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Old 02-20-2008, 02:00 PM
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Originally Posted by scrimshaw
The 'theory' that Ni is more stable for a change in temp. is not true. Even the Ni companies don't say that. This is the first line of the paragraph that I got from their web site.

'Fundamentally, air, oxygen and nitrogen will all behave exactly the same, in terms of just how much pressure will change for each 10 degrees of temperature change.'

If you can remember anything about your old chemistry class this is one of the 'Gas Laws' which basically says all gases or mixture of gases expand/contract the same amount. (I had to look it up!!).

But the fact that Ni carries no water is the stated reason behind it's use.

nitrogen is dry; it has no moisture to contribute extra pressure changes with temperature.
I know at Poli-Form we had an Instafoam 500 foam gun that shot 2 part urethane foam for packaging ..The system required that a pair of 15 gallon tanks full of part a and part b foam be pressurized with nitrogen instead of shop air. The pressures were well within the range of any shop compressor.

.Using Ni from a 220 CF cylinder was mandatory as the chemicals that made up the foam would react with any amount of water (water was readily aabsorbed into the material as well), and make the mixing ratios at the head of the gun all weird. In part due to the water, and also the fact that each hose had a nichrome wire running through it to preheat the any water in the lines there would react unfavorably as well.

For me, this is all academic. I won't put Ni in tires, or spray any paint with it..But the theory and application intrigues me.

Later, mikey
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