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Old 07-08-2016, 12:48   #1
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Please Challenge my Tank Design

I have a 1986 HR42 with 400 ldiesel tank in the keel area. I am considering following set up. As You can seeClick image for larger version

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ID:	129113 I have another additional tank under the seats *100l(, which do not have any pipes to the engine. I am considering pumping fuel from keel tank trough a filter to daytank. For this set up I need to create pipe connection in the day tank and it will take quite a lot of work. However, the advantages are> 1. I can not clean keel tank since there is no access . By pumping trough a polishing filter I could remove the worst of it. 2. It is easy to check day tank since it is under the seats and I can look into it. Double Racors between day tank and the engine will be basically second filtration. On top of everything I will remove Selonoid valves since there is a free fall from the day tank and the fuel can not flow back. Let me hear your thoughts_


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Old 07-08-2016, 13:18   #2
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Re: Please Challenge my Tank Design

I would have a pump at the bottom of the keel tank.
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Old 07-08-2016, 13:21   #3
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Re: Please Challenge my Tank Design

Can you run the refueling line through the polisher/filter as well? Have a series of valves that allows to route the fuel to either tank from the same polisher.

Keep the keel tank clean on the way in, and with sustained use - ought to clean it up a bit. Also gives you added flexibility of being able to refill the day tank without having to go through the keel tank should something happen (say your keel tank fails - you'd want to be able to seal/bypass it.)
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Old 07-08-2016, 13:43   #4
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Re: Please Challenge my Tank Design

Not positive from your drawing, but make sure you have an overflow from day tank back to keel tank. So you can not over fill if you leave transfer pump on. You can also then leave transfer pump from keel tank running thus polishing fuel on a continuous basis when and if required. With the day tank overflowing into the keel tank you then could leave current fill line in place. As previously mentioned giving you the best of both worlds.

If you are concerned with dirty fuel coming in as well as dirt already in the keel tank add a hi-flow in line filter in your fill line.
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Old 07-08-2016, 17:51   #5
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Re: Please Challenge my Tank Design

Racor filters, fuel biocide and conditioner will clean and keep your fuel clean. Even better if you buy clean fuel to start.
My current boat, 1942 Wheeler, has the original tanks and sat for 6 years before I bought it with no fuel maintenance. Using the existing Racors and quality fuel conditioners, I easily cleaned the existing fuel and tanks and have had no fuel/dirt problems. I now run a 2 micron primary that will go 500+ hours (or about 5000 gallons).
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Old 07-08-2016, 18:54   #6
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Re: Please Challenge my Tank Design

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Originally Posted by PaulinOz View Post
Not positive from your drawing, but make sure you have an overflow from day tank back to keel tank. So you can not over fill if you leave transfer pump on. You can also then leave transfer pump from keel tank running thus polishing fuel on a continuous basis when and if required. With the day tank overflowing into the keel tank you then could leave current fill line in place. As previously mentioned giving you the best of both worlds.

If you are concerned with dirty fuel coming in as well as dirt already in the keel tank add a hi-flow in line filter in your fill line.
+1. Exactly my setup, except I had not considered the filter on the fill line. I like that idea.
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Old 07-08-2016, 22:55   #7
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Re: Please Challenge my Tank Design

THX to all of you...I m going for it...


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Old 08-08-2016, 03:22   #8
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Re: Please Challenge my Tank Design

I did similar when fitting a new engine but with the addition of a couple of y split valves, the sketch actually looks a bit more complicated than reality. Now it's possible to pump in or out of a can through a filter and more, well worth the effort imho.

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Old 08-08-2016, 09:13   #9
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Re: Please Challenge my Tank Design

Quote:
Originally Posted by amarf View Post
I have a 1986 HR42 with 400 ldiesel tank in the keel area. I am considering following set up. As You can seeAttachment 129113 I have another additional tank under the seats *100l(, which do not have any pipes to the engine. I am considering pumping fuel from keel tank trough a filter to daytank. For this set up I need to create pipe connection in the day tank and it will take quite a lot of work. However, the advantages are> 1. I can not clean keel tank since there is no access . By pumping trough a polishing filter I could remove the worst of it. 2. It is easy to check day tank since it is under the seats and I can look into it. Double Racors between day tank and the engine will be basically second filtration. On top of everything I will remove Selonoid valves since there is a free fall from the day tank and the fuel can not flow back. Let me hear your thoughts_


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I did something similar on a boat I had in the past. [Some of what I mention here has been covered by other contributors as well.]

Basically, I pumped [through filters] from the main fuel tank into the top of the day tank [so the fuel couldn't gravity flow back to the main tank...]

The day tank air vent Teed into the main tan air vent, and therefore also acted as the overflow for the day tank.

With a few fuel selector valves, you can plumb your twin Racors so they are in the circuit no matter which direction you are pumping fuel.

