Guidance for Lubricating Oil Management

7/26/2019 Guidance for Lubricating Oil Management

1/29

Copyright 2003 by NYK LINE All rights reserved

Guidance for Lubricating Oil Management

(Main Engine System Oil)

2003

NYK Line

Technical Group

Maritime Technology Team


2/29

Copyright 2003 by NYK LINE All rights reservedi

Table of contents

Introduction .......................................................................................................................... 1

Chapter 1: System Oil Management for Slow-Speed Engines .............. .............. ............. ..... 2

1. Characteristics of system oil for slow-speed engines.........................................................2 2. Balance of system oil circulation .......................................................................................2

2.1 Lubricating oil for replenishment and drip oil entering system oil .................................3

2.2 Leaked lubricating oil and drawn out lubricating oil......................................................3 3. Onboard system oil management ......................................................................................4

3.1 Maintaining a proper amount of system oil...................................................................4 3.2 Maintaining properties of system oil ............................................................................43.3 Economical Efficiency .................................................................................................5 3.4 System oil analysis .....................................................................................................53.4.1 Purposes of system oil analysis................................................................................5

4. Standard Values for Lubricating Oil Management ..............................................................6 4.1 Standard Values for System Oil Management ..............................................................6

5. Items to be checked for system oil management ...............................................................9 5.1 Density .......................................................................................................................95.2 Kinematic Viscosity .....................................................................................................9

5.3 Flash Point..................................................................................................................95.4 Water Content .............................................................................................................9 5.5 TBN (Total Base Number)..........................................................................................10 5.6 TAN (Total Acid Number) ........................................................................................... 115.7 Insolubles ................................................................................................................. 115.8 Metal......................................................................................................................... 115.9 Ferrography .............................................................................................................. 11

Chapter 2: System Oil Management for Medium-Speed Engines................ .............. .......... 12

1. Characteristics of system oil for medium-speed engines .................................................12 2. Balance of system oil circulation .....................................................................................12

2.1 Lubricating oil for replenishment................................................................................122.2 Lubricating oil for consumption..................................................................................13

3. Onboard system oil management ....................................................................................13 3.1 Maintaining a proper amount of system oil.................................................................13 3.2 Maintaining properties of system oil ..........................................................................143.4 System oil analysis ...................................................................................................14

4. Standard Values for Lubricating Oil Management ............................................................16 4.1 Standard Values for System Oil Management ............................................................16

5. Items to be checked for system oil management .............................................................16 5.1 Density .....................................................................................................................165.2 Kinematic Viscosity ...................................................................................................16 5.3 Flash Point................................................................................................................17 5.4 Water Content ........................................................................................................... 175 .5 TBN (Total Base Number).........................................................................................185.6 TAN (Total Acid Number) ........................................................................................... 185.7 Insolubles .................................................................................................................18 5.8 Metal.........................................................................................................................18 5.9 Ferrography ..............................................................................................................18

Chapter3: Economical System Oil Management for Slow-Speed Engines .............. ............ 19

1. Replenishment method for system oil.............................................................................. 192. Replenishment with only new oil .....................................................................................19

2.1 Guide for implementation .......................................................................................... 193. Re-use of stuffing box leaked oil .....................................................................................19 4. Use of Low Viscosity Oil .................................................................................................21

4.1 Guide for implementation .......................................................................................... 214.2 Use of Low Viscosity Oil............................................................................................21

5. Replenishment ratio of recycling oil and low v iscosity oil .................................................22 5.1 Reuse of recycled oil (stuffing box leak oil)................................................................235.2 Make up with low viscosity oil ....................................................................................24 5.2 Make up with low viscosity oil ....................................................................................25


3/29

Copyright 2003 by NYK LINE All rights reserved1

Introduction

With the ever-increasing degradation of marine fuel oil and the successive introduction of

high-output propulsion engines, system oil management for diesel engines has continued to undergo

gradual changes.

Although engine manufacturers, oil companies, and ship owners have established their own

standards for system oil management, some of their standards are merely specifications based on

their experience and have not been sufficiently examined from a technical point of view. For

slow-speed engines, it is necessary to adopt a management method in accordance with the actual

condition of system oil because contamination of used cylinder oil (the so-called drip oil) continually

increases with the adoption of high-power, supercharged engines. Meanwhile, for medium-speed

engines, more meticulous (careful) management is needed because system oil is directly affected by

combustion gas and/or ingress of combustion residues, which cause heavy fouling.

Therefore, standard values for system oil management are significantly affected by engine

design and the purification of lubricating oil, and it is presumed that this tendency will continue in

the future.

With such situation being prevalent, NYK has continuously conducted surveys on the properties

of system oil for main engines and has considered establishing an optimum system oil management

method capable of responding to changes in oil conditions.

This guidance explains the following items:

System Oil Management Method for Slow-Speed Engines

System Oil Management Method for Medium-Speed Engines

Items to be checked Limit values: The highest or the lowest value for use

Economical System Oil Management Method for Slow-Speed Engines

The purpose of this guidance is to provide an effective oil management system.

Needless to say, the major objective of lubricat ing oil management is to minimize engine

failures and to maintain safe operation of the vessels. In the meantime, we are required to maintain a

cost-conscious view and to strive to contribute to the economical operation of the ship by reducing

consumption of lubricating oil. Therefore, it is important to combine safe operation of vessels with

economical ship operation.

We hope this guidance will be used by all concerned for the consequent safe operation of

vessels.


4/29


Chapter 1: System Oil Management for Slow-Speed Engines

1. Characteristics of system oil for slow-speed engines

On two-stroke cycle slow-speed engines of the crosshead type (slow-speed engines) the cylinder

space and the crankcase are separated so that the system oil does not directly make contact with the

combustion chamber and the combustion gas. Cylinder oil, which is different from system oil, is fed

into the cylinder liners.

A characteristic of system oil for slow-speed engines is that a fouling continues as a result of the

ingress of used lubricating oil. Cylinder oil, after lubricating the cylinder liner, drops along the liner

wall and remains in the space under the piston. Some of the dropped cylinder oil mixes into the

system oil through the stuffing box. The amount of mixed cylinder oil depends upon the type of

engine and the maintenance conditions of the rings, however, in general the higher the turbocharging

and the greater the wear on the stuffing seal rings, the larger the amount of mixed cylinder oil.

The design of the stuffing box also has a significant effect on the amount of oil entering into the

system oil. Meanwhile, lubricating oils used in slow-speed engines (crosshead type) are rarely

affected by acid materials and/or oxidation.

Therefore, the main point of system oil management for slow-speed engines is to take measures

to prevent contamination by drip oil. More specifically, system oil management is to be carried out

by placing emphasis on changes in kinematic viscosity and TBN.

2. Balance of system oil circulation

A balance of system oil for slow-speed

engines is illustrated in Figure 1-1. The squares

with a solid line in Figure1-1 indicate lubricating

oils replenished or mixed into the circulating

system, while the squares with a dotted line

indicate lubricating oils leaked or drawn out

from the circulating system. The amount of

new oil / drip oil makes up for the quantity of

lubricating oil leaking/drawing out of the

circulation system and as a consequence the total

amount of system oil is usually maintained at the

same level.

