Varnish FAQs – How to optimise turbine operation


What is Varnish?


Varnish is a common issue in circulating oil systems. It can cause huge operational problems, which can cost businesses millions of dollars to rectify. Even the smallest amount of varnish in a system can result in erratic component operation such as valve sticking, poor heat exchanger performance and even bearing failure. These problems also lead to a shortened oil life and loss of equipment productivity.


Ways to mitigate varnish problems have consequently received much attention. Various methods have been used, but most start with removing accumulated varnish from the oil system before implementing prevention and control methods. The most commonly used method for removing varnish from circulating oil systems, such as turbines and air screw compressors, involves the temporary addition of cleaning chemicals to the system.


How do I know I have a varnish problem?


Symptoms of varnish deposits vary even between identical systems. Typical symptoms include sticky servo or thermostatic valves, sticking hydraulic cylinders, inefficient oil coolers leading to high oil temperatures, high bearing temperatures, and subsynchronous vibration in high-speed bearings and seals.


What tests will definitively prove I have a varnish issue?


Oil analysis test methods fall broadly into two types: those that predict the life of the oil and those that measure the current performance of the oil. Note the key word ‘oil’. The first test type will only indicate the varnish potential of the oil. At best, the second test type will only indicate the amount of varnish and varnish precursors in the oil. Neither test type provides an indication of varnish deposits on equipment surfaces nor whether such deposits are problematic. Oil analysis is therefore merely suggestive with respect to confirming that a system’s performance issues are varnish related.


There is no direct, definitive way of identifying varnish-related system issues that do not involve measuring critical parameters like valve hysteresis or oil cooler effectiveness or even tearing down the system to visually ascertain the root cause. 


Why should I clean varnish from my system?


Varnish affects both machine operation and the performance of newly installed oil. Removing varnish often restores machine operation, efficiency and prepares a system for better performance after an oil change.


How long will my system stay clean after I clean it? 


That depends on whether the root cause of oil degradation has been addressed. Identifying and eliminating the root cause of oil degradation specific to your system will greatly improve oil life and system cleanliness. Your system will stay cleaner for longer if you correct the system problems that damage oil and refill it with a high quality, varnish-resistant oil.


Many operators choose to use a chemical cleaner as part of every oil change process. Others choose to clean only when operational evidence of varnish deposits are present. Deliberate consideration of whether to clean or not should form part of the planning for every oil change.

What is VARTECH Industrial System Cleaner?


Texaco’s VARTECH Industrial System Cleaner is compatible with many in-service oils. At the recommended concentrations, it causes minimal filter plugging and has very good seal compatibility. VARTECH has shown deposit removal effectiveness in extensive comparative laboratory and field testing and is designed to dissolve varnish deposits from internal surfaces and then stabilise them for removal with the used oil. It has a viscosity of 53 cSt which helps make it effective in ISO 32-68 viscosity oil as it will not significantly affect oil viscosity at the recommended concentrations. VARTECH also has a minimal impact on lubricant water separability and on long term new oil performance in residual amounts up to 2%.


Where can I find more information on VARTECH? 


Learn how to protect your equipment from harmful varnish with our VARTECH solution, designed to significantly improve system cleanliness, and deliver longer oil life and system operation.