The Jetsam Baby (Nano) Booster

Jetsam Nano (Baby) Booster
By Ian Carruthers

Reproduced with permision from and copyright of www.outlawdivers.org.uk


"The Baby Booster is intended for the travelling rebreather diver and allows both oxygen and diluent tanks to be filled when compressed air is the only source of power available. It will fill rebreather size dive tanks to 200 bar (3000 psi) when the supply tanks are as low as 34 bar (500 psi). With a weight of only 3.2 kg (7 pounds) it is light enough to be conveniently transported by air."

The Jetsam Technology Baby (Nano) Booster.

The Reasoning.

In September 2003 we brought ourselves nice shiny Inspirations, having just finished a season of Trimix diving and mixing all our own gases we had plenty of Oxygen. However once we had use a bit we rapidly ran out of pressure and had three J's of Oxygen at 100 bar, which was a bit of a pain. So early 2004 saw me looking at the Jetsam Technology Baby (Nano) Booster, after an email conversation with Gordon Smith of Jetsam Technology, I decided that it would be nice to have a little booster.

The Booster.

At the end of the summer I had a booster pump. When you get a Baby Booster from Jetsam you have the options of getting whips with it. I decided to source my own in the UK so that I had UK spec hoses which I could replace next day. So after ordering more bits from Sub Aqua Products and cannibalising my decanting whip, I had my hoses. At this point I still couldn't use the booster as it has ¼ NPT fittings and my hoses are ¼ BSP, so I needed adaptors. These I found at Braided Steel Racing Products . Now I had two ¼ BSP - ¼ NPT adaptors, two 2m hoses, two pressure gauges, two bleeds, a needle valve, two DIN ends and of course my booster.

With all the bits assembled I ended up with a DIN input with pressure gauge through a non return valve through a needle valve into the inlet hose. Then I have the booster which feed out to outlet hose to a DIN fitting with a large pressure gauge.


In Use.

OK so enough of the technical bit you want to know how well it works. Well I started a fill in my 3 Litre Oxygen cylinder with 150 bar and 140 bar in my 10 litre source cylinder. I filled the 3 to 245 bar which took my 10 litre down to 110 bar, this took 60 bar from a 12 litre cylinder and about 10-15 mins. On a trip with Open circuit divers as well we did a weeks diving with the five OC Divers on 32% and three CCR divers each evening it took between one and two hours to fill all the oxygen needed for the fills three litres from 140 to 200 bar and ten 10-12 cylinders from 50 to 90 bar. All of these fills were done with donor pressures of less than 130 bar and typically used about a 12 litre of air to drive the booster.

The Theoretical bit from Gordon Smith.

"If the fill tank pressure is near the maximum (approximately 3200 psi/218 bar) each stroke will use 176.7 cubic inches (2.9 litres) of drive gas no matter what the supply tank pressure may be. If the supply tank pressure is 3000 psi (204 bar) the pumping efficiency would be approximately 90%. If the supply tank pressure is 500 psi (34 bar) the pumping efficiency will be approximately 12% and the drive gas consumed would still be 176.6 cubic inches (2.9 litres) per stroke.

Consider the situation from a mechanical perspective:

If the fill tank pressure is 3000 psi (204 bar) and the supply tank is 2000 psi (136 bar) the high pressure cylinder of the booster will be filled to a pressure of 2000 psi (136 bar) at the beginning of the compression stroke. The total stroke length is 2.5 inches (63.5 mm). The piston will travel .83 inches (21 mm) in order to raise the pressure in the booster cylinder enough to equal the pressure in the fill tank. Only then will the booster begin to transfer the gas into the fill tank.

If the supply tank pressure is only 500 psi (34 bar) the piston will have to travel 2.1 inches (53 mm) before it can begin to transfer the gas into the fill tank. But in both cases the drive gas consumed will be the same.

To take the situation to the extreme:

The booster will continue to cycle with a supply pressure of only 73 psi (5 bar). At this pressure NO gas will be pumped into the fill tank. But if the fill tank was at 3000 psi (204 bar) the booster would still use 2.9 litres of drive gas per stroke."

Transportability

With the booster weighing only 3.2kg transportability is easy, complete with hoses, adaptors and carry case mine weighs in at just less than 10kg. The small size and the gas power mean that it can be operated anywhere mine is quite often use out of the back of my car.


SPECIFICATIONS:

Weight.................................... 3.2kg (7 lbs)
Dimensions.............................110mm X 110mm X 300mm
Drive cylinder displacement....... 0.29 Litres (17.67 cubic inches)
High pressure cylinder displacement.. 0.0126 Litres (0.767 cubic inches)
Pressure ratio..........................23:1
*Note this is a mathematical ratio only; actual pressure ratio will be less due to seal friction, dead space and gas compressibility
Maximum drive gas pressure..... 10 bar (147 psi) Air only!
Maximum boost pressure..........@ 10 bar (147 psi) = 218 bar (3200 psi)
Boost ratio................................5:1 with air, 3:1 with Helium

Manual

The manual is avaliable on the Jetsam website HERE


Discuss this article HERE