How To Open The Tank Valve

[Couv]

When teaching students how to help each other gear up...

I taught students that I liked to help their buddy put on his/her equipment first. That way, the buddy would be the one struggling with all of the weight and gear on while returning the favor.

Re the OP's question. I've heard the "hold the purge" theory before, but it does not make sense as intermediate pressure (IP) closes the first stage valve. If you want to take a precaution: Slowly crack open the tank valve and pause just long enough for the regulator system to pressurize. If something is going to pop, blow, or leak it will be at this moment. The short pause allows you to quickly shut off the valve if need be.

 

[boulderjohn]

Padi is not teaching fin pivot anymore?

Not for many years--I don't remember when they ended it.

Now, you CAN still do it. You are supposed to do an exercise of your choosing that teaches the relation of buoyancy and breathing, but they do not call it a fin pivot. You can do something along the lines of a fin pivot, and you can even do the fin pivot, but they hope that by not naming the exercise and by instead naming the concept to be taught, the instructor will not obsess on a useless perfect fin pivot form. (This was explained to me quite some time ago by a member of PADI HQ.)

Last year I was in Akumal for a vacation, and I watched portions of the local PADI instructors doing the OW class. They were not using the "new" standards--which were then about 6 years old.

 

[ToneNQ]

Padi is not teaching fin pivot anymore?



I learned( also from a CD) that it will increase the lifetime of first stages.
Because when turning the pressure on and it has no place to go. The air will hit the first stage and create heat in that point.
This heat is less, when some air can escape through a 2. Stage.

I am sure its not necessary, but its not harmful aswell. And for me it sounds plausible.

I would suggest that Boyle's Law and Charle's Law are pretty clear on this topic, as the pressure drops the volume increases, and therefore the temperature must drop as the air flows through the HP valve. If the idea is that rapidly stopping airflow generates heat, its actually flow that generates friction. Perhaps the suggestion is the heat generated from the flow through the tank valve is now trapped behind the HP seat, but the distance traveled is a few millimetres and the volume of air is miniscule when the tank is full to not generate any measurable heat. Maybe the idea is that opening the valve slowly makes the cooling process adiabatic, but if that were the case then regs would not freeze in cold water diving without heating fins.

Its certainly not harmful, but you'd need to servicing your own regs at long intervals to get value from any increase in life for the HP poppet valve. I'll wait nervously to be slapped down by one of the scientists, but that is my understanding of this.

If your CD was like my old CD, good at sales, good at diving, had the courage to try to eek a living from it, really hadn't learned anything new about diving since he was a DM. Especially in old PADI, pre TecRec, my experience was there was nothing else to learn about diving. Everything from IDC is/was about the business of diving and the method of instruction.

The SPG bourden tube failure, that took on a life that was both undeserving and unrelenting.

 

[TMHeimer]

And I was taught it by a PADI Course Director who had been himself taught it by a PADI Course Director, but it is nowhere taught officially by PADI.

That same PADI Course Director was the first person I DM'd for, and he came up with a bright idea of his own. When teaching students how to help each other gear up while standing beside the pool, which he scheduled right before the giant stride entry, he realized that if they put their fins on in the correct order (with the figure 4 technique holding onto the buddy's shoulder), they would end up facing the pool, ready for the giant stride. Before long, it became a required step in the process, and people not doing it were not doing the skill correctly. Since he was the director of instruction for the shop, before long all instructors were requiring students to put their fins on in that order. When I became an instructor, I realized it was stupid, because divers gearing up that way are not likely to be on the side of a pool preparing to do a giant stride, and they had to face each other for a buddy check anyway.

Decades ago agencies wanted to teach students that inhaling made them more buoyant and exhaling made them less buoyant. They wondered how best to do that, and the fin pivot was born. That was its only purpose, because it is not something you ever actually do on a dive. Well, instructors all over the world made it an art form, with elaborate rules (knees locked, fin tips on the floor at ALL times, never touch the floor, arms folded, etc.). What was supposed to be a simple little learning exercise became the hardest skill in the OW class. That is why PADI eliminated it years ago--it had become the Frankenstein's monster of scuba instruction.

I am sure many people can tell you stories of things that are taught in scuba classes that are not true and have never been a part of official agency instruction--the most famous being, of course, "if you put your mask on your forehead, a DM will assume you are panicking and will leap in to assist you."

