| Author | Message | ||
| Mark Halley (Comet) (64.154.188.26)
Rating: |
Hi everyone. This is my first post to this board. Some great wisdom on this board. My question is, I am interested in buying an older (50s-60s) GMC bus either already converted or in need of conversion. My wife heard from a friend that older buses have fuel tanks that are unsafe and can explode like a Ford Pinto. She heard it from a friend that used to live in Alabama where she claims there was lots of news coverage on the topic. Does anyone know about this and can the problem be fixed? I have not been able to find anything on the 'net about this. Thanks | ||
| Peter Broadribb (Madbrit) (216.67.207.242)
Rating: N/A |
Sounds like may be a confusion over the GMC and Chevy pick up saddle tanks which had that side impact problem. Peter. | ||
| RJ Long (Rjlong) (24.127.74.29)
Rating: N/A |
Well Mark, your better half's friend is partially correct. I think what she's referring to is a gasoline-powered, dog-nosed, ex-school bus that collided with a wrong-way drunk driver in NC in the early '90's. The impact took place on the right front side of the bus, driving the framework of the front door's steps into the fuel tank, which was mounted outside the frame rails directly behind the door. The resulting fire killed several people on board the bus, as well as the drunk that caused it. At the transit agency that I worked for (in Operations Management), we had a "New Look" Flx transit (like Scott's) get T-boned by a red-light runner in a big Olds 98 right at the fuel tank. The CHP calculated that the Olds was doing approximately 45 mph upon impact, and the bus was doing about 35. The collision tore the air tanks off the coach, and split open the fuel tank, dumping approximately 75 gallons of diesel out on the street. There was NO fire. The bus driver, a 25-year veteran, calmly let the spring brakes bring the bus to a halt (didn't have a choice - air supply was lost), opened both doors and evacuated 27 passengers to a safe location about 100 feet away from the scene. The driver of the Olds had to be cut out of the car with the "Jaws of Life" by the fire department, but interestingly enough, because of her seatbelt usage, suffered only a broken ankle and some cuts from flying glass. The point of this little dissertation is two-fold: the fuel tank on the GMC highway coach is pretty well protected, and that diesel fuel is not nearly as flammable as gasoline. These things aren't Pintos!!! So find yourselves a nice 4104 or 4106 and go cruisin'! RJ PD4106-2784 Fresno CA | ||
| FAST FRED (65.56.24.6) Rating: N/A |
The usual problem with the fuel tank in an early coach is that the coach owner was too lazy to remove the water that collects from condensation , or poor fuel handeling. This causes leaks , the tank rusts thru from the inside , and bugs, little micro organisms that live on the water fuel interface and eat the fuel. The drain plug is the cure , with a dose of Bio Bor for good measure. If the tank is leaking, From the last issue of Power and Motoryacht magazine comes news of a product to repair cracks in metal tanks containing hydrocarbons. Claim is it is superior to fiberglass or epoxy. http://www.belzona-western-ltd.com/ Any vehicle can have a big problem in a crash , coaches have a great safty record , that's why the liability insurance is so cheap! FAST FRED | ||
| Ian Giffin (Admin) (64.228.43.146)
Rating: N/A |
Hi Mark, Fuel Oil No.2 (diesel fuel) has an ignition temperature of 494F (257C), a flash point 126F to 204F (52C to 96C) and an explosive limit from between 0.6% and 7.5%. In other words, unless there were to be direct flame impingement on a near empty bus fuel tank with the filler cover open, there is about as much chance for an explosion as there is a chance that Fast Fred and Ace will become best friends: Not likely, but not impossible... For example, this warning appears on the MSDS sheet delivered with diesel fuel from Amoco Oil: "The container for this product can present explosion or fire hazards, even when emptied. To avoid risk of injury, do not cut, puncture or weld on or near this container." Understand the inherent danger, but also understand that these conditions very seldom exist. Regards, Ian Giffin www.busnut.com | ||
| Ian Giffin (Admin) (64.228.43.146)
Rating: N/A |
