Monday, February 11, 2013

Differences between Gasoline & Diesel, as Fuels and in Engines

Tree planting companies go through a lot of fuel each summer, and most companies have mixed needs for gasoline (called petrol in Europe) and diesel fuels. More often than anyone would like to admit, people put the wrong fuels into equipment or vehicles, damaging the engines and necessitating expensive repairs. To try to reduce the number of incidents in the industry, I just put together a 25-minute video that explains, among other things:
- The different properties of gasoline vs. diesel.
- Differences in gasoline and diesel engines.
- Storage and labelling.
- Handling tips.

If you don't want to read any of the info in the blog post below, you can skip all of it and just sit back and watch the video, which is probably more comprehensive anyway:

Here's a partial summary of the content of the video:

Reasons why you don’t use the wrong fuel in an engine:
Diesel in a gas engine isn’t great. But gas in a diesel is much worse: very, very bad. Modern “fuel injectors” in diesel engines do NOT tolerate gasoline. Or water, for that matter. Or dirt. Replacing an injector is around two thousand dollars right now. Always make sure that you’re actually putting diesel into a diesel engine, and make sure it’s clean. Don’t use jerry cans if you can see dirt or water inside. Make sure you never leave the cap off of a tidy tank, because if it rains, you’ll get water in the tank which will go on to harm another truck.

What’s the difference between an engine and a motor?
Well, technically, they’re the same thing, or at least started out that way. In Latin, there was a term “ingenium” which gave the French the term “engin.” That later became “engine” in English. The word “gin” (as in cotton gin) also came from this root, since the cotton gin was a type of machine. Anyway, the term motor wasn’t really invented until about a century ago, and initially referred to internal combustion engines. However, common usage has changed it. There are no real clear definitions, but you can assume that an engine transforms matter interally, whereas a motor doesn’t transform any type of matter and derives its energy from an external source. So an electric motor has no moving parts, but the electricity (which comes from an external source) allows it to produce work (such as a rotating shaft). The steam engine, which was an "external combustion engine" because the steam was produced externally (in a boiler) should probably be considered a motor. The definitions are pretty vague though, and the two words are constantly interchanged in everyday use.

Chemical differences between gasoline and diesel:
Well, first they smell different, but you really have to smell both types repeatedly to learn the smells. In general, diesel smells almost sweeter (to me) and doesn’t make me sick to my stomach. However, a strong odor of gasoline will make me feel nauseated fairly quickly. If you get some on your hand, gasoline is quite thin and on a warm day will evaporate quite quickly, whereas diesel feels quite greasy. Gasoline doesn’t really change its consistency as it gets colder, but diesel does increase in viscosity, getting slightly thicker. And important, diesel burns at a lower temperature. Diesel will ignite at 210 degrees Celsius and gasoline ignites at 246 degrees. I’ll explain why this is important in a few minutes. Incidentally, gasoline is quite explosive, whereas diesel isn’t. That’s because gasoline has a much lower vapour point, so it evaporates much more quickly than diesel. Essentially, the difference between diesel burning and gas exploding is just the speed of the oxidation reaction (the flames). Diesel combusts very slowly, which we see as “burning,” and gas combusts very quickly, which we see as an explosion.

Products that are closely related to diesel:
There are several different types of diesel, but they are all quite similar in chemical composition. Interestingly, home heating oil, kerosene, jet fuel, and agricultural diesel are all very similar to the normal diesel sold at service stations. In fact, people can generally burn various types of diesel, kerosene, and jet fuel in home heating furnaces. Speaking of kerosene, some camps carry kerosene for use in large heaters for “dry tent” facilities. Basically, kerosene and jet fuel are just slightly more refined grades of diesel, with less wax content. So it's OK to burn kerosene or jet fuel in a diesel engine, but I wouldn't recommend that you try burning diesel in a space heater or a helicopter.

Clear versus Dyed fuels:
Gas and diesel are both generally sold as either “clear” or “dyed” if you go to a bulk station or cardlock facility, although normal consumer services stations usually only have “clear” gas and diesel unless you're in a fairly rural area. The difference between the two lies in the taxes added to the price. Dyed diesel is intended for farm, logging, or other types of off-road use, and does not cost as much as clear diesel, even though they are the same chemical composition. Essentially, you might say that the taxes are higher on clear diesel because the extra money goes to help fund the public highway system. Or if you want an alternative way of looking at it, farm fuel and heating oil is cheaper because it’s considered to be more of a necessity, whereas diesel for public highway use is considered to be more of a luxury.