Agree with everything you say. But I didn't say I thought the Course Director was teaching it because it was taught officially by PADI. Another thing he showed us was how to quickly don the unit when alone and needing to do a rescue. I doubt that's officially taught by PADI either (it's not in the manual anyway) but I do it for every dive.

 

[boulderjohn]

Especially in old PADI, pre TecRec, my experience was there was nothing else to learn about diving. Everything from IDC is/was about the business of diving and the method of instruction.

I recently heard a long time PADI CD say that through the 1970's, all agencies firmly believed that everything you really needed to know about scuba was in the OW class as it was taught by all agencies. There was no real need to teach anything more. This was all before tech diving and all the other stuff we know about now.

 

[rob.mwpropane]

Just open gently. And if you are opening an oxygen cylinder, open VERY gently.

I try to remember to treat all tanks like O2, that way when it is O2 it's just 2nd nature to open sloooooow...

 

[Bob DBF]

I would suggest that Boyle's Law and Charle's Law are pretty clear on this topic, as the pressure drops the volume increases, and therefore the temperature must drop as the air flows through the HP valve. If the idea is that rapidly stopping airflow generates heat, its actually flow that generates friction.

The pressure in the reg is at atmospheric pressure, as you rapidly open the valve, the reg shuts flow to the second stage when IP is reached, then the reg is pressurized from 125# to 3000# instantaneously generating heat in the reg.

A search on dieseling will describe what can happen when high pressure is rapidly dead ended with a fuel, say lubricant, present. Another reason to slowly pressurize high pressure lines. The s**t is dangerous.

 

[ToneNQ]

The pressure in the reg is at atmospheric pressure, as you rapidly open the valve, the reg shuts flow to the second stage when IP is reached, then the reg is pressurized from 125# to 3000# instantaneously generating heat in the reg.

A search on dieseling will describe what can happen when high pressure is rapidly dead ended with a fuel, say lubricant, present. Another reason to slowly pressurize high pressure lines. The s**t is dangerous.

Anyone using a flammable lubricant in a regulator should rethink their servicing. Tribolube and Cristolube are ideal. The simple observation is you feel the heat in a tank when you're filling it, but have you ever felt a regulator even vaguely warm. If the heat is generated you simply have to be able to feel/measure it on the regulator body at some point. The 1st stage internal volume limits the heat you can generate. Its interesting, do you have an observed instance where this has occurred?

Key differences with dieseling are the compression occurs in large volumes, with a highly volatile fuel, in an engine that is already hot. Everything is hot, the air is compressed and the flash-point of the fuel is reached. If the fuel is a lube paste, flash point is not relevant and the auto-ignition temperature of lubricants is quite high. Hydraulic dieseling is a very different scenario to this. Is there another dieseling that I have missed? I spent a chunk of my career in heavy plant maintenance, so haven't dealt with dieseling since I was an apprentice working on old beaters.

I turn mine tank valves on slowly, but I'm a long way from convinced it matters.

 

[rob.mwpropane]

Anyone using a flammable lubricant in a regulator should rethink their servicing. Tribolube and Cristolube are ideal. The simple observation is you feel the heat in a tank when you're filling it, but have you ever felt a regulator even vaguely warm. If the heat is generated you simply have to be able to feel/measure it on the regulator body at some point. The 1st stage internal volume limits the heat you can generate. Its interesting, do you have an observed instance where this has occurred?

Key differences with dieseling are the compression occurs in large volumes, with a highly volatile fuel, in an engine that is already hot. Everything is hot, the air is compressed and the flash-point of the fuel is reached. If the fuel is a lube paste, flash point is not relevant and the auto-ignition temperature of lubricants is quite high. Hydraulic dieseling is a very different scenario to this. Is there another dieseling that I have missed? I spent a chunk of my career in heavy plant maintenance, so haven't dealt with dieseling since I was an apprentice working on old beaters.

I turn mine tank valves on slowly, but I'm a long way from convinced it matters.

Do you feel the same about O2 tanks? "turn mine tank valves on slowly, but I'm a long way from convinced it matters". I'm honestly curious if you think it matters.

I've never felt a regulator get warm, but to me it makes sense to turn slow as opposed to fast. Gives a little time for everything to expand / react / adjust for the added pressure, and maybe ourselves a split second to quickly turn things off should something pop.

 

[Miyaru]

There's absolutely no reason whatsoever to open an oxygen tank slowly.

....except when there's oxygen in the tank