There are many different rebreather manufacturers in the world and everyone will tell you that their own units are the best that are available. You’d expect that though wouldn’t you?
The problem with rebreather manufacturers is that once that they have designed and built their rebreathers they then need to test them.
Testing is expensive and you have to initially test it by diving it yourself. It is possible to use breathing machines that simulate breathing and carbon dioxide production these machines can be pressurised to depth but they are very, very expensive to use and almost impossible to buy for the fledgling manufacturer. Without the breathing simulators the only choice is to take it and dive it. Once the manufacturer is happy with their own test dives they then produce a small number of rebreathers and sell them. The divers that buy them are aware that they have a new unit and that there may be teething troubles and that in effect they are undertaking a form of test. This is known as “Beta testing”.
rEvo rebreathers invested in their very own breathing machine known as an “ANSTI” machine. There are very few of these machines in the world and the benefit that it has to a manufacturer is that tests can be undertaken in a controlled environment and data collected digitally. No divers are at risk in testing equipment.
rEvo don’t just test their rebreathers in the ANSTI machine but they also test the carbon dioxide absorbant materials to ensure what they recommend is the very best available.
The tests are carried out in all conditions and there is nothing left to chance. Before any new rEvo leaves the factory it undergo's a 120 different tests.
The look of the rEvo is quite different to any other rebreather and that is because it uses two carbon dioxide absorbent material canisters instead of one. The benefit of using two canisters is a topic in it’s own right.
The owner and designer of rEvo Rebreathers is Paul Raymeakers and he doesn’t just produce rEvo rebreathers he is also an avid diver of them. Unlike many other manufacturers, when there is a chance of a rEvo being used in a record breaking dive, Paul doesn’t expect some other diver to attempt it, he goes himself on his own rebreather that he designed and manufactured. He has the upmost belief in his product and this was apparent when he took a standard rEvo to 212 metres in Dec 2009.
Paul is not simply a manufacturer who just wants to sell units, you can always contact him with any questions, problems or suggestions and he always replies. It’s a really big factor for many divers who have trusted their lives to a rEvo rebreather.
In a perfect world we only need one cell. However in reality we cannot trust that one cell is giving the correct information so we need more cells to verify. Two cells is no good because if you have one good and one bad you don’t know which is giving the correct information and which is not. You cannot be sure which is correct.
Most rebreather manufacturers have decided that three cells is the right amount because if you have three cells you can take the two closest cell readings as being correct and rule out the remaining cell. That works fine but what if two cells fail together? Research has shown that cells of the same batch that have the same dive history are far more likely to fail together. This means that three cells fitted at the same time from the same batch gives a higher probability of two cells failing together. Thus the two failed cells will out vote the good cell.
rEvo rebreathers can have up to 5 cells. This gives the diver the information that he needs to make an informed judgement on the readouts from the Cells. The diver will then know if there is a cell going out of range and the decisions are left with the thinking diver who understands what is happening and not to the programming on a computer.
The first step in the production process is to cut and fold the steel or titanium chassis (the case). If we take the stainless steel unit as a standard then the raw material is laser cut. It’s not just a matter of placing stainless steel on a machine as there are two different types of stainless steel used in the manufacture. A hardened stainless steel is used for the feet and for the other parts that are subject to stress. The chassis are made from 316 Stainless steel in production runs of 10 to 20 at a time.
When the cutting has taken place with lasers there are no burs on the steel , just to give the edges a more smooth feel however, the large pieces are all hand finished and polished and the smaller ones are tumbled in a machine with a substance that smoothes and polishes the components.
The chassis are then folded with a CNC folding machine and this guarantees the accuracy. Each case is precision folded to ensure a perfect fit on assembly. Before the polished pieces can be folded they are protected to ensure that there are no marks from the folding process.
The other metal parts required are all machined and all the plastic parts are machined from solid Delrin.
The counter lungs are computer laser cut from bio compatible polyurethane, and then manually high frequency welded in a 3D box shape which utilises all of the free space within the chassis.
The rEvodreams and HUDs are milled from solid Delrin and the circuit boards and displays are all assembled in house. All of the wiring is undertaken in house. The Molex connectors are assembled and soldered according to rEvo specifications. First the bare cables are coated with liquid solder (tinned), then they are crimped using an Exact tool, finally they are soldered to make a permanent connection between cable and Molex pin. All of the entry and exit points of cables are potted to ensure no water ingress.
At first glance the first stages appear to be Apex DS4s however on closer inspection the reveal that they are in fact specifically manufactured by Apex for rEvo (DS4-rEvo) with two high pressure ports and different orientation of the ports to ensure smooth hose routing.
Shearwater computers are bought in from Shearwater Research but the solenoid controllers and battery compartments are all manufactured in house and machined from Delrin to the same exacting tolerance. All of the components are pressure tested.
The manual addition buttons all have double springs on them which helps to prevent them from sticking.
Oxygen cells are not made in house but bought in from specialist manufacturers. These cells however, are not just taken and fitted into the units. Each cell is taken out of the sealed bag which is carefully opened and is subjected to 5 dives where the performance of each cell is measured and only when it has passed all of the tests does it get placed back into the original bag and is then hermetically sealed ready for installation. The cells that are rejected are returned to the manufacturer.
On assembly the counterlungs are connected to the scrubbers and then placed in a protective liner before being fixed inside the chassis. The gas system and electronics are then fitted. All throughout the production process there are checks to ensure the quality and the whole breathing loop is put under negative pressure. This test is done by closing all of the ports then vacuuming out the gas with a small machine to minus 120mb. Pressure is then increased to minus 40mb where a split time stop watch comparison is carried out on a digital device.
When the unit is fully assembled yet before it is packed and shipped off to the customer there is a 120 point quality control check. This final check is not undertaken by the person who assembled the rebreather but one of their colleagues who have had no input into the assembly process of that particular unit.
This rebreather has been manufactured and assembled to the highest standard with the upmost care and attention and the people who build these are all qualified to dive them.
It’s not just any rebreather it’s a rEvo rebreather.