C.P. PROPELLER SYSTEMS OF THE "EUROLINER" CLASS VESSELS
By
C.C. Schneiders
Vice-President
LIPS N.y. Propeller Works
Paper read at inaugural meeting of
The Institue of Marine Engineers,
Netherlands Branch
Table of contents
Page
Abstract 3
ntroduction 3
Main characteristics of ships and propulsion groups
Design work 5
14 C.p. propeller systems description 8
Operating experience 11
C.P. Propeller Systems of the ''Euroliner'' Class Vessels.
Abstract.
The twin screw gasturbine driven container ship Euroliner and subsequent vessels have drawn considerable attention in the technical press as well as from ship operators all over the world. (n this paper, attention is given to the controllable pitch propeller systems. The lay-out of the shaftl me
is treated and details of interest are given. Finally, the experience obtained with the systems during 0 months of service at sea is discussed.
1. Introduction.
'Euroliner'' and her sister ships constitute the first series of commercially operated merchant marine vessels, which are equipped with the progressive type propulsion train formed by gasturbines driving controllable pitch propellers.
Operating in the container trade between N. Europe and the U.S.
Atlantic Coast, her sister ship the G.T.S. Eurofreighter'' was
awarded the 'Blue Riband' trophy for its new transatlantic speed-record made during a crossing from New York to Europe at a speed of 27.1 knots [i]
With the appearance of these ships on the high seas, the aircraft
derivativemarinegasturbinec.p. propellerconfigurationas
aneconomical proposition in specialized cargo vessels, has emerged from its former experimental stage onto a more mature level [21
[]
,[]
In the 50's, industrial type gasturbines where installed in the tanker ''Auris'' and in the Liberty ship ''John W. Sergeant''. The ships were
relatively successful with their new propulsion train but no shipowner in the world was induced to install gasturbines in his ships. In 1967,
the 'Adm. Wm. M. Cal laghan'' was commissioned. This experimental twin screw ship is propel led by two gasturbines each driving a monobloc propeller through a reverse-reduction gear.
With the mechanically highly loaded propel 1ers involved, ''Eurol mer'' and her sister ships are only a short step behind similar frigate and destroyer type propulsion applications. The first series of naval ships
equippedwithall G.T.-C.P.P. combinations, beingordered early 1966, were recently commissioned to the Royal Canada Navy [5] , [6]
This paper gives a description of the controllable pitch propeller systems and information on operational experience.
2.
Main characteristics of ships and propulsion groups.General design.
The ships have been designed by John J. McMullen
Ass.
and built by Rheinstahl Nordsee Werke, Germany, for Scarsdale Shipping Co. Ltd., a subsidiary of J. and J. Denhoim Ltd. and they are on long term charterto Seatrain Lines of New York. The hulls have very fine lines and the ships look particularly graceful for container ships of this class,
The ships are equipped with FT14A-12 gasturbines of Pratt & Whitney, one
per shaftl me, each driving a Lips controllable pitch propeller through a De Schelde reduction gear, table 1.
So far, these units are the most powerful c.p. propeller systems now in service, fig. 2.
Bowthruster.
Each ship is equipped with a 1,000 HP/238 rpm. electrically driven bowthruster with controllable pitch propeller. The thrust delivered at full power is about 11,000 kg. The bowthrusters are of low noise
design, i.e. ''crackling'', ''rattling'' and ''thundering'' have been
reduced as much as possible.
fig. 1.
The main dimens ions are:
Length overall 2143,14 m (798-6'')
Length between pependiculars 2214,95 m (738'-'')
Breadth moulded (max.)
30,5
m (ioo'-")Depth of Upper Deck
19,20
m ( 63-0'')Drauglît (designed)
9,906
m (32-6")
Deadweight 28,/432 t
(816 x 140'
containers)Why gasturbines?
Selection of gasturbines as the main source of propulsive power has been the subject of investigation since many years. The pros and cons of such a configuration may be known in a general sense. The decision to use aircraft derivative gasturbines in these ships has been taken after consideration of all possible trade-offs involved. lt reflects the costs side of investment, maintenance and operation of a fleet of ships
in the overall scope of a container transportation system, consisting of sea-transport, shore handl ing and distribution systems. The high fuel consumption of approximately 300 ts of gasoil per day, which so far has prohibited appl ication of this type of propulsor in other
systems, has been integrately considered in the overall scope of cost
[21.
Some of the aspects considered in this project, involving total economics,
are:
- exceptional high util ization, based on reliability, ease of maintenance and repairs and quick interchange of a complete gasturbine.
- reduction of the ship's complement; the engine installation is ideally suited for automation and thus for unattended operation.
- extremely compact and low-weight installation benefits the cargo carrying capacity, resulting in abt. l0 additional containers. - improved rnanoeuvrability.
3. Design work.
Orders for the propellers were given in February and June 1969.
Design work was completed in November 1969. Deliveries took place in August 1970 for the first ship and November 1971 for the last ship,
table 2.
Hydrodynamic design.
Prel iminary hydrodynamic design studies were conducted by the
University of Michigan in 1968. The propellers were finally designed and tested by the Netherlands Ship Model Basin in close co-operation
with Lips N.y.. Several configurations of propeller positions were investigated,
[8]
One configuration was seriously considered, i.e. overlapping propellers. It is interesting to note that a ship with overlapping propellers was
The advant!ges were considered to be: - better elficiency of the propellers,
- enginerocm located more aft and shorter in length,
- short shafting, enabl ing the use of c.p. propellers with the well tried system of the push-pull rod.
lt was finally decided to choose for the conventional twin screw arrangement with long shafts for the following reasons:
- the gain in efficiency with overlapping propellers for this ship was
considered to be insignificant to run other risks, amongst which those
connected with novel structural concepts.
- uneven dynamic loading of shafting and c.p. propellers and risk of
vibrations and interference phenomena for the overlapping arrangemen:.
- superior steering properties for the conventional arrangement.
As could be expected, it appeared that the propellers were rather susceptible to cavitation. Considerable attention and additional design work and
testing was required to ascertain cavitation free operation. Because of the danger for windmill ing during crash-stop procedures, special
consideration was required of the blade contour, rateof pitch change
and propeller characteristics in off-design conditions. The remote control
system was programmed such as to avoid this effect. Simulations were made for various manoeuvres with pitch reduction when, consequently,
risk for overspeeding of the gasturbine exists.
Mechanical design.
lt is clearly recognized that reliablec.p. propeller systems, capable
of high levels of performance, are primarily achieved as a result of continuous research and development of advanced component concepts
over a period of many years, backed up by operational experience. C.p. propel 1er systems of this power level and with this shaft length
had not been built before, requiring extension of component technology. New design work had to be carried out, starting from evaluation of experience with previous systems through establishing new design
criteria to verification test programs on components, equipments and the complete system. This resulted in a total effort of almost 10.000
manhours, including preparation of production drawings.
Various sy;tem concepts were being considered in the preliminary design phase, connected with the different propulsion configurations. The
rather than a push-pull rod with inboard cylinder version, was largely influenced by the very long shafting. Both versions have been built in thousands in the past with good results. So discussions about technical merits are superfluous. Push-pull rod versions of similar power, though physically somewhat smaller, have been installed in naval ships. The coupling connecting the tailshaft to the tube shaft then has to transmit thrust, torque and the pitch control forces in the rod. This would
result in a sizable semi-detachable coupi ing, which could not be housed within the dimensions of the sterntube of the present ships. Consequently, a S.K.F. oil injection type muff coupl ing was -selected as a component part of the c.p. propeller installation with cylinder in the hub. This
coupl ing only has to transmit thrust and torque. Yet, the S.K.F. coupling required was of a size beyond the existing range at the time and had to be specially developed.
