O2 Clean, VIP, and Hydro

[Mark Vlahos]

Hi,

I am getting ready to purchase some tanks that will do double duty. I am planning on purchasing 2 AL80's and 1 AL40. The AL80's will be used as back gas for recreational dives and deco bottles for decompression dives. The AL40 may be used as a pony for recreational dives when required by some area dive boats, and will be used as an oxygen bottle for deco dives.

The tanks will be purchased new with O2 clean cylinder, valve, and lubricants and will have a VIP sticker to confirm this. I plan on always using O2 compatible air or partial pressure blended NITROX.

My question is about the long term costs of tank ownership.

If I have been vigilant and NEVER used "dirty" air will Visual Inspections be any different, either in the work performed or the cost, on my O2 clean tank than they would be on a normal air tank? What about Hydro on this tank?

If I have been vigilant will I need to do any special inspections to maintain the O2 clean nature of the tank? I understand that when the valve is maintained it needs to be done with oxygen compatible parts and lubricants.

I expect that when it comes time to fill the 40 with oxygen as a deco gas the tank will need to be emptied, and then refilled with oxygen so the nitrogen content is next to nothing. Are there any inherent problems with my plan?

Tanks are expensive and I don't want to spend the money for dedicated tanks for each of the purposes if I don't need to.

Many thanks,

Mark Vlahos

 

[DA Aquamaster]

An AL 80 is an awful big deco bottle. A pair of AL 40's is a better choice for deco than a single 80 as you can then have 2 separate deco gases along (like 50% and 80% or 100% O2.) A pair of AL 40's will get you through at least 3-4 dives with moderate deco requirements (150'-170' for 25 minutes for example).

If you are doing dives where an AL 40 is not enough, you are diving really deep, really long, or on an extended expedition with no air or O2 available on the boat.

My feeling is that O2 clean tanks should be O2 cleaned annually. Contaminants tend to build up over time as few compressor/filter systems are perfect. Despite the religeous zeal that some folks express about O2 cleaning procedures, O2 clean is really only a relative term, particularly after the tank has been in service several months and refilled numerous times. Most shops I have seen that apply an O2 clean sticker give it a 12 month expiration date anyway.

VIP costs and hydro tests costs will be the same, it's just the O2 cleaning that is extra.

Locally a hydro costs $15.00 and includes the VIP and an air fill. Your best bet money wise is to work directly with the hydro test facilty for the hydro as dive shops tend to have a bad habit of charging $30 to $50 for a $15.00 hydro.

Filling a 100% O2 tank with 100% O2 does not require it to be emptied. If it has 100% O2 in it, you can just top it off. BUT practices vary depending on the shop. Some shops, particularly those that partial pressure blend Nitrox and transfill the O2, prefer the tank be empty when they start as sort of a hold over from the way they blend Nitrox.

 

[SDAnderson]

If I have been vigilant and NEVER used "dirty" air will Visual Inspections be any different, either in the work performed or the cost, on my O2 clean tank than they would be on a normal air tank? What about Hydro on this tank?

I don't see any reason why a viz or a hydro should be any different or cost any more, simply because it's an O2 ready tank. For instance, there is nothing in the PSI inspection protocol that differentiates between an inspection on an O2 clean cylinder and an air cylinder. Some folks advocate blacklight inspections but there are a bunch of issues with the technology and methodology that make them mildly dangerous and prone to a high number of false positives. Though I'm not qualified to directly address the hydro question, I've never heard of a hydro facility altering either it's protocol or price to test an oxygen ready tank.​

If I have been vigilant will I need to do any special inspections to maintain the O2 clean nature of the tank? I understand that when the valve is maintained it needs to be done with oxygen compatible parts and lubricants.

No. See "blacklight", above.​

I expect that when it comes time to fill the 40 with oxygen as a deco gas the tank will need to be emptied, and then refilled with oxygen so the nitrogen content is next to nothing. Are there any inherent problems with my plan?

I think O2 bottles should be dedicated. Some contamination is almost inevitable whenever you fill from a compressor and that, combined with high pressure oxygen, is a recipe for disaster. So long as you keep your cylinder labels accurate, I don't have any issues with multi-tasking other bottles.​

Tanks are expensive and I don't want to spend the money for dedicated tanks for each of the purposes if I don't need to.

I hear that. A few things to consider, however:

The aggravation factor of having to re-label your cylinders everytime you switch mixes is going to be a consideration in your plan. Standard cylinder MOD markings can be done with a magic marker and duct tape, but it makes a mess and takes time and care.

Then there is the issue of converting the tanks from back gas singles to stage/deco bottles. Removing and replacing the rigging, as well as changing the MOD markings, is going to be a pain in the patoot.

