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PVC and cold temps
Posted: Wed Jan 28, 2009 12:59 am
by Daltonultra
OK, I accept the fact that cold temperatures do affect the shock-resistance of PVC, but does anyone have any data on temperature and burst pressures? I can't seem to find anything beyond the usual working temp ratings.
Posted: Wed Jan 28, 2009 1:01 am
by trigun
bump, agreed greatly i couldn't either.
Posted: Wed Jan 28, 2009 1:07 am
by frankrede
Cold temperature will make the cannon more brittle,
IIRC, the pressure rating rises.
Posted: Wed Jan 28, 2009 1:08 am
by trigun
wouldn't it lower it
if it does raise it can someone explain
Posted: Wed Jan 28, 2009 1:21 am
by jook13
No, he meant the pressure rating will decrease ( I think he did...). I havent heard any concrete data on the subject, but I like to use commen sense. If the cold is making you nervous, wait till its warmer. Build a copper cannon, the temperature resistance of copper is impressive.
Posted: Wed Jan 28, 2009 2:39 am
by Ragnarok
jook13 wrote:No, he meant the pressure rating will decrease ( I think he did...)
You're mixing up "rating" and "safe working pressure" - Rating is what the pipe has been nominally certified to. Safe working pressure is what it is appropriately safe to use it at.
Rating tends not to change - there are some companies that offer pipe with ratings for different temperatures, but most don't (an exception is listed below).
In contrast to what you believe, PVC actually gets stronger as it is colder - to a degree, anyway. However, it is also far more brittle and impact resistant.
The reason it is ill advised to use PVC at colder temperatures is that the risk of it exploding in spectacular fashion at knocks or drops increases, as does the energy that would be released in those events.
The best I can offer off the top of my head is this link, which gives an idea of rating reduction as temperature increases, unfortunately though, it's data is lacking at the low end, and it should not be considered to be a mark of failure pressures:
http://www.pipestock.com/PVC-Specifications.php (Third table down)
These links might also be useful, but I'm a bit incoherent at the moment, so I only skimmed them:
1 2 3 4 5
Some appear to refer to higher temperatures rather than lower, and some to slightly different circumstances, but they might have snippets of useful info in them.
Build a copper cannon, the temperature resistance of copper is impressive.
Indeed. If it's not so hot or cold that you're able to use your cannon, it's safe.