Safe or Silly....

[Pete]

I hadn't thought of it that way, but I guess you're right.... If the volume is only 0.01 CI, and at 1500 psi the maximum energy from isothermal expansion is only about 5.8 FPE/CI = 0.06 FPE.... A 1 oz. gauge would only reach 8 fps....

So as shown, it's very dangerous.... With a 0.010" hole in an otherwise continuous tube wall it's not an issue.... Live and learn....

Bob

Still wouldn't want 1oz @ 8fps in my eye while seeing how much psi was in the gun...

[HYspd]

i'm a lot more interested in what happen when the tube splits from fatigue at that hole
than I am in what happens if the threaded port pops off.

[willbird]

solder and high pressure is a big NO

Cheers marno

I would qualify that to "solder improperly used". When used properly in keeping with a good design it seems to hold together with two pressure vessels at 10,000 psi or so, both pressurized in quick succession :-). Do not want to violate forum policy so you will have to think on that one to discern the projectile launching device I speak of :-). Barrel liners are often just GLUED in with acraglass and experience 24,000 psi or more, the key thing is enough sq inches of bond or solder to do the job....or they are soft soldered in.

Bill

[HYspd]

in the pic I see what very much look to me to be soft solder, doesn't really even look like Lead Free high/tin from lowes
that has a light colored brighter shine even when aged

and i'm about as sure as I can get from a Pic that it's not bearing (hard) solder..the soldering itself doesn't appear to have been properly fluxed

in the pic the tube appears to badly (from a structural viewpoint) prepared, lots of possible stress risers and a reduction
of material thickness leading to a place of material removal, soft solder doesn't add much by way a strength to make
up for the removed material.

for certain, that is not a silver solder joint, the appearance would be much more like a brazing as the temp required to
flow silver solder are up there with the brass compared to the low heat requirement of soft solder.

my question is still  how big of a bang would that tube make if it burst?

[chuckinohio]

my question is still  how big of a bang would that tube make if it burst?

  Yes, a very real concern my friend.

  Precisely what material is that tube made from, anyone know?

  Pinhole port aside, what you have in that picture is a pressure vessel with a very large heat affected zone surrounding that fitting.
  I don't think that the fitting flying off is the immediate problem, I think that the heat affected area has the potential to fail as a whole, and separate from the tube body in an abrupt fashion.
  What are the chances of that tube being an air hardening alloy? Anyone care to guess what the compositional and structural changes are between the heat affected zone of that modification and the parent tube body?
  At pressure, that tube will expand and contract at vastly different rates due to the compositional change in the steel at that site, leading to accelerated fatigue, and failure. Add to that the affects of vibrational feedback from the shot cycle, and it has even more potential to fail.

  Without knowing the composition of the tube material and how it will be affected by heat, even heat as low as 250 to 400 degrees Fahrenheit, I would make a SWAG of 'not for me'.

  Of course, I may be all wet, and completely off base. Please feel free to correct me as applicable.

[willbird]

my question is still  how big of a bang would that tube make if it burst?

  Yes, a very real concern my friend.

  Precisely what material is that tube made from, anyone know?

  Pinhole port aside, what you have in that picture is a pressure vessel with a very large heat affected zone surrounding that fitting.
  I don't think that the fitting flying off is the immediate problem, I think that the heat affected area has the potential to fail as a whole, and separate from the tube body in an abrupt fashion.
  What are the chances of that tube being an air hardening alloy? Anyone care to guess what the compositional and structural changes are between the heat affected zone of that modification and the parent tube body?
  At pressure, that tube will expand and contract at vastly different rates due to the compositional change in the steel at that site, leading to accelerated fatigue, and failure. Add to that the affects of vibrational feedback from the shot cycle, and it has even more potential to fail.

  Without knowing the composition of the tube material and how it will be affected by heat, even heat as low as 250 to 400 degrees Fahrenheit, I would make a SWAG of 'not for me'.

  Of course, I may be all wet, and completely off base. Please feel free to correct me as applicable.

I have never heard of an air hardening alloy being sold as tubing (but I learn new things every day). Somebody was kind enough to send me a spreadsheet on tubing strength when used as a pressure vessel...the 4130 tube that gets used for a lot of stuff is "normalized" so it is not getting it's strength from heat treatment.

