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View Full Version : Why the dislike for AL 100 tanks??



Chilkie
11-16-2009, 19:43
Hello all. I'm a rec diver who owns a couple of my own AL80 tanks which I generally take with me when I dive. I'm not generally the first person back on the boat, but I'm not the last either. I was thinking about buying a couple of AL100 tanks to use figuring that it would give me more air and keep me in the water a little longer.
When I went to research them, it seem that most folks go to steel tanks and some just downright dislike aluminium (one thread I saw had a Bart Simpson icon dropping his pants to Al100 tanks...funny!!).
Anyway, I'm curious as to why AL100's aren't very popular. They seem to be quite a bit less expensive than steel and should be easier to care for.
On a related note, I'm also purchasing a boat and planning on keeping multiple tanks on board to dive with down around the Panama City, FL area. Again, maybe I am missing something but I'm not really sure why steel would be worth more money. Any advice would be greatly appreciated. I'd like to have as much air available not only for myself but also for any friends and guests I have on my boat. Thanks!

WaScubaDude
11-16-2009, 19:51
I would imagine it has to do with the buoyancy characteristics of the tank. Always the issue with Al 80's, but I am sure someone who really knows will pipe in.

FishFood
11-16-2009, 20:04
They are big and heavy compared to a HP steel 100, but still swing to 2-4lbs positive buoyancy. And, unlike an al80, they are not cheap. Be best to spend a little extra cash and go steel.

IndyDiver
11-16-2009, 20:08
As the man from WA says, the buoyancy/weight/size characteristics are not good.

The Luxfer AL100 is 8" in diameter, so it won't fit in many warm water dive boat tank holders. It weights 40 lbs on dry land, and in water is 3lb positive when empty and 4 lbs negative when full. Fill pressure is 3300.

The Worthington (XSScuba) HP100 is a 7.25" tank. It weights 33 lbs on dry land, and in water is -2.5 lb empty and -10lb when full. Fill pressure is 3442, so no real difference there.

Since most people wear weights to get neutrally buoyant, this means on the way to the water you are carying 7lbs more tank and 6lbs more lead with the AL100 than with the HP100.

Nothing really wrong with an AL100, it's just all the specs have a slight downside and there is no real upside.

in_cavediver
11-16-2009, 20:09
Its all in the bouyancy characteristics of the tanks.

A Luxfer 100 wieghs 41lbs empty, is 4lbs negative full and 3lbs positive full. Compare that to a steel 100 that is 33lbs emtpy, -8.5lbs full and -1lb when empty. To achieve tank neutrality - you need 4lbs less weight with the steel tank. Couple that to being 8lbs lighter out of the water and you can translate that into 12lbs less weight to carry out of the water. (assumes you use at least 4lbs of lead weight). Looking at tank weights - that is a third of the weight of the steel 100.

Oh the steel tank is also smaller - 7.25 inches and 24" tall versus 8" in diameter and 26" tall which is more comfortable for many divers.

IndyDiver
11-16-2009, 20:17
Again, maybe I am missing something but I'm not really sure why steel would be worth more money. Any advice would be greatly appreciated. I'd like to have as much air available not only for myself but also for any friends and guests I have on my boat. Thanks!

Once you start looking at steel, there is also the HP119 and HP120 (depending on whether you want a short 8" tank or a longer 7.25" tank), both of which would give you and your friends 20 cuft more air per dive than the AL100 - and neither of them really weighs any more on land.

IndyDiver
11-16-2009, 20:19
Its all in the bouyancy characteristics of the tanks.

A Luxfer 100 wieghs 41lbs empty, is 4lbs negative full and 3lbs positive full. Compare that to a steel 100 that is 33lbs emtpy, -8.5lbs full and -1lb when empty. To achieve tank neutrality - you need 4lbs less weight with the steel tank. Couple that to being 8lbs lighter out of the water and you can translate that into 12lbs less weight to carry out of the water. (assumes you use at least 4lbs of lead weight). Looking at tank weights - that is a third of the weight of the steel 100.

