Topic: Propane Safety
Instructor: Al Cohoe
Propane is highly explosive, but properly handled it's extremely safe.
Properties of propane. It has no odor by itself. It's clear. An oderant is added, and that's the smell we're all familiar with. It's heavier than air, and thus displaces air. That's why propane detector is usually within a few inches of the floor. It has limits of flamability. 2.5% - 9.5% by volume mixed with air is where it's flammable. Thus when it first leaks out, it's an insufficient "mix" to be explosive. Propane itself is oderless. But an oderant is always added to help detect propane leaks. At .5% (by volume) you can begin to smell it -- that's 20% of the lower level of flamabiity. Oddly, women tend to detect the odor of propane before men. However, if you're careless and leave empty propane tank "open", moisture can get in. If the tank is not purged of moisture, it will reduce the efficiency of the oderant. Said otherwise, you'll now need more than .5% before you'll be able to detect it.
Propane gas detector, in addition to smoke detector, now standard in all RV units. It's always located close to the floor, since propane is heavier than air. [However this theory is being re-examined because propane travels with convection -- some tests have shown placing the detector at a higher point may in some cases be more effective.] Carbon monoxide detector (not universally found in RVs) is nearer ceiling, and detects improper combustion. Soot around propane appliances is a clear danger signal of imperfect combustion.
When you purchase it, it's in a liquid state. Tank gets filled to 80%. Allows for 20% expansion. When vaproized, it expands 270 to 1. Liquid propane "boils" at -44F. If surrounding area is colder than that, it stays in liquid form, and won't come out of tank. Not usually a problem w/propane. However, as a rule fill your tank in the same general locality as you're going to use it. Example to avoid: filling a tank in freezing temperatures in the northern states, and driving to Arizona: When you filled the tank it was filled to 80% capacity; but going to the heat of Arizona could cause the propane tank to become "overfilled".
Propane expands 1.5% for every 10 degree increase in temperature. That's why tanks are never filled beyond 80%. It's crucial to keep filled tanks so that escape valve is on top so that any "overfilled" volume will be expelled as a vapor, and not in its liquid form. This is why it's dangerous to paint propane tanks a dark color to "match your rig" -- it will heat up to higher temperatures and become "overfilled".
But sometimes it's mixed with butane, and not identified as other than propane. Coming home to northern states from AZ with a full tank of mostly butane -- which won't vaporize until it gets above 32F -- can cause a problem, since butane needs to be above feezing to vaporize. If it doesn't vaporize, your appliances won't work. If you fill up with Butane in Texas and drive home to Minnesota in winter months, you'll find none of your "propane" appliances will work.
Perfect combustion of propane yields water, carbon dioxide & heat. But often it's not perfect. If combustion is imperfect, a byproduct is carbon monoxide -- colorless, oderless, and deadly.
Cylinders & Tanks: Cylinders small disposables (like coleman) up to very large re-useables. If you refinish the outside of a cylinder yourself, use white or off-white color. Dark colors absorb heat, and propane liquid expands 1.5% for every 10 degrees (measured against temp at filling time). Plastic milk cartons make great travel containers for propane tanks when taking them in for refilling. The date on the tank should be w/in 12 years -- and if not, needs recertification. Usually cheaper to dispose of the old tank and purchase a new one. [Note: US is 12 years, Canada is 10 years.]
Recommend don't travel with fridge on. Fridge can retain cold for a full day's travel, so really not needed anyway. New tanks have "OPD", overflow protection device (triangular handle plus outside label). These not only have spit valve, but something that cuts off filling at 80%. Quick connect "QC-1" valve. No more messing around with wrenches. The law now requires OPD valves, and they offer complete protection agains inadvertent overfill.
Propane cyls & tanks require purging before use, to ensure getting rid of air/moisture. If it's exposed to atmosphere (empty with valve open). Moisture effects pilot lights and other probs. Can save cost of purging. Put anhydrous methanol into container to eat water, and bleed off several times. Then charge w/15# vapor.
Two ways to fill cylinders. By volume -- open set screw, will bleed off when fops out at 80%. In US they fill by volume, and won't touch a tank w/out it. Also, can fill by weight. Collar shows tear weight -- which is dry weight. Filling by weight is safer than filling by volume, since the volume would automatically be adjusted to current temperature. Example -- if you fill by weight at below zero temps, you may only be filling to 60% of capacity -- which is where it should be if you're heading into hot temperatures and need to factor in expansion.
Hoses & Lines. Propane goes to regulator via hoses. They should be flexible, and state on it that it's for LP gas and good to 350#. Look for the label of UL or CGA approval. Some have "O" rings. Check them for cracking. Check hoses for dry cracking as well.
Don't use teflon tape or lubricant on threads. It may cause an improper seal, and result in propane leaks.
Barbeque "single stage" regulators are illegal on RVs. Two stage regulators provide margin of safety. 100# tank pressure goes down to 10-13#; second stage can work much more easily with the low pressure it receives from first stage. Vents must be pointed down +/- 45 degrees. Autochangeover lets you open both tanks, point to the primary tank which will be used up first. When it runs dry (propane will now be automatically drawn from the second tank) turn it off, switch pointer to second tank, and you're ready to fill up the empty one.
Most furnaces are rated in BTUs. There are two -- an input rating and the other the furnace output rating. This compares how much fuel you use with how much heat is produced. The efficiency is the ratio of input to output. 85% would be "good" efficiency.
[90,000 BTUs per gallons of propane. Fridge uses very little -- about 2,000 per hour. Standard stove burner about 5,000 per hour.]
Bottom line is propane needs to be treated with respect -- not terrified of it. Find a certified technician and get a propane leak test done on your RV at least annually. This should be a half hour labor. In British Columbia every sale of a used RV -- even in a private sale, requires "gas re-certification".