Hi Mark, I guess I should have made a comparison of diesel to gasoline to demonstrate the differences in the figures I stated in my previous message. Gasoline has an ignition temperature of 482F (250C), a flash point of 70F (21C) and an explosive limit from between 1.3% to 7.1%. This comparison shows that although the two fuels have about the same explosive limit and ignition temperature, gasoline has a substantially lower flash point, which is the reason gasoline ignites more readily than diesel fuel. Ian www.busnut.com | ||
| Tom Caffrey (Pvcces) (64.114.233.197)
Rating: N/A |
Hi Ian, what do you read out of the explosive limit specification? In other words, how can you use this information? Many years ago, it seemed like gasoline might have had a lower flash point, because I saw flames spread across some very cold, freshly poured gasoline. I do realize that they are always working on gasoline formulations, so if there had been a pretty big change, it wouldn't surprise me. It seems like modern gasolines sour easier than older ones. I took that to mean that the fuel is a little heavier now, with a small amount of a more highly volatile ignition component (maybe benzene) used to help get it burning in an engine. If that is lost through evaporation, then the fuel acts a lot more like diesel if you're trying to get it to burn. It can be real stubborn in outboards, for example. Thanks for the specs. Tom Caffrey PD4106-2576 | ||
| Ian Giffin (Admin) (64.228.55.190)
Rating: N/A |
Hi Tom, Great question, long answer... I'll start by stating that only vapor burns, not a given product, be it gasoline, diesel fuel, a log in the fireplace, etc. Each of these ignitables (as I call them) gives off vapor as a result of being heated. The vapor itself is what burns. To demonstrate this, strike a match, hold it horizontally and look at the flame. The flame appears to be burning above the matchstick. This is not an optical illusion. The wood is not, and will not, burn. The vaporization of the wood, as a result of being heated, is what you see burning. This phenomenon is true of all things that "burn". For ignitability to occur, 2 conditions MUST exist: 1) Diesel fuel must be heated and evaporate into at least a 0.6% "vapor in air" mixture in order for the vapor to support combustion. If this mixture is above 7.5%, the vapor cannot burn. - AND, at the same time - 2) The ambient air temperature must be at least 126F. If the temperature is above 204F, the vapor cannot burn (until the entire liquid product reaches a temperature of 494F, at which time it will all vaporize at once and burn off quickly - also known as flashover). Therefore, it is nearly impossible for humans to survive in the temperatures stated for any length of time and the diesel fuel would have had to dissipate to almost negligible amounts for the product to become ignitable. Additionally, this fuel/air mixture would have to have considerable stability AND be somewhat contained for conditions to exist for it to actually explode. By stable, I mean that fuel/air mixture has to remain constant for some time (impossible in even a light wind, for example). Additionally, fire is more likely a scenario than an explosion in ALL vapor/air mixtures. These conditions MAY be present in the mechanic's shop while he is welding your fuel tank, for example, but that's why he has air blowing inside the tank while he is working. You are safe in almost every other circumstance, though. So, a quick review of the flammable liquids you carry on board your bus, or store in your garage, might be in order. Take the stuff with the lower flash point temperatures out of your garage (such as gasoline and propane) and store them outside in a ventilated bay or in the shed with lots of air circulation. Understand that ignition temperatures, flash points and explosive limits are closely tied to each other. You can use this information to know what can be safely transported within your bus and what must be stored outside in the fresh air. Hope this helps, Tom. Ian www.busnut.com | ||
| sancarlos (198.81.17.44) Rating: N/A |
If you make any repairs or modifications to the tanks or lines do not use galvanized metal. Diesel reacts with zinc and will clog the filters and system. | ||
| comet (Comet) (64.154.187.119)
Rating: N/A |
Thanks everyone, I didn't think this was a problem and I had already explained the lesser volatility of diesel to the wife. She just asked me to check this out before we take the "plunge." | ||
| Ace (24.28.44.126) Rating: N/A |
