How long should it take a liveaboard to fix their Nitrox?? (Dancer fleet)

[mathauck0814]

OR ... just dive air and decompress as necessary.

 

[cephalopod2]

Can someone do the math of how many EAN40 tanks would be required to provide AL80 (77cu ft) EAN32 for let's say 'just' 12 divers over the course of 5+ days of 4 dive per day diving? Seems like a lot....

If they like the idea I would actually propose a higher mix - basically as high as a Bali op would mix for them as long as it's not pure O2 (if they agree to pure O2 even better although I think they will not). I guess I should put a gas blending cert on my to do list for the future - could come in handy. Are there limits to how high a % one could mix?

There are many ways this could unfold. My goal is to get them to take a first step to a solution and then work from there. Hopefully not all onboard would want Nitrox, and even if they do, there are ways to ration or prioritize by diver or by dive. Nitrox is not that important to everyone.

 

[nimoh]

Can someone do the math of how many EAN40 tanks would be required to provide AL80 (77cu ft) EAN32 for let's say 'just' 12 divers over the course of 5+ days of 4 dive per day diving? Seems like a lot....

rough calculation off the top of my head

5 days, 12 divers 4 dives per day is 240 tank fills, less say 20 tanks that you would leave port with full of EAN32 is 220 tank fills

roughly have to mix EAN40 with air half and half to get EAN32, figure each tank has about 500psi in it, so 60ft3 fill, 30ft3 of which is EAN40.

so, 1 300ft3 supply tank is good for 10 fills, and 22 would be needed (along with a booster), after that everyone is diving air.

so yes, its a lot, unless refilling the supply tanks over the course of the trip is possible.

 

[boulderjohn]

If they like the idea I would actually propose a higher mix - basically as high as a Bali op would mix for them as long as it's not pure O2 (if they agree to pure O2 even better although I think they will not). I guess I should put a gas blending cert on my to do list for the future - could come in handy. Are there limits to how high a % one could mix?

Anything over 40% will have the same rules as O2, and for a good reason. As I understand it, NASAs research after the disastrous fire that killed three astronauts indicated that the dangers of handling O2 were pretty much the same from 50%-100%.

I have only been on 4 liveaboards, but as I think back on them, I can't think of any that would have room for a bunch of 300 cubic foot tanks of EANx 40. It is also a surprisingly expensive solution, believe me. It would be a lot cheaper for the company to do what it takes to fix the present system, and they apparently don't want to spend that kind of money.

 

[nimoh]

Anything over 40% will have the same rules as O2, and for a good reason. As I understand it, NASAs research after the disastrous fire that killed three astronauts indicated that the dangers of handling O2 were pretty much the same from 50%-100%.

I have only been on 4 liveaboards, but as I think back on them, I can't think of any that would have room for a bunch of 300 cubic foot tanks of EANx 40. It is also a surprisingly expensive solution, believe me. It would be a lot cheaper for the company to do what it takes to fix the present system, and they apparently don't want to spend that kind of money.

I agree, it was only an idea

 

[cephalopod2]

Anything over 40% will have the same rules as O2, and for a good reason.

Unfortunate but good to know - thanks.

I have only been on 4 liveaboards, but as I think back on them, I can't think of any that would have room for a bunch of 300 cubic foot tanks of EANx 40. It is also a surprisingly expensive solution, believe me. It would be a lot cheaper for the company to do what it takes to fix the present system, and they apparently don't want to spend that kind of money.

On the issue of cost, they could pass along some of the costs to the divers and presumably absorb some - I have no idea the scale here. Cheapness could be well be the reason behind the 4 week delay but it could it also conceivably be the travel schedule of the manufacturer's mechanic, back order of a specific part, or am I being naive?

IMO this is a customer service issue. Let's say even with max effort (if that were present), the system couldn't be fixed in time. An out of the box solution is what I would expect from a quality boat with a reputation for service on the line. The US office might not set the bar this high, but the local owners might (being optimistic, I accept).

 

[mathauck0814]

rough calculation off the top of my head

5 days, 12 divers 4 dives per day is 240 tank fills, less say 20 tanks that you would leave port with full of EAN32 is 220 tank fills

roughly have to mix EAN40 with air half and half to get EAN32, figure each tank has about 500psi in it, so 60ft3 fill, 30ft3 of which is EAN40.

so, 1 300ft3 supply tank is good for 10 fills, and 22 would be needed (along with a booster), after that everyone is diving air.

so yes, its a lot, unless refilling the supply tanks over the course of the trip is possible.

You're assuming that the booster can suck the supply bottle dry and that the boat's compressor has the capacity to both boost gas AND perform top ups in the short surface interval period for n divers. Depending on the size of the compressor you may put stress on the system, empty the banks or both.

If it were my boat, I'd apologize for the inconvenience, make a good faith attempt to get the system fixed and failing that, tell you to just dive air. Having a crew busy themselves with bandaid nitrox solutions, inefficient blending strategies, etc. distracts from their already busy day and deviates from the routine of the boat.

 

[nimoh]

You're assuming that the booster can suck the supply bottle dry and that the boat's compressor has the capacity to both boost gas AND perform top ups in the short surface interval period for n divers. Depending on the size of the compressor you may put stress on the system, empty the banks or both.

If it were my boat, I'd apologize for the inconvenience, make a good faith attempt to get the system fixed and failing that, tell you to just dive air. Having a crew busy themselves with bandaid nitrox solutions, inefficient blending strategies, etc. distracts from their already busy day and deviates from the routine of the boat.

Like I said, rough calculation, but agree with what you said.

Really not feasible without using a smaller bank and stopping along the way somewhere to have the bank refilled, and if that is the case, may as well just put EAN32 in the bank.

 

[Shasta_man]

Sorry, but I would prepare to dive on air. If you were telling me they do all of their nitrox that way, Indonesia style, I'd believe you, but trying to hack this together seems pretty unlikely.

Shame to hear the Komodo Dancer is having this trouble. We had a great trip in 2009.

One question, cephalopd2: Are you saying you were on both the initial ill fated Carib Dancer trip and the Aggressor I ran aground trip?

 

[cephalopod2]

Really not feasible without using a smaller bank and stopping along the way somewhere to have the bank refilled, and if that is the case, may as well just put EAN32 in the bank.

Refills not impossible - looks like there is now a tec op based in Labuan Bajo, from this I would bet there are a couple rec ops with EAN 32 as well.

As mathauck0814 points out there is still the crew time (and cost), but there tends to be lots of crew (relative to LOBs in South America, Caribbean, Red Sea etc) on Indo LOBs. One may be 100% devoted to tank filling.

Thank you very much nimoh, boulderjohn, mathauck0814 for taking the time to think through the technical issues I don't know enough about.