The S-Separator

Technical information for mineral oil treatment

Inside view

3

Summary

4

The Alfa Laval S-Separator Systems

Conventional cleaning with purifier systems
Separation results with purifiers
Limitations common to conventional purifiers
Limitations common to conventional clarifiers

8

The ALCAP technology

Operating principle
Medium free water contamination
High free water contamination
Transducer MT 50 operating principle
Dielectric constant – approximate values

11

The separator

Design features

14

Flow diagram

16

Separation performance

Factors influencing separation efficiency
System layout
Separation efficiency test method
Separation Performance Standard

19

Remote operation

This technical information deals with the S-Separator which
provides the highest separation efficiency for mineral oil treatment
ever achieved.

The Alfa Laval S-Separator

2 Alfa Laval Marine & Diesel Equipment

Alfa Laval Marine & Diesel Equipment 3

The Alfa Laval S-Separator

Summary

The Alfa Laval S-Separator is an automated single-stage separation system
for the cleaning of fuel oil and lubricating oil.

Based on the well established ALCAP™ technology, this
compact system consists of a high-speed separator and
ancillary components together with control system and
starter box. It can be delivered in a fully integrated modular
design on its own base plate or, to facilitate delivery, as six
individual components that can be assembled on site.

Available in a full range of sizes and in different configurations,
the S-Separator delivers higher cleaning efficiency than pre-
vious models and drastically reduces operation and main-
tenance costs.

Innovations include:

• a compact separator bowl which reduces sludge produc-

tion and loss of oil,

• a new disc stack design to ensure optimal flow patterns

and separation characteristics,

• the non-threaded CentriLock™ spring lock ring which is

easy to snap on and pop out, and,

• the CentriShoot™ discharge system, which replaces the

sliding bowl bottom with a patented, flexible discharge slide
that is fixed within the bowl body.

The purpose of this document is to provide technical infor-
mation about the Alfa Laval S-Separator system. This includes
information about the separation process, advances in system
design, system benefits and a description of equipment.

Benefits
Highest separation efficiency available. In laboratory tests,
the Alfa Laval S-Separator removes over 85 percent of all
5-micron particles to ensure fuel and lubricating oils do not
contain harmful contaminants. This effectiveness measures
up to the Separation Performance Standard.

Low installation costs. Compact, modular, flexible design
saves space and reduces installation costs.

Faster, more secure commissioning with full technical support
during design, installation and startup – even for retrofits.

Big savings on operation and maintenance costs. The
S-Separator provides continuous monitoring of clean oil,

reduces sludge by up to 75 percent, and minimizes wear
and tear on the bowl. Compared to previous separator
models, the spare parts inventory has been reduced and the
service intervals prolonged.

Easy-to-access, easy-to-operate equipment provides auto-
matic, start-and-forget systems that are designed for remote
control and operation.

No adjustments required to the gravity disc or other system
components for continuous optimum separation efficiency
despite fluctuations in density and viscosity.

Proven key components provide more uptime, high reliability,
consistent performance and low maintenance.

Longer service intervals. Longer-lasting construction prolongs
service intervals and reduces spare parts consumption by up
to 50 percent compared to conventional systems.

The Alfa Laval S-Separator

4 Alfa Laval Marine & Diesel Equipment

The Alfa Laval S-Separator Systems

The Alfa Laval S-Separator is the principle component of a range of high-
efficiency mineral oil separation systems. Based on proven ALCAP™ oil treatment
technology, the Alfa Laval S-Separator combines fuel oil and lubricating oil
treatment into a single separator, thanks to software that makes it possible to set
the relevant parameters in the process controller.

The Alfa Laval
S-Separator.

The Alfa Laval S-Separator system can handle:

• Heavy fuel oils with high densities up to 1010 kg/m

3

and

viscosity up to 700 cSt/50°C. Handling of higher viscosity
is available upon request.

• Lubricating oils for all diesel engine types.

• Distillates and light diesel oils (MDO).

The Alfa Laval S-Separator systems consist of a separator
and its ancillary components, together with control system
and starter box. It can be delivered in two ways:

1. as the Alfa Laval Separator Ancillary (SA) system, which

consists of six individual components that can be assembled
on site to facilitate delivery, or,

2. as the Alfa Laval Separator Unit (SU), which is a fully inte-

grated modular system on its own base plate.

