Gas Usage Planning for Expeditions

GLOC · January 15th, 2007, 02:06 PM

I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco.

1. Pay for He on the boat at 3p per litre (O2 is 1p per litre)
2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!)
3. Take J's/get J's delivered and cascade
4. Take J's/get J's delivered and boost

If we fill our own tins with He, the skipper doesn't want it done on the boat but the quayside, O2/air tops will be carried out by him.

So, here comes the difficult questions. Once I have worked out the litreage (sp?) of gas required, how do I work out how many J's I need to order if we are going to cascade?

There is already one blender on the team but by the time we get there, there should be 3 of us.

Finally, how much difference does it make if you use a booster (Haskell?) and does anyone know where we can hire one?

Regards

nic_the_greek · January 15th, 2007, 02:42 PM

Quote: (Originally Posted by GLOC)

I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco.

1. Pay for He on the boat at 3p per litre (O2 is 1p per litre)
2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!)
3. Take J's/get J's delivered and cascade
4. Take J's/get J's delivered and boost

If we fill our own tins with He, the skipper doesn't want it done on the boat but the quayside, O2/air tops will be carried out by him.

So, here comes the difficult questions. Once I have worked out the litreage (sp?) of gas required, how do I work out how many J's I need to order if we are going to cascade?

There is already one blender on the team but by the time we get there, there should be 3 of us.

Finally, how much difference does it make if you use a booster (Haskell?) and does anyone know where we can hire one?

Regards

Firstly, this sort of calculation should be covered in your Blender training - both the TDI and PSAI exams had questions regarding gas planning for expeditions. Speak to your instructor, I'm sure they will help you go through it.

Secondly, last year we took a twinset of 30/70. By decanting 75bar in to an e,pty twinset and topping with air to 210bar you'd get a 24/25 mix. Not exactly what you're after but it was good for us and is divable to 45m.

Cheers/Nic

PBrown · January 15th, 2007, 02:51 PM

Quote: (Originally Posted by GLOC)

I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco.

1. Pay for He on the boat at 3p per litre (O2 is 1p per litre)
2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!)
3. Take J's/get J's delivered and cascade
4. Take J's/get J's delivered and boost

We used Air products a couple of years ago & picked them up on the island, it woked well for us, although it did involve a trip to Kirkwell to pick the J's up and then another to drop them off at the end (they might deliver to the quayside now). We already have an account so the price was the same as we pay at home.

Quote:

If we fill our own tins with He, the skipper doesn't want it done on the boat but the quayside, O2/air tops will be carried out by him.

don't forget to factor time into your plans, you will (presumably) need to haul your twins off & back on again (easier at high tide than low tide!) as well as the time for the actual filling. It would be better if the skipper would allow the J's onboard, as you can use travelling time for filling (but I can understand his/her reluctance if you are removing a potential for profit from them).

Quote:

So, here comes the difficult questions. Once I have worked out the litreage (sp?) of gas required, how do I work out how many J's I need to order if we are going to cascade?

I cheat, I allow Simon to work it out for me!

Lawrence Orchard wrote a spreadsheet many years ago, which is still vaild, you can download a copy from here:
tools

Quote:

Finally, how much difference does it make if you use a booster (Haskell?) and does anyone know where we can hire one?

For one week it would probably be far more hassle than it's worth. I would be surprised if you saved enough to make it worth while. Don't forget you would also need a means of driving the thing.

cheers,
Paul

Gary K · January 15th, 2007, 03:04 PM

Quote: (Originally Posted by GLOC)

1. Pay for He on the boat at 3p per litre (O2 is 1p per litre)
2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!)
3. Take J's/get J's delivered and cascade
4. Take J's/get J's delivered and boost

1. its approx £80 a fill
2. you'd need 4 or 5 twinsets each
3/4. possible but I couldn't find a booster on hire

The easiest way for volume would be to take the van over (£100), then collect/get a few of J's delivered and cascade. You certainly wouldn't want to take them with you from down south, think of the vehicle fuel!

Working on the 45% He, even if you come back with a reasonable reserve, you'll need a J each

Using the booster would help because you can get more out of the J than just equalizing when the J is low but remember you'll also need a drive source. Unless you borrow one, I wouldn't worry about the booster.

