Fuel Tank Equalization

Some weeks ago, I found that* I needed to replace some fuel lines so I chose to replace all of them at the same time.* During the process, I did a complete inspection of the fuel system aboard my 40 Labelle.*

I found, much to my amazement, that the generator fuel return did not go to the center day tank but fed to the port tank.* So when we ran the generator often, the vessel would develop a slight list.

So with some careful planning, I devised a crossover series of valves and lines to connect both the starboard and port saddle tanks together; now the fuel is always equalized.

What about the generator return? I was doing the same and picked up a two 3 way valves to switch both supply and returns. This way I can return the fuel to the tank it is being drawn from.

It seems like the SOP for a lot of our trawler generator installs. When I overhauled my fuel system last year, I found the exact same thing and corrected it too. However, the way I understand it, the genset really only produces a few ounces per hour of return and doesn't make much of a difference in the ballast weight over the course of a tank.

are all of your lines pumped or is there* gravity feed?

what I am wondering is that if you developed a list*would the side with the most weight on it* draw less fuel. Making the tank with less fuel supply more eventually emptying that side tank.

Say you are running a beam sea on one side you are constantly heeled over would the tank on the high side empty faster.

and if you do get one tank *with less fuel in it will it by gravity equal out?

It looks great I was just wondering.

SD


-- Edited by skipperdude on Monday 12th of December 2011 08:19:03 PM

It appears you are using the center tank as the main tank to draw fuel from.* However, there no filters to clean/filter the fuel transferring from the side tanks, and no filter for the new equalizing line.* One of the main advantages of having a main/day tank is keeping the fuel clean.*
*
We have three 400 gallon tanks and all the fuel transferred between the three tanks is filtered so if a tank becomes contaminated/dirty it will not contaminate the other two tanks. If you are going to re plumb/design the fuel system you might want to think about filtering the fuel before it is transferred to the center tank.**
*
Usually fuel lines thsat draw from the bottom of the tank have valves which are closed except*when equalize the tanks.* Same with*sight glasses the vlaves should be close excpet to read the fuel level.* **


-- Edited by Phil Fill on Tuesday 13th of December 2011 04:07:55 PM

So am I totaly off on the subject as per my previous post. Or am I just not getting my point across.

*I would hate to have my boat go belly up because of a limber line

But it does seem that it could happen. I think shut off valves should be in order.

Whadda ya think?

SD

My equilizing valves are open. They were open when I bought the boat. I only shut them when I was doing my fuel filtering from one side to the other. Then I opened them again.

*

*

I understand but*do you preceive**possibility (as outlined in my first post )where open fuel lines could cause a capsize?

SD

My main motor returns fuel to the starb tank when running from the port tank for 12-13 hrs it seems to make no differance to the balance of the boat

skipperdude wrote:
I understand but*do you preceive**possibility (as outlined in my first post )where open fuel lines could cause a capsize?

SD

Click to expand...

*No. Not at all. The equilization line is small.

I would hope none of our boats would capsize because of full tanks on one side of the boat and empty on the other...if they might cause a capsize...REALLY bad design.

Some of us with older tanks would be scared to fuel up then....there's always a possibility of a rupture that could empty one side pretty quick.

I talked to a few boat builders in my area and was told that this is a something that can and has happened.

The suggestion was to install a couple of oneway valves in the fuel lines.

SD

Shame on the builders then...NO boat I have ever been on or owned would do it...and I've run hundreds while working at various marinas and deliveries...even knowing one would do it is pretty scary...

I think there is probably a lot more to that story than fuel gravity feeding from one tank to another.

Commercial fishing vessel operators are notorious for overloading, and modifying their boats with little regard for stability. Larger boats often use fuel for ballast and if that is done for the wrong reasons - sometimes moving weight to the "high side" to level the boat is the worst thing you can do.

Transferring fuel with a small pump is boring and people have other things to do and forget about it until it spills or something nasty happens.

Unless you routinely run around with a 30 degree list from some other loading condition, the likelihood of fuel gravity feeding from one tank to the other and capsizing the boat is probably less than getting hit by a meteorite.

RickB wrote:
I think there is probably a lot more to that story than fuel gravity feeding from one tank to another.

Commercial fishing vessel operators are notorious for overloading, and modifying their boats with little regard for stability. Larger boats often use fuel for ballast and if that is done for the wrong reasons - sometimes moving weight to the "high side" to level the boat is the worst thing you can do.

Transferring fuel with a small pump is boring and people have other things to do and forget about it until it spills or something nasty happens.

Unless you routinely run around with a 30 degree list from some other loading condition, the likelihood of fuel gravity feeding from one tank to the other and capsizing the boat is probably less than getting hit by a meteorite.

Click to expand...

*Read the Coast Guard report on the sinking of the tug VALOUR in 2006.

I agree about commercial boats...routinely modified by amatuer NA's (Ha!)

But the average* rec boat with the exception of some trawlers I doubt has the tankage to make that big of a difference (list yes/capsize I doubt) and the tanks are almost always so low in the boat I just don't see it.

Possible...sure...but again...just haven't seen a rec boat yet that*I think would be in that situation.*

Like the "rule of thumb" used for guessing whether you have too much ice on the topsides...if your roll time is getting getting longer and "hangs"...then yes I would worry about stability.* I have been known to say that liveaboard cruisers better watch out just like commercial fishermen forget about mods/gear...by the time you add on deck all the cruising stuff (bikes, dingy, kayaks, propane, barbecue, extra ground tackle, stairs, etc..etc)...you may HAVE affected your stability to a degree.

dwhatty wrote:*Read the Coast Guard report on the sinking of the tug VALOUR in 2006.

Click to expand...

Yep, that is exactly what I was talking about. There is usually far more to the incident than first meets the eye.

And, FWIW, in my personal opinion which is shared by a large number of professional mariners, those ATBs exist only to avoid the rules and standards that apply to ships in order to prevent the sort of accident that happened to the Valour.

*

dwhatty wrote:*Read the Coast Guard report on the sinking of the tug VALOUR in 2006.

Click to expand...

*Wow it took a village to sink a boat.

This might be an interesting required read for one employees to read no matter what business one is in.* It points out how with in a few hours several every day "let's try this instead" actions can cause such a large catastrophic event.

We lost two crab boats with all hands, the*Americus and Altair, sister ships out of Anacortes back in 1983.* Same situation offloaded fuel and stacked the decks high with 800 lb pots.* They rolled over and sank after leaving port in Dutch Harbor on the same day in calm seas.* Extensive testing by several labs determined the design*stability had been grossly exceeded causing the loss of both boats.* The book written afterwards is "Lost at sea."

On February 3, 1983, the men aboard Americus and Altair, two state-of-the-art crabbing vessels, docked in their home port of Anacortes, Washington, prepared to begin a grueling three-month season fishing in the notorious Bering Sea. Eleven days later, on Valentine's Day, the overturned hull of the Americus was found drifting in calm seas, with no record of even a single distress call or trace of its seven-man crew. The Altair vanished altogether. Despite the desperate search that followed, no evidence of the vessel or its crew would ever be found. Fourteen men were lost. And the tragedy would mark the worst disaster in the history of U.S. commercial fishing.

Sure...lots of commercial boats are lost for all kinds of reasons...but I find it hard to compare commercial vessels with their huge tankage spread around the vessel to be anywhere's near the same as most of our trawlers/vessels....unless of course you own a commercial conversion.

I think that a good idea before casting off is to get off the boat, step back and take a look to see if there is a list and to see if she has any trim. If she does then move a few things around. A little trim to the stern is ok, meaning a degree or two, but a list can be dangerous. If you are listing to port and taking wind and waves to the starboard bow this weather can cause the list to port to be exaggerated. I think that the recreational trawlers are somewhat proportional in their design to their larger commercial sisters. Everything may be smaller in scale, but wouldn't the characteristics be similiar? I don't know for sure but it seems to make sense. Plus, when sailing, I do not want anything going on that I am not in control of and not sure of, meaning allowing fluids to move from on place to another freely and not knowing how much weight that is and when it is makes me nervous. At roughly eight pounds a gallon for diesel seems like it can sure get heavy in a spot quickly. Maybe not, I'm just trying to get a handle on the idea.

When I first got my boat, I filtered all the fuel. Having approx 1/2 tanks full, I filtered one to the other, then all back to the empty tank. So my*port tank was full and*starboard empty. (180 gal tanks each side)

The list was only a few degrees, I would estimate 5 maybe 10.

It took about 4 hours of "partying" with as many on the starboard side to get the tanks even again.

Most of our boats have cross over pipes to the tanks with valves to cut them off if needed. So how many have ANY first hand knowledge, not I heard it from someones cousin that heard it in the local grocery store check out line, of one of our types of vessels that capsized from cross overs in the fuel tanks. I think we have so many other things to be concerned with as boat owners that we don't need to sit around and worry about things that are never going to happen. I have had one tank full and the other empty, even while under way. There is no more difference than if two people are standing on one side of the boat as far as the listing. Chuck

A few thoughts:

I switch my tanks but most of the time I do'nt do it until I notice a slight list so some undesirable listing happens. Fly stuff in my opinion but it does happen. But I like to have the control. But if a list is caused by everybody going to the port rail or worse the cross-over system will allow fuel to flow over to the port side and cause more list. That's the main reason I do'nt like cross-over lines as I loose some control. And I've always been fussy about listing especially under way. I've never used cross-over tubes but one could probably boat for 100 years w then and not have a problem.*

True, we're not as complicated,*don't have ballast tanks*and like someone pointed out, fuel tanks are ballast, but are most often at or below the waterline.**Empty tanks on one side might cause a slight list and could effect handling in the wrong conditions.**But*IMHO, the capsize danger for recreational boaters*is more likely going to be from operator negligence,*too many people on board, too*much above deck load, running with too much sail, combined with high seas*or bad weather*and inexperience/poor handling skills which can lead to disaster.**

A guy at our marina was loading 80 lb bags of Quickrete on his 27 foot boat to transport*to his cabin on Decator Island.* He had 100 bags and was going to do it in one trip he thought.**Other marina patrons*were*encouraging him to split it up into at least four loads.* After insisting he could do it and had done it before, he got around 50 bags on before the boat began leaning on the dock.* If he had untied the lines, it would have rolled.**He ended up taking half of it off and made*three or four trips.* It's called the Forrest Gump syndrome, "Stupid is as stupid does!!"**

*

What?* Me list?

*

I understand it is good practice with twin engines to normally feed (and return) each engine from a different tank, so that if one tank becomes contaminated you don`t risk losing both engines. If that is right ,won`t equalization effectively combine the two tanks, defeating the practice?

BruceK

My boat's fuel tank set-up is a lesson in KISS. They are able to be closed off by a tap and each exit point, but I leave them open all the time, and the lines meet in the middle as it were, then feed the engine, with the the excess fuel return just feeding back to the primary filter. Beautifully simple, and as they drain from the bottom, no crud builds up and I release a teaspoonful of water from the primary filter bottom bowl once a year. It means they are always level, and I can fill from either side, and they will ultimately level out then as well, as I never top right up normally. If I am I add to both sides to save time waiting for the leveling to occur.

Bruce-

True in theory..but most people I've talked to about this ..at least here in the States...they have never nor heard of anyone where it would have mattered.* Mostly because you have to fill only one side from one source to prevent contaminating both sides...which people almost never do.* The good news is* that marinas here on the East Coast in busy areas are almost never the problem.


-- Edited by psneeld on Saturday 17th of December 2011 05:30:41 AM

Actually both my engines and the generator pull from the center-line tank. Fuel from the saddle tanks gravity feed into that tank. I have shut-off valves on both saddle tanks.