Oh the steel tank is also smaller - 7.25 inches and 24" tall versus 8" in diameter and 26" tall which is more comfortable for many divers.

Beat you by a minute :smiley36:

Chilkie
11-16-2009, 20:55
Thanks gang!. That really makes sense. How much more care do steel tanks require?

FishFood
11-16-2009, 21:11
Thanks gang!. That really makes sense. How much more care do steel tanks require?

Get a dipped galvanized tank and very little. You *may* have an issue at PCB with wet fills. A dive shop down there had a sub ballast bank tank blow this past year; The cause seeming to be moisture causing rust in the tank. Did that translate into wet fills for customers? I don't know. Maybe someone else can chime in on this.

A yearly VIP should allow you cut off any major issues however.

comet24
11-16-2009, 21:46
Al floats, steel sinks. There are other reasons but for most it's really that easy.

mitsuguy
11-17-2009, 00:46
Let me throw one more thing out there too...

AL80 @ 3000 psi = 77.8 cu ft.
AL100 @ 3000 psi = 88 cu ft.

AL100's are rated at 3300 psi, so if your shop doesn't offer higher than 3000 psi fills, you are really only gaining 10 cu ft versus the 20 most think they are getting...

That, plus as everyone has mentioned, the horrible buoyancy, excessive extra weight, and larger diameter that doesn't fit on boats (even our 22 passenger Newton only has 2 spots for 100's), there just isn't much reason to go to AL100's, when for just a few dollars more most places, you can get a steel 100/119/120 and be much happier...

scubastud
11-17-2009, 02:42
Wow... I am glad I happened on this post. If I were Calvin, I would pee on AL100s too.
Last thing I want to do is have to load up with more weights.
When I am ready to buy a tank or two, it will def. be steel.

IndyDiver
11-17-2009, 07:10
Thanks gang!. That really makes sense. How much more care do steel tanks require?

None really. As FishFood says, if you get a galvanized tank, the outside should be just as durable as an aluminum. There are 20 and 30 year old steel tanks out there still going strong.

The inside will rust if moisture gets into the tank, but scuba air is too dry to support rust formation; so the only danger is that water gets in when the fill whip is attached. This is most likely to happen from fills on boats and fills from shops that still use a water cooling tank. In any case, the annual viz will catch any rust before it ruins the tank in any but the most severe cases.

IndyDiver
11-17-2009, 07:15
Let me throw one more thing out there too...

AL80 @ 3000 psi = 77.8 cu ft.
AL100 @ 3000 psi = 88 cu ft.

AL100's are rated at 3300 psi, so if your shop doesn't offer higher than 3000 psi fills, you are really only gaining 10 cu ft versus the 20 most think they are getting...


Ahh, the sad truth of things. I spend a lot of time with 3000-3100 psi in my steel tanks. :smiley13:

So a lot of the time, I have an HP90 and an HP107

dkh6070
11-17-2009, 07:23
I learn every time I log in here. This is great info and most recreational divers do no know this stuff. Thanks to everyone for great information.

Chilkie
11-17-2009, 08:23
I'm really planning on buying 5 or 6 more tanks over time so that I have quite a few for myself and friends. After getting all of this great feedback I think the AL80's are fine for keeping on my boat to use with "the gang" as you can pick them up brand new so inexpensively, but I think that I will pick up a couple of steel HP100's (or maybe even 120's) to utilize myself when I go out on a 2 tank dive charter.
Seems like the way to go.....now I just have to explain to my wife why I will have so many tanks sitting around when I haven't bought my boat yet. :smiley5:

awap
11-17-2009, 08:55
The only down side I found to the steel HP100 I selected over the AL100 is that for warm water diving with my heavy plate (~5lb), I am overweighted by a couple pounds. So, you can either add a little neoprene, like a 3mm shortie; or go for a lighter plate.

in_cavediver
11-17-2009, 10:50
Its all in the bouyancy characteristics of the tanks.

