Schip en W e rf - Officieel orgaan van
de Nederlandse Vereniging van Technici op
Scheepvaartgebied
De Centrale Bond van Scheepsbouwmees­
ters in Nederland CEBOSINE
Het Maritiem Research Instituut Nederland
MARIN.
Verschijnt vrijdags om de 14 dagen
TIJDSCHRIFT VOOR
MARmDHE-EM OFFSHORETECHHIEK
SCHIP EN WERF
Redactie
Ir. J. N. Joustra, P. A. Luikenaar,
Dr. ir. K. J. Saurwalt en Ing. C. Dam
Redactie-adres
Heem raad ssingel 193,
3023 CB Rotterdam
telefoon 010-4762333
ICMES '87
Voor advertenties, abonnementen
en losse num m ers
Uitgevers W yt & Zonen b.v.
Pieter de Hoochweg 11 I
3024 BG Rotterdam
Postbus 268, 3000 AG Rotterdam
telefoon 010-4762566*
telefax 010-4762315
telex 21403
postgiro 58458
Abonnementen
jaarabonnement 1987
ƒ 78,25
buiten Nederland
ƒ 124,50
losse nummers
ƒ 5,55
(alle prijzen incl. BTW)
Bij correspondentie inzake abonnementen
s.v.p. het 8-cijferige abonnementsnummer
vermelden. (Zie adreswikkel.)
Vormgeving en druk
Drukkerij W yt & Zonen b.v.
ISSN 0036 - 6099
CtHï* ir7
P o lltie b o o t: gebouwd op Scheepswert De Hoop - Schiedam. Voorzien
van: 2 stuks MTU/MB OM 424 A mo­
toren van elk 350 KW.
'M TU, een Daitnler-Benz onderneming, produ­
ceert kompakte
dieselm otoren van
131 tot 7400 kW
(178 tot 10.064
pk) volgens de
laatste stand der
techniek, voor sta­
tionaire-, traktieen scheepstoepassing, alsmede
diesel- elektrische
aggregaten voor
land- en scheepsinstallaties; ook in
container uitvoe-
Meer dan 37.200 M TÜ-motoren zijn wereldwijd in gebruik,
waarvan meer dan 10.500 in de scheepvaart. Import: AG AM
MOTOREN ROTTERDAM B.V.
Inhoud
ICMES '87
387
The Medina project
389
Conoco ontwikkelt
V-gasvelden
395
Design aspects of
floating production
stations
400
Nieuwsberichten
407
Verenigingsnieuws
408
Application o f Technological Advances
H et vierde Symposium van de Internatio­
nal Cooperation on Marine Engineering
System (ICMES) vond van 9 to t en m et 11
september plaats in Malmö, de derde stad
van Zweden en de bakermat van de
scheepswerf Kockums A.B., die een niet
onaanzienlijk aandeel had in de organisatie
van d it symposium.
Malmö is ook de plaats waar de W o rld
Maritime University van de I.M.O., de In­
ternational Maritime Organisation van de
Verenigde Naties, sedert haar oprichting
in I983 is gevestigd.
H et symposium w erd om die reden dan
ook geopend door de Secretaris Generaal
van de I.M.O. mr. C. P. Srivastava. In zijn
openingsrede pleitte Srivastava vo or ken­
nisoverdracht op m aritiem gebied. De
I.M.O. is namelijk de grootste sponsor van
de W o rld Maritime University, een oplei­
dingsinstituut voor scheepvaart manage­
ment op nautisch, technisch en administra­
tie f gebied voor studenten uit opkomende
maritieme naties (ontwikkelingslanden)
m et als doel het bevorderen van de invoe­
ring der I. M.O. resoluties op het gebied van
maritieme veiligheid en milieu.
Een 40-tal studenten en docenten van deze
Universiteit nam ook deel aan d it symposi­
um. De voornaamste deelnemers, totaal
102, kwamen uit 17 landen, voornamelijk
Westeuropese, doch ook deelnemers uit
China, Egypte en Israël luisterden m et veel
interesse naar de 31 voordrachten die
door sprekers afkomstig uit 11 verschillen­
de landen, wederom voornamelijk W e st­
europese, werden gehouden.
Inhoud van h e t Sym posium
De ICMES-organisatie bestaat u it een
commissie van 7 leden onder v o o rz itte r­
schap van de Fransman G. C. Volcy, een bij
velen bekende engineering surveyor
superintendent van Bureau Veritas. V oor
Nederland maakt ir. A. de Mooy van T N O IW ECO als lid deel u it van deze commissie.
Iedere drie jaar organiseert ICMES een
SenW 54STE IAAR G AN G NR 20
symposium dat is gebaseerd op de resulta­
ten van in totaal 9 werkgroepen (Technical
comittees) die de volgende onderwerpen
op het gebied van Marine Engineering be­
handelen:
- Reliability and Maintainability.
- Energy and Manpower Saving Systems.
- C ontrol Engineering.
- Noise on board Ships.
- Shafting System Dynamics and Interac­
tions w ith the Ship.
- Interaction between Diesel Engine and
the Ship.
- Interaction between Gearings and C ou­
plings and the Ship.
- Operation and Maintenance o f the Ship.
- Integrated Ship Systems: Design, O pe­
ration and Personnel Training.
In vijf sessions werden 3 1 voordrachten,
afkomstig uit de diverse werkgroepen, ge­
presenteerd. Een voordracht over 'Marine
Technology, a Time fo r Change’ vormde
de inleiding to t een bijzonder interessante
paneldiscussie over de toekom st van Mari­
ne Engineering. Van de 3 1 lezingen werden
er vijf door Nederland gebracht waardoor
ons aandeel in d it symposium w eer goed
to t uiting kwam.
Ir. R. K. Hansen van Nedlloyd hield een
inleiding over de voorstuwingsinstallatie
van de nieuwe veerboten voor N o rth Sea
Ferries.
Ir. B. W . jaspers van T N O -IW E C O hield
een inleiding over de technische conse­
quenties van de verminderde bemanning.
Ing. R. U iterm arkt en ir. P. Kloppenburg
van Techno Diagnosis verzorgden beiden
een inleiding op het gebied van Condition
Monitoring en Onderhoudsvoorspelling.
En als laatste hield de heer H. F. Steenhoek
van T N O -T P D een voordracht over de
voortgang van de Geluidsbeheersing in
Scheepsvoortstuwingsinstallaties.
Uiteraard had Zweden een g ro o t aandeel
in de presentaties die op een hoog peil
stonden waar theorie en praktijk elkaar
goed aanvulden.
387
H et Duitse aandeel in de presentaties
w erd voornamelijk geleverd door Profes­
sor G. Grossmann van de Technische Universiteit in Berlijn. M et zijn medestanders
en volgelingen verzorgde hij een aantal
inleidingen over de technische installaties
van het 'Schiff der Z uku nft’.
H et Britse aandeel in de voordrachten was
afkomstig van de University o f Newcastle
upon Tyne en van British Shipbuilders.
O o k de Volksrepubliek China liet zich op
d it symposium horen m et een viertal voor­
drachten over torsietrillingen.
Enkele slo to p m erkingen
De stemming op d it symposium was niet
pessimistisch vo o r wat b etreft de to e ­
komst van de marine engineering in W estEuropa. Al in de paneldiscussie aan het
begin van het symposium kwam naar voren
dat in W est-Europa voldoende kennis en
'high tech’ aanwezig is om een belangrijk
marktaandeel te behouden in de leveran­
ties van m aritiem technische installaties aan
de wereldscheepsbouw. V o o r ons land
kunnen dan als voorbeeld worden ge­
noemd, Lips, Hydraudyne, I.H.C. en de
elektrotechnische bedrijven. O o k het aan­
deel van onze onderzoeksinstituten in de
wereld van de hydrodynamica en m aritie­
me technologie mag enige naam hebben.
Waar w ij in Nederland voor moeten vech­
ten is de instandhouding van de driehoek
Onderwijs, O nderzoek en Industrie, waar­
bij de Industrie als basis onmisbaar is voor
Onderwijs en O nderzoek (Research and
Development).
O p d it symposium heeft Nederland ge­
toond nog steeds volop actief te zijn, waar­
bij niet zonder tro ts mag worden vermeld
dat nagenoeg alle dertien Nederlandse
deelnemers lid zijn van onze Vereniging en
alle Nederlandse presentaties verzorgd
werden door leden van onze N.V.T.S.
Het Gemeentebestuur van Malmö heeft
zich een uitstekend gastheer getoond d oo r
de beschikbaarstelling van de conferentie­
zaal in het St. G ertrudcentrum en de Guildhall voor een stijlvol banket vo or de deel­
nemers en de hen vergezellende dames.
In Malmö was de reden vo or een o ptim isti­
sche toekom st niet ongegrond. M et enige
tro ts maakte de directie van Kockums A.B.
de ontvangst bekend van een opdracht
vo or de bouw van zes onderzeeboten voor
de Australische Marine. Hiermee was de
werkgelegenheid van de 700 werknemers
van Kockums A.B. voor enige jaren verze­
kerd.
Tenslotte w erd het voorzitterschap van
ICMES d oo r de heer Volcy (vo o rzitte r
sedert de oprichting) overgedragen aan de
heer Nils Dellgren, de organisator van dit
zeer geslaagde symposium.
P. A. L.
388
25 Fault D etection
Appendix, Tables and Index.
N ieuw e uitgaven
M A R IN E R E F R IG E R A T IO N
MANUAL
by Capt. A. W . C. Alders.
Price: US $ 6 5 .- + postage US $ 3.50 per
copy.
The book is available from : Rotterdam
Marine Chartering Agents. RMCA Mod­
erato I. 2925 BL Krimpen a/d IJssei.
Netherlands. Tel. 01807-19730.
O ver the past decades both refrigeration
engineering and the carriage o f refriger­
ated products have shown tremendous
developments. Obviously, a great need
arose fo r knowledge o f this area both
amongst nautical and engineering staff on
board refrigerated vessels and amongst all
those ashore whose jobs involve dealing
w ith refrigerated and frozen produce.
This book was originally published in the
Dutch language and immediately received
wide acclaim. In his treatm ent o f aspects
relating to specific cooling techniques,
Captain Alders shows that he has research­
ed his subjects deeply and this explains the
inclusion o f the latest techniques used in
this field.
The result is a well-presented book o f
some 250 pages w ith the follow ing con­
tents:
1 The Refrigeration Plant
2 Theory o f Thermodynamics
3 A ir Circulation
4 Insulating Materials
5 The Insulation o f the Refrigerated
Hold
6 The Installation and the Refrigerant
7 Acids, Salts, Bases and pH
8 The Condenser and the Evaporator
9 The Thermostatic Expansion Valve
10 Defrosting and Leak D etection
11 C onstruction o f the Installation
12 Compressors
13 Containerisation in Reefer Shipping
14 The Design o f a Modern Reefer C on­
tainer Ship
15 Cooling and Freezing in the Fisheries
Sector
16 Receipt and Carriage o f the Cargo
17 General Guidelines fo r Transport o f
Refrigerated Cargoes
18 Mechanical Freezing o f Foodstuffs
19 Carrying Conditions fo r Animal
Products
20 Carrying Conditions fo r Fruits and
Vegetables
21 Particular Requirements fo r Individual
Fruits
22 The PE Diagram
23 Total load on the Refrigeration Plant
24 Electronic C on trol o f The Refrigera­
tion Plant
The book is recommend to all those w o rk ­
ing in the wide field o f refrigeration such as
owners o f refrigerated vessels and their
officers, shippers o f refrigerated and
frozen cargoes, reefer brokers, technicians
o f coldstores and shipyardsand, last but not
least, students attending technical and
nautical colleges.
T y p e approved M aterials
and E q u ip m en t
Bureau Veritas has published a booklet
listing every certificate o f approval for
materials and equipment relating to
Machinery and Piping Systems delivered
until A pril 1987. This booklet supersedes
the one published in February 1986.