Ian, I just got back from visiting Mickey & Minnie for the weekend and I must admit, your funny! I only thought I was too tired to laugh but you proved me wrong again!  Ace | ||
| keith andrews (24.237.147.115) Rating: N/A |
Ian if I stick my finger in say a candel flame is it the vaporization of my finger or the burning of my "finger vapor" that hurts? OUCH! Seriously do you have the same numbers for propane and 100LL (100 octane aviation fuel) or is it the same for all gasoline. I have often wondered why aircraft fueling up with 100LL allways use a ground line but no one does when fueling up their autos. I became so paranoid of a fire when I used to fly skis in the winter I would rig my plastic gas cans so that there was a ground wire running from inside the can attached to a coil ( so it would'nt fall out when I started pouring ) to the bottom of my wing tanks, with a lead sinker on the end. THe idea of course was to keep a static spark from igniting the fuel vapor inside the fuel tank by bonding the can and its contents to the fuel in the tank. I often wondered later if my efforts were incomplete as I suppose a static discharge could have occured between myself or my clothing and the fuel. Now I could have attached an alligator clip to my tounge with a ground line running to the exhaust pipe or fuel tank but that seems a bit silly. I don't think it is silly however to take fires very seriously and always carry at least a couple extinguishers in a motor home and I also like the idea of a fire blanket. I have the scars to remember what happens when you don't take fire serious enough. The notion of static sparks from fueling a diesel powered bus are ludicrous but I suppose in the case of a propane leak (which many people do carry) an intricate knowledge of bonding, static charges,flash points, ect could be valuable. Ian thanks for the technical information just the sort of thing I love to see here. I searched around and even pulled out my old organic chemistry text book as you got me thinking about other questions. enjoy the ride Kilo Alpha | ||
| Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A |
Kieth, Ground lines are used for fueling planes because flying thru the air, they can accumulate many thousands of volts of static charge, and when they land, the tires are good insulators so the charge, if any, stays with the body of the craft. Plus the craft has a good-sized surface area so the spark can be pretty fat. Cars don't do that, and it's never been much of a problem, but I don't have a "real world" answer as to why. However you will see tankers use a ground clip before dumping into filling stations. Propane fill-line hoses all have stainless braid inside them and the metal filling nozzel is firmly screwed to the tank first, so again, no problem-it takes care of itself, and supposedly there are no leaks, right, so there's nothing to ignite when you're hooking up your fill hose... Again, it's all because of the flash points of diesel, gasoline, and propane that they can or cannot be easily ignited with a spark... Propane is already a gas and super easy to set off, especially because it's heavier than air and tends to pool up and stay around... gasoline is next- it's not a vapor but it's easily turned into one at comparitively low temperatures although those vapors are lighter than air and go away fairly easily... and diesel, well, you'd have to sit there on a pretty hot day to be able to ignite the stuff with your pizeo lighter- you'd probably be dead from the heat first!! It's my personal notion that diesel can be treated fairly casuallly *by comparison*, gasoline gets my attention, and propane... it's serious stuff and needs serious attention. Propane leaks are verboten, period. (I've personally watched a Cat D-6 get knocked over on it's side and a concrete wall have it's paint set on fire, not to mention three blocks worth of windows blown out from a propane filling accident) Propane systems should be designed properly and if you don't know what you're doing, ask a pro first. I am one of those guys who does everything myself... way back when I did my Superior bus's pusher conversion from gas to propane engine, I was Mr. Know-it-all and fairly mad that no-one would sell me the propane conversion parts untless I was "certified"... so I ended up going to a week long propane school, got my certificate (big deal..) but I have to say that I also gained a very healthy respect for the gas and found that the things I learned were very valuable. Simple stuff you'd never think of like where to vent the tanks' relief valve (up and out the back of the bus, and with pipe and fittings that don't mind being cryogenically frozen) and little info bits like what happens to a propane liquid line when it's shut off at the tank AND the engine... filled with liquid that loves to expand with heat and no-where to go...oops... Uh-Oh, you got me on my propane bandwagon again...Ok I'll quit... ..and I wanna see a photo of you and that alligator clip atached to your tongue!!) Cheers Gary | ||
