How many here were scared to death and still completed OW classes?

[MJS1946]

As a newb, I have a newb question on max vs fill pressure. Is this somewhat dependent on the equipment used to do the fill? Are some not capable of filling to max PSI?

Thanks

 

[almostDIR]

As a newb, I have a newb question on max vs fill pressure. Is this somewhat dependent on the equipment used to do the fill? Are some not capable of filling to max PSI?

Thanks

there may be some old/travel compressors which could not do max psi but it is more of a problem with the gas in the tank warming up when filling (gas expanding due to temperature) and when it cools down the pressure drops. The compressor output does not need to be overly warm, the temperature rise happens more of because of the pressure change in the tank. If you want to have the max pressure in the tank AFTER it has cooled down you need to either fill it multiple times cooling it down after each fill so that more gas can be added, OR you have to seriously overfill it like LOTS of overpressure so that when it cools down it drops to the pressure you will want to have in the end.

basically you will either wait more and fill the same tank multiple times to get a good fill pressure in the end OR seriously overfill and stress the tank more and maybe shorten its lifetime on every fill

 

[NAUI Wowie]

As a newb, I have a newb question on max vs fill pressure. Is this somewhat dependent on the equipment used to do the fill? Are some not capable of filling to max PSI?

Thanks

Im new but ill take a crack at this as ive just bought some tanks and researched it. In the USA steel high pressure tanks should be filled to 100% or 3442 psi.

Aluminum tanks if still within testing approval can be filled to 110% or plus ten percent which is normally around 3200ish?

at least thats what I believe ive found to be true here

 

[JackD342]

Im new but ill take a crack at this as ive just bought some tanks and researched it. In the USA steel high pressure tanks should be filled to 100% or 3442 psi.

Aluminum tanks if still within testing approval can be filled to 110% or plus ten percent which is normally around 3200ish?

at least thats what I believe ive found to be true here

That is a little over simplified, and a little reversed. Ignoring over fills and speaking just for service pressure, there are many steel cylinders that can legally be filled to 10% over the stamped service pressure, if they have been tested for it and stamped with the “+” at the last hydro. If not, then only the service pressure is allowed by DOT. To my recollection, I have not heard of a +10% aluminum protocol. Most current aluminum cylinders are 3000 psi SP. An aluminum AL100 or a Neutral 80 is usually 3300, but that is NOT a +10% SP.
3442 is a very common current HP steel SP, and again is not a +10% protocol cylinder. An example of a +10% tank is one stamped 2400+, which can be filled to 2640 if the “+” hydro test is done and stamped.

 

[NAUI Wowie]

That is a little over simplified, and a little reversed. Ignoring over fills and speaking just for service pressure, there are many steel cylinders that can legally be filled to 10% over the stamped service pressure, if they have been tested for it and stamped with the “+” at the last hydro. If not, then only the service pressure is allowed by DOT. To my recollection, I have not heard of a +10% aluminum protocol. Most current aluminum cylinders are 3000 psi SP. An aluminum AL100 or a Neutral 80 is usually 3300, but that is NOT a +10% SP.
3442 is a very common current HP steel SP, and again is not a +10% protocol cylinder. An example of a +10% tank is one stamped 2400+, which can be filled to 2640 if the “+” hydro test is done and stamped.

Interesting but im definitely not talking low pressure. So you are saying that the steel H.P. tanks can safely be filled over the 3442 rating? I need to know because I just purchased two steel tanks and if I can go ten percent over the 3442 thats great information.

 

[JackD342]

As a newb, I have a newb question on max vs fill pressure. Is this somewhat dependent on the equipment used to do the fill? Are some not capable of filling to max PSI?

Thanks

Several variables:

• Capacity of the compressor
• Service pressure of the bank bottles
• Ease or willingness of fill station operator to adjust the fill station flow regulator up then back down

My compressor is over 30 years old, and while it is maintained I am hesitant to run it over 3500. Also, most of my banks are 3600 max, so I can’t bank too high anyway. I have a couple of customers with 3442 tanks, but if they stop in when the highest bank is a little low they may have to leave it overnight.

 

[JackD342]

Interesting but im definitely not talking low pressure. So you are saying that the steel H.P. tanks can safely be filled over the 3442 rating? I need to know because I just purchased two steel tanks and if I can go ten percent over the 3442 thats great information.

Over fills (cave fills) are commonly discussed on SB, and I gather usually far exceed 10% over the service pressure. I have only described to you what is legal in an attempt to educate. I do not personally engage in disussion of relative safety for anything higher, nor do I fill cylinders any higher. I will never convince an overfill proponent to change their mind and agree with me, and they would never convince me to agree with them.

 

[NAUI Wowie]

Over fills (cave fills) are commonly discussed on SB, and I gather usually far exceed 10% over the service pressure. I have only described to you what is legal in an attempt to educate. I do not personally engage in disussion of relative safety for anything higher, nor do I fill cylinders any higher. I will never convince an overfill proponent to change their mind and agree with me, and they would never convince me to agree with them.

Yea not wanting to get into any discussion of danger vs practicality. Was just curious. Interesting info on cave fills maybe going higher. Great info and no agendas thanks for the experience conveyed

 

[almostDIR]

Yea not wanting to get into any discussion of danger vs practicality. Was just curious. Interesting info on cave fills maybe going higher. Great info and no agendas thanks for the experience conveyed

I think it is pretty much like playing with the NDL limits, there WILL be some added risk if going over the limits but no one really knows how much more that is and when something bad will happen (if ever) until it does. steel tanks are made a bit elastic so that they can expand a little when filled and shrink a little when the pressure drops. overfilling may affect how many expand/shrink cycles the tank can hold until the metal can't stand it anymore. but as said no one really knows HOW MUCH it affects a certain tank though maybe it could be somewhat measured if hydroing the tank more often than needed.

 

[Kimela]

I just got my OW in Sept. at Mermet, and the thing that still freaks me out are the weekend crowds on those platforms. It social anxiety, low vis. due to the silt, and fear of loosing my buddy/wife among the throngs of students moving across and practicing on those platforms. It's a whole different place this time of year when there are probably only you and a buddy. Much less anxiety for me.

Good to know. I wish I was a cold water diver. I get too chilled, too quickly, and it's just no fun for me. Diving cold water would open up a world of possibilities for me, but I just can talk myself into it. So I get to look at the cool pics and hear the wonderful stories from those who do those chilly dives.