The Hidden Dangers of Topping Up Your Lube Oil

Synthetic lubricants were born out of a need for better lubricating properties, and the unavailability of crude oil in Germany. Aviation was the first application for synthetic lubricants, as they are superior to mineral oils at cold start up and cold climates. Synthetic oils have a higher Viscosity Index, offering better viscosity stability at varying temperatures. Group IV synthetic oils are man-made from PAO’s (polyalphaolefins) and Group V oils are made up of polyesters, phosphate esters, di-esters, alkylated benzenes and other synthetic molecules.

Another way of comparing the various refinement of oil is to compare the oil to a fluid with balls of varying sizes in suspension. The lower the Group level of oil, the greater variety of ball size and shapes (which represent the types of molecules). Group 1 oils will have millions of differing atomic compounds (molecules) making up the oil. As the oil is refined, the oil is more uniform and the ‘balls’ are the same size. Synthetic oils have only one size ball.
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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!