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- brewsmith February 2015
- Control_Guy February 2015
- CothermanDistilling September 2015
- dad September 2015
- FloridaCracker September 2015
- grim September 2015
- jbierling September 2015
- Kapea February 2015
- Littlechicago June 2015
- Lloyd February 2015
- Mickiboi March 2015
- punkin September 2015
- razerhawg1 February 2015
- Smaug August 2015
- TheMechWarrior September 2015
- Unsensibel February 2015
All about Lower Explosive Limit (LEL) and Upper Explosive Limit (UEL)
This discussion was created from comments split from: Hello everyone from Maryland USA.
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Welcome!
Well, since you are here…
I'm trying to calculate the amount of liquid ethanol, that if turned into vapor, would be sufficient to hit 100% LEL, assuming no ventilation. So, for example, if I had 77,000 cubic feet of distillery space - how much Ethanol could be vaporized or evaporated without becoming an explosion hazard. Should I worry if I spill a gallon? Should I worry if I spill 10? This is mostly academic, since I realize that without air movement, localized concentrations will be significantly higher.
Trying to understand the appropriate ventilation requirements. I know there is a 'rule of thumb' of 1 CFM for 1 SQFT of floor space to provide "adequate ventilation" - NFPA497, but what I'm not sure is if this is overkill or if this is insufficient, since solvents/vapor can vary so significantly with regards to LEL concentration. Trying to get by without heated make up air, since every number I work out to is going to require a significant HVAC investment, not to mention operating cost.
Glad you are here! :)
Naw, just try not not spill it @grim.
I do understand that if shit happens what can I do to avoid a catastrophe, I also play that game in my mind constantly.
Power E-Stops on electrics and emergency floor flooding/washing? E-Stop button type extra ventilation?
911 on speed dial?
Pictures of Buddha on the wall?
Glad you are here @Control_Guy because I recon Buddha pictures won't save grim's butt when a 50L container of 80% booze gets knocked over and spills on the still floor.
Save grim please. I'm trying to mooch a bottle of his finest before he burns the place down.
I certainly won't spill it, but that doesn't stop the building and fire guys asking about spilling it. The way they are looking at this, is if a bottle falls and breaks, the whole place is going to go up like a roman candle.
I keep trying to tell them they should spend more time closing down all the bars in town, because of the safety hazards.
They weren't happy when I said that.
Also said I was happy they outlawed smoking in bars now, you know, on account of all the people blowing themselves up when having smoke and vodka tonic.
Also not thrilled when I said that either. I should probably keep my mouth shut.
Architect says hide behind the code and go with 1cfm for 1 sq foot, engineer tells me that there is no way I can get by with anyting but a $100k HVAC system. At this point I think the architect has got the most sensible approach.
@grim - we have to have a drink together when you get approved... I bought up cognac requiring open flame stills, smoking over a shot of whiskey, I told them if they had a desk with 'whiteout' in the drawer, they had flammables on premises ;-)
Grim, you can probably get by with ventilating the brewing room with an explosion proof explosion fan and draw your makeup air from the space adjacent to it. Install fire/smoke dampers controlled by fire alarms to close dampers. Bring but loads of makeup air into adjacent space. That will eliminate explosion proof a system.
Typically this type of ventilation is calculated in air changes per hour. So take the room dimensions X the height, that's the cubic footage. It's been a while since I have looked at this, but I would guess you are looking at 5 air changes per hour (ach) to a max of 10. So if your room is 10 X 10 and 10' tall you ha e 1,000 cubic feet. That times say 5 is 5,000 cubic feet per hour /60 is roughly 85 cubic feet per minute (cfm).
The explosion proof fan should be under $1,000 at the worst case. Don't know your location, but if you are roughly 1,000 so you won't need very much cooling to overcome that quantity of outside air. Otherwise explosion proof ac is huge bucks..
Sounds like a negative pressure room. If the brewing/distilling thing doesn't work out, you can always keep tuberculosis patients in there......
I don't work in imperial measurements, I need medication to do it and I have run out.
77000 ft3 = 2180m3.
Ethanol LEL = 3.3 %v/v
Ethanol UEL = 19 %v/v
LEL kg/m3@12DegC = 0.0595 kg = 59.5g per m3
UEL kg/m3@12DegC = 0.3425 kg = 342.5g per m3
Ltrs of ethanol to get to LEL for 2180m3 = 129.733
Ltrs of Ethanol to get to UEL for 2180m3 = 746.951
I think the best thing you can do is get ethanol LEL detectors placed strategically around the area.
You need to spill a whole lot booze to get to LEL considering these calculations are based on ethanol 100%abv. Adjust figures according to % you are using. eg if you have 40%abv then you have to spill more than double these figures to get to LEL or UEL.
LEL and UEL figures taken from Draeger website.