In order to give an impression about sizes of the equipment, some data are listed in tables 3 and L4 Total weight of shafting, gearbox and gasturbine amounts to aproximately 310 tons. lt is interesting to note that the weight of a cathedral type diesel engine of same power would be
in the order of 1,000 tons.
Torsional characteristics were calculated as usual. Extensive elastic
line calculations were carried out by Lips to optimize the bearing reactions.
Whirling characteristics were calculated by the yard for various configurations. As a result, the aft part of the tailshaft had to be
appreciable increased in diameter 5'' and 8' respectively in excess of A.B.S. rules resulting ¡n abt. 30'' and 35'' diameter respectively.
Remote control
The servo-unit with follow-up hydraulic valve is connected to an A.E.G. remote control system. There are two modes, i.e.
- Sea mode, in which the gasturbine ¡s power control led. Shaft speed is
free.
Shaft speed control cannot be accepted because of resulting thermal load variations at full rpm.
- Manoeuvring mode, in which pitch and shaft speed are maintained at preset values. Fuel injection now ¡s a dependent parameter.
In the sea mode, the shaft speed depends on temporary values of pitch and gasturbine load. The dynamic values of pitch and load can result ¡n unacceptable values of shaft speed, e.g. during windmill ing.
Under those conditions, safety requirements must overrule the control system. Therefore it is essential that an extra control loop is foreseen.
During a crash-stop manoeuvre, when windmilling will cause the tendency
for the shaftspeed to become excessive, this control loop ensures that
pitch is reduced stepwise. All critical manoeuvres were simulated on
the computer. Fig. 3 shows results of simulations with various control
sequences at two rates of pitch change. A more general treatment of this subject is given in reference [io]
. C.p. propeller systems description.
Hub.
The hub is cast in one piece, blades are connected to blade-carriers by
means of bolts, fig. .
Blades and blade-carriers are actuated by an axially moving
cylinder-yoke through a single slot-pin mechanism. Slots are located in the blade-carrier. Yoke-pins on the moving cylinder are acting on the blade carrier slots through sliding blocks of special bronze, fig. 5. With this lay-out, the blade spindle torque capability of the mechanism
increases at larger pitch angles, so that in the full ahead pitch
condition maximum spindle torque is available. The piston in the
cylinder is fixed against the forward side of the hub through a piston
rod.
When high pressure oil is pumped to the forward side, the cylinder-yoke is moving aft, thereby moving the blades forward and increasing pitch. Piston rings act as seals between cyl inder and piston. Medium pressure
oil, pumped into the aft part of the cylinder, causes the blades to
move backwards. It should be noted that the hydraulic high pressure oil
compartment is completely surrounded by low pressure lubricating oil.
This oil is kept under pressure by a head tank. Each blade foot is sealed against the hub by a special but simple and rei jable blade seal of
synthetic rubber.
Tailshaft and tubeshaft.
The hub is secured to the aft flange of the propeller shaft by means of bolts and dowels, protected by a flange cover. This cover ¡s
provided with synthetic rubber seal rings and filled with mineral grease.
The tailshaft is connected to the tubeshaft by means of an S.K.F. oil
The shafts contain two co-axial pipes, connected to the cylinder-yoke and to the feedback mechanism of the servo-unit. The pipe insert is pressure-compensated and transmits the blade position to a mechanical feedback system, thereby not changing in length under pressure variations. One hydraulic channel is connected to the forward side of the cylinder, the other one to the aft side. The surrounding channel provides the
lubrication oil for the hub mechanism.
Emergency feature.
An extra pipe is attached to the main pipe insert, Through this pipe oil can be pumped to an emergency piston contained in the aft part of
the tailshaft. A hand pump can be inserted in one of the feedback rods
of the servo-unit. The emergency piston can be pumped aft thereby
moving cylinder-yoke and pipe insert aft in order to fix the pitch in a
suitable ahead position.