Both systems include:

• an high-speed S centrifuge,
• an EPC50 process controller,
• an MT 50 transducer (capacitive transmitter), and,
• ancillary equipment.

Alfa Laval Marine & Diesel Equipment 5

The Alfa Laval S-Separator

SU – Separation Unit

Easy to work with but occupying only a minimum volume,
the plug-and-play Separation Unit integrates a separator
and ancillaries with a control cabinet and starter box. With
all components pre-installed on a single base plate, you
save installation time, materials and space.

SU Module

The plug-and-play SU Module combines a Separation Unit
with a heater and feed pump. This makes it a complete oil
cleaning system and an optimum solution for protecting
your engine. Double and triple configurations are also avail-
able, each mounted on a single base plate with all of the
interconnecting piping.

To further simplify the design process, 3-D AutoCAD drawings for all separator configurations are available in electronic format.

SA – Separation Ancillaries

A non-integrated solution, the SA separation system lets
you minimize your initial investment by assembling it on site.
Specialized block components let you determine the
arrangement, and each component is pre-tested to ensure
a perfectly working system.

Water block

Oil block

EPC50 control unit

Air block

Optional starter

Sludge outlet kit

The Alfa Laval S-Separator

6 Alfa Laval Marine & Diesel Equipment

840

950

970

991

Fuel density kg/m

3

at 15°C

Interface position sensitivity

Figure 1. Interface position’s sensitivity.

840

950

970

991

Fuel density kg/m

3

at 15°C

Gravity disc capability

Figure 2. Capability of the gravity disc to cope with disturbing factors.

Figure 3. Purifier problem area.

Purifier
problem
area

Interface
sensitivity

PURIFIER

PURIFIER + CLARIFIER

ALCAP FOPX

Fuel
density

Gravity disc
insufficiency

960

991

1010

+

Conventional cleaning with purifier systems
Conventional cleaning plants are based on purifier type
separators. Practical operation has clearly proven that the
generally accepted maximum density limit for fuel oil is
991 kg/m

3

at 15°C. This maximum density limit may be

exceeded at bunkering, which may result in operational
difficulties with the cleaning plant.

Consequently, the purifier type of separator restricts the use
of available fuel oils. For lube oil cleaning, the conventional
purifiers are still an option.

Separation results with purifiers
To achieve optimum separation results using purifiers, the
interface between oil and water in the bowl must be outside
the disc stack.

The interface position of a purifier is adjusted by means
of gravity discs. To get the correct interface position the
purifier must be fitted with a correctly sized gravity disc.
This presents an operational dilemma with changing oil
properties.

With higher fuel densities, maintaining optimum separation
results by means of gravity discs becomes increasingly diffi-
cult. Factors that affect the interface position are changes in
oil density, viscosity, feed flow rate and temperature.

With increasing fuel density, the interface position
becomes progressively more sensitive to these factors
(Figure 1).

Unfortunately, gravity discs experience the same progressive
sensitivity to these disturbing factors. The capability of the
gravity disc therefore declines progressively with increasing
fuel density (Figure 2).

Thus, as the interface position becomes more sensitive to
disturbing factors, each successive gravity disc has a
reduced capacity to cope with them (Figure 3). In practice,
problems with the purifier develop well before the fuel density
reaches 991 kg/m

3

.

Temperature fluctuations, inherent in even the best tempera-
ture control systems, cause viscosity fluctuations. However, a
proportional integral (PI) temperature controller will consider-
ably reduce this source of disturbance.

Alfa Laval Marine & Diesel Equipment 7

The Alfa Laval S-Separator

Limitations common to conventional purifiers
The basic problem in treating heavy fuel oil is the gravity disc:

• It restricts the use of diesel engine fuels to those with

a maximum density of 991 kg/m

3

at 15°C.

• Optimum separation depends on selecting the correct

gravity disc, which corresponds to the prevailing density,
viscosity, feed flow rate and temperature. This becomes an
impossible task in practical operation with the fluctuation of
density and viscosity, particularly with high-density fuels of
991 kg/m

3

at 15°C and above.

