Lube Oil Varnish Control Made Simple

Lube oil varnish -- it’s the 800-pound gorilla in your living room you refuse to acknowledge. The question is not “if,” but rather “when” varnish will be a problem for you.

Varnish forms because of lube oil degradation, largely from the extreme temperatures and oxygen existing in combustion turbines. Varnish buildup causes excessive wear on parts, can lead to bearing failures, and can cause critical components -- such as servomechanisms -- to seize. These failures are costly, not only due to the repair expenses, but also because of the off line lost revenue. Seaworthy Industrial Systems’ lube oil filtration system can control varnish from lube oil systems and prevent these varnish-induced problems.

Seaworthy’s filtration method has the highest varnish capacity, while maintaining the lowest cost, of any other varnish control system on the market. Its secret is its simplicity, which makes it a “plug and play” system. Unlike competing systems, Seaworthy uses depth filtration, rather than electrostatic or chemical methods. With few parts and no complexity, it requires practically no maintenance and has little chance of problems. Complexity brings risk. Simplicity defines low risk.

Field tests performed by a large U.S. utility company showed that in the first 20 days of operation, the Seaworthy filtration system reduced the lube oil varnish potential rating (VPR) by 24% - improving an “abnormal” varnish level to “acceptable”.

What is varnish and where does it come from?

Varnish results in a thin film deposit often found on bearings, servo-valves, and other metal surfaces. The film is made up of soft insolubles that fail to be removed by full flow filtration.

Thanks to advancements in high temperature-resistant materials, modern combustion turbines are able to operate at very high firing temperatures. This, in turn, causes high bearing compartment temperatures. As the lube oil flows into and around the bearings, it gets hot and mixes with air in the bearing compartments. Each time the lube oil passes through a hot bearing compartment, it oxides a little. This oxidation causes the early depletion of antioxidant additives in the early, and leads to the formation of insolubles, which are the beginnings of varnish. These early insolubles are soft and do not have a definite shape, so the full flow filtration systems on combustion turbines cannot remove the insolubles. If left in the lube oil, these insolubles will eventually stick to metal surfaces. Since most large combustion turbines also use their lube oil system to operate servomechanisms for fuel valves and variable vane actuators, filming can occur on these components and cause them to stick, malfunction, and eventually result in the engine tripping off line. Furthermore, varnish films will cause excessive wear to bearings, resulting in early bearing failures and unexpected maintenance requirements.

As mentioned, oil degradation is the primary cause of varnish; however, oil degradation itself is caused by several factors. Poor filtration will allow particulates, wear particles, and water to build up and contaminate the oil. Oxidation, high temperatures, and moisture will cause the depletion of antioxidant additives. All of these factors degrade the oil and allow insolubles to form. Furthermore, it has been found that wear debris -- especially of the sub-micron size -- acts as a catalyst for varnish formation.

Do I have a varnish problem?

All large combustion turbines with non-synthetic lubricating oil are vulnerable to varnish. As oil degrades, varnish is bound to form. The only question is: When will the problem hit?

How can you control varnish?

Varnish is composed of insolubles that have no fixed shape, so they simply “squeeze” through conventional filters, rendering them useless for varnish control. As a result, other filtration methods must be used. Current marketed varnish treatments are expensive, demand consistent maintenance, and are prone to expensive malfunctions. Products currently on the market include electrostatic precipitation systems and edge filtration units.

Electrostatic precipitation requires the use of complex and expensive components including PLCs. They also require high-voltage electricity to create positive and negative charges to particulates in the oil. Meanwhile, edge filtration methods have a very limited amount of filter surface area at the edge of the discs. As a result, they have low flow rates and are prone to clogging in applications when filming occurs as is the situation with varnish in the lube oil.

In contrast, the SIS method has no PLCs, no high voltage, and no complexity. It has the highest flow rate and the highest varnish capacity of any other system, and is not susceptible to clogging. The SIS configuration uses organic, rammed depth element filters to capture varnish, insolubles, water, and other particulates through the methods of absorption and adsorption. Magnetic filtration is added to further control very fine ferritic wear particles.

SIS has designed their filtration system to act in a side stream (kidney loop) configuration. Once connected to the oil reservoir, it is turned on and left on. With only a circulation pump and filter assembly, there is very little chance of error and no need for constant maintenance or expensive service technicians.

What else will the Seaworthy filtration system do for my turbine’s oil?

Seaworthy’s system provides a complete turnkey package to filter and extend the life of lube oil. The depth filtration elements will capture varnish, insolubles, particulate matter, and water, while its added magnetic filtration will catch wear particles of all sizes. Since ferritic particles act as catalytic sites for varnish formation, magnetic filtration can be considered the bedrock of varnish prevention. At press time, Seaworthy’s varnish filtration system is the only varnish control product on the market with magnetic filtration.

When first started, the SIS filtration system will begin to filter your lube oil, ridding it of varnish, particulates, and water. Depending upon the severity of the turbine’s varnish condition, the now clean lube oil will begin to dilute the varnish film on the turbine’s metal surfaces, drawing it back into the lube oil. Once again, the SIS system will remove that varnish from the oil. This cycle will continue to “self-clean” the entire turbine lube oil system.

For systems without varnish, or for systems that are now “clean” from the process described above, the SIS system will ensure that varnish buildup does not occur. This is accomplished by filtering the insolubles from the oil before they reach high enough concentrations at which varnish forms, while simultaneously using magnetic filtration to capture wear debris which would otherwise act as a catalyst for varnish formation.

In addition to varnish control, the SIS system will help to increase lube oil life. Since the cost of an oil change is prohibitively expensive for large combustion turbines (with several thousand gallon oil reservoirs), proper oil filtration to prevent oil degradation is a must. Since the SIS system captures insolubles, particulates, water, and ferritic wear debris of all sizes and shapes, oil degradation prevention is being addressed.

What’s the bottom line?

Seaworthy Industrial Systems’ lube oil filter is the simplest, easiest, and cheapest way to rid your combustion turbine of varnish, while also protecting it from future varnish problems. It will prevent costly trips off line due to varnish-related seizures, while prolonging the life of your turbine’s lube oil. Seaworthy’s filtration system is the simplest and cheapest way to get rid of that “800-pound” varnish gorilla.