over fill a low pressure steel tank?

[Rhone Man]

First of all, the hydro for an LP120 is 4000psi, not 4400. 2400 x 5 / 3.
Secondly, a 120 at 3000 is not 170cu' it's 136cu'
Thirdly, i'd put 4k in that tank without blinking an eye, too...

I say. 136.36 or so.

Not sure how he got to 170. That tank is 22 psi/ft^3 so he was off by 740 psi. Would not think too much about 3740, but I think lp 120s are a bit big for me anyway.

You are both mistaken, surely? 120 cu ft is calculated on a working pressure of 2400 psi. If you fill to 3000 psi you get 120 x (3000 / 2400) = 150 cu ft. N'est pas?

Point being - that's a lot of gas.

 

[guyharrisonphoto]

How does overfilling an LP tank compare to having an HP tank? An LP 95 is about the same size as an HP 130. Can the HP tank be "overfilled?" Will I get more capacity with the LP 95 filled to 3500 PSI than with the HP 130 filled to 3440?

Thanks,

Guy

 

[PfcAJ]

A lp95 is closer to a hp119, and the lp104 is close to a hp130.

Filling tanks past 3600 or so results in diminishing returns. Gases don't follow the ideal gas law at high pressures, so you end up getting less volume crammed in the tank relative to pressure.

 

[redacted]

You are both mistaken, surely? 120 cu ft is calculated on a working pressure of 2400 psi. If you fill to 3000 psi you get 120 x (3000 / 2400) = 150 cu ft. N'est pas?

Point being - that's a lot of gas.

I'm pretty sure the capacity ratings include the +10% when applicable: Scuba Cylinder Specifications from Tech Diving Limited - 928-855-9400

 

[300bar]

Guess all those euro valves with no burst disks are just accidents waiting to happen...

And yet we don't have any exploding tanks yet AFAIK

We had some idiots putting M25 valves into a 3/4gas tanks(gave a great BANG)


Burstdisks are useless (atleast on steel)

Tanks are filled during hydro 1.5 times the working pressure, and that is with a VERY safe margian.
They can easely withstand 4x that working pressure.

 

[manni-yunk]

Not really.

A "working pressure" for many steel LP tanks is calculated assuming the + stamp and 10% overfill. Example - an LP 95 is only 95 at 2640. At the NON PLUS stamped rated pressure of 2400 - its only an 88 cu ft. The Hydro test, however is 5/3 of the 2400....and not the 2640.

I dont own any LP 120s so I cant speak to ratings....but pressures and capacities can be very misleading.

 

[Jacob Plunkett]

my question is what is the burst disk psi when the tanks are bought new? new to the forum but not new to diving. first post here.
I am about to buy two LP95's and was curious if i intend to fill to 3500psi is the factory burst disk ok or do i need to replace it, and if so where can i get a higher rated burst disk and whats the torque spec on the cap?

 

[g1138]

my question is what is the burst disk psi when the tanks are bought new? new to the forum but not new to diving. first post here.
I am about to buy two LP95's and was curious if i intend to fill to 3500psi is the factory burst disk ok or do i need to replace it, and if so where can i get a higher rated burst disk and whats the torque spec on the cap?

Roughly and usually 5/3's working pressure, or Hydro Test pressure.
Some MFG's will go slightly less.
You will find the Burst Disk rating stamped into the burst disk usually along it's edge.

2400psi working has a 4000psi burst disk
3000psi working pressure has 5000psi burst disk
3442psi working pressure has 5250 burst disk

Fun Fact:
You will see some valves have a "PSI Service Pressure" label on them.
A 3000psi Service Pressure Label means it's for a 3000psi working pressure tank (ie. Al 80)
Ergo the burst disk should be 5000psi. The pressure label on the valve doesn't signify when the burst disk goes.

And some dumb dumbs can swap in the wrong burst disk or wrong "valve" with incorrect burst disk for the tank's working pressure. Something to look for when shopping used tanks.

 

[NAM001]

I'm pretty sure the capacity ratings include the +10% when applicable: Scuba Cylinder Specifications from Tech Diving Limited - 928-855-9400

The capacity is rated at the 10% over fill psi.

 

[NAM001]

You are both mistaken, surely? 120 cu ft is calculated on a working pressure of 2400 psi. If you fill to 3000 psi you get 120 x (3000 / 2400) = 150 cu ft. N'est pas?

Point being - that's a lot of gas.

the capacity is with the + 10% overfill to 2640. the lp95 at 3000 psi is 108 cuft. the lp120 is about 135 @ 3ooo psi.

I look at my lp120 at 3200 as 2 al 80's since an al80 is 77 and you only need the reserve 500 from one of those tanks . ADN THE OMS TANK IS 125 BUT CALLED A 120. I dive all day with one. Yes it is a lot of gas. Not only a lot of gas its a lot of weight on land. 60+ # FILLED