TECH TIP Guidelines for Selecting a Filter Media
In our advisory roles in lubricants, we often are asked for advice on lubricant related products, like filters. Choice of filter can have a direct impact on how well a lubricant works. Here are some things to consider when recommending fiberglass or cellulose filter media:
Higher cost – while fiberglass filters tend to cost more, you usually get what you pay for.
More pores per square inch – this means the filter will have better efficiency and will have a higher Beta Ratio.
Consistent pore size – this means the filter will have a higher Absolute Filter Rating and be more exact in terms of the particle size it can filter.
Higher dirt holding capacity – having extra dirt holding capacity is always an advantage in case of delayed filter changes or unexpected contamination.
Tolerant to high temperatures – failures due to high temperatures are not common, but they do occur; in thermal oil systems, fiberglass media must be used. Failure also occurs when the adhesive used to seal the media filter to the canister fails.
Cellulose (Wood pulp)
Lower cost – while the cost per unit might be lower, when we factor in lower dirt holding capacity, lower beta ratio (filter efficiency), cost of less clean oil and increased change-outs, the actual life cycle cost can be higher.
Large fiber diameter size – the larger fiber size means more of the filter space is occupied by the fibers themselves, with less area available to hold contaminants.
Inconsistent pore size – because of this, they usually have a lower Beta Ratio
Can absorb small amounts of water – while this is an advantage, it can also be a disadvantage if large amounts of water encountered. Large amounts of water can cause the filter media to swell, resulting in a rapid rise in filter differential pressure, possible rupture, and a by-pass of the filter media.
Subject to fatigue and high temperature failure – cellulose filters are less resistant to high temperatures and acidic environments.
In the end, no filter media choice is absolutely right or wrong but by paying attention to it, we can help maximize the life and performance of the quality lubricants we sell.