This booklet entitled 'Type approved
materials and equipment — machinery and
piping systems’ is divided in tw o parts, the
first one related to products approved fo r a
general application, the second one related
to products approved fo r a specific applica­
tion. These tw o parts are themselves di­
vided in several chapters as follows:
- p art I: General applications
1. Miscellaneous machinery & piping
materials o r equipment.
2. Internal combustion engines, turbines &
accessories.
3. Reduction & step-up gears, clutches.
4. Propellers, thrusters, shafting assemb­
lies, shaft couplings, shaft bearings &
propeller shaft sealing glands.
5. Fire boilers, incinerators, pressure ves­
sels, heat exchangers & accessories.
6. Pumps, compressors, fans & blowers.
7. Pipes, pipe connections, gaskets, ex­
pansion joints, bellows & hoses.
8. Valves, valve actuation devices & safety
piping devices.
9. Istrumentation.
1.
2.
3.
Part II: Specific Applications
Refrigerating plants.
Prevention against sea pollution.
Equipment o th e r than electrical ones
fo r use w ithin hazardous areas.
4. Cargo process equipment fo r oil / pro­
duct / chemical tankers.
5. Cargo process equipment fo r liquefied
gas carriers.
6. Special equipment fo r offshore, diving
o r submarines.
It refers to about 800 products manufac­
tured by about 360 Manufacturers around
the w orld.
This booklet is one o f the series covering all
Marine and Offshore materials and equip­
ment eligible to the Society’s Type
Approved and C ertification scheme
(TYPEC scheme). It is available on request
at: Bureau Veritas, Coolsingel 75, 3012 A D
Rotterdam.
SenW 54STE 1AARGANG N R 20
THE MEDINA PROJECT
5y Ch. van der Z w e e p * and E. David Stogdon M B E **
In tro d u c tio n
When the chairman o f the KNZHRM , Mr.
J. F. Dudok van Heel, together w ith the
Dutch author o f this article, paid a visit to
the RNLI in September 1980 and were
given the o pportunity to make a trial run in
the first Medina (O .N . 1069) 'M ountbatten
of Burma’, they were, like many others,
favourably impressed by the concept o f this
type o f boat.
The 'Mountbatten o f Burma’, driven by
twin inboard diesel engines coupled to
Stern Powr outdrive units, has a draught of
1.14 m, while the draught o f the Medina
hull is only 0.68 m. Since the KN ZH R M
would soon be needing a boat w ith a
draught o f circa 0.70 m, capable o f operat­
ing in deep and shallow coastal waters,
which would replace a number of afloat and
carriage-launched beach lifeboats, it was
thought that a Medina w ith w ater-jet
propulsion might be suitable.
Because o f the depth o f expertise and
experience concentrated in the RNLI, the
KNZHRM - instead o f starting develop­
ment itself - enquired if the RNLI would
consider the development o f a w ater-jet
driven Medina w ith financial participation
by the KNZHRM. This development and
the proposed participation were accepted
and an informal Memorandum o f Under­
standing was drawn up and signed in
November 19 8 1. As a result, the director
of the KN ZH R M joined the RNLI Medina
working party which remained the deci­
sion-making authority, and in 1983 the
Medina O .N . 1091 was produced w ith
water-jet propulsion.
Meanwhile our sister-institution in R otter­
dam, the KZHMRS, also very enthusiastic
about the exceptional sea-keeping qual­
ities and speed o f the first Medina, decided
in 1982 to design and build its own Medina.
This resulted in the P.P. w ater-je t driven
’Koningin Beatrix’, commissioned in A pril
1984 by her Majesty Queen Beatrix.
W ith the information and experience
gained since 1980, the KN ZH R M decided
at the end o f 1984 to start its own project
pursuing a line o f development to embody
the lessons learnt. The aim was to design a
next generation Medina w ith an enclosed
wheelhouse (to give crew and survivor
protection and to provide full self-righting
capability) and w ith duplicated control
from an open bridge.
The ’Bureau voor Scheepsbouw W illem de
Vries Lentsch’ was contracted to design
the boat and to produce all the necessary
drawings, assisted by an advisory team of
the KNZHRM.
W e are very fortunate that Mr. E. D. Stog­
don MBE, RNVR - ex-superintendent of
the RNLI’s Cowes Base, Staff Project
O fficer o f the Medina I (O .N . 1069) and
one o f the pioneers in the Rigid Hull Inflat­
able Boat (RHI) concept, w ho served as an
advisor/consultant on the building team o f
the ’Koningin Beatrix’ - was also willing to
join our team.
R equirem ents
Some o f the most essential requirements
were:
- The boat to lie afloat and to have the
ability to be launched and recovered by
means of a carriage o ff a gently sloping
sandy beach; the fo rm e r being the more
im portant initial requirement.
- A crew o f four, but should be capable of
being operated by a crew o f three, and at
night as well as in daylight hours.
- Aluminium construction.
A deadrise o f approximately 26° in con­
junction w ith a 3 Vi° to 3^*° dynamic
trim .
The boat to be divided into 5 w atertight
compartments; forepeak, middle com­
partment, each engine in a separate com­
partment, aft compartm ent w ith je t units.
- An endurance o f six hours running at full
speed - range 150 nautical miles. Fuel
capacity; 2 x 600 litres.
- Propulsion by tw in inboard diesel en­
gines coupled to KaMeWa w aterjet units
w ith o u t reverse gear, to give a speed o f at
least 27 Vi knots. This speed is based on the
maximum wavespeed in the N o rth Sea of
24 knots (In deep water).
The horsepower required to provide a top
speed o f over 27 knots is the minimum
pow er necessary to give a choice o f posi­
tion when running in unstable sea condi­
tions.
The KaMeWa type 40 S 62/6 w ater-jet
units w ere chosen on account o f the shape
and position o f the ’bucket’, and o f the
construction in stainless steel.
A complaint about the existing Medinas
Fig. 2. 13.3 m 3 zero static trim , wedge 2 ° andspray-scrip, speed 28.3 kn„ dynamic trim
3.6°
* Director KNZHRM.
** RNVR.
SenW S4STE IA AR G AN G NR 20
389
Fig. I. General Arrangement
390
SenW 54STE IA A R G A N G NR 20
with water-jets is the low astern power.
Our opinion is that the KaMeWa units,
whereby the astern thrust is achieved by a
reversing ’bucket’ in the steering nozzle,
may overcome this as the ’bucket’ is gra­
dually introduced into the jetstream redi­
recting it downward and forw ard thus pro­
viding more effective stern power.
The stainless steel construction was
chosen fo r its sturdiness and reliability, but
in particular fo r its effective resistance
against attack by sandladen water.
This choice means however that we have
to pay the penalty fo r the heavy weight
involved.
- The diesel engines to be mounted side
by side and forw ard o f the wheelhouse.
We considered that the side by side posi­
tion w ith the weight localised about the
LCG is preferable to the staggered installa­
tion used in o the r Medinas (where the
weight is distributed along the length o f the
boat), because the weight concentration
about the LCG reduces the longitudinal
radius o f gyration.
Having the wheelhouse aft o f the engines
gives adequate height fo r engine mainte­
nance and fo r m inor repair facility at sea.
Also engine replacement is easier, tem per­
ature in the wheelhouse is reduced and a
better noise insulation can be achieved.
- A closed cooling system fo r the engines
to avoid sand blocking the cooling pipes
when operating in shallow sandy areas.
The hull was to o small however to allow a
sufficient cooling surface fo r the required
H.P. This led to the choice o f air-cooled
engines: Deutz BF I2L 513, 480 PK/353
Kw ( 15 min.), 454 PK/334 Kw (cont.). This
choice necessitates large air intakes (tw ice
100 x 40 cm) and even larger outlets (tw ice
80 x 80 cm).
W e are not unduly w orried if some w ater
gets inside, because adequate watertraps
and the bilge suction pumps can handle it.
The openings are closed by valves in the
event o f a capsize and as they are only under
water fo r a short time, the amount o f
water that gets inside (if any) w ill be man­
ageable and o f little concern.
- Buoyancy tube, diameter 80-82 cm,
material Kleber, full Kevlar 6758. A coun­
te r stern (pinky stern) w ith the buoyancy
tube continued around the transom to
provide greater lift in this area. This con­
figuration improves the boat’s perform ­
ance in open sea conditions w ith following
seas, makes slow running safer when escor­
ting boats before a sea, and helps to pre­
vent pooping and keeps the boat dry.
The tube w ill be subdivided into 10 com­
partments w ith recessed valves fo r air in­
flation. Each compartm ent w ill have w ithin
it a rolled up tube made o f lighter material.
This inner tube can be blown up through its
own separate inflation valve in case o f
damage to the o ute r tube.
In order to save weight, glue and not
mechanical means w ill be used to attach the
SenW 54STE IA AR G AN G NR 20
tube to the gunwale and inboard side of the
saddle. The tube w ill be constructed by
Float Sassenheim.
- Enclosed w atertight wheelhouse to
provide a positive righting capability and an
external steering position.
When a lifeboat is fitte d w ith an enclosed
wheelhouse we consider an additional ex­
ternal steering position a necessity. It gives
the helmsman/coxswain much better
visibility and hearing, when crossing a bar
or in the search area, as well as the
opportunity to communicate w ith the
crew on deck, when near the casualty. This
is particularly im portant during operations
at night and in low visibility conditions such
as fog and rain.
• Windows
Forward
windows
w ith
layered,
toughened glass; 15 m m o u ts id e -2 m m fo il
w ith heating element - 5 mm inside. Side
windows double glazed (to check conden­
sation) w ith polycarbonate Makrolon; 8
mm outside - 6 mm inside.
Length overall (m)
Length o f rigid hull (m)
C W L (m)
Beam overall (m)
Beam o f rigid hull (m)
Draught (m)
Displacement (m 3)
- Navstar 6 0 1D Navigator.
- VHF radiotelephones: 2 S.P. Radio
Sailor Multi-Remote sets, type RT-146.
- VHF/DF: Skipper/Taiyo, type T D L1520 RDF.
• Recovery o f survivors in the w ater by
helicopter strop used from an RNLI-type
A-frame mounted on the p o rt side o f the
wheelhouse.
Lines
W hile drawing the lines based on these
requirements it soon became apparent
that the boat would have to be bigger and
beamier than its predecessors and that
much more horse pow er than the original­
ly planned total o f 2 x 355 PK would be
needed, so the extra horse pow er o f the
chosen Deutz air-cooled engines was a
welcome bonus.
The most im portant main dimension was
the beam required to accommodate the
tw in diesel engines side by side and each in a
w atertight compartment. (See Appendix)
This led to the following principal dimen­
sions:
Prototype
lifeboat
Medina
Kon. Beatrix
14.39
13.65
11.13
5.39
4.20
0.75
13.5
12.04
10.51
9.50
4.35
3.45
0.68
9.2
12.70
11.25
10.05
4.70
3.90
0.63
8.9
• Seating
The four crew are seated in the wheelhouse, each w ith a view forw ard, on Atlan­
tic 21 type saddle seats w ith safety belts;
one saddle seat in the open bridge. W e
consider the saddle seat the best answer,
because it is firm and one cannot ’b o tto m ’
on it. By pressing one’s knees and legs
against the pedestal, like riding a horse, and
by using footstraps, a b e tte r balance can be
kept than by sitting in a (sprung) chair.
M oreover chairs are cumbersome and p ro­
ne to buckle in heavy seas.
Additionally, fo r survivors, there are four
body-moulded seats w ith safety-belts as
made by Messrs. Verhoef Aluminium In­
dustrie fo r th eir freefall lifeboats.
• Maximum noise level to be between 75
and 80 dB.
• Electronic equipment
- electronic compass: I T. Holland, type 6
S, w ith daughter compass (and a magnetic
compass) on the open steering position.
