices. All the new ships. however beautiful and modern they may

be, were not able to break even. Dyvi has

already spent its entire capital, 40 million

Dollars. Ferncarrier had the shareholder

make an additional payment and later on the ship was sold to the Military Sealift

Command for a song and a dance.

Lauritzen sold his two ships to Wijsmuller, who does not have employ for them either, but wants to prevent outsiders from becoming his competitors with cheaply acquired ships.

You have to realize that in general a

shipowner is not exactly applauding the

bankruptcy of a competitor. The latter's

ships remain in existance and because the

new owner can buy them cheap his capital

costs are low and thus a more dangerous

competitor enters the market.

Nothing beats making new designs, preferably

a ship capable of doing absolutely anything.

The crux, however is that money has to be

made and that the company stays alive. Out of the 9 ships that have been put into service since 1982, the "SIBIG VENTURE" is

-

8

-the only ship that can Just break even. As

the "SIBIG VENTURE" was a converted old

ship, initially the criticisms were heard everywhere.

However, now that the ship has been sailing

for some years

with a very high rat of employ,

with an economical speed of 12 knots,

with drilling rigs that could not be

loaded by others,

with double loads (like sales: two rig transports for the price of one),

and moreover that we are not confronted with

astronomical losses, the criticisms passed

over and there is admiration instead.

After this introduction I would like to

tell you about the techniques applied and Its consequences.

1 have already outlined the development of

the heavyload equipment.

The second generation heavyload ships

mainly distinguishes itself from the first

generation by the shape of the ship, so the

linesplan and the superstructure on fore and

aft ship, this creates spare buoyancy,

moreover there is more freeboard for the cargo deck.

Consequently for the second generation ship

the seakeeping is most favorable.

Advantages over wet-tows

In short the most important advantages of a dry tow are the following:

Higher sailing speed, decreasing the

transittime by more than half

Cargo has hardly to be prepared for a

seaworthy condition, preparation of some hours, immediately in working order upon arrival

Because of a better seagoing behaviour,

the legs can be transported full length without having to shorten them

A safer method, less damage and consequently a considerably lower transport insurance

In the field of dredging equipment,

transportation of all required dredgers, barges, small tugs, pipes, pontoons in one safe transport

During the Suez Canal passage considerably

lower transit fees

Example of a 10,000 tons rig transported

over 8,500 nautical miles (see fig. 3)

WET PONTOON SHIP

Days 90 55 30

Premium 3% 0.8% 0.3%

Ballasting / deballasting

It wil I be clear to everybody that when at

the top of a

tank a de-aerating valve will be opened and in the the bottom a

bottomvalve, the tank will fill and if you

ballast sufficient tanks the whole pontoon

will submerge. So you can emerge the pontoon

by closing the de-aerating valves at the top of the tank and by supplying compressed air.

The air expels the water through the

bottomvalve.

This system was applied with the very first

barge.

A compressor was placed on a small pontoon

and connected to the tanks with flexible hoses.

In salvage films you can see that this

system is still en vogue.

Another possibility is to fill and empty the

tank by pumping, which is the normal procedure with shipstanks. I would like to

put the advantages and disadvantages of both systems side by side, in particular for the heavy -load aspect.

Compressed air versus pumps (see fig. 4). - Compressed air:

maximum pressure differential at the top of the tank;

so strong deck, favorable, for cargo has to be stowed here;

pressure differential independent of

submerging depth;

maximum pressure differentia; never more

than depth of ship (H).

-9-Advantages:

aircompressors cheap

2. relatively small high-pressure line

Disadvantages:

remote controlled valves in tanks

breakdowns hard to remedy Operational disadvantage:

I. draft variation implies change of

pressure, resulting in bouyancy differential.

Pumps:

maximum pressure at the bottom of the

tank;

so strong deck (cargo) and strong bottom (pressure) necessary;

dependent on submerging depth (T); maximum pressure differential is max. draft

Advantages:

no mechanical parts in tank

level measuring with pressure gauges

possible

bouyancy independent of T

Disadvantages:

more steelweight in construction

Stability

During all stages cf submerging and loading

there had -to be sufficient stability in order to keep the whole operation under

control.

I trust that you are familiar with the fact

that the

stability consists of a weight

contribution and a form contribution.

reduced by a free liquid deduction.

KB - KG BM - free surface reduction MGr

-(weight) (form)

Weightstability = KB - KG.

An empty ship always has a negative weightstability.

As the tanks are being ballasted, this

becomes less and less negative and with submersible ships it can even become positive.

KB increases rapidly, KG decreases slowly. The formstability equals BM

-

F.S.

reduction.

The formstability for a surface ship is always high.

During ballasting the BM = I/V normally

decreases, mainly by increase of the displacement.

For submersible ships the waterline inertia

moment I strongly decreases at the point

where the cargodeck disappears under water,

while the displacement increases.

In the example, with even keel, while draft = depth, the weight stability Is negative and the form stability just 0, because of the huge superstructure in this example.

(See fig. 5).

As you can clearly see, the stability

becomes negative at the moment when the whole cargodeck gets through the waterline.

So w? never operate this way.

Hence the second diagram applies, now for a trim of 5 m. by the stern. As part of the deck remains above the water, the

waterline-moment-of-inertia is as high as

possible as long as possible (see fig. 6).

Free-surface-reduction can be limited by constructing longitudinal bulkheads. One of

the competitors has one longitudinal

10

-bulkhead only and therefore continuously

problems whilst loading and discharging

those cargoes, which by shape and position

contributes little to the stability.