On an older type of engine, the amount of

new oil is larger because the amount of drip oil is

relatively small. As a result, the properties of

system oil are almost the same as those of new oil. On the contrary, on a high-power,

high-supercharged engine, the amount of drip oil is large while the amount of new oil replenished is

small.

As a result, the properties of system oil will deteriorate compared to an older type of engine.In particular, when the values of kinematic viscosity and TBN increase significantly, drawing out of

system oil in use is needed.

Fig.1-1 Balance of system oil (Low-speed)

Lanternrecess drain

Otherleaked oil

Drip oil(Leaked oil)

Cylinder oilinjection

Drawingout

Sump Tank

Separatorleaked oil

Replenishment,

ContaminationLeakage, Drawing

Replenishmentof new oil

System

oilStorage

tank

Stuffing boxdrain

Separator


5/29


2.1 Lubricating oil for replenishment and drip oil entering system oil

(1) Replenishment New oil / Reuse oil

1) New oil is replenished at periodic intervals.

2) Reuse oil, drip oil leaked from the seal rings on the stuffing box, is sometimes used together

with new oil.

3) Ensure that enough new system oil, desirably the entire amount of system oil being circulated

that can be replaced at least once, is kept at all times in order to deal with any unexpected

accidents during which an entire amount of system oil would need to be replaced.

(2) Drip oil

1) This is the used lubricating oil entering the crankcase from the space under the piston through

the stuffing box seal rings.

2) The properties of drip oil vary with the type of engine and the cylinder feed oil ratio, however,

it is presumed that drip oil has almost the same property values of lantern drain oil, which are

shown in Table 1-2.

2.2 Leaked lubricating oil and drawn out lubricating oil

(1) Stuffing box leaked oil

1) This is leaked-off oil (used lubricating oil and system oil) from scraper rings on the stuffing box

and is led away to a drain.

2) Stuffing box leaked oil chiefly refers to system oil from the crankcase scraped off by the sets of

rings on the stuffing box and returned to the recycling tank. It has similar properties to the

original system oil as shown in Table 1-1.

3) Re-use may be possible for this oil after the oil has been treated in the purifier.

Table 1-1: Properties of Stuffing Box Leaked Oil and System Oil

Items

Density

(g/cm3)

Kinematic

Viscosity

(cSt @40)

Water

(%v/v)

TBN

(mgKOH/g)

Insolubles

in Pentane

(%m/m)

Leaked oil (range) 0.8865~0.9255 100~160 0.02~1.5 6.5~30 0.01~2.6

Leaked oil (average) 0.9064 126 0.20 16.5 0.33

System oil (average) 0.9041 123 0.14 14.4 0.11

(2) Lantern drain oil

1) This is the used lubricating oil (contaminated oil) remaining in the bottom of the scavenge

space, where it is drained away via the scavenge drains.

2) On modern engines the same drain line is generally used for the stuffing box leaked oil and the

lantern drain oil. In such a case, re-use is not possible for the stuffing box leaked oil.

Table 1-2: Properties of lantern drain oil

Items

Density

(g/cm3)

Kinematic

Viscosity(cSt @40)

Water

(%v/v)

TBN

(mgKOH/g)

Insolubles

in Pentane(%m/m)

Insolubles

in Toluene(%m/m)

Properties 0.948~0.966 185~300 0.5~1.0 48~60 1.5~2.5 0.5~2.0


6/29


(3) Drawn out system oil

1) When constant deterioration of the system oil is observed (when the amount of drip oil is large),

conduct drawing out operations at periodic intervals.

2) Temporary drawing out is an effective remedy for sudden deterioration in properties of the

system oil.

(4) Leaked-off oil from purifier

1) This is the lubricating oil drained out from the purifier when cleaning.

(5) Other leaked-off oil

1) This is the lubricating oil leaked from the flanges on the piping.

3. Onboard system oil management

3.1 Maintaining a proper amount of system oil

1) Carry out replenishment or drawing out in a timely manner to maintain a proper amount of

system oil at all times.

2) System oil tends to be affected by fouling when the total amount of system oil decreases.

3) In general the amount of system oil for low-speed engines is approximately 14m3 / 10000kw

(10m3 / 10000PS).

4) Attention should also be paid to the amount of new oil.

(Ensure that enough new system oil, desirably the entire amount of system oil being circulated

that can be replaced at least once, is kept at all times)

3.2 Maintaining properties of system oil

3.2.1 Replenishment and Drawing out

1) Carry out replenishment or drawing out in a timely manner to keep the property values of the oil

within the recommended standard values.

2) Determine the optimum amount of replenishment or drawing out based on the results of

periodic analysis.

3) Except in an emergency case, when the values of kinematic viscosity and TBN can be

maintained within the standard values, other properties can also maintained.

4) Properties of the system oil are affected to varying degrees by the engine load, wear on the seal

rings on the stuffing box, and the amount of cylinder feed oil. Therefore, these factors should be

taken into account when maintaining system oil.

3.2.2 Treatment by purifier

(1) Carry out system oil treatment with the purifier.

1) Bypass purifying

a. Set the oil flow rate for the purifier to approximately 1700 lit/h /10000kw(1300 lit/h/10000PS).

b. Set the oil flow temperature between 80 and 85.

c. For a total blow type purifier, set the cleaning interval to two hours or less because calcium

compound, a main ingredient in additives, is liable to become hard if two hours is exceeded.

(2) Entire quantity purifying


7/29


Treat all of the system oil during a docking period when the main engine is stopped for a

prolonged period of time.

a. Transfer all of the system oil to the lubricating oil settling tank and purify it by circulating it

through the purifier. In addition, clean the lube oil sump tank.

b. Set the heating temperature in the tank to approximately 80 .

c. The oil flow volume through the purifier is to be adjusted to between two and three times the

entire amount of system oil. (With 10m3 of system oil, for example, the oil flow volume would

be between 830 to 1250 lit/h)

3.3 Economical Efficiency

(1) New oil replenishment is to be minimized. The quality of the system oil can be maintained in optimum

condition if a larger amount of new oil is supplied, however, economical efficiency will be small.

(2) When considering economical efficiency, the target value should be close to the upper limit of the

standard value range. More meticulous management is required.

**** Target value for system oil management ****

a. Kinematic Viscosity: Upper limit minus 5 cSt

b. TBN : Upper limit minus 5 mgKOH/g

(3) Re-use of stuffing leaked oil is to be considered.

Re-use of stuffing leaked oil is available when values of system oil are kept with only new oil

replenishment. In this method, new oil must be used together with stuffing leaked oil.

Replenishment with only stuffing leaked oil should be avoided.

**** Guide line for stuffing leaked oil ****

a. Kinematic Viscosity: Upper limit minus 10 cSt

b. TBN : Upper limit minus 10 mgKOH/g

3.4 System oil analysis

1) Request shore laboratories to make analysis at regular intervals.

