Safety Questions

[cgm73]

Good evening. Got a few safety questions.

I am a complete newbie so any questions that have already been answered please excuse. I researched what I can but can only find general answers and not specifics. I need proffesional advise. I am going to be diving in 60-120ft of water on eastern SC coast spear fishing. Using steel 120 low pressure nitrox tanks. When spear fishing often the buddy system is not often helpful if your buddy is to far away are poor visibility if a problem arise. First question.

1). At 110ft with a safety stop required what would be an adequate extra air supply to include a safety stop to get me to the surface. From what I've read spare air 3.0 would be worthless at that depth.

2) if an oring on the first stage blewout at that depth what would be an estimate on how fast my air would deplete. Also if it was an oring from regulator line are regulator started free flowing? With proper maintenance what would be the likelihood of any of these occurring?
Seems like these are the only way of loosing air extremely quick other than a cut hose.
If this happened would it be better to try to find buddy are just make an emergency ascent and miss safety stop and take chance.

Trying to have a backup plan if something went wrong. I'm 6.1ft 190lbs in decent shape.
The fellows I will be diving with are experienced divers and they only carry one tank. Thanks for the help. Any other safety advise would be welcome. Thanks for the help.

 

[Dr. Lecter]

I need proffesional advise.

Then you're in the wrong place. Internet advice is worth exactly what you pay for it.

I am going to be diving in 60-120ft of water on eastern SC coast spear fishing. Using steel 120 low pressure nitrox tanks. When spear fishing often the buddy system is not often helpful if your buddy is to far away are poor visibility if a problem arise.

<checks dive count> This can only end well.

At 110ft with a safety stop required what would be an adequate extra air supply to include a safety stop to get me to the surface.

First things first: safety stops are, by definition, never required. If you have a required stop, you're in deco.

That said, the answer to your question depends on knowing your gas consumption rate under the conditions you'll be diving and then adding a realistic fudge factor to accommodate the fact that when things go wrong your breathing rate goes up. We don't know that information and it's blindingly clear you don't either. So, I'd guess on the 'never have too much gas' side of things and take an AL30 or 40 as a pony. An AL19 would probably work, but it also might not.

if an oring on the first stage blewout at that depth what would be an estimate on how fast my air would deplete. Also if it was an oring from regulator line are regulator started free flowing? With proper maintenance what would be the likelihood of any of these occurring?

Try consulting with Las Vegas, I hear they'll give odds on almost anything.

Seems like these are the only way of loosing air extremely quick other than a cut hose.

And yet they're not.

If this happened would it be better to try to find buddy are just make an emergency ascent and miss safety stop and take chance.

Bent beats dead every day of the week and twice on Sundays, but remember that bent can mean permanent neurological damage and paralysis. You loads your tissues and you takes your chances.

 

[dumpsterDiver]

If you have less than 24 dives and are a total newbie... you do not belong spearfishing in 120 feet of water. No way that is safe.

I have been spearing hundreds of times in those depths alone and you just have no business engaging in that activity. Before you dive solo spearing in 120 feet, you need to be completely comfortable diving solo. Diving solo in 120 feet is not that big of a deal for most peoples .. . but add in spearfishing and big fish, and tangled lines and aggressive sharks and exertion from chasing and grabbing fish and everything changes.

If these guys are willing to take you out there and have you spearfish, then you need to find new buddies, because they are not looking out for you. At best, get a 13 or 19 cu-ft pony bottle, figure how to rig it and then beg them to allow you to WATCH spearfishing for several trips..

 

[TSandM]

At 110, using a 60 fpm ascent rate, you are roughly 2 minutes from a safety stop, with an average depth of 3 ATA during your ascent. 2 minutes, at a stressed SAC rate of 1.0 cfm, and an average of 3 ATA, is 6 cubic feet of gas for ascent. We usually allow a minute at depth to sort out the issue, which would be about 4.5 cf. 3 minutes at 15 feet with a SAC of 1.0 is another 4.5 cf, so you are looking at about 15 cubic feet of gas to do a maximal rate ascent with safety stop. Obviously, a 3 cubic foot reserve is going to be pretty worthless, and most computers want a 30 fpm ascent, so these numbers are really last-ditch get out of Dodge values.

