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Pressure of a 3 way valve

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Pressure of a 3 way valve

Unread postAuthor: jor2daje » Thu Sep 03, 2009 5:18 pm

I just got 3 Mead MV 20 3 way valvesoff ebay, they are rated to 120 psi, but I'm wondering if anyone else who has used them before has taken them higher. Im hoping to use this as a pilot for a qev in a relatively high pressure semi auto bb gun.
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Unread postAuthor: btrettel » Thu Sep 03, 2009 7:22 pm

If you want to go higher, find a valve with a higher rating. I'm certain you can take it higher (that is why such devices are built with a "safety factor"), but engineers choose a rating for a reason. Not given any information about the justification I'd stick with the rating.

Hydrotesting (search here for more information) to find a "safe" rating would be one way to find what's okay to go higher. Note that hydrotesting does not give you information about how quickly the materials are fatiguing (failing slowly due to cycling loading), so it's no replacement for the rating.

Edit: Sorry if this sounds pessimistic, but I've always found suggestions to go higher than a pressure rating to be silly. Take it from someone with some experience with stress analysis.
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Unread postAuthor: THUNDERLORD » Thu Sep 03, 2009 10:13 pm

Looks like an interesting "trigger" (the roller looking part on top (?)).
I got an HVAC electric switch in my junk pile that has an extremely light "click" (on-off) to it.

Maybe there's some way to add smaller diameter pipe inside for lower volume/ higher pressure use(?).

Safety wise, It may depend on whether an internal part will fail OR the outer casing will burst.

Either is bad but you've got three (two to break?).
Course similar to what Btrettel stated, if they worked at much higher pressure seems they'd be rated higher so they could be sold better.
IDK for sure. [/ramble] 8)
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Unread postAuthor: jor2daje » Thu Sep 03, 2009 10:56 pm

Well like you said, I have 3 but I do have solid plans for 2 of them, I think Ill probably be good to about 200 which would give acceptable power I think.

Btw I think Im going to take the roller out, I will have a rod linking the 3 way switch to my trigger. And according to a sheet I looked at these are triggered by only 6 grams so it should be easy to pull.
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Unread postAuthor: Technician1002 » Fri Sep 04, 2009 12:01 am

Often a hydraulic spool valve will work with air. Keep it oiled with hydraulic oil.

3,000 PSI valves like these should work just fine.
http://www.northerntool.com/webapp/wcs/stores/servlet/CatDsp?storeId=6970&N=96+1503+771529&cm_ven=natural&cm_cat=netconcepts&cm_pla=Google&cm_ite=hydraulic%2Bcontrol%2Bvalves
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Unread postAuthor: qwerty » Fri Sep 04, 2009 3:24 am

This is the one that poland spud showed me to use in my semi-auto
http://clippard.com/store/display_details.asp?sku=MJVO-3
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Unread postAuthor: POLAND_SPUD » Fri Sep 04, 2009 4:57 am

hey that's a nice deal... 3 of them for 13$ (with shipping)

have a look here first -> http://docs.google.com/gview?a=v&q=cach ... l=pl&pli=1

most pneumatic valves are rated for 10 bar because it's just a kind of standard... everything is usually rated for 10 bar - air cylinders, tubes, valves basically everything that is used in pneumatic systems is rated to 10 bar... filters and regs are sometimes rated little bit higher, to 12 - 15 bar, but they reg down to 10 bar usually... even QEVs are officially rated to 10 bar only

the reason is simple - 95% of pneumatic systems in factories, shops etc. run on 10 - 12 bar max... so what's the point of having one valve rated to 20 bar in the system if you'd have to add additional hp compressor to power it?

so don't expect to find too many directionally control valves that are rated to more than 150 psi... clippard MJVO-3 is rated higher but that's really an exception

fortunately, most valves can handle higher pressures... I wouldn't really worry so much about the casing or the spool itself...

I found that manually actuated direct acting valves should handle high pressures best, while solenoid(both direct acting and indirect acting) and piloted valves worst

I used to take my 5 way solenoid 1/4" valve (rated to 10bar) to more than 25bar for a long time... sometime ago I noticed it leaked via solenoid past 180 psi
so I dissembled it and assembled it, which somehow fixed it (I suspect that the small plastic ring was responsible for that but I can't tell for sure)

notice that the solenoid is like a blowgun connected the other way round - pressure will open it at one point pic


hey don't worry - it seems that your can take 300psi... 1/8" stuff can usually take a lot simply because it's so small... but I am a little worried about zinc body though so be careful

@tech
I've been thinking of using a hydraulic valve... lack of rated directionally control valves is really the only thing that keeps me from using higher pressures


@ qwerty
MJVO-3 is rated to 300 psi so I suspect it should handle 400 - 500 psi (but that's just a guesstimate based on its contruction - I don't own one)
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