Water enters hydraulic oil primarily through the reservoir. Specifically, the main point of entry is through the reservoir headspace. Hydraulic systems often use breather caps on reservoirs to allow air to move in and out as the oil volume changes due to thermal expansion, contraction, or cylinder actuation. Unfortunately, these breather caps can also allow moisture (and particles) to enter.
Major Entry Points:
The primary way water gets into hydraulic oil is via:
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Reservoir Headspace: The space above the hydraulic fluid in the reservoir.
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Breather Caps: As oil levels fluctuate, air is drawn in and expelled through the breather cap. This incoming air can carry moisture which then condenses inside the reservoir.
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According to our reference, many systems are equipped with breather caps that facilitate this air exchange, unfortunately introducing moisture and particulates.
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How Water Entry Happens:
- Condensation: When warm, humid air enters the cooler reservoir, the water vapor condenses into liquid water.
- Breather Cap Ingress: The breather cap, designed to equalize pressure, allows humid air to enter as oil levels change. This is a significant way water gets into hydraulic oil.
- External Contamination: While less common than reservoir entry, water can enter through leaking seals, accidental spills, or improper storage of oil containers.
Table Summarizing Water Entry:
| Entry Point | Description | Mechanism of Entry |
|---|---|---|
| Reservoir Headspace | The space above the oil in the reservoir | Air entering through the breather cap carries moisture, which can condense. |
| Breather Caps | Designed to allow air movement due to oil level changes | Allows moist air to enter as oil expands/contracts. |
| External Sources | Leaks, spills, or contaminated storage. | Accidental introduction of water into the system. |
Practical Insights:
- Regular Inspections: Monitor the hydraulic oil for signs of water contamination. This includes checking for a milky appearance, which indicates water in the oil.
- Use Desiccant Breathers: Using breather caps containing a desiccant (drying agent) can reduce the amount of moisture entering the reservoir.
- Maintenance: Proper seal maintenance and cautious storage of hydraulic fluids can minimize external contamination.
By understanding how water gets into hydraulic oil, preventative measures can be taken to maintain system integrity and longevity.