A Luxfer 100 wieghs 41lbs empty, is 4lbs negative full and 3lbs positive full. Compare that to a steel 100 that is 33lbs emtpy, -8.5lbs full and -1lb when empty. To achieve tank neutrality - you need 4lbs less weight with the steel tank. Couple that to being 8lbs lighter out of the water and you can translate that into 12lbs less weight to carry out of the water. (assumes you use at least 4lbs of lead weight). Looking at tank weights - that is a third of the weight of the steel 100.

Oh the steel tank is also smaller - 7.25 inches and 24" tall versus 8" in diameter and 26" tall which is more comfortable for many divers.

Beat you by a minute :smiley36:

Hey - at least we agree!

MSilvia
11-17-2009, 12:41
I think that I will pick up a couple of steel HP100's (or maybe even 120's) to utilize myself when I go out on a 2 tank dive charter.
Seems like the way to go.
Bear in mind that it's not as simple as "Aluminum has crappy buoyancy but steel is good". Different tanks have different characteristics. Just because you might like diving with a HP100 doesn't mean you'll like a different size. It's worth looking at charts of characteristics and talking to people who dive them.

One other point worth considering: Steel tanks tend to have much longer useful lives than aluminium tanks. I'd be hesitant to buy an AL tank that's 15 years old, but I have no reservations about diving an LP steel 72 from the late 60s.

Chilkie
11-17-2009, 14:42
Ya know......the most puzzling thing to me is why the AL80 tanks seem to go for so much when they are used. Even on ebay they tend to be around $65 bucks or more. By the time you add the vis and hydro charges after you get them (and shipping) they cost as much as new tanks would.
Who buys these things??????

Chilkie
11-17-2009, 15:08
Ya know......the most puzzling thing to me is why the AL80 tanks seem to go for so much when they are used. Even on ebay they tend to be around $65 bucks or more. By the time you add the vis and hydro charges after you get them (and shipping) they cost as much as new tanks would.
Who buys these things??????

awap
11-17-2009, 15:09
Ya know......the most puzzling thing to me is why the AL80 tanks seem to go for so much when they are used. Even on ebay they tend to be around $65 bucks or more. By the time you add the vis and hydro charges after you get them (and shipping) they cost as much as new tanks would.
Who buys these things??????

Divers who have shops that are trying to charge $200 for a new one and divers who are patient and find good buys in the local area for AL80s that are still in hydro.

Chilkie
11-17-2009, 16:06
Ya know......the most puzzling thing to me is why the AL80 tanks seem to go for so much when they are used. Even on ebay they tend to be around $65 bucks or more. By the time you add the vis and hydro charges after you get them (and shipping) they cost as much as new tanks would.
Who buys these things??????

Divers who have shops that are trying to charge $200 for a new one and divers who are patient and find good buys in the local area for AL80s that are still in hydro.


My LDS is selling a 10 year AL80 old tank for $160 (includes the hydro and Vis though). Of course, if you pay that and add in sales tax and you are right around $175 for a much older tank.

As Scooby Doo says....Jinkies!!!

CompuDude
11-17-2009, 16:30
Ya know......the most puzzling thing to me is why the AL80 tanks seem to go for so much when they are used. Even on ebay they tend to be around $65 bucks or more. By the time you add the vis and hydro charges after you get them (and shipping) they cost as much as new tanks would.
Who buys these things??????

The uneducated, or desperate, consumer.

"A fool and his money are soon parted."
-Thomas Tusser, 1557

"There's a sucker born every minute."
-David Hannum, circa 1869

MSilvia
11-17-2009, 16:39
Yeah... it's no mystery why people try to charge so much for them. They mystery is why anyone would think that was a good deal.

nrembis
11-17-2009, 16:49
sooner or later a deal pops up...I just bought 16 tanks not too long ago for 40.00 each all have a year and a half left on hydro and vis were still good when i bought them, vis will be due however next spring, but all the tanks were topped off before I brought them home, so will be able to use them before I have to get a vis done.

