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Dear Divers: I just was made aware of this mail list and would like to respond to some of the questions/comments that have been made. First of all, the X-tra System is intended for the recreational diver who would like to have a pony bottle backup system. Diving test and the calculations show that 6 cu ft. is only enough air for a safe assent from about 100 ft. 13 cu ft. (which is offered along with 19 and 30 cu ft cylinders) would address deeper diving situations or specialty dives. The X-tra system can be used like any other pony bottle if desired with the main advantage in this case being an easy filling system and a low profile combination valve/1st stage regulator. In this situation, two Scubapro high pressure disconnects are used on each end of the fill line and the X-tra system is detached from the main system. This is how I expect the larger cylinders (19 and 30 cu ft) two be used for cave divers and other specialty divers. The standard (recreational) application for X-tra is to leave the high pressure transfer line hooked up all of the time. This has many advantages and one potential disadvantage. If any thing happens with a diver's primary system or any of the high pressure lines, X-tra is isolated and supplies a bailout supply. The transfer line insures that X-tra is topped off on repetitive dives and provides that the entire air supply is available in the event another diver needs your safe second. By attaching X-tra to the power inflator, the diver knows that the pony bottle regulator is always working (auto-checking) and air is available. No more pony bottles that have leaked down or had a regulator full of sand without the diver knowing. The bad part of having a transfer line is that if something happens to cause X-tra to free flow or leak, then the total air supply could be lost. During recreational diving situations, a diver is likely to notice an unstoppable massive leak or a free flow and should start an ascent immediately. The good news is that no matter what happens with the X-tra system the maximum air loss rate is the same as the fill rate of about 6 cu ft. per minute or about 250 psi of an 80 cu ft. cylinder per minute, and most divers could deal with this situation by making a controlled ascent. The X-tra system can give redundancy without complexity. If a diver uses an Air2 or other combination safe second/power inflator then the redundant system has only one hose into the pony bottle and one hose out. Only one low pressure hose (to possibly fail) out side of the backup system. To answer the serious technical questions: 1. Aquavit, Inc. makes the first stage regulator that includes the check valve and PIN pressure gage. The regulator is a piston type with depth intermediate pressure adjustment and is very much like a Scubapro MK2. The intermediate pressure can be adjusted with shims to give about 125-145psi as desired. I prefer about 130psi to avoid free flows. Service kits are available and X-tra can be serviced by anyone experienced in normal regulator maintenance. All X-tra units are pressure and leak tested and adjusted for intermediate pressure. Jan Troup, President Aquavit, Inc. email: aquavit@aq*.co* -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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