It sounds like a nice improvement for your boat. It was on mine especially because the day tank also gravity fed the diesel drip heater- eliminating the tic-tic-tic sounds from the heater fuel pump...

Cheers! Bill
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Old 08-08-2016, 16:22   #10
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Re: Please Challenge my Tank Design

Placement of tank fitting can screw the best plan. Day tank mounted on cabin roof filled and drained back to tank. Drain was on the bottom so stove only worked when engines were on On top of that, the return lines to 4 separate tanks were crossed at the manifold so I put two tank loads into one tank while delivering new vessel to Alaska My own vessel enjoyed a day tank setup in which the tank vents went though the day tank so localizing condensation to the drain of the day tank. (Tanks also big vented thru opened deck fills when fueling.
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Old 08-08-2016, 19:04   #11
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Re: Please Challenge my Tank Design

I went through this exercise a number of years ago and decided that a separator system to circulate the main tank down in the keel was a better option. I have a 12V gear and a Finsbury bucket pump in parallel with a check valved bypass around the Finsbury to allow unrestricted flow when using the gear pump. The separator is a DIY job made out of a large glass spaghetti jar inside this is a bag filter made from heavy denim (It's what I had handy at the time) A 1/2" stand pipe goes all the way to the bottom of the tank with a hose between it and the pumps suction. I also have a hose on the output as I use the same system to pump out my engine for oil changes.


If I just want to check for water I can hand pump the bottom of the tank and see any water returned in the bottom of the glass for a gunk cleanout I run the gear pump on 6 volts and prime it using the Finsbury.


If I just want
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Old 08-08-2016, 19:34   #12
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Re: Please Challenge my Tank Design

Thats a large day tank putting a lot of weight up high.

We have a 6L (1.5 gallon) day tank which gravity feeds our espar heater, generator and main engine. 1 hour of engine operation is sufficient for a day tank. The generator will run for many hours and the espar heater could run for about 12 hours with no electric fuel pump ticking.

It is fitted with high, med and low sightglasses and level sensors. These light up green, yellow or a red led at the helm giving plenty or warning of any fuel delivery issues. It is also fitted with a flow sensor that can be bypassed when not calibrating our fuel consumption curves.

We have a 3 stage filtration system. Racor 500s as primary 30 micron, a Racor P series fuel pump, heater and 10 micron filter as secondary which can be bypassed to a backup walbro pump, and the on engine / generator 2 micron filter as tertiary.

We can polish from any tank to any other tank.

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Old 08-08-2016, 20:37   #13
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Re: Please Challenge my Tank Design

Do I understand correctly that these gravity feed tanks need to have a penetration and pluming fittings mounted on the bottom of the tank?

Yes it sounds very common but IMHO it's just a bad idea. I don't think I will ever want that kind of setup in my boat.

This is because I did have such a setup in an aluminum "wing" tank. Corrosion in the fitting at bottom of tank resulted in slow seeping of diesel into bilge which was not detected until it became quite obvious from the smell. Then I had to spend some hard earned money having a pro come out and clean the bilge, to say nothing of having to remove the tank and have that bottom penetration permanently welded shut.

Fortunately, there was no other damage but I did lose some sleep thinking about what might have happened.

Now I have only a top mounted fuel line in that tank, which can be siphoned (after starting the flow with a pump) into the main tank under the cabin sole. Any leakage in that line will only result in failure of the fuel transfer, not spillage. I do have to be careful to only do this when I know I have lots of empty space in the main tank so it could take all the wing tank load if I forget to switch off the valves.
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Old 09-08-2016, 06:26   #14
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Please Challenge my Tank Design

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Originally Posted by leftbrainstuff View Post

1 hour of engine operation is sufficient for a day tank.

I really disagree with this.

Having pounded for four hours through horrendous conditions in Backstairs Passage near Kangaroo Island under engine, I can say we would absolutely have been stuffed if we'd had to top up the day tank during that time. We had five crew on board at the time and it was all we could do to just to hang on. Farting about with fuel systems below decks or above would have been impossible.

We have about twelve to fifteen hours under normal engine conditions in the day tank, and that feels barely adequate. As it was, under the heavy engine load in the passage, we were burning fuel at nearly double the normal rate too. Running near 1600 rpm instead of 1000 rpm. With a one hour tank we'd have had to top up every half hour.

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Old 09-08-2016, 06:36   #15
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Re: Please Challenge my Tank Design

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Do I understand correctly that these gravity feed tanks need to have a penetration and pluming fittings mounted on the bottom of the tank?

Yes it sounds very common but IMHO it's just a bad idea. I don't think I will ever want that kind of setup in my boat.
.

No, the usual top mounted pickup tube is all that is required. Some suggest using the breather hose for the overflow to the main tank. I tried that, it drove me nuts. Any fuel in the breather hose and the breather would either belch diesel into the cockpit when refuelling or at the very least fail to breath and cause blow back at the filler. I just added yet another outlet to the top of the tank and sent it to the main tank down below.


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