• Checking and fitting the gravity disc is time-consuming and

unpleasant. Since the correct gravity disc is defined as the
largest disc that does not cause a broken water seal, it can
be a frustrating trial-and-error process. Alarms for broken
water seals can be frequent. Consequently, the gravity disc
selected tends to be undersized and the oil cannot be
adequately cleaned in a purifier alone.

• To ensure satisfactory cleaning a second separator is

required in series operation. This creates a separation
system of a purifier followed by a clarifier as a safety net.
This system, however, is still restricted to oils with a
maximum density of 991 kg/m

3

at 15°C.

Limitations common to conventional clarifiers
The basic problems when treating fuel oil of any density in a
clarifier are oil losses and limited water handling capability.

Oil losses
When operating a separator in clarifier mode, no displace-
ment water is added prior to sludge discharge. Therefore, not
only sludge and separated water are discharged, but a cer-
tain volume of oil is discharged, too.

Limited water handling capability
For optimum separation efficiency separated water must
not enter the disc stack. The separated water can only be
discharged with the sludge through the sludge ports at the
bowl periphery since the water outlet is closed in a conven-
tional clarifier (Figure 4).

If a clarifier is used without a purifier in the first stage and
with elevated water content, sludge discharge occurs
frequently at short intervals because no other method of
discharging separated water exists.

Sludge discharge causes turbulence in the bowl and
therefore discharging sludge too frequently decreases
separation efficiency. Consequently, the water handling
capability of a conventional clarifier is insufficient for
cleaning fuel oil.

Water outlet
closed

Figure 4. Conventional clarifier water discharge.

The Alfa Laval S-Separator

8 Alfa Laval Marine & Diesel Equipment

Oil

Sludge
and water

MT

Water

Disc stack

Water
transducer

Figure 6. High free water contamination.

The ALCAP technology

Operating principle
Dirty, pre-heated oil is continuously
fed to the S-Separator, which essen-
tially operates as a clarifier. Clean oil is
continuously discharged from the clean
oil outlet. Separated sludge and water
accumulate at the periphery of the
bowl.

When separated water approaches
the disc stack, traces of water start to
escape with the cleaned oil. This minor
increase in water content of the cleaned
oil is detected by the transducer MT 50,
which is installed in the clean oil outlet.

Increased water content in the
cleaned oil is a sign of reduced sepa-
ration efficiency not only of water, but
of solid particles too.

The transducer continuously measures
changes in water content. No absolute
values of water content or volume are
involved. The transducer measures the
deviation from a non-calibrated refer-
ence value and transmits a signal to the
EPC50 process controller for inter-
pretation. Measurements that fall within
the permissible deviation values are
known as the trigger range.

The EPC50 process controller stores
a new reference value after the trans-
ducer stabilization time that follows
every sludge discharge sequence has
elapsed. During the reference time the
best possible separation result is
obtained.

At the trigger point, which is when the
water content in cleaned oil reaches
its maximum allowable deviation of
approximately 0.2 percent, the EPC50
process controller initiates an automatic
discharge of the water that has accu-
mulated in the separator bowl.

Figure 5. Low free water contamination.

Alfa Laval Marine & Diesel Equipment 9

The Alfa Laval S-Separator

Depending on the amount of water
in the oil, water is discharged either
through the water drain valve, or with
the sludge through the sludge ports at
the periphery of the bowl.

Medium free water contamination
When separated water approaches the
disc stack the transducer signal triggers
the EPC50 process controller to open
the water drain valve.

High free water contamination
When excessive amounts of water are
present in the feed and if the water
drain valve activation does not provide
sufficient drainage, the EPC50 process
controller automatically initiates a
sludge discharge.

Transducer MT 50 operating principle
The transducer includes a cylindrical
capacitor through which the full flow of
cleaned oil passes, forming a dielectric
medium. The working principle of the
transducer exploits the large difference
between the dielectric constants of
mineral oil and water.

Dielectric constant
– approximate values
Mineral oil

2–4

Water

80

The dielectric constant of oil contami-
nated with water increases when the
water content of the oil increases, and
vice versa. Changes in the dielectric
constant of the cleaned oil are very
sensitive, convenient measures of
changes in its water content.

