Can 206 PSI DETONATE?
206 PSI can go BANG ! ! !
Diesel engines operate efficiently anywhere from 14:1 to 25:1 compression ratio. So, the mean sea level air pressure of 14.696 PSI air compressed quickly at the ratio of 14:1 Or approximately 206 PSI becomes so hot it can detonate diesel fuel injected into it.
With PCP air rifles we are using easily 10 times the pressure of a common diesel engines initial compression. Any flammable lubricant could easily be atomized in a multi stage PCP pump as it is heated, collects at a valve and is suddenly released into the next stage or into the quickly heating connecting hose.
So, what could happen if the rifle tank is low in PSI when a pump or connecting hose detonates? What if the rifle tank is already heated and nearly full?
All Replies
I feel a circle jerk coming on…
Again we prove the value if a forum.
Common interest and communication of individual concerns and experience leads to an informed group of individuals that are less likely to make serious mistakes.
Also I have observed from the hunting experiences and gory details posted in other topics on this forum, that are ignorantly deleted from other forums, we are educated to how Deadly our High Power Air guns and equipment can be. A picture is worth a thousand words and a thousand words can paint a memorable picture that both educates and instills a cautious respect for the power at hand.
Thanks for all type input ❗
Lurker,
Here’s another thought… Have you ever had a static shock? Did you shuffle across the carpet and then get a tiny little spark when you touched something?
Did you have a burn mark on your fingertip? Ever wonder what the temperature inside a spark (even tiny ones) is?
The easiest way to explain the lack of injury is to point out that the “volume or mass” of heat generated was not enough to cause damage as it dissapated and transferred outward.
There’s a similar thing going on with a pump. Yeah, if everything else is ignored, a slow steady rise in pressure causes a rise in temperature. BUT, the real world does not ignore anything! As you squeeze the air via the pump, it gets warm but that heat dissapates and flows into the pump body and out into the air. Stroke that thing like you just met Ginger Lee and you’ll still be way short of the charge air getting to auto-ignition temperature of oil because the heta is going everywhere!
Lurker,
My point, sarcastically attempted (because I’ve been through this before and I happen to be old and grouchy) is that one theory or equation does not explain a phenomenon just because one chooses to ignore all the other factors.
A diesel engine would not work if you had a 3000psi hose blowing down the intake. 100 to 1 compression would not work if it took 10 seconds to generate. A perfect diesel won’t run if the fuel timing is off…
Diesels run because atomized fuel is injected just as rapidly compressed air is heated to auto igmition temperature. Why do diesels have glow plugs? Because the cast iron block soaks up and transfers the heat from compression so fast that without them, it is much harder to get the damn thing started!
Stroking a pump creates compression and heat but that heat flows to anyplace colder. Heat moves, that’s another theory that has been proven but guys on airgun forums don’t remember it. Heat ignites fuel, not pressure. You can put diesel fuel or even napalm or TNT under 10s of thousands of pounds of pressure but if the temperature is low, it won’t ignite.
I saw the recent post from the barefoot pumper. I’m too tire to go into a forensic study right now, but I don’t think the choice of lube for his pump was the problem.
Jerry,
Would you say that the 3000 PSI we use is no more likely to detonate than my example of a diesel engines compression of roughly 206 PSI
❓
i think the comparison to a diesel engine is misleading. temperature is not proportional to the pressure.
but the ratio of start-compression-cycle pressure to end-compression-cycle pressure is the same as the ratio of start-compression temperature to end-compression temperature. if pressure in a diesel cylinder increases more than 10-fold, the temperature increases more than 10-fold.
with a pcp hand-pump, the ratio of start and end cycle pressures is much less than 10, even when you start to pump and that ratio is at its max. on the other hand, the hand-pump doesn’t dissipate heat rapidly between cycles/pump-strokes so the temperature can increase as you pump, especially if you pump rapidly.
I’ll get really worried just as soon as I can pump as fast as the starter on my truck cranks that diesel.
i sent the pump to sunoptics because replacing the broken check-valve spring didn’t fix the problem.
they sent me back someone else’s beat-up pump which pissed me off but it’s such a hassle dealing with them and so expensive to ship, that it’s sitting in my basement. i’m not sure if they rebuilt that pump using motor oil.
i bought an fx (because of the 5 year warranty) while diddling with the defective airforce pump and that’s the pump i use. the airforce pump is collecting dust.
I wouldn’t. Check the shoebox compressor recommendations for their pumps. Call a local dive shop ask what they use.
and airforce/sunoptics recommends motor oil for all pump parts including o-rings. the following is part of an email exchange between a sunoptics employee and me regarding a problem with the airforce pump:
i replaced the spring and am still having problems. i have one more thing to try before returning for service:
should the base adapter O-ring be lubricated with motor oil or with silicon O-ring lube?
keith
—————————————————————————
Apr 12
Reply
Duane Sorensen to me
lube all parts with motor oil.
duane
Duane Sorensen <dsorensen@sunopticsusa.com>
I think that’s why we use silicone on our o-rings for the gun. Not sure of multi-stage pump.
For transport and storage I use a SCUBA dust cap… For the gun during transport I use the AF Valve protector and a couple of PVC 1/2 Plugs for the female AF connections (gun/tank mount and fill adapter).
I use these to protect against dust, dirt, moisture, and most importantly RemOil which is sprayed on all my firearms.
- You must be logged in to reply to this topic.
I feel a circle jerk coming on…
Hey a few bodies in motion and a little lotion. Physics law #69 😆