WD8CDH
11-18-2009, 15:43
I think that I will pick up a couple of steel HP100's (or maybe even 120's) to utilize myself when I go out on a 2 tank dive charter.
Seems like the way to go.
Bear in mind that it's not as simple as "Aluminum has crappy buoyancy but steel is good". Different tanks have different characteristics. Just because you might like diving with a HP100 doesn't mean you'll like a different size. It's worth looking at charts of characteristics and talking to people who dive them.

One other point worth considering: Steel tanks tend to have much longer useful lives than aluminium tanks. I'd be hesitant to buy an AL tank that's 15 years old, but I have no reservations about diving an LP steel 72 from the late 60s.
I have no reservations diving an AL tank made from 6061 alloy regardless of the age. In fact, a non abused 6061 Aluminum tank or steel tank should both outlast out lifetimes. But I prefer Steel over Aluminum in most tank sizes.

RogerAg
11-19-2009, 12:21
I'm really planning on buying 5 or 6 more tanks over time so that I have quite a few for myself and friends. After getting all of this great feedback I think the AL80's are fine for keeping on my boat to use with "the gang" as you can pick them up brand new so inexpensively, but I think that I will pick up a couple of steel HP100's (or maybe even 120's) to utilize myself when I go out on a 2 tank dive charter.
Seems like the way to go.....now I just have to explain to my wife why I will have so many tanks sitting around when I haven't bought my boat yet. :smiley5:

You do know that HP100's use den while AL80's use yoke. You will have to have a second 1st stage or an adapter. Or you can take your first stage apart as I do and replace the Yoke with a den.

FishFood
11-19-2009, 12:34
You do know that HP100's use den while AL80's use yoke.

HP100's can utilize either valve configuration. In fact, ScubaToys' lists their Worthingtons as coming equiped with a yoke valve.

CompuDude
11-19-2009, 13:06
I'm really planning on buying 5 or 6 more tanks over time so that I have quite a few for myself and friends. After getting all of this great feedback I think the AL80's are fine for keeping on my boat to use with "the gang" as you can pick them up brand new so inexpensively, but I think that I will pick up a couple of steel HP100's (or maybe even 120's) to utilize myself when I go out on a 2 tank dive charter.
Seems like the way to go.....now I just have to explain to my wife why I will have so many tanks sitting around when I haven't bought my boat yet. :smiley5:

You do know that HP100's use den while AL80's use yoke. You will have to have a second 1st stage or an adapter. Or you can take your first stage apart as I do and replace the Yoke with a den.

1) DIN, not "den".

2) Most tanks sold today come with a convertible valve that works with both DIN and Yoke valves... including pretty much all current HP100s.

RogerAg
11-19-2009, 15:40
[QUOTE=

1) DIN, not "den".

2) Most tanks sold today come with a convertible valve that works with both DIN and Yoke valves... including pretty much all current HP100s.

My tanks are din only, however I loaned a HP tank to member of my dive club on a club dive. He had a "Tank Valve Converter".

He blow his O-Ring before he even got into the water. :smiley5:

MSilvia
11-19-2009, 16:39
2) Most tanks sold today come with a convertible valve that works with both DIN and Yoke valves... including pretty much all current HP100s.
I think that is (or should be) LP tanks only. HP tanks have a higher service pressure than yoke regs are meant to handle. IIRC, 220 BAR DIN has the converter, but not the 300 BAR. I have trouble believing a responsible manufacturer would put 220 BAR DIN valves on HP tanks... are you sure about that? My HP100s aren't brand new, but they definately don't have convertible DIN valves.

mitsuguy
11-19-2009, 16:44
2) Most tanks sold today come with a convertible valve that works with both DIN and Yoke valves... including pretty much all current HP100s.
I think that is (or should be) LP tanks only. HP tanks have a higher service pressure than yoke regs are meant to handle. IIRC, 220 BAR DIN has the converter, but not the 300 BAR. I have trouble believing a responsible manufacturer would put 220 BAR DIN valves on HP tanks... are you sure about that? My HP100s aren't brand new, but they definately don't have convertible DIN valves.

nope... HP, at least to 3442... Which works just fine with a lot of current regulators... my Tusa is stamped 232 bar service pressure, which, when converted, is almost 3400 psi... so, its less than 100 psi short of most HP tanks... I have used many 3442 psi HP steel tanks with no issue with the yoke valve plug with zero issues... Not saying it's always the correct thing, and of course, a yoke probably wouldn't handle 300 bar, but the tanks aren't rated for it anyways...