MT

Transducer

Figure 7. High free water contamination – water drain valve activated.

Figure 8. High free water contamination – sludge discharge.

The Alfa Laval S-Separator

10 Alfa Laval Marine & Diesel Equipment

Alfa Laval Marine & Diesel Equipment 11

The Alfa Laval S-Separator

The separator

With its unique design features, the centrifugal separator incorporated in the
range of S-Separators is the most advanced separator ever produced for the
marine and power industries.

Longer intervals between service have a positive effect on
overall life cycle costs compared to those of previous sepa-
rator models.

All components, from the simple belt drive to the design of
the new bowl, have been thoroughly tested both in laboratory
trials and in rigorous field tests under normal and forced
operating conditions.

Drive
The separator is driven by an electric motor via a flat belt to
the spindle that is supported in the frame by bearings and
special composite springs. No tensioning of the drive belt is
required.

This configuration provides reliability and long intervals
between service.

Bowl
The bowl, which is fixed at the top of the spindle, contains
the most advanced changes found in the separator.

Fluid dynamics studies have been extensively used in the
design to ensure the best possible flow patterns. This is
especially true in the case of the disc stack, which has been
optimized to provide high separation characteristics and to
help keep the bowl free from sludge deposits.

The bowl has a simple paring tube, instead of the conven-
tional heavy phase paring disc, that “floats” on the surface
of the heavy water phase. This patented paring tube system
minimizes oil losses and enables use of the same bowl
configuration on all fuel and lube oil types.

As with all bowls using ALCAP technology, no adjustments
are necessary and no gravity discs are fitted.

Because of its high speed and advanced design, the bowl
is appreciably smaller than those of previous separator
models for a given capacity requirement. This compact bowl
is a factor that contributes to the small overall size of the
separator.

Figure 9. The S-Separator.

Paring tube

Seal ring

Discharge
ports

Discharge
slide

CentriLock

Untreated oil

Clean oil outlet

Water outlet

Figure 10. Separator bowl.

The Alfa Laval S-Separator

12 Alfa Laval Marine & Diesel Equipment

Discharge system
The separator operates with the new CentriShoot

®

discharge

system. The sliding bowl bottom of previous models has
been replaced by a discharge system that uses a patented,
flexible discharge slide that is fixed in the bowl body.

During discharge, only the outer periphery of the disc flexes
downward exposing the discharge ports. The frame of the
separator easily absorbs the impact forces in the sludge.

Because of the smaller bowl volume, longer intervals between
sludge discharges and more accurate controls, the new
system provides efficient sludge removal but with less oil loss,
lower water consumption and less total waste production
than previous models.

CentriLock™ lock ring
In the new separators, a simple snap-in spring lock ring, for
which patents have been applied, has replaced the traditional
threaded lock ring, the lock ring spanner and the sledge-
hammer.

The bowl is assembled and then compressed, using the
mechanical disc stack compression tool that comes with the
S-Separator. This enables the spring lock ring to snap easily
into place.

Removal is equally simple. An Allen key loosens grub
screws set into the outer wall of the bowl and the lock ring
pops out.

STEP THREE

: After discharge, the slide moves gently

back into position, closing the ports. Closing is done
hydraulically, without any springs.

STEP TWO

: During sludge discharge, the edge of the

slide flexes downward, exposing the ports.

STEP ONE

: CentriShoot’s discharge slide is fixed at the

centre. During separation it covers the discharge ports.

Figure 11. CentriShoot discharge system.

CentriLock can be removed with only an Allen key.
No sledgehammer is necessary.

CentriLock lifts out and snaps in easily – without any
threads to wear.

Threaded lock rings

must be removed with
a sledgehammer. Over
time, metal-to-metal
wear between bowl
and lock ring lead to
expensive bowl repair
or replacement.

Figure 12. CentriLock lock ring.

Inlet/outlet parts
The inlet/outlet parts of previous models consisted of several
parts that required individual assembly. These individual parts
have been replaced in the new separator by a single housing
to which the inlet/outlet hoses are connected.

When opening the separator, the hoses are disconnected first
and secured to one side for reconnection. The entire housing
can then simply be removed as a single piece.

