Tanks

[NAM001]

I dont understand this discussion of lp vs hp tanks . a hp 120 holds the same as a lp 120. You have to talk apples and apples. With all that being the same the lp is a larger tank. A little more drag and weight. The larger the working psi the more stress on the tank material so lp will have perhaps less stress on it for the same thickness walls. You can always find someone to over fill an LP tank, many times unknowingly as they treat it like another al 80 and fill to 3200 and cool to 3k. If you have problem with a shop that will not fill an LP tank over 2640 hot and wont top off when cool, rent a al80 or HP tank and buy a transfer whip to top off with. Preferably a HP because it is a 3442 with probably 3200 in it. We all deserve a full fill.

 

[kwinter]

The OP might be needing this info. Yolk regulators and valves are only rated for 3500 psi. If pressures are more then that, you must go DIN. Just another reason cavers use DIN.


Sent from my iPhone using Tapatalk

Here we go again.......

1. It's YOKE, not YOLK. It has nothing to do with eggs.

2. Yoke attachments are good to 3442 psi, not 3500. That's why true HP 3500 tanks have 300 bar DIN valves that can not be converted to yoke, while newer HP tanks are marked 3442 and can use convertible 200 bar DIN valves.

3. Cave, tech and rebreather divers use DIN for reasons that have absolutely nothing to do with pressure. Very few would ever be using tanks with more than 3442 psi.


iPhone. iTypo. iApologize.

 

[00wabbit]

I dont understand this discussion of lp vs hp tanks . a hp 120 holds the same as a lp 120. You have to talk apples and apples. With all that being the same the lp is a larger tank. A little more drag and weight. The larger the working psi the more stress on the tank material so lp will have perhaps less stress on it for the same thickness walls. You can always find someone to over fill an LP tank, many times unknowingly as they treat it like another al 80 and fill to 3200 and cool to 3k. If you have problem with a shop that will not fill an LP tank over 2640 hot and wont top off when cool, rent a al80 or HP tank and buy a transfer whip to top off with. Preferably a HP because it is a 3442 with probably 3200 in it. We all deserve a full fill.

You can't always find someone to overfill low pressure tanks. I spent a week in key largo with my lp tanks. I went to various shops for fills and no one would go over the ratings. Apparently a dot inspector caught a shop down there overfilling and fined them big when it happened. So now they are all reluctant especially of you are just walking in for the first time asking for it. Maybe if it's your local shop and they know you they will do it but if you are planning to travel with your tanks to anywhere other than cave country then you can't count on overfills.

I think the lp vs hp issue is that and hp100 holds 100cuft and not more because it's difficult to fill past hp pressure. An lp 85 on the other hand will hold 112cuft if filled to 3500psi and will still be a similar size and diameter to an hp 100. This is why a cave diver may choose the smaller lp tank. They can cram more air into a smaller package and squeeze through smaller holes.

I think ink also you should consider the bouyancy characteristics of the tank. If you need to carry a lot of lead because you are more buoyant then maybe choosing and hp tank is better because they are more negative than lp tanks and you can remove some lead.

 

[kwinter]

I think the lp vs hp issue is that and hp100 holds 100cuft and not more because it's difficult to fill past hp pressure. An lp 85 on the other hand will hold 112cuft if filled to 3500psi and will still be a similar size and diameter to an hp 100. This is why a cave diver may choose the smaller lp tank.

I think you're almost right. For me the bigger issue is that a HP100 only holds 100cf at 3442 or 3500 psi, and a true HP fill might even be harder to get than a cave fill on a LP tank. The LP85 only needs to be overfilled to 3100 to hold 100cf. That might be easier to get than a real 3500 psi fill.


iPhone. iTypo. iApologize.

 

[Redshift]

A lot of people push lp tanks because they overfill them (normal fill pressure is 2640 and they fill to 3200-3500)

Weird, those are your filling pressures? On this side of the pond, our low pressure steels, which are the most used at the moment, have a work pressure of 230 bar (3336 psi), although usually we end up with slightly less than that, unless we top off after it's cooled down (and depending on the pressure relief valves on compressors because some are set to just over 200 bar since Al tanks have work pressure of 207 bar - 3002 psi). These tanks usually have 200 bar DIN convertible valves so both yoke and DIN regs work.
Our high pressure steels have a working pressure of 300 bar (4351 psi). With these tanks only 300 bar DIN valves and regulators.

