Filtration: How Much Is Enough?

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One of the most common concerns about oil is whether or not it’s possible to over-filter it. Some are of the opinion that maximum filtration is the best option, while others say that less is more. So which is the right answer? Increased life expectancy of equipment has been the result of using cleaner oils. However, there are also considerations which need to be made if the goal is to meet ISO cleanliness codes.

The Tolerance Of The Machine

Regardless of the equipment you are using, its tolerance should be a key consideration. What does it need in terms of oil cleanliness? In the case of hydraulic systems, the requirement for clean oil is very well known. And the cleanliness requirement for the oil in a hydraulic system is very high when compared to the oil cleanliness that may be needed by something like a gearbox.

A machine’s tolerance will also depend on how old it is, how much the equipment would cost to replace and how critical clean oil is to overall operation. All of these things should be taken into consideration when determining the right level of oil cleanliness.

The Right Filter

Upon determining the tolerance of your machine, you must choose the best filter for that tolerance. It is true that the micron rating of the filter will determine its performance, but you’ll also need to look at the beta ratio. The micron rating will communicate the coarseness or fineness of the filter media, but the beta ratio will tell you how efficiently a filter will catch particles at a particular micron value.

Sub-micron filtration is possible with some filters. The more aggressive a filter is, the higher the likelihood that they will strip out additives, which can negatively affect the health of the lubricant. As well, the protection of machine surfaces can be compromised when a chemically active filter is used where fluid contains polar additives.

Filter Quality

When choosing the right filter, one thing to remember is not to compromise on filter quality. It may be that a universal filter will appear to look and fit the same, but it’s important to keep in mind that it likely won’t have the structural features you may be looking for, such as an O-ring protected bypass valve. In this example, installing the universal filter could risk pressure dropping in the system, which could lead to the oil being pumped out

Filter Performance

It is true that filters undergo testing before they are sent for sale. These tests are completed to rigorous standards and ensure optimal reliability, performance and service life. Choosing a universal filter may not offer the same guarantee.

Not only that, but most OEMS employ advanced planning tools when creating their filters. The control plan is one example of this. This plan outlines which controls were in place during the process for the testing, assembly, handling, manufacture, painting and shipping of the filter. This plan is put in place to ensure that relevant specifications are met.

Filter Fit

Ensuring the right fit is another consideration where the right level of filtration needs to occur. Here again, it’s important to choose products other than those deemed to be universal. However, fit can be difficult to determine with some filters unless regular particle counts are taken from the machine where the filter has been installed.

The bottom line is that clean oil is, in fact, better than oil that isn’t clean. This is true always. But there must also be a balance between the cost to clean machine oil and its oil cleanliness needs. This will differ with each piece of equipment, and as such, the needs of each will need to be considered separately.

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