Open the valve, pushing purge button?
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There is no reason to do this,,,,just crack the tank valve slowly and all will be well!
Some don't know *** they are talking about. As a practice, it won't hurt but it doesn't replace the need to open the valve slowly.
Opening the valve slowly helps. Having the purge button pressed when opening the valve helps save the seats from getting slammed by the orface when the reg is pressurized. This will help save the seats a bit but is not totally necessary. Its a step that can't hurt.
I've heard this before. After working in the islands as well as the cold, high altitudes and opening thousands of valves with regs attached the only issue I've come across is a bad o-ring on the tank. But then again that doesn't mean nothing will happen. But the odds are quite low to almost nil. Having said that, it doesn't hurt to check to see if the purge is working properly.
However, I do recommend opening the valve slowly as stated above.
Chris
However, I do recommend opening the valve slowly as stated above.
Chris
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Only if you use an upstream regulator. Do you use an upstream regulator? Which one?
Greg Barlow
Contributor
It does lessen the shock to the first stage valve assembly. In both piston and diaphragm desigs, the hard and soft seats are separated by spring tension when the reg is not pressurized. Upon initial pressurization, the parts "lock" together within milliseconds. Because they were at maximum separation prior to pressurization, there is a "hammering effect" that occurs.
When you have the purge button depressed it somewhat lessens the hammering effect as the pressure cannot build as rapidly. Opening the valve very slowly also accomplishes the same thing, but many valves have coarse threads. This can make it difficult to pressurize the valve slowly.
You barely need to depress the purge button, and the amount of lost gas is very small.
Greg Barlow
When you have the purge button depressed it somewhat lessens the hammering effect as the pressure cannot build as rapidly. Opening the valve very slowly also accomplishes the same thing, but many valves have coarse threads. This can make it difficult to pressurize the valve slowly.
You barely need to depress the purge button, and the amount of lost gas is very small.
Greg Barlow
I's good practice to have the purge button slightly depressed for the reasons Greg mentions above.
Turning the valve on slowly is not really adequate as some valve go from off to an awful lot of pressure in a very short turn of the valve.
When you get into high percentage O2 nitrox mixes, that habit of depressing the purge every time you turn on the reg will serve you well as scuba valves in general are not dsigned for O2 service (they come on very rapidly) and the rapid compression that occurs in both the valve and first stage can in some cases generate enough heat to cause ignition of any available fuels in the high O2 atmosphere inside the valve and first stage.
As an aside, you never really heard the "depress the purge when you turn on the reg" advice until the advent of nitrox so I suspect it has generalized from there.
Even though death and dismemberment will not occur when slamming open the valve on a fully closed reg with your tank of air, it is none the less sound advice to both open the valve slowly and depress the purge slightly. As Greg indicates, you do not need an annoying gas wasting full blown several seconds long purge, rather just a slight purge for a half second or so to let the pressure rise more slowly and to allow the seat and orifice to meet from a much shorter working range.
It is I think one of those "best practices" that separates the knowledgeble/thoughtful divers from the wannabees.
Turning the valve on slowly is not really adequate as some valve go from off to an awful lot of pressure in a very short turn of the valve.
When you get into high percentage O2 nitrox mixes, that habit of depressing the purge every time you turn on the reg will serve you well as scuba valves in general are not dsigned for O2 service (they come on very rapidly) and the rapid compression that occurs in both the valve and first stage can in some cases generate enough heat to cause ignition of any available fuels in the high O2 atmosphere inside the valve and first stage.
As an aside, you never really heard the "depress the purge when you turn on the reg" advice until the advent of nitrox so I suspect it has generalized from there.
Even though death and dismemberment will not occur when slamming open the valve on a fully closed reg with your tank of air, it is none the less sound advice to both open the valve slowly and depress the purge slightly. As Greg indicates, you do not need an annoying gas wasting full blown several seconds long purge, rather just a slight purge for a half second or so to let the pressure rise more slowly and to allow the seat and orifice to meet from a much shorter working range.
It is I think one of those "best practices" that separates the knowledgeble/thoughtful divers from the wannabees.
tonka97
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cool_hardware52
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Yes. O2 fires have started upon opening the valve on O2 scuba bottles. A couple years ago a dive boat in out of the UAE burned to the water line as the result of an O2 fire.
Were they caused by opening the valve to fast? Hard to say, not much left to examine.
Safe handling of O2 is a matter of taking all practical precautions.
Tobin
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