Dräger SM 1 semiclosed rebreather

Selfmixing Swim apparatus

This unit is equipped with an oxygen and an air bottle. Both bottles have a volume of 1,5 ltr and 200 bar working pressure. Mixing the oxygen and air is done automatically by using orifices. The mix is changing with the depth. The carbon dioxide exhaled by the diver is removed chemically by the scrubber. The cleaned air is mixed with the ait-oxygen mix that is injected in the loop. The design is made in such way that 2 ltr/min oxygen consumption of the diver is possible. The lower fraction of oxygen pressure is restricted to 0,2 bar. When the diver uses 0,5 ltr oxygen per minute the unit will not provide gas with a higher partial pressure of oxygen above 2.0 bar. During a common use of 1,3 ltr/min oxygen consumption, the partial pressure of oxygen will be around 1,5 bar.

Oxygen is added by means of a first stage regulator with a fixed IP of 9 bar. Resulting in a constant oxygen flow of 2 l/min independent of the depth! Air is added by means of a depth compensated first stage regulator AND a second stage regulator reducing the IP being 0,5 above ambient pressure. (depth compensated). The gas is mixed in a mix tube before entering the loop. The system in supplied with two electric switches who guard the pressure between the restrictors, in this way warning the diver when the gas flow stops.

DATASHEET SEMICLOSED REBREATHER
Dräger SM 1	Date: 11 April 2005
Selbstmischendes Mischgas-Schwimmtauchgerät SM1	Database semi closed rebreathers by: J.W. Bech
Manufacturer	Dräger
Designer
Model	SM1
Land of origin	Germany
Design year	1962?
Special Note:	Rare rebreather
User group	Military
Magnetic characteristics	Non Magnetic/ Acoustic
Part no:	4220-12-140-9197
Working principle	Constant Mass Flow	Oxygen 2 ltr/min – Air 2,2 ltr/min
Gas type	Oxygen – Air
Oxygen is added by means of a first stage regulator with a fixed IP of 9 bar. Resulting in a constant oxygen flow of 2 l/min independent of the depth!
Air is added by means of a depth compensated first stage regulator AND a second stage regulator reducing the IP being 0,5 above ambient pressure. (depth compensated).
The gas is mixed in a mix tube before entering the loop. The system in supplied with two electric switches who guard the pressure between the restrictors, in this way warning the diver when the gas flow stops.
Intended use	Military
Dimensions LxWxH	640 x 420 x 270 mm
Device weight	In Air 25 kg in water 4,0 kg
Intermediate Pressure	9 bar 02 fix/ Air Pamb+0,5 bar
Overpressure valve	15 cm water Colum
Max depth	40 meters	(metres)
Used material for housing/backplate	glass fibre
Pressure reducer	Oxygen, fixed, Air depth compensated	Air 2 staged pressure reduction 10bar – Amb+0.5 bar
Connection reducer – bottles	Oxygen cylinder with inside thread, Air outside threat	Aluminium bottles 1,5 ltr max 200 bar
Supply pressure	200 bar, minimum 30 bar
Umbilical connection	No
Color of cilinders	Air : Gray, Oxygen: Blue
Manual bypass	Yes, by pressing lever both gasses are added
pO2 measurement standard	No	Lamp guarding gas flow
Pressure gauge range	0-200 bar	Lamp fitted in mask
Cylinders	2 x 1,5 liters
Cylinder material	Non-magnetic
Cylinder thread	G 5/8” inside and outside
Valve	T-shape
Designed for gas type	Selfmixing
Co2 absorption cartridge capacity	2,1  liters
Co2 absorption cartridge rechargeable	Yes
Co2 absorption cartridge storage time	no data	(month/year)
Co2 absorption time testing (CE)	No
Connections Co2 cartridge	The scrubber is fixed in the rebreather housing
Guaranteed absorption time	100 minutes @ 10 meter
Grade of absorption material	no data
Breathing bag material	inside rubberized
Inhale bag volume	no inhale breathing bag
Exhale bag volume	10 liters fixed between exhale side and scrubber
Total loop Volume	Total volume 11 liters
Operating temperature	no data
Magnetic signature	low
Colour (s)	green
Worn	On the back
FFM attached	Yes	(mask)
Mouthpiece valve	Yes
Extra info:	Low acoustic signature
Safety device	The unit comes with a double pressure switch. In case pressure of one of the gasses drops below a certain safety level the switch turns on a small lamp in the divers mask. You can see the small cable fixed on the mask.
Additional information:	http://www.teknosofen.com/draeger_sm_tech.htm
Email address owner:
URL owner:
If you have any information to add this sheet please mail it to jw.bech@quicknet.nl References to source and names will always be added!
Info found: Ake Larsson, Tauchtechnik G. Haux, Original Manual Dräger SM1 kindly offered by Nautiek Diving Netherlands
Origin: http://www.therebreathersite.nl
Info:
The unit is equipped with an oxygen and an air bottle. Both bottles have a volume of 1,5 ltr and 200 bar working pressure. Mixing the oxygen and air is done automatically. The mix is changing with the depth. The carbon dioxide exhaled by the diver is removed chemically by the scrubber. The cleaned air is mixed with the ait-oxygen mix that is injected in the loop. The design is made in such way that 2 ltr/min oxygen consumption of the diver is possible. The lower fraction of oxygen pressure is restricted to 0,2 bar. When the diver uses 0,5 ltr oxygen per minute the unit will not provide gas with a higher partial pressure of oxygen above 2.0 bar. During a common use of 1,3 ltr/min oxygen consumption, the partial pressure of oxygen will be around 1,5 bar.
Example: Suppose the diver dives to 10 mtr depth and has filled his loop with gas. The starting percentage of the loop is 50% of oxygen. When using 2,0 ltr/min (graphic 1) after 30 minutes the oxygen % will drop to 20% and reaches the lower limit. At 10 mtr water depth the loop lower limit is 10%. When using 2,5 ltr/min this lower limit is reached in 20 minutes (graphic curve 2). When using 3,0 ltr min in 10 min the lower limit is reached.

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