This Is What Can Happen.....

[chekbone]

You NEVER test anything to destruction using air pressure.... you use a fluid that doesn't compress and store energy.... Hence the term "Hydrostatic" testing.... Alternately, for testing things like the shear strength of screws, you can use direct mechanical force, like a hydraulic ram, as used by Lloyd to test the Disco screws....

Bob

To that point i would agree, but will hydrostatic testing hoot the valve out the back of the gun along with all the other stuff? To see if things would go flying would be the only reason for a test like that.

Oops, think i just figured out how to separate a quote.

[oldgearhead]

Here is what is still bothering me about the original accident.
The guy who ended up with the valve in his leg said he was opening up the carbine to replace some 'O' rings located behind the hammer with a section of hose. Okay? However, why does he continue removing screws from the gun after access to the space behind the hammer is clearly available. Was he
making a training video about the breech screw? Because he spent more video time with the breech screw than anything else. I'm thinking maybe he started to remove the trigger assembly after the forearm..?

[Gerard]

To that point i would agree, but will hydrostatic testing hoot the valve out the back of the gun along with all the other stuff? To see if things would go flying would be the only reason for a test like that.

Some folks need to throw a battery into a fireplace and have it explode, sending schrapnel and burning caustic chemicals throughout the room, before they'll believe the ancient warning NOT to put batteries in a fire. Guess it's a personality thing. Fortunately for the survival of our species, most of us don't need to see that things can go horribly, painfully wrong to believe that they will where certain 'Darwin award' actions are concerned.

We know that high pressure air can be used to push things out of a tube at very high energy levels. We're all in this forum because that happens; it's what an airgun does, pushing pellets out of a barrel very quickly. The main tube of an airgun of whatever make using a setup in any way like that used with a HiPAC installation, where the valve needs to be stable so as to create a seal against the pressure vessel, is very much like a large bore barrel, the valve is like a really big heavy pellet. If you grind away the only bolt restraining that pellet, the HiPAC or whatever cylinder will shoot the valve out the tube. Quickly. Why would anyone need to test this by grinding away the bolt?

[Voltar1]

Nope. But I think a good test for things flying out the back of the gun, wish I had the rocks to try it - would be to lock a pressurized tube in a vise and grind the valve screw down until the valve goes rocket. Not suggesting any one try it, just saying i won't. I measured the slot on my hipacs and both of mine have about .050 thickness. I remember somebody say that it was tested it to 5000 psi.

how did you measure 0.050" wall?
Or is it od - id?
What measurements did you get on yours?

[rsterne]

oldgearhead.... He stated that he was taking out the stock screw (ie presumably the front screw in the trigger group) when it blew.... That screw goes into the space in the Disco valve right behind the O-rings, so may have been taking some of the load from the valve.... and when he removed it, either the (single) valve screw sheared (or was already sheared) and the valve blew out the back....

Bob

[chekbone]

If you grind away the only bolt restraining that pellet, the HiPAC or whatever cylinder will shoot the valve out the tube. Quickly. Why would anyone need to test this by grinding away the bolt?

If you're gonna respond, respond to the question being asked. Obviously the initial point got lost in your understanding, which is. If the valve screw sheared would the valve have enough force to push out the hammer, counter spring pressure, hit the end cap, shear the upper and lower rear screws through the tube and knock out the end cap and all that stuff goes flying out the back. No s--t, the valve will go flying out the back of the tube if you cut the screw and there's nothing behind it. We just saw the end result, DUUUH.

[Gerard]

If you're gonna respond, respond to the question being asked. Obviously the initial point got lost in your understanding, which is. If the valve screw sheared would the valve have enough force to push out the hammer, counter spring pressure, hit the end cap, shear the upper and lower rear screws through the tube and knock out the end cap and all that stuff goes flying out the back. No s--t, the valve will go flying out the back of the tube if you cut the screw and there's nothing behind it. We just saw the end result, DUUUH.

