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-   -   Home made PVC pneumatic cylinders? anyone with experience in this? (http://www.hauntforum.com/showthread.php?t=29657)

Brad Green 11-20-2011 08:50 PM

Waaaay back 'in the day' I used home-made pvc cylinders, and while I never had one rupture, let alone go boom, they were an absolute pain in the ass to use and would fail on a regular basis. You are basically working with 'seals' (rubber washers) that never seal properly, tubing i.d.'s that are no where near uniform, and a whole host of jack-legged parts that really don't fit. Even if you completely discount any possible safety issues, these things just aren't worth all the inherit problems that come with them. Just watch Ebay closely and you'll find plenty of genuine cylinders at a great price.

mroct31 11-20-2011 09:31 PM

Quote:

Originally Posted by corey872 (Post 594678)
If you look at the specs for schedule 40 PVC, even 3" dia. has a working pressure of 260psi - and it goes up from there as you go into smaller diameters. .

Not sure about the effects but PVC is rated for liquid pressure not air pressure.
There are plenty of stories online about PVC failing when used with air, maybe not the grenade problem but problems none the less. Why even chance it, hurt yourself that's one thing, hurting a guest...well no more happy Halloweens for you!:jol:

gadget-evilusions 11-21-2011 12:09 PM

http://www.osha.gov/dts/hib/hib_data/hib19880520.html

The reason you should not use PVC pipe either in distribution or cylinders and spud guns is that it will eventually explode, and when it does, people can die. This is documented in the link to an article on the OSHA (Occupational Safety and Health Administration) website.

At my job someone decided it was a good idea to do air distribution thru PVC pipe that was rated at over 300 psi. After only about 1 year the 125 psi air in the system continuously pressurizing and depressurizing fatigued a piece of the system into exploding and hitting ME in the head with shrapnel. These are the same conditions that a cylinder or spud gun will see.

I know everyone wants cheap, but safety should never be sacrificed. Sorry to be negative, but since it's actually happened to be, I believe the urban legends.

ouizul1 11-21-2011 05:18 PM

Quote:

Originally Posted by madmax (Post 594907)
I started to leave this alone because....

Glad you didn't. That's one of the best unbiased responses I've seen on the subject.

I did some searching on the subject and also found that the documented catastrophic failures were in shop supply lines...most of those occurring when someone or something struck the pipe, causing it to rupture and sending shards of sharpness flying about. Searching through a bunch of OSHA and manufacturer's stuff...yes, use of PVC pipe for compressed air without some type of adequate containment layer around the piping is definitely a no-no.

So, when it comes to compressed air and PVC, it seems that the danger lays not in that something WILL go wrong...but rather what happens WHEN something does go wrong.

But hey...it's a free country, and the casinos are always open. :cheeseton:

bert1913 11-23-2011 12:15 AM

i did a internet search for pvc cylinders blowing up and found nothing. if you keep the pressure at or below 30 psi i see no problems with using them.

hauntedyards 11-23-2011 08:11 AM

All PVC pipes using compressed air are by default PVC cylinders.

http://torque1st.clubfte.com/OSHA_PVC_Pipe.htm

"The main problem with using PVC pipe and fittings for compressed gas is not that it
spontaneously explodes but that PVC is a brittle material that can be broken or
shattered with external force unless properly protected. Compressed gasses can be
best described as being analogous to a coiled spring. When a PVC pipe or fitting
fails when under stress from compressed gas it literally explodes like a bomb,
sending shards of plastic flying several feet in all directions. Liquids, on the
other hand, being compressed by only 1/10th of 1% contain very little stored energy.
When pressurized systems with liquids fail, the energy is dissipated very quickly,
thereby creating a much lower potential for hazard.

Colonial Engineering does not recommend the use of PVC plastic pipe fittings in
compressed gas service."

mroct31 11-23-2011 12:19 PM

Quote:

Originally Posted by bert1913 (Post 595212)
i did a internet search for pvc cylinders blowing up and found nothing. if you keep the pressure at or below 30 psi i see no problems with using them.

No problem using PVC for air? Really?

Here was a great explanation I found:

"Think of it this way. Take a scuba tank, fill it with water and apply pressure to the tank by hooking a pipe to a water tower next door. It the tank springs a leak, water will come out but note that water cannot be compressed so you only have the volume of water coming out that the pipe will flow.

Take that same tank, fill it with 80 cubic feet of air compressed to fit the tank (air is compressible) and hook it to a nice compressed air supply. If the tank ruptures now, the air will expand to its normal volume as it escapes. This allows the air to expand in volume from whatever pressure you have (example: 150 psi) to normal air pressure (14.7 psi). In this example, the air would expand to over 10 times its compressed volume state.

That is the difference in water and air. One will create a leak that will spray a lot of water and the other can explode rather spectacularly at times...."

Also here is a picture since you didn't find it:
http://www.monroefiredept.com/Incide...?IncidentID=56

There are some good stories here as well: http://www.garagejournal.com/forum/s...ad.php?t=60109

I like this post as well:

http://www.osha.gov/dts/hib/hib_data/hib19880520.html

Methinks that any corporation, school or individual that has a failure is reluctant to photograph the evidence of going against OSHA recommendations! A quick browse of the internet does turn up dozens of failures. Some nuts still defend PVC, saying things like, "it's only broken twice in 10 years"

Hey, PVC might work great but it will fail at some point and why work with material that is known to have problems when you can work with materials that are well tested and safe? Seems like a no-brainer but we all know someone with no brains! As a matter of fact I'm putting him out next year in my haunt!

yyzmec 11-29-2011 05:08 PM

just wondering what everyones opinion is on modified screen door closers is?

halstaff 11-29-2011 05:26 PM

Quote:

Originally Posted by yyzmec (Post 596448)
just wondering what everyones opinion is on modified screen door closers is?

I feel the small increase in price of using a proper cylinder that's already built is worth it. I don't have time when Halloween comes to worry about a possible failure in a hacked cylinder. I'll save my hack time for something else.

BioHazardCustoms 11-29-2011 05:58 PM

+1 to halstaff. The cost of actual cylinders is not that much different than a hack job. I'd much prefer to use my hack time somewhere that isn't a potential safety hazard.


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