Varnish Absorption Systems

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Varnish is a thin, insoluble film deposit that usually forms on fluid-wetted surfaces inside a turbine lube system, and even on bearings and servo valves.

Varnish is comprised of a wide range of oil additives and high molecular weight thermo-oxidative fluid breakdown compounds that have limited solvency in the base fluid. These compounds are polar in nature and begin to migrate from the base fluid to the wetted surfaces over time, depending on the system and fluid conditions and their polar affinities. The chemical compositions of these insoluble materials may vary depending on the turbine operating conditions or the fluid base stock and additive type.

Initially, these surfaces show up as a gold or tan color and build up to darker gum like layers that eventually develop into a hard, lacquer-like material.

Lubricants and oils that have experienced severe oxidations and heavy varnishing may not be adequately reclaimed or filtered and as a result may not be able to continue providing a useful service to the user.

However, in most cases, varnish and other soft contaminants can be removed from the oil and the oil can be returned to service.

Two common methods of varnish removal are electrostatic separation and absorption.

Under electrostatic separation processes, electrostatic separators run on a low-flow, offline, or kidney loop installation. They also operate on the premise that charged particles precipitate towards a collection media or plates of the opposite charge.

There are, however, a number of problems that come with using electrostatic separators, including a high purchase cost, high operational costs, low varnish holding capacity of collection media, a drop inefficiency with the presence of the water in oil (500 PPM or greater), low flow rates, and complex control systems.

Absorption systems, on the other hand, are able to provide a higher range of flow rates— from low flow under 5 gpm to high flow at greater than 50 gpm.

A high-density, depth-type cellulose filter is most commonly used in off-line type absorption.

With this system, it is possible to combine particle, moisture, and varnish removal all in one system, but doing so can require more than just a normal physical force used in common particle and moisture removal processes such as impaction and absorption.

For absorption systems, we recommend the method of Ion-exchange for varnish mitigation or removal.

Under this method, selective ion-exchange resins are formulated specifically to absorb varnish in its porous structure. This absorptive nature is due to the unique polar attraction between the ion exchange resin and the varnish contaminants.

This process offers a number of benefits: First, because of the large amounts of surface area by volume, this process is highly effective. Second, because selective resins are generally mass produced they have become a very cost-effective solution to fix contamination problems. Lastly, our systems use a large amount of ion-exchange resin media combined with oversized high-efficiency post filters to bring out the most from your fluids.

At Hydrocarbon Filtration, we offer absorption both as the primary mechanism for varnish mitigation, as well as a means to increase performance.

The very first stage in our Varnish Absorptions Systems is a prefilter, which acts as the primary defense against contaminants. This is followed by one of our regular absorption filters.

For added protection against contamination, we recommend lowering the temperature of the fluid to help remove the varnish from the solution more efficiently. This process is quite similar to how you would let emulsified water cool and settle out of suspension and into a free water state.

Lowering the temperature and allowing a dissolved solution to come out naturally is much more efficient than most other methods. Once water has settled, it is much easier to drain using gravity.

The final stage of our varnish removal system is a high-efficiency Beta greater than 1000 micro-glass filter elements to ensure a very low particle count.

Additional options for our Varnish Absorption Systems include:

  • Combination Kidney Loop Filtration for Low Particle Counts with Varnish Absorption
  • High performance particulate removal with Beta(x) > 1000 Post Filtration – for Low Particle Counts
  • High varnish holding capacity
  • Varnish Removal Cartridge replacement does not require a winch or lifting system.We have easy to grab handles and each cartridge is under 40 lbs.
  • Presence of water in the oil (500 ppm or greater) is not detrimental to performance.Recommendations are to keep applications lower than 100 PPM to maximize lubricity of oil and minimize varnish propagation.Can do so by using a Vacuum Oil Purification System.
  • Various flow rate options from 1 to 50 GPM.
  • Simple Control Systems.
  • Cost effective operational and purchase cost.

Varnish can come in contact with your oil for a number of reasons. Here at Hydrocarbon Filtration Systems, we have 4 proven methods of removing problematic varnish, and they all come in one system!

  • Cooling your oil is a tried and true way of separating varnish from your solution utilizing the proper method of downstream filtration.
  • When using the absorption method, your oil will typically clear up and become brighter than before. We use prefiltration to help perform this function.
  • By using resin media in the absorption process, we are able to better remove varnish from your systems.
  • The final stage of our varnish removal process is to use absolute rated micro-glass filter media to provide a final polish and low particle counts.

Our 10 GPM Varnish Absorption Systems came with a wide array of customization options.

We offer these systems in 5, 10, and 15 GPM flow rates, all with our patent pending Resin-Based Polar Attracting Varnish Removal Technology.

Our 10 GPM system also includes Dual Varnish Absorptive Housing, measuring 20" in diameter by 40" in length, as well as a 640 Series Pleated Micro-glass Filter Housing.

Two Varnish Removal Elements with 5,000 gallons of Turbine Oil are designed to lower your varnish MPC values from MPC=42 to less than 25 MPC. An additional two elements may be required to bring it down to less than 15 MPC.

With our Varnish Absorption Systems, particulate is reduced with a 5 micron Beta ( c ) greater than 1000 Micro-glass Filter Element in our 640 Series Filter Housing from ISO 21/19/18 to as low as 16/13/10.

Please note that in many applications where water is greater than 500 PPM, a Vacuum Oil Purifier is required to further dissolve then water under 100 PPM.

Varnish Mitigation Systems can also be used as an in-line filtration process to transfer fluids between reservoirs. This process may also be known as Kidney Loop Filtration and is very similar to our own kidney's process of circulating blood throughout the body. After 10 to 20 passes, particulate contamination will generally meet or exceed new oil cleanliness results.