We mature now. Okay, since you're wanting to point fingers and question my reading comprehension, I'll provide this link for the second time in this thread:
http://www.airgunforum.ca/forums/topic69359.html
Did you bother to look the first time? Did you bother to read up on what happened? There's another thread where a moderator posted the results of his and two other experts' evaluations of the evidence, and their collective conclusion that the airgun valve's single retaining screw sheared, allowing the valve to fly backward in the tube, breaking through all the metal bits behind it and flying 38 yards across the field. Luckily no one was behind it. The owner of the airgun insisted that it had never been filled anywhere near 2,000psi, and was at 500psi at the time of the incident.

So from that, it would seem a safe assumption that an airgun of this type (his was very similar in overall layout, using a Crosman zinc grip, sear, steel end cap, retaining bolt) will allow a valve under pressure, as low as 500psi, to cut through all that metal and fly out the back with dangerous energy, enough to smash apart one of Joe Hickey's nicest custom stocks on the way back across the field. Is this good enough for you? Or do you wish to see more people endangering themselves by replicating this same setup and failure? The answer should be obvious... duh.

[BigTinBoat]

We mature now. Okay, since you're wanting to point fingers and question my reading comprehension, I'll provide this link for the second time in this thread:
http://www.airgunforum.ca/forums/topic69359.html
Did you bother to look the first time? Did you bother to read up on what happened?

I thought he was referencing a gun with a HiPac in use. Isn't the link you reference a gun with the tube pressurized? Doesn't this put MUCH more pressure on the valve?

[Gerard]

The case under discussion in this thread, the case demonstrated in the videos linked and shown in this thread, was a case where a HiPAC was mis-used in pressurizing the main tube, using a Discovery valve with O-rings to seal it and a single retaining screw. If chekbone wishes to discuss the likelihood of failure of a proper HiPAC installation with 1 retaining screw then he ought to say so, but he said:

If the valve screw sheared would the valve have enough force to push out the hammer...

In such a case it would not matter whether it was a properly installed HiPAC or an unconventional use where the user sawed off the small end and sealed the rest to the main tube somehow. In either case should a single (or any number of) retaining screws fail, the valve wouldn't much care what sort of nonsense was happening upstream, it would be pushed just the same by whatever pressure was in the HiPAC. Put simply, an air cannon with the valve as the ammunition.

[chekbone]

I thought he was referencing a gun with a HiPac in use. Isn't the link you reference a gun with the tube pressurized? Doesn't this put MUCH more pressure on the valve?

Thank you. I was, it is and it does. Guy's so quick to get s--t started he missed the whole perssurized tube part of it.

[Gerard]

You really think so, that this is a problem of my eagerness to get things started? Thought I was answering the question. Seems to me that it really doesn't make a lot of difference whether the tube is pressurized to begin with or the valve face seal fails on a conventional installation, as either way the tube will be pressurized. Maybe only for an instant in the case of a failed valve face seal, but with a single small retaining screw that's probably enough to shear it off at 2,000psi or especially at 3,000psi, considering how little space there is for blow-by around that valve body. All that pressure wants to expand. It will do so at the expense of whatever parts are in the way, unless they're built to withstand that amount of pressure.

[chekbone]

How did you measure 0.050" wall?
Or is it od - id?
What measurements did you get on yours?

Sorry, I missed this one. I measured the outside, measured the inside, took the difference and devided by two. My micrometer is a cheap one from AutoZone but I did it several times and went with the most constant readings. All readings were within +/- .001

[rsterne]

I believe Walter also asked what dimensions you got for ID and OD at the O-ring groove.... How old is your HiPac, ie when was it made?.... Coarse or fine threads?....

Bob

[Voltar1]

Outside where? What measurement?
Inside where?

[cilami]

Someone is willing to part the cost of hydro testing a couple of Hipacs. See here: http://www.network54.com/Forum/275684/message/1442697643/Re-+The+Hipac+failure+had+nothing+to+do+with+the+mods

An interesting experiment. Now, where to find two users willing to sacrifice theirs units in favor of the airgun/Hipac community?

[chekbone]

Now, where to find two users willing to sacrifice theirs units in favor of the airgun/Hipac community?

Why not ask Alex to offer up a few, seems it would be in his best interest.

This is much nicer now that I can quote properly

I believe Walter also asked what dimensions you got for ID and OD at the O-ring groove.... How old is your HiPac, ie when was it made?.... Coarse or fine threads?....