I suspect a J will cost over £200 up there, so it'll still work out £60 a fill

If your going to need that much, I'd have a quiet word with Ian and see if he's willing to do a bulk deal on the He

PBrown · January 15th, 2007, 03:11 PM

Quote: (Originally Posted by nic_the_greek)

Secondly, last year we took a twinset of 30/70. By decanting 75bar in to an e,pty twinset and topping with air to 210bar you'd get a 24/25 mix. Not exactly what you're after but it was good for us and is divable to 45m.

This is also a good way of doing it, if you can get enough twinsets, or potentially use stages. We did this in France this year, do a dive with a very rich He mix, then simply air top it for the 2nd dive. The stages were great, breath one empty, equalise with a full one, air top both and you now have enough for two more dives.

Of course this means you may not be diving standard mixes.

cheers,
Paul

jamesd · January 15th, 2007, 03:29 PM

Could you not use stages? A twinset and an AL80 of bottom gas should last you 2 mix dives. You can get this filled from your favoured cheap supplier before you go. If you only plan another 2 mix dives you can just get the twinset and stage filled up by the skipper.
It may be more slightly more expensive but:
you won't have to move J's around, or hire them or phaff
you won't have to hire a bigger transit,
you won't fall out of favour with the skipper,
he will blend the gas for you giving you more holiday

I know tech 1 dives who use the twinset and stage and deco bottle approach for diving weekends, particularly when gas is going to be difficult to find.

jd

JS1scuba · January 15th, 2007, 04:45 PM

Quote: (Originally Posted by GLOC)

I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco.
Regards

We do this ALL the time. First you need to get out of the "perfect mix mode" and put on your "creative mixing in the field cap"

Take 2 twinsets. .... fill them with 14/60 trimix full then follow rule of thirds plus a little (always more is better) then top with air to approx 150 bar (do the math on your own) you will end up with about 18/35.

Another thing we do is to start one set at 18/45 and the other set is 10/90 we use the 10/90 set as a "sweetener" to set 1 after dive 1 and then top with air (if you have compressor on board) and keep doing this till you are done ---

On the deco gas bring deco bottles in 50% and 100% do high helium mix dives with Both deco gases, then top the 50% bottles till you end up with 36% EAN and the 100% bottles you can still use until you reach approx 100 bar then top those to make 50% -- critical to relable on the spot so the cylinders do NOT get confused.

As to the rest of your twinsets for nitrox two big bottles of oxygen will make many many twinsets of Nitrox 32%

I have traveled with boosters and compressors and all kinds of kit to make all this work and usually we have 10 divers most of which are so hellbent on having a perfect mix we have just made it so that if you want a perfect mix YOU bring all the sets of gas YOU want to have. Otherwise just learn to be a bit creative and a little accomodating and you can have a lot of fun and still do perfect dives. It sure makes it a better evening if you just have to top up some sets with air than to have to dick around (states term) for 5 hours filling and tweaking gas.

The key here is to work out your gas plan FIRST and let everyone know what that gas plan is. If they break the gas fill plan by breathing down too much or not starting out with the right start mix then they get stuck with what they get.

I had a few folks on a project this past year that broke the gas fill plan and it ended up costing them a bit for all the extra helium we had to use to get them topped.

Welcome to getting gas in the field!

Cheers

GLOC · January 15th, 2007, 04:58 PM

Thanks everyone for the thoughts. Hadn't really thought about the AL80/bottom stages but it does sound like it would make things logistically easier to use those. Haven't done the mixing course yet Tricky but will probably do it with Mark Powell when I contact him.

A revised plan then: 2 twinsets of 18.45 each with 4 AL80 with 18.45 should give 4 dives per person, 1 twinset of 32% and then 1 AL80 of 50% to start with. (Don't want to crash the van then with that amount of money onboard!)

The O2 tops/fills will be done by the skipper rather than piss him off.