Don't forget the cost of O2 servicing your tanks and valves. I clean mine at least annually or anytime I've had a fill from a fill station that I don't trust. You can DIY, but it takes some special training, equipment, supplies and parts. Not to mention a blown weekend about this time every year...​

 

[Mark Vlahos]

An AL 80 is an awful big deco bottle. A pair of AL 40's is a better choice for deco than a single 80 as you can then have 2 separate deco gases along (like 50% and 80% or 100% O2.) A pair of AL 40's will get you through at least 3-4 dives with moderate deco requirements (150'-170' for 25 minutes for example).

If you are doing dives where an AL 40 is not enough, you are diving really deep, really long, or on an extended expedition with no air or O2 available on the boat.

My feeling is that O2 clean tanks should be O2 cleaned annually. Contaminants tend to build up over time as few compressor/filter systems are perfect. Despite the religeous zeal that some folks express about O2 cleaning procedures, O2 clean is really only a relative term, particularly after the tank has been in service several months and refilled numerous times. Most shops I have seen that apply an O2 clean sticker give it a 12 month expiration date anyway.

VIP costs and hydro tests costs will be the same, it's just the O2 cleaning that is extra.

Locally a hydro costs $15.00 and includes the VIP and an air fill. Your best bet money wise is to work directly with the hydro test facilty for the hydro as dive shops tend to have a bad habit of charging $30 to $50 for a $15.00 hydro.

Filling a 100% O2 tank with 100% O2 does not require it to be emptied. If it has 100% O2 in it, you can just top it off. BUT practices vary depending on the shop. Some shops, particularly those that partial pressure blend Nitrox and transfill the O2, prefer the tank be empty when they start as sort of a hold over from the way they blend Nitrox.

The choice for the AL80 as a deco bottle is to provide adequate gas on multiple dives with an acceptable reserve if on the last dive my buddy suffers a gas loss and needs my deco gas. I do plan on having the lighter blend, somthing in the 50% to 80% range - depending on the planned profile for the dives involved, in the larger tank and 100% O2 in the 40.

It is starting to look like the AL40 needs to be dedicated and the AL80's can do double duty. What are typical costs for O2 cleaning on tanks used as I have described? I certainly understand that prices will vary widely, just an estimate is fine. I have always rented tanks and will continue to rent doubles for backgas as the costs on these are still a little too rich for me at this time.

Many thanks,

Mark Vlahos

 

[Mark Vlahos]

I think O2 bottles should be dedicated. Some contamination is almost inevitable whenever you fill from a compressor and that, combined with high pressure oxygen, is a recipe for disaster. So long as you keep your cylinder labels accurate, I don't have any issues with multi-tasking other bottles.​

Tanks are expensive and I don't want to spend the money for dedicated tanks for each of the purposes if I don't need to.

I hear that. A few things to consider, however:

The aggravation factor of having to re-label your cylinders everytime you switch mixes is going to be a consideration in your plan. Standard cylinder MOD markings can be done with a magic marker and duct tape, but it makes a mess and takes time and care.

Then there is the issue of converting the tanks from back gas singles to stage/deco bottles. Removing and replacing the rigging, as well as changing the MOD markings, is going to be a pain in the patoot.

Don't forget the cost of O2 servicing your tanks and valves. I clean mine at least annually or anytime I've had a fill from a fill station that I don't trust. You can DIY, but it takes some special training, equipment, supplies and parts. Not to mention a blown weekend about this time every year...​

Your point about a dedicated O2 bottle is a good idea and perhaps I had not considered the problems involved in this enough, so I will think on it some more. I am now leaning more toward dedicating the 40 for 100% O2. If the dive operators get sticky about wanting all divers to carry a large pony, well then I might find it necessary to get a separate cylinder for that purpose.

Your point about the hassle regarding rerigging and relabeling is somthing I had considered and is somthing I am willing to put up with until I can afford dedicated tanks for all tasks. I am slowly getting into technical diving and the gear costs are consderable, as I am sure you know.

My long term plans are for dedicated regs for doubles, and dedicated tanks. I have some of the gear now and I am slowly getting more, I just want to spend the money only once. If I can get gear that will do double duty now and become dedicated to a single task later I will save moeny in the long run.

Mark Vlahos

 

[DA Aquamaster]

The choice for the AL80 as a deco bottle is to provide adequate gas on multiple dives with an acceptable reserve if on the last dive my buddy suffers a gas loss and needs my deco gas. I do plan on having the lighter blend, somthing in the 50% to 80% range - depending on the planned profile for the dives involved, in the larger tank and 100% O2 in the 40.

It is starting to look like the AL40 needs to be dedicated and the AL80's can do double duty.