- echosounders: Lowrance digital sound­
er, type 3200 M w ith repeater on the open
steering position; Lowrance graph recor­
der, type X-16.
- radar: Furuno.
- video plotter: Furuno, type GD-170.
W e rejected the possibility o f a softer
’strike’ area w ith a steeper section, fo r
safety, fo r the following reasons:
(1) the high thrust line of je t drive may
cause a deep V-shaped bow to 'dig in’ when
running at speed on the face o f a sea.
(2) when there is a possibility o f
broaching, jet steering does not provide
the immediate ’feel’ to counteract a swing.
As je t propulsion has no grip o f the w ater
aft, a deep V-shaped bow may more easily
dominate a broaching attitude.
A fte r careful calculation, having reduced
the weight as much as possible, the total
weight was 13.439 tonnes w ith 75% fuel
and 4 crew. W ith this figure, the lines o f the
boat, and w ith the pow er specified in the
design requirements, a com puter pre­
dicted the speed to be 27 - 27 Vi knots.
A t this stage it was decided, on account o f
the weight and dimensions o f the boat, to
pursue the lying afloat ability only and to
drop fo r the tim e being the requirement
that the boat also had to be launched from a
carriage.
T o w in g ta n k tests
Towing tank tests were carried o ut next in
A p ril 1986 at the D elft University by Pro­
fessor Ir. J. Gerritsm a (fig. 2). A 1:9 scale
391
one direction tend to have disadvantages in
others. In any case it might have been
necessary to have another series o f tank
tests w ith a modified model. As the after­
body wedges are only marginal, we de­
cided to leave the lines as they were.
model was tested at speeds varying be­
tween 14 and 30 knots and w ith the
displacements I 3.3 m 3and 14.3 m 3to m e a ­
sure resistance, running trim and heave
change. During the tests, as a result o f the
experiments, the hull form was fitte d w ith
an extra spray rail and small afterbody
wedges (2°, 0.05 L) to reduce the running
trim angle o f 4.8° to the required angle of
3.5° above zero static trim .
The results w ith a speed o f 27 knots were
as follows:
Selfrighting test
A fte r the tow ing tank tests the model was
fitted w ith an enclosed w atertigh t wheelhouse and scaled to the exact weight, w ith
the LCG and VCG in the co rrect positions,
V = 27 knots
cow-condition
8S degrees
Z, m
PE hp
V = 13.3 m3
0si = — 1 degree
5.8
0.23
485
4.0
0.17
565
4.1
0.18
510
3.7
0.23
470
3.9
0.26
505
V = 13.3 m3
0si = — 1 degree
wedge 2 degrees: 0.05 L
V = 13.3 m3
0« = — 1 degree
wedge 2 degrees: 0.05 L
extra spray-strips
V = 13.3 m3
0si = 0 degrees
wedge 2 degrees; 0.05 L
extra spray-strips
V = 14.3 m3
0 „ = 0 degrees
wedge 2 degrees; 0.05 L
extra spray-strips
0„ 0, V Z PE -
static trim
dynamic trim
displacement
heave
effective horse pow er
The combination o f a zero static trim , a
wedge o f 2 degrees and an extra spraystrip gave the best result: a dynamic trim o f
3.7 degrees, the lowest EHP and no pow er
hump.
W ith a speed o f 27 knots, a displacement o f
13.3 m 3 and a total p ow er yield o f 50% the
shaft horse pow er needed was determined
at 940 HP.
To provide the required dynamic trim of
3 '/z0 to 3% ° from the waterline, the
tank tests showed it was necessary to have
a static trim o f — 1° o r 0° trim plus
wedges.
A reduction in the fore-body volume was
considered. The possible increase o f deadrise o f stations 5, 6, 7 and 8, shortening the
parallel lines by a small amount, may have
provided the required dynamic trim w ith ­
out either a static bow -dow n trim o r
wedges.
It is difficult to know w hat o the r conse­
quences might evolve from changing the
lines however slightly: improvements in
392
to get an impression of its selfrighting
properties and its behaviour in the w ater
(fig 3 and fig. 4).
A calculated curve o f righting levers had
already indicated that all the righting arms
were positive and this was proved by the
model tests. The model righted w ithin 3
seconds. It also behaved perfectly when
pushed and th ro w n around in the water.
As a result o f these tests it was decided to
give the wheelhouse sides more rake
above the knuckle line and to ease the
radius to the wheelhouse top. This would
improve the vision from the open steering
position to the sides o f the boat and also
enhance the aesthetic appearance.
Tenders
In May 1986, three yards w ere invited to
send in th eir tenders based upon brief
specifications, the lines and preliminary
drawings prepared by De Vries Lentsch.
These yards had been preselected from
interested contractors and the project and
its requirements had been talked over.
A luboot B.V. at Hindeloopen, a yard which
had already built several lifeboats fo r the
Institution, won the contract. U nfortu­
nately, but known in advance, the yard
could not start building at once and finish
the boat before the X V th ILC in Spain (June
1987), due to earlier commitments.
The boat w ill however be ready in O c to ­
ber 1987, after which extensive assess­
ment trials w ill be held before she is turned
over to her allocated station at Ameland
fo r fu rthe r evaluation.
The total costs o f the boat, excluding the
costs fo r the design, the various tests and
the preparation o f the drawings, w ill be
approximately
Dfl. 1.100.000,—
(£ 343.750,-, US$ 489.000,-, using rates
o f exchange current on 5 Dec. 1986).
Building
Before the actual building o f the boat
started, a full scale mock-up o f the wheelhouse was made by the yard fo r evaluation
o f the space layout and equipment location.
The steering console and control instru­
Fig. 3.
SenW 54STE IA AR G AN G NR 20
ment panel, as well as the seating arrange­
ment o f the crew and the helmsman's posi­
tion were also established w ith the aid o f
this mock-up.
T ra in in g
Parallel w ith the development o f boats of
this type and size runs the necessity to train
their future crews. Handling a rigid hull
inflatable boat w ith water-jets, capable of
25-30 knots w ith fast acceleration and
manoeuvrability, calls fo r a high degree of
training.
As the new boat had been allocated early to
our station Ameland, the existing crew
was locally trained in handling various types
of RHIs w ith outboard engines and w ith
w ater-jet units.
In November 1986 those selected under­
went fu rthe r training at the Offshore
Survival School at Stonehaven, Scotland,
where all our crews fo r RHIs and fully
inflatable boats have had th e ir final training.
For this crew the usual course was adapted
and special emphasis was laid on handling
the boats driven by waterjets.
A P P E N D IX
Buoyancy condiderations in th e de­
sign o f rigid hull inflatables
When considering the design of larger
RHIs (over 10 m) it is im portant that the
function o f the buoyancy tube (described
below) is preserved, and not compromised
for the sake o f convenience o r appearance.
These functions are:
1. It provides a circle o r near circle o f
totally enclosed buoyancy in excess o f
the displacement o f the boat; the hull
being positioned below it.
Additional loading at deck level (e.g.
survivors) therefore does not seriously
affect stability.
2. It provides the stability o f a raft when
stopped, w ith o u t impairing the boat's
high speed performance.
3. It acts as an 'energy sink’ to absorb the
weight o f a heavy sea.
4. If the tube is designed w ith sufficient
volume and positioned correctly it
should minimize the possibility o f a
capsize.
Fig. 4.
side o f the boat is at least 65% o f the boat’s
displacement, it w ill minimize the possibil­
ity o f capsize when the boat is on its beam
ends, because the gunwale w ill have some
support which w ill allow the boat to side­
slip.
The total volume o f the buoyancy tube of
the N o rth Holland lifeboat is 15.9 m 3 and
the tube diameter would have to be in­
creased to 83.3 cm from its present dia­
m eter o f 80 cm to achieve a buoyancy on
one side of the boat which is equal to 65%
o f the boat’s displacement.
Stabilisation o f tube
The attachment of the buoyancy tube to
the gunwale and deck, by a 'saddle' helps to
stabilise the tube w itho ut reducing the
'energy sink’ properties.
The saddle’s arc o f attachment o f the
N o rth Holland lifeboat is 10.4% o f the
tube’s circumference, which strikes a ba-
Height o f bow
The rigid bow height above the waterline
and the volume o f buoyancy in the rigid
bow section must be sufficient to carry the
bow up the back o f a steep sea, w itho ut
allowing it to penetrate. The height and
volume o f the bow o f the N o rth Holland
lifeboat fits closely to the empirical pattern
of the associated height and volume o f the
RNLI Medinas and so far the Medinas have
not buried th e ir bow when running before
a sea.
W e hope that as the number and variety of
large RHIs increase it w ill be easier to
determine certain design parameters from
operational experience.
E. D. Stogdon
January 1987
1. Fortran 77
fo r main frame computers of the IBM/370
type and its successors, under VM/SP and
CMS.
N ieuw e uitgaven
Height o f tube
The height o f the bottom o f the tube from
the waterline is related to the rigid beam o f
the boat and the beam must be sufficient
for installation o f the engines and the
associated access space. Having established
the height o f the tube the after sections of
the hull can than be drawn to support it.
In the case o f the N o rth Holland lifeboat,
the height o f tube from the w ater is 38 cm
which matches the recommanded (R.A.
Chatfield, 19 8 1) height fo r this size of boat
(37.3 cm).
’G L Rules' c o m p u ter p ro g ram fo r
the construction o f steel hulls; n ew
edition
The latest version o f ’GL RULES’ compu­
te r program fo r the construction o f steel
hulls is now available from the classification
society, Germanischer Lloyd. The prog­
ram covers Volume I , chapter 2 o f Germa­
nischer Lloyd’s rules book, and includes the
latest changes, published in the Summer
1986 edition. Formulas are included fo r all
the significant sections o f chapter 2, and
some sections are covered more fully than
in the 1982 edition.
Volume o f tube
If the volume o f the buoyancy tube on one
The 'GL Rules' program is available in the
following versions:
SenW 54STE IAAR G AN G NR 20
lance between stabilising the tube, and
allowing it to roll and absorb energy.
2. Fortran 77
fo r personal computers o f the IBM/XT
type and its successors, under MS-DOS.
3. HP-Pascal
fo r HP desktop computers
4. HP-Basic
fo r desktop computers HP 9845 B
5. Fortran IV
subroutine package fo r integration into
other programs.
For fu rthe r information contact: Germanischer Lloyd, Research Department,
Hamburg. Tel.: Hamburg (040) 36 14 90.
393
V FIELD PARTNERSHIPS
Vulcan
Partners
SOUTHERN
BASIN
GAS
DEVELOPMENT
(estimated reserves : 1020 billion cu . ft.)
A CCOMMODATION P[ATFORM
Vulcan straddles blocks 49/21 and
Block 48/25b
48/25b and will be developed by
two unmanned satellite platforms
Conoco
(50%)
Britoil
(50%)
Block 49/21
Conoco
Vanguard
200 billion cu.
(37.5%)
Arco
(12.5%)
Marathon
(12.5%)
Occidental
(12.5%)
ft.)
Block 49/16
The Vanguard field lies in block
Conoco
(50%)
49/16 and will be developed by one
Britoil
(50%)
unmanned satellite platform
South Valiant
(estimated reserves : 180 billion cu.
South Valiant lies in block
H.C.G. Schiedam Netherlands
SCHEDULE
Fabrication started March '86
Fabrication complete Feb '88
COMPRISES:-
5 Decks plus helldcck and Includes a sauna,
gymnasium, cinema, recreation area, galley,
laundry, dining area, sick bay, cabins and
a communications module.
COMPLEMENT:
Maximum peak
125
Maximum operating 83
Normal operating
A?
