Terminating return fuel line with angled pipe inside the tank.

DinoKanuck

DinoKanuck

.
Feb 4, 2012
95
LM 28 Pilot House Sloop Pilothouse Campobello Island & Fredericton, NB
Hello All,

Time has come to replace the fuel lines, the fuel pick up and the fitting that takes the return line into the tank. See pics of old system and some of the new fittings to see why.

Any advice on terminating the return line with a short angled pipe inside the tank so the returned fuel gets returned a distance from the pick up?

It will be roll-your-own part so any advice is appreciated on length of pipe, angle and how far away the returned fuel should be from the pick up.

I'm using USCG rubber approved fuel line

Thanks

Dino

Dinoimage.jpegimage.jpegimage.jpegimage.jpeg image.jpegimage.jpgimage.jpg image.jpg
 
DinoKanuck

DinoKanuck

.
Feb 4, 2012
95
LM 28 Pilot House Sloop Pilothouse Campobello Island & Fredericton, NB
Thanks but question was about the return.

That fuel matt goes on the pickup and looks like a problem waiting to happen.
 
capta

capta

.
Jun 4, 2009
5,072
Pearson 530 Admiralty Bay, Bequia SVG
I can't think of any reason to do this. The return line empties into the top of the tank and the pick up is somewhere near the bottom of the tank. How much farther apart do you think a 90 degree bend will put them?
 
  • Like
Likes: woodster
K

kerryedwards

.
Mar 27, 2016
52
Corsair F-24 denver
I don't see the point either. The returning fuel is filtered fuel so even if it were to go directly back to the engine it's not a problem.
 
DinoKanuck

DinoKanuck

.
Feb 4, 2012
95
LM 28 Pilot House Sloop Pilothouse Campobello Island & Fredericton, NB
The idea is valid.

Avoid air when the fuel level gets close to the pick up hole. Induce a bit of fuel circulation so your change of getting even a minor fuel polishing effect increases.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
24,539
CAL 35 Cruiser #21 moored EVERETT WA
First. the return fuel in a diesel system is low pressure/low volume. While the fuel is "polished" because it has been run through 2 filters it is a negligible impact in the terms of "polishing your fuel".

Fuel returning to the tank often is returned at a marginal distance (within 12 to 14 inches on the top of the tank) from the intake pipe which is separated by depth being near the bottom of the tank. This means shorter fuel pipe runs to the engine. This minimizes the amount of vacuum needed to draw fuel into the lines. Again it is not returned under pressure, it is returned at the top of the tank, so returned fuel has little impact at creating measurable bubbles that could create an intake fuel/air problem. If air is going to get into your intake line it is because you are low on fuel and where the return line is cannot significantly increase the fuel volume to prevent air entering the fuel lines. You need to refuel before you run empty.

It feels like you are trying to over think this issue.
 
capta

capta

.
Jun 4, 2009
5,072
Pearson 530 Admiralty Bay, Bequia SVG
If one
jssailem said:
First. the return fuel in a diesel system is low pressure/low volume. While the fuel is "polished" because it has been run through 2 filters it is a negligible impact in the terms of "polishing your fuel".

Fuel returning to the tank often is returned at a marginal distance (within 12 to 14 inches on the top of the tank) from the intake pipe which is separated by depth being near the bottom of the tank. This means shorter fuel pipe runs to the engine. This minimizes the amount of vacuum needed to draw fuel into the lines. Again it is not returned under pressure, it is returned at the top of the tank, so returned fuel has little impact at creating measurable bubbles that could create an intake fuel/air problem. If air is going to get into your intake line it is because you are low on fuel and where the return line is cannot significantly increase the fuel volume to prevent air entering the fuel lines. You need to refuel before you run empty. It feels like you are trying to over think this issue.
Click to expand
If one is so low on fuel that one is worried about the bubbles the return line is making, then one would be much better served getting their sails up because that engine's usefulness is going to end PDQ.
 
centerline

centerline

.
Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
jssailem said:
First. the return fuel in a diesel system is low pressure/low volume. While the fuel is "polished" because it has been run through 2 filters it is a negligible impact in the terms of "polishing your fuel".

Fuel returning to the tank often is returned at a marginal distance (within 12 to 14 inches on the top of the tank) from the intake pipe which is separated by depth being near the bottom of the tank. This means shorter fuel pipe runs to the engine. This minimizes the amount of vacuum needed to draw fuel into the lines. Again it is not returned under pressure, it is returned at the top of the tank, so returned fuel has little impact at creating measurable bubbles that could create an intake fuel/air problem. If air is going to get into your intake line it is because you are low on fuel and where the return line is cannot significantly increase the fuel volume to prevent air entering the fuel lines. You need to refuel before you run empty.

It feels like you are trying to over think this issue.
Click to expand
I agree....
if the system is operating properly with a good lift pump, there will be enough constant flow thru the lines and back to the tank, that IF the fuel were to somehow become aerated enough for the fuel pick up tube to suck a few bubbles, it would filter it out and send it back down the return to the tank, and only keep solid fuel going to the engine.... providing there is enough fuel in the tank to keep the pick up tube submerged in it.
 
DinoKanuck

DinoKanuck

.
Feb 4, 2012
95
LM 28 Pilot House Sloop Pilothouse Campobello Island & Fredericton, NB
As minor of a fuel circulation effect and polishing action that having the returned fuel directed away from the pick up areas will have, it is worth doing.

As you can see from the photos, the system is in parts right now. We are talking pennies for 3 to 6 inches of pipe and if a new pick up pipe is being grazed into the system why would you not braze in that bent return pipe?

Dino
 
woodster

woodster

.
Sep 15, 2009
6,244
S2 9.2a Fairhope Al
did you ever think maybe with a pipe sticking down in the fuel with a full tank you could possibly create a siphon and drain fuel back out of the tank ....then what ....
 
Maine Sail

Maine Sail

.
Feb 6, 1998
11,759
Canadian Sailcraft 36T Casco Bay, ME
The reason for a return dip tube is for high turnover applications to prevent foaming. With a standard lift pump this is not necessary. My main concern is mixing copper or copper alloys with what appears to be an aluminum tank..
 
Ron20324

Ron20324

.
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
I have no idea of the volume or force in the return line, but I'd think directing it to the lowest part uf the tank to stir the fuel- and whateverelse- might be a good idea. IF you start with a relatively clean tank.
 
centerline

centerline

.
Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
Ron20324 said:
I have no idea of the volume or force in the return line, but I'd think directing it to the lowest part uf the tank to stir the fuel- and whateverelse- might be a good idea. IF you start with a relatively clean tank.
Click to expand
its my opinion that the wave action will stir the fuel much more violently than any low volume drip tube could ever do....
 
DinoKanuck

DinoKanuck

.
Feb 4, 2012
95
LM 28 Pilot House Sloop Pilothouse Campobello Island & Fredericton, NB
Deal done... Brazed in copper pick up tube that ends 1 inch above bottom of tank and brazed in 3 inch return pipe angled away from pick up.

Tank is fibreglass so no concern on mixing my metals.

Dino

image.jpeg
 

Attachments

You must log in or register to reply here.

Top Bottom