Quote:
Originally Posted by math311
The seniors that built this used PVC pressure rated for 250 PSI, and we only plan on doing 125-150 PSI, so would that make PVC safe to use?
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No -- PVC is rated for water, not air.
The (most important) difference is that, because water is practically incompressible, a small crack will turn into a leak. Air will cause the PVC to shatter entirely, creating a large pressure wave (permanent hearing loss) and large quantities of high-velocity shrapnel.
Also, I'm not sure if this is true or not, but I recall reading that the different type of loads experienced by storing air (particularly when all the air is released at once, as is done in a T-shirt launcher) can cause PVC to fail much more quickly (and randomly) as it does with water (even if you're only running at 10 PSI).
If you don't have metal tanks, they can be pretty expensive to buy new. We acquired our tanks from local medical-supply businesses. They may have tanks around that are too old to be useful or are being phased out -- since they operate them at 2000 PSI (this can vary -- I'm using the figures for Lincare), they have to be a lot more careful than us with regards to discontinuing use of old tanks. It can be hit-and-miss, though, because they'll occasionally have the tanks they've collected recycled.
Thanks for considering our safety concerns, and good luck constructing your launcher.