press purge button when opening tank valve?

[Hank49]

I don't get it. When I open my tank valve slowly, I can clearly hear air entering the hoses for at least two seconds. During this time the hoses all stiffen up.

The fact that air is flowing through the LP ports means that the HP seat isn't engaged, right? What would forcing *more* air through the LP ports do for you?

Wouldn't the only hose to "stiffen be" the hp? If air entered the lp hoses when opening the valve it would blow them I would think. It only can enter if the purge is pressed or you're sucking air.....or if your hp seat is leaking..a slight hiss after about 2 seconds.

 

[Spectre]

How else does gas get from the first stage to the second stage?

 

[Mick_O]

When I open tank valves (only 63's and 80's so far), I clearly hear air hiss into the HP hose, as well as the LP inflator AND the regulator hoses (regulators don't swivel as easily on the hoses anymore). Does that still mean that the HP valve will slam open and then slam shut?

 

[Hank49]

When I open tank valves (only 63's and 80's so far), I clearly hear air hiss into the HP hose, as well as the LP inflator AND the regulator hoses (regulators don't swivel as easily on the hoses anymore). Does that still mean that the HP valve will slam open and then slam shut?

You're right. It will enter the hoses until the intermediate pressure reaches..uhhh correct me on this..9 bar or so (125 psi) then the piston closes off the air until you press the purge or suck on the reg.

 

[jonnythan]

Then as long as you open slowly, purging the reg does nothing.

 

[matt_unique]

For large tanks, I just open it slowly...

For small tanks like 40s, I can never get it to open very slowly, so I try, but I keep the reg purged so that I'm covered if I fail.

Some tank valves are hard to open and they seem to blast on or shut off with no in between. I can always ensure a slow pressurization in my first stage when I keep the 2nd stage purge button pressed then release slowly.

--Matt

 

[nwdiver2]

It gets changed yearly with the servicing of the reg, so I don’t see how the average divers 30-50 times a year hitting the purge will help. Plus you are dumping 130-150 psi and hitting the seat with 2750-3500 psi and it has to go past the seat to get out so whats the point. Opening it slowly may help. In the past with 500+ dives in a year having the regs serviced after 150 dives I’ve never had a HP seat failure nor a very grotty looking one on the regs I serviced for myself.

It this a one for a new forum "Scuba Myths" ????

 

[Night Diver]

Perversely it seems like opening the valve without purging may be "safer," since if I am going to have a HP seat failure I'd rather have it happen on the boat or in the parking lot than 100 feet down. Seems like if it's going to go that day it would be more likely to go when the air first hits it than any other time.

 

[jonnythan]

Don't do it when it's really cold out either

 

[Boogie711]

It gets changed yearly with the servicing of the reg, so I don’t see how the average divers 30-50 times a year hitting the purge will help. Plus you are dumping 130-150 psi and hitting the seat with 2750-3500 psi and it has to go past the seat to get out so whats the point. Opening it slowly may help. In the past with 500+ dives in a year having the regs serviced after 150 dives I’ve never had a HP seat failure nor a very grotty looking one on the regs I serviced for myself.

It this a one for a new forum "Scuba Myths" ????

OK - I don't know what you're doing, I would think that someone with "500+ dives in a year" would realize there is NO WAY you can be dumping 150 psi by keeping the purge button open for the two seconds it takes to open the valve. On an AL80 that's over 3cf of gas - come on.

I don't mind mulling over a valid reason why it's a bad idea - but that can't be one of them.