4. 3.Challenges to industries
For any power generation facility, the turbine is
considered the lifeblood of the operation.
According to a 1991 study by General Electric (GE),
turbines contribute on average 20 percent of all
forced outages in a conventional power plant. Among
this 20 percent, GE noted that 19 percent of
turbine/generator problems were associated with the
lube oil system.
For this reason, monitoring turbine oils has become
common place in the power generation industry.
5. 4.Purpose
Lubricant testing is recommended for the
following reasons:
To study the condition (wear, and so
on) of the machine being lubricated. If
there is a problem with the lubricant,
there is a strong possibility that the
machine will need maintenance.
To determine if the lubricant is meeting
the specifications.
6. 5.LUBRICANT LAB TESTS
The following are laboratory tests performed on
oil samples:
1. Particle count -ISO 4405, 4406)
2. Fourier transform-infrared analysis
3. Additive Package Condition
4. Viscosity testing (ASTM D445)
5. Total acid number (TAN)
6. Spectrometric analysis/emission spectroscopy
7. Crackle test/Karl Fischer water test
8. Oxidation stability test (ASTM D2272)
9. Demulsibility (ASTM D1401-96)
10. Pour point (ASTM D97)
11 .Foam test (ASTM D892-95
12. Flash point (ASTM D92)
7. 5.1.Particle Count -ISO 4405, 4406:
Particles in lube oil have long been
recognized as the main cause of failure in
hydraulics and rotational machinery.
Particles are also a leading indicator of a
machine’s condition. Because all
contaminants in the oil are counted as
particles, the particle count includes wear
particles, soot, dirt, and other contaminates.
This test provides information on lubricant
cleanliness.
8. 5.2. Fourier transform-infrared analysis
The FT-IR monitors the chemical composition of
the oil in certain key wavelengths.
The infrared absorption spectrum of a lubricant
furnishes a means of fingerprinting organic
compounds and functional groups. Test results
are trended and quantitative and qualitative
determinations can be made.
Infrared analysis is often used for identifying
additives and their concentrations, reaction
products, and contamination by organic
materials in used lubricants.
Oxidation (carboxylic acids and esters), nitrate
esters, water, soot, and glycol can be
quantified.
9. 5.3. Additive Package Condition:
Additives present in a lubricant improve and strengthen
the performance characteristics. Chemically active
additives are able to interact with metals and form a
protective film with the metallic components present in
the machinery.
The designer of the additive package must ensure that
the additives will not produce unacceptable side effects.
If an additive is present in excessive levels or interacts
in an unsatisfactory manner with other additives that are
present, it can be detrimental to the equipment.
Over time, additive packages can deplete, leaving
machinery unprotected and vulnerable to failure.
10. 5.4. Viscosity testing (ASTM D445):
Viscosity is one of the most important characteristics of
an oil because it ensures that the proper film strength is
present to minimize metal-to-metal contact and machine
wear. Viscosity is a factor in the formation of lubricating
films under both thick and thin film conditions.
If the viscosity is too low, the oil may not have the
necessary film strength required to maintain a proper oil
film. An inadequate oil film results in excessive wear. A
decrease in viscosity may indicate contamination with a
solvent or fuel or with lower grade viscosity oil.
If the viscosity is too high, additional fluid friction is
generated. This increases the operating temperature of
the bearings and increases the rate of oxidation.
11. 5.5. Total acid number (TAN)
(ASTM D664 and D974)
The acidity of lubricants is measured by the
amount of potassium hydroxide required for
neutralization (mg KOH/g), and the resultant
number is called the TAN.
An increase in TAN may indicate lube oxidation
or contamination with an acidic product.
A severely degraded lubricant indicated by a
high TAN may be very corrosive.
12. 5.6. Spectrometric Analysis/emission
spectroscopy/rotrode filter spectroscopy
Elemental analysis is performed in accordance
with atomic emission spectroscopy (AES).
A specific volume of lubricant is energized
using an electrical arc. The light frequencies
and intensities are measured and reported in
parts per million of various elements.
The following elements are analyzed: Fe, Cr,
Al, Pb, Sn, Cu, Ag, Ni, Na, V, Cd, Ti, Mo, Ca,
Ba, P, Zn, B, K, Mg, and Si.
13. 5.7. Crackle test/Karl Fischer water test
(ASTM D-4928 and D1744)
Water in a lubricant not only promotes corrosion and
oxidation, but also it may form an emulsion having the
appearance of a soft sludge. In many bearing
applications, even a small amount of water can be
detrimental, especially in journal-bearing applications
where the oil film thickness is critical.
In the crackle test, a drop of oil from an eyedropper is
placed on a hot plate heated to 100°C, and monitored
for the characteristic crackle that occurs as water
explodes into steam.
14. 5.8. Oxidation Stability Test
(ASTM D2272):
This was formerly called the rotating
bomb oxidation test, and it is used to
assess the remaining life of in-service
lubricants.
15. 5.9. Demulsibility (ASTM D1401-96):
This test provides a guide for
determining the water separation
characteristics of oils subject to water
contamination and turbulence.
16. 5.10. Pour Point (ASTM D97):
The pour point is the determination of
the lowest temperature that a
petroleum product may be used if
fluidity is necessary to the
application.
17. 5.11 .Foam Test (ASTM D892-95)
Foaming of the oil may result when air is
picked up by the oil and is thoroughly mixed by
agitation and churning. Excessive foam
accumulation can result in loss of oil by
overflow or seepage.
High quality oil should have good resistance to
excessive foaming, and the air bubbles formed
on the surface should break up quickly.
