Lubricant breakdown accounts for more than 50% of your machine failures
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:Â Â
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 restiction 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:
Visible deposits or staining of lube circuit components
Switched from Group I to Group II or blend of oils
Gas turbine or hydraulic application
High flow rate from a small lube reservoir
High operating temps
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 can adhere 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-gap from an unscheduled shutdown or unit trip, in comparison to condition monitoring and cost of varnish mitigation.
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.
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.
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!
Next Article – Five important things to look for in a lube oil Lab Report
Ph 0466 625 225