LIFEBOATS:
DECK CRANE:
POWER GENERATION:
2 x 70 man
1 x 8t
2 x 600 kw units
CAN STORE
126 m t s 3 Diesel fuel
141 m t s 3 potable water
3 x 600 gallons he 11 fuel
CAN SUPPLY
Sea water at 47 m t s V h r
94 m 3/hr
Fire water at 2016 m t s V h r
Potable water at 23.7 m 3/day
Compressed air at 560 m 3/hr
(25%)
Britoil
Partners
(estimated reserves:
FABRICATOR:
Partners
ft.)
COMMUNICATIONS MODULE CONTAINS A:- MET. station, helicopter control centre,
data system, micro wave system, private radio system,
Inmarsat terminal, telephone, telefax and facsimile
facilities and a solas system.
Block 49/21
49/21 possibly extending into 49/16
and will be developed by one
Conoco
(25%)
unmanned satellite platform
Britoil
(37.5%)
Arco
(12.5%)
Marathon
(12.5%)
Occidental
(12.5%)
LIFT WEIGHT:
2600 t approx.
Tabel II
Tabel 1
Fig. 1. Lincolnshire Offshore Gas Gathering System (LDGGS)
fconoco)
‘V ’ Fields Gas Area and LOGGS
Viking Gas T e r m i n a ^ - ^
Theddlethorpe
Lincolnshire
To Viking &
Victor complexes
36 in ch -7 5 mile pipeline
28 inch - 86 mile
pipeline
Gathering Station
North Valiant 1
Vulcan 2
Vulcan 1
394
Vanguard
North
Valiant 2
South Valiant
SenW 54STE IA AR G AN G NR 20
CONOCO ONTWIKKELT
V-GASVELDEN
door Ing. C. Dam
Inleiding
Conoco (UK) Ltd. brengt op d it moment
het zgn. V-Gasvelden-project to t o n tw ik­
keling op het zuidelijke deel van het Engel­
se continentale plat van de Noordzee. Met
de eerste fase van d it project is een investe­
ring gemoeid van £ 650 miljoen en geldt
dan ook op d it mom ent als de grootste
investering op het Engelse continentale
plat. Deze fase van het project bestaat uit
de ontwikkeling van de volgende drie gas­
velden Vulcan, Vanguard en South Valiant,
waarop in totaal zeven vaste platforms
worden geïnstalleerd. Conoco (UK) Ltd.
zal als licentiehouder (operator) optreden
voor deze velden in samenwerking met
Britoil pic., A rco British Limited, Marathon
Petroleum (UK) Ltd., en Occidental Pe­
troleum Cooperation.
De tweede fase houdt in de ontwikkeling
van het N o rth Valiant gasveld door C ono­
co (UK) Ltd. en het Audrey gasveld door
Phillips Petroleum. Conoco is een
dochteronderneming van Du Pont de
Nemours.
O ntw ikkelingsfase I
De drie genoemde gasvelden zoals aange­
geven in figuur !, hebben een winbare
gasvoorraad van 1020 biljoen cu. ft. en
zullen voorzien in ongeveer vijf procent
van de dagelijkse Britse gasbehoefte in het
begin van de jaren 90. De eerste gasleve­
ranties aan de British Gas Cooperation
worden verwacht in oktober 1988.
De verdeling van de licenties van de gas­
voorraden is aangegeven in tabel I.
V o or de ontw ikkeling van de drie gasvel­
den worden er vier onbemande putten­
platforms (wellhead platforms) geïnstal­
leerd, een in het Vanguard en het South
Valiant veld en twee in het Vulcan veld
Fig. 2. Gasbehandelingsplatform en accommodatieplatform (modellen)
SenW 54STE IA A R G A N G NR 20
welke op de zeebodem onderling verbon­
den worden d.m.v. gastransportleidingen
met het centrale gasbehandelingsplatform
(Central Gathering Station). H et gasbe­
handelingsplatform heeft een ontwerpca­
paciteit van 1200 miljoen cu. ft. per dag en
zal in eerste instantie bestaan u it twee
platforms; een accommodatieplatform en
een gasbehandelingsplatform (produktieplatform) figuur 2.
Twee jaar na de eerste gasproduktie zal dit
complex worden uitgebreid met een gascompressieplatform (figuur 3).
Een 36" gastransportleiding met een lengte
van 75 mijl zal op de zeebodem worden
aangelegd welke gezamenlijk beheerd
w o rd t door Conoco en Britoil. Deze gas­
transportleiding zal het voorbehandelde
gas vanaf het produktieplatform trans­
porteren naar de uit te breiden Viking
gastermina! in Theddlethorpe - Lincoln-
Fabrikanten
- Design and Project Management:
Brown and Root (U K ) Limited, W im ­
bledon, Surrey, U.K.
- Onshore Design and Project Manage­
ment: John Brown U K Limited, London,
U.K.
- Pipeline Steel and Fabrication: Mannesmann Handel AG, Muelheim, W est
Germany.
- Jacket Fabrication: Howard Doris Limi­
ted, Wallsend, Tyneside, U.K.
- Wellhead Platform Deck Fabrication:
UIE (Scotland) Limited, Clydebank,
U.K.
- Production Deck Fabrication: Press O ff­
shore Limited, Wallsend, U.K.
- Accommodation Module Fabrication:
HCG, Rotterdam, Netherlands.
- Pipe Route Survey: Racal Survey (UK)
Limited, Great Yarmouth, U.K.
- Template Fabrication: Turm eric Limi­
ted, Great Yarmouth, U.K.
- Drilling Rig Hire: Taywood-Santa Fe Li­
mited, Aberdeen, U.K.
- Theddlethorpe Office Extension: Clugston C onstruction Limited, Scunthorpe,
U.K.
Fig. 3. Gas gathering station
shire, ook deze installatie w o rd t beheerd
d oor Conoco en Britoil.
H et gewonnen gas zal op deze nieuwe
uitbreiding van de gasterminal w orden be­
handeld en op specificatie worden ge­
bracht alvorens het via gasmeetstations
afgeleverd w o rd t aan de nabij gelegen in­
stallatie van British Gas Cooperation.
H et is te verwachten dat de andere gas­
voorraden welke in de toekom st in d it
gebied zullen worden gewonnen door d it
nieuwe transportsysteem, beter bekend
als het Lincolnshire Offshore Gas Gathe­
ring System (LOGGS), zullen w orden
getransporteerd.
De nieuwe gasterminal en het gasbehandelingsplatform hebben beide een piekcapacite it van 1200 miljoen cu. ft. per dag,
waarbij nu reeds voorzieningen zijn g etrof­
fen om in de toekom st de capaciteit sterk
te vergroten om aan de verwachte gasle­
veranties uit de overige velden in d it ge­
bied te kunnen voldoen.
structors verantw oordelijk zijn vo or de
uitbreiding van de bestaande Viking gaster­
minal in Theddlethorpe waarmee een in­
vestering van £ 50 miljoen is gemoeid.
De fabricage en assemblage van de jackets
(onderbouw) en de platform dekconstrukties, worden hoofdzakelijk door Engelse
constructiebedrijven uitgevoerd, zoals in
onderstaand overzicht is aangegeven,
waarbij het opm erkelijk is dat de N eder­
landse offshore fabrikant HCG-Schiedam
het accommodatieplatform heeft w eten te
verwerven.
N ederlandse d eeln am e
H et accommodatieplatform v o rm t een
onderdeel van het centrale gasbehandelingscomplex en bestaat uit een 4-poots
jacket met daarop een geïntegreerde plat­
form accommodatie dekkonstruktie.
Deze accommodatie bestaat uit vier ver­
diepingen en heeft een capaciteit vo or een
permanente bezetting van 125 man (figuur
5 en 6).
Boven op de konstruktie van het accom­
modatieplatform rust het landings- en behandelingsplatform vo or helikopters (Si­
korsky SN61).
H et accommodatieplatform dat momen­
Fig. 4. V ’ fields development outline
‘V’ Fields Development Outline
(conoco)
H et nieuwe LOGGS-gastransportsysteem
w o rd t een van de grootste transportsyste­
men van het zuidelijke deel van het Britse
continentale plat en in de toekom st kan dit
systeem voorzien in het transport van ca.
20% van de dagelijkse Britse gasbehoefte
(figuur 4).
Fabricage
H et ontw erp en het project management
van de offshore-installaties w o rd t uitge­
voerd door Brown & Root (U K ) Limited,
te rw ijl John Brown Engineers and Con396
SenW 54STE IA AR G AN G NR 20
SECTION B - B
Fig. 5
teel w o rd t gebouwd op de w e rf van HCG
- S.O. - Schiedam (figuur 7) kan volledig
onafhankelijk van de overige platforms
functioneren daar het een eigen energie­
voorziening bezit.
Tevens is d it platform voorzien van een
onafhankelijke brandbestrijdingsinstallatie
en mag dan ook als de veilige thuishaven
voor de bemanning van het gehele platformcomplex worden beschouwd bij
Fig. 6
IQiCOWft Mtmu
eventuele calamiteiten.
Hierbij kan gebruik gemaakt worden van
de tw ee reddingsboten die de volledige
bezetting van d it complex kunnen evacu­
eren.
Alle telecommunicatie van het gehele
complex w o rd t gevoerd via de centrale
controlepost op d it accommodatieplatform.
Verder is dit accommodatieplatform u it­
.~
I
SECTPN A -A
SenW 54STE IA AR G AN G NR 20
gerust m et een complete ziekenboeg, sau­
na, keuken, wasserij, recreatiezaal, sport­
zaal en bioscoop.
De een/twee persoonskamers zijn vo o r­
zien van een eigen doucheruimte en zijn
zeer smaakvol afgewerkt en ingericht en
voorzien van Video/TV aansluiting.
Het gehele accommodatieplatform is in de
grote assemblagehal van HCG-Schiedam
gebouwd dus vrij van weersinvloeden wel-
ke de pro du ktiviteit en de hoge kw aliteits­
eisen van Conoco ten goede komen. De
mechanische en elektrische installaties zul­
len in november 1988 worden opgeleverd
waarbij de zgn. load-out gepland staat voor
februari 1988. H et totale gewicht van het
accommodatieplatform bedraagt 2500 ton
en vo o r nadere details w o rd t verwezen
naar tabel II.
In stallatie buitengaats
De vijf eerste jackets zijn binnen een zeer
krap tijdschema van 5 1/2 maand gecom­
pleteerd en zijn d oo r het kraanschip van Mc
D e rm o tt DB 101 geïnstalleerd.
Elk wellhead platform jacket weegt onge­
veer 900 ton, het accommodatieplatform
jacket weegt 6 10 ton en het produktieplatform jacket w eegt 1200 ton. De hoogte
van de jackets varieert t.g.v. de verschillen­
de waterdiepten en bedraagt voor het
produktie- en accommodatiejacket 130 ft,
voor de Vanguard en Vulcan I jackets 154 ft
en het South Valiant jacket 171 ft.
Tijdens de installatie van het accommodatieplatform -jacket zijn tijdens het heien
van de heipalen enige complicaties o n t­
staan waarbij beschadigingen aan de
bracings/anodes zijn ontstaan.
D it heeft ertoe geleid dat het jacket door
het kraanschip van M cD e rm o ttD B 101 van
Fig. 8. Lincolnshire Offshore Gas Gathering System m et de nieuwe o ntw ikke ­
lingen
Accom
‘V ’ Fields Gas Area and LOGGS
398
modatieplBtform m
aanu w " - '
(conoco)
SenW 54STE IA AR G AN G NR 20
Fig. 9. Overzicht van de gasvelden voor de Engelse oostkust
Tabel III
The North Valiant partnerships
Block 49/16 - Conoco 50%
de zeebodem moest worden gelicht voor
nadere inspectie en reparatie.
Deze tegenvaller zal volgens Conoco geen
invloed hebben op het totale installatie­
schema.
Het installeren van de reeds gecomple­
teerde dekkonstrukties w o rd t door het
kraanschip van M cD erm ott DB 101 uitge­
voerd.