With an adequate choice of the number of

longitudinal bulkheads and the position of

the KG a pontoon can remain stable even

under water.

For pontoons without an aft superstructure or buoyancy tanks like the Seacamels, the

longitudinal stability rapidly decreases

when the aft deck goes under water. As soon

as this stability is

negative the aft ship

sinks onto the bottom.

This movement is hard to control. The transverse stability is maintained by

choosing a turningpoint that guarantees

sufficient dry deck for form stability. This is clearly demonstrated in the film.

After having touched the bottom we can

submerge the fore-part and the Seacamel will be ready to receive the cargo (see fig. 7).

Once the cargo has been correctly positioned above the Seacamel then deballasting will

take place as follows in order to guarantee

sufficient stability at all stages.

The fore-ship will be deballasted with

compressed air so

far that

the front of

cargo makes contact with a force of a couple

of 100 tons. So now there is a linecontact

between cargo and pontoon. The stern will be

pumped dry so that the bottom pressure

becomes nil.

From the moment the bottom contact is lost

the Seacamel has too little stability of its own and stability is borrowed from the still floating cargo via the linecontact.

The Seacamel tilts around this line against

the bottom of the cargo.

While maintaining a calculated minimal trim

the unit (pontoon and cargo) will be lifted through the waterline with the aid of

compressed air.

The minimal or critical stability occurs

when the width of the waterplane area of the

cargo becomes smaller than the width of the pontoon.

Just as loading with trim is possible you can also load with a list. The essential difference is that when loading with trim

stability is always positive. When loading

with a list the arms of the GZ curves are

negative the first few degrees. So far we

did not have to apply this principle and

that sets our minds at ease.

Now that we are talking about stability I'd

like to tell you something about the

stability during the voyage.

We can calculate two GZ curves, one for the stransportship only and one where the

buoyancy of the cargo is included (see fig. 8).

As in our branche 99% of the cargo

overhangs the carrier and the freeboard as a rule never exceeds

the 4 to

5 metres, the

cargo will touch the waterline and

contributes to the stability after a 3 to

4 degrees list.

This contribution is so substantional that in spite of the enormous windcatching areas

of the jack-up legs and the corresponding

moment arm, excessive windangles do not

occur. So, independent of the initial stability we can always amply comply with

the A.B.S. stability criteria.

Theoretically the initial stability might

approach zero. A practical _difficulty is

that with every breath of wind the ship

would list, the overhang would dip into the water, thus resulting in extra propulsion

resistance.

Seagoing behaviour / motions response

The seagoing behaviour of the heavy-load

ships brings about forces and accelerations

affecting the cargo,

For three reasons the seagoing behaviour is important to know:

I. the part of the cargo must be strong enough to resist the occurring

accelerations and inertia forces, without

permanent damage

the seafastenings, which have to secure the cargo to the ship, are dimensioned

depending on the seagoing behaviour the cribbing design, the wood between deck and cargo, depends on the motions

The seagoing behaviour of ship and cargo is depending on the factors:

waveheight and period band, relative

direction and windspeed

initial stability and radius of gyration of the ship/cargo

dimensions and shape of the ship, existence of bilge keels etc. as well as

speed

Affecting the seagoing behaviour

As generally the transport season and the

route cannot be affected to a large extent, the design waveheight and wave period band

are fixed.

Variables are the wave direction with

respect to the course, possible ports or

refuge and speed of the ship.

The affect of the speed is marginal. During

heavy weather with waveheights of 10 metres

or more, the speed is determined by impact,

slamming, racing of the propeller. etc.

Pitching of the ship.

'the pitch period is low with regard to the wave period of very high waves.

The pitch movements of a ship can hardly be affected. The longitudinal radius of

gyration and longitudinal metacentric height can only vary within narrow limits and do

not cause any change worth mentioning in pitch behaviour.

You may understand that I am pleased to tell you that we have the longest heavy-load ship

arid so as a consequence the best pitch

behaviour.

Rolling of the ship

So much the higher the initial stability GM,

so much the more _{the ship rolls, according} to the formula:

T nat = 2 x Kxx x 1.2

sqrt GM

The higher the GM the lower T flat the

closer T nat approaches the wave period, the

more interference occurs and the more

You see another variable: Kxx, the radius of

gyration. This is mainly fixed by the geometrical ratios. Long legs of a drilling

rig enlarge Kxx.

The factor that can be affected is the GM.

Low GM arises from:

a small ship, but we do not like that, we want a wide deck to place the cargo.

You can see a compromise in the main frame shape of the Mighty Servants, which have

with increasing draft a wider waterline. This creates with a light cargo, so a low draft, a small ship and with a heavier

cargo, more draft, a wider ship. The seagoing behaviour of the

shipcargounit becomes to a lesser extent

a function of the cargo.

This idea is not new, we too wanted to apply it in a design, that was on the shelve 5 years ago, but was abandoned for

efficiency and technical reasons. High systemKG, so high KG and V.C.G.

cargo. A KG ship can be affected at the initial design stage by adjusting the depth of the ship, a large depth requires a considerable waterdepth at the

submerging location at generally a

limitation of the water height above deck

in submerged condition. Top tanks.

The carriage of ballast water in tanks situated under the cargo deck.

If we look at these points for barges and

carriers, then we see that:

Barges: relatively wide, L/B = 3-4.) low KG, ) so high GM no top tanks. Carriers: relatively small, L/B = 4-5.) high KG, ) so low GM

generally top tanks.

