Thursday, October 15, 2009

How to Store Diesel Fuel



An Israeli Jerry can. The irony.


Both of my vehicles are diesels. They get better mileage than comparable gas vehicles - the VW TDI averages 50 mpg and goes 700 miles between fill-ups. Diesel engines last about twice as long as gas engines - they tend to operate at lower RPM's, and their fuel has superior lubricating properties. They're more reliable, with no spark plugs, no ignition coil, no distributor, no plug wires, and no oxygen sensors in the exhaust system. They could run on heating oil in a pinch, although that's illegal because heating oil isn't taxed.

Diesel is less volatile than gasoline, with a far longer "shelf life". And it's much, much safer to store. Gasoline is more dangerous than dynamite. (I recently read the blog of a fellow who stores cans of gasoline in an apartment closet. Wouldn't be surprised if he wins a Darwin award some day.)

I try to keep a small supply on hand, and think old-fashioned "Jerry cans" are the best storage containers. They're rugged, stackable, easy to pour from, and they don't "breath" like plastic containers. A dozen Jerry cans equals 3,000 miles in my car or 1,020 in my truck. Of course, our nanny state has made them illegal because they don't have child-proof caps or CARB ("California Air Resources Board") compliant spouts. "Pre-ban" Jerry cans are still sometimes available at surplus stores with the warning that they are not to be used to store fuel. What can I say.

I will share the results of my internet research with you, because I love you all:

There are two common problems with storing diesel fuel:

1. It begins to oxidize as soon as it leaves the refinery. Gums and sediments that clog fuel filters form. The process can be slowed by keeping it cool and by adding stabilizers.

2. Water, usually from condensation in the empty part of the storage container, is the medium for algae growth. A slime that will again clog fuel filters results. Adding biocide will prevent algae growth, but better yet is to keep it in a sealed, full container and in a stable temperature to prevent water from condensing in the first place.

Those who store large amounts of diesel for long periods (deep water sailors, the military, nuclear power plants with back-up generators) periodically test and "polish" their fuel, filtering and adding additional stabilizers. For us little people, rotating stocks is more practical, but funnels with built-in filters are available.

Exxon's website says that: "If you keep it clean, cool and dry, diesel fuel can be stored 6 months to 1 year without significant quality degradation. Storage for longer periods can be accomplished through use of periodic filtrations and addition of fuel stabilizers and biocides."

Chevron says: "those who store diesel fuel for a prolonged period, i.e., one year or longer, can take steps
to maintain fuel integrity. The steps below provide increasing levels of protection:
1. Purchase clean, dry fuel from a reputable supplier and keep the stored fuel cool and
dry. The presence of free water encourages the corrosion of metal storage tanks and
provides the medium for microbiological growth.
2. Add an appropriate stabilizer that contains an antioxidant, biocide, and
corrosion inhibitor.
3. Use a fuel quality management service to regularly test the fuel, and, as necessary,
polish it – by filtration through portable filters – and add fresh stabilizer."

BP says: "Under normal storage conditions diesel fuel can be expected to stay in a useable condition
for:

12 months or longer at an ambient of 20ºC.
6-12 months at an ambient temperature higher than 30ºC.

As diesel gets older a fine sediment and gum forms in the diesel brought about by the
reaction of diesel components with oxygen from the air. The fine sediment and gum will
block fuel filters, leading to fuel starvation and the engine stopping. Frequent filter changes
are then required to keep the engine going. The gums and sediments do not burn in the
engine very well and can lead to carbon and soot deposits on injectors and other combustion
surfaces."

Cenex says: "If storage exceeds one year, testing is recommended."

Diesel fuels are blended for different seasons and regions. "Summer" diesel may cloud or gel at cold temperatures.

From BP: "Always purchase fuel to replenish stocks in the winter season. This will
ensure that the fuel will not cause wax problems whatever season it is used."

According to Exxon: "Non-winterized diesel fuel will not generally cause problems as long as temperatures are at or above 10°F."


So the basic strategy boils down to:

1. Buying "fresh" fuel (the quotation marks are because it's probably already several weeks old by the time it works it's way from the refinery to us consumers).

2. Topping off storage containers, leaving just enough headspace for expansion and contraction, but not much for condensation.

3. Keeping it dry and cool. Heat speeds deterioration, temperature swings will cause condensation.

4. Adding a stabilizer to slow oxidation if storage in warm temperatures or beyond a year is anticipated.

5. Adding a biocide to prevent algae growth (or better yet, keep it in a sealed, full container and in a stable temperature to prevent water condensation in the first place).

6. Rotating stocks every winter.

7. When in doubt, filtering. The "Mr. Funnel" plastic fuel filter funnel from Amazon.com has a good reputation. (The same funnel is marketed under several different names but for a lot more money.)




Interesting historical trivia: "Jerry cans" are so-named because they were originally designed and stockpiled for the German Wehrmacht during the build-up to WWII. Transporting and storing fuel in combat conditions was a critical problem as armies became mechanized, and Jerry cans were a secret project ordered by Hitler. They can be stacked with little wasted space. Their three handles allow easy carrying by either one or two people. The small built-in air space allows for expansion while minimizing condensation, and ensures that they'll float even when full. A traveling American engineer recognized the value of the ingenious design and stole three of them during an adventure that reads like a spy novel. They were subsequently delivered to America and Britain and reverse-engineered. I've also seen French, Swiss and even Israeli copies.

8 comments:

-Humongous said...

Dude, I've heard that one before. But I'm gonna step out and trust you on this. I... I love you too.

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Scotty said...

good article.. thanks for the references. I've got a tdi vw, too, & wanted to have a few gallons of diesel around. I'll have to look around for some of the metal jerry cans, if plastic ones are not good. Is it because they 'breathe', that diesel isn't good to store fuel in them? I'd like to store ~20 gal or so in the basement.

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Portable Diesel Engines said...

Interesting facts about storing the diesel fuel!