Static electricity and plastic fuel drums

[EdDekker]

We had a thread on plastic diesel fuel drums last week. A question comes to mind: is static electricity is a concern with the plastic (HDPE) drums?

For years I have read the instructions to place fuel containers on the ground before filling them (i.e. don't fill them when they are in the trunk, trailer or on the bed of the pick up). When I learned to fly airplanes I learned to connect the ground cable before gassing up the airplane to prevent a static induced explosion.

The stated reason for concern was a spark igniting the gas fumes, given that the moving gasoline could generate the static charge.


Now commercial plastic (HDPE) gas cans are common and as MikePA has reported, Chevron came as close as possible to recommending them for both gasoline and diesel.

With a 30 (or 55) gallon drum lifting the drum to the ground to ground it for filling and lifting it back into the trailer when full to transport it is not practical.

Is a static induced explosion not a problem with diesel? (Diesel is less volatile than gasoline. ...)

Is a grounding clip to the drum sufficient? (That is the normal HDPE drum sufficiently conductive that a single point connection to ground is sufficient.) Should a wire be placed in the bung hole down to the bottom of the drum and this wire grounded?

Does the HDPE in commercially available gas cans have an additive to make it conductive enough to discharge a static buildup?


I did try an experiment. I do not have a conductance meter (a very high range ohmmeter), I used a digital multimeter and its two probes to measure the resistance of the fuel container materials. I pressed the two probes against the fuel tank while close together (probes not touching). With the commercial plastic gas and diesel cans I get an open circuit, With bare metal I get a low resistance (about an ohm or less). The open circuit may simply indicate a resistance higher than I can measure.

I question the validity of my experiment since I also get an infinite resistance from a painted metal gas can (the paint acting as an insulator). If the 'place the gas can on the ground' technique works than the metal gas can resting on the ground is protected either by: the paint being a high but finite resistance or by the static potential reaching the breakdown potential of the paint and arcing inside the paint before reaching a potential which can spark in the air/fuel vapor mixture. Or is static not really an issue for a gasoline cans?


Ed

 

[TerryinMD]

Huh? /w3tcompact/icons/crazy.gif

What you are really asking here is will the plastic can/drum produce a dischage (in laymans terms)?

And how do you ground a large container without unloading it from your truck?

Is that close? I wouldn't mind knowing that myself.

Terry

 

[GlueGuy]

Edward,

I do have some experience in this type of thing, as I have a plastic airplane.

You're right about the type of fuel being part of the equation. 100LL avgas is very volatile, where diesel and kerosene is less volatile. What it means is the less volatile fuels give off fumes at a slower rate, and tend to be more forgiving (in a given time frame).

Plastic fuel tanks can build static electricity, but they generally don't conduct electricity. This can be adjusted by including some conductive agent in the plastic (e.g. carbon), or, as have some people with plastic airplanes, embed a conductive mesh in the composite.

One thing you might want to try with your HDPE tank is to rub the surface with silk or maybe polyester cloth. Then turn the back of your hand/forearm to the area where you rubbed it. If it's building static, then it will pull up on the hairs. If it has some sort of static inhibitor (like carbon), then it will dissipate the static very quickly, or possibly not build the static in the first place.

This is an evolving science to some extent. I've heard of a couple of plastic airplanes going up (flames, etc.) because of static electricity.

OTOH, my plastic airplane has no carbon or copper mesh or anything, and I've not had a problem in 13 years. It does build static on the surface, but the surface does not produce a spark.

The GlueGuy

 

[bgott]

The static electricity is built up in the nozzle, that's why you're supposed to keep the nozzle in contact with the fuel container while you're pumping. You're probably better off grounding the nozzle, the plastic barrel is non conductive, maybe. Gasoline and diesel is conductive. They're hydrocarbons and the "carbon" part conducts electricity. If you spill the stuff down the side of the barrel you have a path to ground. Hell, ground them both. It's also highly recommended that you don't pump fuel into jugs while they are sitting in the back of a pick-up on a plastic bed liner.

 

[MossRoad]

I used to work at the airport refueling airplanes. We always bonded the fuel truck to the ground, then the plane to the fuel truck. We were taught that jet fuel(refined kerosene) had a lower flash point than gasoline. That means it will ignite at a lower temperature than gasoline. However, gasoline gives off way more fumes than kerosene. Fuel running over plastic, especially gasoline, can build up static on the plastic drum. That's why you are supposed to put any gas cans on the ground while you fill them and keep the nozzle in contact with the can so that the can and the nozzle always have the same electrical potential on them. Never use any un-approved container to store or transport fuel. Its not worth the risk, to me, to use some old plastic barrel that I found, for fuel. Tried it once. I posted the results before. Barrel got hot one day, expanded so much that I couldn't get the cap off to relieve the pressure. Had to cool off the barrel with water hose. Drained the barrel, rinsed, cut the top off and used it for a trash can. Please be careful.

<font color=green> MossRoad </font color=green>

 

[njrqs]

Glue Guy

A plastic plane ? - Please Explain ?

I learn to fly, but mine are aluminium and I feel warm and fuzzy knowing that. Plastic ?? Hmmmmmmmm


Also, on the diesel issue, you can extinguish a match in a container of diesel. Trust me, I have tried it !!

<font color=blue>Neil from OZ.</font color=blue>

 

[Egon]

Glue Guy:
Combustion requires three items, air-fuel-ignition source. All three must be present in proper portion to get combustion. The vapour pressure of the fuel is also critical in this combination.
Yes you can put out a match in a pail of diesel because the proper air/fuel mixture was not present. You could do the same with a pail of gasoline if it was cold enough. It is also possible to fill a pail with propane not that I would advise it though.
Places like oil refineries have very specific grounding procedures when hydrocarbons are being transfered to containers.
Some previous replies are well worth paying attention to for grounding procedures.

Egon

 

[Egon]

Glue Guy:
My appologies, The post just sent was supposed to be in reply to Neil from Oz.

Egon

 

[mbjacobs]

Bottom line - storing large quantities of diesel is relatively safe, gasoline is dangerous. Flash point of diesel is typically 140 F, gasoline -45 F. The higher the flash point the safer the material. I wouldn't worry about static with diesel in plastic, I worry about gasoline in any container.

Maury Jacobs

 

[MIKE71]

I just got a 35 gl plastic drum to store diesel in. I will have to fill it while it is still in my truck. I am planning on removing the rubber bed mat each time I load it so it will not build up any extra static. It will be stored under an open shed on a stand so I can gravity feed through a hoze and nozzle. Do I need to take any extra precautions to prevent static build-up? The stand will be made out of wood. The shed is an ungrounded wood frame with metal siding and metal roof.