Het leggen van de hoofdgastransportlei­
ding van 36" over een lengte van 75 mijl
w ordt uitgevoerd door de semi-submersible pipelaybarge Castoro Sei. De vier in­
terconnectie zeebodemleidingen die het
South Valiant, Vanguard en Valiant I en II
met het centrale gasbehandelingsplatform
verbinden zullen door de Semac pipelay­
barge worden gelegd en variëren van 10"
to t 18” in diameter en hebben een totale
lengte van 23 mijl.
De ontw ikkelingsfase 2
In aanvulling op de boven omschreven o n t­
wikkeling zal ook het N o rth Valiant pro­
ject door Conoco (UK) Ltd. worden o n t­
wikkeld. De tw ee platforms worden ge­
plaatst in de blokken 49/16 en 48/20a en
zullen van 12 putten w orden voorzien. Een
van de platforms zal m et een brug verbon­
den w orden met het centrale gasbehande­
lingsplatform van het Lincolnshire O ff­
shore Gas Gathering System (LOGGS) het
tweede satellietplatform w o rd t op drie
mijl afstand daarvan geplaatst (figuur 8).
Op het N o rth Valiant gasveld tre e d t C o ­
noco (UK) Ltd. als operator op met als
partners B ritoil, Shell (UK) en Esso Explo­
ration and Production vo o r een verdeling
van de belangen (zie tabel III).
SenW 54STE IAAR G AN G NR 20
Britoil 50%
Block 48/20a - Shell 50%
Esso 50%
LOGGS
Conoco 50%
Britoil 50%
Approximately
75 per
cent of North Valiant's gas
estimated to lie in block 49/16,
H et N o rth Valiant project welke een in­
vestering vergt van £ 110 miljoen, is het
vijfde gasveld dat aangesloten gaat worden
op het LOGGS-systeem. O o k vo or d it
project geldt dat het eerste gas in oktober
1988 aangeleverd w o rd t op de uitgebreide
Viking gasterminal in Theddlethorpe.
Hiermede w o rd t bereikt dat deze vijf gas­
velden tezamen in het begin van de jaren 90
voor ca. 12% kunnen voorzien in de dage­
lijkse Britse gasbehoefte.
Een tweede investering in deze tweede
ontwikkelingsfase zijn de activiteiten van
Phillips Petroleum door het ontwikkelen
van het Audrey gasveld in blok 4 9 /Ma
waarmee een investering is gemoeid van
£ 80 miljoen.
In d it gasveld zal Phillips Petroleum als
operator optreden vo or de partners C o­
noco (UK) Ltd en B rito il die vo or elk 35%
deelnemen in d it project.
De maximum gasproduktie van d it gasveld
w o rd t geschat op 450 miljoen cu. ft./dag en
dit gas zal door een nog aan te leggen
gastransportleiding van 20" over een leng­
te van 10,5 mijl getransporteerd worden
via Conoco’s centrale gasbehandelingsplatform naar de Viking gasterminal.
reserves a r e
25 per cent in block 4 8 / 2 0 a .
Een seperate 3" methanol-leiding zal vanaf
het centrale gasbehandelingsplatform naar
het Audrey platform worden aangelegd.
Het totale platform gewicht w o rd t door
de nieuw opgerichte ingenieursbureaucombinatie Brown & Root Vickers Ltd.
geschat op 2500 ton.
O ok van d it gasveld w o rd t verwacht dat
het eerste gas en condensaat in oktober
1988 via het centrale gasbehandelingsplat­
form en het LOGGS-systeem kan worden
aangeleverd.
Een bijzonderheid is nog dat het centrale
Conoco complex ook voor d it Audrey
gasveld, de gascompressie zal verzorgen
(figuur 9).
C e rtific a tie
Alle genoemde platformconstructies zul­
len worden ontworpen, gebouwd en geïn­
stalleerd volgens de eisen van het Departe­
ment o f Energy (SI 289) en zullen door
Lloyd’s Register worden gecertificeerd.
M et dank aan:
- Conoco (UK) Ltd. - London
Public Affairs Departm ent
- HCG (S.O.) - Schiedam
399
DESIGN ASPECTS OF FLOATING
PRODUCTION STATIONS*
by H. Boonstra,* *
S u m m ary
Several design aspects o f and requirements fo r semi-submersible production platforms
are discussed, in particular those which result in differences w ith drilling semi-submersibles, such as sailing and tow ing characteristics, load carrying capacity, free ventilated
spaces and fatigue resistance.
The N orring-4, a semi-submersible which is designed as a floating production station is
introduced briefly.
Intro d uctio n
The number o f semi-submersibles is small
when compared to ships; fo r instance the
total number of semi-subs on ord er end of
1985 was 24, whereas in the same year
2 2 10 ships ( 100 gross tonnage and upward)
w ere completed [5], It is estimated that the
amount o f steel in those 24 semi-submersi­
bles is less than 5% o f the steel used fo r
building o f ships in 1985. Only one o f the 24
semi-subs on order in 1986 is purposely
built as a production station. A few o the r
units have contingencies built in regarding
deckload and deckspace in ord er to be
converted to a tem porary floating produc­
tion station at short notice. This illustrates
the fact that offshore production o f hydro­
carbons by means of floating platforms is
still in its infancy.
W hy is it then that several shipyards, con­
sultancy firms and engineering contractors
market designs fo r floating production sta­
tions?
The answer to this question is that there is a
general feeling in the industry that offshore
oil and gas reserves in deeper w ater can
only be economically recovered by techni­
cal means o the r than fixed platforms of
which the capital costs increase progres­
sively w ith the waterdepth.
Experience gained in recent years w ith
converted drilling semi-submersibles has
shown that this type o f unit forms a reliable
and stable platform fo r production o f hy­
drocarbons.
In the next sections design aspects o f pur­
posely built semi-submersible production
stations are discussed. The last section o f
this paper introduces the N orring-4 semisubmersible floating production station.
* Lecture presented at the W EMT Confer­
ence. ’Advances in Offshore Technology'. Am­
sterdam 25-27 Nov. 86.
** Fluor Marcon Offshore Haarlem.
400
S E M I-S U B M E R S IB L E
PLATFORM S - GENERAL
Semi-submersible platforms have been in
use in the offshore industry fo r almost 25
years. A t the moment approximately 230
platforms o f this type exist w orldw ide, the
m ajority is being used as mobile drilling
platform [8], In table I a split-up is given.
Although the semi-submersible type of
platform is by far outnumbered by the jackup type (o f which approximately tw ice as
much units exist), in deep and hostile wa­
ters the semi-submersible is the prominent
type o f mobile offshore platform.
The shape and geom etry o f semi-submersi­
bles covers a wide range, o f which only the
most prom inent types are mentioned
briefly. Some designs consist o f a number o f
circular columns (generally three o r five),
each provided w ith a footing o r low er hull.
Structural integrity is achieved by a re­
latively complicated bracing system and by
a truss type deck. Examples o f this m ulti­
hull type are the Sedco 135 series, the
W est Venture and the Pentagon type.
O th e r platforms consist o f tw o parallel
low er hulls, provided w ith generally six or
eight colums. The columns may be circular
or rectangular in shape. The deck can be
made up from trusses o r may be o f the
stiffened plate type. Bracings are generally
used to provide structural integrity o f the
platform. Examples o f this configuration
are the A ke r H3. the Sedco 700 series and
the Pacesetter type.
In the recent years several trends in the
choice o f configuration and shaping of
semi-submersibles can be discerned.
- The multi-hull type has become old
fashioned and is no longer prom oted by
designers. Apparently the potential advan­
tages o f this type such as the possibility to
achieve superior m otion characteristics
fo r platforms w ith a relatively small
displacement and the independence of
angle o f attact o f current and waves do not
justify the inherent poor tow ing char­
acteristics. Undoubtedly the accident w ith
the Pentagon type platform Alexander
Kieltand, where the structural failure o f
one bracing caused the loss o f a complete
column and resulted in capsizing o f the
platform, has played a role in this respect.
- The tw o -flo ate r type has increased in
popularity in the recent years. It appears
that fo r the latest designs o f this type the
number o f bracings is gradually decreasing.
Also there is a tendency to reduce the
number o f columns, in some designs even
to four (e.g. G V A 4000). As a result the
unsupported span o f the deckstructure has
increased and also the loading o f the column-deck connection is increased, both
effects resulting in an increase in structural
weight o f the deck. This apparently is
accepted by the designers at the advantage
of a clean structure and avoidance o f fatigue
problems in the bracing connections.
- The deckstructure o f most o f the mod­
ern semi-submersible platforms is built-up
from stiffened plate instead o f a truss type
structure.
S E M I-S U B M E R S IB L E
P LA TFO R M S FOR
P R O D U C T IO N
During the past tw o decades the semi-
Table I, split up of semi-submersible platform s, w orldw ide, 1986
Num ber
Mobile drilling
Accommodation
Production (converted)
Maintenance, general service
Craneage
Pipe laying
180
18
15
6
5
4
Semi-submersible platforms, total
228
SenW 54STE IAAR.GANG NR 20
submersible platform, despite some se­
rious accidents, has proven to be a safe,
reliable and stable w orkstation in the most
severe sea states. This type o f platform
therefore is well suited to be successfully
used as a floating production station.
The first floating production platform was
installed by Hamilton Brothers Oil & Gas in
1975 at the Argyll field, using a converted
drilling semi-submersible, The Trans­
world-58.
Today the number o f semi-submersible
based production platforms is 14, o f which
tw o are located in the N o rth Sea (Argyll,
Buchan) and ten in Brazilian waters [8].
These existing semi-submersible based
production platforms are all converted
drilling platforms. O f the three semi-submersible production platforms planned fo r
installation in 1987, one is a new built
platform (Sun Oil, Balmoral field using a
GVA 5000 design) the o the r tw o are con­
versions of drilling platforms.
A converted drilling platform may w ell be
an economical, and from technical point of
view an acceptable, floating production
station, in particular fo r small oil reserves
and a limited number o f wells to be de­
pleted in a few years.
However in general the requirements fo r a
floating productibn station differ consider­
ably from those o f a drilling platform. The
most im portant aspect w ill be elaborated
and highlighted in the next sections. The
implication is that optimal configuration
and layo utdiffe rfor both types o f platform.
In the open literature only limited informa­
tion can be found on specific design aspects
of floating production. An exception is a
paper by Burn and Graaf [ I ] which de­
scribes the Semi-Spar concept developed
by Shell.
D E S IG N C O N S ID E R A T IO N S
The most im portant aspects which dis­
tinguish a semi-submersible production
platform from a drilling platform are dis­
cussed below. These aspects cause differ­
ences in design considerations and
weighing o f aspects fo r both platform
types and result in the end that different
solutions regarding configuration and lay­
out w ill be chosen.
Sailing and to w in g characteristics
Drilling semi-submersibles have to be
moved from one location to an o the r reg­
ularly, say once in six o r eight weeks. The
distance may be a few miles (in one field), a
few hundred miles (in one geographical
area) o r in some cases a complete ocean has
to be sailed across.
All modern drilling rigs therefore are
shaped in such a way that at transit draft a
speed o f approximately 10 knots can be
reached under to w o r even by use o f its
own thrusters. For a production platform,
which is designed to remain several years at
one location there is no economic incen­
SenW 54STE IAAR G A N G NR 20
tive to choose a configuration and shape o f
the floater which minimizes tow ing resist­
ance. In case a long ocean to w is required
from the building yard to the field, a dry
to w is the obvious method o f transport.
The fact that optim ization o r sailing char­
acteristics are not required means that the
configuration can be chosen in which all
bracings are eliminated, which may im­
prove fatigue resistance greatly.
