While there are several lubricant-related issues that can compromise engine and engine accessory performance, water contamination of a jet oil is a serious and misunderstood phenomenon capable of causing expensive and extensive damage.
For instance, consider integrated drive generators (IDGs), which are essential to most commercial aircraft because they provide electric power. Due to the closed-system design of most IDGs, any water trapped inside can adversely impact jet oil performance through hydrolysis and increased acidity levels. Moreover, if damage becomes severe enough to warrant an unplanned removal of an IDG, costs may be as high as $250,000.
All aviation ester-based lubricants, including jet oils, readily absorb water and are vulnerable to contamination due to storage and handling procedures. Ester-based jet oils are most vulnerable to rapid contamination when stored in drums or service carts open to the atmosphere, regardless of being indoors or outdoors. Because of this, jet oil technicians are strongly advised to regularly test for water contamination in these containers when they are exposed to the atmosphere. These check-ins help ensure that jet oil meets equipment manufacturer specifications.
How quickly can water contaminate jet oils?
The rate of water contamination is temperature sensitive; in warm and humid climates, ester-based jet oils become contaminated as rapidly as 2,000 parts-per-million within a few days. When technicians apply contaminated jet oil to an accessory such as an IDG, the component will likely experience accelerated corrosion and lubricant filter plugging.
Water contamination can also occur in lower temperatures and various humidity levels. Although the water contamination will occur at a slower rate, the gradually accumulated water may still cause accessory failure before normal expectations.
Given the importance of maintaining the integrity of jet oil, here are three tips that operators can follow to minimize water contamination.
1. Ensure jet oil is stored in original, sealed containers as long as possible
Ideally, technicians can help ensure the best possible quality assurance by using jet oils taken directly from the original cans. However, if technicians only have open cans available, the jet oil should be used as soon as possible.
For airlines that use service carts to store large lubricant inventories or wish to reduce waste inside cans, drums or totes, lubricants should be:
- Equipped with a water-absorbing desiccant filter element offered by lubricant suppliers, or;
- Pressurized with dry nitrogen to prevent contact between the atmosphere and the lubricant.
2. Monitor jet oil condition while in drums, totes and service carts
There are a number of predictive maintenance tactics that can identify the presence and severity of water contamination.
Many lubricant suppliers and third-party laboratories provide aviation fluid condition analysis services, including quantitative tests for water contamination. For example, the Karl Fischer test yields a part-per-million (ppm) quantity of water that allows analysts to compare contamination levels to equipment manufacturer fluid condition limits, helping determine the severity of contamination.
Today, digital monitoring technology simplifies and improves the predictive maintenance process for technicians. While intricate laboratory test results may require up to five days to process, the use of portable, on-site analysis equipment is designed to provide a high-level assessment of fluid condition within minutes. Together, digital technology and laboratory analysis can help technicians accurately assess the condition of their lubricants.
3. Leverage your lubricant supplier’s resources
Fortunately, technicians can also lean on lubricant suppliers to assess oil and component condition. During the lubricant selection process, the supplier’s team of highly-trained engineers should work with quality assurance and line maintenance personnel to provide training on proper product handling and to establish the routine sampling program. Through this program, the supplier’s engineers can ensure that maintenance technicians understand proper sampling technique (bad sampling yields misleading results), assist with interpretation of test results, and share best practices to solve specific contamination problems.