|
Interpretation of test
data and recommended action on Petroleum Lubricating oils for
steam turbine |
|
Test |
Warning Limits |
Interpretation |
Action |
|
Appearance |
Hazy |
oil contains water, solids and or air |
Investigate cause, Check water
content first |
|
Odour |
Unusual smell, i.e. pungent, burnt,
rotten eggs or solvents |
This represents a change in the oil,
possibly as a result of degradation, high temperature, bacterial
growth or contamination respectively |
Investigate cause, Check TAN, water
content or flash-point |
|
Colour ISO 2049 |
Unusual and rapid darkening |
This is indicative of :
a) Contamination or b) excessive degradation |
Determine cause and rectify |
|
Total acid number (TAN) ISO 6618 |
Increase over the initial values by
0,1-0, 2 mg KOH/g before 20000 h of operation
Increase over the initial value by 0,3-0, 4 mg KOH/g at any time |
This represents abnormal
deterioration.
Possible cause are :
a) very severe system;
b) anti-oxidant
depleted;
c) oil contaminated
Oil at end or approaching end of service life but c) or d) above
may apply
|
Investigate cause. Increase frequency
of testing.
Compare with oxidation stability data.
Consult with oil supplier for possible re-inhibition
Look for signs of increased sediment on filteres and centrifuges.
If so or if oxidation stability is less than warning limits,
review status with oil supplier. Increase oil test frequency if
left in system |
|
Sludge IEC 422 |
Detectable |
Excessive degradation |
Check oxidation stability remaining |
|
Particle counting ASTM F 312 ISO/DIS 4407 ISO/DIS 4408 |
Exceeds accepted limits
*,
for example 15/12 ISO 4406 or SAE J 1165 |
Source of particulates may be :
a) make-up oil;
b) dust or ash entering system ;
c) wear condition in system |
Review limits with equipment manufacturer and if required identify
particles. Locate and eliminate source. Clean system oil by
filtration and /or centrifuging |
|
Viscosity ISO 3104 |
20% from original oil viscosity |
a) oil is contaminated
b) oil is severely degraded, or
c) wrong oil is added |
Determine cause. If viscosity is low determine flash-point. Check
demulsibility. Change oil, if necessary. |
|
* Limits will depend on method used ( consult
equipment manufacturer or oil supplier). |
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Petroleum Lubricating Oils for Steam Turbines |
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Oxidation stability
remaining ASTM D 2272 (RBOT) or IP 328 |
Less than 50% of
original value before 20000 h of operation
Less than 25 at any time
Less than 10 h at any time |
Above normal degradation
Together with high TAN indicates oil nearing and of service life
Together with high TAN indicates oil nearing end of service life |
Investigate cause,
Increase frequency of testing. Consider reinhibition.
Resample, If same consider oil change
Resample, If same consider oil change |
|
Water content ISO/DP
6296 |
Exceeds 0,2% |
oil contaminated or
degraded.
Potential water leaks, system malfunctioning |
Check water separability.
If unsatisfactory, check for source of contaminants.
Compare with other test data indicating degree of degradation.
Remove water and watch system carefully |
Rust test ISO 7120
Procedure A |
Light rust before 20000
h of operation
Light rust after 20000 h of operation |
The system is wet and/or
dirty, not maintained properly, and the additive is washed out
Normal additive depletion in wet system |
Investigate cause and
make necessary maintenance and operating changes. Resample and
recheck rust test. Consult oil supplier regarding re-inhibition if
test result unchanged
Consult oil supplier regarding re-inhibition |
Water separability ISO
6614
DIN 51589 |
60 min
600 s |
Oil contaminated or
degraded |
Compare with other test
data indicating degree of degradation.
No action required if water content is acceptable |
Foam test
ISO/DIS 6247 |
Exceeds following limits
:
Seq. I : 600/0 |
Probably contamination
with solids or wrong oil. In new turbines residual rust
preventives absorbed by oil may cause problems |
Watch oil in the system
Rectify cause. Check with oil supplier regarding inhibition |
Air release DIN 61 161
ISO/DIS 9120 |
it is required
6 min for VG 32
10 min for VG 46
12 min for VG 68 |
Contamination or
degradation |
Watch the system as
required. Rectify cause. Compare with other test results. |
|
Flash point ISO or ISO
2719 |
Drop of 300C
or more compared to oil |
Probably contamination |
Determine cause. Check
viscosity to see if solvents are present. Consider oil change |
|
Reference : CEI IEC 60962 fro Maintenance and use guide for
petroleum lubricating oils for steam turbine |
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