Twin fuel filters - what microns?

[Robert Wilson]

The double cav type filter has a gallery in the top aluminium housing that supplies both filters at the same time, they are in parallel. They are usually fitted to engines over 100hp, or to increase service life of the filter. You can also get a triple filter housing. To have two filters in series you would need to install two single filter housings with a fuel line going out of one and into the other.

Bummer!
That is what I have now, so from what you say I have wasted £65.

Let's see what ASAP put in writing.
I'm probably a bit late for a refund as I bought it in November.
Hmmm.

 

[pvb]

Just to add further complication to this, it seems that there are various versions of the twin filter assembly. Whilst externally they all look identical, they will work in different ways according to the way in which the various galleries have been drilled. Mostly, they will work in parallel (hence the 90 LPH rating). But some do indeed work in series, if the correct holes have been drilled. There seems to be no easy way of identifying which version does what, and the filter assembly doesn't have a model number on it usually. The people who sell them don't seem to understand them fully, and certainly don't give much info on their websites.

So, if you still want a twin filter assembly which works in series, you need to quiz a supplier thoroughly. May I suggest you start with SSL Diesel, who are much cheaper than ASAP for similar units?

 

[black mercury]

You could still use your double cav filter, just install another single cav filter with the finer micron filter after the double filter. You just need a fuel line between them. It wouldn't do any harm installing the double filter, you just have an extra filter to replace, but those filters aren't expensive.

 

[Robert Wilson]

pvb (I'll contact SSL Diesel in the future!) and Black Mercury,
Thanks.

Here is my question to ASAP, and their response.
Dear sirs,
I hope you can help me with an apparent confusion with the“flow” through the above filter assembly supplied by ASAP last November.
When recently discussing with sailing friends I was informedthat the #302009 assembly has a “parallel flow” rather than the “series flow”which was what I thought I had ordered.
My requirements was/is for fuel to flow in from the fuel tank,through the first filter, onwards into the second filter (internally within thehousing) and then out to the engine/pump.
A number of people have stated that the arrangement is from thetank then simultaneously into both filters/chambers and then onwards to theengine/pump.
They have quoted Delphi CAV model#FDE-5874010 which does indeedhave a parallel flow sequence.
I am hoping that this quoted model is not the same as your#302009 and that the #302009 meets my requirements.
I, and various friends, would be most grateful to receive youradvice on the issue, for which I thank you in anticipation.
Best regards,
Robert Wilson,


Good morning Robert,
Thank you for your enquiry.
The 302009 filter flow is in series, so it will enter the firstfilter and move through to the second filter before going to the engine.
If you have any further questions, please feel free to contactus.
JasonChurch
[FONT=&#10]sales@asap-supplies.com
01502 716993
ASAP Supplies

I trust this clears-up the issue.


[/FONT]

 

[pvb]

Thanks for posting the ASAP response. If the filters are in series, how can they suddenly cope with double the flow rate of a single filter? And wouldn't it be nice if they specified on the website how the things work?

I also wonder why they illustrate these things with 2 identical 296 filter elements installed. What's the point of putting the fuel through one 296 filter and then putting it through another identical filter?

Edit: Incidentally, if you are to achieve series flow, you have to use a specific inlet and outlet, you can't just use any of the four ports.

 

[Robert Wilson]

Thanks for posting the ASAP response. If the filters are in series, how can they suddenly cope with double the flow rate of a single filter? And wouldn't it be nice if they specified on the website how the things work?

I also wonder why they illustrate these things with 2 identical 296 filter elements installed. What's the point of putting the fuel through one 296 filter and then putting it through another identical filter?

Edit: Incidentally, if you are to achieve series flow, you have to use a specific inlet and outlet, you can't just use any of the four ports.

Good point !

And yes, I shall pay very careful attention to which port(s) I use. Hopefully their will be clear instructions, somewhere!

Thank you for your interest, comments and advice - all of you.

 

[LadyInBed]

Is it possible to invert the unit and tip some water into the input side and see where it flows to?

 

[pvb]

Is it possible to invert the unit and tip some water into the input side and see where it flows to?

With a small torch, you can see into the various holes and discover where the interconnecting passages are.

The parallel flow filters are easy to spot, there's a short passage between the two filter heads (see arrows). So you can use either of the inlet ports, and either of the outlet ports (the outlet spigots are interconnected.

 

[black mercury]

Some good points there. If you blow through the inlet connection air will come out the small hole in the dished part of the housing above the filter, not the middle hole where the filter pushes onto, that's the fuel outlet after passing through the filter. Put your finger over these holes while blowing into the inlet, you will soon know if they are connected.

 

[pvb]

For completeness, here's a pic of a series flow filter. The fuel has to go in to the port on the right hand side of the pic, where it flows through the first filter and out via the central stub. The gallery carries the fuel to the second filter, where it emerges from the hole circled in blue. The fuel passes through the second filter and out via the central stub and then out of the port on the left hand side of the pic. These two indicated inlet and outlet ports must be used, otherwise the fuel will not flow correctly through the two filters. It's quite likely that different makes of filter head might use slightly different plumbing routes, so careful examination of the filter head is needed.

 

[Robert Wilson]

A sensible question, and three very useful hints.
:encouragement:

 

[zoidberg]

You could go 10 to 4 if you wanted, with a small engine. If there was any crap in the fuel the 10 obviously blocks up a little quicker, but still an acceptable combination.

I decided to have TWO primary/coarse filters, selectable and in parallel. That permits continued engine running if/when dirty fuel causes a partial blockage.

and

( during installation - W.I.P. )

The unit I had from ASAP functioned in SERIES. I took it to a learned Kubota specialist in Bath, who fitted a suitable screw which blocks the inter-gallery transfer. £10....
The copper T-pieces visible are crude support brackets. The red handles/cocks require careful ordering, for they are described 'ambiguously' by ASAP.

The 'upper half' of the following diagram was adapted to better suit my size of engine and fuel flow, and was helpful in visualising the concept:

 

[Robert Wilson]

I decided to have TWO primary/coarse filters, selectable and in parallel. That permits continued engine running if/when dirty fuel causes a partial blockage.

and

( during installation - W.I.P. )

The unit I had from ASAP functioned in SERIES. I took it to a learned Kubota specialist in Bath, who fitted a suitable screw which blocks the inter-gallery transfer. £10....
The copper T-pieces visible are crude support brackets. The red handles/cocks require careful ordering, for they are described 'ambiguously' by ASAP.

The 'upper half' of the following diagram was adapted to better suit my size of engine and fuel flow, and was helpful in visualising the concept:

Neat set-up, and good thinking.
I like your Farraro taps - how do they attach/grip the rubber hose? O presume it's standard size nitrile rubber?