Please forward this message widely, the list below of hazards in the other message is very good. It all points to closed, and I mean really, really closed, systems- preferably ones capable of containing some pressure. Working outdoors reduces some of these risks but there's really no excuse not to use a closed fumeless processor. .
Here's one other dangerous variable that most people are unaware of: water in oil when making biodiesel What's that , you say? water as a fire hazard? Here's how it happens: If you pump-mix methoxide with wet oil, there is a slight danger of localised boiling of methanol (!!!!!) IF the ratios of methoxide to wet oil is high. This inproper ratio only happens if your methoxide inlet to the pump is large compared to the oil inlet, or if any valves in the two lines (oil and methoxide) are open to the wrong ratio (ie oil mostly closed down and methoxide wide open). For example, a 3/4 piece of tubing for methoxide delivery going into a pump along with a 3/4 inch oil inlet tube is what I consider a high ratio. (I now use 3/8 inch methoxide tubing and 3/4" oil, with a valve on the methoxide tube, which is only opened slightly) What happens is this: the lye in the methoxide can produce heat when it hits water (from the oil). Normally if your ratios are correct, we're not using enough lye (and there should'nt be enough water) to cause this to raise the temperature in a whole tank of (even very wet) oil. But in a pump-mix situation with incorrect tubing ratios, there is momentarily a situation in the pump plumbing where the oil/water quantity is low and the methanol/lye quantity is high- which could get hot enough to surpass the boiling point of methanol (148F/60C). If your tank isn't a closed system (and plastic conical tanks and their 'manhole' covers are not a closed system!) then the methanol vapors will boil out of your tank, and the tank will pressurise (yet another reason for avoiding plastic as a mixing tank) which means that any normally invisible leaks will spray methanol-containing hot oil/biodiesel out of the tank. You may also notice a bunch of soap being made- there'll be odd gelling if the oil/ biodiesel/methanol makes it's way out of the tank! I don't think people are very aware of this problem. Pump mixing is absolutely, hands-down superior to stirred tank mixing- and it's far easier to build a sealed system with a pump rather than a stirred tank- but you have to have the methoxide delivery be slow, both for the safety reasons above and to keep the production of soap down. I think peopel sometimes rush to mix in their methoxide (because after that step there's no more operator involvement needed) but there are a few good reasons to slow down methoxide delivery- 1. preventing the overpressure situaiton above 2. not making a bunch of soap (which happens in the above situaion because there's too much lye for the amount of oil in the pipe) and 3. making sure you get a very, very good initial mix of reactants, which is easier to control in the pump ratios rather than hoping that it'll all mix through circulation later on. not using wet oil is of course also important. > > I think Tom offered some strong clues as to the "how" of the fire. My bet is > that the boiling methanol caused frothing of the oil and boiling over the > edge of an open or perhaps even vented reactor. > > Anyway, here are some of the things that have been pointed out as potential > fire problems in the past. Doesn't hurt to place them back in the public > view once again in a composite manner. > > --- Open reactor and poor ventilation in the presence of an ignition source. > Ignition sources can be: > a) Using combustible fuels as a direct heat source (ie propane, natural > gas, wvo, wood, etc.), rather than a heat exchange system where the flame is > far removed from the processing area. > b) Open electric motor housings, rather than TEFC motors (at minimum). > c) Disconnecting an electrical appliance by pulling out the wall plug, > rather than using enclosed switches. > d) A match or lighter (open flame, Part Dieu). > > Other fire sources can be over taxed pumps and motors in close proximity to > combustible materials (garage walls, plastic barrels, almost anything), > oversized breakers and/or fuses, undersized wiring (such as 14/2 Romex) for > higher amperage draws. And there always is the danger of spontaneous > combustion in the presence of oily rags, most predominant when working with > drying oils such as hemp and linseed. This threat decreases as the > saturation of the oil/fat increases. > > There are probably a dozen other hazards that don't come readily to mind at > the moment. But these are the basics. mark adds: It's easy enough for me to suggest working outdoors since I live in California and it's fairly warm all the time. If you are indoors and are using a ventilation system, please do some research about ventilation of explosive fumes. Look on the internet, or (if I have the title correct), there's a good book on DIY ventillation called Ventillation for Artists and Craftspeople (I think) which is sometimes available in art supply stores. Don't rely on a fan or ventillation system for fume control- just DO NOT produce fumes in the first place. Use a sealed processor. use a sealed processor. use a sealed processor. another fire danger, not specific to biodiesel, is the use of very long extension cords and drawing a high power draw on them. Sometimes you'll be in this position in order to work in a shed or space outdoors without proper wiring. You need at least a 12 gauge extension cord to run an electrically heated processor, and if the cord is over something like 100 feet you want something bigger- 10 gauge cord). You should not run both your heater and your pump at the same time on one circuit in this situaion (many pumps I've used are something like an 8 amp draw, and the heater is about 10 amps). Essentially, a long cord can burn up with a high load long before your circuit breaker knows anything's wrong. This applies to any sort of electrical heating or high power draw. ------------------------ Yahoo! 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