Simple Fuel Poliishing

[Roger Long]

I've seen a lot of fuel polishing systems proposed here and elsewhere. I've gotten by without one on our current trawler but, when and if I get around to installing one, it will be like this one which simplifies retrofit issues and a lot of extra piping.

https://www.cruisingonstrider.us/images/Fuel_Polishing.pdf

 

[rgano]

I would suggest also allowing for polishing back to the main tank. I used to select one of my four tanks every month and run the polisher for 24 hours. That way all tanks were pretty much ready to go as day/hour tank. In practice, while cruising, I ran the two tanks per side as independent systems from each other keeping supply for each engine separtated. At the end of each day, I polished the day's usage of fuel from the two tanks I used as "storage" in the the slightly smaller tanks feeling the engines directly.

 

[SteveK]

Looks like the day tank has an overflow back to the main tank once filled

 

[rgano]

Looks like the day tank has an overflow back to the main tank once filled

I see that. It's good as is for a single tank. Wonder about multiple tanks.

 

[caltexflanc]

Thanks Roger, that's interesting. I'm confused by this:

"The pump is wired into the engine system to start whenever the electrical
system for the gauges and starting is energized. You can also install a switch to run the pump with the engine off in case you need to clean up a bad batch of fuel."

It sounds to me like you have both the polishing system and the engine competing for the fuel when under way? I'm not seeing the point here somehow, can you explain a bit more?

Thanks

 

[rgano]

I guess I assumed the intended use is to polish fuel to the day tank when not underway and replenish it daily.

 

[SteveK]

The plumbing needs the pump running to fill the hour tank in order to supply the engine. The polishing does not compete with the engine. For twin tanks, I suppose you need two of these. Interesting concept as it eliminates secondary plumbing and switching valves.

 

[caltexflanc]

The plumbing needs the pump running to fill the hour tank in order to supply the engine. The polishing does not compete with the engine. For twin tanks, I suppose you need two of these. Interesting concept as it eliminates secondary plumbing and switching valves.

Then what's the point of the line between the main and the hour? It somehow feeds overflow of the hour to the main?

I have to admit, not only am I admittedly dense in trying to understand this, I don't get the whole complication introduced by the "Hour" tank to begin with. Why not just use multi stage filtration from main to engine to begin with, or cycle fuel out of and back into the main with no hour tank at all?

 

[SteveK]

George. The link explains a bit more. The hour tank named thus to supply the engine for an hour is constantly replenished as the 'P' (pump) is turned on when the engine is running. The line from the hour tank top to main tank top is an overflow return when hour tank is full.
At least how I read it.

 

[Roger Long]

At least how I read it.

You got it.

 

[Roger Long]

I see that. It's good as is for a single tank. Wonder about multiple tanks.

Yes, you would have to be careful with multiple tanks that you were always returning to the same tank.



Twin engines could both draw from the same Hour Tank, along with generators and diesel heaters, as the tank provides a buffer so they are not sucking against each other.


I'm really glad to have a boat with just one fuel tank

 

[SoWhat]

If you have primary and secondary filters this diagram would simply add a third.
Typically polishing is only required when a tank is contaminated with water or little creatures. The main goal is too polish the main tank. (P)

Redundancy is desirable so once the main tank is covered I would add valving direct to the secondary and bypass fuel pump. Fuel pumps do fail.

 

[obthomas]

Yes, you would have to be careful with multiple tanks that you were always returning to the same tank.

Twin engines could both draw from the same Hour Tank, along with generators and diesel heaters, as the tank provides a buffer so they are not sucking against each other.

I'm really glad to have a boat with just one fuel tank

Thought I would show you all my system:

 

[SteveK]

If you have primary and secondary filters this diagram would simply add a third.
Typically polishing is only required when a tank is contaminated with water or little creatures. The main goal is too polish the main tank. (P)

Redundancy is desirable so once the main tank is covered I would add valving direct to the secondary and bypass fuel pump. Fuel pumps do fail.

I was thinking the same for a pump failure, bypass valve to let engine draw from tank.

IF you already have a primary and secondary it is just a matter of re purposing the primary into this system. Our engines were originally designed to operate on what we now call secondary.

 

[SteveK]

Thought I would show you all my system:

Are those opposing triangles shutoff valves, one is marked NC (not closed?). Check valves for one way flow.
Why do you have an intake from bottom and from top?
Also interesting but more complicated.

 

[Lostsailor13]

I had 250 gallons of old diesel from 20 years ago when I bought my boat the tanks were so bad after 5 hrs of steaming in heavy seas my racor 500 was smoked,I Installed a gulfcoast F1 fuel filter and it totally worked so good after about 30 hrs of running hard and changing filter 2 times I believe I have cycled through all of the remaining 200 gallons enough and it totally cleaned up tbe tanks and as a result my deisel is 100% cleaner

 

[Xlantic]

I like it. It is a combination of the day-tank concept plus polishing. While I have my doubts on how effective polishing is I believe the day-tank are good insurance against many fuel issues.

