In North America, at least since 1960, there have been known to have a car tire repair aerosol, which is a very useful aerosol products. They can quickly put a large pot of aerosol content into the air leakage and discharge pressure to change a flat tire. Aerosol material liquid containing emulsion type ethylene polymers, antifreeze, modified agent, corrosion inhibitor, bactericide and assist the vinylic sealing leak of special material. At the same time, aerosol propellant to re inflate tires. The aerosol with CFC-12 or CFC-12/114 (80:20) as a propellant, propellant amount accounted for about 45% ~ 55% of the prescription, to ensure that there is enough air into the tire to re inflate. Even for large tires, in cold weather and some propellant gas will in loophole blocked before the closure the escape hole is also true, that is to say, the amount of propellant should can meet a variety of special circumstances of inflating needs. After 1978, USA banned the use of CFCs for aerosol, forcing the industry to replace with hydrocarbon propellant.
Hydrocarbon ejection agent only accounts for about all formulations of 20% to 25%, because the molecular weight of the hydrocarbon is much lighter, so the amount enough to produce and higher proportion (%) of CFCs ejection agent with the same volume of gas. The formula makers realize that there are some tyres that may be extremely cold at the -35~-20, which requires the aerosol to work under such a severe condition. So, the propellant must have a relatively high pressure. The mixture of propane and ISO has been used in the past, and propane is about 30.5%~37% of the total amount of, which is about 0.41~0.45MPa (21). Even under very cold conditions, there is still plenty of pressure in the aerosol can quickly put the product into the tire and fill it with a tire.
Most worried about is the product must be covered by the leak. For example, if the leak near the top of the tire, and products from close to the bottom of the injection, so only the propellant vapor will contact the leak and through here continue to leak. Therefore, the tire must be slow to at least a circle, even if it is a flat tire. The occasional leakage will be caused by a steel ring, and tubeless tires may be caused by the seal between the rim and tire burst. Under normal circumstances, aerosol products may not contact these areas, repair tyre will fail.
Marketers had to worry about the hydrocarbon propellant mixture combustion, they provide clear label instructions for use, guiding consumers how to safely from the fetal exclude flammable gas, guide the driver to the first organic repair industry and trade of car repair stations, mechanic from the car unloading tire and unscrew the tire valve spring the potentially combustible gas exhaust, tire completely deflated, and then use compressed air to fetal pressurized to approximately 0.2 MPa again deflated pressure relief. After more than two times the pressure - pressure - release of residual hydrocarbon in the tire will be lower than the explosion limit (LEL), so it will not burn.
Here is an example of the outcome of the situation. The first two assumptions, the volume in hypothesis of tyre is 50L, and injected 0.45MPa propellant mixture 100g. By listed in table, in 21 DEG C and 101.3 kPa absolute pressure, 1 g of the mixture to form fibers are pure gas, the amount of 100g will produce gas 46.5L, if the tire air pressure are not, adding hydrocarbon ejection agent in the tire pressure will be:
101.325kPa x (46.5/50.5) =94.3kPa (or 0.0943MPa)
This is equivalent to absolute pressure: 0.195MPa (467mmHg 760+707=1)
The first operation removable mechanic all the tire pressure, the pressure from 0.195MPa to 0.1MPa pressure pressure. In this process, the original 100g hydrocarbon propellant with volume fraction is 48.2% is discharged into the air, in the tire still remains 51.8% of the original mixed ejection agent and 48.2% air.
The second operation is to use compressed air to the tire pressure to 0.2MPa, so that the absolute pressure of the tire is equivalent to about 0.302MPa. The combustible in the tire is diluted to the original concentration (1/2.98) or 33.6%, and the result is contained in the mixture containing 14.3% propylene and 85.7% air.
The tire pressure once again, and many of the remaining hydrocarbon gases. The air pressure is still pressurized to 0.2MPa, and the gas is then diluted to 33.6%. The composition of the gas in the tire is 4.80% C and 95.2% air.
Third times the tire is the last discharge pressure, pressure, can be gas and then diluted to the previous 33.6%. At this time, the composition of the gas inside the tire is 1.61% C and 98.39% air. Due to the low limit of explosion of propylene (LEL) is 1.93%, the gas in the tire contains 1.61% propane.
By this time, the tire from the wheel, clean and finally used plugging or supplement method to repair, the market's suggested by the permanent repair methods.
If the user does not have a permanent repair, is known as the temporary sealing of the aerosol can continue to travel thousands of kilometers. If the tire is leaking again, users may forget to tell garage mechanic fetal full potential flammable (explosive) mixture of gases. Mechanic with steel pry hard tyre peeling off from the steel ring, if the spark may ignite the gas in the tire, the tire
The gas in the confined space has a terrible thermal expansion, the pressure can reach 1~2MPa, and the tyre may blow up. Old tires, rubber tire, had no radiation steel ribbon and larger than the new tire tire tire more easily influenced by blasting. In this case, the mechanic is often a serious injury and even death.
Another problem and welding thin cracks found on the tire rims on. It violates the welding principle, trying to seal cracks in pressure vessels, melting in steel