An accident. Take care please. Playing with HPA is not a joke

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mubhaur

mubhaur

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Nov 8, 2015
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Karachi, Pakistan
It happened with a product of a well-known tuner.

That is why I make plenums out of solid rod of high grade stainless steel only. 

https://www.facebook.com/groups/fxairguns/permalink/1792425960930224/

This is very serious accident.

The difference in my plenum and the blasted plenum. 

Be careful please

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Regards, 

Umair Bhaur 
 
No one says hpa is a joke. Have you seen a carbon fiber tank go boom? Not pretty. This is why you don't use stuff made by people. They are not regulated by the states or follow any DOT laws. They probably don't even pressure test it 3X its max fill. Only use parts made by a airgun manufacturer. They will teat these things way above its recommended pressure to be safe to sale cause they don't wanna get sue if anything goes wrong. Last time a guy bought a hpa kit made for a Crossman c02 pistol. It went kaboom and the valve went into the guys legs. Aint pretty.
 
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Just for the record, most stainless steel is NOT good for a high pressure, pressure vessel..! And if used, should be checked and maintained by using DOT standards. Like has been said here, have you seen what's left of an exploded high pressure, pressure vessel ? It's NOT pretty, especially if someone was near enough to have been injured (not me thank you).

High grade carbon steel is normally a better choice for a high pressure cylinder. If you work in the food industry, a stainless like 304L is usable, but there is a very good reason outdoor cylinders (welding, inert gas storage, etc., cylinders are made of a good grade carbon steel. 

Properly wrapped carbon fiber cylinders are also a very good choice for material. But again, not just any material, and not just wrapping in any ol form.

One thing at I see that having been a part of the industry that uses very high pressure cylinders, is seeing that many, if not most all of the "machined" aluminum cylinders in our PCP guns...have been machined with hard square corners. This is a BAD thing. Makes me cringe every time I...don't quite "fill" one of mine..!

If you look closely at the steel stamped numbers/letters on heavy steel cylinders, you'll notice that the stamps are much different than standard steel stamps. High pressure steel stamps have "rounded" edges, no sharp edges like a normal steel stamp..! Check that for yourself..!

Be careful out there.

Mike
 
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Dear Mike VV,

I understand that Titanium is a better material for such cylinders or the carbon steel as well as compared to stainless steel.

The real point is not the material chosen, rather its the calculation that how much pressure the plenum can bear. This can be made of any good material and for the ability to withstand the pressure is the design and wall thickness of such cylinders keeping in mind the material used.

I keep the calculated pressure at 200% in order to make such things overbuilt. I prefer overbuilt items for such uses.

I hope I make clear my point.

Further it must be tested at the 200% pressure.

regards,

Umair Bhaur


 
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This looks like a commercial for your external plenum wich also can blow up in some cases. I think that Vlad sold big number of his plenums without of such accident luckily . Accidents can happen and it was big luck that nobody was seriously injured. With Impact M3 I don't see big need for external plenums.
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I could use it as commercial as you have said. I also agree that accidents can happen with best products.

Now the matter of fact is that I live in Pakistan. I am a professional accountant. I do not have a lot of time to do all this to earn money. I normally do it for myself and my friends. Further it is difficult to sell such items abroad due to Customs and Export issues.

Thus you can call it a commercial but without "commercial benefits".

I hope you did not read my other posts. Even two posts were yesterday regarding experiments.

The person with whom this accident has happened, has contacted me and wanted that I could send him my plenum. I just told him that I would have to do research if it is possible for me or not.

Further the legend Mr. Harry (Yarrah) was asking me for my made plenum for his RAW that he is going to get from Martin. I openly offered him that I am going to send it as a gift. The reason is that he is Mentor for me. But he refused to take it without charges and advised me to share the specs. I shared the specs and now he might get it machined in Australia. 

Is it still a commercial !!!

Best regards,

Umair Bhaur 
 
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I am not expert or engineer of any kind. I just saw this matter with an eye of third party in this case.

Like a totally amateur I would like to see some round inner edges in plenums of that kind...

Best regards,

Goxy
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No issues Goxy dear,

You are respectable for me. We normally see things from our own view point which is sometimes correct and sometimes not.

Regards,

Bhaur


 
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I don't understand the assertion that stainless steel is not a good material to use, high strength carbon steel is better. There is an obvious corrosion difference that is not in favor of carbon steel. But different steels, carbon or stainless, have higher and lower yield strength, The same thing is true of aluminum. 304L is a lower strength, lower corrosion resistance, stainless steel. All steels have a favorable yield curve with great elasticity - no yielding - until you get very close to yield. Aluminum does not work that way, it's yield is fairly linear with stress - it yields at stress well away from the quoted yield strength. But airplanes are made of aluminum at fairly high levels of stress (so they can get out off the ground) and they are pretty reliable.

The secret to safe application of any material is to design the device at a fraction of yield, and to consider all the aspects of the stress on the device. 200% seems OK to me, I would not go lower. But it is not just the wall thickness that has to be checked. The threads have to take the stress too. All aspects of the device have to be carefully considered.

If it matters, my bachlors is in mechanical engineering. But that was a long time ago. I am pretty confident I still remember the basics. 

Engineers use tests to be sure that we did not miss anything. It proves the calculations are correct. 
 
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Spec's must be different there. Here in the U.S. Such pressure vessels must be tested to 300%. Minimum. That would put the tuypical scba at over 1350 and have a typical burst pressure in actual too failure test in the neighbor hood to 16 to 18000 psi. 

Even then, they vent. Sometimes with a lot of force, Not one on record has ever exploded. With thousands in very rough useage in the fire fighjtomn industry.

Knife
 
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Fascinating and terrifying subject. thanks for posting.

Of interest, pigeonman above mentions 3X pressure test. Mubhaur mentions 200% aka 2X..

I work with rigging equipment as part of my job, (wire rope often called "aircraft cable" shackles, slings, turnbuckles etc.) and I understand that on such equipment the stamped rating at 1/4 or 1/5 it's actual breaking point. (ie, actual failure when tested was a 4x 400% or 5x 500%)

Given the catastrophic potential, I personally would not want to be playing with PCP parts that weren't at least tested successfully at 3X (rated at 1/3 failure point) 200% would NEVER be acceptable for overhead lifting. Of course the potential for shock loads is more of a problem than sudden changes in pressure due to temp, impact, etc..



I'd be curious to know what the actual standards are for rating/vs./failure point of established applications of high pressure gas containers, eg: SCUBA, welding gas, propane cylinders etc.
 
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Spec's must be different there. Here in the U.S. Such pressure vessels must be tested to 300%. Minimum. That would put the tuypical scba at over 1350 and have a typical burst pressure in actual test in the neighbor hood to 16 to 18000 psi. 

Knife
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Well, there it is. 300% makes much more sense based on other industry testing standards.
 
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