Heating the VO tank question

For discussing the modifications needed for diesel vehicles to run with 2 tank veggie oil conversions.

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Heating the VO tank question

Postby 87wolfsburgedition » Sat Apr 21, 2012 9:22 am

I have been running my RV off of WVO for 4 years now, but am doing my first actual install with my VW Vanagon this spring. All of the technical research I have done seems to discourage the heating of the VO tank because heating is a probable cause of polymerization. We all know that we must heat the VO, but heating the tank seems inefficient since if I have a 15 gallon tank and drive 25 miles I will only be burning 1 gallon but heating all 15. Repetative heating and cooling is not good for the fuel (http://www.scribd.com/doc/88603076/Vege ... il-as-Fuel).

So, is there anybody out there that does not heat the VO tank? All of the kits advocate it (Frybrid, Greasecar, GFS, etc., etc.). I live in Oregon where the climate is temperate, do I really need a tank heater?

Here is a rough schematic of my planned installation, please give me feedback where I might be off:
Image
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Re: Heating the VO tank question

Postby John Galt » Sat Apr 21, 2012 8:23 pm

The most reliable systems have the engine coolant circuit connected like this:

╔=coolant pump====╗
╠=cab heater======╣
╠=FPHE ==========╣
╚=HOH+filter+etc===╝
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Re: Heating the VO tank question

Postby SunWizard » Mon Apr 23, 2012 3:19 pm

Drop the vegtherm. A FPHE is much more effective than a vegtherm, it provides far more heat when needed and is regulated to the perfect temperature (170-190F) all the time so no need for switching, monitoring, etc. The vegtherm is not enough heat in the dead of winter, and too much in heat of summer, and fluctuates at any time of year, like when you go downhill and the WVO flow stops with the vegtherm overheating its contents.

A heated pickup is worth it, and it doesn't heat the tank very much if its designed right. Mine is simply a 6" diameter loop of aluminum tube around the bottom of the pickup tube. It provides only a little heat which is needed to melt a small amount of the WVO around the pickup which can be a frozen solid block at temps < 20F. The problem is with large heaters or heat exchangers in their tank which get it too hot like greasecar.

Even if it never gets <20F where you live its good to design the system so you could travel to places that get that cold at night. It also allows you to run thick hydrogenated WVO and stuff with meat fats which can be solid even at 50-70F, and which is easier to find than the sweet canola which is liquid to 20F.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Re: Heating the VO tank question

Postby 87wolfsburgedition » Mon Apr 23, 2012 8:11 pm

Thanks.

Another question for the fuel tank fabrication. Do I have to use a fuel pick-up, or can I just gravity feed to a LP?
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Re: Heating the VO tank question

Postby SunWizard » Mon Apr 23, 2012 8:27 pm

87wolfsburgedition wrote:Another question for the fuel tank fabrication. Do I have to use a fuel pick-up, or can I just gravity feed to a LP?

You can gravity feed if its from near the bottom center of the tank. Otherwise when you are on a steep hill all the fuel runs to the other end and and you suck air.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Re: Heating the VO tank question

Postby merk » Mon Nov 26, 2012 11:24 am

I too just have a coil of tubing in the bottom of my tank around the fuel pickup. On long trips the tank heats up, but not dramatically.
Merk
03 TDI 12 gal marine tank in trunk w/copper heat excahnger no intank connections, coolant heated copper coiled fuel filter, HIH, two 3 port fuel valves
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Re: Heating the VO tank question

Postby beeline » Fri Nov 30, 2012 8:40 pm

I have the same heated pick up as Sunwizard, but my tank heated up considerably on long trips and had polymerization issue, so installed 2 block valves and a bypass, no issues since then and still have the option of using the heated pick up when it's cold. If I was living in Oregon, I wouldn't worry about a heated pick up, just add a small amount of diesel or jet fuel when it get's really cold. The other thing I was thinking of doing is insulating the up and down line inside the tank by putting hose around it and only having the bottom loop around the fuel pick up 'hot' to heat the oil.
1996 dodge diesel, 2 tank heated WVO conversion
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Re: Heating the VO tank question

Postby VegiCamper » Mon Mar 07, 2016 3:06 am

beeline wrote:I have the same heated pick up as Sunwizard, but my tank heated up considerably on long trips and had polymerization issue, so installed 2 block valves and a bypass, no issues since then and still have the option of using the heated pick up when it's cold. If I was living in Oregon, I wouldn't worry about a heated pick up, just add a small amount of diesel or jet fuel when it get's really cold. The other thing I was thinking of doing is insulating the up and down line inside the tank by putting hose around it and only having the bottom loop around the fuel pick up 'hot' to heat the oil.


I understand this is an older thread. Just wondering if there is consensus that polymerization can be avoided by keeping the tank from heating up above say 100°F by installing a coolant bypass and 2 valves.
As noted in my question in the poly sticky thread, the steel tank in the used van I bought is heavily polymerized and I wonder if the excessive heat (2 pipes all along the length of the tank bottom) is at fault, or the fact that it is a steel tank. The pipes are covered in a thin hard layer of black 'chicken skin', a thicker skin covers all tank walls and even the plastic fuel gauge swimmer, the tank bottom steel is blank but covered with 2 inches of soft cakes of poly swimming in murky oil.
Feels like the tank gets unnecessarly hot.
In the SF bay area my oil is usually warm enough for pumping out of the tank without heating (or perhaps just a few minutes), and after that the oil is heated plenty by my Webb 525 fuel heater and then in-hose-heated VO fuel lines, and the warm oil from the return.
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Re: Heating the VO tank question

Postby SunWizard » Mon Mar 07, 2016 5:43 pm

VegiCamper wrote:Just wondering if there is consensus that polymerization can be avoided by keeping the tank from heating up above say 100°F by installing a coolant bypass and 2 valves.

