To purge or not.

[eponym]

What I was taught was this:

Open the second stage with the purge valve, then slowly crack open the tank valve. As pressure builds and air starts to flow, release the purge valve. This avoids unnecessary wear on the second stage's needle seat.

If you've not seen the inside workings of a second stage I recommend you arrange to do so at a local shop. It's a quite simple mechanism and you'll see immediately what I'm talking about.

-Bryan

 

[Hatul]

Sorry if this has been asked before, I have an Atomic B3 reg set. I have been told to slightly hold the purge button open when
opening my tank valve. I have also been told it makes no difference,well purge or not?

I'm curious about the Atomic B3. Is this a new model?

 

[Linedog]

Sorry, I somehow got B3 stuck in my head and still call it a B3 now and then.

 

[knowone]

Did B1 and B2 get together?

 

[lxchin]

this practise does make a difference with piston designs. If u are a slow tank opener then u should be safer, but if not, best to open the purge when turning on the tank. My collegue instructor had to get his 1st stage fixed due to that problem.

 

[Akimbo]

The objective is not to hammer any of the first or second stage seats by rapid pressurization in order to extend their useful life. Piston first stages are a little more susceptible than diaphragms, but it is still a good idea to pressurize all regulators slowly — diving, medical, or industrial.

Holding the purge or slowly cracking the cylinder valve servers the same purpose. It probably does not matter for casual divers that service their regulators every few years because seats are routinely changed and can handle a lot of abuse. Evidence of rapid pressurizing can show on regulators that are used a lot, like tropical rental fleets, but they rarely leak between service intervals. I rate this precaution as good practice, but not dangerous if ignored.

The exception here is pure Oxygen!
This is of particular concern in manifolded installations like HP Nitrox mixing and industrial applications. Rapid pressure changes can cause particles inside improperly cleaned and maintained systems to rapidly accelerate to the speed of sound and reach ignition temperatures. That is why it is dangerous to install ball valves in Oxygen systems.

 

[Hank49]

If the reason behind that procedure is to prevent the first stage piston from slamming into the hp seat, then it probably makes no difference provided you open the tank valve slowly (as you should.) Why does it not make a difference? Because when you first open up the tank valve the air is slowly pressurizing an "empty" regulator and set of hoses that act to dampen pneumatic pressure.

Of course the reason could be for something totally different; I would be interested to hear it.

Cheers,

c

Edit after reading the following post #7: I agree it will not harm anything; however, I feel it isn't necessary.

It's hard to open a tank slow enough to get the same affect as purging and slowing releasing.

 

[Splitlip]

Scuba Equipment Care and Maintenance by Farley/Royer ©1988 page 64 "Mounting a Regulator to a Tank"

4) With the second(sic) stage mounted to the tank valve securely, depress the purge button, then turn the air on slightly and listen for any escaping air to build, then release the purge button and open the valve slowly.


There's no explanation for why this is recommended. I've gotten into the habit of doing it, maybe because Charlie Royer was a friend, and I don't see how it could hurt anything.

I open slowly, but instead of purging (as we did before BC's), I press my inflater. Why waste the gas, LOL?

And as for the quote above, I prefer to attach the first stage to my valve.

 

[sevo]

The exception here is pure Oxygen!
This is of particular concern in manifolded installations like HP Nitrox mixing and industrial applications. Rapid pressure changes can cause particles inside improperly cleaned and maintained systems to rapidly accelerate to the speed of sound and reach ignition temperatures. [/QUOTE]

Resulting in an adiabatic explosion, a truly catastrophic event.

 

[Splitlip]

Yup.
I thought we were in basic forum.