Gravity Zero MK II User Manual

MK II Oxygen Rebreather

Closed Circuit System

User Manual

Definitions of Signal Word

Used in this Manual

Danger: This words indicates an imminently hazardous situation, which if not avoided, will

result in death or serious injury.

Warning: This words indicates a potentially hazardous situation, which if not avoided, could

result in death or serious injury.

Caution: This words indicates a potentially hazardous situation, which if not avoided, may

result in minor or moderate injury. It may also be used to alert against unsafe pratices.

1. INTRODUCTION

MK II is a new fully closed circuit oxygen rebreather designed by GRAVITY ZERO, Italy, for military and

technical use.

Oxygen Rebreather MK II is one of the most compact and lightest weight fully closed circuit oxygen rebreather

on the market.

A special version, called MK II pro is available on request; this version differs from the standard version MK II

in having an innovative soft shield composed of kevlar-cordura wich keeps and protects the polyurethane

rubber breathing bag from possible cutting and abrasion under special operating conditions.

Figure 1- Fully Closed Circuit Oxygen Rebreather MK II

2. TECHNICAL DATA

Manufacturer: GRAVITY ZERO

Order No 1

Working Principle: cyclic

Breathing Gas: pure oxygen

Cylinder (two type available):

 volume 2,0 litres 2,0 litres

 pressure: 200 bar 200 bar

 material: aluminium alloy steel

Breathing Bag Volume: 9,5 litres

Carbon Dioxide Scrubber : soda lime, about 1.30 kg

Duration: according to workload up to 3 hours

Maximum Depth: 6 metres, (ppO2 1,6 ATA)

Weight: 6 kg, ashore

Dimensions: L 400 mm x W 400 mm x H 110 mm

3. DESCRIPTION

MK II consists of the following main components (see figure 2):

1) Breathing bag. Made with poliurethane rubber sheets high frequency electronically welded. The

breathing bag has been placed in manner to give a small hydrostatic pressure difference as possible,

i.e. low inhalation and exhalation resistance.

2) Cylinder. Two cylinder type are available on request:

a) 1,5 litres/200 bar realized in aluminium alloy for decrease the magnetic level b) 2 litres/200 bar realized in steel alloy

3) Shut-off valve assembly. Open or close the gas flow from the cylinder, includes the manual actuating

type bypass, the pressure reducer and the safety valve

4) Pressure gauge. Test the internal cylinder pressure.

5) Canister. Contains the soda lime wich absorbs the carbon dioxide due to respiration acts. The

canister is made in such way that it becomes completely surrounded by a gas flow that prevents the

soda lime from being cooled down by surrounding water.

6) Hose connector. Carries the inhalation and exhalation hose gases in proper manner to and from soda

lime canister .

7) Inhalation and exhalation hose. Both hoses are provided with non return valves wich control in

proper manner the flow direction.

8) Mouthpiece. The mouthpiece contains a rotary valve wich isolates the circuit from the atmosphere

when it is in closed position. In the open position, the rotary valve supplies the oxygen to the diver.

9) Harness. The harness (neck strap and waist strap) are easy to adjust to desired lenghts.

MK II - Figure 2 , Main Components

MK II - Figure 3, Valve Assembly

4. FUNCTIONAL DESCRIPTION

Rebreather is a simply device that capture and recirculate the exaled breath, scrub out the carbon dioxide

produced by the respiratory functions and add oxygen to replenish what comsumed.

Oxygen Rebreather MK II is a cyclic type fully closed circuit oxygen rebreather.

Instead of a one-way gas circulation, to and from breathing bag as pendular type, the gas circulates in two

separate directions.

During the respiratory cycle the gas circuit is as in figure 4.

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Gravity Zero MK II User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual