Cutting cylinder oil costs without a break in service - Wärtsilä

Cutting cylinder oil costs
without a break in service
AUTHOR: Jürgen Gerdes, General Manager, Service Sales, Wärtsilä in Switzerland
Cylinder oil
daily tank
Filter and
measuring unit
FCM-20
ALM-20
Dosage pump
Servo oil supply unit
Lubricating oil drain tank
Lubricator
Fig. 1 – Arrangement of the Retrofit Pulse Lubrication System on one cylinder of
a Wärtsilä low-speed engine.
Pulse Lubricating Systems have
quickly become popular as retrofits
for Wärtsilä RTA and RT-flex low-
speed engines, and since summer
2006, complete systems have been
ordered for more than 80 engines.
After-sales service is more than just
supplying spare parts. Wärtsilä offers
a complete range of products and
proactive services to help customers
get the best results from their engines.
Wärtsilä’s centre for 2-stroke engines
in Switzerland provides customers
WÄRTSILÄ TECHNICAL JOURNAL 02.2007
with original equipment manufacturer
(OEM) spare parts, tools and
consumables, together with performance
optimization, modernization, and
operational support services.
Customers are moving their focus
more and more to performance
optimization, especially towards upgrades
or retrofits that result in immediate
fuel or lubricating oil savings.
For example, since March 2004, the price
of cylinder lubricating oil has increased by
some 250% with an average cost today of
about USD 1700 per tonne. Thus, on a 12cylinder
Wärtsilä RTA96C engine with a
68 MW output, even a modest cut of just
0.3 g/kWh in the cylinder oil feed rate can
result in annual savings of more than USD
200,000. Therefore, it was decided in early
2006 to accelerate development of the new,
electronically-controlled Pulse Lubricating
System (PLS) to make it available for
retrofitting to RTA and RT-flex engines.
PLS cuts cylinder oil consumption
without compromising piston-running
reliability by accurately metering and
precisely timing the oil delivery, and
improving the distribution of cylinder
lubricating oil to an engine’s cylinder
liners. It enables the guide feed rate
for cylinder lubricating oil to be cut
to 0.8 g/kWh in Wärtsilä RTA and
RT-flex engines retrofitted with PLS.
When, during the SMM exhibition in
Hamburg at the end of September 2006,
the Retrofit Pulse Lubricating System
(RPLS) was officially announced it attracted
much interest from shipowners. The first
retrofits were already on order before the
announcement, and by the end of August
2007, orders for more than 80 complete
engine installations had been received,
amounting to 850 cylinders. By mid-
August, 16 engines of both RTA and
RT-flex types had been successfully
retrofitted, while the first orders
had also been booked for RTA84C
and RTA84T engines.
The first retrofit went into service at
the beginning of September 2006. By
mid-2007, the RPLS had been released
for RTA96C, RT-flex96C, RTA84C
and RTA84T engine types while further
engine types will be added during 2008.
Retrofit installation
A retrofit is especially attractive to
shipowners if it can be undertaken without
disturbing commercial operation of the p
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vessel. Wärtsilä’s two-stroke center and the
Wärtsilä services network are thus working
in close co-operation to minimize the
required installation time so that RPLS can
be retrofitted in a ship while on passage and
during a normal port stay. For example,
Wärtsilä in Korea is manufacturing all
pipework and other mechanical parts.
Before dispatching the material to the
vessel, it is prefitted on a dummy in the
Wärtsilä workshop in Noksan, South
Korea, to verify that the work is correct.
RPLS is an independent system with few
connections or interfaces to other systems,
and utilizes the engine’s existing cylinder
liners. Thus preparation and installation
are easy and fast. All equipment, including
prefabricated piping, is supplied with
installation and commissioning work being
undertaken by Wärtsilä service engineers.
To a substantial extent this material
can be installed during the voyage,
thereby considerably reducing the
port time required for fi nishing the
installation and for the commissioning.
Installation of controls, pumps, wiring,
and interface connections to remote and
alarm monitoring systems, is executed
during the voyage. Ample attention is
paid to commissioning, fi ne adjustment
and the running-in of the RPLS in port
and during a confi rmation voyage.
The whole retrofit and commissioning
on the first vessel, the 7500 TEU container
ship “COSCO SHENZHEN” with a 12cylinder
Wärtsilä RTA96C main engine,
could be completed in five steps without
interrupting the vessel’s schedule:
1. Pre-inspection in Hong Kong
on 22 June 2006.
2. First installation trip from Hong
Kong to Yantian during 26–27
August. Installation work continued
in Yantian and during the Pacifi c
crossing to Long Beach (USA),
arriving there on 9 September.