Ancillaries
The system can be delivered either pre-assembled as a
single compact pre-tested unit that includes the separator
and ancillary unit mounted together, or as loose block-
mounted components with the separator and ancillaries as
individual units.

Ancillaries system
Good engineering principles have yielded improvements in
the new ancillaries unit compared with the ancillary systems
supplied with previous models. Instead of having to connect
several different components, the new ancillary system con-
sists of three blocks.

The main block consists of the inlet and outlet connections,
control and regulating valves, temperature and pressure
transmitters, and the water transducer built into a single
block.

The two smaller blocks for operating water and air
are connected as the unit is built.

Six pipe connections are required for the S-Separator:

• Oil inlet

• Clean oil outlet

• Oil recirculation outlet

• Operating water

• Operating air

• Sludge outlet.

Sludge Removal Kit
for use with the Separation Unit
Thanks to the new discharge system it is no longer
necessary to have a large sludge tank under the sepa-
rator. Instead, a very small intermediate sludge tank can
be mounted on the base plate between the separator and
the ancillaries unit.

The intermediate sludge tank is equipped with a level
switch and an air-operated pump that pumps away the
sludge after each discharge. The tank is also equipped
with a connection for a small vent pipe to the nearest tank
ventilation. The Sludge Removal Kit provides flexibility in
the placement of a separation unit.

EPC50 process controller
The control cabinet for the separator unit combines the motor
starters and the process controller into a single unit. However,
the separator ancillary system requires the process controller
to be installed in a separate cabinet.

Maximum reliability and user-friendliness were among the major
design considerations for the new EPC50 process controller.
In addition, the EPC50 introduces several new functions that
are now available due to changes in the instrumentation.

Pressure transmitters have replaced pressure switches in the
ancillaries unit, providing a higher degree of accuracy and reli-
ability. They also supply the process controller with a contin-
uous stream of information.

Instead of the message codes used in previous systems, the
new unit provides information in clear language in a rolling
text window. Eight different languages are provided as stan-
dard, enabling the operator to select the language of choice
at the initial start-up. Further support for the rolling text mes-
sages is provided in the Instruction Book.

In rigorous tests over many years, the process controller has
proven to be stable and the light-emitting diode (LED) display
legible under conditions of high humidity and temperatures of
55°C and above. The EPC50 has been granted approval
from many classification societies.

Alfa Laval Marine & Diesel Equipment 13

The Alfa Laval S-Separator

Figure 13. EPC50 process controller.

The Alfa Laval S-Separator

14 Alfa Laval Marine & Diesel Equipment

Feed Pump
Feeds unprocessed oil to the
separator.

Heater
Heats unprocessed oil to the
separation temperature.

Temperature transmitter
Measures the oil temperature and
signals the process controller.

Pressure transmitter, oil
Measures the pressure in the oil
inlet, and signals the process
controller.

Pneumatically controlled
changeover valve
Leads the untreated oil to the
separator, or back for recirculation.

Process controller
Supervises the S-Separator.

Pressure transmitter, oil
Measures the pressure in the oil
outlet and signals the process
controller.

Transducer
Continuously monitors changes in
water content in the oil outlet and
signals the process controller.
Provides a “separation efficiency
check”.

Flow diagram

Conditioning water

Opening water

Closing water

Water inlet

Untreated
oil inlet

Oil
return

Optional

PT

TT

Alfa Laval Marine & Diesel Equipment 15

The Alfa Laval S-Separator

Regulating valve
Regulates the back-pressure
in the clean oil outlet.

Pneumatically controlled
shut-off valve
Closes the clean oil outlet.

Solenoid valve block, water
Distributes separator
opening/closing water and
conditioning water.

Separator
Cleans the oil by removing water
and solid particles.

Pressure transmitter, water
Measures the pressure in the water
drain outlet and signals the control
unit.

Drain valve
Opens when water is drained from
the separator.

PT

MT

PT

Clean oil outlet

Water outlet

EPC50 Control Unit

Sludge outlet to sludge tank

or Sludge Removal Kit

Separation Unit

Separation performance

Catalytic fines introduced during the refinery process of heavy fuels can cause
premature wear of components and engine breakdown. Therefore, good
separation performance is imperative.

