Twin CAV type filter

stav

stav

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Does anybody know how these work? or rather could one be fitted with a course filter (30 or 10 micron) and then a fine filter (2 micron) and the fuel flow in through the course then the fine and then out.

They seem to be available online, ASAP and thornycroft.

Just an embryonic project at present but since about to spend a fortune on injectors thought about improving the filter system. Already have a single CAV filter and keen to reuse existing pipe work/disturb as least as possible.

Mercedes om636 42hp.
 
It looks as if these are arranged to filter in series so what you are proposing would work. However, most people fitting a dual filter system have them arranged in parallel so that, if one filter blocks, you can switch over to the other one, change the blocked element and continue un-interrupted. As prv has suggested, you've probably got a fine filter built in to the engine.
 
ghostlymoron said:
It looks as if these are arranged to filter in series so what you are proposing would work.
Click to expand...

I think not - these are described by ASAP as 90lph, as opposed to 45lph for the ordinary single CAV-type filter, so it would appear that they are plumbed in parallel, and wouldn't work with different filter ratings.

Having looked at the OM636 manual, it appears that most don't have a fine filter on the engine itself.

If I were starting from scratch, I'd probably go for a Racor spin-on filter arrangement; these can be bought with elements as fine as 2 microns.
 
They are not plumbed in series, but parallel , to present a greater filter surface area, for higher power engines of the period.

We have the same lid on sabre 150 hp, also fitted on the 225 I think.

Late starter has a good thread on more modern filtration equipement.


Dont know what 636 were fitted with but on the om314 we had there was a washable felt filter, by Mann
 
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stav said:
Does anybody know how these work? or rather could one be fitted with a course filter (30 or 10 micron) and then a fine filter (2 micron) and the fuel flow in through the course then the fine and then out.

They seem to be available online, ASAP and thornycroft.

Just an embryonic project at present but since about to spend a fortune on injectors thought about improving the filter system. Already have a single CAV filter and keen to reuse existing pipe work/disturb as least as possible.

Mercedes om636 42hp.
Click to expand...


No in a word.
 
Without going into too much (boring) detail. We had our 1951 vintage tanks cleaned last year, fitted a Perkins water trap and twin CAV type filters. We washed the original rabbit fur fuel filter (true, not made up) in petrol and left it in place. No problem since. However, this coming season. The water trap is doing a grand job. The twin CAV type filters have done around 25 hours work since the twin tanks were cleaned. Before we go anywhere this year I want to change both filters, the first as a 'course grain' filter, and the second as something finer. What recommendations does anyone 'in the know' have. The engine is a big lump but only 30HP and doesn't drink much at all!

Hope this is not thread drift, it being the same subject
 
stuhaynes said:
The twin CAV type filters have done around 25 hours work since the twin tanks were cleaned. Before we go anywhere this year I want to change both filters, the first as a 'course grain' filter, and the second as something finer.
Click to expand...

Assuming these are separate CAV filters plumbed in series (not the dual filter the OP illustrated), you could use an ordinary 296 filter element for the first one and get a Racor 5 micron element for the second one.
 
pvb said:
Assuming these are separate CAV filters plumbed in series (not the dual filter the OP illustrated), you could use an ordinary 296 filter element for the first one and get a Racor 5 micron element for the second one.
Click to expand...

Pukka Delphi CAV 296 are rated at 5-7 um, use the HDF version and not a pattern equivalent. I would put together a switching parallel system and not worry about a series of different sized filters.
 
Hi, thanks for all the replies.

There is another filter on the engine but no idea of filter microns.

So it is just two filters in parallel so will ponder this..... But will also look at other options. I already have 4 spin on racor filters so could buy a housing but the filters seem rather expensive and more inclined to change cheaper more frequently.

Only ever had an engine stop once to a clogged filter and that was whilst suffering the dreaded bug.

Having been poking around this seems a good filter but is it worth the £150+ price tag?

Stage One: Separation: As fuel enters into the filter assembly; it moves through the turbine centrifuge and spins off large solids and water droplets which fall to the bottom of the collection bowl.
Stage Two: Coalescing: Small water droplets bead-up along the sides of the chamber and on the element, once heavy enough these too fall into the bottom of the collection bowl.
Stage Three: Filtration: Algae, rust and dirt are then filtered from the fuel by the Aquabloc element, as the elements are waterproof they are much more effective and long lasting than water absorbing elements.

http://www.asap-supplies.com/marine...lements/parker-racor-500fg-diesel-fuel-filter

And seems to be able to be fitted with a 2 micron filter?
http://www.asap-supplies.com/search/Racor+2010+turbine+elements/racor-2010smor-fuel-filter-elements

Thanks all.
 
It's certainly a good filter, but it's total overkill for your engine, and won't work well with it. The "turbine" stage relies on a reasonable flow of fuel to work, and your small engine won't pump enough fuel. Look at the rated flow of the filter - 227 lph max! Also note that the fuel pipe connections are 3/4"! A much smaller, cheaper filter would be a better choice.
 
Assuming that it is one identical filter following another then from what I have read the first one will remove a certain percentage of particles of a given size and the second one a further percentage.
I have seen this in my own fuel polishing system ( using a single CAV filter) where each pass improves clarity ( up to about 5 passes in really mucky fuel).
What I am suggesting is that even if the second filter is identical ( rather than finer) there will be an improvement in quality.
 
Well thanks again, never thought to look at flow rates before and use them to make comparissions, so always glad to learn something new. I think the conclusion is drawing to adding a Racor 100 sin on filter at some point and then use the finer filter. Especially as I already have a 4 filters in the garage.

Again Thank you and have enjoyed the learning curve.
 
I notice that the filters show with glass bowls. My insurance survey was a fail because the glass bowl was too near the engine. I now have to replace it with a metal bowl. If the filter is near the engine, then I suggest that you start with a metal bowl from scratch.
 
I would vote for clear bowl separator. You see what's going there, can drain the water and mud out, have some control. I still have the glass bowl (surveyors were happy, but then it's properly made boat); new filters have plastic ones, so non-breakable.
Who knows what will come out of the tank...
 
I fitted a parallel fuel systetem with on/off switches and use only one filter at a time. The reason I did it is that's what Mobos have, if one blocks just change to the other, but make sure to bleed both. On the subject of the filter on the engine I always used finer filters than the one on the engine, for the reason that it will take much longer to block and on our engine it was easier to change an external filter. I also agree with clear bowls, you can see water and dirt build up.
 
I recently bought a Lucas twin HDF296 unit with glass bowls, but notice that, according to the markings, it is a top-down filter. I think a bottom-up arangement would be better, so that water and heavy dirt would drop to the bottom without encountering the paper filter. Does anyone have an opinion on this ?
 
My last boat had CAV twin filters in series. One pipe in and one out exactly the same as a single element filter. Vetus do a nice dual in-parallel set with change-over valves and vacuum gauge to indicate when element is becoming blocked.
 
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