Load carrying capacity and deckload
Much confusion exists about the load car­
rying capacity o f semisubmersible plat­
forms. The confusion is probably due to the
fact that the ’deckload' capability o f a
mobile drilling platform is compared to the
’deckweight’ o f a fixed platform. Such a
comparison is unrealistic because the deck­
load o f a mobile drilling platform is defined
as its capability to carry variable loads such
as mud, cement, chemicals, drillpipe, cas­
ing, BOP, riser joints etc. at deck (for most
semi-submersibles this figure varies be­
tween 1700 tons fo r the older units to
3000 ton, o r even 4000 ton fo r modern
rigs), but excludes weight o f deck struc­
ture, accommodation, pow er generation,
utilities, derrick etc. The 'deckweight' o f a
fixed platform comprises all weights o f the
deckstructure, accommodation, utilities,
pow er generation, production facilities
etc. Knecht and Bernard [4] state the
differences clearly.
In order to make a realistic comparison
between afloating and a fixed structure it is
appropriate to define fo r a floating station
the 'topside potential’, which includes all
weight components above the to p o f the
columns: structural steel, accommodation,
utilities, pow er generation, production
facilities etc.
This ’topside potential’ roughly compares
w ith the 'deckweight' o f a fixed structure.
It should be realized however that also this
comparison is not perfect:
- The structural steel o f the deck of a
semi-submersible platform generally w ill
exceed the structural w eight o f the deck o f
a fixed structure due to the larger unsup­
ported span o f the floater deck.
- On the o the r hand the semi-submersi­
ble platform offers the possibility to store
fuel and potable w ater in the low er hull,
while this weight does not count fo r the
’topside potential’, contrary to the case fo r
the fixed structure w here these items have
to be included in the deckweight.
Additionally it is possible, as pointed out by
Burn and Graaf [ I ], to ta ilo r the equipment
and lay-out to the specific situation at a
floating production station.
It can be concluded that in o rd e r to make a
fair comparison between such various op­
tions as a fixed platform o r a floater a fron tend feasibility study is required in which o f
various options the specific merits are in­
vestigated.
Reserve buoyancy and free -v e n tila tion
The hydrodynamic stability o f semi-sub­
mersible platforms in intact condition has
in the past never caused mishaps o r danger­
ous situations. In damaged conditions
however, the flooding o f one o r more
compartments causes heeling moments
which result easily in large angles o f heel.
Investigations into the accidents w ith the
Alexander Kiel land and the Ocean Ranger
have shown that the safety o f a semi-submersible and its crew is greatly improved
when sufficient reserve buoyancy is avail­
able to lim it the angle o f heel in case of an
accident. The obvious method to create
reserve buoyancy is to make (part of) the
deckstructure watertight.
A recent trend in the design and lay-out o f
process plants is to create free-ventilated
spaces in which the hazardous equipment is
located.
Apart from saving w eight and space by
avoiding a complicated forced ventilation
system, the safety is improved due to the
fact that an explosion in an open environ­
ment causes less damage than in an en­
closed space.
Both trends, the enclosed deck fo r reserve
buoyancy and the open, free ventilated lay­
out o f production facilities are in conflict
w ith each other.
It requires intensive cooperation between
engineers o f various disciplines such as na­
val architecture, process, piping and
structural to provide in a specific case the
optimal solution o r compromise. O ur ex­
perience is that a set-up o f the deck, based
on a truss type structure, where required
enclosed by stiffened plate panels, which
contribute in the overall strength, offers a
potential sound basis fo r a balanced de­
tailed design.
S torage o f crude
Semi-submersible drilling platforms gen­
erally do n ot have facilities fo r storage o f
crude. It appears to be difficult to provide
crude storage tanks at a later stage in semisubmersibles during conversion to p ro ­
duction platforms, because rules o f Clas­
sification Societies regarding explosion
safety are very strict. Ballast w ater tanks
adjacent to crude storage tanks, as well as
the pump room where the ballast w ater is
being pumped are turned into hazardous
areas and require explosion-proof pumps
etc. In new built production platforms
crude storage tanks can be incorporated in
the low er hulls at no costs to stability.
Although in case the offloading is taking
place via a pipeline to the shore, crude
storage is, strictly speaking, not required
o r necessary, a small storage capacity (a
few hours o f production) may be advan­
tageous in case repair to the offloading
equipment (pump, riser) is required. This
can be arranged in dedicated tanks.
If offloading is done by means o f a shuttle
401
T
DT
T R A N S IT
DRAUG H T
Fig. I. N orrin g-4 sizing logic
Fig. 2. Basic platform configuration
Fig. 3. Deck lay o ut
Fig. 4. Comparison heave transfer functions N orring-4
O RIG IN A L OESlON
...
ALT, 1
MO OIF IE 0
CRO SS SEC T IO N
ALT. 2
T R IA N G U L A R SEC T IO N S IN
ALT
BOTH
3
ALT. 1 A N D
FL O A T E R
C O R N E R S OF LOWER M U LLS
ALT. 2
20
M EZZA NINE
402
DECK
LFVFI
25
30
35
WAVE PERIOD IN SECONDS
SenW 54STE [A A R G A N G NR 20
tanker via an S.P.M. installation, larger sto r­
age may be required in order to avoid shutin o f production in severe weather condi­
tions.
One to tw o days production can be stored
in displacement tanks which contain either
ballast w ater o r crude. A rather com pli­
cated system fo r treatm ent o f bal last w ater
has to be installed in that case.
Periodic surveys/fatigue
Classification Societies require fo r mobile
drilling platforms periodic surveys. An
annual survey can in principle take place on
location, fo r the intermediate survey (w ith
an interval o f 2.5 years) and the special
survey (interval 4 years) the unit has to be
brought into sheltered water. For a semisubmersible production platform a similar
requirement would mean a considerable
loss o f production. This can be avoided if
the inspection and surveys are executed at
location, similar to the procedures fo r fix ­
ed, bottom supported structures. Alm ost
all present-day drilling semi-submersibles
suffer from fatigue, in particular at bracing
connections, and (although generally
small) repairs are required after survey of
the structure. It is therefore necessary that
semi-submersible production platforms
are designed in such a way that the struc­
ture becomes less fatigue-sensitive, which
justifies the survey at location and elimin­
ates the need to bring the platform to a
sheltered location fo r repair o f the hull.
An effective method to avoid fatigue is to
eliminate stress concentrations in non-redundant parts o f the structure. This can be
realized by om itting all bracings. The fati­
gue life o f critical parts of the structure, i.e.
the connections o f the low er hulls and deck
to the columns can be designed and fabri­
cated in such a way that the fatigue life
exceeds the economic life o f the platform
several times.
Station keeping - thrusters
Most modern drilling semi-submersibles
are provided w ith propulsion devices, gen­
erally azimuthing thrusters which are also
used to assist the catenary m ooring system
by counteracting static forces from wind
and current during severe weather condi­
tions.
For a production semi-submersible the in­
stallation o f thrusters seems not economi­
cally justified; the system would only be
used fo r assistance o f the m ooring system
in severe weather conditions. It is easier
and less expensive to invest in an increased
capability of the catenary mooring system.
In this way fuel is saved and the reliability
(which is never 100% fo r a thruster sys­
tem) is increased.
From safety point o f view the require­
ments fo r the m ooring system o f a produc­
tion platform should be in excess o f the
requirements fo r a drilling platform. D ur­
ing severe weather conditions drilling ope­
SenW 54STE IA AR G AN G NR 20
rations are suspended and the w ell is secu­
red. In case o f a production platform, w ith a
riser system which can remain operating
during survival conditions, the platform is
connected w ith live wells and a failure o f
the mooring system leaves only the subsea
valves to prevent a blow out.
N E W B U IL T O R C O N V E R S IO N
Before a decision is made by the operator
o f an offshore field on the development
scheme and before the choice o f platform
type is made, generally a front-end study
will be made in which various options are
compared on economical and technical
grounds.
The viability o f a semi-submersible produc­
tion platform depends on aspects such as
waterdepth, type and characteristics o f the
field, its expected lifetime, etc.
The decision w hether to go fo r a conver­
sion o r to o pt fo r a new built platform also
requires a front-end comparison study,
involving the current day rate of semisubs,
the w eight and size o f the production facili­
ties (which not only depends on the expec­
ted maximum daily production, but also on
requirements regarding injection o f gas o r
water, gas lift, offloading etc.), pow er re ­
quirements, field lifetime etc.
In some cases the decision is easily made;
heavy and spacious equipment, exceeding
the carrying capacity o f existing semisubs,
large number o f risers etc. call fo r a new
built platform. On the other hand exten­
ded well test o r a simple production sche­
me w ith a few wells only, can easily be
accommodated at a converted platform.
Although conversions can be very compli­
cated in particular when part o f the exis­
ting equipment has to be removed for
stability o r space problems and overrun in
time and budget is hard to avoid (see Logan
et. al.) [6], all 15 o r so present day conver­
sions have proved to result in economical
production schemes. For small fields con­
versions still w ill remain an appropriate
solution, however probably the most im­
portant aspect o f it is that a lot o f experien­
ce is gained w ith floating production, both
regarding topside facilities and riser sys­
tems, which improves the confidence in
floating production and which can be used
in larger fields where new built platforms
are required w ith the inherent large in­
vestments.
P R O D U C T IO N RISER S Y S T E M
The first riser systems used fo r the produc­
tion o f oil by means o f a semi-submersible
platform w ere based on drilling riser tech­
nology. Individual flowlines are spread
around and attached to a central core, used
for the e xp o rt o f the crude, similar to the
kill and choke line attached to a drilling
riser. Tensioning devices at the platform
prevent the riser structure from buckling.
The tw o main arguments against this type
of production riser are;
- the riser has to be disconnected in se­
vere weather conditions, resulting in loss
o f production
- the system becomes very complicated in
particular when the number o f flowlines is
increased.
Several alternative riser systems have been
proposed in the recent past, ranging from
buoyant articulated structures to com­
pletely flexible pipes, hung off from the
platform.
In the last years the use of flexpipe risers
has gained increased confidence in the off­
shore industry. A lo t o f experience is ac­
quired in Brazilian waters (where 10 con­
verted semisubs are used fo r oil produc­
tion, all producing by means o f flexpipe
risers). Early 1987 the Sun O il purposely
built production platform fo r the Balmoral
field w ill start producing also through fle x­
pipe risers [7],
The flexpipe may contain several fluid lines
(m ulti-bore type) and may be hung off
either from the deck o f the floater o r be
connected to steel pipes at the low er hull,
depending on the choice between easy
inspection and repair on one hand and the
possible wear and decreased safety by
passing of the wave zone.
The flexpipe may be guided to the seabed
connection by various shapes e.g. ’steep-S’,
’lazy-S' through a submerged buoy o r dis­
tributed buoyancy elements along the
pipe, see Mahoney et.al., [7], O ther confi­
gurations are also possible fo r example by
using an articulated, submerged, steel riser
structure from the seabed to approxima­
tely 40 m below the surface, the flexpipes
are then connected to the top o f the articu­
lated structure.
The major advantage o f flexpipe risers is
that the system can remain operational
during severe N o rth Sea environmental
conditions. Further aspects of flexpipe ri­
ser systems are:
- the number o f individual flowlines, con­
tro l lines etc. can be increased far beyond
the potentials o f a rigid tensioned riser
system.
- the position where the risers are at­
tached to the platform can be chosen
more o r less freely; and can be adapted to
the optimal layout o f the process facilities.
- if required, the platform can be provided
w ith a w o rk-o ve r o r complete drilling rig
w itho ut interference w ith the production
riser system.
T H E N O R R IN G -4 F L O A T IN G
P R O D U C T IO N S T A T IO N
In this section the N orring-4, a four column
semi-submersible w ith a low er hull fo rm ­
ing a square ring, is introduced briefly.
More detailed information is given in a
paper by Van Holst [3], The platform is
designed as a floating production station
and major aspects discussed above are in­
corporated in the design.
