ADDRESSING THE VARNISHING PROBLEM IN GAS TURBINES

Varnishing can lead to costly downtime, increased maintenance and major financial exposure for gas turbine operators. Castrol has the solution.

Castrol Perfecto XPG is at the heart of the Castrol solution to varnishing prevention. This high performance turbine oil is based on leading edge, well-proven technology. Its advanced properties maintain extremely low levels of total insolubles, reducing the occurrence of sludging and leading to a high degree of system cleanliness and freedom from varnishing of servo-valve components. 

TURBINE VARNISHING – THE PROBLEM

In the last 20 years, gas turbine technology has been developing fast in response to demands for ever greater efficiency.  Higher firing temperatures and greater responsiveness to fluctuating power demand have driven changes which stress not just the turbines but turbine lubricants as well.

Lubricants manufacturers have responded to the challenges, widely offering Group II base oils to make use of their inherently better thermal and oxidative stability. However, this move has resulted in increased insoluble formation and system cleanliness issues. In the worst cases undesirable sludge and varnish deposits are built up. 

Varnish generally tends to form in areas of high temperature and/or severe pressure fluctuation in the system, typically affecting on servo control valves, bearings and journals (i.e. generally areas of low clearance). Failure and malfunction of servo-valves due to varnish deposits on the oil-wetted components is a well-documented problem in gas turbine control systems, and is a significant issue affecting turbine reliability. 

Malfunction can cause increased maintenance costs from the need to clean tanks, repair or replace servo-valves and, in extreme cases, replace bearings. It can increase outages resulting in reduced availability and costly lost generation. What’s more, end-user operators can face major financial exposure, with the overall cost of a power plant trip being more than a $1 million of lost revenue and trading penalties in some markets.

PREVENTING TURBINE VARNISHING

TURBINE VARNISHING PREVENTION

Castrol Perfecto XPG is at the heart of the Castrol Absolute solution to varnishing prevention. This high performance turbine oil is based on leading edge, well-proven technology. Its advanced properties maintain extremely low levels of total insolubles, reducing the occurrence of sludging and leading to a high degree of system cleanliness and freedom from varnishing of servo-valve components. 

Castrol Perfecto XPG offers extreme resistance to varnishing through: 
  • The exceptionally low level of insoluble material generated by the oil in service
  • Advanced solubility characteristics of the highly refined base oil, ensuring that products of degradation are held safely in solution
  • The nature of generated degradation products inhibiting varnish formation
Other key advantages include: 
  • Enhanced thermal and oxidation performance
  • Latest technology, carefully balanced multi-component antioxidant system delivers enhanced oxidative performance with low total antioxidant level
  • Excellent solubility characteristics of base oil towards additives ensuring an extremely stable product
  • A high degree of system cleanliness
Our Castrol Perfecto XPG turbine lubricant is recommended for use in industrial gas turbines, especially under arduous service conditions of high operating temperatures and intermittent running or 'peaking' duty, providing reliability in operation and long service life.
 
Castrol Perfecto XPG is particularly beneficial where exceptionally low tendency to form insolubles, sludge and varnish, together with high oxidation resistance and long service life, are important. It delivers first-class air release performance, good resistance to foaming and excellent water separation properties. 

Castrol Perfecto XPG exceeds the requirements of GEK 32568 (applicable to GE 'F', 'FA' and 'FB' technology units – e.g. Frame 7F, 7FA, etc.), GEK 101941 (applicable to 'F' technology units with enhanced FZG requirement for load gearboxes) and also meets the more stringent requirements of GEK 107395.

The Castrol solution incorporates first-class services including:  

TECHNICAL REVIEW

Experienced Liquid Engineers work with you to fully understand your history of varnishing problems before making recommendations. Using your historical operational data and varnish related servo valve failures and trips, we will demonstrate the potential benefits of the Castrol varnishing solution to you. 

OIL CHANGE & TECHNICAL SERVICE

It is critical that when changing from existing turbine oil, the system is adequately drained and flushed before filling with the new charge of oil. 

For initial fills of new turbines or refills of existing turbines we provide advice on ‘best practice' for flushing, oil cleanliness, filtration, lubricant polishing, package, storage and handling, Oil Condition Monitoring (OCM), collection of samples and general lubricant ‘good housekeeping' to ensure optimum product performance.