Servo-un i t.
The main functions of the servo-unit are oil supply into the running shaft and feedback of the blade position. The maximum pressure in the hydraulic system ¡s 120 bar or 1,700 p.s.i.
High pressure oil supply presents no problem at small shaft diameters. it can be provided by means of an annular pressure chamber around the rotating shaft and narrow slots adjacent to this chamber. Part of the oil will bleed away while passing the slots. Waste of oil is prevented by means of low pressure lip-type seals. The leakage oil is
returned to the tank. The high pressure seals, being plain journal bearings, are clearance seals. The low pressure seals are tight, non-clearance
seals. This method has the advantage of being extremely simple and reliable, requi ring only a small number of parts. The construction is not subject to wear.
The problem really appears at larger shaft diameters, as has been described in reference [iii . Then the sealing process is affected by mechanical deformations. Under the influence of the oil-pressure, the oil supply block swells, and the bearing clearances increase to such an extent that too much oil bleeds away, so that the supply of oil to the
cylinder becomes inadequate. Pressure compensating chambers are introduced to balance the mechanical distortions of the oil supply block.
Fig. 9 shows how these pressure compensating chambers are arranged.
As there ¡s neither metallic contact nor other material contact in the
high-pressure sealing section, this device is essentially free from wear, and no provisions for spare seals need to be made.
The feedback ring ¡s mechanically connected to a box fitted in the
ship. This box contains the hydraulic follow-up valve system and the
connections to the A.E.G. remote control system.
There are two hydraulic pumps of 50 HP for each c.p. propeller system.
These three-worm-type pumps are made by 1MO, Sweden. The hydraulic
valves used in the system, such as four-way valve, pressure relief valve, back pressure valve and non-return valves, are provided by Vi ckers.
Main functions.
When the development and design work for the c.p. propeller systems
had to be carried out, an important part of the attention was given
to the main functions. Areas of possible uncertainties were listed,
such as:
- the six prime reliability objects in c.p. propeller systems, ref. [12] blade attachment
pin-slot mechanism blade suspension
blade foot seal ¡ng
hub-shaft attachment
rotary high-pressure oiltransfer
- cavitation at blade root or at outer radii,
- blade spindle torque and resulting hydraulic oil pressures, - windmill ing during manoeuvring,
- undesirable pitch run-away effects resulting in overspeeding,
- instabilities in the hydraulic system and accuracy of pitch setting, - vibrations in the system.
Blade attachment bolts were a point of concern of the American Bureau of Shipping with respect to strength and qual ity. These bolts are made of stainless steel containing 25°/e chromium and 7°/e nickel. This is an excellent material of a forged quality, both strong, ductile and
corrosion resistant, contrary to many other steels being either
5. Operating experience.
According to the experience of the ships managers, the propellers have performed well in all ci rcumstances [13] . In operating
c.p. propeller systems, this is not a surprising and accidental merit. No matter how thorough the initial design has been engineered, it
is understood that building c.p. propel 1ers on this scale is
associated with certain risks in new and unknown engineering areas. it is therefore proper to report that no problems in such areas have been encountered.
The Eurol mer'' now is 1,5 year in operation. The accumulated number of hours steamed by the four ships together, is approximately
20,000 hours.
The ship speed turned out to be fully satisfactory, as was the propeller efficiency.
No vibrations were noticed anywhere, whereas the noise level in the aft ship was very low, even at maximum power.
Manoeuvrabi I ity turned Out to be extremely good.
The ships reacted very quick and precise, also at speeds in excess of 15 knots in confined waters when the propellers assist rudderaction. During a crash-stop from 29 knots with intermittent pitch change,
action of propellers and controls resulted in a headreach for 'Asialiner' of only 1160 m.
Although there were no problems in new and unknown engineering areas,
it cannot be denied that there have been some failures of minor character in conventional engineering areas:
An early problem occurred, namely overheating of the hydraul ic oil during summertime in port.
Then the oil temperature raised to the alarm setting of 600 C
Insufficient oil-cool Ing in the bottom hull-tank caused this phenomenon. lt could be overcome by incorporating a small cooler in the system.
The blade spindle torque on the third and fourth ship turned out
to be somewhat higher than predicted. The hydraul ic pressure,
therefore,had to be raised from 100 to 120 bar, to ensure reliable operation.
During trials, in one ship a failure of hydraulic pump thrust bearing occurred, which was cured by a design modification.
It appeared that in one hub the piston rings where manufactured to too
Having made the diagnosis, the cure itself was easy, although the
hub had to be opened up. It ¡s interesting to note that this was carried Out while the ship was afloat.
Guarantee docking.
Hubs and blades were in good condition.
Cavitation at the blade root has not been observed while insignificant
cavitation erosion has been found on two blades at the outer radii. This could easily and def initively be rectif ied.
Some corrosion was observed on the Lidrunel blades due to galvanic action. Apparently, the shafts were very well aligned and floating
in oil. A potential difference between shaft] me and ships' hull of 350 mV was measured later on. The remedy here simply is the insta] lation of proper grounding equipment.
Although two ships have touched bottom resulting in blade tip damage,
the blade bolts appeared to be in excellent condition and the blade
attachment was fully intact.
Observations.
Instability in the hydraulic system and the mechanical feedback has not
occurred. Pitch remains stationary under all conditions when alterations are not required. Accuracy of pitch setting is very well within the
required tolerances. Despite the long shafting, creeping of pitch has not been observed. As mentioned before, the pipe insert in the shafting
is pressure compensated, while temperature effects practically do not influence the pitch setting since there is almost no oil flow in the shaftl me.
Rotary high-pressure oiltransfer into the 2/i»' diameter servo-shaft at 1700 p.s. i. did not present any problem under operating conditions.
During a crash-stop procedure from full speed ahead, the propellers
of these ships will show the, by now well known, windmill effect.
During some time, when reducing pitch,the propellers are driven by the
water, because of the high speed of the ship. In turn, the propeller
will speed up the gasturbine, which will trip, without any effect on
the too high shaft speed. This phenomenon has been avoided by taking
special precautions in the remote control system, i.e. by reducing
pitch in steps, fig. 10. Crash-stop manoeuvres during trials have
shown the necessity and proper action of te extra control loop, which introduced stops at 21
,0
and 1L1°.Undesirable increase of shaft speed from full rpm. ma also occur because of pitch run-away. This may well lead to serious damage to the propulsion group, particularly to the gasturbine. lt could be caised by pipe break down or unwanted stopping of hydraulic pumps. The remdy is to design the blades in such a way that at full pitch the hydroynamic part of
the blade spindle torque cannot overcome the friction part, fig. 11.
Now the pitch will remain stationary at hydraulic power loss. Full scale tests confirmed that the blades were properly designed for this purpose.
6. Conclusions.
- C.p. propeller systems of this power and size are practical. They perform very well in all circumstances and respond perfectly under manoeuvring and under sea conditions.
- There ¡s every reason to bel leve that larger units can be designed, built and installed.
- In order to be able to build larger
systems, sufficient know-how, experience and engineering back up must be available.
- Overall design success of such a venture can only be achieved by co-operation of all principals involved.
References.
[i] Maritime Reporter and Engineering News, July 15, 1972.
''Seatrain Line' Euroliner'', Marine Engineering/Log, June 1971.
'The G.T.S. Euroliner", Maritime Reporter/Engineering News,June 1,1971.
[1+] Riback, M., ''Gas Turbine Experience in Container Ship Service'',
Diesel & Gas Turbine Progress, November/December 1971.
Benn, D.H., ''Propulsion Plant for the DDH-280'', Canadian Shipping & Marine Engineering News, March 1969.
