Contamination Control for Turbine Gearboxes
22 Apr, 2021The most problematic of all gearbox issues is bearing failures, a challenge expected to increase as turbines get larger. A recent study concluded that the majority of turbine gearbox failures start in the bearings.
Gearbox reliability problems are being addressed with advanced designs, better materials and with another important strategy: oil contamination control. Next-generation contamination control technologies, already proven in industrial plants and mobile equipment, can essentially reduce particle and water contamination problems—the two most common and damaging oil contaminants—to zero.
Turbine gear oil filtration and cooling are often integrated. To keep gear oil cool, the heat exchanger transfers heat out of the gear oil prior to returning filtered oil back to the gearbox, typically keeping maximum oil operating temperatures below 70°c. To avoid cooling during cold starts, a thermal diverter valve bypasses oil around the heat exchanger until the temperature reaches a minimum of approximately 30°c to 35°c.
To keep gear oil clean, contaminants should be reduced to negligible amounts. Many gearbox manufacturers and bearing experts believe that to eliminate the negative effects of particle contamination oil, cleanliness levels should be maintained at ISO 14/12/10 max.(ISO 14/12/10 is code based on ISO 4406)
Maintaining this cleanliness level, however, requires higher efficiency filtration than has traditionally been used in turbines. Turbine gear oil filtration and cooling are often integrated. Coupling the pump and filter takes advantage of a common mount and negates the need for a pump discharge-to-filter inlet pressure line.
Problems of contamination to oils
Root Cause Failure Analysis: Besides gearbox repair, equally important is discovering the root cause of the gearbox failure in order to avoid unplanned machine downtime in the future. To pinpoint equipment failure one has to perform oil analysis, vibration measurements and thorough visual inspection, for instance examination of abrasive wear patterns and gear tooth pitting. These diagnostic techniques are usually required to monitor the condition of plant machinery and to control the causes of machine failure.
Gearbox lubrication – oil analysis
In many cases, gear and bearing problems result from contaminated or insufficient oil. Oil filter contamination could cause bearing failure and gear tooth damage. Sometimes insufficient lubrication causes metal-to-metal contact with abrasive wear as a result.
Oil analysis provides important information on wear modes and possible gearbox lubrication problems. On the other hand, visual inspections of wear patterns and gear tooth pitting can reveal lubrication problems e.g. oil leakage or improper lubricants.
(BEFORE & AFTER FILTRATION)
DIRTY FILTERS AFTER CLEANING 460 CST GEAR OIL IN IRON INJECTION CAST HOUSE 120 TON OVERHEAD CRANES LONG & CROSS TRAVEL GEARBOXES
Advantages of Oil Filtration
- Virtually eliminates oil changes.
- Reduces costly downtime(production)
- Saves on machine/gearbox maintenance costs
- Extends life of gearboxes
- Contributes to energy conservation
- Reduces pollution – ISO standards
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