blow off valve

[the_original_damo]

i under stand that a blow off valve pops out when itreaches a certain pressure but i have never seen one and wanted to no where the air goes does it come out the sides of the top of it? and also would there be enough power out of one of them to push a bb out of a barrel or even a paintball?
thankyou to everyone who posts back

[spudshot]

you can get them in the air compressor section of just about any hardware stores, the air comes out the ports on the sides when the top is pushed up by pressure. i was thinking of experimenting with one as a bb gun component, i just never got around to it

[pyromanic13]

ya but it open just enogh to let the air out its not a sudden jerk up that stays up like I think you think it is

[The High Plainsman]

It would be enough pressure, but the ones i have used stay open long after the pressure drops below what is required to open it (mine opened at 130 psi and closed at 45) unless you reset it by covering the holes to slow the airflow enough to allow the spring to reset the plunger.

[Hatheg-Kla]

I was looking at those as an alternitave to using a blow gun to actuate a sprinkler valve. you guys think they would release ari fast enough?

[Rambo]

Can I brake a ball valve by too much preshure?

[CS]

No, unless you expose to some serious pressure. Generally a ball valve used in a spudding application isnt the concern, because the piping your using will burst before your valve ever does.

[The High Plainsman]

I was looking at those as an alternitave to using a blow gun to actuate a sprinkler valve. you guys think they would release ari fast enough?

When I used it last, i had a 4" pvc pipe that was about 4 feet long, the blow off valve emptied it from 125 psi or so to 40 psi or so in about 30 seconds, so i think it would get rid of air fast enough to use for that application.

[theregoesthewindow]

Pimpmann, that is only the brass valves. My plastic one is only rated to 150psi.

[Brian the brain]

I'm curious...what would be serious pressure??

I'm currently collecting stuff to build an unregulated CO2 gun.That's about 900 psi or 60 bar.
If I could use a regular brass ballvalve that would help a lot...
I'm thinking of either building a semi piston gun or a full auto.
What do you guys think...will a ballvalve break apart or just leak when it fails??
I once sawed a 12 grammer in half and the walls are surprisingly thin.
The walls on a brass ballvalve are a lot thicker.


And I think a pop off valve would not be a good idea to use in a bb gun.
No control.

[CS]

Window: What size? Look at the pressure rating on the pipe and its proably pretty close to 150. Yes, I was assuming the use of a metal ball valve connected to a PVC pipe. But on are sprinkler system, its always been a pipe failure and never a ball valve.

B the B: If your using without a reg, DR on the spudtech forums pointed out that was very unsafe. What can happen is it will "freeze" the valve in the open postion. The ball valve can be used after the reg, just not by its self.

[nicholai]

yes tony you are soo correct. thats because when something is rapidly depressurized it gets cold, or frozen. simmilar to an air conditioner condenser or freezer workings

[boilingleadbath]

I think most brass ball-valves are only rated to about 600 psi (40 bar).

I'd suspect most would be designed to fail in the least enegetic way possible, and I'm pretty sure that a good majority of mcmaster's valves do say something to that extent.

That being said, for a few $ more, you can get ball-valves rated above 1000 psi.

Assuming you want this to be a repeater, I'm suspecting you'd want 2 of these - one for firing, and one for pressurizing the chamber from the storage vessle?

[Brian the brain]

The CO2 bottle has it's own valve so I can use that.

if all other options fail I will certainly order me a high pressure rated ballvalve .
(Could venting the pilot through a regulator be one of the options??
For a 9mm the pilot could be tiny thus a small amount of gas to vent..)


anyway..full auto is out because of freezing you say..
Still I'm gonna try it but i'll only use a small amount of bb's in the reservoir as a precaution and my hand will be ready to close the bottle's main valve.
I mean..if a valve can freeze up, then so can a regulator

[nicholai]

you could go full auto with a high volume air source from an air compressor, if you could constantly charge the chamber(s) at 80 or so psi. this wouldnt give it the freeze effect so bad however i wouldnt reccomend it for very many full auto shots. High volume (air) vs. high pressure (c02)