Sachs, R.M., "Description of Propulsion System for DDH-280 class gasturbine destroyers'', Naval Engineers Journal, February 1970. Sunley, A.N. and Patterson, G.A., ''DDH Control System'',
Society of Naval Architects and Marine Engineers, Eastern Canadian Section, February 1970.
Kerlen, H., Esveld, J., and Wereldsma, R,,
Propulsion, Cavitation and Vibration Characteristics of overlapping Propellers for a Container Ship''.
nternational Shipbuilding Progress, June 1972.
Hundred Years Flensburger Schiffbau - Gesellschaft.
SS ''Bhandara'' (1896) - Twin-screw vessel with overlapping propellers.
Hansa, 1972, nr. 13.
[io] Pronk, C., ''Selection and Simulation of Marine Propulsion Control
Systems", International Shipbuilding Progress, 1972.
[ii] Wind, J., ''The development of Controllable Pitch Propeller
Systems'',
Lips Technical Presentation Day, September 1971. Diesel & Gasturbine Progress, November.December 1971.
Drenth, B.W., "Rel iabi i ity of Controllable Pitch Propel 1ers",
International Shipbuilding Progress, 1972. O'Hare, T.L.R., and Hoiburn, J.G.,
''Operating Experience with Gasturbine Container Ships", Paper read for The Institute of Marine Engineers,
Table 1, Data of propel 1ers.
Material of hubs and blades 'Lidrunel'', a high-tensile Al-Mn bronze.
Table 2, Schedule.
Name of ship SHP Shaftspeed
rpm. Propeller diameter ub ciameter Number of blades 'Euroliner''
6,150
mm. 1,830 mm. 2 x 30,000 135 '4 ''Eurofreighter' 20' - 2 6' - 0'' ''Asialiner'' 6,200mm. 1,9140mm. 2 x35,000
135 14 ''Asiafreighter' 20' - 14'' 6' - 14''Name of ship Propellers
ordered Propellers del ivered Ships delivered Guarantee docking
''Euroliner'' Febr. '69 Aug. '70 March '71 April '72
'Eurofreighter Febr. '69 Jan. '71 July '71 July '72
''Asial mer'' June '69 July '71 Febr. '72
--Table 3, Length of shafting.
Hub 7'
Tailshaft
52'
Tube shaft Lf3'
Servo-unit 9'
Two intermediate shafts 5L4'
Total length from propeller to gearbox 165'
Table , Weight of shafting.
Hub and blades 37 tons
Tailshaft 68 tons
S.K.F. coupling 7 tons
Tube shaft 39 tons
Servo-unit 11-t tons
Two intermediate shafts 35 tons
Total weight of shafting 200 tons
Gearbox 95 tons
Gasturbine, including sound insulating box 15 tons
Fig. 2. Shafting arrangement of ''Asialiner".
!.r-IrUJ
Ii U1i Ii.
138 132 CAP PISTON
-z
Fig. . LWH C-hub. /2 13 14 15 1 17 78 /2 20 t [SEC]Fig. 3. Rpm. versus time for various rates of pitch change and control
sequences Computer simulations.
PROPELLER BLADE PISTON ROD EMERGENCY PISTON FLANGE COVER BLADE CARRIER MOVING CYLINDER-YOKE 21 22 23 2'- 25 NUMBER ÛFPIJMP3 PD WER REJD 70 STRRT PTPITCH R(WC/N 2 I 2 f I IDLE IDLE IDLE IDLE SDÛHP
5HP
t'o
t3
t3
¿.0t.D
---NDNE
2 3 4 5 ¿ 7 8 g to 11 12 A , 114 'Dût
l-iii
iii ii
I
'r
- JÌ
Fig. 7 Part of shaftline.
Compensating ring Pressure chamber
Ficj. 9 Oil supply block with compensatinq rings.
rIME
Fig. 11 Blade spindle torque.
Fiq. 12. Servo-unit installed.