Factors influencing separation efficiency
Several factors influence separation efficiency, such as:
• Separation temperature
• Separation viscosity
• Feed rate
• Utilization of the disc stack
• Densities of the light phase (oil) and heavy phase (water)
• Size and number of solid particles in the feed
• Amount of water in the feed
• Chemical characteristics of the oil

System layout
Single-stage operation is the normal operating mode, which
generally provides sufficient separation efficiency.

Fuel oil varies considerably in terms of viscosity, density and
the amount of solids, water and other characteristics present.

On those occasions when the fuel oil contains elevated levels
of abrasive wear particles and/or water, parallel operation

splitting the feed rate equally between the two separators is
recommended to maintain sufficient separation efficiency.

Series operation will not improve the separation efficiency
to the same degree as parallel operation. Consequently, the
S-Separator cannot be operated in series configuration.

Lube oil is not subjected to variations in viscosity and density,
therefore a correctly sized separator in single-stage operation
that is properly operated fulfils the requirements to achieve
the desired separation result.

Separation efficiency test method
One of the major challenges facing the development team
was the lack of a reliable method for testing the separation
efficiency of the new separator during the various stages of
the development work. This required a method that closely
approximated normal operating conditions, but would provide
accurate and reproducible results to establish a standard
separation efficiency test method.

The Alfa Laval S-Separator

16 Alfa Laval Marine & Diesel Equipment

0

1

2

3

4

5

6

0

20

40

60

80

100

Separation vs. flow rate

Flow rate [m

3

/h]

Separation [%]

5

µm particles

Figure 14. Separation of plastic particles versus flow rate in an older Alfa Laval model.

Alfa Laval Marine & Diesel Equipment 17

The Alfa Laval S-Separator

In the early 1980s, Alfa Laval carried out separation efficiency
tests using a typical fuel oil.

Both before and after separation, the levels of contaminants,
expressed as aluminium and silica, were measured both by
weight and by particle size using a particle counter. These
tests indicated separation efficiencies for particles greater
than 5 micron in the region of 70 to 80 percent for ALCAP
separators. The tests also showed that a single ALCAP
separator could replace the traditional purifier/clarifier in
series operation.

Instead of catalyst fines, monodisperse spherical plastic
particles size 5 micron are used. This is relevant with respect
to the tolerances found in fuel injection and engine lubrication
systems. These particles are produced to very exact dimen-
sions and densities.

In typical laboratory tests, the prepared mixture of synthetic
oil and plastic particles is heated to a temperature that provides
the same viscosity as fuel oils (380 and 700 cSt @ 50°C)
when heated to the normal separation temperature of 98°C.
The material is then fed through the separator at different
feed rates, and samples are taken at fixed intervals after a
discharge.

The method demonstrated that the test could produce
consistently reproducible results for a given set of conditions.
The test therefore was considered suitable as a highly accu-
rate test method to determination separation efficiency.

Typical data from test results show a gradual decrease in
separation efficiency as flow rate increases (Figure 14).

Good correlation was also found between this method and
separation tests carried out at 98°C on a sample of fuel oil
containing catalyst fines.

It is known that separation efficiency is a function of capacity
and that, if capacity is raised, then separation efficiency will
decrease. To maintain separation efficiency when capacity is
increased, improvements must be made to the separator in
order to provide the desired separation efficiency at the
increased capacity (Figure 15).

Despite the fact that modern bunkers often have good
quality and contain low amounts of catalytic fines, under-
dimensioning separation systems is inexcusable.
Occasionally, highly contaminated bunkers or bunkers with
poor separation characteristics may occur. Other parameters,
such as separation temperature and the cleanliness of the
disc stack, fluctuate.

To maintain a safe margin against poor separation perfor-
mance, even during such conditions, a separation system,
which is amply over-dimensioned for easy treatment of
bunkers, is required. This may be regarded as an insurance
fee that pays off during demanding conditions, such as when
other systems do not perform satisfactorily and lead to costly
engine wear and unreliable operation.

