by Tom Hamilton
Balloon events have all but disappeared from the calendar for the next several months. After Balloon Fiesta there are just a few more rallies, many revolved around Halloweenfun events with wild costumes. The leaves have turned beautiful colors and fallen to the ground. Snow is covering the ground in some place, rain in others.
Whether you and your balloon hibernate for the winter or venture outdoors to enjoy those holiday season greeting card come to life flights, below are some helpful hints to make life more enjoyable.
Winter flying
Cold is the defining element of winter. Propane pressure is a function of temperature, as the temperature becomes colder you will have less pressure in fuel tanks. Every balloon manufacturer will specific in their flight manual what the minimum fuel pressure is for safe flight.
When it becomes cold enough to lower the pressure below any level that you fill uncomfortable with how do you raise it back up to an acceptable standard?
Today the two most common, not to mention safe and effective, methods for raising the pressure in propane tanks are heat tapes wrapped around the tank and nitrogen injected into the tank. Both are effective. Both have their advantages and disadvantages. Below is a discussion of each with their relative pros and cons.
Heat tapes were designed to prevent freezing of water pipes. Generally these tapes have a thermostatic device to prevent them from over heating at around 40·F. A temperature that is too low to be effective for propane cylinders used in a balloon. You can remove the thermostatic control, however you remove a fail-safe feature, which can allow the tank to over heat if the pressure is not monitored. The tapes can either be used directly on the tank or in a casing such as a padded tank jacket.
Disadvantages exist with heat tapes that are used directly contacting the tank. Because they were designed for use with water pipes and thermostatically controlled they were not designed for the intense heat use associated with heating a propane cylinder to 70·F. The protective shielding of the wire can become weakened, causing it to fray. This creates the possibility of an arc-through of the heat tape insulation to the fuel tank, causing a weak point in the cylinder. One balloon manufacturer conducting an annual inspection discovered such a situation. When the nick created by the arc was measured, they found that it had penetrated two-thirds of the depth of the tank wall. If it had completely penetrated the tank wall a fire and resulting explosion would have made a mess. With heat tapes there is also the ever present danger of an electrical spark near a possibly leaking tank valve or other source.
The heat tapes cannot have a bend or kink in them. If such a condition exists the heat tape will short at the bend and eventually cause a fire. A repair station last year discovered that there had been an internal fire inside of a tank jacket. The tank jacket contained a heat tape which had been bent in a zig-zag pattern.
With heat tapes you must monitor the tank pressure to insure that they are working correctly. And once they are working nothing can guarantee they will continue to work.
Still, the heated tank covers offer a superior performance over just the tape itself. Several reputable companies such as Stumpf Balloons in Providence, Rhode Island, offer them for sale.
Several balloonists are using a different method to heat their tanks. They have installed between the tank and a padded tank cover a waterbed heater. The heater has a thermostat that allows them to regulate the temperature to what ever level they want.
For all these problems, padded heated tank covers do have their advantages. A set will probably cost you less than a nitrogen system. They are portable and serve the double duty of protecting you from the tank.
But, more importantly they not only raise the pressure of the fuel, they warm the fuel. So what you ask? Remember in the article on preparing for winter there was the discussion of "O" ring leaks? Those pesky little leaks are caused by various component parts contracting at different rates. Most propane systems are designed to handle temperatures down to 40·F. (about 70 psi). If you are running cold fuel through your fitting there is the potential for a leak to develop. If you have warmed the fuel it will eliminate this problem.
Nitrogen pressurization has been used in Europe since the late 1970s, and very successfully. In the late 1980s a number of balloonists in this country started using it, particularly in Colorado. Nitrogen is an inert gas and acts as an artificial pressurant in propane tanks.
By using nitrogen you eliminate the problems addressed above with heat tapes. A fuel cylinder, pressurized with nitrogen, then used to a small percentage of its total volume, will continue to have a final total pressure much greater than that of the propane's vapor pressure alone.
Using nitrogen is convenient, it can be applied a few moments before inflation in the morning and you can repressurize for an afternoon flight. The process takes only a few minutes.
This might sound like an ideal system but there are disadvantages. It takes special equipment. In fact all parties contacted by Balloon Life stressed that it is extremely important that the proper equipment, procedures and storage techniques be used when handling nitrogen and nitrogen pressurized fuel tanks. To properly outfit a system with the necessary gauges and systems will cost around $200. Add to that a monthly rental fee for the nitrogen bottle that is holding your supply ($5-10/month). Before investing in and using a nitrogen system contact your balloon manufacturer to get their recommendations. Not all approve the use of nitrogen in their system.