3. The second and fi nal installation
period in Long Beach during 9–
11 September, included pistonrunning
related modifi cations.
4. The commissioning was carried-out
while on passage from Long Beach to
Oakland, where on 13 September the
final inspection was also carried out.
5. Finally, on her ‘maiden’ passage
to China, measurements and
documentation of the RPLS
performance were carried out.
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Cylinder oil tank
Alarm
monitoring
system
Filter WECS
Main
bearing
oil
Servo oil
supply unit
Junction
box
Pressure
sensors
Servo oil
overfl ow
Fig 2. – Schematic of the RPLS.
Working principle
The basic principle of the Pulse
Lubricating System is to deliver metered
quantities of cylinder lubricating oil
under pressure at precise timing exactly
into the piston ring package, from
where it is evenly distributed around the
circumference of the cylinder liner.
The RPLS is based on a lubricating
module for each cylinder with a dosage
pump and monitoring electronics,
which delivers pressurized cylinder
lubricating oil to newly developed
lubricators (formerly known as quills)
that fit existing cylinder liners of the
Wärtsilä RTA and RT-flex engine types.
Each lubricating module is equipped
with two separate supply lines – for
cylinder lubricating oil and servo oil.
A separate servo oil supply unit is
needed to drive the lubricating module
for RTA engines, whereas on RT-fl ex
common rail engines, the servo oil is
taken from the servo oil common rail
through a pressure reducing valve.
Once the Wärtsilä Engine Control
System (WECS) switches the 4/2-way
solenoid valve in the lubricating module
Lubricator
ALM-20
Dosage pump
Cylinder
CAN bus
Power supply
Cylinder oil
Servo oil
Servo oil return
to the open position, servo oil fl ows to
the drive side of the central piston of the
dosage pump in the lubricating module.
As the central piston is actuated, it feeds
cylinder lubricating oil from the lubricating
oil supply to the metering ducts, and then
discharges it from the lubricators at high
pressure. The cylinder oil is accurately
supplied at defined positions of the working
piston whose position is constantly detected
by the control system from the reference
signal given by the crank angle sensor. At
the end of the lubrication work cycle, the
directional valve in the lubricating module
directs the servo oil to the return-fl ow
side of the central piston of the dosage
pump, which then returns to its initial
position. The metering chamber is fi lled
again with cylinder lubricating oil to be
ready for the next lubricating cycle.
A separate servo oil supply unit is
provided for RTA engines. It includes two
gear pumps, one supplying the lubricating
module with servo oil taken from the
main engine oil system, with the second
pump as a standby. The oil supply unit
also includes a pressure limiting and safety
valve, pressure gauge, pressure sensor, and

Photo: Nordcapital
Pressure
sensor
Shut-off
valve for
lubricating oil
Cylinder
oil inlet
To system oil
drain tank
Relief valve
for servo oil
Shut-off valve
for servo oil
Fig. 3 – The RPLS lubricating module with lubricator connections and
associated electronics for eight lubricators.
WÄRTSILÄ TECHNICAL JOURNAL 02.2007
Cylinder oil
outlet to
lubricators
Venting plug for
cylinder oil
Venting plug
for servo oil
4/2-way
solenoid valve
Diaphragm
accumulator
Fig. 4 – One of the nine container ships managed by E.R. Schiffahrt, which have
been completely retrofitted with the Pulse Lubricating System. The ships are
powered by Wärtsilä RTA96C low-speed diesel engines.
shut-off valve. For RT-flex engines, servo
oil is drawn from the engine servo oil
system through a pressure reducing valve
by which the oil pressure is reduced from
200 bar to 50 bar. The reduced pressure
is monitored by pressure transmitters
directly connected to the alarm system; the
pipes are SOLAS compliant. The reduced
pressure can be adjusted and its level is
shown on an analogue pressure gauge.
The lubricating module for each
cylinder consists of a dosage pump, a
4/2-way solenoid valve, monitoring
electronics, pressure sensor, and diaphragm
accumulator on a base plate. The timed
lubricating module feeds a predefi ned
metered quantity of cylinder oil at high
speed to the lubricators at the precise
timing ascertained by the engine control
system. Part of the control oil fl ow from
the servo oil line is routed to the 4/2-way
solenoid valve. At the same time, the loaddependent
cylinder lubricating oil needs
of the respective cylinders are ascertained
by the engine control system, which sends
a corresponding signal to the monitoring
electronics of the lubricating module. The
ALM-20 (Advanced Lubricating Module)
checks that the dosage pump is working
correctly. The ALM-20 communicates
with the master control unit through a
redundant bus system, sends the signal to
the 4/2-way solenoid valve, and processes
the data from the pressure transmitter.
