Lubricant breakdown
accounts for more than 50% of your machine failures.
Lubricant Breakdown
Premature
failure from lubricant breakdown is the
most common cause of machinery failure, because it is largely misunderstood
and ignored. Here are some clear signs for
you to look for a problem without waiting on lab reports:
WARNING SIGNS:
·
Change
in oil colour
·
Strong
or burnt odour
·
Change
in oil consistency
·
Sludge
and deposits on lube tank walls and floor
·
Visible
contaminants in the sample bottle
Any
of these generally indicate that your oil has undergone a chemical change and
will no longer perform to the standard it was designed to. Breakdown of the oil can occur from
particulate contaminant, fuel or gas entrainment, oxidation and thermal stress,
but the most common cause is from water contamination.
What is varnish?
Varnish
(also known as sludge, tar and lacquer) is a soluble and insoluble
contaminant made up of by-products of oil degradation.
It
can appear as resinous, sticky, tacky or a gel-like substance that settles or
plates out on the surfaces of the lube system.
This can cause ‘stiction’ on servos and affect clearances and tolerances
in bearings and hydraulic control systems and valves.
As
oil degrades, it consumes its additives packages and antioxidant properties and
waste by-products are formed, creating sludge and varnish. You will have seen
it in hydraulic components, inside engine rocker covers and on journal bearing
surfaces or sumps.
There are many causes of
varnish and sludge, but clean oil is not one of them!
Is your system susceptible?
There
are a number of explanations for why lube oils suffer from high rates of
varnish. If your system ticks any of these boxes then you should
ensure your lab is testing for varnish potential:
 |
| Effect of varnish on equipment |
ü Visible deposits or staining
of lube circuit components
ü Switched from Group I to Group II or
blend of oils
ü Gas turbine or hydraulic application
ü High flow rate from a small
lube reservoir
ü High operating temps
ü Your chosen oil brand is
predisposed to varnish formation
The effect of varnish on equipment
If
left unchecked, varnish can propagate at an exponential rate, creating hot
spots, prematurely plugging filters or oil gallery orifices, and coating heat
exchangers and rendering them thermally inefficient. Hydraulic control systems
and valves can gum up or seize, causing unit trips and starting faults. Also, hard particles canadhere to varnished
components and cause premature wear.
The
cost of a gas turbine or hydraulic system not starting immediately can be
enormous as these are the assets that are designed to work at the press of a
button to meet supply requirements.
All
lubricating systems are subject to varnish potential if not maintained. The biggest cost to industry from varnish is
unscheduled downtime and lost production. There is a yawning cost-gapfrom an unscheduled
shutdown or unit trip, in comparison to condition monitoring and cost of varnish
mitigation.
 |
| Effect of varnish on equipment |
Varnish Detection
If
you suspect that varnish could be a problem then additional laboratory analysis
can identify varnish potential within your system. Sometimes, it can be as simple as pulling
filters and strainers and visibly observing the flakes and sludge indicating the
oil has broken down. Check your oil
sample bottle & sheet to see if your lab can test for these:
Membrane Patch Colorimetry (MPC)
This
is an excellent test to determine varnish potential. It is very sensitive and literally assesses
the colour spectrum of the oil. MPC
analyses (L) white to black, (a) red to green, and (b) yellow to blue scales
providing information on not only the seriousness of varnish found but the
likely cause.
High L = presence of soot, evidence of
micro-dieseling, spark discharge, thermal stress.
High a = diminished EP additives, likely to
produce sludge
High b = sticky, gummy deposits.
 |
| MPC Patches showing varnish potential high to low: results are 52, 44, 32, & 21 respectively. |
Remaining Useful Life Evaluation Routine (RULER)
The
RULER test quantitatively measures the remaining antioxidants concentration in
the oil, and as it says can determine ‘the remaining useful life of the oil’.
This is a comparison test, so ideally requires the original base oil to be
supplied.
Other Tests
MPC
and RULER should be enough, however other methods to determine varnish
potential can include ultra-centrifuge, particle contaminant levels, TAN (Acid
number), moisture testing and FTIR.
What should you do if you have
varnish?
Don’t
ignore it…
Varnish,
if present in a lube system must be managed and controlled.Predictive
maintenance of your unit is far cheaper than reacting to an event, if the cues
were there and were ignored the flow on effect could be significant.
Can
you live with a major breakdown?
If
you do no nothing, varnish will
cause the machine to suffer a breakdown or component failure, at potentially
huge cost. You cannot predict when the
failure will occur, but it will happen… guaranteed. Get the problem resolved, send us your lab
reports, RCA and specs and we can assist.
What solutions can be deployed?
Specialist
filtration
can remove varnish from a system. No two
systems are the same, so a tailored solution is needed. Your existing oil may or may not be able to
be renewed depending on the type and seriousness of the contaminants. Specialist filtration of the lube tank oil can
remove varnish plated out within the entire lube circuit. This process will take time and may need to
be a permanently installed solution.
In
circumstances where the oil is heavily contaminated and the additives packs left
with Elvis, then the oil will need to be replaced. When this occurs a chemical additive,such as Boost VR or Exxon System Cleaner, can be used to sacrificially
drag the varnish contaminant out with the outgoing oil.
There
are several filtration methods of removing varnish in service. A system such as VRS or ESP (Electrophysical Separation
Process) are the most efficient at removing the soluble contaminants in
suspension, and insoluble contaminates (the varnish and sludge that can be
seen). Prior to any varnish mitigation solution being deployed, the oil will
also require purification to remove any particulate, water or gas contamination.
Summary
Varnish
and sludge is like a cancer of the oil, if not treated, it spreads and further
propagates, to the point of machinery seizure and failure.
Varnish
detection and mitigation is far cheaper than an unplanned shutdown… as with
most things prevention is cheaper than the cure.
Don’t park the ambulance at
the bottom of the cliff!
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