Diesel versus Gasoline Engines:
Did you know that a diesel doesn’t have spark plugs? That’s pretty strange, eh? No fire to light the fuel. Basically, a gasoline engine is known as a “spark ignition” system, because the gas is ignited by a spark from the spark plug. However, a diesel is known as a “compression ignition system.” Let me get more basic for a second. Both types of engines have cylinders. The fuel, regardless of whether it is diesel or gasoline, burns in a cylinder and this combustion causes the piston to move within the cylinder, and that piston movement drives the rest of the engine. So anyway, with a gasoline engine, gas is mixed with air, because you need oxygen for fire, and that is injected into the cylinder, then the spark plug provides a spark which ignites the fuel/air mixture to move the piston. However, diesel doesn’t need that spark. You see, if you took physics in high school, you might remember that when the pressure of a gas (and by that I mean real gas, like oxygen, not an abbreviation for gasoline) increases, its temperature rises. So in a diesel engine, it is ONLY air that is compressed, and it gets very hot when it is compressed because the high pressure causes the temperature to spike. Then diesel is spayed into the cylinder by the fuel injector, and since diesel lights at 210 celsius, and the compressed air is hotter than that, the diesel will burn. Again, it is more of a “burn” than an “explosion.” The gas engine is a bunch of mini explosions. Now of course, a cold diesel engine makes it hard for the diesel to ignite, even when the air is compressed, so that’s what the glow plug is for. It just warms up the cylinders for a few seconds when you turn the cold truck on, to get the whole processes started. But after the truck has run for a few seconds, the metal of the cylinder is warm enough that the compressed air is sufficient warm to keep things going. Anyway, that’s all kinds of info that a regular lay person doesn’t necessarily need to know, but it’s good for a tree planter. That’s because planters deal with a number of different engines in camp, and most camps use both gas and diesel. So let’s focus on how to keep them separate, because that’s the most important lesson that you should get out of this video.

Labelling and identifying:
There are a couple ways to commonly label or identify gas and diesel. A person shouldn’t have to rely on smelling them to figure out what type of fuel you have. The first way to tell them apart is the UN Number. The UN number is a four-digit code system that was invented by the United Nations to label hazardous materials. The UN code for diesel is 1202, and the code for gasoline is 1203. This isn’t really easy to remember, so the way I remember it is that the word diesel starts with a “lower” letter in the alphabet, and the UN number is also lower. The other way to distinguish the two fuels is by the colour of the containers. Gasoline is always stored in red containers, and diesel is always stored in yellow containers. It doesn’t matter if you’re talking about a small portable plastic jerry can, which usually holds about 25 litres, or a large “tidy tank” or “slip tank” mounted on the back of a pickup, which often hold around 440 litres. This is important: you should NEVER allow diesel to be put into a red container, and you should NEVER allow gasoline to be put into a yellow container. Even if you want to do that because you don’t have another container, and you think it’s OK because you can put a label on it, mistakes happen. Someone might somehow grab that container and not realize that the wrong type of fuel is in it, and put that wrong fuel into an engine and destroy a vehicle or piece of equipment. I cannot emphasize this too strongly. Red is for Gasoline. Yellow is for Diesel.

Which engines require which fuels?
Next, you need to completely understand what type of fuel goes into an engine. In General, small engines take gasoline. So portable waters pumps, generators, and quads or ATV’s usually take gasoline. But it is possible to buy bigger generators, such as a 6000w generator, that run on diesel. Some planting camps use these, so if you’re uncertain about what type of fuel goes into a piece of equipment, ask someone who is absolutely a safe source of information. Ask your cook, ask a foreman, or ask a supervisor. For vehicles, some camps use gasoline trucks and some use diesels, and some run both types. There should always be a sticker beside the fuel tank to clarify the type of fuel that is required for the vehicle. And it is also a good practice to ensure that the designated driver of a vehicle is the only person who ever puts fuel into the vehicle.

That’s all I have to say about fuels, and if everyone in our industry understands what I’ve just talked about, we run a much lower chance of damaging equipment. And that’s good, because I’d rather see money being paid out as a higher tree price than being used to pay for senseless repairs. Remember, red for gasoline, and yellow for diesel. There should only be designated people who fuel up generators and vehicles. If you’re fueling something, make absolutely sure you know what type of fuel it needs. And finally, always replace the caps on tidy tanks and fuel barrels after filling them or removing fuel from them, so rain can’t get in to the containers.

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