Twin fuel filters

oldbilbo

oldbilbo

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What's to like?

I can see the merits of a pair in parallel, with the freedom to switch from one to the other should blockage begin to affect supply to engine. However, is there any merit in having them arranged in series, but with different grades of filtration?

Or should I simply have an inline 10 micron fine fuel filter downstream of the 40 micron jobs....
 
oldbilbo said:
I can see the merits of a pair in parallel, with the freedom to switch from one to the other should blockage begin to affect supply to engine. However, is there any merit in having them arranged in series, but with different grades of filtration?
Click to expand...

Can't see much benefit in that. I have 2 identical primary filters in parallel, with individual taps so I can isolate one and only use it if the other starts to get blocked. A vacuum gauge indicates if the filter in use is getting blocked.
 
pvb said:
Can't see much benefit in that. I have 2 identical primary filters in parallel, with individual taps so I can isolate one and only use it if the other starts to get blocked. A vacuum gauge indicates if the filter in use is getting blocked.
Click to expand...

What's a vacuum gauge and how does it work. Also how is it fitted.
 
It's very common to have a primary filter / water trap, mounted close to the fuel tank, and have a second engine-mounted filter as well.
But as pvb suggests, two filters in parallel, with individual control cocks makes it very easy to change filter elements without any fuss.
Better to have too many than not enough.
 
eidiohir said:
What's a vacuum gauge and how does it work. Also how is it fitted.
Click to expand...

It's a gauge which measures the vacuum in the fuel pipe between the primary filter and the engine. When the primary filter starts to get blocked, the engine has to "suck" harder to get fuel, and the vacuum in the fuel line increases. The gauge is simply connected with a T-joint and can be remotely mounted - mine's on the switch panel, as the pic below shows. There are lots of vacuum gauges available; mine's a Racor gauge, which you can buy from ASAP Supplies.

instruments.jpg
 
We changed our inline filters to parallel simply because if one filter blocks you can switch to the other, it is standard on motorboats for the obvious reason. Our filters were finer than the engine filter.
 
oldbilbo said:
What's to like?

I can see the merits of a pair in parallel, with the freedom to switch from one to the other should blockage begin to affect supply to engine. However, is there any merit in having them arranged in series, but with different grades of filtration?

Or should I simply have an inline 10 micron fine fuel filter downstream of the 40 micron jobs....
Click to expand...

I've a settling tank/water-trap, then a 40μ Racor filter and finally the standard 10μ filter on the engine.
Only fitted after I'd had the tank out and steam-cleaned following several line blocks (usually in the lift pipe). In nearly 2000 hrs have never had to change the Racor filter, though the 10μ filter is changed every 350 hrs.
 
eidiohir said:
I was looking on-line and I came across this on E bay http://www.ebay.co.uk/itm/50MM-GLYC...857?pt=LH_DefaultDomain_3&hash=item43be021b01 Are they the right sort of gauge and if so are they any good. They are a right bit cheaper than a Racor but then maybe its a case of you get what you pay for?
Click to expand...

Full scale deflection on the Racor gauge is 100kPa (1 bar), and the increase in vacuum exhibited by filters starting to get blocked is only around 10kPa (0.1 bar). So the gauge you linked to can show -1 bar to +2 bar, so the deflection of the needle due to a filter starting to get blocked will be minimal, and you might not notice it. These gauges are also affected by atmospheric pressure and temperature, so I'd be tempted to look for one which is more sensitive.
 
pvb said:
Full scale deflection on the Racor gauge is 100kPa (1 bar), and the increase in vacuum exhibited by filters starting to get blocked is only around 10kPa (0.1 bar). So the gauge you linked to can show -1 bar to +2 bar, so the deflection of the needle due to a filter starting to get blocked will be minimal, and you might not notice it. These gauges are also affected by atmospheric pressure and temperature, so I'd be tempted to look for one which is more sensitive.
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Would this be the right one? http://www.ebay.co.uk/itm/Racor-160...at_Parts_Accessories_Gear&hash=item5d3f0d4308 If not can you kindly point me in the right direction I do want to use this type of kit, it could be a live saver
 
eidiohir said:
Would this be the right one? http://www.ebay.co.uk/itm/Racor-160...at_Parts_Accessories_Gear&hash=item5d3f0d4308 If not can you kindly point me in the right direction I do want to use this type of kit, it could be a live saver
Click to expand...

Yes, that's the one, but with shipping from the States, import duty and VAT, it will cost a fortune! I said in post #5 that you can get it from ASAP Supplies. http://www.asap-supplies.com/search/vacuum/vacuum-gauge-for-racor-turbine-filters-1606b

If you want to risk paying the duty etc, by buying a Racor gauge from the States, there are cheaper offers on eBay, eg http://www.ebay.co.uk/itm/Racor-160...-monitor-your-filter-/300470910596#vi-content

Or, there are cheapo gauges on eBay which would probably do the job, eg http://www.ebay.co.uk/itm/Vacuum-Ga...892?pt=LH_DefaultDomain_3&hash=item1e79d652b4
 
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pvb said:
Yes, that's the one, but with shipping from the States, import duty and VAT, it will cost a fortune! I said in post #5 that you can get it from ASAP Supplies. http://www.asap-supplies.com/search/vacuum/vacuum-gauge-for-racor-turbine-filters-1606b

If you want to risk paying the duty etc, by buying from the States, there are cheaper offers on eBay, eg http://www.ebay.co.uk/itm/Racor-160...-monitor-your-filter-/300470910596#vi-content
Click to expand...
Thank you I'm a slow learner. I intend to add this during the winter I think its great that you can monitor the state of the filters from the bridgedeck. Thanks again!
 
I think the point of series filters is,
However dirty things are when you change the first filter, the second is there to protect the engine.

One variation is to have the second filter 'upside down' so that it traps any air introduced in a filter change.
I've heard it said that the likelihood is, if you tank is so full of carp that the first parallel filter blocks, the second one will block PDQ too.

I'm no longer sure what the best system is.
If I were starting from scratch I would have a 'day' tank of some sort, I think. Even if it was more like a '2 hour tank' of cleaned diesel.
 
>I've heard it said that the likelihood is, if you tank is so full of carp that the first parallel filter blocks, the second one will block PDQ too.


Initially no, there is an on/off switch for each filter so the off one is not passing fuel through so can't block at the same time as the other filter. If there is a lot of crud then it will block at some time by which you will time you will have changed the first blocked filter, and so on. We carried 12 filters at all times when long distance cruising just in case that happened.
 
lw395 said:
I'm no longer sure what the best system is.
If I were starting from scratch I would have a 'day' tank of some sort, I think. Even if it was more like a '2 hour tank' of cleaned diesel.
Click to expand...

If I was starting from scratch, my tanks would have drainable sumps, into which any dirt and water would automatically drain.
Wait a minute - that's what I have.:)
 
NormanS said:
If I was starting from scratch, my tanks would have drainable sumps, into which any dirt and water would automatically drain.
Wait a minute - that's what I have.:)
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If I were starting from scratch, I'd have a built-in fuel polishing system. And possibly a small header tank high up, exclusively for bleeding by gravity.
.
 
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