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INDIAN RAILWAYS MAINTENANCE MANUAL FOR DIESEL LOCOMOTIVES - PART 52

Document No:

Chapter –8 Fuel & Lubricants

Version No: 1.0-d0

Date Issued: dd/mm/yyyy

Document Title: MANUAL MAINTENANCE FOR DIESEL LOCOMOTIVES

Revised 2013

Printed: 2015/03/08

Page 200 of 303

Certain polymeric additives, e.g. some viscosity index improvers show a
reduction of viscosity in service due to mechanical shearing of the polymer
molecules. Oxidation of oil results in increase of viscosity but this is usually
associated with increase in insoluble content and acidity of the oil

8.37.2.3 Flash Point: A drop in flash point of the oil in use indicates its contamination

with the fuel either through scraping action of the rings of the un-burnt fuel
condensed on the walls or through blow by. It is very difficult, from the
measurements of flash point, to determine the extent of fuel dilution. However,
certain broad limits can be set to safeguard against the ill effects of excessive
dilution, on the basis of experience.

8.37.2.4 Sulphated Ash: No limit can be set on the total ash content. However, its

qualitative and quantitative examination is very useful in predicting the
mechanical condition of the engine.

8.37.2.5 Water: Water may enter the crankcase through a water leakage from the cooling

system or due to the condensation as a result of operating the engine under
unduly low temperature conditions. Water tends to increase the viscosity of the
oil and may have an  adverse effect on oxidation, may accelerate sludge
formation and increase foaming tendency. It also has an adverse effect on the
additives in the oil and may cause bearing failures. Presence of water can be
determined by crackling test (qualitatively) and  by distillation test
(quantitatively)

8.37.2.6 Acidity (TAN): Oxidation and contamination with acidic combustion products

contribute to the increase in the oil’s acidity which is determined as “Total Acid
Number (TAN). The part of the acidity that is derived from the strong acids
(inorganic acids) is determined by titration against Pott. Hydroxide (Alcoholic)
solution to an end point corresponding to pH4 , which is indicative of negligible
presence of strong acids. Strong acids are harmful to the bearings and cause
troublesome engine deposits.

8.37.2.7 TBN: TBN of the lube oil is a measure of the potential of the oil to neutralize

strong acids such as mineral acids derived from sulphur, chlorine etc. The
concentration of alkalinity is also used as a criterion of the effectiveness of the
additives. Corrosive wear and rusting in engines caused particularly under low
temperature operating conditions could be effectively combated by increased
alkalinity which is generally introduced into the oil through the use of over-
based Calcium / Barium sulphonate type of additives. High TBN oils are also
found to minimize varnish and sludge deposits in the engine. The TBN should
also be maintained at a certain minimum value. The oil should be changed when
the TBN is equal to or less than the “fuel Sulphur content (% weight) + 0.1”.

8.37.2.8 Oil Insolubles: The suspended and partly dissolved contaminating matter in the

oil contributed by air borne dust, fuel carbon, highly carbonized materials from
the degradation of oil fuel and additives, engine wear debris, oil soluble
resinous matter, etc. is evaluated by the Pentane/Hexane and Benzene insoluble
test. This information facilitates taking preventive steps before the insoluble
reach a value high enough to interference with the proper functioning of the
lubricant. Generally the following insoluble content, is not considered harmful

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Document No:

Chapter –8 Fuel & Lubricants

Version No: 1.0-d0

Date Issued: dd/mm/yyyy

Document Title: MANUAL MAINTENANCE FOR DIESEL LOCOMOTIVES

Revised 2013

Printed: 2015/03/08

Page 201 of 303

for the diesel engines using higher detergency oils such as MIL-L-2104 B level
oils:

a.  Hexane/Pentane insoluble’s -  upto 3.5%
b.  Toluene insoluble’s    -  upto 2.5%
c.  Resins

- 0.5%

However, these limits have to be specified separately for each oil and the engine
in which it is used.

8.37.2.9 Blotter Spot Test :

a. There is no dispersancy test in general use in laboratories and in this one instance

“Blotter spot test” can provide information not obtainable from a routine laboratory
examination. The test consists of depositing a drop of oil from the engine crankcase
on a sheet of a specified type of filter paper. After a certain number of hours
(depending upon the temperature of the oil and the entrained carbon particles) will
have diffused into the pores of the filter paper. An examination of the oil spot shows:

A central zone with light or dark centre called the drop core

ii.

A dark HALO surrounding the central zone (drop core)

iii.

A zone of diffusion outside the halo

iv.

A translucent area soaked with oil outside the diffusion zone.

b. The information is particularly useful when the blotter spot tests are carried out on a

regular interval.

Contamination with the insolubles (primarily combustion spot) is judged by
the lightness or darkness of the Central Zone.

ii.

The lightness or darkness of the soot spot (Central Zone) is markedly
affected by the dispersancy of the oil. An oil of poor dispersancy will
deposit its soot burden on a much smaller area than will a highly dispersant
oil.

iii.

The dispersancy is judged by the extent to which the oil carries its
contaminant through the paper (the zone of diffusion). The decrease of
disappearance of this zone indicates flocculation of the suspension and a fall
in the detergency level of the oil (effectiveness of additives).

iv.

The presence of fuel oil in the lube oil is indicated by divergent and irregular
drop core. The out zone is also comparatively dark.

Water has the effect of imparting a clearly defined boundary to the Central
Zone. The size of the drop halo is smaller than normal. The centre is heavy
block.

8.37.2.10 pH Value: pH value of the oil gives a rough indication of the presence of

Alkalinity/Acidity in the oil. A pH value of less than 4 indicates the presence of
or formation of inorganic (strong) acids in the oil.

8.37.2.11 If the test results are to be used towards evolving better usage standards of

lubricating oils, etc., it is imperative that proper records of the various checks
carried out are maintained in a systematic fashion. This should be the
responsibility of the Laboratory Superintendent who would keep the SSE/Diesel
informed in regard to the lubricating oil changes, etc. It should also be ensured
that a forecast of the various schedules to be carried out along with the dates

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Document No:

Chapter –8 Fuel & Lubricants

Version No: 1.0-d0

Date Issued: dd/mm/yyyy

Document Title: MANUAL MAINTENANCE FOR DIESEL LOCOMOTIVES

Revised 2013

Printed: 2015/03/08

Page 202 of 303

and time thereof, is supplied to the Laboratory Superintendent, so that the
samples are drawn at the proper time.

8.37.2.12 Spectrographic Analysis of Oil:

a. Spectrographic analysis of used crankcase oil is a valuable tool in providing

warning about abnormal wear which may lead to major breakdown such as piston
or bearing seizure. It does not, however, give prior indication of a sudden failure
of any component due to fatigue. It may be said that spectrographic analysis of
the used lube oil is analogous to the blood test of human body with a view to
detect the abnormality of the system. The spectrographic analysis of the used
crankcase oil helps in:

Predicting the required maintenance.

ii.

Scheduling the overhauls, thus avoiding unexpected down time and
thereby increasing the loco availability.

iii.

Preventing engine failure resulting from the incipient wear of engine
components.

b. During calibration of spectrograph it should be ensured that temperature,

humidity and other conditions in spectrograph labs are maintained as per the
manufacturer’s recommendations. The equipment shall be calibrated with the
primary standard supplied by the manufacturer. Spectrographic analysis of used
oil samples shall be done after calibrating the spectrograph against the fresh oil
samples and adjusting the fresh oil values to zero.

The correlation between wear

elements and the engine condition is given in the table below:

Indication of elements & engine wear by spectrograph

S. No.

Element

Indication

Bushing wear

Main / Connecting rod, Turbocharger bearing wear

Bushing shaft wear, ring wear

Cylinder liner wear

Water leakage

Piston wear, Inefficient filtration

Inefficient air filtration

8.37.2.13 Ferrography: Ferrography is a technique for analysing the particles present in

fluids that indicate mechanical wear. It uses microscopic examination and was
developed in the 1970s for predictive maintenance. It overcomes the large
particle detection deficiencies of spectrographic analysis of oil. It has proved
much more useful, as compared to spectrographic analysis of oil, in accurately
predicting impending failures of components.

8.37.3

Procedure for Drawing Samples of Engine Lubricating Oils:

8.37.3.1 The value of any analysis carried out depends entirely on whether the sample

provided for test is truly representative of the bulk oil in the crankcase. Too
much emphasis, therefore, cannot be placed on the importance of correct

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Document No:

Chapter –8 Fuel & Lubricants

Version No: 1.0-d0

Date Issued: dd/mm/yyyy

Document Title: MANUAL MAINTENANCE FOR DIESEL LOCOMOTIVES

Revised 2013

Printed: 2015/03/08

Page 203 of 303

sampling and it should only be undertaken by persons who are specially trained
in it and with the proper equipment.

8.37.3.2 The proper equipment consists of a hand syringe with nozzle extended by a tube

which when fully inserted from the dipstick hole or any other suitable opening
from where the sample of oil is to be taken, reaches midway between the
bottom of the sump of the crankcase and the oil level. The container into which
the sample is to be taken should be capable of being cleaned quickly and
properly. For cleaning the container neither water nor paraffin should be
employed. The presence of water and the effect of paraffin on the flash point
could lead to misleading results. The best method of cleaning the container is to
rinse it thoroughly with new engine oil and allow it to drain.

8.37.3.3 The following points should be rigidly observed while taking sample:-

a. The oil must be hot and in a state of agitation. The sample should preferably be

drawn while the engine is running or just after it is shut down.

b. Flush the syringe by filling and discharging it back into the sump twice, before

drawing the final sample.

c. Use a clean and dry container for the sample and only fill it 2/3

, so as to

facilitate shaking of the oil prior to testing.

d. If a syringe cannot be used and the sample must be taken from a drain cock,

allow at least twice the capacity of the drain pipe to discharge before taking the
sample so as to avoid any possibility of stagnant oil being included in the
sample.

e. The sampling operation MUST be carried out before the addition of topping-up

oil.

f. For ease of identification, each container must be properly marked with loco

number, date sample drawn, etc.

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