Hope this helps
@mickiboi - You are awesome!
One more thing, UEL means nothing really. Once you exceed the LEL your in the shit, remembering that LEL is the lowest point that combustion will take place. Above LEL the only thing that will be different before you reach UEL is the size of the bang. Thats why we have LEL detectors and not UEL detectors :))
Yeah, most LEL detectors alarm at 25% of LEL.
They do. I would be more concerned about a localized area explosion than a whole room one. If you spill 5 litres then somewhere in that surrounding area you will be at LEL. Detectors are your best investment.
First I am not a professional engineer, however I have done many facilities with explosive atmospheric conditions. Several companies produce detection monitors that can activate fan and or scrubbers. I use Honeywell products for many projects, the 310c controller with, or a stand alone E3Point detector by Honeywell. Honeywell E3Point info and the 301c main controller that can monitor many E3 Pint detectors. Flammability limit @ Wikipedia. I personally hose down any spill with water as soon as it happens. Please take in count of all other equipment and controllers, and components that are not explosion proof. Air fresh air makeup is important, however when outdoor temperatures are at 10 deg F as it is here in Maryland today it becomes costly and energy wheels are used to scrub the thermal energy from the air being exhausted and added to the incoming fresh air. I think the big picture is not to allow the vapors to reach the ignition point. The Honeywell controllers have a large assortment of modules for detecting CO, NO2, O2, H2, H2S, CH4, C3H8, electrochemical (for toxic gases) and catalytic bead (for combustible gases).
Any thoughts on this?
VOC Datalogger Ethanol Ammonia Smoke TEMP Humidity Test 32K Monitor Taiwan Made @ eBay
Thanks for the tip on the Honeywell system, I'll check it out. We were looking at the RKI Beacon system.
I know there are a bunch of ethanol detector shields/sensors for arduino boards as well. Whether that would satisfy a fire marshal is another story entirely however...
That detector probably won't comply with the code. It's upper limit 9999ppm which is 0.9999%. LEL is 3.3% but 25% is 0.825% or 8250ppm so it may possibly warn you. The detector is not UL listed and certainly doesn't look explosion proof. It may very well detect ethanol vapor but then possibly blow the crap out you after it has done so. Get a Draeger portable, expensive but works.
Now you're probably going to disagree with this next statement, I play poker with a fireman who is a fire investigator so I know it's not only right but very logical.
Hosing down spills does nothing. It will alleviate the risk of direct ignition of the ethanol liquid but it WILL NOT REMOVE THE RISK OF EXPLOSION. The amount of ethanol you have spilled will still remain the same in vapor form whether you put no water on it or empty a whole tote full on it. Depending on the temperature of the water you dump on it you could also make the situation far worse by increasing the evaporation rate.
Remember LEL IS ABOUT VAPOR CONTENT in the air not liquid quantity on the ground. Explosion risk is totally different from fire risk. Ventilation is the only answer when it comes to minimizing explosion risk with any vapor.
I would not be putting anything home made into a commercial environment. Get proper detection and control equipment if that's what they want.
RKI PS2 has a pretty low cost of entry for a fixed system, you can find it for just under $800, and RKI will calibrate it for whatever ethanol % you want when it goes out the door.
Here's a good primer:
Potential Explosion Hazards due to Evaporating Ethanol In Whisky Distilleries (PDF)
And thanks for letting us take over your thread!!
@Moonshine thank you kind sir
The UEL is important to know. You can exceed it without ignition and be figuratively "safe" on the high side. But in ventilating you could back down into the explosive range and cause ignition from a source that wasn't present before you exceeded the UEL.
We could call this split-off thread, Fun with Stoichiometry...
I'm more like I am now than I was before.
Correct @Kapea but when that 25% LEL alarm goes off you should be either trying to fix the problem or be 10 miles away. I would think that above 19%v/v UEL (190,000ppm) you would be pissed and passed out on alcohol vapour, figuratively on the "high side". Maybe someone from here can put 350ml of alcohol into a 1m3 box, climb inside and post us the results? No smoking in the box though.
Or sure, haul ass and leave it for the ERT to clean up. :))
I'm more like I am now than I was before.
I know it's been mentioned a few times but just because you are under the 25% LEL this does not meant you are under the safe exposure limits.
At my work site we have our LEL alarm set at 15%.
I can tell you what working in an area with 5%-7% LEL is like and I can tell you what 15% is like on occassion. It's not a comfortable place to be. Ventilation is your friend if you can't contain the source of the vapour.
We a have a great number of LEL meters and in one building in particular we've had to upgrade the ventilation system due to the EtOH vapour (VOC's) concentration exceeding the limits for a safe working environment.
I can't tell you the brand of the LEL meters off the top of my head but I'll check them out tomorrow and let you know.