| FAST FRED (65.56.24.221) Rating: N/A |
The current issue of EAA Experimenter discusses a fire caused by static electric and a plastic funnel. grounding is needed , even with plastic. FAST FRED | ||
| Scott P. (205.188.192.53) Rating: N/A |
A long time ago when I was studying to get my FAA Airframe and Powerplant licenses, my instructor said that in partially full, closed containers, gasoline's high vapor pressure ensured that the vapor concentration in the closed tank would exceed the high limit of the explosive mixtures and would therefore be non-explosive. On the other hand, diesel fuel's vapor pressure is such that the concentration of vapor in the closed container will be within the explosive limits. He went so far as to say light a match inside a sealed gasoline tank, nothing happens. Light a match inside a sealed diesel tank, BOOM. Not real world situations, but it is something to think about. Scott P. | ||
| Jayjay (65.142.15.14) Rating: N/A |
The current "boogie-man" in the fueling world is plastic containers sitting on (or in) a plastic base. i.e., a pickup bed liner, or an SUV tailgate. Security cameras at several gas stations have recorded the LARGE static spark that started huge explosions and fires. According to an NFPA training film, (which I saw part of while employed in a petro-chemical plant) there were numerous fires started this way. Set the can out on the ground and the worst of the hazard disappears. It seems the plastic/plastic combination creates too long of a ground path for the normal dissapation of the static charge. New rules for gas stations are on the way, and I've already see the new signs in several stations. Look for them soon at a location near you. Cheers...JJ | ||
| Tom Caffrey (Pvcces) (64.114.233.188)
Rating: N/A |
Thanks, Ian. I wondered if it was the required mix of fuel vapor and air, and you've answered that. I also remember from a long time ago that unless the gas and air mix were within a certain range, it couldn't be ignited. The range that I remembered was 6 to 16 percent. I was talking to some people around the same time about combustibilty of natural gas mixes, and could have gotten them mixed up. I had no idea that the mix for diesel vapor and air could be so lean unless heated by compression, so I will try to make allowance for that in the future. Keep up the good work on this board, Ian. If I can get on the internet, I check it for sure. Tom Caffrey PD4106-2576 | ||
| Johnny (65.235.213.118)
Rating: N/A |
I was a little concerned about the gas tank on my skoolie (passenger side, sidesaddle, behind the door) being vulnerable. Now, I'm VERY concerned about it! Any ideas? The GM pickup thing was 100% scam, BTW. | ||
| RJ Long (Rjlong) (24.127.74.29)
Rating: N/A |
Johnny - In CA, most dog-nosed skoolies have their fuel tanks located between the frame rails immediately behind the rear axle, with an additional frame crossmember providing protection from rear-end collision. The CHP feels that this provides the best fuel tank protection (combo of long overhang, mounting between frame rails, additional crossbracing, etc.) for this type of coach. Pushers are required to have their fuel tanks located between the front and rear axles, and they must be protected against T-bone-type collisions (I'm talking about skoolies here). Chances of the type of accident I referred to earlier happening again are very slim, but still possible. Only YOU can decide what's safe for you. HTH, RJ PD4106-2784 Fresno CA | ||
| John the bsuboy (12.73.163.218) Rating: N/A |
Johnny, The fuel tank on my GMC/BB is located behind the passenger door, which sounds the same as yours. It is very stout and is also protected by a steel cage. The filler cap is heavy duty also. School buses, especally the newer ones, have a lot of safety engineered into them. Gotta keep those kids safe! John the busboy | ||
| Ian Giffin (Admin) (64.228.43.148)