I hear your concern about wanting a reserve supply of deco gas for the buddy, but carrying an 80 just for that rare eventuality, in my opinion, involves a lot of uneccesary inconvenience.

Personally, I always make a contigency plan to anticipate the loss of one deco gas. On dives where I am planning on only using 50%, I will include a contingency profile to do the deco on my backgas and ensure that my reserve will be adequate to cover the deco requirement. The same planning covers the buddy. If he/she screws up and needs my deco gas, I can either share it with him or her (volume permitting) or hand it off (volume not permitting) and do my own deco on my backgas. Afterwards, we can have a nice discussion about how he/she got in that predicament in the first place.

Buddy selection is obviously a factor. If my buddy does the same thing in terms of planning and redundancy that I do (ie: plan to remain self sufficient rather than depend on your buddy for redundant deco gas) then the odds of ever having to get to the point of having to share or give away my deco gas is remote.

If the dive profile gets so long and deep that a 1/3 reserve will not accommodate the deco requirements it's an automatic argument for bringing along a second deco bottle and it just makes more sense to have a hotter mix in it to keep things efficient. Along with this I will do contigency plans to complete the deco with only one or the other of the deco gasses and ensure that 40 cu ft, in conjuction with the 1/3 rd backgas reserve, is enough to accomplish the deco required.

You can increase the redundancy even more, but the logic of doing so usually implies that you are planning to have multiple failures or are planning to get seriously off your dive plan.

You also need to consider the profiles involved. You may find that 40 cu ft of O2 will not be adequate to keep up with 80 cu ft of 50% over the course of several dives and that on that last critical dive, there may not be enough O2 for both of you. That will then require a hotter mix in the 80 to adjust the gas use form each tank and conserve O2 per dive. In the end it may mean compromising efficiency on all your dives in anticipation of an event that should not even occur if your buddy has his/her stuff together.

Given the relative cost of 40's and 80's you get more bang for the buck with an 80 in terms of gross volume, but all things being equal, I'd rather take along a pair of 40's than a single 80. There are lots of factors to consider and while there are a lot of potentially valid arguments either for or against using an 80 or a 40 for a deco bottle, saving money should not be one of them.

 

[jbd]

What are typical costs for O2 cleaning on tanks used as I have described? I certainly understand that prices will vary widely, just an estimate is fine.

Seems like I have seen prices ranging from $30 to $40 which included the fill(standard nitrox) after the cleaning.

 

[ScubaDadMiami]

The added expense of dedicated tanks is not a big deal. If that is the only consideration, then get dedicated tanks and you can always use them in any diving environment.

On the other hand, if you are doing a lot of traveling with your tanks, you will need to make sure that any fills to your tanks along the way will not contaminate them, then requiring that you get them cleaned all over again.

You really will not need for your back gas regulators to be suitable to oxygen service. You really only need dedicated regulators for your deco bottles (assuming you are going with standard mixes).

 

[SDAnderson]

What are typical costs for O2 cleaning on tanks used as I have described?

Prices will vary depending upon the quality of the work being done and the geography. Places that tumble with media and blow steel tanks dry with nitrogen and clean valves in an ultrasound are going to charge more than shops that air dry tanks and scrub valve parts by shaking them in a peanut butter jar full of dish detergent. In some areas its hard to find a shop that will do the work, let alone do it right - for instance, in all of metro Chicago there are only a couple that are even willing to do the work. Prices around here for a good job run about $50 - $60, including stickers and an air fill. (The fact that the price has less to do with greed than rents and labor costs doesn't mean that it doesn't hurt.) DIY to do it properly will cost a little over $1000 for the equipment, training and enough supplies to clean a whole mess of tanks.

Yoikes! It makes the aggravation of multi-tasking a tank a lot less painful.

 

[Mark Vlahos]

The added expense of dedicated tanks is not a big deal. If that is the only consideration, then get dedicated tanks and you can always use them in any diving environment.

On the other hand, if you are doing a lot of traveling with your tanks, you will need to make sure that any fills to your tanks along the way will not contaminate them, then requiring that you get them cleaned all over again.

You really will not need for your back gas regulators to be suitable to oxygen service. You really only need dedicated regulators for your deco bottles (assuming you are going with standard mixes).

I guess I was not clear enough, sorry, my bad.

By dedicated regs I meant specific regs set up for doubles (long hose) but configured for the double tanks, and another reg setup as my standard recreational setup (also long hose) but with two second stages on one first. Getting out the wrench is what I do now but I do not want to do this forever. I do plan on dedicating regs to oxygen service where it is warranted, i.e. deco bottles.

Sorry for the confusion.

Mark Vlahos