Need help deciding what micron rating to use?

Some of the below, is information that we pulled directly from the Racor 7480G Racor-Parker Catalog on determining Micron size as well as some detailed information on understanding micron ratings.

[box type=”info”]Racor’s 2 micron filter medium should only be used in final or secondary filters where the fuel is first filtered by a primary filter.[/box]

A micron rating for a fluid filter is a generalized way of indicating the ability of the filter to remove contaminants by the size of the particles.  AIR FILTERS ARE NOT RATED BY MICRON SIZE. The micron rating does not properly or fully describe either the efficiency or the  contaminant holding capacity of the filter. What does the word micron mean? It is a unit of linear measure in the metric system used to measure distance from one point to another. It is used like the inch, foot, centimeter and millimeter to measure the length, width, or diameter of objects.

 A filter that is marked “10 microns” has some
capability in capturing particles as small as 10-microns. However, there is no one accepted method to measure and describe the size of particles that a filter can capture or the total amount of particles that the filter can hold. When you see the filter marked “10 microns”, you will not know exactly what this means unless you also have a description of the test and standards used to determine the filter rating. Filter micron ratings are often based on one of these methods, but with many possible variations:
A. Nominal Micron Rating (NMR) NMR usually means the filter can capture a given percentage of particles of the stated size. For example, a filter might be said to have a nominal rating of 90% at 10 micron.

B. Absolute Micron Rating (AMR) AMR is a single pass test and is obtained by passing fluid containing glass beads through a flat sheet of filter material. Any beads that pass through are captured and measured.

C. Multi-Pass Beta Rating (MPBR) The MPBR has been accepted by many machinery manufacturers, as well as filter manufacturers (but not used in a public way by most of them to identify or specify their filters), especially for filters used in fluid power applications; hydraulics, controls, transmissions, power steering and so forth. Single/Multi-Pass tests use contaminant specially graded by particle sizes added regularly in measured quantities to the fluid which is pumped continuously through the filter. Measured samples of fluid are taken at timed intervals upstream and downstream of the filter. The contaminant in these samples is measured for particle sizes and the quantity of each size or ranges of sizes.
Some suggestions:
1. Use filters of high quality.
2. Obtain filters by catalog listing, not just by “micron rating”. Other important qualities should also be considered.

3. Pay close attention to service intervals and good service practices for best economy of operation.

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Racor makes filters with various filtration efficiencies, but its standards for non-OEM (Original Equipment Manufacturer) are 2, 10, and 30 micron filter elements. The actual efficiency ratings for these are 98%, 95%, and 90% respectively. Racor also makes use of a 7 and 20 micron filter medium which are used to meet certain engine manufacturer’s requirements for a final filter and a primary filter. Racor’s 2 micron filter medium should only be used in final or secondary filters where the fuel is first filtered by a primary filter. The primary filter for a 2 micron final filter should use a 10 micron medium. The exception in using a 2 micron filter in place of a primary filter is to obtain high-efficiency water separation, and is usually used in marine applications where the fuel supply may be cleaner but also may contain water more often. If the installation can allow the use of a filter large enough, then a 2 micron filter can serve in a system as the only filter in that system.