2) When conducting shipboard analysis, check the accuracy of shipboard analysis results by

comparing the results to shore analysis.

3.4.1 Purposes of system oil analysis

1) To determine whether the system oil is usable or not

2) To assess current conditions of the engine (for example, detection of abnormal wear on the

bear ing)

3) To review whether the management method for system oil is appropriate or not

3.4.2 Analysis interval

1) When no problem is observed: every six months or shorter2) When a problem occurs: during trouble and every one to three months after occurrence of the

trouble


8/29


3.4.2 Sampling

1) Samples (oil actually circulating through the system) are to be taken from the sampling cock or

the air vent valves on the cooler, the pump, and the filter.

2) Prepare a clean container for sampling.

3) Sampling is to be conducted after the drain is thoroughly discharged.

4) Usually the amount of the sample is 0.5 to 1 liter. (It depends on shore laboratories.)

5) In case of trouble, samples are to be taken at the inlet/outlet of the damaged components

(usually at the outlet of the pump). When a sample is taken at the outlet of the filter, wear

particles have been captured on the filter and the cause of the problem may not be identifi ed.

4. Standard Values for Lubricating Oil Management

The standard values which were used until recent years had been specified based on the balance

of system oil used for the older type of slow-speed engines.

Therefore, these values were determined from mere experience without technical examination.

If these values were applied to the system oil management for modern engines, uneconomical

management results would occur with large amounts of system oil drawn out and large amounts of

new oil supplied. Furthermore, even if an engine runs for a prolonged period of time with the system

oil exceeding the standard values, normal engine operation can be achieved without noticeable

problems. This has been verified by practical engine operat ions onboard. In this respect there is

still some margin to reduce new oil consumption of system oil.

More than 15 years have passed since the first high-output propulsion engine was introduced,

and only in recent years have manufacturers and oil companies prepared standard values for system

oil management for high-output propulsion engines.

However, since their standards include indefinite values, we decided to do better by reviewing

the standard values based on the results of past onboard surveys conducted by NYK.

4.1 Standard Values for System Oil Management

(two-stroke cycle slow-speed engines (crosshead type))

The NYK standard values for system oil management for two-stroke cycle slow-speed engines

(crosshead type) are shown in Table 1-3. The standard values (or recommended values) for system

oil management specified by the engine manufacturers and oil companies are shown in Table 4-1.


9/29


Table 1-3: NYK Standard Values for System Oil Management

for Two-Stroke Cycle Slow-Speed Engines (Crosshead Type)

Standard Values

MAN B&W

(MES)(HITACHI)

(KAWASAKI)

Wartsila RTA

(DU)

(MHI)

UEC

(MHI)

(AKASAKA)

(Others)

Max. 140 145 1351) Kinematic

viscosity Min.

cS

@40 15% 15% 10%

2) Flash point (PM) > 180

3) Water % v/v < 0.3

4) Total acid number increase mgKOH/g < 1.0

Max. (increase) 15 25 205) TBN

Min.

mgKOH/g

@KCIO4 3.06) Insolubles in Pentane (Method A) % m/m < 0.5

7) Insolubles in Toluene % m/m < 0.5

8) Ferrography < 50 + Trend

9) Metals

Fe, Cu, Sn, Pb, Ni, Cr)mg/kg < 20mg/kg + Trend


10/29

Copyright 2003 by NYK LINE All rights reserved 8

Table 1-4: Engine Manufacture/Oil Company Standard Values for System Oil Management

for Two-Stroke Cycle Slow-Speed Engines (Crosshead Type)

Oil company Engine manufacture

Exxon Mobil

JOMO COSMONIP PON

OILW.artsila

Sulzer

MAN

B&Wothers

BP

CASTROLSHELL

MES

HITACHI

(MAN B&W)

Limits

W.artsila

DU

RTA

Limits

MHI

(UERTA)

Guide lines

CIMAC

Guide lines

Max.+25%

1)

+35%2)

128.8 136

1501)

1602)

1451)

1502)

1361)

1432)

+3.00 [135]1)

+3.50 [142]2)

+25 1)

+50 2)

+40% 160 +30%

+3.00 [135]1)

+3.50 [142]2)

Kinematic viscosity

(cSt @40)Min.

-5%1)

-15%2)

95.0 81.75

871)

832)

-2.95 [69]1)

-3.45 [65]2)

-25 1)

-50 2)

-15% -10%

-2.95 [69]1)

-3.45 [65]2)

Flash Point () Min. 180 160 200 160 180 190 (COC) 180 (COC) 180 (PM)

Water (%v/v) Max. 0.2 0.3 0.2 (0.3) 0.1 (0.2) 1.0 0.2 0.5(m/m) 0.2 0.20.491)

0.5

2)

Total acid number (mgKOH/g) Max . - 0> 11

1)

< 42)

+151)

Max. 30

121)

151)

16 (7)1)

30 (12)2)

+100% 30

TBN

(mgKOH/g)

Min. 3.1 53

1)

22)

31)

2 (2)1)

1 (1)2)

-30% 2

32)

Insolubles in Pentane

(% m/m)1.0 1.5 0.75 (1.0) 2.0 1.0

0.5 1.491)

1.52)

Insolubles in Benzene (% m/m)

Max.

1.0

2.0

Viscosity adjusting oil

Remarks

* Upper

limit of

Insolubles

in Pentane

is 1.5%

* Figure in ( ) shows the upperlimit of water content

* Figure in ( ) shows the

upper limit of insolubles(based on DIN)

* There are standard valuesfor metal content,

Ferrography, and FT-IR.

* Mobil DTE Oil HeavyMedium is used as a low

viscosity dilution oil.

* Viscosity

@100

* Viscosity in [ ]

shows @40

SAE30,

VI=105

* TBN values in( ) areapplicable to

all but threetypes of

engines ( RTA,MC, and

ME).

*Insoluble is

analyzed byShell Method.

* For a short

per iod of

time, water

content up

to 0.5% is

acceptable.

*Upper limit

of

Insolubles

in Toluene

is 0.6%.

*Upper limit

of

Ash is

2.0%.

* Viscosity @100(SAE 30)

* Water and Insolubles in

Pentane in ( ) showupper limits.

* Max. content ofmetals are 30 mg/Kg

* Upper limit of TBNshows increase value

against new oil

( ) shows Max or Min

Renewal year of data 2002.4 2002.4 2002.4 2002.4 2002.4 2002.4 2002.4 2002.4 2002.4 1997

1) Precautionary limit2) Mandatory limit

8


11/29


5. Items to be checked for system oil management

The following items are to be checked for system oil management.

5.1 Density

1) Ingress of drip oil usually increases the density of the system oil.2) Density is an important factor when selecting a gravity disc for the purifier.

3) Check the density of the system oil in use accordingly and confirm that a correct size of gravity

disc corresponding to the density of the system oil is used.

4) Density does not directly affect engine performance.

5.2 Kinematic Viscosity

1) Kinematic viscosity is an indication of fouling in the system oil and is a fundamental item

needed for system oil management.

2) Kinematic viscosity increases due to ingress of high viscosity oil, such as drip oil / HFO (Heavy

Fuel Oil) and an increase of insolubles in the system oil. The amount of drip oil largely

depends on the type of engine, the design of the stuffing box, and wear conditions. On RTA

type engines, for example, the amount of drip oil is large on C types, while the amount of drip

oil is relatively small on T types. On MAN B&W engines and MHI UEC engines the amount of

drip oil is moderate, between those of RTA type engines.

3) Ingress of low viscosity oil, such as MDO (Marine Diesel Oil) causes a decrease in viscosity of

the system oil.

4) When an unexpected increase or decrease in viscosity takes place, inspect for a cause of this

change and take necessary measures.

5.3 Flash Point

1) In many cases contamination with fuel oil is the main cause of a decrease in flash point.

However, there is almost no case history of a decrease in flash point for a low-speed engine.

2) On older types of MAN B&W engines where the oil system lines for the camshaft and the

system oil are different, the flash point of the camshaft oil may decrease due to contamination

of the fuel oil.

3) When a slight decrease in the flash point is observed, draw out some oil and supply new oil to

maintain a proper flash point.

4) When a remarkable decrease in flash point is observed, replace all of the system oil.

5) When an unexpected decrease in flash point takes place, inspect for a cause of the decrease and

take necessary measures.

5.4 Water Content

1) When water mixes into the system oil, the lubricity decreases, the additive deposits, and


12/29


corrosion takes place on the parts, in particular, lubricating parts are adversely affected.

2) Major causes of increases in water content for low-speed engines are malfunction of the purifier

or ingress of cooling water.

Ingress of water from the purifier is mainly attributed to improper selection of gravity disc.

Since fouling usually causes an increase in density of the system oil, check the density of thesystem oil in use accordingly and confirm that a proper size of gravity disc corresponding to

density of the system oil is used.

3) When a large quantity of water (0.5% or more) is contaminated, in principle, replace

all of the system oil with new oil.

4) Contaminated oil containing a large quantity of water is to be transferred to the settling tank

and the water content is to be removed through the following procedures:

a. After raising the heating temperature in the settling tank up to 80 to 85 , stop heating and

leave it for one day to allow the oil to settle and separate in the tank, extending the settling

time to ensure sufficient separation of water, and draining off water at the bottom of tank.

b. Conduct purification by circulating through the purifier and check water content with an

onboard water content meter.

c. When fresh water contamination is found, water removal can be performed by evaporation by

increasing the heating temperature up to 105 to 110 in the settling tank. In this situation,

bubbling with clean air is an effective remedy. However, do not exceed the heating

temperature of 98 when purification by circulating through the purifier is performed at the

same time.

d. In the event of seawater contamination, set the heating temperature lower than the temperature

of the oil flow through the purifier, and discharge as much water as possible through the purifier.

Sodium chloride may remain in system oil if the heating temperature is raised to an excessive

level in the settling tank.

e. After removing water content, request shore laboratory analysis and determine how best to deal

with the treated oil based on the analysis results.

5.5 TBN (Total Base Number)

1) TBN increases because of the influence of remaining additives in drip oil.

2) The degree of increase depends on the type of engine and the design of the stuffing box.

Although TBN in drip oil is 40 to 60mgKOH/g, these values vary with the type of engine and

the lubricating oil feed rate. TBN in system oil (new oil) is approximately 5mgKOH/g

3) When the value of TBN exceeds the standard value ranges, draw out some oil and supply new

oil to maintain the proper range.


13/29


5.6 TAN (Total Acid Number)

1) TAN increases due to external factors, such as sulfur compounds and additive remaining in drip

oil.

2) Usually TBN is used as a guide for system oil management. System oil is rarely affected by acid

materials and/or oxidation except on rare occasions when combustion gas in the scavenge spaceleaks into the crankcase.

5.7 Insolubles

1) Insolubles increase due to remaining additives which have deteriorated and combustion residues

contained in drip oil.

2) Insolubles have a significant effect on the wear on the bearing and scale adherence on the

heating transfer surface.

3) Insoluble includes toluene insolubles that identify oil-insoluble material in system oil and

pentane insolubles that identify solid and oxidation byproduct, such as resins. Usually pentane

insolubles are used for assessing characteristics of the system oil.

5.8 Metal

1) An ingress of wear particles resulting from abnormal wear on the bearing increases metal

content in the system oil.

2) Metal content is an important item for assessing engine condition.

3) An increase in metal content is a clear sign that engine condition may be worsening. By

assessing changes in metal content (quantity and kind), serious engine trouble can be avoided

before developing into cr itical conditions.

4) If metal content exceeds the standard range or if a rapid increase in a certain metal content is

being shown, it could indicate an abnormal increase in the amount of wear on the bear ings , and

an immediate investigation is to be carried out on the bearings and the loosened bolts. (check

for loosened bolts)

5.9 Ferrography

1) Ferrography is an analytical method that quantifies the levels of contaminant metal particles

present in system oil.

2) This is an important item for assessing engine conditions as well as metal composition.


14/29


Chapter 2: System Oil Management for Medium-Speed Engines

1. Characteristics of system oil for medium-speed engines

A four-stroke cycle medium-speed engine (trunk-piston type) has a structure in which the

system oil directly make contact with the combustion chamber and the combustion gas. Acharacteristic of system oil for medium-speed engines is that fouling and deterioration continue as a

result of the direct contact of combustion gas and the ingress of combustion residues, such as carbon.

On medium-speed engines heavier degradation of system oil takes place compared with

low-speed engines. In particular, the characteristic of system oil is greatly affected by combustion

conditions.

Improper system oil management may lead to serious accidents, such as burnt bearings, cracks

in the crankshaft, and fractures of the connecting rod.

The design of the engine has also a significant effect on the causes of failure in the bearing. On

a crankcase and the cylinder block with low rigidity, vibration causes unstable bearing clearances,

resulting in abnormal wear. Therefore, it is important to assess the characteristics of the engine.

The main point of system oil management for medium-speed engines is to take measures to

prevent fouling by combust ion gas and combust ion compounds. More specifically, system oil

management is to be carried out by placing emphasis on control of insolubles. System oil

degradation is mainly caused by the ingress of combustion residues (such as carbon) even under

normal conditions, however, lubricating oil itself also degrades as a result of combustion gas and

acid materials.

2. Balance of system oil circulation

A balance of system oil for medium-speed engines is almost same as illustrated in Figure 1-1.

The squares with a solid line in Figure 1-1 indicate lubricating oils replenished or mixed

into the circulating system, while the squares with a dotted line indicate lubricating oils

leaked or drawn out from the circulating system. Cylinder oil which has the same characteristics of

the system oil is occasionally supplied to the cylinder liner.

2.1 Lubricating oil for replenishment

(1) New Oil Replenishment

1) New oil is replenished at periodic intervals.

2) Ensure that enough new system oil, desirably the entire amount of system oil being circulated

that can be replaced at least once, is kept at all times in order to deal with any unexpected

accidents during which an entire amount of system oil would need to be replaced.

(2) Used Cylinder Oil

1) When cylinder oil is being fed, used cylinder oil containing combustion composition enters the


15/29


system oil.

2) When the amount of cylinder feed oil is large and the amount of new oil supplied to the

crankcase is small, insoluble content will increase. In such cases, draw out some system oil in

use.

2.2 Lubricating oil for consumption

(1) Scraping off by piston rings

1) The amount of cylinder oil scraped off by the rings is greatly affected by the combustion

condition.

2) In cases where severe vibration combustion is taking place, the amount of system oil

consumption may increase more than twice as much as the normal amount.

3) When the amount of system oil consumption is remarkably large, an engine load adjustment

is to be considered.

(2) Drawn out system oil

1) When constant deterioration of the system oil is observed, conduct drawing out

operations at periodic intervals.

2) Temporary drawing out is an effective remedy for sudden deterioration in properties of the

system oil.

(3) Leaked-off oil from purifier

1) This is the lubrication oil drained out from the purifier at cleaning.

(4) Other leaked-off oil

1) This is the lubrication oil leaked from the flanges on the piping.

3. Onboard system oil management

3.1 Maintaining a proper amount of system oil

1) Carry out replenishment or drawing out in a timely manner to maintain a proper amount of

system oil at all times.

2) Consumption of system oil greatly varies with combustion conditions. Special attention should

be paid to changes in the amount of system oi l consumption.

3) System oil tends to be affected by fouling with a decrease in the total amount of the system oil.

4) In general the amount of system oil for medium-speed engines is approximately 10 to 14m3 /

10000kw (7 to 10m3 / 10000PS)

5) Attention should also be paid to the amount of new oil.


16/29


3.2 Maintaining properties of system oil

3.2.1 Replenishment and Drawing out

1) Properties of system oil are affected to varying degrees by combustion condition.

2) Carry out replenishment with new oil in a timely manner to keep the property values of the oil

within the recommended standard values.3) When the amount of system oil is large or when the amount of system oil consumption is small,

draw out some oil and then replenish with new oil. On medium-speed engines fouling

progresses at all times. Therefore, when the amount of system oil consumption is small,

heavier fouling will take place. Special attention should be paid to changes in properties for

system oil management.

4) Except in an emergency, when the values of insolubles can be maintained within the standard

values, other properties can also be maintained.

5) Determine the optimum amount of replenishment or drawing out based on the results of

periodic analysis.

3.2.2 Treatment by purifier

(1) Carry out system oil treatment with the purifier.

1) Bypass purifying

a. Set the oil flow rate for the purifier at approximately 1700 lit/h /10000kw

(1300 lit/h/10000PS).

b. Set the oil flow temperature to between 80 and 85.

c. For a total blow type purifier, set the cleaning interval to two hours or less because calcium

compound, a main ingredient in additive, is liable to become hard if two hours is exceeded.

(2) Entire quantity purifying

Treat all of the system oil during a docking period when the main engine is stopped for a

prolonged period of time.

a. Transfer all of the system oil to the lubricating oil settling tank and purify it by circulating it

through the purifier. In addition, clean the lube oil sump tank.

b. Set the heating temperature in the tank to approximately 80 .

c. The oil flow volume through the purifier is to be adjusted to between two and three times the

entire amount of system oil (With 10m3 of system oil, for example, the oil flow volume

would be between 830 to 1250 lit/h).

3.4 System oil analysis

1) Request shore laboratories to make analysis at regular intervals.

2) When conducting shipboard analysis, check the accuracy of shipboard analysis results by

comparing the results with shore analysis.


17/29


3.4.1 Purposes of system oil analysis

1) To determine whether the system oil is usable or not

2) To assess the current condition of the engine (for example, detection of abnormal wear on

bear ings)

3) To review whether the management method for system oil is appropriate or not

3.4.2 Analysis interval

1) When no problem is observed: every three months

2) When a problem occurs: when the system oil condition corresponds to one or more of the

following cases/symptoms, carry out oil analysis every two weeks and assess the effect on the

abnormality.

When analysis results (A method) of pentane insoluble content exceeds 1.0% or more.

When metal content (Cu, Sn, Al, Fe, etc.) shows a tendency to increase compared to previous

analysis results despite the fact that new oil has been replenished.

When vanadium and nickel, which are metal elements in fuel oil, show a tendency to increase,

and at the same time, a decrease in the flash point or an increase in insoluble content are

observed.

When frequent clogging takes place in the secondary and tertiary strainer installed on the

lubricating oil pipe.

When the chief engineer concludes that there is an abnormality in system oil management.

Abnormalities include the following situations:

*Analysis results show that the values of properties are out of the usable limit.

*Onboard spot test indicates that there is an abnormality in the system oil in use.

* Abnormal increase in lubricating oil consumption is observed.

3.4.3 Sampling

1) Samples (the oil actually circulating through the system) are to be taken from the sampling cock

or the air vent valves on the cooler, the pump, and the filter.

2) Prepare a clean container for sampling.

3) Sampling is to be conducted after the drain is thoroughly discharged.

4) Usually the amount of sample is 0.5 to 1 liter. (It depends on the requirements of the shore

laboratories.)

5) During trouble, samples are to be taken at the inlet/outlet of the damaged components (Usually

at the outlet of the lubricating oil pump). When a sample is taken at the outlet of the filter, wear

particles have been captured on the filer; cons equently, the cause of the problem may not be

identified.


18/29


4. Standard Values for Lubricating Oil Management

On medium-speed engines, fouling is heavier than that of low-speed engines and the fouling

may develop very rapidly depending on combustion conditions. In addition, the fouling status varies

greatly with the type of engine. Therefore, it is important to assess the characteristic of the engine

and conduct system oil management with time allowance to some degree.

4.1 Standard Values for System Oil Management

(four-stroke cycle medium-speed engines (trunk-piston type))

The NYK standard values for system oil management for four-stroke cycle medium-speed

engines (trunk-piston type) are shown in Table 2-1.

Table 2-1: NYK Standard Values for System Oil Management

for Four-Stroke Cycle medium-Speed Engine (Trunk-piston Type)

Standard Values

1) Kinematic Viscosity SEA 30SEA 40 % 25 %

2) Flash Point (PM) > 170

3) Water % v/v < 0.3

4) Total acid number (increase) mgKOH/g < 1.0

5) TBNmgKOH/g

(@KCIO4)> 16

6) Insolubles in Pentane (Method A) % m/m < 1.5

7) Insolubles in Toluene % m/m < 1.0

8) Ferrography < 50 + Trend

9) Metals Fe, Cu, Sn, Pb, Ni, Cr) mg/kg < 20mg/kg + Trend

5. Items to be checked for system oil management

The following items are to be checked for system oil management.

5.1 Density

1) Ingress of insolubles (combustion composition) usually increases the density of the system oil.

2) Density is an important factor when selecting a gravity disc for the purifier.

3) Check the density of the system oil in use accordingly and confirm that a correct size of gravity

disc corresponding to density of the system oil is used.

4) Density does not directly affect engine performance.

5.2 Kinematic Viscosity

1) Kinematic viscosity is an indication of fouling in the system oil and is a fundamental item

needed for system oil management.

2) Kinematic viscosity increases due to ingress of high viscosity oil, such as HFO (Heavy Fuel

Oil) and an increase of insoluble content in the system oil.


19/29


3) Ingress of low viscosity oil, such as MDO (Marine Diesel Oil), causes a decrease in viscosity of

the system oil.

4) When an unexpected increase or decrease in viscosity takes place, inspect for a cause of this

change and take necessary measures.

5.3 Flash Point

1) In many cases contamination with fuel oil is the main cause of a decrease in flash point.

2) When a slight decrease in flash point is observed, draw out some oil and supply new oil to

maintain a proper flash point.

3) When a remarkable decrease in flash point is observed (170 or less), replace all of the system oil.

4) When an unexpected decrease in flash point takes place, inspect for a cause of the decrease and

take necessary measures.

5.4 Water Content

1) When water mixes into the system oil, the lubricity decreases, the additive deposits, and

corrosion takes place on the parts, in particular, lubricating parts are adversely affected.

2) Major causes of increases in water content for medium-speed engines are malfunction of the

purifier or ingress of cooling water. Ingress of water from the purifier is mainly attr ibuted to

improper selection of gravity disc. Since fouling usually causes an increase in density of the

system oil, check the density of the system oil in use accordingly and confirm that a proper size

of gravity disc corresponding to density of the system oil is used.

3) When a large quantity of water (0.5% or more) is contaminated, replace all of the system oil

with new oil.

4) Contaminated oil containing a large quantity of water is to be transferred to the settling tank

and the water content is to be removed through the following procedures:

a. After raising the heating temperature in the settling tank up to 80 to 85 , stop heating and

leave it for one day to allow the oil to settle and separate in the tank, extending the settling

time to ensure sufficient separation of water, and draining off water at the bottom of the tank.

b. Conduct pur ification by circulating through the pur ifier and check water cont ent with an

onboard water content meter.

c. When fresh water contamination is found, water removal can be performed by evaporation by

increasing the heating temperature up to 105 to 110 in the settling tank. In this situation,

bubbling with clean air is an effective remedy. However, do not exceed the heating

temperature of 98 when purification by circulating through the purifier is performed at the

same time.

d. In the event of seawater contamination, set the heating temperature lower than the

temperature of the oil flow through the purifier, and discharge as much water as possible in

the purifier. Sodium chloride may remain in the system oil if the heating temperature is raised


20/29


to an excessive level in the settling tank.

e. After removing water content, request shore laboratory analysis and determine how best to

deal with the treated oil based on the analysis results.

5 .5 TBN (Total Base Number)1) TBN decreases as a result of ingress of combustion gas and mixture of acid substance contained

in combustion composition.

2) The degree of decrease is affected by combustion conditions and sulfur content in fuel oil.

5.6 TAN (Total Acid Number)

1) TAN increases as a result of external factors, such as sulfur compounds and additive remaining

in drip oil.

2) Usually TBN is used as a guide for system oil management.

5.7 Insolubles

1) Insolubles have a significant effect on the wear on the bearings.

2) Insoluble content is a fundamental item needed for system oil management for medium-speed

engines.

3) Insolubles include toluene insolubles that identify oil-insoluble materials in system oil and

pentane insolubles that identify solid and oxidation byproducts, such as resins. Usually, pentane

insolubles are used for assessing characteristics of the system oil

5.8 Metal

1) An ingress of wear particles resulting from abnormal wear on the bearings increases metal

content in the system oil.

2) Metal content is an important item for assessing engine condition.

3) An increase in metal content is a clear sign that engine condition may be worsening. By

assessing changes in metal content (quantity and kind) serious engine trouble can be avoided

before developing into cr itical condition.

4) If metal content exceeds the standard range or if a rapid increase in a certain metal content is

being shown, it could indicate an abnormal increase in the amount of wear on the bear ings , and

an immediate investigation should be carried out on the bearings and the bolts. (check for

loosened bolts)

5.9 Ferrography

1) Ferrography is an analytical method that quantifies the levels of contaminant metal particles

present in system oil.

2) This is an important item for assessing engine conditions as well as metal content composition.


21/29


Chapter3: Economical System Oil Management for Slow-Speed Engines

1. Replenishment method for system oil

Based on the NYK Standard for system oil management and the SMS Manual, onboard system

oil management has been implemented in accordance with the actual situation on each vessel. Theresults of the reviews conducted so far suggest that there is still some margin to reduce new oil

consumption of system oil.

The amount of new oil consumption can be reduced by adopting the most suitable method from

the following three methods, with some consideration given to the characteristics of engine as well

as the properties of system oil in use.

1) Replenishment with only new oil

2) Re-use of stuffing box leaked oil as replenishment oil (recycling oil)

3) Use of low viscosity oil as replenishment oil

Figure 3.1 shows replenishment methods and guides for property values of the system oil.

2. Replenishment with only new oil

2.1 Guide for implementation

This method is applicable to the engines in which the properties of system oil can be maintained

within the following ranges when replenishing with only new oil.

1) Kinematic Viscosity: 130 to 135 cSt

(note that the value must not exceed the upper limit of the standard value)

2) TBN increase : 15 to 20 mgKOH/g

(note that the value must not exceed the upper limit of the standard value)

3. Re-use of stuffing box leaked oil

1) This is a method in which stuffing leaked oil is collected and used together with new oil after

purifying it with the pur ifier. Stuffing leaked oil has similar properties to system oil.

2) For implementing this method, another settling tank for storage of re-use oil (recycling oil) is

necessary in addition to a storage tank for new oil.

New Oil Upper limits

Kinematic 95~105 130~135 135~145viscosity(cSt @40)

TBN 5~ 7 15~20 20~25(mgKOH/g)

Replenishment

with only new oil

Re-use of stuffing

Box leak oil

Use of Low

Viscosity Oil

Fig. 3.1: Guides for Selection of Replenishment Method

(Convergence Values When Supplied Only New Oil)


22/29


3) This method is not applicable to the engines in which the same drain line is used for the stuffing

box leaked oil and the lantern drain oil.


This method is applicable to the engines in which the properties of system oil can be maintainedwithin the following ranges when replenishing with only new oil.

1) Kinematic Viscosity: 135 to 130 cSt or less

2) TBN increase : 20 to 15 mgKOH/g or less

3.2 Procedures for recycling

The following procedures are to be taken for re-use of stuffing box leaked oil:

3.2.1 Collecting stuffing box leaked oil

1) Transfer stuffing box leaked oil to the settling tank.

3.2.2 Heating/Settling/Draining

1) After raising the heating temperature in the settling tank up to 80 to 85 , leave it for

approximately one day and drain off sediment.

2) When a large quantity of impurities is found in the oil, stop heating the oil during the settling

period to improve sedimentation.

3) When water content (fresh water) is large, the heating temperature may be increased up to

105 to evaporate contained water. In this situation, bubbling with clean air is an effective

remedy.

3.2.3 Purifying (Refer to Figure 3-2)

1) Set the heating temperature in the settling tank between 80 to 85 and conduct purification

by circulating through the purifier for at least one day.

2) Adjust the flow rate in the purifier at 30% or less of the rated volume flow rate and set the

heating temperature of the oil through the purifier between 85 to 90 .

3) As heavy fouling will most likely take place in the purifier, shorten overhauling/ maintenance

intervals in accordance with fouling status.

4) If two settling tanks are available, more effective purification results can be obtained by

purifying the entire quantity of oil between the tanks via the purifier.

Collecting stuffing

box leaked oil

Heating

Settling

Draining off

Purifying

Analyzing

PropertiesDetermining

blending rati o

Replenishment


23/29


3.2.4 Analyzing Properties/determining blending ratio

1) Request shore laboratories to make analysis of properties of the recycling oil.

Determine whether the recycling oil is usable or not. Determine a blending ratio with new oil.

2) Determine a blending ratio in accordance with the actual condition of the system oil on each

vessel because the type of engine and maintenance conditions affect the blending ratio.

3.2.5 Replenishment

1) Do not carry out replenishment with only recycled oil to avoid a large decrease in properties ofthe system oil. New oil must be used together with recycled oil.

4. Use of Low Viscosity Oil

1) This method is applicable to engines on which a rapid increase is observed in kinematic

viscosity and TBN, resulting from a large amount of used lubricating oil mixture; consequently,

frequent drawing out operations should be carried out.

2) For implementing this method, another settling tank for storage of low viscosity oil is necessary

in addition to a storage tank for new oil.


This method is applicable to engines in which the properties of system oil can be maintained

within the following ranges when replenishing with only new oil.

1) Kinematic Viscosity: 135 to 145 cSt or more

2) TBN increase : 20 to 25 mgKOH/g or more

4.2 Use of Low Viscosity Oil

Separated from the storage tank for normal system oil, low viscosity oil should be stored in

Circulating purification with one tank Entire quantity purification with two tanks

Fig. 3-2: Purification for re-use oil

Collect tank

for stuffing

box leaked oil

Storage

tank

for new oil

Settling

tank for

re-use oil

Purifier Main engine

Purifier

Collect tank

for stuffing

box leaked oil

Settling

Tank

No.1

Storage

tank for

new oil

Main engine

Settling

tank

No.2

Purifier

Purifier

B ass Purif in


24/29


only the storage tank provided for low viscosity oil and used

together with new oil as replenishment oil. Since the

blending rat io is greatly affected by the type of engine,

maintenance conditions, the degree of increase in kinematic

viscosity and the properties of the low viscosity oil,determine a blending ratio in accordance with the actual

condition of the system oil on each vessel.

Table 3-1 shows the properties of low viscosity oil

produced by the major oil companies.

Table 3-1: Low Viscosity Oils of Major Oil Companies

Oil company Name of oil DensityKinematic

viscosity 40/100TBN

NIPPON OIL Marine S20 0.884 71.4 / 9.03 7

JOMO ATLANTA MARINE D 2005 0.878 44.8 / 6.76 5

COSMO COSMO MARINE 2005 0.880 49.13 / 7.17 5.5

SHELLMelina S Oil 20

Merina Oil 20

0.882

0.893

67.0 / 8.7

67.9 / 8.8

5

8

EXXON MOBIL Mobil DTE Oil Heavy Medium 0.875 64 /8.6

BP CASTROL CASTROL CDX 20 0.890 65 / 8.3 5

5. Replenishment ratio of recycling oil and low viscosity oil

Figure 3-4 shows a simplified flow diagram

for system oil in the circulating system. In the

circulating system the amount of oil supplied

into the circulating system (oil-in) makes up for

the amount of oil leaked out or drawn out of the

circulating system (oil-out). Thus, the total

amount of system oil is controlled to maintain a

certain level. For an engine in which the amount

of oil-out is large, replenishment with only new

oil will result in an increase in the amount of

oil-in. As a result, the standard value specified

for the system oil management becomes lower.

Meanwhile, for an engine in which the

amount of oil-out is small, the standard value

specified for the system oil management tends to

be higher because the amount of oil-in will

decrease. The amount of oil-in and oil-out is greatly affected by the design of the stuffing box and

the wear condition of the seal rings. When the system oil leaks, a large amount of system oil will

Storage tank

for new oil

Main engine

Storage tank

for low

viscosit oil

Purifier

Bypass Purifying

Fig. 3-3: Use of Low Viscosity Oil

Other

leaked oil

Sump tank

of engine

Cylinder

oil

Purifier

Either is used

Drippedoil

Leaked oil

of stuff. box

Collect tank

of leaked oil

Drawing

New oil

tank

(Normal oil)

Low

Viscosityoil tank

Re-use

oil tank

Fig. 3-4: Flow diagram of system oil


25/29


drain out into the system. When the used cylinder oil passes the stuffing box seal rings, a large

amount of oil contaminated will drain into the crankcase.

In this section, we consider the use of recycled oil (leaked oil from the stuffing box) and proper

system oil management corresponding to the amount of drip oil.

5.1 Reuse of recycled oil (stuffing box leak oil)

Calculated values of kinematic viscosity with use of recycled oil are shown in Table 3-2.

Figures 3-5, 3-6, and 3-7 show the predicted transition of kinematic viscosity and TBN as a

function of the time when recycled oils of different blending ratios are used. Table 3-2 reports that

the calculated values of kinematic viscosity with use of recycled oil at different blending ratios are

compared to the value of kinematic viscosity with only new oil when the total amount of supply oil

(new oil + recycled oil) is maintained at the same level.

When the upper limit value of kimematic viscosity is specified at approximately 140cSt, a

reduction of new oil replenishment can be expected in an engine in which kinematic viscosity is

controlled at 130cSt or less. In particular, in an engine in which kinematic viscosity is controlled at

115cSt or less, 50% or greater reduction effectiveness can be expected.

Table 3-2: Calculated Values of Kinematic Viscosity and TBN with Use of Re-Use Oil

Percentage of

re-use oil ()

= Reduction of new oilConverged values Kinematic viscosity / TBN

0 (New oil only) 110.0 / 5.1 115.0 / 7.4 120.0 / 9.6 125.0 / 11.7 130.0 /13.7

20 114.6 / 7.3 120.6 / 10.3 123.9 / 11.8 132.2 / 15.6 137.9 / 18.0

30 117.9 / 8.4 124.9 / 11.7 128.0 / 13.3 137.1 / 17.3 143.1 / 19.8

40 122.1 / 9.9 129.5 / 13.4 133.4 / 15.2 143.3 / 19.4 149.7 / 21.9

50 128.0 / 11.8 136.3 / 15.7 140.7 / 17.5 151.3 / 21.9 153.5 / 22.7

55 131.9 / 13.0 140.7 / 17.0 148.8 / 20.4

60 136.5 / 14.5 146.0 / 18.7 154.5 / 22.1

65 142.6 / 16.3 152.6 / 20.6

70 150.4 / 18.5

Note: 1) Recycled oil kimematic viscosity: 110% of the system oil in use

TBN : 2mgKOH/g larger than the system oil in use2) Recycled oil ratio is the rate of the total amount of supply.

Figures 3-5, 3-6 and 3-7 show prediction curves in which the values for kinematic viscosity of

the system oils converge at 110, 120, 125cSt respectively when only new oil with 100 cSt at 40 is

supplied. In all cases, kimematic viscosity of the recycled oil is 110% and TBN is +2mgKOH/g of

the system oil in use. For example, when kimematic viscosity of the system oil converges at 110cSt

on an engine whose system oil is controlled by only new oil, kimematic viscosity will converge at

128cSt and TBN will converge at +11.8 mgKOH/g respectively by using recycled oil with 50% of thetotal amount of supply oil.


26/29


100

110

120

130

140

150

0 20000 40000 60000

0

0.4

0.5

0.6

0.650

5

10

15

20

25

0 20000 40000 60000

(c

St@40)

TBN(mg

KOH/g)

(hr) (hr)

Ratio of

Re-use oil

Fig. 3-5: Prediction Curves in Kinematic Viscosity and TBN at Different

Blending Ratio of Recycled Oil (Convergence Value for New Oil:110cSt)

Running hours (hr) Running hours (hr)

TBN(mgKOH/g)

Viscosity(cSt@40)

100

110

120

130

140

150

0 20000 40000 60000

0

0.2

0.3

0.4

0.5

0

5

10

15

20

25

0 20000 40000 60000

(cSt@40)

TBN(mgKOH/g)

(hr) (hr)



Ratio ofRe-use oil


TBN(mgKOH/g)

Viscosity(cSt@40)

100

110

120

130

140

150

0 20000 40000 60000

0

0.2

0.3

0.4

0

5

10

15

20

25

0 20000 40000 60000

(cSt@40)

TBN(mgKOH/g)

(hr) (hr)



Ratio ofRe-use oil


TBN(mgKOH/g

)

Viscosity(cSt@40

)


27/29


5.2 Make up with low viscosity oil

Calculated values of kinematic viscosity and TBN of system oil with use of low viscosity oil are

shown in Table 3-3. Figures 3-8, 3-9 and 3-10 show the predicted transition of kinematic viscosity

and TBN as a function of the time when low viscosity oils at different blending ratios are used.

The amount of replenishment with which the target values of 135cSt and 140cSt can bemaintained are shown in Table 3-3. The values for LO consumption and TBN in Table 3-3 are

represented in accordance with four different blending ratios and viscosities of low viscosity oils.

(Values for the blending ratios are compared to replenishment with only new oil (100cSt), considered

to have a value of 100%.) The lower the kinematic viscosity of low viscosity oil and the greater the

blending rat io, the larger the effectiveness in reducing the amount of new oil to be supplied. However,

when TBN of both low viscosity oil and new oil have the same value, a reduction of TBN in blending

oil cannot be expected. In particular, when kinematic viscosity in low viscosity oil is low and the

blending rat io of low viscosity oil is large, special attention should be paid. On actual vessels the

relationship between kinematic viscosity of low viscosity oil and TBN does not necessarily

correspond to Table 3-3, however, when the target value of kinematic viscosity of the system oil is

set at 140cSt, the blending ratios need to be at 40% or less with low viscosity oil with 70cSt and 20%

or less with low viscosity oil with 50cSt.

Figure 3-8, 3-9 and 3-10 show the relationship between the blending ratios of low viscosity oil

(with 70cSt of kinematic viscosity) and the kinematic viscosity and TBN of the system oil when the

total amount of supply oil (new oil + low viscosity oil) is maintained at the same level. These

figures also illustrate prediction curves in which values of the kinematic viscosity of the system oils

converge at 145, 150, and 160 cSt respectively when only new oil with 100 cSt at 40 is supplied.

When the target value for kinematic viscosity of the system oil is set at 140cSt, the blending

ratios will be at 15% with 145cSt (convergence value for new oil), 30% with 150cSt, and 70% with

160cSt respectively. As the total amount of supply oil (new system oil + low viscosity oil) stays at

the same level, the value of TBN will also stay at the same level regardless of the blending ratio, and

TBN will converge at 21.5 mgKOH/g with 145cSt (convergence value for new oil), 23.5mgKOH/g

with 150cSt,and 27.0 mgKOH/g with 160cSt respectively.


28/29


Table 3-3: Calculated Values of Viscosity and TBN with Use of Low Viscosity Oil

Target viscosity:135cSt Target viscosity:140cStRatio of

low viscosity oil

ratio to thetotal amount

Viscosity of

low viscosity oil

(cSt)

LO

consumption

%

TBN

Convergence

value(mgKOH/g)

LO

consumption

TBN

Convergence

value(mgKOH/g)

50 66 + 22.3 68 + 24.0

60 73 + 21.1 75 + 22.9

70 80 + 20.0 81 + 21.920 %

100 100 + 17.4 100 + 19.3

50 49 + 26.0 52 + 27.5

60 57 + 24.0 60 + 25.7

70 66 + 22.3 69 + 24.040 %

100 100 + 17.4 100 + 19.3

50 44 + 27.4 46 + 28.9

60 52 + 25.3 55 + 26.870 61 + 23.3 64 + 24.9

50 %

100 100 + 17.4 100 + 19.3

50 39 + 28.7 42 + 30.1

60 47 + 26.5 50 + 27.9

70 57 + 24.2 59 + 25.860 %

100 100 + 17.4 100 + 19.3

TBN of low viscosity oil is assumed to be equal.

Drawing out of using oil is not taking into consideration.


29/29

100

120

140

160

0 20000 40000 60000

0

0.5

0.6

0.7

0.9

0

5

10

15

20

25

30

0 20000 40000 60000

(cSt@

40)

TBN(mgKOH

/g)

(hr) (hr)

Fig. 3-10: Prediction Curves in Kinematic Viscosity and TBN at Different Blending

Ratio of Low Viscosity Oil (Convergence Value for Normal Oil:160cSt)

Ratio oflow vis.

oil


TBN(mgKOH

/g)

Viscosity(cSt@

40)

100

120

140

160

0 20000 40000 60000

0

0.3

0.4

0.5

0.6

0

5

10

15

20

25

30

0 20000 40000 60000

(cSt@40)

TBN(mgKOH/g)

(hr) (hr)

Ratio oflow vis.

oil


TBN(mgKOH/g)

Viscosity(cSt@40)



100

120

140

160

0 20000 40000 60000

0

0.15

0.3

0.450

5

10

15

20

25

30

0 20000 40000 60000

(c

St@40)

TBN(mg

KOH/g)

(hr) (hr)

Ratio of

low vis.oil


TBN(mgKOH/g)

Viscosity(cSt@40)



Date post:	13-Apr-2018
Category:	Documents
Upload:	cvita-cvitic
View:	237 times
Download:	0 times

Guidance for Lubricating Oil Management

Documents