Looks like 15 twinsets, 25 AL80s, at least 2 scooters, and all the rest of the gear: that should easily fit into the back of a transit

Is everyone busy in the first week in September or might you be able to lend some AL80s

**neilh** · January 15th, 2007, 05:30 PM

Quote: (Originally Posted by GLOC)

Is everyone busy in the first week in September or might you be able to lend some AL80s

Gimme a shout nearer the time, but you could probably borrow one from me as you pass through

...in fact you might also be able to borrow the faber 12's as well if that's any use...

jamesd · January 15th, 2007, 05:30 PM

Hi

I would reduce the number of twinsets unless you are determined not to buy any trimix from the boat. 1 twinset, 1 deco bottle and 1 stage should be enough per person. Keep filling the stage, either with trimix for the morning dives or 32% for the afternoon dives. From the plan you describe I would think you should only need 3 12L fills of Trimix onboard.

The transit van should take it all. The one I hired last year had only 8 twinsets and 12 deco bottles. However, it did have 8 people aswell. It will take 14 hours to get there from London as the max safe speed is 60-65mph, some new ones are limited to 60mph. Unfortunatly, as I organised a trip last year I had to delegate the driving of the van and had to drive an automatic, air conditioned Audi

It only took 10 hours.

jd

January 15th, 2007, 02:06 PM	#1 (permalink)
GLOC(Offline) Moderator Join Date: Nov 2005 Location: Fleet, Hants Posts: 1,994	Gas Usage Planning for Expeditions I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco. 1. Pay for He on the boat at 3p per litre (O2 is 1p per litre) 2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!) 3. Take J's/get J's delivered and cascade 4. Take J's/get J's delivered and boost If we fill our own tins with He, the skipper doesn't want it done on the boat but the quayside, O2/air tops will be carried out by him. So, here comes the difficult questions. Once I have worked out the litreage (sp?) of gas required, how do I work out how many J's I need to order if we are going to cascade? There is already one blender on the team but by the time we get there, there should be 3 of us. Finally, how much difference does it make if you use a booster (Haskell?) and does anyone know where we can hire one? Regards __________________ Gareth Images of Life Photography DIR Team Foxturd Travels Underwater and Further Afar If you don't have the time to do something right, where are you going to find the time to fix it? - Stephen King

January 15th, 2007, 02:42 PM	#2 (permalink)
nic_the_greek(Offline) New Member Join Date: Jan 2006 Location: Gosport, Hants Posts: 86	Quote: (Originally Posted by GLOC) I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco. 1. Pay for He on the boat at 3p per litre (O2 is 1p per litre) 2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!) 3. Take J's/get J's delivered and cascade 4. Take J's/get J's delivered and boost If we fill our own tins with He, the skipper doesn't want it done on the boat but the quayside, O2/air tops will be carried out by him. So, here comes the difficult questions. Once I have worked out the litreage (sp?) of gas required, how do I work out how many J's I need to order if we are going to cascade? There is already one blender on the team but by the time we get there, there should be 3 of us. Finally, how much difference does it make if you use a booster (Haskell?) and does anyone know where we can hire one? Regards Firstly, this sort of calculation should be covered in your Blender training - both the TDI and PSAI exams had questions regarding gas planning for expeditions. Speak to your instructor, I'm sure they will help you go through it. Secondly, last year we took a twinset of 30/70. By decanting 75bar in to an e,pty twinset and topping with air to 210bar you'd get a 24/25 mix. Not exactly what you're after but it was good for us and is divable to 45m. Cheers/Nic __________________ "God will forgive them. He'll forgive them and allow them into Heaven. I can't live with that." The Other Place

January 15th, 2007, 03:04 PM	#4 (permalink)
Gary K(Offline) New Member Join Date: Feb 2006 Location: . Posts: 72	Quote: (Originally Posted by GLOC) 1. Pay for He on the boat at 3p per litre (O2 is 1p per litre) 2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!) 3. Take J's/get J's delivered and cascade 4. Take J's/get J's delivered and boost 1. its approx £80 a fill 2. you'd need 4 or 5 twinsets each 3/4. possible but I couldn't find a booster on hire The easiest way for volume would be to take the van over (£100), then collect/get a few of J's delivered and cascade. You certainly wouldn't want to take them with you from down south, think of the vehicle fuel! Working on the 45% He, even if you come back with a reasonable reserve, you'll need a J each Using the booster would help because you can get more out of the J than just equalizing when the J is low but remember you'll also need a drive source. Unless you borrow one, I wouldn't worry about the booster. I suspect a J will cost over £200 up there, so it'll still work out £60 a fill If your going to need that much, I'd have a quiet word with Ian and see if he's willing to do a bulk deal on the He Last edited by Gary K; January 15th, 2007 at 03:12 PM.

