Rebreather Review |
Friday, 07 October 2011 08:33 |
Rebreathers have become an arrow in the quiver of leading Australian cave divers to push the boundaries of Australian cave systems. In this article some of Australia's leading cave and rebreather divers compare and contrast some of the rebreather technology currently available for cave diving. This review of the APD, Halcyon, KISS, Megladon and Mk15.5 rebreathers has now been updated with the addition of four more models: Optima, Poseidon, rEvo, Sentinel. The rebreathers reviewed in this article are: Ambient Pressure Diving, Dive Rite Optima FX, Halcyon RB80, Hollis-Prism 2 CCR, KISS CCR, Megalodon CCR, Mk15.5 CCR, Poseidon MK6 Discovery, rEvo, Sentinal
Ambient Pressure Diving Ambient Pressure Diving currently have a range of four units: the older first generation Inspiration Classic and the Vision family of second generation units, the Inspiration, the Evolution and the Evolution Plus. The classic is still available but is nowhere as popular as the newer second generation Vision units which have the lion's share of the CCR (closed circuit rebreather) market. The Vision family of units have a built-in on board computer that handles the general running of the unit's electronics' and the decompression profile of the dive. These were the very first second generation units to market and as such still hold a substantial lead over other second generation units in the use of computer systems to control the unit during a dive. Advantages
Disadvantages
Further information: http://www.apdiving.com Training: http://www.southerncrossdivers.com.au
Dive Rite Optima FX For the cave and open water diver, this is a nice unit. It is compact enough for most cave diving and hardy enough for any conditions. The handsets are easy to use. However, the biggest reason I chose the Optima was for the scrubber that it uses. The easy to install Micropore solid canister takes about 20 seconds to put into the unit! The fact that it is solid and not granular has some huge advantages. It take away the human error side of packing a canister properly, channeling is impossible and if flooded, there is no possibility of a caustic cocktail. Having a CO2 problem on a CCR is one of the biggest hazards of diving the unit. If you can avoid some of the issues that can cause a CO2 problem, the Micropore canister becomes quite an attractive option. Advantages
Disadvantages
Further information: http://www.diverite.com.au Training: http://www.idcscuba.com.au
Halcyon RB80 The RB 80 was named after the designer Reinhard Buchaly (RB) and 80 after the similarity of the size of the unit to an 80cft cylinder The first prototypes of the RB80 were produced in 1999. The unit became commercially available through Halcyon manufacturing in 2001. To date there have been no fatalities on the unit emphasising its simplistic and safe passive semi closed circuit design. The unit is not constant flow like other common SCR's (semi-closed circuit rebreathers). The bellows has a ratio of 1:10. Effectively for every breath, 1/10th of the gas is dumped off board by the inner bellows mechanism through an OPV (over pressure valve). Subsequently as the gas in the bellows is breathed and passively ejected, the plate at the bottom of the "compressing" bellows eventually hits 2 independent second stage injectors which refresh the bellows with fresh premixed drive gas. This injection is easily heard and monitored by a diver and the gas ejection bubbles are visible to an attentive dive buddy. The counter lung is protected and at the bottom enabling a better WOB (work of breathing). Advantages
Disadvantages
Further information: http://www.halcyon.net/
Hollis Prism 2 Closed Circuit Rebreather My original expectations for the Hollis Prism 2 were not high, however I was pleasantly surprised at how well this unit handled under some heavy usage. For those who remember the Prism Topaz, the new Hollis Prism 2 is a newer, refined version of the old work horse. Hollis has made it clear that they have wanted to keep the main design of the original Prism Topaz as it was such a reliable and hard wearing unit. I got the opportunity to test the unit in some caves in Mexico and Florida. At first I was concerned about the size of the unit, however, it handled quite well in small, tight areas. It is an easy unit to assemble and check. The fact that it is running a Shearwater Predator as the controller is a huge plus for the unit. WOB (work of breathing) is good and compares well to most other front mounted counterlung units. The biggest advantage of the unit is it's reliability. I have dived 80 hours on the unit and I still have not had a single problem with it, which is quite impressive. Advantages