I had a similar system in my previous boat but this design is simpler and cleaner. And, unlike in mine, here the filling of the hour automatic as the pump goes on when the engine runs.

I would suggest you include a valved sump in the hour tank so you can periodically check it for water.

 

[Xlantic]

Here is one of my day-tanks, with sump valve.

 

[FF]

Fuel "polishing" can make the batch of fuel in the tank cleaner ,
BUT if the tank has crud it does next to nothing for the tank.

 

[mvweebles]

So if the transfer pump fails underway, you run out of fuel. You can then switch the bypass valves to go direct to the main tank, bleed the system, and you're on your way again, right? If so, by reducing risk of bad fuel, risk of no fuel is elevated. Interesting tradeoff.

Polishing systems get reasonably manageable if you use decent 3-way valves and remove the requirement they need to be used underway.

https://www.groco.net/ts-350-t

Peter

 

[Xlantic]

Fuel "polishing" can make the batch of fuel in the tank cleaner ,
BUT if the tank has crud it does next to nothing for the tank.

That has been my experience. The crud just lurks in the bottom or sides of the tank and only breaks loose and goes out into the fuel lines when shaken, say in a seaway, which is one of the worst possible times.

That's why I find a day-tank to be a better safeguard.

 

[Roger Long]

Fuel "polishing" can make the batch of fuel in the tank cleaner , BUT if the tank has crud it does next to nothing for the tank.

That's true for one time wallet polishing where a contractor just filters the fuel without using a wand to spray wash the walls with it or the tank is not hand cleaned. However, if a polishing system is run long term, the tanks will get cleaner. I watched this progress on my sailboat which ran more like a trawler on my ICW trips. Motion cleaned the tank sides and the crud got sucked up into the stronger flow of the polishing system instead of accumulating in the bottom of the tank.

 

[obthomas]

Are those opposing triangles shutoff valves, one is marked NC (not closed?). Check valves for one way flow.
Why do you have an intake from bottom and from top?
Also interesting but more complicated.

NC is common diagram designation for "Normally Closed". My tanks supply engines from a dip tube about 2 inches from the bottom of the tank. The other connection is the tank drain. Switching from the dip tube to the drain is best for polishing.

 

[Choices]

Mine is similar but even simpler.

I upsized to a racor 500 for genset to reduce spares.
Then I used mini qtr turn valve's and use genset filter as polishing filter. So I can draw from either tank, and return to either tank, or feed main engine or genset.

Very flexible system.

First time I polished it took out a filter, since than never been a problem.

Mine is powered off engine room light circuit so I don't forget it is on.

 

[SteveK]

One day soon when I get me a

I must replumb my primary Racors, install the transfer pump, switching valves as needed and set this up.

 

[caltexflanc]

I still don't get the need for an "hour" tank. "Day" tank, well maybe.

Part of my naivete is not having boated in places where awful fuel was the norm.
Starting with clean tanks and using sequential progressive filtration seems more logical to me than introducing complications and potential additional points of failure.

I'm not being critical, because I can't criticize something I don't understand. I think we should just leave it at that for now. Do what makes you feel more confident, that's what counts.

 

[catalinajack]

It is also better for normal fuel supply irrespective of whether there is a polishing system in place. If your tanks are clean they will stay clean as all fuel will go through your filters, water, crud, everything thus eliminating the need to polish fuel. If you are paranoid - I am not - about that rare bad load of fuel, then use a dual Racor in the event you forget to pay attention to your vacuum gauage and you plug a filter underway. Or, use a Toney Athens type sequential filtering head which employs a 20-micron "mud" filter that feeds a 10-micron final filter (not including your on-engine filters). That is what I use. I can change a filter in less than five minutes with a minimum, if any, spillage. Turn fuel supply valve off, spin old filter off with catch vessel underneath, spin on new filter, open supply valve, open bleeder till air stops, close bleeder, start engine. My fuel is supplied from the bottom of my tanks, no dip tubes.

NC is common diagram designation for "Normally Closed". My tanks supply engines from a dip tube about 2 inches from the bottom of the tank. The other connection is the tank drain. Switching from the dip tube to the drain is best for polishing.

 

[FF]

"Part of my naivete is not having boated in places where awful fuel was the norm."

We all hope for clean fuel , but "stuff" happens.

I think the most common cause of water in the fuel, that grows bugs, is a badly sealed deck fill.


Having a fuel box pro cleaned has limitations as a large capacity usually means there will be baffles to stop sloshing loads , that cant be cleaned behind.

 

[83GB]

You might consider some additional plumbing so that your polishing pump can act as a lift pump should the engine lift pump fail... just a thought

 

[Tim]

Pump location

I would put the pump ahead of the filter. They push better than they pull.