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pilot venting

Posted: Fri Jun 13, 2008 6:07 pm
by mexthatcan
For a barrel sealing piston, with ~6.6 cubic inches of pilot, will a blowgun (either modified or standard) be enough to quickly actuate the valve? Or would something like this pop-off safety valve be better?
McMaster part #48435K72

A sprinkler valve is out of the question because it needs to be small, 1/4" or maybe 3/8".

Thanks in advance for your help.

Posted: Fri Jun 13, 2008 6:25 pm
by MrCrowley
It could work, it depends on your piston also. Though I would not recommend it, you'll be losing A LOT of power with a blow gun. I'd recommend a 1/2" ball valve, at the minimum a 3/8" ball valve.

Posted: Fri Jun 13, 2008 6:27 pm
by mexthatcan
the piston is fairly light, just a endcap thats been shaved down with some washers on it. I have no scale so i cant say exactly, probably a little more than a 1 1/4" endcap unmodified.

And even though the ball valve opens slower, it would be better than the others?

Posted: Fri Jun 13, 2008 6:32 pm
by jrrdw
Members have spring loaded ball valves to make them work/open fast and swear by them.

Posted: Fri Jun 13, 2008 6:46 pm
by MrCrowley
A 3/8" ball valve will offer probably somewhere around 4x as much flow as a blow gun. I can't be bothered doing the math, but the larger flow will easily out do the quicker opening of the blow gun.

Posted: Fri Jun 13, 2008 6:57 pm
by pizlo
definatly go with a metal, 1/2 ball valve.

Posted: Fri Jun 13, 2008 7:12 pm
by hyldgaard
I have had great experience with using a small qev as exhaust, and with that you can use your blowgun without problems.

Posted: Fri Jun 13, 2008 7:12 pm
by mexthatcan
If a quick connect is at the venting end of the ball valve, will that 1/4" hole restrict as well? And if so, can that hole me machined larger without compromising the integrity of the quick connect? Or since there is no pressure without it being inside the female adaptor, there is no issue

Posted: Fri Jun 13, 2008 7:16 pm
by MrCrowley
No it should be fine having a 1/4" QC on a 3/8" or 1/2" ball valve.

Posted: Fri Jun 13, 2008 7:25 pm
by mexthatcan
Alright thanks again for all the advice everyone gave. Using just a ball valve actually simplifies my original design.

Posted: Sat Jun 14, 2008 2:46 am
by Carlman
or use a qev then a blowgun or BV

Posted: Sat Jun 14, 2008 9:25 am
by Gippeto
I used a modified blowgun on my first. Check the video and see if you think it pilots quickly enough for you.



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