Water may enter a hydraulic system through condensation, a damaged cooler or maintenance work. It can promote corrosion and change fluid behavior, yet an oil sample that looks clear can still contain dissolved water. The response should begin with measurement and source control.
Separate evidence from appearance
Record where and when the sample was taken, the operating temperature and whether the machine had recently been stopped. HYDAC lists Karl Fischer analysis as a way to determine water content; online water sensors often report relative saturation rather than a direct mass concentration. Those results answer different questions. A cloudy sample may indicate free or emulsified water, but visual clarity alone is not an acceptance test.
Engineering checks
- Compare the result with the fluid and component suppliers’ limits.
- Inspect breathers, cooler interfaces, washdown routes and tank seals.
- Check whether the fluid is compatible with the proposed treatment.
- Trend water readings with temperature and operating state.
- Review corrosion or filter changes that may indicate a longer problem.
Common mistake to avoid
Removing water once without fixing the entry path allows the problem to return. A fine particle filter alone may not remove dissolved water; choose equipment according to the water state and required final condition.
Data to send with an inquiry
- Fluid identity, volume and latest laboratory results.
- Sampling location and temperature.
- Known water-ingress events or cooler leaks.
- Target condition and available downtime.
Confirm the achieved oil condition with a follow-up sample, then monitor it through representative operation. For related selection guidance, see our oil cleanliness and filtration guide.
Technical references: HYDAC contamination guide; HYDAC oil dehydration systems. Cover: original conceptual schematic, not a product photograph.