MSilvia
11-19-2009, 16:47
2) Most tanks sold today come with a convertible valve that works with both DIN and Yoke valves... including pretty much all current HP100s.
I think that is (or should be) LP tanks only. HP tanks have a higher service pressure than yoke regs are meant to handle. IIRC, 220 BAR DIN has the converter, but not the 300 BAR. I have trouble believing a responsible manufacturer would put 220 BAR DIN valves on HP tanks... are you sure about that? My HP100s aren't brand new, but they definately don't have convertible DIN valves.

nope... HP, at least to 3442... Which works just fine with a lot of current regulators... my Tusa is stamped 232 bar service pressure, which, when converted, is almost 3400 psi... so, its less than 100 psi short of most HP tanks... I have used many 3442 psi HP steel tanks with no issue with the yoke valve plug with zero issues... Not saying it's always the correct thing, and of course, a yoke probably wouldn't handle 300 bar, but the tanks aren't rated for it anyways...
Maybe that's the difference. My HPs are 3500 psi service.

CompuDude
11-19-2009, 17:03
2) Most tanks sold today come with a convertible valve that works with both DIN and Yoke valves... including pretty much all current HP100s.
I think that is (or should be) LP tanks only. HP tanks have a higher service pressure than yoke regs are meant to handle. IIRC, 220 BAR DIN has the converter, but not the 300 BAR. I have trouble believing a responsible manufacturer would put 220 BAR DIN valves on HP tanks... are you sure about that? My HP100s aren't brand new, but they definately don't have convertible DIN valves.

Come on, you know better than that, Matt.

The vast majority of yokes on any reg sold in the past 10 years are rated to 4500psi+. That's from DA_Aquamaster, who I believe you are familiar enough with to trust. There are any number of threads discussing this over the past few years on SB.

ALL current tanks from Worthington (imported by XS Scuba) and Faber (imported by Blue Steel) use convertible valves on their tanks (stock). It's only "true HP" 3500 psi tanks that require DIN-only valves (300 bar), so all of the exemption tanks (3442 is most common, Faber has a couple 3998 tanks!) are allowed Yoke. Worthington's come with Thermo Pro valves (convertible) and Blue Steel (Faber) comes with San-O-Sub convertible valves. (Stock... some dealers may swap things around or special order different ones, but ordinarily, they'd be convertible valves.)

It's true that, the higher the pressure, the more likely a yoke valve (or a convertible valve with the yoke insert in place) will blow an o-ring (just like you can with a 3000psi fill on an Al.80, so where's the difference?), but I know many many local divers that dive them all the time, no problem. DIN is still better, but realistically, Yoke is fine with the pressure of a normal fill.

XS Scuba - Worthington Steel Scuba Cylinder Features (http://www.xsscuba.com/tank_steel_features.html)

Worthington HP100 [TW-HP100] - $365.49 : Tech Diving Limited (http://tdl.divebiz.net/index.php?main_page=product_info&cPath=1_102255&products_id=102725)

HP Steel 100 Scuba Tank High Pressure X7 100 - ScubaToys (http://www.scubatoys.com/store/detail.asp?product_id=X7100)

