Assessing oxidation condition and lubricant refreshment in turbine oils
March 2023Maintenance, Test & Measurement, Calibration
In turbines, lubrication undergoes a hydrodynamic regimen in which wear arises only after very poor lubricant condition. Conversely, the main root cause of turbine failure is the formation of deposits. Deposits produce several detrimental effects on these systems, such as sticking valves, orifice obstruction, and inefficient heat exchange.
In the case of gas turbines, where the lubricant suffers mainly from thermal stress, deposits are usually associated with the formation of varnish. Varnish is commonly associated with oxidation processes. It is composed of sacrificed antioxidants and oxidation products that coalesce to form sticky soft matter. The cost of varnish is very high, both in downtime and in equipment replacement. For this reason, monitoring of the oxidation condition of turbine oils is of utter importance.
To protect the base oil from oxidation, turbine lubricants are supplemented with about 1% of antioxidants. These are sacrificed to protect the base oil from free radicals and thermal and oxidative stress.
It is usually accepted that turbine oils can be used until their remaining active antioxidants are 25% of the original formulation. In many cases, however, depending on the oil, varnish issues arise before this point. Both laboratory tests and turbine oil condition monitoring, show that varnish may start to build up even when remaining antioxidants are as high as 60%.
In order to keep the operation reliable, the oxidation condition of a turbine must be kept between safe boundaries. This implies keeping a high dose of antioxidants, and the varnish potential low, to predict a high oxidation resistance.
Oil refreshment is a viable option to keep turbines free of varnish. By integrating the outcomes of lubricant analytics, such as RULER (Remaining Useful Life Evaluation Routine), RPVOT (Rotating Pressure Vessel Oxidation Test), and MPC (Membrane Patch Colorimetry), it is possible to estimate the refreshment required to keep the turbine under lean operation.
The lubricant’s oxidation condition can be effectively monitored through RULER, MPC, and RPVOT tests. Besides the nominal ASTM (American Society for Testing and Materials) value for these tests, significant information can be gathered from digging into these tests and integrating their outcomes.
One major application for this integration is the estimation of the lubricant refreshment for lean operation. Through laboratory tests, this can be accurately estimated, planning ahead of the upcoming maintenance intervention. This method is shown, together with case studies.
Sustainable water management Wearcheck
Analytical Instrumentation & Environmental Monitoring
Water sustainability is critical for the future wellbeing of people, land and marine ecosystems, and socio-economic development. WearCheck Water provides a range of water analysis techniques to determine water quality for various sectors, including mining, agriculture, domestic and the healthcare industry.”
Read more...WearCheck showcases condition monitoring at Mining Indaba 2025 Wearcheck
News
Scientific oil analysis, transformer oil analysis, reliability services and water testing & analysis – these were some of the condition monitoring techniques that were on show at WearCheck’s stand at the 2025 Investing in Africa Mining Indaba.
Read more...Upskilled workers add value to maintenance teams Wearcheck
News
Maintenance costs, which are traditionally grudge expenses for businesses or industrial operations, can be kept to a minimum by ensuring that maintenance crews are properly trained in key aspects of the condition monitoring process. Wearcheck offers a choice of more than 15 courses covering a wide range of topics, from general oil analysis to thermography, transformer maintenance and many other reliability solutions services.
Read more...UV water treatment system
Maintenance, Test & Measurement, Calibration
bestUV is an innovative manufacturer of professional ultraviolet (UV) water treatment systems for industrial markets.
Read more...WearCheck Water earns AdBlue/DEF analysis accreditation Wearcheck
Analytical Instrumentation & Environmental Monitoring
WearCheck Water recently became the first laboratory in Africa to be officially ISO17025 accredited to test AdBlue diesel exhaust fluid by the South African National Accreditation System.
Read more...WearCheck launches advanced thermography course Wearcheck
News
WearCheck recently launched a new training course, InfraFocus to upskill users of thermographic cameras. This highlights the best ways to capture thermographic imagery for use in a condition monitoring programme
Read more...WearCheck team celebrates diagnostic milestone Wearcheck
Motion Control & Drives
Condition monitoring specialist company, WearCheck celebrated a noteworthy milestone recently when diagnostic manager, John Evans diagnosed his three millionth used oil sample at the company’s Durban laboratory.
Read more...RS PRO a key partner for planned maintenance RS South Africa
Maintenance, Test & Measurement, Calibration
RS PRO, the own-brand of RS, offers a comprehensive selection of over 80 000 products spanning all industries and technologies.
Read more...WearCheck leads the way in condition monitoring Wearcheck
News
WearCheck is on a mission to safeguard the performance of components in industrial machinery by constantly monitoring its output and functionality to detect any potential niggles and rectify them long before they escalate into major problems.
Read more...WearCheck leads the way in condition monitoring Wearcheck
Maintenance, Test & Measurement, Calibration
Minimising maintenance costs of mining and power-generating machinery and maximising its operational efficiency – these goals form the foundation of the proactive/preventive maintenance services provided by the expert technicians at condition monitoring specialist, WearCheck.
printer friendly version