How do you know if you have varnish in your lube system?

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!

Why You Must Eradicate Contaminants from Your Lube Oil

Regardless of contaminant type, any lube system will be compromised if contaminated.  The effect can then compound as some contaminants have a catalyst effect, causing further problems.  The types of contaminants are quite varied including hard particles, soft particles, moisture and free water, gas and varnish.

Over the next few articles we will cover the range of issues that you should consider when managing your lubrication oil for close tolerance machines, hydraulics and gearboxes.

What you cannot see is doing the damage

Silica & Bright Metal at 100x
Let’s start with the types of contaminants:

1. Hard particles, such as Iron, Chrome and other metals, Silica and sand
2. Soft Particles, such as Copper, Tin and other soft metals, fibres
3. Soluble contaminants, varnish, incompatible top up lubes or additive packages
4. Gases and Aeration, process gases and aeration from ingression or inadequate system design
5. Water and liquid contaminants that can change lube viscosity

Hard particles will score and wear away lubricated surfaces, producing other contaminants in the lube oil, creating a snowball effect of increased wear rates. Wear particles and contaminants that oxidise, will deplete the antioxidants in additive packages, leading to varnish potential.

Soft contaminants have the potential to damage lubricated surfaces and increase wear rates, as well as depleting antioxidants, plugging filtration systems and galleries.

Varnish is a by-product of contaminants or depleted antioxidants, and a real concern in any lube system as the damage caused by varnish includes sticky and gummed valves and actuators, decreased tolerances which restricts lubrication to the wearing components causing higher operating temperatures.  Varnish can also plate out on bearing surfaces, causing hot spots and journal deformation. There are costs associated with varnish removal, but the real costs are downtime and loss of production.

Gas - In processing industries, where gas is present, such as gas compression facilities, lube oil can become entrained with gas, becoming aerated and not supplying the correct oil film or strength to the lubricated surfaces, as well as reacting with other contaminants in the oil to cause varnish potential. Aeration in hydraulic equipment also causes cavitation, prematurely wearing pumps, controls and work accessories.  Aeration and cavitation in lubricating oil destroys components and pumps, and reduces operating efficiency.

Moisture in oil is a common contaminant, as our climate can be humid with a wide temperature range.  In close tolerance rotational equipment, moisture levels below 200 ppm are acceptable but some OEM specifications allow for much higher.
                                                     
Free Water has a devastating effect on bearing surfaces, as the water droplet compresses and becomes super-heated into steam, exploding and 'etching' the bearing surface, rendering it unserviceable.

Magnified Samples (60x & 100x)

The following slides are all pictures taken by BioKem Oil Services in the last year.  They show a range of contaminants in 100ml samples of lube oil from gas compressors, turbines, steam feed pumps and gearbox lube oil tanks. For reference the black line shown is 44µm in width.

RUST – The presence of water speeds oxidation and additive breakdown of the oil and is considered a serious problem.  Particle size varies from 10 - 120 micron range

FIBRES - Typically introduced by improper cleaning and maintenance practices.

ASPHALTENES - particles are generally in the 0.5 - 2.0 µm range and they agglomerate into an oily sludge. This problem is made worse when free water is present.

SILICA & SAND – range of debris on this slide typically found airborne in Australia.

BRIGHT METAL PARTICLES - Typically comes from component wear. These particles are abrasive and, as a result, can lead to further wear and tear of the system bearings.

SOOT & SILT (<5µM), SILICA AND DUST PARTICLES - This is typically airborne contamination or part of sludge from the bottom of tanks.  Very hard and extremely abrasive against delicate components in boundary layer systems.

Non Magnified Samples

Sludge – This is a filter housing showing a buildup of oil additives after exposure to moisture (no magnification)

Varnish – Flakes of varnish plated out onto a filter and the varnish washed out onto an an absorbent towel (no magnification)

Examples of Damage

The next few articles will focus on how the different contaminants are caused, and the types of resolutions that can be performed.
If you would like further information on this article or others, please let me know or visit our website.

ENTRAINED GAS IN LUBRICATION OIL

BioKem Oil Services has specialist equipment that will remove 100% of entrained gas from lubricating and hydraulic oil.

BioKem has the equipment and the know-how to perform on-site oil filtration, dehydration and removal of entrained gases from your lubrication oil.  Entrained gas is not just problematic from simple air bubble generation, but can also ‘dilute’ or lower the mineral oil viscosity of the oil.

Is the presence of entrained gases affecting your lubrication circuit?

If the lubricating oil comes into contact with gas at an elevated temperature and pressure then gas entrainment may occur.  ‘Entrainment’ or ‘fluid aeration’ can cause numerous problems in hydraulic and lubrication oil systems including: unacceptable noise, poor component response due to spongy behaviour of aerated fluids, cavitation damage and severe fluid degradation.  If bubbles are present in the fluid in the reservoir, they may be sucked into the pump, where the bubbles’ volume will increase, due to pressure decrease along the suction line, and then compress again when a region of higher pressure is encountered. This compression is nearly adiabatic (the bubble gets hot, but does not materially increase the temperature of the surrounding fluid), resulting in tremendous localized temperatures at the gas-liquid interface. This may cause thermal cracking and sludge/varnish formation. In compressors, various process gasses, including soluble hydrocarbons like methane, butane, propane, petro-chemical processing sour gases, etc., are soluble in mineral oils and effectively cause ‘dilution’ or a lowering of the mineral oil viscosity reducing lubricant efficacy.

Cambridge Viscosity President Robert Kasameyer says that "when the compressor is running, the lubrication oil is hot and the entrained gas remains in gaseous phase. When the compressor is down, the lubrication oil cools and some of this gas can become liquid, which causes the lube oil viscosity to drop. Then, when the equipment is re-started but before it heats up, the equipment is operating with inadequate lubrication, which can be a disaster! If it makes it through this stage, the light hydrocarbons will again become gaseous, separating out of the lube oil, and the lube oil will regain its proper viscosity. But the damage will already be done."

The key thing to know is that once oil has been absorbed into the gas flow, it will not be collected by the oil separator.

Bubble removal devices can be used to mechanically remove bubbles from fluids however this is not a 100% effective method and foaming can occur.  Removal of entrained gas with a vacuum dehydrator provides for 100% removal of entrained gases and advantages such as the possibility of smaller reservoir size and lower overall system cost. 

BioKem VDOPS achieving ISO 10/8/7

The installation of an in-service, kidney loop, BioKem Oil Services vacuum dehydrator (VDOPS) will ensure that 100% of entrained gas and 90% of dissolved gas is removed and that the oil is free from not only gas, but is very dry and clean.  Our VDOPS systems are equipped with high efficiency pleated Microglass filter elements rated Beta(c)1000 per ISO 16889 to quickly and reliably achieve very low particle counts to meet or exceed an ISO 16/14/11 cleanliness level.

BioKem VDOPS 190l/min vacuum dehydrator

SGSpost filter Lab Test of 5,000l lube oil tank showing a moisture level of 8ppm!