Safe work exposure level in Australia is only 1880mg/m3 or1000ppm. But above 500 ppm it's recommended to use A VOC mask. So the safe work level is miles below even the 5-7% @TheMechWarrior is talking about. Seems there is more than explosive limits to consider, also have to think about exposure limits.
So there are two aspects we need to consider here. Ethanol vapors released during non-operating conditions, or operating conditions where distilling is not taking place. Second condition is potential ethanol vapors released during distillation operations.
I'll paraphrase an interesting comment in the Discus Fire Manual regarding Alcohol Vapors from a liquid source.
Once you exceed 18" from the liquid vapor source, you will likely be below 25% LEL, and once you exceed 5 feet, you will be below measurable limits. They don't list a temperature for this statement, but I'd expect it to be at 70F.
From a spill perspective, outline your operating area, draw a 5 foot line around that, treat that as classified.
From the second case above, a safe assumption for sizing is to assume that the entire ethanol content of your still boiler will be vaporized. So, 1000 liter still, 8% ethanol, 80 liters total ethanol. Assuming perfect mixing of air, and zero ventilation, 77,000 cubic feet, this should be equivalent to 62% LEL. Realistically, this would be an explosive environment because of the 1.6 vapor density, which means the concentration at ground level will likely be well over the LEL. Assuming the bottom half of the room, 11 feet, we'd be at 1.2x LEL, kaboom.
Agree, you still have the vapor to deal with, but you also have the vapor potential to deal with. I would imagine that even if your water was at ambient temperature, as was the alcohol, dilution would raise the open cup flash point and reduce the amount of vaporization from evaporation. Probably some benefit if your water happened to be colder. Hotter? Probably not a good idea.
Clearly this doesn't always work to your advantage though . For example, spill 50 liters of 95%. You just so happen to have a 15 liter bucket of water handy. You think to yourself, it would be a good idea to try to dilute that 50 liter spill with this 15 liter bucket. Well, no. Now you've make the spill area larger and it's just as hazardous.
There is a recommendation about the dilution volume required, which essentially says take it down to 20%.
((% alcohol before dil. / 20%) - 1) * vol. of alcoholSo 50 liters of 95% would require 187.5 liters to sufficiently dilute. You can even play a timing game with this and measure the volume of water you can get from your hose, lets say 18 liters a minute. You'd need to dilute for 11 minutes at full flow. Probably a worthwhile test since you aren't going to be trying to take a measurement on the floor.
Firemen may know how to put out fires, but 99% of them think that ethanol and gasoline are the in the same class... take what he says with a grain of salt... Ethanol is water miscible, gasoline is not and floats. Also ethanol is not considered flammable below 20%... that is specifically spelled out in the fire code... hell, one of you at your poker table probably has stronger than 20% in your glass and lights up a cigar, pipe, or cigarette......
also, on the detector not being explosion proof, why does it have to be? In an H3 occupancy, sure, but in F1-OH2, not required....
The problem is that blended fuels like E15 and E85 blur that line, especially E85, which is ethanol denatured with 15% gasoline. In addition, much of the literature on this is large scale spills and tank fires, which use techniques similar to other fuels. This runs contrary to a number of Discus recommendations. The most interesting of which is the statement about sprinkler density.
20% May not be flammable in water but in the air it's explosive, 2 different things. If you took 100ltrs at 20% which won't light and spilt it on the floor and only 10 ltrs becomes vapour, your are at the LEL for a 160m3 area, you have put 10ltrs of ethanol in the air and that's what we were talking about, explosive limits not flammable limits. What you have spilled has become less flammable but the air is now an explosive mixture. As a general rule if your light fixtures have to be explosion proof then every thing else electrical that enters the room should be as well. I don't know about the US so maybe I shouldn't have said anything about the detector but you couldn't use that thing here in Australia in a commercial environment.
If you have a water hose and spray with a shower type stream and not a jet, the air above the vapor will be impossible to ignite... also, if you spill 50 liters on flat ground with no drain, when you finally clean it up, you will realize the importance of drains.... if I spill 50 liters, 49 are going down the drain...
go get a few stainless bowl, put a cup of 95%, diesel, and gasoline in them and light them in an open area....
a lot of bad information is fueled by lies told to insurance companies... I have personal knowledge of a rented motorcycle shop being burned down ... the story is a pan of gas sitting on a motorcycle lift with a cup of gas in it somehow created vapors that made it to the gas water heater.... the truth was more like he set down his cigarette and it rolled down the lift next to the pan of gas.....
If we did not have videos of how stupid the guy in Moore, OK was, we would think that his accident could happen to us... I can't tell you an accident will not happen to me, but I can tell you that I am not going to have a propane burner,tank, and still boiler on a pallet in the air with a forklift and have essentially a dryer vent pipe taking my alcohol to the condenser with duct tape holding it together...