But the "heat affected zone" is an area where the surrounding metal quenched the heat, so it actually may be harder, even if it is not an air hardening alloy, BUT I think the metal needs to be heated to above the critical temperature, which would be "red hot" ? If you stay below the critical temperature all you can do is anneal or soften the metal ?? And it if were "normalized" . Lots and lots of race cars are built from normalized 4130 tubing TIG welded together, works out very nicely.

Bill

[HYspd]

the picture has been taken down...but I looked it over 3 times and it appeared to me to be brass.

I think the AG is a benji pumper....I generally use my right hand to cock my break barrel so I would
also use my right hand on a multi pump so that damaged area would be pointing at my face during
pumping...

as somebody who has blown up a lot things via the whoops process, i'm calling this a Bad Plan.

[chuckinohio]

  There is tubing available in air hardening alloys, but whether or not it was used by Benjamin is debatable, and in all actuality probably really remote.

  My main point in using that as an example was more of a what if scenario.

  I have destroyed many items in the name of modification, and escaped serious injury a few times. Due to that, I always err on the side of caution, and assume worse case scenario.

  It may turn out to be a proven mod through repeated use, but I don't really want to be the guinea pig if you know what I'm saying!! 

  I wish him lots of luck with the mod, and hopefully it gives good accurate service.

[michaelthomas]

The real part of what I see here is that people should be encouraged to actually have items tested to ensure safety.

The speculation of many does not even begin to outweigh a proper hydro test which would cost about 60$.

There is a company called Galiso that is in my hometown of Montrose, CO that makes the hydro testing rigs that are used worldwide.  There is a guy that works there named Rick.  He was extremely gracious and helpful to me when I machined my air tubes.  They charged me 60$ to perform a DOT standard test on my stuff, and it came with a printout and his interpretation of the results. 

My tanks had odd threads, so I had to machine an adapter for their machine......that was it. 

My tanks passed the DOT test easily for a working pressure of 3000psi, but I learned from a post that I had made about them that many contentious people still doubted their safety based solely on the dimensions of the cylinders.  If I had relied on the opinions of folks that were certain that they knew "what was safe, and what wasn't".......I would have thrown away perfectly good cylinders and started over.

All the doubt and speculation in the world does not amount to a hill of beans compared to a real test.

If it's HPA......just get it tested. 

Mike

[willbird]

  There is tubing available in air hardening alloys, but whether or not it was used by Benjamin is debatable, and in all actuality probably really remote.

  My main point in using that as an example was more of a what if scenario.

  I have destroyed many items in the name of modification, and escaped serious injury a few times. Due to that, I always err on the side of caution, and assume worse case scenario.

  It may turn out to be a proven mod through repeated use, but I don't really want to be the guinea pig if you know what I'm saying!! 

  I wish him lots of luck with the mod, and hopefully it gives good accurate service.

But air hardening steel is typically used when it will be heat treated for hardness...the only air hard I would expect to see in a firearm where tubing might have some applications would be S7, and while I have never LOOKED for it in tube form, neither have I seen it listed. And to get any heat affected zone from re heat treating the metal would mean heating it to 1750F or so for S7 and A2....1850 for H13.

[Sfttailrdr46]

Some people have thin skin and take offense easier than others  if the intent was about safety and s serious injury potential existed then I would rather unintentionally insult someone and see them remain uninjured than remain silent and see one person injured due to my silence

[chuckinohio]

  There is tubing available in air hardening alloys, but whether or not it was used by Benjamin is debatable, and in all actuality probably really remote.

  My main point in using that as an example was more of a what if scenario.

  I have destroyed many items in the name of modification, and escaped serious injury a few times. Due to that, I always err on the side of caution, and assume worse case scenario.

  It may turn out to be a proven mod through repeated use, but I don't really want to be the guinea pig if you know what I'm saying!! 

  I wish him lots of luck with the mod, and hopefully it gives good accurate service.

But air hardening steel is typically used when it will be heat treated for hardness...the only air hard I would expect to see in a firearm where tubing might have some applications would be S7, and while I have never LOOKED for it in tube form, neither have I seen it listed. And to get any heat affected zone from re heat treating the metal would mean heating it to 1750F or so for S7 and A2....1850 for H13.