Nitrogen is not recommended for tanks with vapor withdrawal for the pilot light. The nitrogen rests in the top of the tank where your propane vapor is. The nitrogen reduces the reliably and operating efficiency of the pilot light. As the temperature decreases and the proportional amount of nitrogen increases in the vapor, the volume of propane vapor reaching the combustion area (pilot light) decreases. Should you pressurize the vapor withdrawal tank, the pilot light might work for a while and then go out. You can agitate the tank (shake it thus bringing the two gases back to equilibrium) and relight the pilot light. Since you never know exactly when you need fire power or when the pilot light might fail, pressurization of the tank with vapor withdrawal is not recommended.
While tank pressure increased by nitrogen will remain relatively high there is a downside. Once the amount of fuel drops below 25 percent the pressure in the tank will drop dramatically. The pressure can be raised by shaking the tank. Its the same principle that takes place when you shake a can of soda. When you pressurize a tank with nitrogen, 60-80 percent goes into solution with the propane, and the remainder stays with the liquid in vapor state, giving you the pressure increase. When you shake it, the pressure will go up because some comes out of solution.
The cold will also effect several equipment components. Despite newly designed burners that often don't use "O" rings, there are still a number of you out there with "O" rings and each is a potential leak waiting to happen. O-ring leaks are caused by the different rates of contraction of the metal housing and the rubber O-rings in the blast valve. Generally these will disappear as the valve is actuated and thereby warmed. If O-ring leaks were a problem last year, you will likely see them again this year. Depending on the age of your system, it might be wise to have the blast valve serviced by your repair station at the start of the season and the O-rings checked and replaced if needed.
Winter is also a good time to think about adding methanol to your tanks to protect against water contamination. Many authorities feel that the potential for internal tank condensation is greater in the winter due to the great range of heating and cooling from heat tapes and vaporization cool down during flight.
Of course the colder temperatures will also have an effect on the performance of your balloon and the burner. Remember earlier when we said that the cold will cause low vaporization? When you first open the blast valve and run propane through the cold pre-heat coils the fuel will not vaporize and you will be burning liquid propane. You can recognize when this happens because liquid propane will burn as a yellow fire ball rather than the thin blue flame that you are used to seeing. Once the coils warm, the fuel becomes better vaporized and the burner more efficient.
Why is that important? Well that yellow fireball can result in a "flame thrower effect" completely filling the mouth of the balloon for the unsuspecting pilot ready to start a hot inflation. Both crew members holding open the skirt and/or throat of the envelope itself could be burned!
Two things you can do to minimize this danger. First, test your burner and warm the coils prior to laying the basket over and connecting the cables. Second, make your first inflation burns short, test burns to again warm the coils for best performance.
When landing, remember that the ground is probably frozen and it will be like landing on concrete. You may want to consider padding the basket floor to help absorb impact. Keep in mind that any stubble left standing in a field may also be frozen and can damage the envelope or possibly injure a passenger. Whenever possible, try to land as close as possible to the recovery access and if separated from your crew, land near a house, shed or natural outcropping where you and your passengers can seek shelter from the elements if need be.
Winter Storage
For many of Mother Nature's creatures this is a time for hibernation, for staying inside the den where it is warm, where one can watch the football playoffs, bowl games and the Super Bowl, not to mention the start of basketball season. For many winter is also a time of hibernation for the balloon as the flying season comes to an end. Here in the Pacific Northwet (that isn't a typo) the rain, grey clouds, and wind will be a fact of life until late Spring. Here are some tips from the experts on how best to store your equipment.
Keep the tanks separate from the balloon. The best place to store them would be in a shed away from any possible ignition source.
The basket should be raised up on blocks, 2x4's would make a good platform. By raising the basket it will allow the air to circulate and help to prevent dry rot.
Cover the basket and cap the fuel hoses. Store the burner in sack if one is available in a dry place.
The envelope also needs to be stored in a dry place and away from items that if spilled could harm it, such as solvents, gasoline and chemicals. Raise the envelope bag off the floor, used pallets make an excellent storage platform. You want air to be able to circulate around the bag.
Since they occupy a small amount of space, bring your instruments inside the house and store them in a safe, dry space.
Your inflator fan should be emptied of gas and run dry. If you have a wooden prop be sure that it is in a horizontal position (this prevents fluids in the wood from settling to one end and causing an out of balance vibration).
Coat the metal surfaces of the fan with a light coat of oil to guard against rust.
For more details on preparing for winter flight and chasing see Balloon Life's special report on Cold Weather Preparation in the December 1996 issue or visit our web site at http://balloonlife.com/ to read the articles. Have a safe winter.