X-Series Steel SCUBA Tanks by Worthington Cylinders - Dive Gear Express (http://www.divegearexpress.com/gas/steel.shtml)

~~~

Blue Steel Valves (http://www.bluesteelllc.com/valves.htm)

Blue Steel Faber High Pressure Steel Tank - LeisurePro (http://www.leisurepro.com/Prod/CategoryID_962/Context_954/Sort_Stock/DescSort_0/Filter_1%3d2731/FBRHP.html?Hit=1)


(Oddly, I can't find many vendors with a large selection of Faber tanks, even TDL, and Joel has always been one to push Faber hard. I wonder if something is going on with the imports?)

IndyDiver
11-19-2009, 17:05
2) Most tanks sold today come with a convertible valve that works with both DIN and Yoke valves... including pretty much all current HP100s.
I think that is (or should be) LP tanks only. HP tanks have a higher service pressure than yoke regs are meant to handle. IIRC, 220 BAR DIN has the converter, but not the 300 BAR. I have trouble believing a responsible manufacturer would put 220 BAR DIN valves on HP tanks... are you sure about that? My HP100s aren't brand new, but they definately don't have convertible DIN valves.

nope... HP, at least to 3442... Which works just fine with a lot of current regulators... my Tusa is stamped 232 bar service pressure, which, when converted, is almost 3400 psi... so, its less than 100 psi short of most HP tanks... I have used many 3442 psi HP steel tanks with no issue with the yoke valve plug with zero issues... Not saying it's always the correct thing, and of course, a yoke probably wouldn't handle 300 bar, but the tanks aren't rated for it anyways...
Maybe that's the difference. My HPs are 3500 psi service.

All of the yoke regulators I have are stamped either as 232 bar or as 3500psi, depending on the manufacturer.

Every 3442psi HP tank I have seen that was bought new in the last few years has a 200bar convertible valve on it that is good for DIN or yoke. This includes Faber and a couple of makes of rebranded Worthingtons.

The older HP tanks that were made before the current DOT exemptions seem to be mostly rated at 3500 and came with 300bar non-convertibel valves.

IndyDiver
11-19-2009, 17:10
(Oddly, I can't find many vendors with a large selection of Faber tanks, even TDL, and Joel has always been one to push Faber hard. I wonder if something is going on with the imports?)

Northeast Scuba Supply, which also seems to push Faber tanks a lot, has a large selection in stock on their website.

Tanks - Faber Diving Cylinders - Northeast Scuba Supply (http://northeastscubasupply.com/store/tanks/faber-diving-cylinders/cat_86.html)

In general, I have always found the Faber tanks much rarer than the Worthingtons.

IndyDiver
11-19-2009, 17:14
The vast majority of yokes on any reg sold in the past 10 years are rated to 4500psi+.

Did you really mean to type 4500?

CompuDude
11-19-2009, 17:16
(Oddly, I can't find many vendors with a large selection of Faber tanks, even TDL, and Joel has always been one to push Faber hard. I wonder if something is going on with the imports?)

Northeast Scuba Supply, which also seems to push Faber tanks a lot, has a large selection in stock on their website.

Tanks - Faber Diving Cylinders - Northeast Scuba Supply (http://northeastscubasupply.com/store/tanks/faber-diving-cylinders/cat_86.html)

In general, I have always found the Faber tanks much rarer than the Worthingtons.

Good find. Funny, though, how the cheap SOBs are selling the valves separately. Makes the price look better than it is. LOL

RogerAg
11-19-2009, 17:18
Maybe that's the difference. My HPs are 3500 psi service. Wow
I realize that my tanks are old but I thought mine are rated at 4500

CompuDude
11-19-2009, 17:28
The vast majority of yokes on any reg sold in the past 10 years are rated to 4500psi+.

Did you really mean to type 4500?

Absolutely, although it's possible I should have written 3500. Either way, it's not an issue.

It's only really old yoke regs that were marked for 3000 psi service... most are actually rated for 3500-4000-4500 or even 5000 psi service. The issue is the strength of the yoke itself, not the internal components. This is why you can convert yoke to DIN in many regs just by swapping the attachment. The reg itself is just fine with the extra pressure.

Unless your reg is really old, or clearly marked 3000 psi (200 bar) service, I wouldn't worry about it in the slightest.

CompuDude
11-19-2009, 17:33
Maybe that's the difference. My HPs are 3500 psi service. Wow
I realize that my tanks are old but I thought mine are rated at 4500

