Water separator/diesel filter

No they don't. Possibly because, like me they don't think they do very much on diesel that a 10 won't do. The standard element for them is in fact 10 even in their turbine range. The next is a 2 for final filtration. The 5 micron ones I have are Sepor actually because I had them available in my "bosuns locker" left over from another job when I built the boat. When I run out of elements in about 2099 if I am still alive I might change them!
 
No it doesn't Piers and I see that the main argument for using a 2 comes from you on that thread. I believe you are wrong for the reasons stated. I also think the extract below from that thread, seemingly lifted from a website, says exactly what I am saying for very similar reasons. You don't seem to have any logic for a primary filter being 2 apart from seeing that some boat builders have fitted them as standard (in ignorance of good filtration practice in my view)

Most diesel fuel filter/water separator assemblies are sold with 2 micron filters however, the secret to the most effective and efficient fuel filtration is STEP-DOWN filtration. RACOR Filters states in their catalog, "A 30 micron filter (or primary filter) is used to filter raw fuel (or poor quality fuel) before it can be further filtered by finer medias such as a 10 or 2 micron. A 10 micron filter (or secondary and even final) is used to filter fuel which is known to be of very good quality. A 2 micron filter (or final filter) is the finest filtration available and is the last filter used prior to engine ingestion." In other words, the first filter in line from the fuel tank (primary) should have a larger micron rating than the filter (secondary) located further on down line or on the engine. The secondary filters are commonly 10 micron rated. If you use a 2 micron primary filter, a larger micron rated secondary filter will be doing absolutely nothing while reducing the overall efficiency of your system. The primary filter should be either a 10 micron or 30 micron rated filter. Keep in mind that using the small micron rated filters will also require more frequent filter changes. Exceptionally high fuel-flow engines, such as Detroit Diesels, should use the largest micron rating as the smaller sizes will restrict fuel flow and will need to be changed more often than necessary. Remember, it is fuel flow, not fuel consumption that determines the correct size of the fuel filter/water separator unit you use. Many engines use a fuel bypass system that routes unused fuel back to the fuel tank after it passes through the filtering system. Additionally, many small diesels are equipped with equally small fuel lift pumps. Using a small micron rated filter increases the load on these small pumps which can lead to premature failure. A properly sized primary filter used in conjunction with the engine mounted secondary filter will provide all the filtration needed to guarantee good fuel quality.
 
Hi boatmike. I can understand the argument, but owning a trawler yacht which are more popular in the States, and reading the articles by the leading trawler yacht mag in the States (Passage Maker), and being guided by the Sales Manager of Racor UK a few years back, I will be sticking with their recommendations of a 2 micron pre-filter. Seeing Nordhaven now fit these as standard (having accepted the argument as well) only reinforces my decision.

If, however, Passage Maker recants their articles, and Nordhaven recants their decision to go 2 micron, and the Sales Manager Racor UK recants his recommendations, I will change back to 30 micron.

As I have said before, at least I know that if I have a blocked filter,k the engine is safe I will not have to change the fine filter as well with the ensuing bleeding.

Shall we just agree to disagree?
 
In the end Piers you can fit what you want. It's your boat! Changing from 2 micron to 30 however would be highly radical. I would suggest 10. By the way the "sales" manager of Racor UK, if he did say such a thing, is totally at odds with the "technical" department in the states. You ought to ask him why, if that's the case, do they fit 10 micron elements in their diesel line filters as standard?
Boatmike out!
 
Boatmike, Piers:

Thanks for all your replies. Perhaps I should add "sorry I asked" !!!

I think I will stick with the 5 micron CAV for the time being - I have only just changed the filter. Perhaps next year I may change over, particularly if I crack another bowl.

John
 
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