You and Propane
It seems like most of the most of the hazards and warnings associated with ballooning never change. We just need to be reminded of them. However, what does change is the conditions in which these hazards present themselves. Our contact with propane is a great example.
The basics attributes of propane gas and its handling are as follows:
It is combustible when it is somewhere between 2% and 9% in concentration. Does this information by itself offer a formula for safely handling propane gas? Not really. The only thing we can determine once unburned liquid propane has left the confines of a tank or hose is that it will enter that combustible range sometime and somewhere before it dilutes into the air. That much is assured.
It is heavier than air. This means it will tend to sink relative to calm surroundings. Is this critical information? It is without a doubt. For any pilots who have ever stored their equipment in a garage or building and heated the tanks or the building, the risk is obvious. If the tank pressure relief valve opens for some reason, the out flowing gas will creep in all directions along the floor until it reaches an ignition source or it finally dissipates.
Even without a burning pilot light in the building, while this gas is dissipating, someone walking in the facility can ignite the gas inadvertently by stepping on, bumping against any type of ignition source. For those who don’t know, when a tank “pops off”, it doesn’t quickly release a little gas and pressure and then shut down. It blows liquid out for what seems like hours (probably 10 minutes) and there’s nothing you can do about it except quickly plot your escape route if you are indoors.
It expands 275 times its volume when going from a liquid to a vapor. If propane could lose this property, it would cut our risk factor significantly as balloonists. Since we must use propane in its liquid state to provide our power needs (it’s actually gas at the very end), we are constantly faced with leak expansion factor that can easily go unnoticed and can’t readily be diverted from potential ignition sources. Just imagine, 1 cubic inch of liquid propane coming out of a fuel hose translates into about 275 cubic inches of combustible gas.
This amount of gas will quickly spread to the pilot light in spite of its propensity to follow gravity. Once lit, it’s all over. If a liquid or gas leak occurs inside of a poorly ventilated structure, what was once a diluted gas, out of its combustible range, has an opportunity to collect along the floor into a potent concentration looking for an ignition source.
As a student pilot, hopefully the properties and safe operating procedures of propane were covered in depth. The first thing you probably learned is to make sure no one is smoking in the vicinity of propane refueling. You probably didn’t learn much at your refueling station as those guys tend to know less than anyone about propane. In any case, it’s likely that you fell into a routine at your regular refueling station and since you haven’t blown anything up yet, you are doing everything right.
The next level of enlightenment likely came during the refueling process at a balloon event. Depending on the diligence of the safety officer, you should have been instructed (at a minimum) on the following protocol;
- Pilot and 1 crew only allowed in the refueling zone
- Take all strikers out of the basket or disable them at a minimum. Take out anything that could produce a static charge. Don’t wear a nylon jacket.
- Don’t start bleeding tanks until you are in the refueling zone
- Turn off engine as soon as you reach your spot in the refueling zone
- Once in the refueling zone, don’t refuel from inside the basket
- Pull the basket out from any vehicle that could collect gas inside during the refueling process (van etc), or insure good flow through ventilation.
Make sure all tank valves are off and hoses disconnected before leaving the area.
After your first event, you may have added many of these safeguards to your refueling regimen. This is all good. Unfortunately, sometimes this regimen becomes habit and the situational awareness fades leaving you at risk for subtle changes that may occur during the refueling process.
Recently, a propane accident occurred during refueling at a major balloon event. The situation involved a motor home type chase vehicle with the balloon storage in the rear. During refueling, the door to the living area from the rear storage deck was left open, allowing propane gas to enter and eventually come in contact with the pilot light from the refrigerator. The ensuing explosion caused some serious injuries and damage.
I’m sure the parties involved had refueled safely from this vehicle for many years. Maybe they had even refueled when the back door was open but an open front door had allowed enough ventilation to keep the gas under the explosive limits or the flow direction was out of the rear. Maybe they were used to refueling their personal balloons out of a truck and didn’t consider the different situation and its implications. The point here is that refueling can easily become a routine and habitual in nature. This is dangerous. It is essential that you evaluate the parameters of every refueling process before proceeding even if it is at home at your regular propane outlet.
Ref past issue on emergency procedures.
I was reminded by an astute instructor that “burning through the mouth” may not always be the best solution when in an uncontrolled descent. The possibility exists that the basket could sever from the envelope if all of the critical load tapes are burned through. Obviously this would be a tough call.
Propane is given an additive for smell (Methanethiol, or Methyl Mercaptan) since it’s invisible in the air. This helps determine if there is a leak sometimes but once a leak occurs in a basket in flight for instance, we are in big trouble.