3500 psi service pressure HP tanks are "true" HP tanks. It's illegal to put an outlet on them that's not rated for 300 bar. So you only get them with 300 bar DIN valves. This is what Matt has, as well, it seems.

Most "HP" tanks sold today are rated a little below the 3500 psi limit to skirt that very rule. Manufacturers, simply by making that tiny change, can put a valve on the tank that lets them sell the same configuration to a much wider audience.

CompuDude
11-19-2009, 17:45
Found the quote I was looking for (one of them, anyway):


Over the years yokes have become stronger to deal with increasing service pressurse. For exampel the 50's era yokw was designed for 1800 and 2250 psi tanks with 10% over fills so the service rating was a max of about 2500 psi. Later when 3000 psi tanks became popular yokes were made stronger to prevent any stretching at the higher 3000-3300 psi service pressures, still later, they got really robust with the current 7/16" yoke screw being more or less standard surrounded by a very heavy yoke, with about twice the metal as the early 3000 psi yokes and many of those are stamped with 3500-4000 psi markings.

A well designed modern yoke is not going to be any where near failure at 3500 psi.

Chilkie
11-20-2009, 10:30
Found the quote I was looking for (one of them, anyway):


Over the years yokes have become stronger to deal with increasing service pressurse. For exampel the 50's era yokw was designed for 1800 and 2250 psi tanks with 10% over fills so the service rating was a max of about 2500 psi. Later when 3000 psi tanks became popular yokes were made stronger to prevent any stretching at the higher 3000-3300 psi service pressures, still later, they got really robust with the current 7/16" yoke screw being more or less standard surrounded by a very heavy yoke, with about twice the metal as the early 3000 psi yokes and many of those are stamped with 3500-4000 psi markings.

A well designed modern yoke is not going to be any where near failure at 3500 psi.


Great info compudude. Thanks!

MSilvia
11-20-2009, 11:48
Come on, you know better than that, Matt.
As it happens, I did not know better. Thanks for the info!

Since every HP tank I've ever owned was 3500 service pressure, and since I haven't purchased a yoke reg in... well, a long time, this is all news to me. Generally speaking, the only stuff I've read on SB lately is in the New England forum, or something that catches my eye on the first page of "new posts". There's way too much nonsense over there for me to wade through otherwise, which is no doubt how I missed the discussions about this.

CompuDude
11-20-2009, 12:58
Come on, you know better than that, Matt.
As it happens, I did not know better. Thanks for the info!

Since every HP tank I've ever owned was 3500 service pressure, and since I haven't purchased a yoke reg in... well, a long time, this is all news to me. Generally speaking, the only stuff I've read on SB lately is in the New England forum, or something that catches my eye on the first page of "new posts". There's way too much nonsense over there for me to wade through otherwise, which is no doubt how I missed the discussions about this.

My bad, and I can see how you may have missed that, with long upgrade cycles. Or I just over-estimated your knowledge. LOL :smiley31:

(I haven't read SB with any regularity in a year or more now, either, for similar reasons, but those discussion have popped up regularly on SB for several years.)

MSilvia
11-20-2009, 14:49
...Or I just over-estimated your knowledge.
No worries... I've been known to do that myself on occasion. :D

WD8CDH
11-20-2009, 16:37
Actually, it's not "illegal" to put a valve not rated for 300 bar on a 3500 psi tank. There isn't even a requirement for 3500psi tanks to have a neck thread different from the standard 3/4" NPS SCUBA thread. It was strictly marketing decision that made the first supplier of 3500 psi SCUBA tanks go with 7/8-14 UNF threads. The valve only has to be rated for the same or higher service pressure of the tanks they are used with. For many years prior to the 3500psi HP tank's introduction, Sherwood was selling yoke valves rated for 4000psi and even 5000psi. Even the OMS and many other "200bar" DIN valves are rated for 4500psi. In the case of most valves made today, the service pressure marked on the valve is the service pressure of the burst disk, not the valve itself.