Because process plant parameters differ
403
considerably from case to case, resulting in
different requirements regarding deck
load and and space, main dimensions and
particulars have to be established in each
individual case in ord er to arrive at an
optional solution.
Sizing P ro g ra m
C om puter programs based on algorithms
fo r estimate o f steel weight, hydrostatic
stability, m otion behaviour etc. are cost
effective tools to generate a series o f preli­
minary designs. See fo r instance Penny
et.al. [ 10]. For the N orring-4 type platform
a com puter program was developed to
perform a first pass sizing depending on
topside weight, draught, underdeck clear­
ance and stability requirements. Figure I
shows the sizing logic.
A similar progam fo r a tw o floater drilling
platform is described by Penny et.al. [10].
G en eral description and basic d ata
For a process plant based on data shown in
Table II a N orring-4 platform has been
w orked o ut in detail, up to pre-certifica­
tion approval by Lloyd’s Register. The prin­
cipal dimensions, the weights o f equipment
and structural steel can be found in Tables
III and IV.
The hull structure, as shown in Fig. 2, is
completely built up from flat stiffened plate
panels. It does not contain curved elements
o r plates nor does it have any braces.
Overall structural integrity is attained by
stiff frames form ed by the low er hulls, the
columns and the deck.
Parts o f the structure vulnerable to fatigue
are minimized and located in areas w ith
sufficient redundancy.
The structure is assessed by Lloyd’s Regis­
te r and has been granted a pre-certification
approval.
D eck structures
T w o types o f deck structure can be applied
in the N orring-4 design, depending on re­
Fluid Production Rate:
Gas Production Rate:
GOR:
Maximum W ater Production Rate:
Treated W a te r Quality:
Crude Storage Capacity:
T ab le II, design d a ta fo r process/N orring-4
Length - w idth overall floaters
Length - w idth overall deck
Elevation low er deck
Elevation upper deck
Height o f low er hulls
W id th o f low er hulls
Column dimension (side o f square)
Draught, operating
Draught, transit
Displacement: operating
transit
75,00 m
75,00 m
40,75 m
49,00 m
8,50 m
13,50 m
13,50 m
25,00 m
7,80 m
41 300 ton
26500 ton
T ab le III, principal dim ensions, N o rrin g -4
quirements regarding free ventilated
spaced and reserve buoyancy.
The first type o f deck structure consists
basically o f large trusses w ith a height o f
approximately 12 m., spaced apart at 12 m.
distance.
The trusses may be enclosed by stiffened
flat plate panels as required, fo r instance
above the to p o f the columns to achieve
reserve buoyancy and fo r protection o f the
living quarters and the pow er generation
equipment. The process facility and all ha­
zardous equipment can be located in com­
pletely free ventilated areas.
The second option is a deck form ed by
large box girders arranged in a square
configuration. The box girders are housing
the pow er generation and distribution
equipment, the living quarters, the HVAC
and utilities.
The central area formed by the box girders
T a b le IV , w e ig h t o f e q u ip m e n t and stru c tu ra l steel, N o rrin g -4
Steel w e ig h t
Lower hulls
Columns
Decks
5700 ton
3450 ton
6300 ton
Total
D eck load
Process equipment and utilities (w et)
Riser system
Living quarters
Platform systems *
Contingency
15450 ton
4450
250
1200
1350
1200
Total
*) excluding systems in columns and low e r hulls
404
50,000 b/d (330 m 3/hr)
25-35 MMSCFD
(27.5 - 38.5 x l0 3N m 3/hr)
500 - 700
20% at 50,000 b/d
< 30 ppm oil
28,300 bbls (4.500 m 3)
ton
ton
ton
ton
ton
8450 ton
is bridged by three large trusses which
support the decks fo r process equipment,
stores, workshops and control room.
This option results in less steel w eight than
in the case o f a truss type deck due to the
fact that structural steel o f the box girders
is effectively used both as primary strength
member and support o f equipment and
facilities. On the o th e r hand it requires a
comprehensive ventilation system in parti­
cular fo r areas w ith hazardous equipment.
Efficient Fabrication
In the recent years several attempts are
made to reduce the fabrication and build ing
costs o f marine structures. See fo r instance
Goldan [2], Incase o f the N orring efficiency
is obtained by avoiding curved and compli­
cated sections in the low er hull, the
columns and the deck.
D eck layo u t
A possible layout o f the deck, assuming
process facilities defined on basis o f data in
Table II, is shown in Figure 3. It should be
noted that o th e r arrangements are as well
possible w ithin the same structural set-up
o f the platform deck.
M otions
The configuration and shape o f the N o rring-4 have not in the first place been
optimized w ith regard to wave induced
m otion behaviour because flexpipe risers
do not impose stringent requirements in
this respect. However, the motions com­
pare well w ith average drilling semi-sub­
mersible platforms. See fo r example the
heave response curve in Fig. 4. The solid
line represents the calculated curve fo r the
basic platform w ith rectangular low er hull
sections.
SenW 54STE IA AR G AN G NR 20
floating production station, tailored to
specific design requirements and aiming at
low cost fabrication and construction.
ANCLE OF NEEL 1dcqr)
Fig. 5. N orrin g-4 Intact Stability operational condition
It has been investigated that the heave
motion can be improved if required. The
dotted lines in Fig. 4 show the effect of
decreased added mass by cutting off the
edges o f the low er hull sections, while
keeping the to ta l displacement constant.
Also the effect on the heave response of
increased buoyancy near the column fo o t­
ings is shown. The improvements in m oti­
on characteristics result in a m ore com pli­
cated and consequently more expensive
structure.
Stability
The N orring-4 design meets all intact as
well as damage stability requirements o f all
certifying authorities (e.g. Lloyds, DnV)
and governmental organizations (e.g.
NMD, DEn, USCG) w ith the restriction
that in case o f the truss type deck the high
impact requirem ent (buoyancy o f a com ­
plete column lost) is not fulfilled complete­
ly. In case o f the box girder deck w ith its
increased reserve buoyancy also this requi­
rement is met. In Fig. 5 the intact stability
curve of both types o f deck structure is
shown.
tically shown in Fig. 6. The w aterdepth at
the mating location has to be at least 40 m.
Concluding Rem arks
It is shown that design parameters fo r
semi-submersible production platforms
differ from those fo r mobile drilling units.
Consequently an optimized production
platform o f the semi-submersible type w ill
differ in shape and configuration from a
drilling platform.
The N orring-4 design is a representative
example o f a modern semi-submersible
References
1. A. j. Bum and G. Graaf, 'Topside Facilities
for Floating Production Systems Require
New Engineering Thinking', Offshore
Technology Conference, Houston, paper
OTC 4543, 1983
2. M. Goldan, 'The application of modular
elements in the design and construction of
semi-submersible platforms', Thesis, Delft
University of Technology, 1985
3. M. van Holst, 'Floating Production Station
Norring-4', ConOff, Amsterdam 1986
4. H. I. Knecht and S. W . Bernard, 'Why
mobile rigs can make reliable production
units’, Ocean Industry, December 1985
5. Lloyds Register o f Shipping, 'Annual Sum­
mary of Merchant Ships Completed in the
W orld during 1985', issued 1986
6. B. L. Logan et. al., 'Buchan Development
Project-Conversion of a Drilling Rig into a
Floating Production Platform’, Offshore
Technology Conference, Houston, paper
OTC 3985, 1981
7. T. R. Mahoney and M. J. Bouvard, 'Flexible
production riser system for floating pro­
duction application in the N orth Sea',
Offshore Technology Conference, Hous­
ton, paper OTC 5163, 1986
8. Ocean Industry, September 1985, 'Direc­
to ry o f Marine Drilling Rigs’
9. Offshore Engineer, April (986 'Floating
Production System Review'
10. P. W . Penny and R. M. Riser, 'Preliminary
Design o f Semi-submersibles’, Trans NEC
Institution of Engineers and Shipbuilders,
101, 1985
Fig.6. Proposed construction m ethod and deck mating procedure
Mooring
The mooring system consists o f 12 legs of
4" super quality chain. For a w aterdepth o f
300 m the length o f each line is 1700 m. The
mooring system meets DnV (PosMoor)
requirements. Preset piled anchor points
are envisaged fo r a permanent m ooring
arrangement, instead o f ship type anchors.
Construction and deck m a tin g
The tim e schedule fo r construction o f the
unit probably can be decreased by building
the hull and the deck separately. A fu rthe r
advantage o f a separate building is that the
equipment and facilities at deck can be
installed and tested at surface level. A
possible procedure fo r the mating o f deck
and hull in a sheltered location is schema­
SenW 54STE IAAR G AN G NR 20
405
rfïp.? W M . W ' W m ' i
% Jÿ * W
«Motoren tot 4000 pk W/
800- 1500 omw/min.
HàtiideknKàfW>n:
A
M H I SAM O FA D I E S E L BV
M IT S U B IS H I
D IE SE L M O T O R E N
Europese h o olävestiging van M itsubishi
H eavy Industries-E ngine D ivision J a p a n
Postbus 20, 3840 AÀ H ard erw ijk,
T e l:0 3 4 1 0 -130+1 T ele x : 47330
T ele tax :0 3 4 1 0 -19060
Daarom buigt Seton de pijpen machinaal. Elke
gebogen bocht scheelt 2 lassen. Dat leidt regelrecht
naar een betere kwaliteit van de pijpen.
En het laswerk dat resteert wordt door ervaren en
goed geschoolde vakmensen zeer nauwgezet gedaan.
H O E MINDER LASSEN, H O E BETER D E PIJP.
Seton fabriceert enkel en alleen pijpleidingen. Volgens
't Prefab-systeem. Deze specialisatie is onze kracht.
Het resultaat is dat alle pijpen van Seton al volledig
afgelast (en zelfs met de juiste
oppervlaktebehandeling) maatklaar naar het werk
gaan. Dat komt de kwaliteit van de installatie ten
goede. Verder scheelt het een hoop heen-en-weer
gesjouw. Dus tijd.
Seton is erbij. Vanaf het eerste ontwerp tot en met
de komplete installering.
Informatie en offertes:
Ketelweg 30, 3356 L E Papendrecht. Telefoon (078) 152011.
Want wat waard is
gedaan te worden,
is waard goed
gedaan te worden.
SETON
PIJPLEIDINGEN
A3
NIEUWSBERICHTEN
House, 55/59 Fife Road, Kingston upon
Thames, Surrey KTI ITA. Tel: 01-549
5831.
Agenda
4th Cruise Shipping C onference
& Exhibition
Seatrade's annual Cruise Shipping event now firm ly established as the annual forum
for the international cruise industry-takes
place on February 23-25, 1988 at the Fon­
tainebleau H ilton in Miami, USA.
The shape o f the cruise industry as it moves
into the nineteen nineties w ill be a principal
theme o f Cruise Shipping 88, w ith expert
speakers looking ahead to how and where
the next generation o f cruise ships w ill be
designed, built, financed, and positioned in
the market place, in order to broaden the
appeal o f the cruise product. Sessions on
subjects ranging from on-ship operations
and insurance through to marketing and
promotion w ill give this event a broad
appeal to all segments o f the cruise in­
dustry.
The conference w ill be introduced by A.
Kirk Lanterman, President, Holland A m er­
ica Line - Westours, Inc., and o the r speak­
ers w ill include Robert H. Dickinson,
Senior Vice President, Sales and M arket­
ing, Carnival Cruise Lines; Carmen J.
Lunetta, Port D irector, Port o f Miami, Jay
Silberman, President, National Associa­
tion of Cruise Only Agencies (N A C O A )
and A lf P. Poliak, Managing D ire ctor,
Seetours International GMBH, Frankfurt.
For further information please contact
Seatrade, Fairfax House, Colchester COI
IRJ U K Tel: (0206) 45121.