Similar reasoning applies for lube oil systems. Although
the characteristics of the oil do not vary much, other para-
meters can have noticeable influence on the separation
efficiency. It is important to dimension the system for the
worst-case scenario. Otherwise unacceptable engine wear
can result.

0

20

40

60

80

100

Flow

Separation [%]

Impr

oved

Decrease in separation
efficiency due to increased
recommended capacity
without improved design.

Old

Old r

ec. cap

Incr

eased r

ec. cap

a

c

b

Figure 15. Illustration of the effect of increased flow design in a separator.
a) Old point of operation.
b) After increasing capacity without change in design.
c) Improved design gives high efficiency of increased flow.

The Alfa Laval S-Separator

18 Alfa Laval Marine & Diesel Equipment

Separation Performance Standard
Establishing a separation performance standard enables:
• Fair comparison of different separators,
• Good reliability of the diesel engine, and,
• Economical operation of the diesel engine.

Of all the contaminants contained in residual fuels, the
most damaging are catalytic fines. These are hard, abrasive,
irregularly shaped particles of aluminium silicate, which must
be removed, or at least reduced, to acceptable levels before
the fuel oil is injected into the engine. If cat fines remain,
they can lodge in injection pumps, piston rings and cylinder
liners, causing serious wear that can over time lead to break-
downs.

According to ISO 8217 standards, the maximum allowable
cat fines in bunkered fuel is 80 parts per million (ppm).
However, because engine builders typically stipulate a
maximum of 15 ppm in fuel oil, fuel oil is rigorously cleaned
by centrifugal separation before it enters the engine.

Currently, fuel oil separator selection is based on the
Maximum Recommended Capacity (MRC) tables provided
by the manufacturers. It is known that separation efficiency
is a function of the separator flow rate. Generally, the higher
the flow rate, the higher the number of particles that remain
in the oil, and the lower the separation efficiency. But as the
flow rate is reduced, particle removal increases and cleaning
efficiency improves. It is, however, essential to know at what
capacity adequate separation efficiency is reached in the
typical case.

There is no recognized reproducible method for measuring
the relationship between capacity and separation perfor-
mance. Therefore no one can be absolutely sure that separa-
tors chosen according to the MRC actually provide safe
removal of harmful catalytic fines from the heavy fuel oil
before injection into the engine.

Fuel system suppliers do not believe that it is possible to
compensate for poor separation or to provide adequate back
up to ensure separation performance by installing a fine filter
downstream of the separator. The filter would only capture
particles of 10 micron or more, while smaller cat fines that
remain would pass through the system. Centrifugal separa-
tors can remove particles as small as two micron.

In cooperation with several classification societies, Alfa Laval
has provided a de facto standard for independent verification
of separation performance based the DNV-approved Dyno
Test Method. This is an alternative to specifying separator
performance based on the MCR; the new standard is
expressed as Certified Flow Rate (CFR).

A separator’s CFR is the throughput rate at which 85 percent
of 5 micron monodispersed plastic particles, which simulate
harmful catalytic fines, are removed from the test oil, which
simulates a high viscosity fuel oil. The CFR represents a safe
level for continuous, efficient separation and provides the
industry with independent verification of separation perfor-

mance. This makes it possible to compare fuel oil separators
based on separation efficiency rather than on throughput
capacity.

With CFR measured for every separator, customers can
specify a unit of the correct size for the task, with the knowl-
edge that the installed unit will suit its intended purpose and
eliminate the risk of installing an undersized unit.

Because catalytic fines are not available in any standard size
distribution, it is impossible to create a standard based on the
evaluation of tests using real cat fines, or real heavy fuel oil.
Fuel oils also vary in terms of chemical characteristics, which
affect the polarity, and physical characteristics such as
density and viscosity.

Due to these wide variations, it is impossible to obtain repeat-
able and comparable results from tests made on actual
bunkers. The 5 micron monodispersed plastic particles, or
Dynospheres, are identically sized, homogeneous, spherical
plastic particles, normally used for the calibration of instru-
ments.

The development of the Separation Performance Standard is
positive for the shipping industry as a whole. For the ship
owner, the overall benefits are clear: different separators can
be compared on equal terms based on a reliable independent
international performance standard.