  I'm with you, believe it or not... 

  Air hardening tubular steel is used a lot in the bicycle manufacturing world.

  I wouldn't think it too far of a stretch to immagine some penny pinching bean counter substituting similarly dimensioned tubing for another alloy with no other thought in mind other than final cost of product shipped.
   -Insert cheap Chinese alloy steel bashing rant here. -
  Such an alloy in its annealed state, or machine ready state, may not pose any problems to machining operations prior to assembly, and go unnoticed.

  Pure conjecture, I am aware of that fact, but stranger things have happened.

  All metallurgy questions aside, I'm still a bit leary of modifying a pressure vessel unless it is a proven process.

[willbird]

  There is tubing available in air hardening alloys, but whether or not it was used by Benjamin is debatable, and in all actuality probably really remote.

  My main point in using that as an example was more of a what if scenario.

  I have destroyed many items in the name of modification, and escaped serious injury a few times. Due to that, I always err on the side of caution, and assume worse case scenario.

  It may turn out to be a proven mod through repeated use, but I don't really want to be the guinea pig if you know what I'm saying!! 

  I wish him lots of luck with the mod, and hopefully it gives good accurate service.

But air hardening steel is typically used when it will be heat treated for hardness...the only air hard I would expect to see in a firearm where tubing might have some applications would be S7, and while I have never LOOKED for it in tube form, neither have I seen it listed. And to get any heat affected zone from re heat treating the metal would mean heating it to 1750F or so for S7 and A2....1850 for H13.

  I'm with you, believe it or not... 

  Air hardening tubular steel is used a lot in the bicycle manufacturing world.

  I wouldn't think it too far of a stretch to immagine some penny pinching bean counter substituting similarly dimensioned tubing for another alloy with no other thought in mind other than final cost of product shipped.
   -Insert cheap Chinese alloy steel bashing rant here. -
  Such an alloy in its annealed state, or machine ready state, may not pose any problems to machining operations prior to assembly, and go unnoticed.

  Pure conjecture, I am aware of that fact, but stranger things have happened.

  All metallurgy questions aside, I'm still a bit leary of modifying a pressure vessel unless it is a proven process.

Hmm I never thought about bearing races :-)...that would indeed be a good use for such a thing :-). Most of my metal working experience has been "tool and die" and agricultural-automotive. Maybe I need to get out more :-).

And I do agree about modifying pressure vessels.

Bill

[Sfttailrdr46]

I was stationed on a sub tender and  submarines are the ultimate pressure vessels I know this is a side trip but the point is any time the hull was breached for a new through hull fitting after the welding was completed x rays and magnaflux tests were performed to insure that the work was safe when everything was completed. 2500 psi is a lot of pressure is dramatic if the vessel were to rupture due to heat induced fatigue and the resulting metal fragments could very well be lethal or at the least make one *(&^ of a bang 

[joel w]

I have read this all and I am not going to comment on the guys braze joint as I can't see it very clearly.   I understand the pinhole safety factor.  All I know is to get a good bond it needs to get really hot and the paint on the tube does not show that to me?

This is a silver soldered brazed test cap that was under just 250psi when it failed. It was one of my first big (12" x 12') chillers that I made. It is a 2.5" inch diameter and .098" thick CUNI (copper nickel) butt jointed to a 2" ID suction tube.  I was fairly new at brazing and you can clearly see from the picture that the flux did not get hot enough  on the right pic to run clear and the joint was weak (cold joint).  Granted this is now pretty oxidized after 8 years and is no longer pink and shiny.



When it let go, I was 1-2' away and there was no warning at all.  It hit me in the right side sending me 20ft in the opposite direction ripping off 2 jackets and my shirt.  I am still picking flux out of my skin to this day as it works it's way to the surface.  Luckily it just knocked the wind out of me, caused some minor internal bleeding and a bunch of road rash but it could have been much much worse..

Be safe!!

PS. Thanks for looking out for us Bob.  Feelings heal faster than flesh!

[rsterne]

Maybe so, but time to put this YEAR OLD thread to rest....

Bob