Sixth offshore c o m p u te r show
The sixth Offshore Com puters C onfer­
ence and Exhibition w ill be held 22-24
March 1988 at the Aberdeen Exhibition
and Conference Centre, Aberdeen, UK.
The theme o f the three day event, orga­
nised by Offshore Conferences and Exhibi­
tions, wi II be the e xten t to which the use o f
computers applications increasingly aids
cost efficiency in the offshore oil and gas
industry.
The exhibition w ill reflect current ad­
vances in hardware and software fo r use by
the offshore oil and gas industry. A call fo r
papers outlining the main areas o f interest
in the associated conference is being pub­
lished shortly and full information on ex­
hibit costs w ill be available from Offshore
Conferences and Exhibitions, Rowe
SenW 54STE IÂAR G AN G NR 20
Technische
informatie
N ie u w d e m o n s tra tie c e n tru m voo r
oppervlaktebehandelingstechnieken
en onderdelenreiniging
C.T. (BENELUX) B.V., Dordrecht, de al­
leenvertegenwoordiger in Nederland
voor de Guyson range aan straalreinigingsmachines, heeft recentelijk een nieuw de­
monstratie- en testcentrum geopend in
hun pand in de Réaumurstraat. D it centrum
is van g ro o t belang vo or managers van
grote en kleinere werkplaatsen, b etrok­
ken bij de reparatie van benzine- en diesel­
motoren en gasturbines uit de automobiel-,
scheepvaart- en luchtvaartindustrie en
eiektriciteitsopw ekki ng.
H et GUYSON systeem w e rk t d.m.v. het
gecontroleerd opbrengen van miljoenen
glasballetjes bij een hoge snelheid op het te
behandelen onderdeel, waarbij van nor­
maal onbereikbare plaatsen koolaanslag,
roest, walshuid, en andere verontreini­
gingen worden verw ijderd zonder dat de
maatvoering w o rd t aangetast o f insluitin­
gen in het oppervlak plaatsvinden.
Bovendien ontstaan voordelen zoals het
peen-effect, welke niet alleen een zijdeglans finish veroorzaakt, maar ook de ver­
moei ingsfactor opvoert, haarscheuren
zichtbaar maakt, een verbetering geeft aan
het smerend vermogen en een grotere
weerstand biedt aan koolaanhechting.
A lternatief kan in het zelfde systeem een
hard scherpkantig medium worden ge­
bruikt voor het snel verwijderen van har­
dere neerslagen, zoals verfresten en zware
walshuid, waarbij een egale matte finish o f
een hoge mate van reinheidsgraad verkre­
gen w o rd t als voorbehandeling voor me­
taal- en plasmaspuiten, verven, lijmen o f
coaten.
Guyson parel- o f gritstralen biedt belang­
rijke kosten- en omgevingsvoordelen in
vergelijking m et methodes als chemisch
badreinigen o f het traditionele borstelen
en schrapen en geeft bovenal een absoluut
superieure finish.
V o or nadere informatie: C.T. (BENELUX)
B.V., Réaumurstraat 4A, D ordrecht, 078311955
B ureau V e rita s publication,
H u ll stru ctu re fo r ships
of less than 65 m . in length
The first aim o f the amendments is to
incorporate in the main Rules, the rules
applicable to fishing vessels, launches and
sea-going launches. A t the same time, part
II (Hull) is subvided in:
- rules applicable to ships of more than 65
m. in length,
- rules applicable to ships of less than 65 m.
in length.
To this effect the rules fo r seagoing ships
are now subdivided as follows
Part I:
contains tw o chapters dealing w ith the
general requirements of classification and
surveys. Rules applicable to fishing vessels,
launches and sea-going launches have been
incorporated and up-dated.
Part II:
ships o f more than 65 m. in length: contains
the requirements governing hull structure
of ships o f more than 65 m. in length.
Part II (new):
ships o f less than 65 m. in length: contains
the requirements governing hull structure
fo r ships o f less than 65 m. in length. This
part also precises the conditions upon
which these rules may be extended to
cover certain classes of ships o f more than
65 m, but not greater than 90 m. in length.
This part incorporates the rule rules applic­
able to fishing vessels o f less than 65 m. in
length, launches and sea-going launches.
Part III:
contains the requirements applicable to all
size o f ships and governing machinery,
electricity and automation. A new section
fo r fishing vessels has been added.
Bureau V e rita s guidance n o te 199
- S teel stru c tu re fatigue
Following its action in view o f improving
safety o f units, Bureau Veritas just pub­
lished the Guidance N ote: ’Cyclic fatigue
o f nodes and welded joints o f offshore
units’.
This N ote comes as a complement o f the
Rules: ’Rules and regulations fo r the con­
struction and classification o f offshore plat­
form s’.
The methods described and the criteria
used are based on the up-to-date results o f
the European research programme on the
fatigue strength o f welded joints fo r
offshore units and the w o rk performed in
ARSEM (Research Association o f the Be­
haviour of Steel Offshore Structures) to
which Bureau Veritas is associated.
The document fo r design offices defines
the procedures for:
- the calculation o f loads due to waves,
- the calculation o f stresses in joints,
- the calculation o f long term histogrammes
407
It provides information on the concept o f
S-N curves and gives the relevant data to:
- choose the necesarry S-N curves fo r
verification
- calculate the cumulative fatigue and de­
cide the acceptability o f the results
- minimize the risk o f fatigue in the design
and construction o f the units.
The document w ill be a valuable to o l fo r all
those in charge o f verifying the reliability
w ith respect to fatigue o f projects of
marine units o r installations.
Giassflake coatings
in arctic o f tro p ical w a te rs
Besides having good anti-corrosive prop­
erties Sigma C o ltu rie t Giassflake Coating
is proving remarkably resistant to impact
and abrasion damage - to such an extent
that it is now specified fo r ships’ main
decks, cargo decks and even cargo holds
and hatch coamings. It is also used fo r
w orking decks o f offshore rigs, the protec­
tion o f oil and petrol storage tanks, rail
hopper cars and numerous o th e r types of
equipment.
N ew areas o f use fo r C o ltu rie t Giassflake
Coating have exceeded the most hopeful
predictions; it has proven to be extrem ely
tough and has excellent resistance to abra­
sion damage caused by berthing, anchor
cables, tugs, etc. and to general mechanical
damage such as ice, hatches, containers and
heavy wear and tear. M oreover, it is highly
resistant to splash o r spillage o f a wide
range o f chemicals and oils. This quality is
also im portant fo r the protection o f sur­
faces in chemical plants, breweries, tan­
neries, etc., including drilling rigs.
C o ltu rie t Giassflake Coating is being parti­
cularly applied to such areas as sea chests,
boottopping, rudders, stern frames and
thruster tunnels, even fo r deck machinery,
fore and aft gangways, cargo and bunker
manifold, decks, hatches and many o the r
parts where most deck wear and damage is
encountered.
A C o ltu rie t Giassflake coating requires
mixing the base material w ith a hardener
and it can then be applied economically in
layers o f 500 microns o r more. Time re­
quired fo r a full cure w ill vary according to
the substrate tem perature but in average
conditions C o ltu rie t Giassflake can be
touch dry after only tw o hours and can be
overcoated in 16 hours at 20 °C, o r in 36
hours at a substrate tem perature o f
10 °C. Full cure at 10 °C take seven days
but only tw o days is required at 40 °C.
The holding prim er used is a highly special­
ist product which incorporates effective
anti-creep agents assuring b e tte r bonding
and preventing the electro-osmosis pro­
cess which is stimulated by cathodic pro­
tection systems should the coating be dam­
aged. Encouraging results in a variety o f
extrem e conditions have led to C o ltu rie t
Giassflake Coating being applied to
408
offshore service vessels, pipelaying barges,
and others where anti-corrosion but highly
durable coatings are necessary.
More information from : Sigma Coatings
BV. P.O. Box 42 1420 A A U ithoorn tel.
02975 - 41247.
are welding (powder).
- Solid wire-shielding gas combination.
- Flux-cored wires w ith o r w ith o u t shiel­
ding gas.
- D ifferent combination fo r special wel­
ding processes.
A p proved F iller Products
for Electric A rc W eld in g
Bureau Veritas has published a booklet
listing all approved Filler Products fo r Elec­
tric A rc W elding updated to A p ril 1987.
This booklet supersedes the 20th issue,
published in August 1986.
This booklet title d ’Approved Filler Pro­
ducts fo r Electric A rc W elding - 1987’,
2 1st issue, contains the follow ing chapters:
- Electrodes fo r manual arc welding.
- W ire-flu x combination fo r submerged
It refers to about 2325 products manufac­
tured by more than 200 manufacturers
around the w orld.
This booklet is one among the dozen
covering all Marine and Offshore materials
and equipment eligible to the Product
Type Approval and C ertification (TYPEC)
scheme o f the Society.
This booklet is available on request at:
Bureau Veritas, Coolsingel 75, 3012 AD
Rotterdam. Tel. 010-41 19733.
NEDERLANDSE VERENIGING
VAN TECHNICI OP
SCHEEPVAARTGEBIED
t
(Netherlands Society of Marine Technologists)
V o o rlo p ig P ro g ra m m a van
lezingen en e v e n e m e n te n in h et
seizoen 1987/1988
Im plicaties M A R P O L A n n ex I en II
voo r product- en
chem icaliëntankers
door E. Pieters van Gebr. Broere D o r­
drecht
di. 13 o k t„ 1987 Groningen
D e V e rb o u w in g van de Q ueen
Elisabeth I I * * *
door W . Ohlers M A N /B & W en door Ir. T.
van Beek en Ir. J. J. M. de C ock van Lips B.V.
Drunen
wo. 14 okt. 1987 Amsterdam
do. 15 okt. 1987 Rotterdam
In h et kielzog van ’W ille m B are n ts z’
door A. Veldkamp, gezagvoerder 'Plancius’
do. 15 okt. 1987 Vlissingen
O n tm o etin g sd ag M a ritie m e
Tech n iek
Dagbijeenkomst. Thema: M a ritie m e
Veiligh eid en P rivatiserin g
do. 12 nov. 1987 RAI Amsterdam
(zie inlegvel)
B ijzondere schepen
door Damen Shipyards
W o. 4 nov. TU D elft (voor afd. R’dam)
Di. 17 nov. Groningen
W o. 18 nov. Amsterdam
Do. 19 nov. Vlissingen
Berging ’H e ra ld o f F re e E n terp rise ’
door H. J. G. Walenkamp van Smit Interna­
tional
W o. 25 nov. ’87 T.U. D elft
N .B .:
D it programma zal in de komende maan­
den worden aangevuld en eventueel gewij­
zigd.
* Lezingen in samenwerking m et de N e­
therlands Branch van het Institute o f Mari­
ne Engineers.
* * Lezingen in samenwerking m et de afd.
Maritieme Techniek van het Kvl en het
Scheepsbouwkundig Gezelschap ’William
Froude’.
1. De lezingen in Groningen w orden ge­
houden in Café-Restaurant 'Boschhuis'
Hereweg 95 te Groningen, aanvang
20.00 uur.
2. De lezingen te Amsterdam w orden ge­
houden in het Instituut vo o r Hoger
Technisch en Nautisch Onderwijs,
Schipluidenlaan 20, Amsterdam, aan­
vang 19.00 uur. Vooraf gezamenlijk
aperitief en broodmaaltijd om 17.30
uur.
3. De lezingen in Rotterdam worden ge­
houden in de Kriterionzaal van het
Groothandelsgebouw,
Stationsplein
45, aanvang 20.00 uur. Vooraf geza­
menlijk aperitief en broodmaaltijd, aan­
vang 18.00 uur.
4. De lezingen in Vlissingen worden ge­
houden in het Maritiem Instituut ’De
Ruijter', Boulevard Banckert 130, Vlis­
singen, aanvang 19.30 uur.
SenW 54STE IA AR G AN G NR 20

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