Fuel polishing system on Nordic Tugs

[Fletcher500]

I have heard of people running their dual racers in parallel, both on, for some of the noted reasons.

I will defer to others regarding your cross over question.

The builder of our current boat doesn't like cross overs, so we don't have one. I have to periodically adjust the trim of the boat by changing the tank supply. Easy enough to do.

 

[RCook]

Thank you. Your response below begs another question. (Note: Is there a limit to dumb questions on this forum?). I came from twin diesels and twin tanks; each tank fed an engine. The crossover was a simple pipe with shutoffs at each tank. In 14 years I never opened them. Simple!

Reading below, it sounds like port tank feeds the main. Got it. The starboard tank feeds the gen and heater, and then the return fuel is fed over to the port tank. That sounds odd. It seems like moving fuel fed from the starboard tank over to port tank tank introduces a risk of overflowing the port tank, I must be missing something. Can someone add some words to help me understand this?

Also how do the tanks get balanced out?

Thanks,
Pete

On my 37, the main engine supply and its return are connected to the port tank. Genset supply and return, and diesel heater supply, are connected to the stbd tank. I keep the crossover valves open, so the fuel levels even out.

Re other posts:

I would not run fuel through both Racors at the same time - it would defeat the ability to switch quickly when a filter begins to clog.

Some NT32's were equipped with Volvos - maybe 2007-2009.

 

[mcarthur]

The builder of our current boat doesn't like cross overs, so we don't have one. I have to periodically adjust the trim of the boat by changing the tank supply. Easy enough to do.

Is there any reason not to have crossover capability? I can see it certainly adds some complexity, and therefore during confusion can possibly induce errors in opening the wrong valves or keeping some closed, but the good reasons appear to outweigh those...

 

[markpierce]

My polishing system has been disengaged (didn't seem to be useful since local fuel supplies are clean) but is still capable of transferring fuel among the boat's four fuel tanks, keeping the boat level.

 

[sunchaser]

Is there any reason not to have crossover capability? I can see it certainly adds some complexity, and therefore during confusion can possibly induce errors in opening the wrong valves or keeping some closed, but the good reasons appear to outweigh those...

Our vessel has a crossover line between between the two main tanks. The valves have never been opened since the vessel was new. A very nice fuel draw/return manifold for the 3 engines and between the 4 tanks is quite intuitive. No logical reason to use the crossover other than to add a confusion question.

Most vessels with multiple tanks have fuel transfer pumps, thus no crossover needed. If one's vessel does not have a transfer pump they are easy enough to install. Then if so inclined add an inline spin on fuel filter or two after the pump for "polishing" the transferred fuel.

As mentioned previously, unless your "polishing " filter is set up to draw from very bottom of tank, its debatable usefulness is moot.

 

[catalinajack]

Our vessel has a crossover line between between the two main tanks. The valves have never been opened since the vessel was new. A very nice fuel draw/return manifold for the 3 engines and between the 4 tanks is quite intuitive. No logical reason to use the crossover other than to add a confusion question.

Most vessels with multiple tanks have fuel transfer pumps, thus no crossover needed. If one's vessel does not have a transfer pump they are easy enough to install. Then if so inclined add an inline spin on fuel filter or two after the pump for "polishing" the transferred fuel.

As mentioned previously, unless your "polishing " filter is set up to draw from very bottom of tank, its debatable usefulness is moot.

Your assertion that most vessels with multiple tanks have fuel transfer pumps is probably a bit of an overstatement. If that were so, please explain the multiple threads on installations of same.

 

[sunchaser]

Your assertion that most vessels with multiple tanks have fuel transfer pumps is probably a bit of an overstatement. If that were so, please explain the multiple threads on installations of same.

CJ
Good point, especially on older or smaller vessels.

The fact remains though that with a fuel transfer pump the need for a crossover seems negligible. Plus then all the benefits derived from a transfer setup, whether for filling a day tank, "polishing,"moving fuel for ballast or wanting to isolate older from newer fuel.

We have a fuel line as part of the transfer system that allows movement off the vessel either to rid of potentially bad fuel (never seen it) or send to another vessel in need of fuel.

 

[Codger2]

I would not run fuel through both Racors at the same time - it would defeat the ability to switch quickly when a filter begins to clog.

Exactly! You would be defeating the whole reason (design) of the duel Racor!

 

[Ang]

On my 37, the main engine supply and its return are connected to the port tank. Genset supply and return, and diesel heater supply, are connected to the stbd tank. I keep the crossover valves open, so the fuel levels even out.

Re other posts:

I would not run fuel through both Racors at the same time - it would defeat the ability to switch quickly when a filter begins to clog.

Some NT32's were equipped with Volvos - maybe 2007-2009.

Our Nordic Tug has a Volvo D6-280. Nice design on the fuel filter. A while ago we had water and crud in the fuel tank. Added a valve to the base of the primary Racor to bleed out water. Also did a lot of Racor filter element changes. After a few months the issue cleared out. For what it's worth.

Cheers,

 

[firehoser75]

PDXstriper,
The era of Nordic Tug 37 that you are considering (at least for the one's I have knowledge of) operate the way Richard Cook of Dream Catcher describe. There are 2 fuel tanks in the boat, one on each side, and they are the same size. Each tank can operate independently (with the cross over line closed) and there are only the shutoff valves at the base of each tank, 2 valves on each tank (both at the bottom of the tank). One valve closes the fuel supply (at that tank), and the other valve closes the cross over line at that tank. The port tank supplies the main engine and if the main valve on that tank is closed, then no fuel will reach the engine (fuel returns to the same tank (enters at the top of the tank) and does not have a shutoff so no issue with forgetting to open it). The starboard tank supplies the generator and diesel furnace, with the return going back to that tank, again no shut off in the return line. You can run fine with the cross over line closed (if you want), but having it open will allow the 2 tanks to "balance" themselves and will give the main engine access to all of the fuel on board. It is very simple, no pumps are needed! However, if desired, a pump (and filter if polishing is desired) could be installed in the cross over line if you ever wanted to pump fuel from the starboard tank (generator tank) to the port tank to achieve a situation where one tank has more fuel in it than the other (for example for athwartship balance). However, it would require careful monitoring as you could end up pumping fuel out the vent if you "overfilled"
Personally, I like the simplicity (so no pump for me), and I let the engine "polish" the fuel. It will "go through" the entire port tank in about 3.5-4 hours of run time. This is for a 2002 NT 37 with a Cummins 6BTA engine.

 

[Capitaine R]

Thread wandering alert.

So our 32 NT has a 1986 Cat 3208t, 300hp and a single 200 gal fuel tank. Does anyone here know what the fuel return rate would be.
I have tried to search for this answer with no luck.

 

[Conrad]

Blue Sky, an NT42, has two tanks, port and starboard, with no crossover line.
And yet the tanks balance themselves with no intervention on my part. Having never opened them up to see the internals, I can only draw one conclusion, but if anyone has a better and wiser suggestion, I'm open to it.
I believe that the fuel pickup and return lines both have tubes that enter at the top and extend down to almost the bottom of the tanks. What that would do is allow the head pressure of the higher level tank to feed the fuel pump to the engine, while the head pressure of the lower level tank would preferentially allow the return flow to go to it.
It seems simple, but I've never heard of the practice before. (Blue Sky is hull #1 so it might have been a one off.)

 

[OldDan1943]

The advantage of fuel polishing systems is, you can polish your fuel at the dock and transfer fuel without starting the main engine.

 

[rjm911]

Good article from Steve D’Antonio

https://stevedmarineconsulting.com/?s=Polishing

 

[Newtrawlerowner]

Fuel Polishing

Hi,
I am getting close to deciding that a Nordic Tug 37 to 42 may be right for me. Budget-wise I am probably looking for a 15+ year old boat. My last boat had twin diesels and so I am experiencing the no-doubt common concerns about keeping that one engine running. So I've been researching fuel polishers.

I've seen some Nordic Tugs on ad that have fuel polishers so others have crossed this bridge before. I'd appreciate any and all thoughts on:

1) what system did you choose and why?

2) are you happy with it?

3) how complex was the installation?

4) what did it cost you?

5) would you install a fuel polishing system on your next boat and would you use the same system?

Thanks. Sorry I guess I ask a lot of questions. I was always that kid in class that asked all the questions. I can't help it.

Pete

Having not purchased a trawler yet, I did have a diesel powered sailboat for 5 years. I changed the fuel filters at every oil change and never had any crud. I used a fuel saver/extender and as others have said, clean low sulfur fuel is the best way to avoid issues.

 

[sunchaser]

The advantage of fuel polishing systems is, you can polish your fuel at the dock and transfer fuel without starting the main engine.

A fuel polishing system (or better said an in line filter) is not necessary to allow fuel transfer while at the dock.

 

[Northern Spy]

Another thing to be aware about is that no two Nordic Tugs are really alike. They bordered on semi-custom and many have a lot of owner influence design attributes when constructed. I don't think they built a lot of spec boats.

Well, perhaps moreso the older vintage ones.

 

[Martin J]

New polisher

Hi Guys

Just finished making my own polisher. Using Racor 900 Dual

I've just got to finish the 5/8" soft copper to all the tanks feed + return over the next few days. It has the capacity of 180gph using the pump.
I can also gravity feed approx. 80% through the racor's from my 4 main tanks to the 1400 gall day tank.
Also built in is the option to dump 100% of any of my main tanks (2200 galls) to the Day tank (1400 galls).
I probably did the whole thing for under $1000.

 

[Bkay]

Hi Guys

Just finished making my own polisher. Using Racor 900 Dual

80% through the racor's from my 4 main tanks to the 1400 gall day tank.

Nicely done. But I have to ask - you have a 1400 gallon day tank? How long are your days??

 

[Martin J]

I have 3600 approx. galls in total in the 5 tanks. Needless to say I don't fill up. No point burning fuel to carry fuel. The "day tank" actually holds a week of steaming