Disadvantages
More information: http://www.hollisgear.com/prodview.asp?id=3 Training: http://www.idcscuba.com.au
KISS Closed Circuit Rebreather The Classic KISS was one of the earliest fully "manual" CCRs developed. The basic principle of operation relies on the mechanical injection of oxygen into the breathing loop, whilst the PO2 (partial pressure of oxygen) is monitored by the diver. A continuous trickle of O2 into the loop through a fixed orifice ensures that the PO2 in the loop is always slowly declining. This means that the diver must be very vigilant in watching their PO2 and intermittently top it up with a manual addition button. If the rebreather is set up correctly, this extra addition can be quite infrequent at constant depth. Advantages
Disadvantages
Further information: http://www.kissrebreathers.com/
Megalodon Closed Circuit Rebreather The Megalodon is an electronically controlled, closed circuit rebreather, using the most common design of central can housing the scrubber and electronics, flanked by the cylinders and with over the shoulder, or (optionally) "around-the-neck" counter lungs. Diver interface is via twin, redundant handsets for controlling and monitoring the electronics plus a head-up display. Advantages
Disadvantages:
Further information: http://www.customrebreathers.com/meg.html
Mk15.5 Closed Circuit Rebreather Approximately 85 of these prototype rebreathers were made by the US Navy in the 1980's, and as such they are not truly a commercially available unit. However most are still in use and if you really want one, they can be picked up second hand. Arguably the most thoroughly tested and most rigorously designed unit available (not many private companies have the resources of the USN!), the 15.5 has proven itself in extreme diving applications (depth, distance, duration). Advantages
Disadvantages
Poseidon MK6 Discovery A recreational unit designed for divers who do not want to be technically challenged. It is simple to use and for no decompression diving, it is designed to facilitate you in the simplest possible way out of a problem the unit might have. Pretty much, if you have an issue, BAILOUT. The BOV is simple to operate. There is only one handset to look at and it does not need to be programmed, no setpoints are inputted by the diver. Ideal unit for the 40m max no deco diver that wants to spend heaps of time worrying about the composition and setting up of their photographic master piece, and less time worrying about how to fly the unit. Advantages
Disadvantages
More information: http://www.diverite.com.au Training: http://www.idcscuba.com.au
rEvo The compact nature of this unit is the main reason for choosing this CCR. As an avid cave diver, this units slimline design and compactness appealed to me the most. It is a great all-round unit but I believe that it's capabilities in the cave environment far exceed other units on the market. It also has a unique scrubber system that is designed to cater for safety. There are two scrubbers so that if one is compromised, the other acts as a safe guard and continues to scrub the CO2. The counterlungs on this unit are also built in to the back of the unit making them more protected and more streamlined. Advantages
Disadvantages
More information: http://www.revo-rebreathers.com Training: http://www.idcscuba.com.au
What a work of art this machine is. The technology that has gone into this beast is awesome to say the least. However, the reason I chose this unit was not for cave diving, well not tighter caves anyway. It is a much larger unit. great for the big long passages of Cocklebiddy, not so great for the tighter passages of Tank Cave. This unit caught my eye because is is a good deep ocean exploration unit. One thing that sets it apart from the others that it has a unique infrared CO2 detector on it. This in itself is one of the most sort after feature on a CCR. The fact that it does not have cables in it but most of it's systems are connected via infrared or fibre optics is a huge advantage as well when you consider that metal does not work well in moist environments. A true life support system, you will also pay a bit more for this unit. Advantages
Disadvantages
More information: http://www.technologyindepth.com/sentinel.html Training: http://www.idcscuba.com.au |
Last Updated on Sunday, 05 August 2012 13:06 |