January 15th, 2007, 04:45 PM	#7 (permalink)
JS1scuba(Offline) New Member Join Date: Nov 2005 Location: Arizona, USA Posts: 82	Quote: (Originally Posted by GLOC) I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco. Regards We do this ALL the time. First you need to get out of the "perfect mix mode" and put on your "creative mixing in the field cap" Take 2 twinsets. .... fill them with 14/60 trimix full then follow rule of thirds plus a little (always more is better) then top with air to approx 150 bar (do the math on your own) you will end up with about 18/35. Another thing we do is to start one set at 18/45 and the other set is 10/90 we use the 10/90 set as a "sweetener" to set 1 after dive 1 and then top with air (if you have compressor on board) and keep doing this till you are done --- On the deco gas bring deco bottles in 50% and 100% do high helium mix dives with Both deco gases, then top the 50% bottles till you end up with 36% EAN and the 100% bottles you can still use until you reach approx 100 bar then top those to make 50% -- critical to relable on the spot so the cylinders do NOT get confused. As to the rest of your twinsets for nitrox two big bottles of oxygen will make many many twinsets of Nitrox 32% I have traveled with boosters and compressors and all kinds of kit to make all this work and usually we have 10 divers most of which are so hellbent on having a perfect mix we have just made it so that if you want a perfect mix YOU bring all the sets of gas YOU want to have. Otherwise just learn to be a bit creative and a little accomodating and you can have a lot of fun and still do perfect dives. It sure makes it a better evening if you just have to top up some sets with air than to have to dick around (states term) for 5 hours filling and tweaking gas. The key here is to work out your gas plan FIRST and let everyone know what that gas plan is. If they break the gas fill plan by breathing down too much or not starting out with the right start mix then they get stuck with what they get. I had a few folks on a project this past year that broke the gas fill plan and it ended up costing them a bit for all the extra helium we had to use to get them topped. Welcome to getting gas in the field! Cheers __________________ Joel Silverstein, VP, COO www.techdivinglimited.com a division of Scuba Training and Technology Inc. NAUTILUS DIVE PLANNER CYLINDER SPEC CHART

January 15th, 2007, 04:58 PM	#8 (permalink)
GLOC(Offline) Moderator Join Date: Nov 2005 Location: Fleet, Hants Posts: 1,994	Thanks everyone for the thoughts. Hadn't really thought about the AL80/bottom stages but it does sound like it would make things logistically easier to use those. Haven't done the mixing course yet Tricky but will probably do it with Mark Powell when I contact him. A revised plan then: 2 twinsets of 18.45 each with 4 AL80 with 18.45 should give 4 dives per person, 1 twinset of 32% and then 1 AL80 of 50% to start with. (Don't want to crash the van then with that amount of money onboard!) The O2 tops/fills will be done by the skipper rather than piss him off. Looks like 15 twinsets, 25 AL80s, at least 2 scooters, and all the rest of the gear: that should easily fit into the back of a transit Is everyone busy in the first week in September or might you be able to lend some AL80s __________________ Gareth Images of Life Photography DIR Team Foxturd Travels Underwater and Further Afar If you don't have the time to do something right, where are you going to find the time to fix it? - Stephen King