The owner may find that investment in a larger separator is
required when basing selection on CFR. This, however, can
be compared with buying a separator with an insurance fee
against damage to the engine caused by inadequate separa-
tion. Analyses indicate that a reduction in engine wear of as
little as two percent makes the selection of separators
according to CFR a profitable investment. At a given flow
rate, a larger separator will always provide higher separation
performance than a smaller one.

Remote operation

Unlike previous systems, the S-Separator has several options for remote
operation. This has been made possible due to built-in safety features,
such as a speed sensor and a vibration sensor.

Alfa Laval Marine & Diesel Equipment 19

The Alfa Laval S-Separator

Depending on the installation, the alternatives for remote con-
trol include:

• Bus communication that enables up to nine systems to be

connected as a network. Installation of the customer’s own
software package enables remote operation. A MODBUS
or PROFIBUS board must be installed in each EPC50
process controller.

• An additional EPC50 control panel (remote operator panel)

that can be installed for local operation or for operation
from an alternative location.

• A simple remote operation version that uses two switches

connected to an I/O expansion board.

• A junction box that can be installed on the S-Separator to

enable positioning of the control cabinet at a location away
from the separator itself.

Each alternative provides safety interlocks to prevent acci-
dental operation in un-safe conditions.

REMIND
As standard, each complete delivery of the S-Separator
includes a REMIND software package for local monitoring
only, a short connecting cable and an operating manual.
This allows the operator to install the program disks on a
laptop computer that is then connected to the EPC50
process controller. REMIND can then review and store the
alarm history and the processing parameters in the laptop.
This data may be used later to check processing conditions
and for troubleshooting.

Full instructions for the installation of the various systems are
given in Instruction Books.

Figure 16. Remote control network version.

The Alfa Laval S-Separator

20 Alfa Laval Marine & Diesel Equipment

The Alfa Laval S-Separator is ideal for new building
applications as well as for replacing older separator
units or supplementing existing cleaning systems.

Its compact size easily fits into available space in an
existing engine room. It can also be divided into four
parts in order to facilitate transport through small
passageways.

In addition, the pipe connections for the separator
units enable greater flexibility for the placement of the
unit; the units no longer need to be located over the
sludge tank or in the same place as the unit it is
replacing.

Alfa Laval supplies each S-Separator with full docu-
mentation either as paper copies or as PDF (Portable
Document Format) files on a CD-ROM. Documentation
is clearer and easier to understand, thanks to improved
graphics. The instruction manual, which can also be
made available in most major languages, covers:

• Safety
• System description
• Operating instruction
• Parameter list
• Alarms and fault finding
• System reference/installation instructions
• Service manual
• Spare parts catalogue

Documentation

Alfa Laval ensures that the S-Separator fulfills the
requirements of all major classification societies. Upon
request, Alfa Laval delivers each S-Separator with an
individual test certificate. This includes approval by the
society of the main components as well as workshop
testing of the complete module. Most key
components are also type approved by the leading
classification societies.

Alfa Laval provides spare parts kits for all service and
maintenance needs. Global technical service, training
and support are available throughout the lifetime of the
S-Separator.

Retrofitting

Classification
society approval

Spare parts,
service and
support

Alfa Laval reserves the right to make changes at any time without prior notice.

Any comments regarding possible errors and omissions or suggestions for improvement
of this publication would be gratefully appreciated.

Copies of this publication can be ordered from your local Alfa Laval company.

Published by:

Alfa Laval Tumba AB
Marine & Diesel Equipment
SE-147 80 Tumba
Sweden

© Copyright Alfa Laval Tumba AB 2004.

EMD00049EN 04

10

Alfa Laval in brief

Alfa Laval is a leading global provider
of specialized products and engi-
neering solutions.

Our equipment, systems and services
are dedicated to helping customers
to optimize the performance of their
processes. Time and time again.
We help our customers to heat, cool,
separate and transport products
such as oil, water, chemicals, bever-
ages, foodstuff, starch and pharma-
ceuticals.

Our worldwide organization works
closely with customers in almost 100
countries to help them stay ahead.

How to contact Alfa Laval

Contact details for all countries are
continually updated on our web site.
Please visit www.alfalaval.com to
access the information.

www

.fotoskrift.se

2004