How to figure out the best tank to buy?

[TechBlack]

i hear the boys and girls in cave country have them pumped up to 4000psi. riding the rocket...

I'm a long way from cave country, but'iv;e seen it on a regular basis... I don't wanna be arond when one decides to let go!!!!

 

[francousteau]

that's the beauty of it!!! problem is most shops never check for the plus, and you end up getting overfilled anyways.... you have to watch out sometimes with lp's. I've had shops assume mine were hp, just because they were galvanized, and luckily enough saw the error before they were filled to high

Is this some kind of DOT issue then? Some kind of DOT regs during the mfg. of the cylinder? My shop routinely overfills mine (sshhh) to 3k and better, so the + rating isn't an issue for me, but this whole cylinder rating is confusing. I'm wondering why this isn't an issue with HP tanks??

 

[francousteau]

i hear the boys and girls in cave country have them pumped up to 4000psi. riding the rocket...

An interesting thread from TDS on the subject:
http://thedecostop.com/forums/showthread.php?t=16088

 

[spectrum]

Really, you take 10% off the cubic footage of the tank at the 2400psi rating? This pretty much sucks then and I'm left wondering why not just rate the tanks at 2640psi if they're going to call the tank a 85cf'r? After all, if the tank doesn't come back from hydro with the + rating, you're left with something other than the 85cf tank that you thought you were buying.

Look at it thiis way... You have 5 years to improove your air consumption by 10%, then you come out even or better.

Pete

 

[spectrum]

I'm assuming I want steel, so I can get more air for the same weight--is that the way to go?

It certainly is a nice way to dive. Have you seen this post?
http://www.scubaboard.com/showpost.php?p=1191538&postcount=16
Use the link in this link to get specs to run the numbers with the cylinders you are considering to see how they compare with your AL80.

I am normally a big HP advocate. My diving is almost exlusively cold water shore diving. The weight of my rig (cylinder and ballast) is important to me and my wife.

You sound like you are mainly a boat diver and as such tank weight is not such a big deal. That being the case a LP steel cylinder may be an attractive option with a lower cost and no fussy filling.

Pete

 

[sprange]

Actually I used to think this too, but when having the tanks hydroed, some shops were not getting the "+" renewed and this was causing under fill problems with the lp tanks. The advertised volume is at the give pressure of 2400+ which is 2640. My double 104's yeild close to 240 cu at 3000, my double lp80's give me 182 cu at 3000, not that I recommend that sort of thing!!!

Are you sure the "+" stamp isn't just a DOT (US) issue that has managed to confuse Canadian dive shops? Every low pressure tank that I've seen has "184" in the TC section indicating that it can be filled to 184 bar (~2640 psi). In the DOT section you'll notice "2400", and this is where the "+" comes into play--allowing the 'overfill' to 2640.

Sean

 

[aaarnt57]

Faber LP 108,s 5000 psi BD,s at 3500 psi and not a lb less.

 

[TechBlack]

Are you sure the "+" stamp isn't just a DOT (US) issue that has managed to confuse Canadian dive shops? Every low pressure tank that I've seen has "184" in the TC section indicating that it can be filled to 184 bar (~2640 psi). In the DOT section you'll notice "2400", and this is where the "+" comes into play--allowing the 'overfill' to 2640.

Sean

I'm not 100% sure on the regs, but from my understanding, lp's are rated to 2400 psi service pressure, and then a second test is performed at the time of hydro (the inital one, and one every 5 years thereafter) and if the tank passes the second test, the "+" is stamped next to the hydro date, indicating that it can be overfilled 10% or to 2640 psi. But you raise an interesting point,maybe there's a guru out there who knows this for sure. But from what I can tell here (quebec/ontario), every tank that has had it's second hydro done gets the stamp also, so maybe the "+" is redundant?

 

[Abyssdiver]

Sorry guys... I was the operations manager for OMS and the 10% overfill to 2640 is 85cu feet of air in a 85 cu foot cylinder... If you fill only to 2400 it will not be 85cu feet of air!!! When planning your dives make sure you figure that into your numbers.. You will run short on gas..

You can contact the folks at Tech Diving Unlimited and speak with Joel or Scotty if you don't choose to believe me. But that's the truth.. They will also be able to choose the correct cylinder for the application you are using the cylinder too..

Randy

 

[JimC]

Are you sure the "+" stamp isn't just a DOT (US) issue that has managed to confuse Canadian dive shops? Every low pressure tank that I've seen has "184" in the TC section indicating that it can be filled to 184 bar (~2640 psi). In the DOT section you'll notice "2400", and this is where the "+" comes into play--allowing the 'overfill' to 2640.

Sean

You are correct. The + rateing is a DOT only thing. TC does not have a + rateing.

In canada you should fill to the TC stamp specifications. Ei: 184 bar. Most dive shops just don't know what they are doing. Most don't even have bar on their gauges.

The only pickle you end up in is with grandfathered DOT tanks from before there was a TC. They follow DOT rules.