If we consider a standard drilling rig of 10,000 tons, then in transportation on a

pontoon the natural period will be 12 to 15 seconds, and with heavyload ship this will

be 22 to 24 seconds or more. As the pontoon-cargounit interfaces with the wave period,

severe seagoing behaviour occurs in heavy

1 2

-weather. The rollangle can double or triple

compared with the roll angle of the heavy

load ships.

The wave direction with respect to the

sailing direction determines to a high

extent the seagoing behaviour. Head seas

cause pitching and theoretically no rolling.

Beam seas cause rolling and theoretically little pitching. Quartering seas course

rolling but to a lesser extent than beam

sea, but moreover pitching and that to a

higher extent than in head seas.

In a transport study the motion and accelerations in these three headings are

calculated as standard conditions.

There are a few more matters affecting the seagoing behaviour:

The overhang of the Cargo, which can

amount from 15 to 20 m, dips into the sea with larger roll angles than 3 to 4

degrees.

There have been quite some talks on this effect ant the opinions are highly dependent on the hat the speaker is wearing, in other words whether he has a transport initiating or supervising

function.

When we did the tanktests with our Sibig

Venture model at Wageningen we could not

help investigating the effect of the

overhang.

For the model with the same natural period

an experiment was made, with and without overhanging cargo, with significant wave

heights of 6 and 12 m

It turned out that

with a 6 m wave damping by the overhang occurred and with a 12 m wave an

intensification of the rolling movement,

both in the region of 10%.

Bilge keels.

Lengthening the bilge keels can decrease the rolling behaviour by 15 to 20% (see

fig. 9).

A third affect not to be underestimated is

the waterline moment of inertia.

Last year there was a transport of a huge drilling rig, the "GLOMAR LABRADOR I." of

13,000 tons, with legs of 135 m length,

where the spudcans, (those are the tanks at

the bottom lower end of the legs. with which the legs are standing on the sea bottom)

were halfway immersed in transport

condition.

Now let us do a small calculation:

say the displacement is 40,000 tons, GM = 4

in, dia spudcan 13 m, A = 133 m2 , Y = 28.5 in Increase in GM is 108,000/40,000 = 2.7 in for each spudcan.

T nat is 30 seconds 2 kxx x 1.2 = 60 1 spudcan in the water: T flat 60/sqrt 7.6

= 23 sec.

2 spudcans in the water: T flat = 60/sqrt 9.4 = 19 sec.

3 spudcans in the water: T nat = 60/scirt

12.1 = 17.24 sec.

A natural period of 17 secs. is a disaster.

We transported the same rig to Rotterdam in

September 1985. By sailing with large

freeboard, 7 in average, where the rig had

been placed, the spudcans stay out of the

water.

Without any problems whatsoever the

transport arrived, thanks to the too

beautiful weather as well.

You should not forget that in addition to

the disadvantageous affect on the seagoing

benaiour the speed strongly decreases too when the cargo parts are being dragged

through the water.

Under these circumstances storm, typhoon and monsoon navigation has to be applied,

because the ship can no longer run ahead of bad weather.

Bending moments in legs of jackup's

As I told you before, one of the important

advantages of the modern heavyload ships is the better behaviour, so that the legs can

be carried full length.

I won't keep from you the calculation's methodology of the occurring bending moment,

as this is purely a bit of theoretical

mechanics.

'We tske the rolling of the ship.

The leg is supported by upper and lower

guide. Let's look at the legpart above the upper guide.

The following forces and accelerations

affect the leg (see fig. 10).

-13-windforce.

calculation of the force according to

A.B.S. or with the aid of windturtnel results

gravity component G sinus phi. Phi is the sum of max. rollangle and wind angle. translation of the centre of gravity of

the leg part as a consequence of the sway

acceleration (double flux Y).

Sc just F = M x a.

translation of the leg part as a

consequence of the roll angular acceleration double flux phi x R with respect' to the roll centre.

R x double flux phi is equal to the acceleration in the centre of gravity of

the leg and so F=Mx a again.

Items 1 thru 4 cause a combined force, that multiplied by half the leglength above upper

guide results into a moment.

last contribution is the rotation of the legpart itself around its centre of gravity according to M = I x double flux phi, in which I is its own moment of

inertia

To incorporate unforeseen affects the total

moment thus obtained will be increased by 20%.

You must see this margin as a safety factor

for slamming of the spudcans, causing

vibrations and rattling of the legs if

clearance occurs in the shims of the guides.

For the max. _{allowable bending moment we}

usually go to 90% of the yielding point.

It is clearly not an exact calculation

method. Maxima are added as if there were no phasedifferences between the various

motions. It is, however, a very practical method, because the motions maxima are known

from the tanktests, Calculation of the phase difference requires an extensive calculating

program, which would not be feasible without a big computer and thus would be very expensive. Moreover it would suggest an

accuracy, which bears no relation to reality at all.

There is no fixed point of rotation for the

roll motion.

generally accepted however to use the

systems centre of gravity.

Cribbing

The cargo is not placed on deck baldly but

on a wooden cribbing of appropriate thickness. This cribbing made from soft wood acts like a cushion and smoothes out

differences in platethickness etc. Normal

height 3-4 inch.

If parts are protruding from the bottom, the

cribbingheight is enlarged by hardwood

blocks

The cribbing designs have changed

considerably during the past years because of a different approach. Of old we

calculated with so many tons per m2 derived from permissible deckloads for cargo not having stiffness of its own, bags of

potatoes or something like that.

The cargo we transport has its own stiffness and the carrying capacity of plateareas on

which this permissible deckload was based,

is no longer relevant.

The cargo is supported by frames, bulkheads,

shell and deckbeams.

