Fuel Polishing System

[lorenzo b]

Don't let the CG catch you with any of that white flake, dude.

[s/v Jedi]

Hi guys,

I'm a bit late to this thread, but I designed a fuel polishing system aboard Jedi 5 years ago. It's based on the documentation from Nordhavn. You find my description here: A new fuel system for Jedi (English) - s/v Jedi

this is the diagram:

ciao!
Nick.

[Southern Drawl]

The fuel polishing can be accomplished by pumping fuel from the tank bottom with a vacuum device such as a Topsider pump or similar

[DeepFrz]

The fuel polishing can be accomplished by pumping fuel from the tank bottom with a vacuum device such as a Topsider pump or similar

Good luck. Let us know how you make out.

[emarine01]

I wish I had more time to address some of the posts @ length, The water issue in diesel tanks is pretty straight forward, On most diesel engines the return fuel removes heat from the fuel injection system, This heat will raise the fuel tank temp well above ambient air temp.... on some engines diesel fuel is run through the cylinder head as well and can raise fuel tank temps over 140F, After a long run the fuel in the tank expands.... When you dock the fuel will begin to cool drawing in air from the tank vent, Depending where you are on the planet... the relative humidity @ sea level can be very high introducing water vapor into the tank, over time this water collects in the bottom of the tank, This is the start of the tank fouling process.... Of course bad tank fill o rings and improper vent installations add to fuel tank water, Then there is the good ole mate who put the water hose in the fuel fill issue, Last and the less likely way is the last fuel vendor you purchased your fuel from... who usually gets the first blame... I know its happened... but most fuel vendors have had to upgrade their tanks and pumping systems to include water meters to insure water is not sold with fuel, One simple question to ask when you purchase your diesel fuel is, What type of filtration system is installed on the diesel pump if any, Good luck Guys

[emarine01]

Diesel fuel can be very TOXIC..... so every precaution should taken to protect skin and inhaling fumes.... Again good luck, Craig

[Astrid]

On most diesel engines the return fuel removes heat from the fuel injection system, This heat will raise the fuel tank temp well above ambient air temp.... on some engines diesel fuel is run through the cylinder head as well and can raise fuel tank temps over 140F, After a long run the fuel in the tank expands.... When you dock the fuel will begin to cool drawing in air from the tank vent, Depending where you are on the planet... the relative humidity @ sea level can be very high introducing water vapor into the tank, over time this water collects in the bottom of the tank,

On at least some older marine diesel fuel systems, unused overflow fuel from the injectors passed through a condensor-like cooling jacket before going to the tank.

[saben]

Originally Posted by Pete7

Nope disagree with that . A change in atmospheric pressure will move air in and out of an empty fuel tank as will a change in temperature during the day and night. The cooling effect of a steel tank containing moist air means water vapour will build up slowly but surely.

Little air will be drawn into our tank during use because we only use a couple of tank fulls a year on a yacht though clearly anyone using a motorboat will use more.

One of the reasons I changed to a plastic tank on a previous boat and I will swop the current steel tank out in time.

Your point on seals is very true and I suspect often overlooked. I took a while to work out why the previous owner had a small jar of petroleum jelly in the gas locker nearby the fuel filler.


Pete

I agree with this observation. Tank breathing caused by atmospheric pressure changes. Very seldom is the atmospheric pressure constant, its always breathing just like humans drawing in moisture every time and condensing on the tank walls if they are colder. More of a problem in colder climates and especially with integral steel fuel tanks in contact with cold northern water like the Puget Sound where my boat Saben was for many years. For that reason I tried to keep the tank topped off, minimizing air space volume. I had an idea but never actually tried it. Connect a small diameter vinyl hose to the tank vent outlet and routed to a canister of silica gel crystals, desiccant, to remove the moisture in the air being breathed.

[DeepFrz]

The following list answers a lot of these questions.

Fuel School: Asphaltene's and Plugged Fuel Filters

[emarine01]

Originally Posted by s/v Jedi

Hi guys,

I'm a bit late to this thread, but I designed a fuel polishing system aboard Jedi 5 years ago. It's based on the documentation from Nordhavn. You find my description here: A new fuel system for Jedi (English) - s/v Jedi

this is the diagram:

ciao!
Nick.

Nice system Nick I quick note for anyone who installs their own fuel polishing system using Racor turbine type filters..... All Racor turbine filter housings have a max of 15psi working pressure..... so when installing this type of unit after a fuel supply pump < pressure supplied to the input side of the racor> Make sure the fuel pump has a pressure regulator or relief valve set less than 15psi .... It is also a good practice to clean pump pressure relief plungers every couple of years to prevent spill or fire hazard.... It is always best to install Racor turbine filters on the suction side of the pump < before the pump> so to keep the filter housing under vacuum not pressure....Craig

[s/v Jedi]

Originally Posted by emarine01

Nice system Nick I quick note for anyone who installs their own fuel polishing system using Racor turbine type filters..... All Racor turbine filter housings have a max of 15psi working pressure..... so when installing this type of unit after a fuel supply pump < pressure supplied to the input side of the racor> Make sure the fuel pump has a pressure regulator or relief valve set less than 15psi .... It is also a good practice to clean pump pressure relief plungers every couple of years to prevent spill or fire hazard.... It is always best to install Racor turbine filters on the suction side of the pump < before the pump> so to keep the filter housing under vacuum not pressure....Craig

Thanks Craig. The system has performed 100% over the last 5 years so it's solid. I used Walbro fuel pumps that deliver 7-8 psi pressure so well under the maximum of the Racor filters. The pump that connects to the feed-manifold is the one that pressurizes the racor filters and this is done for priming the system or to boost fuel through a clogged filter element in an emergency.

One nice observation about the system: I tested pumping fuel from a jerry jug that was put in my dinghy alongside, to emulate pumping it from a drum. This works well and I discovered that when I run both pumps for this (to both the feed and return manifolds so back-feeding via the feed manifold) I still just stay under the maximum flow rate for the Racor 500 filter.

I also put an old fashioned mechanical timer switch on the transfer pump so that I can give it a spin and let it polish fuel for an hour or two and then stop by itself. I circulate within tanks until I have less than 1 full tank; I start transferring it at that point. For circulating within a tank the rule of thumb is to circulate 5x the volume of fuel currently in the tank for a full clean cycle.

ciao!
Nick.

[Marine Nut]

Has anyone here read this?

http://boatdiesel.com/Articles/Artic...ion.cfm&Y=2006

Some interesting ideas that may have some substance behind them.I certainly like to get some input from your side of the world.

Wes

[farotherside]

Hey all,

We're heading offshore in just over a month, headed south, and after reading this thread I realized I've got all the parts to build a fuel polisher except the actual filter! We'll probably be in far-off anchorages, so reliable fuel would/will be key.

I'm currently running dual filters in my engine room, a Dahl filter/separator and the Yanmar filter on the engine. I do have two day tanks though, and a Reverso OP-4 pump to transfer diesel to them - it seems to me that I could put a Y-valve on the output of the Reverso and send the fuel through a filter or two and back into the main tank.

What filter would you recommend for this task, given the OP-4's flow rate of (I think) 3 gpm?

[Florida Mike]

Drew23,

You need to check the pump motor and see if it is rated for continuous use. Other than that it should be a fine pump for what you want to do. Just my two cents, Mike.

[Dockhead]

Originally Posted by DeepFrz

Exactly! Those seals are very, very important as is making sure the cap is closed securely. A much better idea would be to have the fuel fills mounted in the side wall of the cabin. The only production boat that does this (that I know of) is Kadey-Krogan, although the newer Nordhavn may.

Many Moodys, including mine, have the fuel filler mounted high in the doghouse bulkhead, behind a door. I always thought that flush-mounted in-deck fuel fillers were madness. I'm not actually comfortable even with the fresh water filler mounted that way.