FATS (Fuel Air Trap System)

[Daless2]

FATS (Fuel Air Trap System)


FATS as an acronym for the Fuel Air Trap System.

FATS was originally developed last year in an effort to address and help manage the problem of fuel spillage and associated safety issues of fuel spillage during ERoCC off road Rock Crawling Events.

I have recently received several requests to put this rather simple design up on the web and available for use by those who may want to employ it.

Please understand, if you have a better design, good for you! I encourage you to please make it good for me by posting it and sharing your solution with the rest of us.

Here was the specific request, which this design is engineered to help manage.

?What can we do to prevent fuel from leaking from the vent lines on competitor vehicles?

Right now we require a rollover valve and that works ok when vehicles are upside down.

The problem we have is when a vehicle is laying on its side or climbing a hill we get some pretty serious leaks. I am trying to come up with a way that will prevent this as inexpensively as possible.?


I believe you will find FATS a low cost easy to implement solution that will provide the function needed to resolve the safety and environmental issues you are dealing with.

If you think this idea has merit please feel free to distribute this document to the other folks for their comments and input. I?m sure with other?s input we can collectively fine tune this and make it even more effective.


FATS Functional Design

FATS employs a simple plumbers trap principle (Like your kitchen sink drain.).

Please take a look at the drawing below.

You will see a fuel tank having one Vent/Valve on top. Attached to the Vent/Valve is a length of fuel hose. The fuel hose is routed in a ?specific pattern?. This pattern forms a Fuel/Air Trap when the vehicle is on its side.

The fuel line is terminated with a standard FRAM metal canister fuel filter.

That?s it!

That?s the entire FATS system.

Total cost about $15.






Fuel Hose Routing

The fuel hose must be routed in an easy to do, yet specific way.

From the vent/valve the hose extends to the left past the left side of the fuel tank on a slight angle past horizontal (See reference to horizontal and vertical reference lines.).

Once past the end of the tank, the fuel line is routed upward, again not quite vertical, but angled slightly.

Again the hose is routed to the right, completely over and past the right end of the fuel tank (Not quit horizontally).

And then lastly the hose is routed downward to a level close to (or below) the bottom of the fuel tank.

Hose routing is vital, for this routing is what makes the FATS design work.

Again, hose routing attributes are:

? Left-to-Right or Right-to-Left hose routing must always extend Past the Sides of the Fuel Tank.

? Vertical and Horizontal hose routing must not be square, but rather sloped so as to allow any fuel in the lines to drain back to the tank.

? Hose should terminate as close to the bottom of (or below) the fuel tank.


Fuel Hose Termination

The fuel hose should be terminated with a metal canister fuel filter similar to the FRAM G6567. This filter has both input and output fuel line nipples on the same side of the canister. The canister has a metal tab, which can be used to bolt the filter onto the frame.

The metal canister fuel filter will provide storage for any fuel in the attached line, if and only if a vehicle on its side (and the vent/valve is leaking) continues on into a complete roll over situation. (Without FATS in place this fuel would spill as it does now when the vehicle is on its side.)

Here is a simple drawing to show what these FRAM filter looks like.








Please note the FRAM Fuel Filter only comes into play during a full roll over. It is installed on the end of the fuel line to catch any fuel that may or may not be in the fuel lines.

I have physically measured this. This fuel filter can, can hold the volume of fuel found in 12-feet of 3/8-inch (I.D.) fuel line before spilling over.


FATS Operations

Let?s roll the vehicle over to the left, past 90 degrees and take a look at what happens.

If the vent/valves leak fuel in this position, the fuel runs into the fuel hose attached to the vent/valve, but cannot exit to the environment because of the fuel hose routing, which forms the trap.

The fuel level in the hose can only reach the vertical height of the fuel in the tank. (Physics says so.).

When the vehicle is up righted any fuel that may or may not have gone into the fuel hose will flow back into the fuel tank via gravity and the slope of the hose routing.








Here is another drawing of a vehicle rolled to the right.






Again, the fuel, which leaks past the vent/valve, can only reach the height of the fuel level in the tank. When the vehicle is righted, the fuel in the hose will flow back into the tank.

The metal fuel canister comes into play if and only if all these situations happen.

IF;
The vehicle rolls to the left or right
AND
The vent/valves Leak
AND
The vehicle continues to roll over completely

THEN;
Some fuel inside the fuel hose will flow into the metal canister filter when the vehicle is up righted.

ELSE;

All fuel flows back into the vehicles fuel tank



Practical Application

Here are a few simple drawing that show how the FATS design could be implemented on a vehicle. Please note I am showing how I would address this for a fuel tank having two vent/roll over valves link my Jeep has.

One hose (Blue) is routed on an angle from the left vent/valve to the right side roll bar upright. From there it is routed up and then across the roll bar and down the left upright. Terminating in a FRAM metal canister fuel filter. The second FATS hose attaches to the second vent/valve with similar but opposite routing.

Here?s what it would look like.







Let roll it to the left.






See! No Fuel Spillage!

Want to see what happens if it rolls to the right?

Print this off and rotate the paper! J

Actually that is a very good thing to do. Print and rotate the paper and test out all possible scenarios. I think you will see the Fuel Air Trap will work in any position, provided the hoses are routed as described. (Read that Hose Routing, though simple is vital to performance.)



I hope you find this helpful. If one person or Team is helped to be safer through its use then it was well worth the little bit of time to develop, document and post here.

Have a great day, I plan too!

Frank

[Croaker]

Very nice, very simple, AND inexpensive to boot!