Now that we lay the cribbing on these

structural members it does no longer make

sense to talk about tons per m2 but about

tons per running meter.

In the past if too high static loads turned

up, the cribbing width was simply doubled

up, so on paper the load was reduced to 50%,

however forgetting that the extra beam was

positioned in an unstiffened plate area and so provided no contribution whatsoever.

The new calculating technique saves quite a

bit of wood upto 50% and consequently

man hours.

To give an example for a 10,000 tons rig:

OLD METHOD:

10,000/25 = 285 m2 wood

NEW METHOD:

10,000/25 x 0.3 = 120 m2 wood.

So much the higher the cribbing so much more the savings; condition is of course that

sufficient structural members of cargo and

ship are located on the same perpendicular.

1 4

-i just want to go a l-ittle further -into th-is

matter. The weight is never equally divided

over the cribbing for the following reasons:

The stiffness of the shell and the

longitudinal bulkheads is not the same, moreover as per banana theory the cargo is in hogging condition because of Its

overhang. In case of rolling, the load on

the crosssections looks as follows (see

fig. 11): the difference between maximum and

minimum depends on the mutual stiffness.

Upon this static load there will be a

dynamic load as a result of the ship's motions and the wind. The heave motion

increases the parabolic load, and similar to the legs loads, a moment is acting on the

cribbing too. As the cribbing can only take pressure forces, the maximum negative

stresses due to the moment may not exceed

the positive stressses due to weight and

heave, otherwise the rig starts rocking and lift off may occur.

To gain the maximum effect of the cribbing

this will be positioned as much as possible

around the circumference of the rig and as

little as possible in the centre.

In order to be able to perform the

calculations I talked about, the moment of

inertia of the cribbing has to be determined in 3 directions. This is a hell of a job. It is therefore our intention to computerize

these calculations.

Skidding and launching of a semisubmersible

drilling platform in Cherbourg, France. summer 1982.

At the U.I.E. yard in Cherbourg the s.s.

PETROBR.AS XIII" was built on the quayside.

Having no slipway or floating dock facilities, I.T.C. was asked to perform the launching operation by means of a

semisubmersible barge.

For economical reasons it was preferred to use one barge only. This implied positioning of the 10,000 tons rig athwarthsips with

overhang of the pontoons of abt. 20 m on

each side of the barge (barge width 40 m, rig pontoon length abt. 80 m), see fig. 12.

The totally symmetrical position of the rig

on the submersible barge and the skidding

data is outlined on fig. 13.

In those days there had not been a transport of an athwartship placed semi-sub yet. Especially as the four corner columns were

not supported by the barge deck, there could

be a strength problem.

Simple two-dimensional strength calculations

appeared unreliable. We had to describe

barge and rig with 3 dimensional plots. See fig. 14 and 15.

With the well-known Ices Strudl finite

element calculation method, forces and

deflections at the relevant locations could be simulated.

No overstress was found in the rig nor in

the barge (see fig. 16).

The results confirmed the Banana Theory, forces and stresses increased from centerline towards the barge side.

Consequently the deflections show the same

pattern (see fig. 17).

Frames 11 and 18 are transverse bulkheads, frames 12 and 16 are loaded with the skidbeams.

Total engineering and operation of this

complicated job was performed by I.T.C.'s naval architects. The finite element

calculation was run via a terminal on an

I.B.M. mainframe computer.

Double transportations of the jack-up rigs

"ROWAN ANCHORAGE" and "ROWAN NEW ORLEANS" with 2.7 to high cribbing

Two rigs in the Arabian Gulf had to be

transported to the U.S. Gulf. We talk about the summer of 1983. Both are of the same type Marathon LeTourneau class 82. About 6,00C, tons weight with spudcans protruding

2.70 m from Baseline.

The distances of legcentres are that small

that straddling is not possible. The spudcans are that large (14 m dia) that cutting holes into the deck is technically and economically not feasible. We are left

with no other solution but to build a

cribbing of 2.7 m height.

-15-The possibilities are wood, concrete and

steel. Wood is off, because of the price.

Concrete is off, because we are not familiar

with the material, and because of the hardening times required. We think of a standard cribbing, only somewhat higher so

that you get concrete walls on which the rig

is resting. We considered making saddles in

which the spudcans could rest. These could

either be fabricated, but then we would have

problems with the centering, or fast

hardening concrete might be poured under

water after the rig and thus the legs too had been positioned:

This kind of plans never survived the brainstorming stage.

So steel it was.

What is available in the Middle East? No

trees, but a lot of

pipes and those have a good buckling resistance. After some fiddling around with diameters we arrived

for non-technical reasons at pipes 800-900

Mal On top of the pipe a heavy T-beam and on top of this beam a layer of wood. The basic

principle of this pipe construction is that only a vertical force is carried, so that

the pipe is only loaded on buckling and not

on bending.

As usual the horizontal forces of the

seagoing behaviour had to he absorbed by the

"eafastenings. So as not to make it excessively expensive we did not seafasten

against the hull but against the spudcans,

as you can see on fig. 18. Large brackets haven been welded against the spudcans to

get a nice vertical plane and against this

plane our standard seafastenings were

placed.

For the sake of clearness: seafastenings are never welded to the cargo as well as to the

carrier, it is either, or.

This has to do with difference in stiffness

between cargo and ship. Difference in

deflection occurs during hullbending; cargo and seafastening can in a vertical sense

move freely in respect of each other.

Back to the pipes. We arrived at the conclusion that we would need one hundred

pipes for each rig. Top and foot of the pipe

must be

at the

strong points of rig and

ship. So 100 corresponding strong points.

complication. Normally a cargo will be

floated over the cribbing, so there is

enough water on deck of the ship in submerged condition to float the object to

be transported freely over the cribbing. In the present case the cribbing was already 2.7 m high, thus a waterdepth of 4.8 m would

remain above the cribbing. Draft of the hull, however, was 4 m + 2.7 m of the

spudcan = 6.7 m And so were to metres short

to move freely.

We came up with the following solution (see fig. 19): Both rigs were placed

athwartships.

The configuration of the pipes is such that

the bow spudcan can pass through a gallery

of pipes. These pipes support the cantilever bulkheads. To keep the spudcan in its place

we welded rails with a travelling cat tot he

forward bulkhead and a

steelwire

was

measured at the right length. As the ship is at bow anchor only, current and wind provide sufficient strain on this wire, so that it is automatically tensioned. Because of the

fixed length the bowleg swings over the

deck. As soon as the wire lies parallel with

the ship the travelling cat runs on its

own

across the width. This system has been

succesfully applied to both rigs.

I won't keep from you a diagram of the

required trim after loading whilst the cargo

deck goes through the waterline (see fig. 20). HEIGHT feet 142,5 467 102,5 336 BIG BEN

16

-Now I'll just get back to the cribbing. The

permanent configuration as you see it on the picture consists of about 84 pipes. These are

sufficient to carry the static load, the last 16 pipes mainly serve to take up dynamic forces. By lack of space and strong

points 16 pipes are still missing during the loading/floatingin procedure. We called them portable pillars because they were positioned after loading. To make sure that these 16 pipes take these loads, they were,

during positioning, jacked against the hull

bottom with a force of 70 tons and welded to the deck by means of gusset plates.

I can tell you that it is tremendously

satisfying and there is really a load off

your mind if everything works out the way you planned it.

The voyage, 13,000 nautical miles, went via The Cape of Good Hope, then, during a few

aays, the ship sailed though wavss of 9 at and rolled about 8 degrees in 16 secs. As there inevitably always occurs clearance

in the guides of the legs. the front rig

started to move 8 to 10 mm athwartships. After having skimmed this clearance there

were no further problems and the transport arrived damagefree at Brownsville.

A

II

GO SO SO SO SO gg

ge

gig SO SO SO SO GO gig GO 5D GO GO 'Al.' 'Al.' GO GO rje 50 JACX UP RIG

- 1 7

--DEVELOPMENT OF HEAVY LIFT SEMI SUBMERSIBLE SHIPS

FIRST GENERATION

as

S., 90 M. BARGE (1 fl 120 M. BARGE

lb

NEDBARGES

r

ild

SUPERSERVANT

--,---MICiiTY SERVANT 1_,

Oso=

1-Thtt, --

₀₀

P

SECOND GENERATION

DYV1 "SWAN- TYPE

SIBIG VENTURE

_ _

_, :

'1- -r

---, 1 1 t

t

, 1 1 ' i 1 fiq 1

NJ

HOW BIG IS OUR SIBIG ?

WIISMULLER

...

VI=

International Transport

1 9 -KIB

g

rA1 210 FA FA

r

WET TOWAGE

--Lop\

0.8

55

DRY TOWAGE

VOYAGE LENGTH

( days

) PREMIUMS ( 0/0 )

0.3

30

fig3

FA

/A

rA

re

ON BOARD VL SS

VOYAGE LENGTH

(

days

)

PREMIUMS

( 0/0 )

3

90

VOYAGE LENGTH

( days

1 PREMIUMS ( 0/0 )

-20-Ballasting-Deballasting systems

Compressed air versus pumps

from aircompresisor

Compressed air system

-Max. pressure differential at the

top of the tank.

-So strong deck, favourable,for cargo

has to be stowed there.

-Independent of submerging depth.

-Max. pressure differential never

_more

than depth of the shipp.

Advantage

-Aircompressor cheap

-A relatively small high-pressure line.

Disadvantage

-Remote contrdaed valves in tanks,

breakdowns hard to remedy.

-Operational; draft variation implies

change of pressure resulting in

bouyancy differential.

fig 4 [

AP

Ptr) .1111..1

to pump

Pumping system

-Max. pressure differential at the

bottom of the tank.

-So strong deck ,(cargo). and strong

bottom (pressure)necessary.

-Strength dependent on submerging

depth

-Max. pressure differential is

draft T.

Advantage

-No mechanical parts in tank.

Level measuring with pressure

gauges possible.

Bouyancy independent of T.

Disadvantage

-More steelweight in

_contruction

-Heavy pumps and large lines

_are

STABILITY CHARACTERISTICS:

EVEN KEEL

-5

0

21

STABILITY CHARACTERISTICS:

5 m TRIM AT THE STERN

MG BM CARGO DECK meters

fig.

6

V.V

MG BM KG KB

V.V

KB KG 16 15

-22-_

fig 7.

SUBMERGING

PRE-SUBMERGING

POST-SUBMERGING

LOADING + "BIT"

TURN BARGE

UNDER LOAD

MINIMUM

STABILITY PHASE

LOADING SEQUENCE

eljbcSZI

RIGHTINGARM CURVES.

1.5

buoyancy of

rig not included.

-1.0 windarm. -2 5 15

fig.

8 30

buoyancy of rig included.

40 50

deg.

8.0 6.0 1.0 2.0 0.0 0.0 0.5

WAVE FREQUENCY IN RAD/5

fig. 9

1

Influence of length of bilge keels on roll motions

L bil.e

Waves

r

/

it

/ \_\

..

11111111

i

it

\

1.0 1.5

1. WIND

2.GRAVITY

3.

SWAY

COMPONENT

4. TRANSLATION 5. ROTATION

(ROLL)

_(ROLL)

/

/

//

/

//

II

--,

/ /

/

/

/1

/

/

-25-BANANA THEORY

0-line

load

I

0-line

i.

load

I -..."7:---...- ... -... ....

fig 11

heave

static weight

moment

total cribbingload

UZ)

PETROBRAS

XIII

SYSTEMSHARE SHIPDESIGNPROGRAM TITLE

SEACAME1

SEMISU13

SEACAMEL 393 - 11

Y

PORT 4,:s svp

ilf.Eti

I I I 1 139 I

II

I I

--.

65 t7.-.3 I I 1 . I

! }

STARBOARD I I I I-21-I 1 I 1 ile I I

I'

I I I I I I 4_ 1 i _POR

X

'G.

STERN CATAMARAN TH 2500 BOW I I I i

_J

I I , 1 11 i 1 I L_ 1 _ll, I I I

- -

-r-_T 1 I 1 1 _.1 SKIDDING STARBOARD

ARRANGEMENT

I BOW

2 8

of Semisub (quarter)

I aiinrhinn of cemistih at Fhprhntirn

Plot of Seacamel barge (quarter)

//

/ /

'/

/

/

1

Transverse load distribution over skidbeam

Launching of semisub at Cherbourg

79 77 77 73 71

Deflection in mm.

30

fig 17

40

c.

6

74-C?

"Pe

s

Launching of semisub at Cherbourg

/

.

/

/

/

/

/

/

1/

/

II

frame 18 and 11 are bulkheads longitudinal bulkhead

/

/

/

longitudinal bulkhead longitudinal bulkhead

centre line SEACAMEL

1 2 v 3 I, 4

TV

5 6 1 7 1 9 10

-31

f ig

.

/4A

SK1DBEAM BULKHEAD SHIPS FRAME RIGBOTTOM J SHIP'S MA1NOECK

Jack Up dcuble transport on 9 ft cribbing

fig. 19

ROWAN ANCHORAGE

PATTERN OF FIXED

PILLARS ON DECK

ROWAN NEW ORLEANS

'Jack Up double transport on 9 ft cribbing

4

13

TRIM

(m)

1

-32-SUBMERGED STABILITY AND TRIM.

fig 20

Jack Up double transport on 9 ft cribbin

1

7

6

5

4

3

2

INTERNATIONAL MARITIME ORGANIZATION

Jr. W.A.Th. Bik

Nedlloyd Rederi,j Diensten,

_Rotterdam

3 3

3 4

-INTERNATIONAL MARITIME ORGANISATION

by Ir. W.A.Th.Bik

Dep Chief Naval Architect Nedlloyd Rederii Diensten

Summary

lull 1. 1986 the new amendments on the S.O.L.A.S.-convention

entered into force Especially the rules with respect to life-saving

on board of foreign-going ships are of great importance.After

reviewing the history of the S.O.L.A.S convention the most

important changes will be discussed

In several cases the author gives his personnal opinion and recommendations

Safety Of Life At Sea. 1986

Collisions accidents with ships are sometimes attractive heroic or dramatic. We all remember the stories, written in the youth books. we read with red ears The truth however, is horrible

Before reviewing the rules regulations and requirements we want first quote a testimony of Ronald Stewart Duncan Master Mariner of the Seafarth Highlander"This vessel was a stand-by

vessel of the semi-submersible Oce.u2 Ranger, which capsized on

februari 15. 1952.

The complement of 54 died with this disaster. Re testified

'At that time 0105 hours on 15 Februari, and almost immediately at that time we observed small lights in the water approximately four, live points on the starboard bow, and we

sighted a red distress flare approximately four points on the

starboard how at the same time I proceeded towards the red distress

flare and while proceeding to it another flare from the same source went up Probably about three minutes after sighting the

first flare we visually sighted a lifeboat which at first appeared to he in good shape riding high on the water. and I manoeuvred my ship very close downwind of the lifeboat, The lifeboat was under power because he steamed across a swell. across my stern from

starboard side to port side, and he manoeuvred his lifeboat down the port side of my vessel on to the port quarter (figure 1)

Duncan stated that the swells exceeded 60 feet and there were I5-foot breaking waves. The lifeboat came alongside us. and my men who by this time had gone out on the deck threw lines with

liferings attached One line was made fast on the lifeboat and

another ring was made fast to my ship Then some men began to come out of the enclosed boat and they stood on the portside of the

lifeboat which was the side away from my vessel - four orfive, maybe six men came out

Sometimes the lifeboat was iust touching the Seaforth Highlander but not especially violently At other times she was six

feet off the Seaforth !Leh/ander She was moving in and out a little

It was at that time that the lifeboat began to capsize to port in a

very slow manner, like watching a slow motion picture The men standing on top of the boat were thrown into the sea.

