An experiment - main spring failure

[halocline]

Well, there you go, I learned something new today. And it's still early!

 

[Couv]

Well, there you go, I learned something new today. And it's still early!

Me too, I would have thought the balanced flow through design would allow the piston to float back and forth if there were no spring to push it open. But, now that you bring it up, the "balance" must take into account the spring force too.


Awap, what pneumatic tools do you have that need less than 120psi?

c

 

[redacted]

Me too, I would have thought the balanced flow through design would allow the piston to float back and forth if there were no spring to push it open. But, now that you bring it up, the "balance" must take into account the spring force too.


Awap, what pneumatic tools do you have that need less than 120psi?

c

I had to get an air power source to apply wall texture. She never told me when I was removing texture to apply wallpaper that she had the option to have it switched back on demand. Ended up buying a regulator to control pressure coming out of a LP compressor and installing that on a Mk2. Works fine.

BTW, I now have a Mk5 converted to din. I used a Scubapro universal din retainer with an o-ring just above the threads and about 1.5mm of shims so the retainer would bottom out and still leave enough room for the saddle and din Wheel not to bind. I canalized a metal din wheel from a POS Trident din converter and used the Mk20 upgrade saddle with enough plastic trimmed away for the wheel to fit OK. Took the spring & filter retainer from My Mk20 so I'll have to find those parts but I'm ready for the FGB. Heck, if I can find a couple more din wheels (knobs), I could probably convert a few more.

 

[halocline]

That's excellent news about the DIN fitting. I have a plastic wheel and a universal retainer, but not the internals. (spring, filter retainer) I wonder if I can get those separately.

 

[captain]

Just buy a cheap used diaphragm 1st stage and you can ajust any IP you want.

 

[AquaNSun]

Initially, I had the same thought as Couv that the piston would float back and forth and damage my mk2 seat in doing so without a spring. The piston did move actually but visually I couldn't tell as the movement was soooo small, in micron I think! I didn't understand so I shut off the tank, purged my 2nd, then opened up a LP port and turned on the tank slightly and there I heard the air rushing out of the orifice. My thought - the downstream force did push the seat off when I
purged my reg! It just happened that the movement was so small and the valve looked closed.

Looking at my data, 5 psi was still good enough for the piston to close the valve, lower limit. So Im guessing in a balanced piston, as little as 5 psi pushing on the piston head could theoretically shut the valve as well. It didn't matter if the tank was at 3000psi or 300psi, the valve will be shut off as soon as the IP chamber gets up to 5psi. So if someone was trying to breath from a 5psi reg, near vacuum, he/she would certainly not getting much air.

 

[halocline]

So if someone was trying to breath from a 5psi reg, near vacuum, he/she would certainly not getting much air.

Well, it's 5psi (or whatever) over ambient, so it's not a vacuum. Remember you have ambient pressure pushing on the ambient side of the piston head.

But, your point is correct, it would apparently be difficult or impossible to breathe off the BP reg with no spring.

 

[AquaNSun]

It's indeed over ambient pressure. Thanks for the correction. And time to hit the bed now!

 

[duckbill]

That's assuming you wouldn't just be sucking water in from a different 2nd stage, i.e. through a seat saver.

Isn't a 'seat saver' that dealie that holds the purge valve down to relieve pressure on the 2nd stage seat during storage?

 

[halocline]

Isn't a 'seat saver' that dealie that holds the purge valve down to relieve pressure on the 2nd stage seat during storage?

There are some like that, my R190 has one. But there are others that work internally, either through a spring washer in the orifice (atomic, I think) or a balance chamber (S600?) that separate the 2nd stage seat from the orifice whenever the reg is not pressurized.