 

[00wabbit]

Weird, those are your filling pressures? On this side of the pond, our low pressure steels, which are the most used at the moment, have a work pressure of 230 bar (3336 psi), although usually we end up with slightly less than that, unless we top off after it's cooled down (and depending on the pressure relief valves on compressors because some are set to just over 200 bar since Al tanks have work pressure of 207 bar - 3002 psi). These tanks usually have 200 bar DIN convertible valves so both yoke and DIN regs work.
Our high pressure steels have a working pressure of 300 bar (4351 psi). With these tanks only 300 bar DIN valves and regulators.

Yep - Normal LP tanks are rated to 2400psi with a 10% overfill allowed if they are plus rated. This brings then up to 2640psi
Normal HP tanks are either 3442 or 3500psi

The generic aluminum 80 that everyone learns on and is the standard tank in the rental fleets of every dive shop is rated to 3000psi.

 

[Bob DBF]

Here we go again.......

1. It's YOKE, not YOLK. It has nothing to do with eggs.

2. Yoke attachments are good to 3442 psi, not 3500. That's why true HP 3500 tanks have 300 bar DIN valves that can not be converted to yoke, while newer HP tanks are marked 3442 and can use convertible 200 bar DIN valves.

3. Cave, tech and rebreather divers use DIN for reasons that have absolutely nothing to do with pressure. Very few would ever be using tanks with more than 3442 psi.


iPhone. iTypo. iApologize.

1. Don't you love automatic spellcheck, unfortunately most folks on the internet don't ever read or check what they write at all.

2. I still have, and use, a yoke reg made in the late '70's that was built for 4000# service. I have used my current yoke reg on tanks with over 3500# tank pressure. I wouldn't try that with any, but one, of my vintage regs because the yokes were made for 3000#, or less, service. In the same fashion, 300 DIN regulators have been made for a long time and the older regulators may not be able to physically stand the higher pressure.

Let's face it, yoke has been around a long time and until a very large percentage of the tank valves in rental and personal fleets are convertable or DIN, there will not be a good reason for any changeover.
Tank pressure is a red herring.

3. Agreed, but they would if they got a HP tank with 3600# in it.


Bob
---------------------
I may be old, but I'm not dead yet.

 

[The Kraken]

HP 100's are a dream to dive. Smaller than an LP 80 and lots more gas. Additionally you can take about 4 pounds from your weight belt because of the buoyancy characteristics of the HP tanks.

Safe dives . . . . . .
. . . safer ascents !

the K

 

[84CJ7]

Just to clarify since it has been somewhat talked around, I see 2 big advantages to DIN over yoke that are not pressure limit related.

1. Captive O ring. Most yokes can handle anything you can put in a tank metal wise, but the way the O ring is squashed between the sealing face of the regulator and the tank is less than ideal for reliability and gets worse the higher the pressure gets. With the DIN design the O ring is trapped in a metal space all the way down inside the tank valve when the regulator is attached.

2. Smaller regulator. If you look at the same regulator in a picture with a yoke and din, you will see that the DIN valve only sticks out in one direction from the valve (towards the diver). The big knob on a yoke regulator sticks up above the tank valve, and if you are a cave or wreck diver makes a wonderful place to hang up on everything. Technically the tank is usually wider than the valve, but something banging the tank will follow the curve and usually go right up over whereas the yoke valve seems ideally suited to snag on lines, cables or overhead edges with its 90 degree angle and mushroom head.

On the other topic of HP vs LP sizes I tend to not notice underwater as I am tall so a shorter tank doesn't make any difference to me and the difference in diameter is usually pretty tiny.

 

[Michael Guerrero]

HP tanks are more compact for a similar amount of gas, which may not be great for you depending on your body type. If you're tall, small HP100s may be more difficult to trim out, necessitating longer and heavier HP steel tanks.