Biodiesel and dual tanks

[cranetruck]

Just an observation, using a separate fuel tank for diesel and one for biodiesel/veggie oil offers several advantages.
Cold temp operation is of course an obvious one, but the fact that most of the fuel lines, the filters and IP are only exposed to biodiesel when on a drive may be a comfort factor if materials compatibility is a factor. When starting and shutting down on regular diesel, all these parts are safe from any solvent/corrosive effects from biodiesel during the majority of the time when the truck isn't used.

 

[micky]

So what are you using

for a tank selector valve. And are you heating the fuel line?
Thanks Mick

 

[jodka]

There is some interval between flipping valves to the diesel tank and the lines completely filling with diesel, right? So how do you detect that the lines have filled with diesel before shutting down?

 

[cranetruck]

There are several valves in the system. There is some exposure 100% of the time at those valves and a few feet of fuel lines and yes, the main tank and all that goes with it (pump, level sending unit, temp probes and coolant heating coil).

To monitor the fuel, I installed a potentiometer that senses the movement of the fuel "density" compensator stop block. A change in viscosity is clearly shown on my DVM. It takes about 75 seconds to replace the fuel in the lines after switching. That's about 2-1/2 quarts of fuel.
The return fuel flow can be controlled too, so that diesel goes back to the diesel tank and bio goes to the main tank.

(A search should get you lots of posts on this)

I'm installing heated fuel lines for tubing that will always carry biodiesel/veggie oil. The 1/2 (3/8 ID) inch fuel lines runs inside 7/8 (3/4 ID) inch copper tubing with fittings as needed. About 6 feet total of this.
Image below shows portion of this heated fuel line.

 

[houdel]

Bjorn, you are just awesome. That fuel line is just too much! I would never have thought of doing like that.

 

[Recovry4x4]

That fuel line idea is nothing short of brilliant Bjorn.

 

[cranetruck]

Look guys, nothing really new about that idea, Tickell's book "From the fryer to the fuel tank" shows something similar, I just adapted it to the deuce with copper lines instead of plastic hoses.

 

[mangus580]

I have seen that 'heat exchanger' idea in many a place. It is somewhere just short of brilliant.

BTW, I see kenny is enjoying his vacation.... his avatar has changed no less than 3 times in the past 24 hours

 

[wallew]

The 1/2 (3/8 ID) inch fuel lines runs inside 7/8 (3/4 ID) inch copper tubing with fittings as needed. About 6 feet total of this.

Bjorn,
I've been LOOKING FOR 7/8 inch OD pipe. WHERE did you get yours from?

This is the EXACT OD needed for the oil filter conversion. It's 7/8 16 (tpi) and I have already found the place to get the die to cut the threads from and it's about $30.

So, any help you can give with the 7/8 inch pipe will be GREATLY appreciated.

 

[Recovry4x4]

So it has Mike! Making fun of me?

 

[jodka]

It takes about 75 seconds to replace the fuel in the lines after switching. That's about 2-1/2 quarts of fuel.

A truck which gets 9MPG travelling at 55MPH would burn 1/2 quart in 75 seconds. Yet it would pump 2-1/2 quarts in the same 75 seconds? So 80% of the flow would be returned to the tank and 20% burned?

Seems odd. But then flow should be adequate for peak fuel consumption not average consumption. Also the engine would burn a greater volume of a low energy density fuel. So really not so odd.

 

[cranetruck]

Numbers that I have confirmed by actual measurements:
At idle the multifuel engine burns about 3 qts/hour.
During the same time it pumps about 30 gallons of fuel thru the system.
In a diesel, fuel is used to cool the injectors and the returned fuel will warm the fuel in the tank. In my "aux" tank, which holds about 12 gallons, the temp increases rapidly when the engine is running off it. In one hour the entire supply of fuel will have gone thru the system twice.
The flow rate is also higher at higher rpm's, but no numbers at this time.

Jim: The 3/4 inch copper tubing used in house plumbing has an OD of 7/8".

 

[jodka]

In a diesel, fuel is used to cool the injectors...

Ah. So that explains the high flow/consumption ratio. Thanks.