Dive knife, Sea Snips, or both?

[Skulmoski]

I carry titanium snips (right side BP/W belt), Spyderco Enuff Sheepfoot in H-1 steel (left side BP/W belt), and Hollis titanium line cutter on left BP/W shoulder strap). Different cutters for different jobs. And redundancy if i loose a tool or get tangled and cannot reach a primary tool.

GJS

 

[Trace Wilson]

It's not a show off. It's a necessary for my peace of mind and to insure that I have backup dive computer to continue the dive, when the primary one fails during the dive / dive trip. After some dive computer failures (ran out of battery & set to free diving mode by accident during a dive) that grounded me for a day / two during a week-long liveaboard trip, I decided to have a backup dive computer.

After seeing my dive buddy high-pressure hose failure (the hose was actually blew up with a bang, luckily it happened before he jumped into the water), I decided to have a back up tank press reading too. Now I have 2 ways to read the tank pressure, one with SPG, the other one via one of the dive computer. If one of the 2 high pressure hoses fails, I'd just thumb that dive, remove the broken hose and plug the port in the 1st stage. Then continue the rest of the dive trip with the backup pressure gauge.

There are quite a few divers here in Scubaboard diving with 2 dive computers and a backup SPG for similar reason I have experienced.

Curious, any idea how fast do you lose air from a tank if the high pressure hose goes, i.e. PSI/min? Just wondering how long I'd have to get topside if I lost one.

 

[Dan]

Curious, any idea how fast do you lose air from a tank if the high pressure hose goes, i.e. PSI/min? Just wondering how long I'd have to get topside if I lost one.

No clue. Sorry. That's why we have buddy system in addition to the gear redundancy to make sure we cover screw up resolutions as much as possible.

 

[Lorenzoid]

I love this video, comparing how long it takes to drain a tank if a diver's HP hose is cut with how long it takes to drain a tank if the diver's LP hose is cut:

 

[Dan]

Curious, any idea how fast do you lose air from a tank if the high pressure hose goes, i.e. PSI/min? Just wondering how long I'd have to get topside if I lost one.

You got me curious about doing the math now

It'll be about 7.5 minutes according to the following input data, calculations & assumptions:
Tank size: AL80 or 80 CF
Initial pressure = 3185 psig (max input for the Engineering Calculator allowed for calculating an air flow through orifice (I assume it reaches the sonic velocity): Calculator: Air Flow Rate through an Orifice | TLV - A Steam Specialist Company (International)
Air temperature = warm water temp of 82F
Hose inside diameter = 1/4"

The gas rate is estimated to be 2301 SCFM. The AL80 at 3185 psig will have 17333 SCF (3185 x 80 / 14.7). Leak time = 17333 / 2301 = 7.5 min.

 

[Charles2]

You got me curious about doing the math now

It'll be about 7.5 minutes according to the following input data, calculations & assumptions:
Tank size: AL80 or 80 CF
Initial pressure = 3185 psig (max input for the Engineering Calculator allowed for calculating an air flow through orifice (I assume it reaches the sonic velocity): Calculator: Air Flow Rate through an Orifice | TLV - A Steam Specialist Company (International)
Air temperature = warm water temp of 82F
Hose inside diameter = 1/4"

View attachment 427435

The gas rate is estimated to be 2301 SCFM. The AL80 at 3185 psig will have 17333 SCF (3185 x 80 / 14.7). Leak time = 17333 / 2301 = 7.5 min.

I think you are waaaay off on this one. Hose may be 1/4" ID but orifice is much, much smaller. An AL80 at 3185 psi will have about 82 SCF. Also, the tank pressure will not be constant but decreasing as the air bleeds out.

 

[briannapstevens]

It's not a show off. It's a necessary for my peace of mind and to insure that I have backup dive computer to continue the dive, when the primary one fails during the dive / dive trip. After some dive computer failures (ran out of battery & set to free diving mode by accident during a dive) that grounded me for a day / two during a week-long liveaboard trip, I decided to have a backup dive computer.

After seeing my dive buddy high-pressure hose failure (the hose was actually blew up with a bang, luckily it happened before he jumped into the water), I decided to have a back up tank press reading too. Now I have 2 ways to read the tank pressure, one with SPG, the other one via one of the dive computer. If one of the 2 high pressure hoses fails, I'd just thumb that dive, remove the broken hose and plug the port in the 1st stage. Then continue the rest of the dive trip with the backup pressure gauge.

There are quite a few divers here in Scubaboard diving with 2 dive computers and a backup SPG for similar reason I have experienced.

Don't take it personally! I'm just jealous! I keep fantasizing about the Suuntos. But cannot afford one! I have two computers, too. Crappy old Oceanic ones, although I still love my Veo. I really want an air integrated computer w/digital compass!

 

[Dan]

I think you are waaaay off on this one. Hose may be 1/4" ID but orifice is much, much smaller. An AL80 at 3185 psi will have about 82 SCF. Also, the tank pressure will not be constant but decreasing as the air bleeds out.

You are right! I forgot about the tiny orifice at the fitting to the 1st stage & the tank losing pressure. The low pressure hose will actually lose air faster due to the larger orifice. Live & learn. Thanks for the tips

 

[Dan]

I love this video, comparing how long it takes to drain a tank if a diver's HP hose is cut with how long it takes to drain a tank if the diver's LP hose is cut:

That's a very educational video! Thanks for posting

 

[Dan]

Don't take it personally! I'm just jealous! I keep fantasizing about the Suuntos. But cannot afford one! I have two computers, too. Crappy old Oceanic ones, although I still love my Veo. I really want an air integrated computer w/digital compass!

None taken

Just wanted to share my past experience on the importance of having redundancy.