Bob

I measured it again but this time with the light on and glasses cleaned. My micrometer is a cheap one and seems to be slipping, didn't know I had to zero it after every slide. I got mine a few months ago, fine thread I guess, same thread as the end cap part. Where the oring goes on the bottom part the outside is .674 on the qb one and .694 on another, inside is
about .592 on both. The outside diameter differs by .020, that's quite a bit

[Voltar1]

Thank you Steven. Even the thin one has 0.041" wall not bad.
Please measure od of threads and od of extension tube.
I bet you mean caliper vs micrometer eh? :-)

[cilami]

Now, where to find two users willing to sacrifice theirs units in favor of the airgun/Hipac community?

Why not ask Alex to offer up a few, seems it would be in his best interest.

This is much nicer now that I can quote properly

I believe Walter also asked what dimensions you got for ID and OD at the O-ring groove.... How old is your HiPac, ie when was it made?.... Coarse or fine threads?....

Bob

I measured it again but this time with the light on and glasses cleaned. My micrometer is a cheap one and seems to be slipping, didn't know I had to zero it after every slide. I got mine a few months ago, fine thread I guess, same thread as the end cap part. Where the oring goes on the bottom part the outside is .674 on the qb one and .694 on another, inside is
about .592 on both. The outside diameter differs by .020, that's quite a bit

Checkbone,

I don't think Alex would be very interested in testing this. He already did a hydro test to 5,000 psi back in 2011, according to this post in the airgunforum.co.uk forum:

""Rodents' Rapture
08-11-2012, 08:01 AM
Who is it that started this pressurized tube nonsense? There's absolutely no way for the tube to become pressurize unless it's totally sealed at the valve and threads. There's too much mechanical aptitude around airgunning for nobody else to pick up on that! No seal, no pressure, no boom. It's not gonna happen, why don't people get it? It must be the non-existant horror stories. The valve flying out the back of the gun only makes sense if there's nothing behind it.. Let's see. The valve set-screw breaks, the valve pushes the striker, compressing the spring until the striker hits the end-cap, shearing the rear breech screw and rear frame screw knocking the end-cap off, just flew by your head, shearing off the cocking-pin so that the striker goes flying past you head just before the valve comes flying past your head. REALLY? Once the seal is made if the valve moves the seal is lost but it may seal at a lower pressure unless the seal has blown out completely, which has happened and still no boom. Get the facts

What logic is it that says the max recommended pressure is the recommended use pressure? I don't get it.

BTW, some people have their facts wrong, AGAIN! It was pressure tested long ago to 4700psi, hydro tested to 5Kpsi less than a year ago. (blue emphasis by cilami) NO BOOM and there's never been a boom. Remember that honest reviews about any product only come from actual users.

Anyway, i just came by to show off the newest addition to the PowerMax line of excellent products.
56142
"PowerMax-HiFLO Valve" in 303SS. Designed with HiPAC users in mind and exclusively for use with the HiPAC system.
56143A post wouldn't be a post without this fellow in it
Rodents' Rapture
.22; 24"brl; 2240CCS; HiPAC system + 2X extensions"

The point now would be to test the max/min tube thickness of the HiPAC units as mentioned here. I assume that a 0.050" thickness wall would yield a different result when compared to a
 0.025".

[rsterne]

Yes, if the wall is half as thick, for the same diameter the MSWP is also half as great.... Hydrotesting is only valid on ONE particular pressure vessel, not as a guarantee that every vessel is safe, as production tolerances have a great effect on that.... If you want to rely on Hydrotesting, you must test the weakest one that ever gets out the door, which means you must have a quality control system that guarantees that....

Bob

[cilami]

Yes, if the wall is half as thick, for the same diameter the MSWP is also half as great.... Hydrotesting is only valid on ONE particular pressure vessel, not as a guarantee that every vessel is safe, as production tolerances have a great effect on that.... If you want to rely on Hydrotesting, you must test the weakest one that ever gets out the door, which means you must have a quality control system that guarantees that....
 
Bob

Perfect. But let's see it from the end user perspective. As an example, if it is proved by whatever accepted method, that a 0.050" wall is safe for the HiPAC o-ring slot in general, then all I have to do is to check that my unit has a thickness of at least 0.050". Am I correct?