January 15th, 2007, 02:51 PM	#3 (permalink)
PBrown(Offline) New Member Join Date: Nov 2005 Location: Wiltshire Posts: 199	Quote: (Originally Posted by GLOC) I and several others (total 5) are off to Scapa this year for at least 4 mix dives (the remaining 6 being Nitrox) and we have a couple of options with regards to gas availability. Gas planned for use is 18/45 with 50% deco. 1. Pay for He on the boat at 3p per litre (O2 is 1p per litre) 2. Take enough twinsets with gas in them (we are taking a Transit but that could be converted into a LWB transit!) 3. Take J's/get J's delivered and cascade 4. Take J's/get J's delivered and boost We used Air products a couple of years ago & picked them up on the island, it woked well for us, although it did involve a trip to Kirkwell to pick the J's up and then another to drop them off at the end (they might deliver to the quayside now). We already have an account so the price was the same as we pay at home. Quote: If we fill our own tins with He, the skipper doesn't want it done on the boat but the quayside, O2/air tops will be carried out by him. don't forget to factor time into your plans, you will (presumably) need to haul your twins off & back on again (easier at high tide than low tide!) as well as the time for the actual filling. It would be better if the skipper would allow the J's onboard, as you can use travelling time for filling (but I can understand his/her reluctance if you are removing a potential for profit from them). Quote: So, here comes the difficult questions. Once I have worked out the litreage (sp?) of gas required, how do I work out how many J's I need to order if we are going to cascade? I cheat, I allow Simon to work it out for me! Lawrence Orchard wrote a spreadsheet many years ago, which is still vaild, you can download a copy from here: tools Quote: Finally, how much difference does it make if you use a booster (Haskell?) and does anyone know where we can hire one? For one week it would probably be far more hassle than it's worth. I would be surprised if you saved enough to make it worth while. Don't forget you would also need a means of driving the thing. cheers, Paul

January 15th, 2007, 03:11 PM	#5 (permalink)
PBrown(Offline) New Member Join Date: Nov 2005 Location: Wiltshire Posts: 199	Quote: (Originally Posted by nic_the_greek) Secondly, last year we took a twinset of 30/70. By decanting 75bar in to an e,pty twinset and topping with air to 210bar you'd get a 24/25 mix. Not exactly what you're after but it was good for us and is divable to 45m. This is also a good way of doing it, if you can get enough twinsets, or potentially use stages. We did this in France this year, do a dive with a very rich He mix, then simply air top it for the 2nd dive. The stages were great, breath one empty, equalise with a full one, air top both and you now have enough for two more dives. Of course this means you may not be diving standard mixes. cheers, Paul

January 15th, 2007, 03:29 PM	#6 (permalink)
jamesd(Offline) New Member Join Date: Jan 2006 Location: London Posts: 54	Could you not use stages? A twinset and an AL80 of bottom gas should last you 2 mix dives. You can get this filled from your favoured cheap supplier before you go. If you only plan another 2 mix dives you can just get the twinset and stage filled up by the skipper. It may be more slightly more expensive but: you won't have to move J's around, or hire them or phaff you won't have to hire a bigger transit, you won't fall out of favour with the skipper, he will blend the gas for you giving you more holiday I know tech 1 dives who use the twinset and stage and deco bottle approach for diving weekends, particularly when gas is going to be difficult to find. jd

January 15th, 2007, 05:30 PM	#9 (permalink)
neilh(Offline) Haemoglobin on the bus... Join Date: Nov 2005 Location: Barnsley, UK Posts: 1,900	Quote: (Originally Posted by GLOC) Is everyone busy in the first week in September or might you be able to lend some AL80s Gimme a shout nearer the time, but you could probably borrow one from me as you pass through ...in fact you might also be able to borrow the faber 12's as well if that's any use... Last edited by neilh; January 15th, 2007 at 05:31 PM. Reason: Added doubles!

January 15th, 2007, 05:30 PM	#10 (permalink)
jamesd(Offline) New Member Join Date: Jan 2006 Location: London Posts: 54	Hi I would reduce the number of twinsets unless you are determined not to buy any trimix from the boat. 1 twinset, 1 deco bottle and 1 stage should be enough per person. Keep filling the stage, either with trimix for the morning dives or 32% for the afternoon dives. From the plan you describe I would think you should only need 3 12L fills of Trimix onboard. The transit van should take it all. The one I hired last year had only 8 twinsets and 12 deco bottles. However, it did have 8 people aswell. It will take 14 hours to get there from London as the max safe speed is 60-65mph, some new ones are limited to 60mph. Unfortunatly, as I organised a trip last year I had to delegate the driving of the van and had to drive an automatic, air conditioned Audi It only took 10 hours. jd