Rating: N/A |
Hi Kilo Alpha, Tom and others... I guess I should pay closer attention to THE BOARD, since some of the messages are directed at ME! Please excuse my delay in answering... Duh! KA, the numbers for propane are: Ignition Temp - minus 43F Flash Point - minus 156F Explosive Limit - 2.1% to 9.5% If your reaction to those numbers is, 'wow, scary', you would be irrefutably correct. For 100LL (Avgas) (otherwise known as Naphtha): Ignition Temp - 824F Flash Point - minus 46F Explosive Limit - 1.3% to 7.1% How does explosivity occur? An increase in temperature creates a more hazardous condition because of the increase in the rate at which vapours are evolved. The faster the rate of rise in temperature, the greater the chance of an explosion. Thus, the ignitability difference between normal temperature rise and the impingement of direct flame. This thread has spoken to a number of new terms. Here's a glossary: Ignition Temperature - the minimum temperature required to initiate or cause self-sustained combustion, in the absence of a spark or flame. Flash Point - the lowest temperature of the liquid at which it gives off enough vapour to form an ignitible mixture of vapour and air immediately above the liquid surface. A flammable liquid has a flash point below 37.8 C (100F) while a combustible liquid has a flash point greater than 37.8 C (that's why I referred to these products as ignitables, not flammable or combustible - avoids confusing terms). The lower the flash point, the greater the potential fire hazard. Explosive Limit - is the range between the lower explosive limit (LEL) and the upper explosive limit (UEL). The LEL is the lowest concentration of vapour in air which will burn or explode upon contact with a source of ignition. Below the LEL, the mixture is too lean (i.e. there is insufficient fuel). The UEL is the highest concentration of vapour in air which will burn or explode upon contact with a source of ignition. Above the UEL, the mixture is too rich to burn (i.e. there is insufficient oxygen). To speak to the issue of static electricity, let's keep it very simple. Static electricity has extremely high voltage but almost no amperage. Thus when you shuffle across the carpet with wool socks on and touch your wife's earlobe, two things happen: 1) big lightning bolt and a 'crack' and 2) your wife punches your lights out. But, the release of electricity doesn't kill her. However, the temperature of the 'lightning' spark is hot enough to make ignitables go BOOM because, as explained above, the sudden increase in temperature creates a more explosive atmosphere, if for only a split second. But that's all it takes! Simply stated, a vehicle's fuel tank makes a 'suitable' earth ground through the vehicle's steel filler nozzle through to the tires. Not so with aluminum aircraft (with a hugely lower flash point) nor plastic gas cans in the plastic liner of a pickup truck (which is why you MUST take them out of the truck and fill them on the ground). Hope this info is helpful in understanding fuels and their handling more safely. Regards, Ian www.busnut.com | ||
| RJ Long (Rjlong) (24.127.74.29)
Rating: N/A |
|@n - Your postings about fuel flammability are extremely interesting and informative. Thank you for sharing with us. I think you've mentioned it before, but aren't you (or weren't you) involved in the fire safety industry?? RJ PD4106-2784 Fresno CA | ||
| Ace (24.28.44.126) Rating: N/A |
I@N has been known to put out a few fires... even ones on this BB! Right ole' buddy? How ya doing I@N? Ace & $usan | ||
| Ian Giffin (Admin) (64.228.55.30)
Rating: N/A |
Hi RJ, Thanks for your kind words. The topic can easily put the reader to sleep as it does in my case... I fell off my chair several times just composing that one message! :-) In my real life, I am a Training Officer at a local fire department. I was promoted last March after having been a Firefighter for the past 14 years. Thanks for asking! Ian www.busnut.com PS. Doin' great Ace, thank you. I read your earlier message on this thread and chuckled back at ya!! A few smouldering embers here and there is ok by me. Nothing a few mouse clicks hasn't been able to put out. Even if we haven't always seen eye to eye, I've always been a big fan of yours, bud. If we were all the same, life would never be this interesting, would it? ...Ian | ||
| keith andrews (24.237.148.162) Rating: N/A |
Your posts are appreciated. Enjoy the ride Kilo Alpha |
