The most common types of filters used to remove water from hydraulic oil are coalescing filters, desiccant filters, and water-absorbing filters. Each of these filters is designed to address different types of water contamination in hydraulic oil, such as free water, emulsified water, and dissolved water. Here's an overview of each:
1. Coalescing Filters
- Function: Coalescing filters are designed to remove both free and emulsified water from hydraulic oil. They work by causing small water droplets suspended in the oil to combine (coalesce) into larger droplets, which then separate from the oil due to gravity.
- How they work:
- The filter media causes small water droplets to join together, forming larger droplets.
- These larger droplets are easier to separate from the oil, either through gravity or additional filtration stages.
- Advantages:
- Effective at removing emulsified water (water dispersed in the oil at a microscopic level).
- Can also remove free water.
- Often used in industrial hydraulic systems that deal with varying levels of water contamination.
- Common applications: Large hydraulic systems, hydraulic presses, industrial equipment.
- Recommended filter types: Coalescer filter cartridges, coalescing separators.
2. Desiccant Filters
- Function: Desiccant filters are used to remove dissolved water from hydraulic oil, which is water that has mixed with the oil at the molecular level. These filters use materials like silica gel or molecular sieves to absorb the water.
- How they work:
- The filter media (typically silica gel or a similar desiccant) adsorbs the dissolved water from the oil as it passes through the filter.
- Once saturated, the desiccant media can be replaced or regenerated.
- Advantages:
- Effective at removing dissolved water from the oil, which is harder to extract than free or emulsified water.
- Ideal for systems with low but persistent levels of dissolved water.
- Simple to maintain and cost-effective.
- Common applications: Smaller hydraulic systems, maintenance of oil quality in sensitive machinery, systems with trace water contamination.
- Recommended filter types: Desiccant breathers, desiccant filter cartridges.
3. Water-Absorbing Filters
- Function: Water-absorbing filters are designed to remove free water from hydraulic oil. These filters contain special absorbent materials, like polymer fibers or specially treated cellulose, that capture water as the oil passes through.
- How they work:
- The filter media captures water droplets, either by adsorption or absorption, and helps separate the water from the oil.
- Advantages:
- Cost-effective for removing small amounts of free water.
- Works well for low water contamination in hydraulic systems.
- Simple and easy to use.
- Common applications: Smaller hydraulic systems, maintenance of oil in sensitive machinery, and as a supplementary filter in larger systems.
- Recommended filter types: Water-absorbing filter cartridges, breather filters with water-absorbing elements.
Choosing the Right Filter:
- Coalescing Filters: Best for systems with a mixture of free and emulsified water. They are ideal for large hydraulic systems where water contamination is higher and more complex.
- Desiccant Filters: Ideal for removing dissolved water from the oil. Suitable for systems that require continuous protection from low levels of water contamination, such as for maintaining oil quality in sensitive or high-precision hydraulic equipment.
- Water-Absorbing Filters: Best for small amounts of free water in hydraulic oils. Simple to use and cost-effective for smaller systems or intermittent maintenance.
In many cases, a combination of these filters may be used in hydraulic systems, depending on the type of water contamination (free, emulsified, or dissolved) and the level of contamination.