The redesigned lubricator delivers the
cylinder oil radially as compact oil pulse
feeds exactly into the piston ring package,
from where it is equally distributed around
the circumference of the cylinder liner.
The lubricators (up to eight) are arranged
around the liner in one row to ensure an
excellent distribution of the cylinder oil on
the cylinder liner. The vertical distribution
is governed by the lubricating oil injection
timing as a function of the crank angle.
A generously dimensioned 40micron
cylinder lubricating oil fi lter is
arranged before the lubricating modules.
It effectively removes any particles of
dirt, thereby ensuring reliable operation
of the lubricating modules. A 12 litre
buffer tank is provided with a scaled
sight glass that enables cylinder oil
consumption measurements of up to
five litres. The buffer tank also allows
the filter to be changed while the engine
is running. When the filter is dirty,
the integrated sensor gives a signal on
the excessive differential pressure. p
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Fig. 5 – Excellent service experience with the RPLS revealed by the piston ring
pack in an RT-flex96C engine after running with a cylinder oil feed rate of
0.8 g/kWh during shipboard trials.
Distant down
from joint
face, mm
Specific diametrical liner wear,
mm/1000 hours
Fig 6. – Specifi c diametrical
liner wear, mm/1000 running
hours, in one cylinder of the
12-cylinder RTA96C engine of
the “COSCO SHENZHEN” at
the second inspection at Long
Beach: measurement taken
fore–aft and port–starboard.
54 indetail
0.000 0.020 0.040
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
Fore – Aft
Port – Starboard
Control and monitoring of the Pulse
Lubricating System is provided by the
WECS engine control system, which is
based on the system used on Wärtsilä
RT-flex common rail engines. The
Advanced Lubricating Module (ALM­
20) units communicate with the master
control unit (FCM-20) by means of a
redundant bus system. All control modules
have a redundant power supply. When
a lubricating pulse is initiated by the
engine control system, the monitoring
electronics associated with the respective
lubricator activate the 4/2-way solenoid
valve. The lubricating pulse is triggered
electro-hydraulically as the pressure
sensor sends a check signal to the ALM­
20. When the pressure is within the
programmed range, the local signal
confirms that the lubricating cycle was
executed as specified. If, for instance, no
correct lubricating cycle is ascertained
owing to a fault such as a lubricator
blockage, a shortage of lubricant, a lack
of hydraulic drive power or a faulty shut
off-valve position, a local fault signal is
sent to the WECS engine control system.
The redundant SSI bus connecting the
FCM-20 to the crank angle sensor is part
of the retrofit package. The crank-angle
sensor is mounted on the intermediate
shaft and has built-in redundancy.
From the outset, considerable
thought and design work was put into
developing a cost-effective lubricating
system that can deliver the shortest
possible payback time. This required
that the RPLS is able to be retrofi tted in
the minimum working time on board
ship with cost-effective components.
Experience with RPLS
Since the fi rst retrofit, the “COSCO
SHENZHEN” has been visited by
Wärtsilä engineers several times, and
the cylinder lubricating feed rate was
reduced within two weeks to the target
level of 0.8 g/kWh from its original
setting of 1.36 g/kWh. The operating
results have been very good during the
6000 running hours so far accumulated.
“With its improved capability and
considerable cost savings, this new cylinder
lubricating system is a notable performance
improvement to the Wärtsilä engines, and
we look forward to rapid completion of
the series of nine retrofi ts”, said Willem
Dekker, Chief Operating Offi cer, of
E.R. Schiffahrt GmbH & Cie KG,
the Hamburg manager of “COSCO
SHENZHEN”, after reviewing the
service results at the end of 2006. In
the meantime, the whole RTA96Cengined
fleet of E.R. Schiffahrt has been
successful retrofitted with RPLS.
Overall, experience with RPLS has
been successful, and excellent liner
and piston ring conditions have been
recorded since the earliest tests. Before
the first commercial installation, trials
had been carried out both on the
Wärtsilä research engine in Winterthur,
and on shipboard engines.
The first RPLS test started on the
research engine in June 2003. Shipboard
testing began with an RTA58T engine in
September 2004, and later with an
RT-flex96C engine. Shipboard testing
has accumulated more than 20,000
running hours. Throughout, the
outstanding performance of the RPLS
was confirmed, with all testing being at or
below the guide feed rate of 0.8 g/kWh.
The Pulse Lubricating System
is now established as a worthwhile
retrofit for Wärtsilä RTA and RT-fl ex
engines, and it offers ship owners and
operators substantial savings in operating
costs without disturbing the normal
operating service of their ships.