User

I have seen much debate about using 2-micron pre-filters (I have a Fleming 55 and take PMM regularly), and I now use these in my Racors. However, in the UK, the feeling is strongly against this, with 30- or 20-micron being the recommendation.

Can I ask what the current thought is?

Piers du Pre

UK

The 2 vs. 10 or 30 micron primary filter element debate is one that has raged for several years now and I suspect the end is nowhere in sight, and it applies to all diesel engines, from 10 hp sail auxiliaries to engines like yours.  There's good reason for the confusion.  Many folks prefer to use a 2 micron filter because they don't want to deal with the on-engine, primary filter, and I can't say I blame them.  This filter is often difficult to change without introducing air into the system; it's usually expensive and sometimes difficult to access.   However, using a 2 micron element in the primary filter effectively reduces the area of the filter media by at least half, little if any dirt is making its way to the second filter, so it's not being spread out over the two elements.  This means, if you encounter gross contamination, you have that much less filter media with which to capture it.  Additionally, sequential filtration is scientifically proven to be more effective than single stage, fine micron filtration, but you don't have take my word for this, it's SOP for most engine manufacturers, including yours, as well as filter manufacturers such as Racor.  Additionally, this approach is also used by the semi-conductor and pharmaceuticals industries for obtaining exceptionally clean water, a necessary ingredient for their processes.  I detailed this philosophy in an article in PassageMaker approximately two years ago.

Steve D’Antonio, PMM Tech Ed.