I could see what I estimate to be eight or nine men clinging

to the boat in the water I could see all these men They had

lifejackets

At about this tame I was taking heavy seas in the after deckof my

vessel which was stern to wind and sea The mate and one of the

seamen were washed up on the deck, but they were both okay

although they suffered some bruising The gangway net was

washed over the side We were still along the lifeboat, and after

maybe a minute and half or two minutes - it is verydifficult to estimate - the men clinging to the boat began to let go, and they drifted down my port side At that point I shouted down to my mate on the deck via the load hailer system to throw over a liferaft

I saw the men running up forward on my deck to go for the

liferaft and they threw a liferaft over the side which inflated

right beside the men in the water No effort was made by any men

in the water to grab hold of the liferaft No apparent effort was made by any men in the water to reach the lines which my men had been throwing to them after the lifeboatcapsized

I saw a lifering with line attached landing close to the men clinging to the boat and they didn t make any effort to reach the lifering At this time there were some men drifting down my portside. but the lifeboat was still off the port quarter of the ship

with two or three men clinging to it It was close to my port

propellor at this time so 1 had to stop my port propellor in case the men got caught in it

-35-Figure I The Seaforth Highlander approached a lifeboat of the Ocean Ranger and subsequently manoeuvred to assist

At that time the Seaforth Highlander was forced off the location by the heavy seas, and could not longer maintain our

position alongside the men in the water or the lifeboat Once we were clear of all the men I was able to use the port propellor again, and I manoeuvred the ship back around to an upwind position from the lifeboat and steamed down close to the lifeboat, the men and the lifejackets in the water There was no sign of life at all We could see all the men floating with there heads under the water, some of them with their arms outstretched, no sign of life, and the men on deck were trying to pick up bodies We couldn't get close to any of the bodies It was very difficult We were washing the bodies away

with the motion of the ship, and for the rest of that morning we

kept searching thet area for any live personnel which might have been found

84 people died with this accident

A second example

In spring 1956 the Russian passengerliner MichailLermentoll

sank after hitting undersea rocks on the South Island coast of New Zealand "35 people survived, I died The Russian pressbureau lass glorified the behaviour of the crew "Off reason the cool-blooded

action of the well-trained crew a bigger disaster could be

prohibited

Question is a good training in safety practises of a shipscrew a

newspaper topic or should this be normal

In 1983, after many years of negotiations and numerous

compromises. the International Maritime organisation ( IMO ) produced a new set of regulations to govern the standard and scale of life-saving appliances to be carried on foreign going merchant ships These newly, agreed requirements will apply in full to new ships as from 1 July- 1986. and in case of existing ships, they will apply in part on 1 July 1986, and slightly more extensively five

years later Why these requirements ?

Short history of Solas.

The first reasons for establishing safety requirements is the

destruction of the unsinkable Titanic in 1912 Till that moment no rule nor requirement in the field of safety for ships existed Means for life-saving was a favor of the shipowner.

Reviewing the design history of the TiaIk we see the number of lifeboats decreasing Finally. 20% of the life boats left compared

with the originally designed number Regulary. boats_{were crossed} out the ship was unsinkable wasn't she

We all know the final result

Solas 1914

This disaster raised so many questions about maritime safety that the UT -government decided to hold an international conference to discuss new safety regulations This conference held in London was attended by representatives from 13 countriesand the Solas - Safety Of Life At Sea - was adopted on 20 januari 1914

-36-It introduced new international requirements dealing with

the safety of navigation for all merchant ships, the provision of

watertight and fire-resistant bulkheads. life-saving appliances and fire prevention and firefighting appliances on passengerships. A

straight derivation from the Tiamie-disaster is the obligation to

carry a radiotelegraph and listen to it

The convention was to enter into force in July 1915

Solas 1929

The second Solas convention was again held in London in

1929 and adopted by IS countries This convention was a

refinement of the first Solas conference

Solas 1948

By 1948 the 1929 convention had been overtaken by

technical developments Again this convention took place in

London and followed the already established pattern but covered a wider range of ships and went into considerably greater detail. Important improvements were made in such matters as watertight

subdivision in passenger ships, stability standards, the maintenance of essential services in emergencies and structural fire protection. The Collision Regulations were also revised.

The International Safety Equipment Certificate was

introduced A seperate chapter was included dealing with the carriage of grain and dangerous goods

The year 1948 was particularly significant because a

conference held in Geneva under the auspices of the United Nations adopted a convention establishing IMCO

-Intergovernmental Maritime Consultative Organisation

The 1948 Solas convention recognized that the creation of

this new organisation would, for the first time, mean that there was a permanent international body capable of adopting

legislation on all matiars to maritime safety

It was originally intended that the convention would be kept up to dale by periodic amendments adopted under the auspices of IMCO but in the event it took so long to secure the ratifications required to bring the IMCO convention into force that rather than amend the 1948 convention it would be better to adopt a completely new instrument - the fourth Silas convention

Solas 1960

The 1960 Silas conference, which was attended by delegates

from 55 countries. 21 more than the 1948 one, was the first

conference to be held by IMO - International Maritime Organisation

The pace of technical change was that quick that the 1960

convention should adapt the numerous technical improvements

Like its predecessor, the new convention incorporated control

provisions including requirements for various surveys and

certificates for cargo ships of 500 gt and above making international voyages and for a government to investigate

casualties when " it judges that such an investigation may assist in

determining what changes in the present future might be

desirable ' and to supply 11,,I0 with pertinent information

Many safety measures which had once applied only to passenger ships were extended to cargo ships, notably those

dealing with emergency power and lighting and fire protection The radio requirements were again revised and in the chapter dealing with life-saving appliances provision was made for the carriage of liferafts which had developed to such an extent that

they could be regarded as a partial substitute for lifeboats in some

cases Regulations dealing with construction and fire protection

were revised as were the rules dealing with the carriage of grain

and dangerous goods The final chapter contained outline requirements for nuclear-powered ships which seemed to become

very important in the coming future As in 1929 and in 1948

revised Collision Regulations were annexed to the convention Finally, the conference adopted some 55 resolutions, many of which called upon IMO to undertake studies collect and disseminate

information or take other action These included, for example, a

request that IMO develop an unified international code dealing with the carriage of dangerous goods, a resolution which resulted

in the adoption five years later of the International Maritime

Dangerous Goods Code

The 1960 Silas conference was to determine much of IM0's technical work for the next few years It was originally intended

that the 1960 convention would be kept up to date by means of

amendments adopted as and when it entered into force in 1965 The

first set of amendments was adapted in 1966 and from then

amendments were adopted regularly

1966 amendments to chapter II, dealing with special fire safety measures for passenger ships

1967 six amendments adopted dealing with fire safety

measures and arrangements for life-saving appliances on certain

tankers and cargo ships, vhf radiotelephony in areas of high

traffic density: novel types of craft, and the repair, modification and outfitting of ships

1968 new requirements introduced into Chapter V dealing with shipborne navigational equipment, the use of automatic pilot

and the carriage of nautical publications.

