Diesel filtration option?

maxim_rfeld · #1 10-10-2003

Hello everybody.

I would like to hear your opinion on the diesel filtration subject. As the rule goes, diesel engines usually have two filters. Primary filter - which is intended for water separation and coarse filtration (lets say 10 or 30 microns), usually located in the easily accessible place and piece of cake to change. Secondary filter (2 or 5 micron) - most often located in the back of the engine, often CAV type and pain to change.

Now the question – what are the disadvantages of having only one, 2 or 5 micron “primary” filter, which: 1)will do all the filtration; 2)easy to access and change; 3)easy to monitor (ex. Racor filter with the vacuum gauge and clear bowl); 4)even that you’ll have to change it twice as often as with the two filter configuration now you have much better idea about the sate of your filtration system and you won’t be caught of guard (in the bad weather, in the dark…) by clogged secondary filter, and it’s easy to change; 5)Overall cost for filter cartridge replacement will stay the same (you have to change it twice as often but with only one filter).

Looking forward to hear from you if anything is wrong with this idea.

Maxim.

Jeff_H · #2 10-10-2003

I would not call that the rule systems intended for offshore work. Generally I would expect to see two large capacity, fine primary filter/ water separators hooked in parrellel with a switch over valve and a secondary filter still in place. In practice the system would operate on one of the primary filters and when that one became fouled you would switch over to the other filter. That way you do not have to prime the engine or in some cases even shut it down. These should be installed so that it is safe to work with the engine running. The secondary filter should only handle very small quanities of material that may slip through during a filter change and should only be changed as a routine maintainance item.

Jeff

RichH · #3 10-10-2003

Filtration seqential ''trains'' are composed of a prefilter(s) + final filter. The prefilter is typically sized at 5X the micrometer retention size of the final filter and usually (not always) is the same surface area of the final filter. If the situation of the tankage is such that the pre and final filters plug rapidly you can add an additional prefilter of larger retention. This configuration will vastly increase the service life of the final filter as the prefilter has some capacity of retention rating of the final filter. The PRIME job of the prefilter is to extend life of the final filter. If you choose to use just a final filter, I''d recommend that you increase the surface area (& cost) by a factor of 5X or more.

Filtration is a three dimensional event so besides surface area (velocity of the fluid as it enters the ''pores'' ) one must consider the velocity of the fluid ''through the pores''. The internal velocity will establish how DEEP into the filtration structure before plugging occurs. If you want a long life filter, you must slow down the velocities so that the dirt is captured near the surface and not deep into the structure. A prefilter greatly enhances the life of the final filter because it removes much of the debris before it reaches the final stage... and the final stage can be run at greater velocity and with lower relative surface area.

If you''re looking for ultimate efficiency and cost savings, consider to put in an independent pumped recirculation loop (from the tank and right back to the tank) : transfer pump, 15-20µM prefilter, gages, etc. continually run the system when your engine is on - then youll only need a single 2µM before the injector pump and will rarely have to ever change it. The 15-20µM recirc prefilter will after a few total ''tank turnovers'' accomplish particle levels in-the-tank down to submicronic levels. Then, the final filter before the injection pump becomes just a "guard filter" and is rarely ever challenged with particles; all particulate removal work is done by the (much much cheaper) larger retention recirculation prefilter.

So to answer your question..... Definitely DONT just use a single final filter in the system, unless you put in a VERY LARGE surface area (costly) filter! Final filters are very expensive in comparison to larger retention filters. If you use a single stage filter, expect to replace it VERY often.

RichH · #4 10-10-2003

Thats definitely NOT the way to run a parallel filter bank!!!
Run BOTH filters simultaneously so that the service life is increased by a factor of 4 approximately. Apply a differential pressure switch across the filter bank (or use a simple pressure gauge which you look at every now and then) wired to an alarm. When the differential pressure reaches the set-point (well below the normal plugging value) you shift to single stage and change a filter, switch to the the second filter and change it;. Running with the most surface area available will exponentially lessen the filters to ''slam closed'' with debris - the lower the internal velocity the higher the propensity for the debris to be captured ON the surface of the filter thus aiding the filtering out of subsequent debris .... using dirt to filter dirt. If you run a parallel bank with only one filter in operation and one in a ''stand-by'' mode, expect to change out the filters 4 times as often.

"Yacht" filter systems/set are about 50-75 years behind normal state-of-the-art practice.

RichH · #5 10-10-2003

Thats definitely NOT the way to run a parallel filter bank!!!
Run BOTH filters simultaneously so that the service life is increased by a factor of 4 approximately. Apply a differential pressure switch across the filter bank (or use a simple pressure gauge which you look at every now and then) wired to an alarm. When the differential pressure reaches the set-point (well below the normal plugging value) you shift to single stage and change a filter, switch to the the second filter and change it;. Running with the most surface area available will exponentially lessen the filters to ''slam closed'' with debris - the lower the internal velocity the higher the propensity for the debris to be captured ON the surface of the filter thus aiding the filtering out of subsequent debris .... using dirt to filter dirt. If you run a parallel bank with only one filter in operation and one in a ''stand-by'' mode, expect to change out the filters 4 times as often.

"Yacht" filter systems/set are about 50-75 years behind normal state-of-the-art practice.

DuaneIsing · #6 10-10-2003

Thanks for the detailed info, Rich. I like the idea of fuel polishing you describe, but can you be fairly sure that the recirculation will process all the potential gunk in your tank? I have experienced the annoyance (on charter) of heavy seas stirring up the previously-benign sludge which quickly plugged the system.

Further thoughts? Maybe if you start with a clean tank and keep it polished, you would never have that problem.

RichH wrote: "...independent pumped recirculation loop (from the tank and right back to the tank)..."

TIA,
Duane

RichH · #7 10-10-2003

A recirculation system will be best able to recover a "particle storm" or slug of sludge/bioburden/polymerized fuel when it breaks loose due to its ability to rapidly ''turn-over'' a tank and return the resident particle load to a reasonable level. A recirc system will also greatly attenuate such deposits from forming ..... but you really have to start with a fairly clean tank. You really have to look at the (non-published) dirt capacity of the filter used in such applications. My ballpark estimate is: 10" polypropylene spun bonded @ 50 grams, 10" pleated paper @ 100-150 grams, typical Racor @ 25-50 grams .... once you reach the load limit, the filter cannot flow. So to anwer your question .... tell me how much crap you already have in your tank and I''ll tell you how many filters you''ll need; if its a clean tank we already know the answer and with a recirc. system will know that it will stay that way.
If you take on a contaminated load of fuel, the recirc system is also the best at fast particle reduction.

Without a recirc. system if a particle storm does happen youll need a truck-load of filters to keep up the replacment needs.

I have quite a sophisticated system: pumped recirc loop, tank vent filter, a to-the-engine line of - single stage Racor 2µM to a 3 gallon ''day'' tank which delivers to the lift pump, system is a pressure system that works on an automotive 12v fuel pump at the tank for NO air leaks, etc. The system is spphisticated but quite cheap to build.
Filters last much much longer if they are pressurized rather than the antiquated typical ''boat system'' model that works on vacuum from the lift pump.
eMail me direct and I will send you a line sketch of my system if you''re interested.

maxim_rfeld · #8 10-10-2003

Thanks everybody for the opinions and I should say that I am very impressed with the quality of them. For example, calling filter guys at NAPA I did not get any meaningful response on the same question.