No consensus possible since its got too many variables. Proper dewatering is #1 fix. You only need to avoid heating the tank if you are keeping the same old VO in the tank for more than 2 weeks.
As noted in my question in the poly sticky thread, the steel tank in the used van I bought is heavily polymerized and I wonder if the excessive heat (2 pipes all along the length of the tank bottom) is at fault, or the fact that it is a steel tank. The pipes are covered in a thin hard layer of black 'chicken skin', a thicker skin covers all tank walls and even the plastic fuel gauge swimmer, the tank bottom steel is blank but covered with 2 inches of soft cakes of poly swimming in murky oil.
Feels like the tank gets unnecessarly hot.
In the SF bay area my oil is usually warm enough for pumping out of the tank without heating (or perhaps just a few minutes), and after that the oil is heated plenty by my Webb 525 fuel heater and then in-hose-heated VO fuel lines, and the warm oil from the return.

In SF, you never need to heat the tank. All your heat to get 160F should be provided by a FPHE near the IP, the Webb heater provides very little heat, hoses might give enough heat but would need temp measurements, and the return doesnt count since it only heats up the tank which is not needed or wanted.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Re: Heating the VO tank question

Postby VegiCamper » Mon Mar 07, 2016 6:31 pm

SunWizard wrote: You only need to avoid heating the tank if you are keeping the same old VO in the tank for more than 2 weeks.
In SF, you never need to heat the tank. All your heat to get 160F should be provided by a FPHE near the IP, the Webb heater provides very little heat, hoses might give enough heat but would need temp measurements, and the return doesnt count since it only heats up the tank which is not needed or wanted.

Thanks SunWizard,
Yes, there is a FPHE right before the IP for heating the oil to the desired injection temperature.
I was here mainly concerned with balancing the least possible poly inducing heat with the need to keep the fuel liquid enough for tank pickup and filters.

I wasn't aware of the two week rule of thumb, that helps. Typically I'll use the van for long distance trips only and usually I do a longer trip every two weeks or two using up the tank. If I do drive in between, rarely does it get driven short distances to the point of getting the oil very hot. So, the oil would typically only be heated a couple of times in the tank until it's used.
So this part of the reply seems to indicate that it's ok to keep the coolant heating always on in the tank pipes.
However tanks are never totally empty, I guess in this one 2-4 gallons typically remain at the bottom by the time it is refilled. And of course I don't always empty the tank every two weeks, sometimes I might travel or work out of town without the van for weeks or months. In that case is it better to empty the tank or fill it up to the top with as much fresh VO while it sits?

Your second part of the reply seems to indicate that at least in SF or similar weather that rarely drops below 55F it would be better not to heat the tank at all. In that case switchable valves for the tank circuit would be beneficial?
I do want to be able to heat the tank on winter(spring/fall) trips, as I go skiing in the Sierra a lot between Nov and May when nights, but also daytime temperatures can approach and often also drop below freezing.
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Re: Heating the VO tank question

Postby SunWizard » Tue Mar 08, 2016 3:40 pm

VegiCamper wrote:Your second part of the reply seems to indicate that at least in SF or similar weather that rarely drops below 55F it would be better not to heat the tank at all. In that case switchable valves for the tank circuit would be beneficial?

Correct. And your tank heat is too much even at -10F temps, all that is needed is a 6" diameter single loop of 3/8" coolant tube around the bottom of the pickup to keep that location liquid.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Re: Heating the VO tank question

Postby VegiCamper » Tue Mar 08, 2016 7:11 pm

VegiCamper wrote: ... sometimes I might travel or work out of town without the van for weeks or months. In that case is it better to empty the tank or fill it up to the top with as much fresh VO while it sits?
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Re: Heating the VO tank question

Postby SunWizard » Thu Mar 10, 2016 10:04 am

VegiCamper wrote: ... sometimes I might travel or work out of town without the van for weeks or months. In that case is it better to empty the tank or fill it up to the top with as much fresh VO while it sits?

Weeks, fill it. >3 months, empty it and put a few inches of Diesel on the bottom.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Re: Heating the VO tank question

Postby centrifuge marty » Wed May 25, 2016 9:41 pm

I use an Arctic fox in tank heater that only heats the incoming oil, I can drive for hours and the tank is only luke warm. There is no need to heat the veg tank as the oil will get warm enough with the hose on hose then into heated filter then into fphe I use 30 plate just before the injection pump. My oil is 170 before the pump except when it gets real cold -30 where it will drop to 160, I then turn on my megatherm and it will boost my temp to 170. All my hoses are wrapped in plumbers insulation under the hood and the hoses running back to my tank are wrapped in plumbers insulation then slid inside pvc pipe that runs from my engine compartment along my frame up into the box besides my tank so nothing is exposed to the cold air.
Never be impatient to switch to oil wait till the thermostat opens that way all the hoses filter fphe and tank heater are up to temp, you will know it is when the oil temp climbs straight up to 170 and stays there.
1996 Dodge Cummins extended cab 4x4
2-Tank veg oil conversion based on sunwizard design
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