It is definitely unusual to have a sudden malfunction that shuts off your gas supply, but it can happen. Especially with spearfishing, where you assume unusual attitudes, a clogged dip tube is a possibility. Free-flows happen, and empty an Al80 in about 90 seconds (from full, which your tank may not be when the free-flow occurs). Any major leak on the LP side (or tank o-ring, or burst disc) will empty things that fast.

It is ALWAYS better to have a gas supply, than not to have one. If you have a buddy with whom you can share, AND that buddy has maintained reserves for 2, AND that buddy and you are competent at doing an ascent while sharing gas, you are in a much better situation if you are breathing, than if you are not. If your buddy hasn't maintained reserves, or neither of you has practiced an air-share since open water class, then you might be better off heading for the surface with the gas you have left.

 

[marinuse]

Can't help but agreeing with dumpsterDiver.
Unless you're a natural (which from the questions you ask I would conclude you are not, no offense), you need at least 50 dives to learn how to dive.
Diving is like driving a car. You learn it only after you got your license. And driving you don't learn with twice a week to the grocery store 1km down the road.

At this point we shouldn't even be answering the questions your asking.
Get a bit more experience first with *just* scuba diving. When you're completely comfortable with *just* diving, THEN move on to "bigger" things.

By the way... The questions you ask in your original post you should all be able to answer with the knowledge you were given in the Open Water Course.
Question 1) (e-)RDPML.
Qeustion 2) remember the free flowing regulator exercise? That should give you somewhat of an indication of how quickly your tank empties when anything under hi-pressure blows. Breathing 30 seconds from a free flowing regulator will cost you approximately 15-30 bars of air (somewhat depending on the gear you're using).

 

[cgm73]

TsandM,
Very logical and thought out answer. This is what i was looking for. thanks for your help.

---------- Post added July 1st, 2015 at 08:36 AM ----------

Dr Lector,
Why waste your time and mine with worthless answers that just give you a feeling of superiority for having experience i do not have. Why not just think it in your head and that be the end of it. Instead you took your time to answer nothing, and wasted my time reading your nothing. thanks

 

[Dhboner]

Dr. Lector did not waste your time...he was trying to illustrate that the questions you ask betray the fact that you should not consider the dive without further training and experience. You can't ask a question without being open to honest answers.

 

[diver 85]

Man OP---you've got problems------that a few 'extra' diveS might solve........I'd forget your game plan (you've described) & op' out for more 'fun' dives---IF--you're that concerned about your diving abilities.........good luck, hope they have to throw the fish you spear----& you---in the 'cooler' on the way back to the dock........

 

[cgm73]

diver 85 Im not concerned about my diving ability, I am concerned with reliability of equipment. I dont have a problem doing my part, Im worried about unforeseen equipment problems that my inexperience might not be able to overcome. I dont plan on ending up in the fish cooler.

bcd Ranger Zeagle
first state Scubapro MK25
regulator Scubapro A700

 

[orion612004]

As a Diving Safety Officer, Instructor and Dive Medic I have to agree with the previous posters. The questions you ask should have been answered in your open water class and the nature of your questions shows your inexperience. You want professional advice, go back to the dive shop where you got certified and talk to them. It appears they missed a lecture or two during your open water class. 60-120 ft is considered deep and the the skills for that depth range comes with taking an AOW class and time. Have you ever dove that deep before? Off a boat? been spearfishing? used this gear before? gone bluewater diving? solo diving? used a pony body? done a safety stop? understand decompression stops just in chance? Do you have a dive computer? If so, Do you know how to use it?

I am just curious because that is a alot of new things and multitasking can stress even a more experienced diver. Do your dive buddies know to diving capabilities? Have you dove with them before? Are there any safety measures in place? Is you DAN Insurance current? If not, you may want to get the Guardian Plan.

I would recommend scrapping the dive until you have the knowledge and experience to answer the questions you asked. If not best of luck, and assuming your gear is properly maintained and serviced (read the manual for instructions) I would not stress too much about o rings popping out at depth or your hose being cut (unless you are also filming the new James Bond movie) but more on your dive and air consumption. Fatalities caused by dive gear is around 1%, most of the time it is user error (DAN Fatality Report) and Open water students diving beyond their means.

Cheers

Orion

---------- Post added July 1st, 2015 at 09:27 AM ----------

I dont plan on ending up in the fish cooler.

Does anyone?