The foam test is the determination of the
foaming characteristics of lubricating oils at
specified temperatures.
18. 5.12. Flash Point (ASTM D92):
Flash point indicates the presence of highly
volatile and flammable materials in a relatively
nonvolatile or nonflammable material.
The lubricant sample temperature is raised at
a constant rate as the flash point is
approached. The flash point is the lowest
temperature at which the application of the test
flame causes the vapors above the surface of
the liquid to ignite
19. 5.13. Cone penetration of lubricating
grease (ASTM D 217)
This test measures the consistency of grease.
The cone is dropped into the grease sample
from a specified height and at a specific time.
The measured amount that the cone
penetrates into the grease is the cone
penetration
20. 5.14.Percent Sediment in Lubricating Oils
This test is an excellent determination
of sediments suspended in lubricating
oil. Excessive amounts of sediments
can impede oil capability and can clog
filters.
21. 6.Sample
Recommendations for taking samples are:
Take the sample when the system is stabilized, not
before or just after makeup lubricant has been added.
Take the sample ahead of filters so that contaminants
are still in the lubricant.
Put the oil sample in a suitable, clean, well-labeled
container.
Take the sample using a consistent method. Take the
sample from the same location and under the same
operating condition.
22. 7.Machines Cover Under Lubricants
Testing Program in thermal power plants
Mill,
Air preheater,
Turbine ,
Boiler feed pump,
F D Fan,
ID Fan,
PA Fan,
Compressor,
23. 8.Deterioration of lube Oil in
Service
Oxidative Degradation -This occurs as the result of
chemical changes brought about by oxygen in the
atmosphere.
Thermal/Oxidative Degradation -This may occur at
hot spots in turbines. At elevated temperatures,
hydrocarbons are subject to thermal cracking to form
unstable compounds.
Water Accumulation in the System Accumulated
water promotes oil degradation .
Loss 0f Additives -This can result in more rapid
oxidation and premature rusting.
Influx 0f Contaminants -Contaminants arising within
the system (corrosion and wear products) or from fly
ash/ dirt, fluids cause wear problems.
24. 9.Turbine oil monitoring
The key to efficient turbine maintenance is
routine monitoring of the oil, which ensures
that decisions involving the turbine,
including scheduling of oil changes and
other maintenance, are based on what is
actually happening inside the unit, instead
of the number of hours, days or years of
operation.
Routine and in-depth monitoring can
provide warning signs early enough to take
corrective action.
25. 9.1.DAILY AND WEEKLY TEST,
INSPECTION OF LUBRICANT –
STEAM TURBINE LUBE OIL :
DAILY-Visual Test for Change in
Appearance to Indicate Excessive
Water or Solid Contamination
WEEKLY-Visual Test of Oil Color to
Detect Deterioration (Reference ASTM
Test Method D 1500-82)
26. 9.2.QUARTERLY TEST, INSPECTION OF
LUBRICANT –STEAM TURBINE LUBE OIL:
Laboratory Test for Viscosity to Indicate Oil
Contamination or Deterioration (Ref ASTM Test D 445-
82)
Laboratory Test for Total Acid Number to Indicate
Antioxidant Depletion (Ref ASTM Tests D 974-80, D 664-
81, D 3339-80/DIN 51587)
Laboratory Test for Water Content to Indicate Water
Contamination (Ref ASTM Tests D 95-70, D 1744-64)
Laboratory Test for Cleanliness to Indicate Particle
Contamination (Ref ASTM Tests F 311-78, F 312-69, F
313-78/ISO 4406).
27. 9.3.YEARLY TEST, INSPECTION OF
LUBRICANT –STEAM TURBINE LUBE OIL:
Lab Test for Anti-Rust Protection Capability to Show
Depletion of Rust Inhibitor (Ref ASTM Test D 665-82)
Lab Test for Oxidation Stability to Reveal Anti-Oxidant
Depletion and Oil Deterioration (Ref ASTM Tests D 943-
81 for New Oil and D 2272-67 for Used Oil).
Any other test/frequency of test ,recommended by
Turbine Manufacturer's Lubrication Group/lubricant
Supplier /ASTM Standard Practice/Company Technical
Expert.
28. 10. Analysis of Lubricant of Fan / pump /Mill
Particle count
Viscosity
Total acid measure
Condition of oil additives
Sediment in Lubricating Oils
Any other test recommended by OEM/ lubricant
Supplier
30. 11.1.Oil Analysis( Pulverizer Gearbox )
Wear Debris Analysis
The elements found in the gearbox oil analysis are
indications of the condition of the gearbox
components.
• Copper comes from thrust washers, bronze gears,
bearing cages, and other bronze or brass components.
• Iron comes from gears, bearings, worm shaft, and
piping. The iron may appear as rust.
• Lead in an oil sample indicates excessive babbitt
bearing wear and possible failure.
• Chromium and nickel in an oil sample may indicate
abnormal wear of rolling element bearings.
• The ISO 4406 Solid Contaminant Code is used to
quantify contaminants in the oil.
32. 12.Oil Specification-
KWU –BHEL Turbine 500 MW
Oil of viscosity OIL SUPPLIER BRAND
class ISO VG 46 IOC SERVO PRIME 46
shall be used. The
oil shall be a GULF OIL INDIA
LTD
GULF CREST 46
petroleum product CALTEX REGEL R&O 46
with or without
additives to meet CASTROL Castrol prefecto t-
46 super clean
the requirement of Indo mobil ltd Mobil DTE
this standard. medium/DTE
798
