The Washington Post ran an article today detailing the 101st Airborne Division’s preparations for a possible war with Iraq (article here). One of the things they’re doing is shrink-wrapping copters for transit and sealing them with 3,000 degree heat guns (see the third paragraph of the article).
Huh?!? 3,000 degrees! That can’t be right, can it? Surely someone was funning the reporter, or he added an extra zero to the figure by mistake. At that temperature, the helicopter would be molten slag, wouldn’t it? How could plastic survive that? And what about the operator – how does one wield a 3,000 heat gun without becoming charcoal?
Here is a table of melting points for some metals. Suffice it to say that not many metals are still solid at that temperature. Even if the copter were made entirely of titanium (unlikely, though I’m sure that exotic metal is utilized somewhere in military copters), 3,000 degrees comes within 200 degrees of melting it. That’s cutting it a little close for comfort.
So, does the military really use 3,000 degree heat guns to seal the shrink wrap around their copters?
Sure, why not? The high temperature merely ensures that the job can get done quickly. No part of the shrink wrap or the 'copter is exposed to that temperature for very long. A mass takes time to heat up. Just because the air coming out of the heat gun is at 3,000 degrees, doesn’t meant that anything exposed to it will instantly heat to that temperature.
Part of my job is heat shrink wrapping military vehicles.
The heat gun that we use is hooked up to a regular propane tank. The gun that we use emits a flame about 2 feet long and about 6 inches wide. It has a trigger that sends a spark which lights the flame.
We use heat shrink wrapping that is in rolls about 8 feet wide, folded twice. So that means it is 32 feet wide. The way to heat shrink is to wrap it loosely on the object being treated, and tape down the loose ends. Then we start applying heat with the gun, taking care not to get too close, which will burn holes in the heat shrinking. The thing to do is to heat it up and then move to another part. When it heats up, it gets looser, and then when it cools a bit, it tightens right up. It takes a great bit of practice to get it right…
Hermann Cheruscan, thanks for chiming in. I was hoping to hear from a voice of experience. Given that the equipment you use is powered by a propane tank, am I safe in assuming that you’re working with a few hundred degrees, rather than a few thousand?
Fear Itself, thanks for the link. I, too, am leaning toward an error, though I haven’t seen any correction printed in the Post.
Mangetout, your comment about an oxyacetylene torch spurred me to do a little research; turns out they burn as hot as 6,300 F! So in an entirely unrelated question, what is the torch nozzle made of that it can withstand that heat?
The flame doesn’t actually touch the tip, depending on the pressure of the gas, it can be anywhere from a half centimeter away to more than an inch. And the flame is being constantly blown away from the tip.
Good point, NurseCarmen, that due to the gas pressure, the flame isn’t actually touching the metal. But still, even with the actual flame an inch away, that’s still gotta be pretty damn hot. Maybe not the full 6,300 degrees, but how much could the temperature possibly fall off in an inch or so?
Going by your logic, the source to heat up that flowing gas to 3000 deg. will have to be at a substantially high temperature almost like a 1000 degress more. It may be feasible to use to some exotic material to do that - but this reasoning fails to tell what purpose it may serve.
Doesn’t cool off a lot… if you shut off your torch, remove your goggles and gloves, take a swig of Pepsi, then sit down to take a break, the torch tip will burn right through all seven layers of skin right quick if you put your hand down on it.