Fuel Plumbing Configuration

[Janusz]

So, I run a single engine trawler.

There are two tanks port and starboard sides and two primary Racors.

I keep all valves opened, which means fuel comes from both tanks simultaneously, goes through both Racor and returns to both tanks. The tanks are both connected with each other and fuel pick ups are from the bottoms of the tanks.

Is that a mistake?

Should I draw fuel from one tank and then switch to the other? In that case the return fuel should go to the same tank, which would mean the other tank is just dormant until I swap them, right?

How about Racor filters then? Should i run them one at the time? Also, I inherited a collection of filter inserts from PO and they are 2 microns, 10 microns and 30 microns. Which should i use?

Please educate me.

 

[dhays]

There are no “right” answers, but there are a lot of preferences based on our different environment and uses.

I have the same setup. Single engine, two tanks, double Racor primaries.

My practice is to draw from and return to one tank at a time. To be honest, I have no strong reason for doing so. I will draw from one tank until there is enough of a difference in tank levels to prompt me to switch tanks. I also will sometimes simply transfer fuel from the unused tank into the used tank as I have a fuel transfer pump and crossover line.

I don’t see anything from with drawing from both tanks and returning to both tanks. Likely, you will find that you won’t get an equal draw from the tanks. When that happens, you can equalize the levels by either drawing from one tank for a bit, or only returning fuel to one tank for a bit.

I do think there is a very good reason to only use one of your Racor primaries at a time. On the off chance that you encounter bad fuel or some other problem, if you are running through both filters you are clogging up both filters. If you only run through one filter, you have the other fresh filter immediately available by simply turning your selector. You then can change the clogged filter, even while the engine is running.

I have a vacuum gauge on my filters but have never seen high vacuum on the my filters as I’ve never had fuel problems. I change out the filter element that has been used once a year and then turn the selector to the filter element that has been unused. Ideally, the filter elements should both be replaced yearly as the filter elements Aqua-block do age out when immersed in diesel fuel according to some information that I’ve read from Parker. Even so, I don’t bother. I’m happy to use a filter that has simply sat in diesel fuel for a year.

The final question is what filter element should you be using. Lots of opinions my smart folks on this. I’m not smart. I have a Cummins QSB common rail engine. The secondary filter is a 2 micron filter and I use the Cummins Fleetguard filters. I typically replace the secondary every 2 years. Cummins says to replace it every 250 hrs or 6 months, whichever comes first.

Cummins also calls for 10 micron primary filters. So that is what I use. However, this last time I happened to have 2040N-02 Parker filter elements rather than the 2040n-10. While we often consider the -02 to be 2 micron filters, Parker says they are 98% effective at filtering down to 4 microns.

Anyway, there are plenty of experienced folks who will use the -02 as primary filters feeling that as long as there isn’t too much vacuum created by the increased resistance to fuel flow, then the extra filtration can’t hurt. Next year, I’ll go back to using the 10 micron filters as that is what I ordered to replace my spares.

 

[mike66]

My set up is just like yours, except my return for both gen and main go to the starboard tank. I run both tanks at once through one racor, with the ability to switch to the other if needed. Both tanks are connected at the bottom. Often when refueling 100 gallons I just fill whichever side is closest to the dock, and the tanks self level. The Lehman sips fuel, so I don't think much about the filtration size. Switching tanks periodically is more complication than I need. Bad enough when it came to battery switches before I set up ACR's.
I only boat in New England, so bad fuel is seldom an issue.

 

[rwidman]

I suggest that you continue to do what you are doing. By drawing fuel from all the tanks simultaneously, the boat keeps its balance and you don't have to bother with switching valves back and forth. That's as simple as it can be.

I see no advantage to doing it any other way.

 

[Fish53]

This depends on how the tanks are connected. If the boat gets a list will fuel flow from one tank to the other causing the list to worsen? If so it wouldn't be a good idea to keep them connected. Also by keeping the tanks connected you have no control or knowledge of how much fuel is used from each tank plus if you get bad fuel it may contaminate the other tank. I have the same two tank one engine configuration and I always draw and return to the same tank and don't have them connected. Generally I change tanks every few hours, keeps things balanced and gives me a reason to check the engineroom. I can't actually see a valid reason for tanks to be connected with anything except a transfer pump, which is a good idea for a number of reasons.
Your engine filter is probably 2 micron so the Racor would be best at 10 micron if you like changing filters on a schedule like I do.

 

[High Wire]

There is no good reason to use both RACORs at the same time for a single engine unless it's the only way to cross-tie tanks. Run one RACOR and keep the other full and bled, ready for use at any time. The extra flow will help the centrifuge action of the filter. Change the used element at some reasonable interval. I use 1 season or 500 hours whichever comes first then adjust based on what I find in the filter. The other filter goes in service for the next season, etc. If you pull out the element and it looks like you dunked it in coal tar, you should shorten the interval!
Also label the filter with a tag so you know what's in there. Micron rating, date, and engine hours.
I'm assuming you have a single Lehman so what you use in the RACOR might depend on how accessible the on-engine secondary filters are to change. The Lehman will run on 2, 10, or 30s. Check the spare elements that you have for the older ones need a spacer that is no longer available. The newer elements do not use the spacer. So if you do by chance have the spacer, use up the elements that use the spacer first.

 

[Fish53]

You can run two Racors inline as a two stage filter, say a 30 micron in the first then a 10 micron in the second, if you have gauges on your filters a setup like this can extend the life of the filter elements.

 

[Janusz]

Thank you for all the answers guys.
You've answered all my questions and my doubts are gone.

I will use my Racors one at the time, especially that they are connected parallel and not in line and my engine, although not Lehman anymore but a newish Pekins M-225, sips fuel at a low rate indeed (8-9 liters or 2 gallons an hour).

Archie, your argument about stronger centrifugal action of one filter is very elegant and convincing.

My primary filters are configured parallel and not in line so i could not use your advice, Fish 53