A Proactive Approach to Treating Varnish Can Prevent Significant Downtime at Plants

Varnish is one of the most widespread issues in power plants. It’s the hard, oil-insoluble organic residue that cannot be easily removed from mechanical components. It typically occurs in turbines or compressors due to extreme temperatures, disrupting plant operations and causing downtime, which ultimately leads to revenue losses.

When varnish forms on a critical piece of equipment at a power plant, it creates a chain reaction of issues throughout systems. There’s the potential increase in labor, unplanned shutdowns, and extended lead time if replacement parts are not readily available, all of which translate to a spike in operating costs. And because varnish silently builds up on machinery, it can go easily undetected, which could leave plants scrambling at the last minute if they don’t have a prevention plan in place.

Plants can’t operate at 100% of their capacity, or produce all of their products, when they have to shut down a turbine or compressor due to varnish. Systems that develop varnish typically don’t last as long and require more frequent oil replacement. Varnish can create high bearing temperatures, cause servo values to stick, and create filter blockage. Plants have to shut down and replace the bearings or clean them out, which is not always effective. It’s important to mitigate the development of varnish and proactively prevent these issues that inhibit a plant from functioning optimally.

Unplanned shutdowns can also have broader implications, like preventing a plant from meeting stakeholder expectations and financial goals for the year. Limiting downtime is therefore critical for power plants to optimize efficiency and achieve the biggest cost savings.

Finding the Right Solution—At the Right Time

When it comes to optimizing plant efficiency, the right products—and the right timeline—can have a significant impact in mitigating varnish and varnish-related issues. Oil-soluble cleaners are good options for tackling varnish because they can be safely added to in-service oil without having an adverse impact on performance, unlike water-based chemical cleaners or more aggressive oil-soluble solutions. They dissolve varnish to prevent a sudden dump of contaminants from occurring.

Beyond having the best products to rid a system of varnish, taking a proactive approach enables plants to ensure they have clean oil before damage is done from advanced varnish formation. The sooner varnish is detected, the better chance a plant will have at cost savings from replacing equipment or oil. If a plant has an outage scheduled one month out, a service provider can implement a solution 30 days in advance and use the solution in the old oil to clean it up and then put the new oil in. Or, if a plant’s next outage isn’t scheduled for a year, the service provider can implement the solution a year in advance to keep the system going and prevent unplanned downtime. Planning these outages in advance is integral to mitigating varnish and any issues associated with it.

Optimizing Plant Efficiency

One solution we use at ExxonMobil to tackle varnish is our Mobil Solvancer product, a high-performance, oil-soluble cleaner for gas or steam turbines, compressors, and hydraulic systems to improve reliability and reduce the overall cost of operations.

The Mobil Solvancer product offers a cost-effective method to decontaminate lubricant oil systems in between oil changes. The product works to address issues related to varnish such as escalating bearing temperatures and avoid issues including re-adhesion, transfer of deposits, filter plugging, oil line flow blockage, and more. It’s fully compatible with in-service oil and can be added to quickly dissolve varnish and deconstruct organic deposits from equipment to help maintain the cleanliness of turbine bearings, seals, and hydraulic systems.

The Mobil Solvancer product supports oil conversions, alleviates operational issues due to varnish, and helps with oil life extension. In addition to improving equipment reliability, it does not require a sacrificial flush, so there’s very limited downtime and reduced costs compared to more aggressive solutions.

Eliminating Varnish and Preventing Downtime

Customers typically reach out to our team of engineers when they think they’ve detected varnish. At that point, we look at bearing plots and bearing temperature increases, run oil analysis tests, and walk through different scenarios to see which solution would be best.

Our team was recently approached by a plant looking for a solution to varnish that would allow them to avoid a post-flush oil change so that their equipment could remain in operation throughout the process. After running several varnish prediction tests, we detected varnish buildup in their system and determined that the Mobil Solvancer product would be the best solution for their needs.

We successfully got rid of the varnish and addressed other problems proactively so that when they did shut down, they wouldn’t have to spend extra time on high-velocity oil flushes and hire contractors to clean out all of the varnish in the systems or potentially replace the bearings.

This strategy led to savings and shorter downtime for the plant, allowing them to avoid running a sacrificial flush that would have otherwise been required with an alternative solution. As a result, the plant was able to come back online and resume production earlier than expected. They successfully reduced downtime by three and a half days and, because of their ability to forgo the sacrificial flush, saved more than 20,000 gallons of oil.

The best way to treat varnish is to prevent it from forming. By being proactive rather than reactive, power plants can maximize the lifespan of vital equipment to ensure service continuity, identify failures as they occur, reduce the need to replace parts frequently, and ultimately limit downtime to prevent revenue losses.

—Joel Scarbrough ([email protected]) is a Lubrication Engineer with ExxonMobil Product Solutions Company, a Division of ExxonMobil Corporation.