The only reason that you might be forced to put a "300 bar" DIN valve on a 3500psi HP tank is none of the valve manufacturers ever made any SCUBA valves in anything but "300 bar" DIN with a 7/8"-14 UNF tank thread.

The common misconception that Yoke is limited to 3000psi comes mostly from the old CGA 850 standard from the '60s. There are more modern yoke standards that allow for far greater than 3000 psi. I personally own several yoke regulators with 4000psi forged into the yoke and one with 4500psi forged in the yoke. I also have one regulator with the "200bar" DIN connection rated for 4500psi that won't even fit a "300 bar" DIN valve.

Some pretty wimpy looking yokes (by today's standards) were regularly used by the Navy at 3000psi in the 60's and Cousteau was using double hose regulators at 5000psi on yoke valves in the early 70s.

Just make sure your o-ring is in good shape at higher pressures and keep spares, especially with rental tanks.

RogerAg
11-21-2009, 16:27
Actually, it's not "illegal" to put a valve not rated for 300 bar on a 3500 psi tank. There isn't even a requirement for 3500psi tanks to have a neck thread different from the standard 3/4" NPS SCUBA thread. It was strictly marketing decision that made the first supplier of 3500 psi SCUBA tanks go with 7/8-14 UNF threads. The valve only has to be rated for the same or higher service pressure of the tanks they are used with. For many years prior to the 3500psi HP tank's introduction, Sherwood was selling yoke valves rated for 4000psi and even 5000psi. Even the OMS and many other "200bar" DIN valves are rated for 4500psi. In the case of most valves made today, the service pressure marked on the valve is the service pressure of the burst disk, not the valve itself.

The only reason that you might be forced to put a "300 bar" DIN valve on a 3500psi HP tank is none of the valve manufacturers ever made any SCUBA valves in anything but "300 bar" DIN with a 7/8"-14 UNF tank thread.

The common misconception that Yoke is limited to 3000psi comes mostly from the old CGA 850 standard from the '60s. There are more modern yoke standards that allow for far greater than 3000 psi. I personally own several yoke regulators with 4000psi forged into the yoke and one with 4500psi forged in the yoke. I also have one regulator with the "200bar" DIN connection rated for 4500psi that won't even fit a "300 bar" DIN valve.

Some pretty wimpy looking yokes (by today's standards) were regularly used by the Navy at 3000psi in the 60's and Cousteau was using double hose regulators at 5000psi on yoke valves in the early 70s.

Just make sure your o-ring is in good shape at higher pressures and keep spares, especially with rental tanks.



I never checked my regs. before until now while reading your posts. The regs. I have are Mares Titanium that I got back in 1997
The Yoke states: MAX 232 BAR I did a little converting and came up with 3,364.88 psi. That certainly would not handle my 4,500 psi HP tanks .
For me it's not a problem because I simply take the yoke off and screw on a din.
But then I decided to check the din and it states: Bar 300 and I again did a little converting and came up with 4,351.13 psi.
I'm learning a lot by just going through these message boards thanks for the info.:communityhelper:

WD8CDH
11-23-2009, 13:46
Hi Roger,

The temperature that the SCUBA industry uses for pressure rating in bar is different than what is used for psi, but the common conversion in the SCUBA industry is 232bar = 3442psi.

I was beginning to think I was the only one on the board with 4,500 psi (310 bar) tanks. What kind do you have?

RogerAg
11-24-2009, 13:37
Hi Roger,

The temperature that the SCUBA industry uses for pressure rating in bar is different than what is used for psi, but the common conversion in the SCUBA industry is 232bar = 3442psi.

I was beginning to think I was the only one on the board with 4,500 psi (310 bar) tanks. What kind do you have?

Hello Ron
Now why does the (SCUBA Industry) say Bar is about 10.65psi? One Bar is air pressure at sea level? And that is just over 14.50 psi. However I do understand that one Industry uses one set of guidelines and another Industry uses another. But it is confusing. Anyone that buys a 10 Cup coffee maker will find that it does not hold 10 real cups. In the Coffee Industry a cup of coffee is just 5 ounces. The confusion comes in, with the difference between Coffee and water. 10 Cups of water is 80 ounces, What happens to the extra 30 ounces of water after the Coffee maker makes the water into Coffee.
ITS USED TO MOP THE FLOOR!!!!! :smiley35: