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N/A High Pressure Fear - Rant/Vent : )

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Bernie7 said:
Anyone else still get freaked out dealing with the high pressure air in PCPs? Sometimes I wonder if I picked the wrong hobby or this is something that goes away over time. I just finished a barrel polish on my Rattler. Reassembled the whole thing, screwed the valve back in the CF 580cc tank, applied fresh silicone grease and then screwed the tank back onto the gun. Hooked up a 9L tank and turned on the gas, heart rate jumped a bit when I heard the “click” even though I knew it was coming 😅. Heard a hiss, knew it had a leak and noticed it looked like the silicone grease was blown out from one spot where the bottle valve connects with the gun. Tried hand tightening a bit more and it reduced the sound but it was definitely still there. Dropped from 200 bar to empty in an hour. Okay, used my saber tactical degassing kit to clamp around the tank so I could tighten it even more. Also tightened (with my hand), the second regulator gauge as there was a super slow leak from that prior to performing any work.

View attachment 416817

While doing so, I can’t help but be concerned about-
  1. Damaging the tank by applying a ‘crushing’ force from clamping around the CF tank.
  2. Over tightening the tank to the gun and causing an issue from the torque.
  3. Damaging the threading on the gauge to the point it turns into a projectile.

In order of the points above, I know these tanks are designed to be really strong but is there any good documentation on what type of external compressing force, or torque they can safely take? #2 Similar thing, we always just say, “hand tight”. What is hand tight, I like having numbers, how many ft/lbs of torque is considered hand tight? #3 again, what are the numbers? I asked AoA a year ago when I had the original leak from the plenum gauge and they said that information wasn’t available.

How do I know I’m not damaging anything or reducing the structural integrity of the device(s)?

Part of my concerns include a second aspect, I live in the worst place imaginable to be able to enjoy this hobby. An apartment in the city, a poof too loud (not a negligent discharge, just standard PCP hissing, wooshing, and popping) and LEOs would rightfully be knocking on my door to see what’s going on. Or my worst fear which is something gets damaged and a part decides to become a projectile and harms someone.

The thing that balances this out though, is I think if these issues were as easy to trip as I sometimes imagine, we’d be hearing about it CONSTANTLY. Yet the reality seems to be that they’re extraordinarily rare.

Idk, just wondering if this sorta stuff ever bothers anyone else. Sometimes I think it’s like handling electronics. I used to be very gentle until I worked as a repair tech for over a decade and I feel like I know the exact line where something breaks so now I can be a lot rougher with stuff and not be concerned.

Thanks for listening to me vent : )

Hoping everyone has a beautiful Christmas and Happy Holidays!
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Had same concerns 30 years ago when I first got into PCPs. I got over it but still respect the power of high pressure.
 
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Poopshoot55 said:
Unfortunately you are more likely to be killed by a drunk driver than a high pressure air bottle. Maybe you should look into springers. 😉
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ive been snapped in the face by a wrist rocket , ive had a barrel snap shut by a factory light trigger , bent the barrel ! my front tooth is half broke off from a rock being thrown , as a kid i had a horse fall down and roll over on me at a dead run ! so can i count on people to stay on their own side of that little painted line at 65 MPH. ? and still i am most afraid of the government !
 
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ctshooter said:
The reason is it can cause galling on the metal to metal surfaces.
Click to expand...

I agree that silicone oil or grease is a poor lube for metal to metal sliding surfaces. I would have thought that for a thread that would normally be left dry, silicone can't hurt, as threads don't move except during assembly and disassembly - unless that is a poor assumption. Are you suggesting silicone lube is worse than dry for galling metal to metal friction pairs?

Yes, dry aluminum on aluminum, or stainless steel on stainless steel (such as 304) gall like mad when the same alloy and temper are used for both surfaces. But this occurs when dry, so an anti-seize paste could be a good thing. If not lithium or Teflon grease, then copper paste.

Any soft metal that works hardens significantly will tend to gall worse than harder metals. Aluminum and many stainless steel grades fall into that category. Harder stainless or "carbon steel" is less prone to galling, but sliding pairs that are perhaps 10 point Rockwell C apart in hardness are even better. Mild steel on mild steel will also gall, but not as quickly as stainless on stainless and aluminum on aluminum - especially when running cut threads together. Passivation or anodizing should help reduce the tendency to gall, but break through that surface layer and parts can seize by "cold welding" in a hurry.

www.essentracomponents.com

How to prevent galling on stainless steel bolts

What is fastener galling and how can you avoid it?
www.essentracomponents.com www.essentracomponents.com
 
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The order of failure, I'd think, is this:
1) O-ring(s) - via extrusion
2) Threads
3) Actual wall of HPA container

1 is safe to fail - it would just hiss.
2 would create a projectile out of a tank or a pressure gauge or a bolt or a connector. It is relatively manageable by never pointing threaded things in an unsafe direction.
3 would practically never happen.

Having said all this - pumpers are much safer than PCPs because the volume of air is small (for one shot), and because the valve is often double contained in the pump tube.
 
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ctshooter said:
The reason is it can cause galling on the metal to metal surfaces. Tom from AAA made a point of this in some other threads where a user had two parts pretty much fuse together. Now Tom uses Very Fine threading and most others are more coarse. Galling is less likely on the coarse threads - but still a posibility.
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The silicon reacts with anodizing to anodizing, I darn near destroyed my Mavericks air bottle and adapter, the anodizing was gone and the threads were being attacked, had a heck of a hard time getting the bottle off. Got the silicon off, used real lube, been fine now for 2 years, no bottle rockets...luckily.
 
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Bernie7, I suppose everyone has some initial mistrust in something new to them. I remember my first static line parachute jump. You’re counting on the equipment to be 100% foolproof. Same went the first time I hung over a cliff learning to rappel. Once you get some experience you gain some trust. Just don’t get complacent.
The only comment regarding your leak, and this for the most part refers to anything high pressure, you tightened the assembly while under pressure. Big no no. Always de-pressurize, look for root cause and then try again. It’s unlikely anything would blow up but a chard or something could launch into you or something else.

As far as silicone on tank threads and tank O rings, there are two definite schools there. Grease, and no grease. I serviced literally thousands of scuba tanks for a dive shops tanks and customer tanks and every single one had silicone grease on the threads and the O ring had just enough grease to make it shiny. The grease on the O ring was just to prevent the O ring from wrinkling at final seating. Grease on threads was to prevent galvanic corrosion because the valve and aluminum tanks were dissimilar metals. SCBA’s and there valves are typically both aluminum and that’s where galling can occur. As I was posting I contacted a major high pressure air vendor here in Ohio that heavily services the fire service. I asked to speak to their SCBA technician. They typically do not lubricate SCBA cylinders and valve threads. To be clear, this is the threaded portion of valve that screws into the carbon fiber tank, NOT the outlet threads.

Bare aluminum on bare aluminum can cause galling. The best way to prevent that is to loosen or tighten the valve very slowly until it is completely loose. Which should occur within a half turn or so. And that pertains to straight threads which is all I ever saw on SCBA’s. The technician added that IF they do use a lubricant it is typically Krytox or equivalent. And it is used very sparingly.

Tapered threads on the other are a completely different matter. Galling on stainless to stainless can be a challenge. I worked with assemblies for the oil patch industry and assembled and disassembled thousands of assemblies and SS on SS disassembly sucked. But we typically do not see that on airguns.

So how you choose to lubricate or not lubricate will depend on the school you ascribe to. I have never had any issues with either process. YMMV.
Slow is smooth, smooth is fast.
 
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On the subject of greases.....
A while back there was a discussion on why you use silicone Type of Grease in HPA applications...
Some were testing the Flammability of such greases...
Well I didn't see any test on greases like Kyrtox or Molykote 33..

So I did my own test.
Using a small butane torch...
I know this Was not scientific-controlled experiment, but what I found was eye opening..

I test both silicone and synthetic based SuperLube, Pure Silicone SCUBA grease, Molykote33 and Krytox #205.
It took a little bit of time, all greases but the Krytox flamed up. ...Side note: the next longest to flame up was Molykote 33!
Interesting!! But I still use silicone to lube my O-rings and Krytox on High stress areas like Bottle O-rings

Also on the subject of using silicone as a thread lube.... I wouldn't used on my Bottles!!
Ben Taylor, several years ago did a test of silicone lube on various metals.
He found it caused major Galling.
Aso once it contact the metal surface, it imbeds it the surface...
He had to surface grind the metal to remove any trace of the silicone!

So I will only use Krytox to lube my bottle Threads!!
 
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I've always been a bit nervous around them for the same reasons.

But with time and experience I'm much less concerned. Now I'm in that state where I need to be thinking doing routine operations. The other day my foster fitting collar wasn't clicked on, and after a few hundred psi of air built up (cylinder started at zero) the fitting popped loose and air started hissing from the fill hose. First time I ever had my 4500psi cylinder wide open to air and frankly it was unremarkable. I'm sure it helps I use a Brancato slow-fill hose.

David
 
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Ca_Varminter said:
On the subject of greases.....
A while back there was a discussion on why you use silicone Type of Grease in HPA applications...
Some were testing the Flammability of such greases...
Well I didn't see any test on greases like Kyrtox or Molykote 33..

So I did my own test.
Using a small butane torch...
I know this Was not scientific-controlled experiment, but what I found was eye opening..

I test both silicone and synthetic based SuperLube, Pure Silicone SCUBA grease, Molykote33 and Krytox #205.
It took a little bit of time, all greases but the Krytox flamed up. ...Side note: the next longest to flame up was Molykote 33!
Interesting!! But I still use silicone to lube my O-rings and Krytox on High stress areas like Bottle O-rings

Also on the subject of using silicone as a thread lube.... I wouldn't used on my Bottles!!
Ben Taylor, several years ago did a test of silicone lube on various metals.
He found it caused major Galling.
Aso once it contact the metal surface, it imbeds it the surface...
He had to surface grind the metal to remove any trace of the silicone!

So I will only use Krytox to lube my bottle Threads!!
Click to expand...
Burning fluorinated compounds (Krytox is fluorinated) will release horribly toxic gases. Likewise with any Viton or Kalrez. Don't do it!!!

David
 
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