1969 various amendments adopted, dealing with such

matters as firemen's outfits and personal equipment in cargo ships, specifications for lifebuoys and lifejackets radio installations and shipborne navigational equipment

1971 regulations amended concerning radiotelegraphy and radiotelephony and routting of ships

1973 regulations concerning life-saving appliances, radiotelegraph watches pilot ladders and hoists The major

amendment was a complete revision of Chapter VI which deals with

the carriage of grain Unfortunately it became increasingly

apparent as the years went by that these efforts to keep theSolas

convention on line with technical developments were doomed to failure - because of the nature of the amendment procedure

adopted at the 1960 conference This procedure required that amendments would enter into force twelve months after being accepted by two-third of Contracting Parties to the parent convention

-37-most international treaties were ratified by a relatively small

number of countries But during the 1960s the membership of the United Nations and international organisations such as IMO was

growing rapidly More and more countries had secured their independence and many of them soon began to build up their

merchant fleets The number of parties grew steadily This meant

that the number of ratifications required to meet the two-thirds

target required to secure entry into force of Solas amendments also increased It became clear that it would take many years - too many years - before these amendments became international law

As a result IMO decided to introduce a new Solas convention which would not only incorporate all the amendments previous

adopted to the 1960 convention but would also include a new

amendment procedure which would enable future amendments to be brought into force within an acceptable period of time

Solas 1974

The 1974 Solas conference was held in London from 21

october to 1 november and was attended by 71 countries

The convention which was adopted is the version currently in force

Article VIII included the new amendment procedure that amendments would enter into force by acceptation of 25 % of the Contracting Parties, representing 50 % gt of the world merchant shipping.

This Chapter went into force on 25 May 1986.

In the mean time a series of accidents involving oil tankers

in the winter 1976-77 led to increasing pressure for further

international action As a result, early in 1978 IMO convened an

international conference on tanker safety and pollution

prevention which adopted a number of important modifications to Solas as well to the International Convention for the Prevention of

Pollution from ships ( MARPOL ) 1973.

Since the 1974 Solas convention had not entered into force it was impossible to amend the convention Instead the conference decided to adopt a Protocol which would enter into force six month

after ratification by 15 States with 50 % of world tonnage of

merchant ships The Protocol entered into force on 1 May 1981 Solas 1974 already has been amended several times The first amendments were adopted in November 1951 and under the tacit acceptance procedure, entered into force on 1 September 1954

The most important of these concerns Chapter II-1

(Subdivision and Stability, machinery and electric installations) and Chapter 11-2 (Construction, fire protection fire detection and

fire extinction) In both cases the Chapters have been rewritten

and updated Several other Chapters have been adapted

The second set of amendments to the Solas convention were adopted in November 1953 and entered into force on 1 _lull 1956

They include a few editorial changes of Chapter 11-1 and some

further revisions of Chapter 11-2

Chapter III of the 1974 convention which deals with

life-saving appliances and arrangements is basically the same as that of the 1960 convention but the 1953 amendments amount to a

complete revision

As this article shows, the Solas convention is continually evolving IMO is currently engaged in developing what is termed

the Future Global Maritime Distress and Safety System (FGMDSS), a system which will take full adventage of the technological

developments of recent years in the communications field, notably the introduction of satellite technology

In 1986 IMO will convene a conference to consider the

harmonization of survey and certification requirements of the Load Lines and Soles conventions

It is unlikely however, that further amendments will be

adopted in the near future Under Resolution A 500(XID adopted in

1951, the IMO Assembly effectively called for a slowing-down of the

activities as far as the adoption of new legislation is concerned and

a greater concentration on the implementation of existing

instruments.

Highlights of the revised Chapter III Life-saving appliances and arrangements

The revised rules deals with all cargo ships, however the

Administration may exempt from those requirements individual ships which, in the course of their voyage, do not proceed more than 20 miles from the nearest land

Passenger ships have exemptions too

The major danger facing a sailor who has to abondon ship is the risc of death due to hypothermia.

Hypothermia is a condition which arises as the internal

temperature of the body, usually referred to as the body core temperature is reduced, a critical stage being normally reached when the core temperature falls more than 2 C below normal

( the excitation state )

If the temperature continues to fall below 35 C the person affected will suffer from Yarling degrees of disability, leading eventually to

death

Even with a very carefully medical check it is hardly impossible to determin if the victom is deeply unconscious or death Only with an E.0 Gan irregular heart rhytme can be detected

Approximate Time Scale for Survivors of A ee Body Built

Table 1

The body is chilled when subjected to external low temperatures and this chilling occurs 25 times more rapidly immersed in water

than in air

Temp.of Water Unclothed Clothed

o' c Survivor remains able for 1 hour 2 / 10 min

5' C I hour 20 / 30 min

C 3 hours I hour

15 C 5 hours 3 hours