Thailands Premuire SCBA & SCUBA diving service centre.


The 'Labyrinth'
Continuous Flow Gas
Blender

Methods of producing
Nitrox / Trimix.

Partial Pressure Blending

Membrane systems.

Continous Flow Blending.

Oxygen Safety.

















Labyrinth Nitrox Trimix continuous flow gas blending panel for making enriched air nitrox up to 40%.
  • Consistent and accurate mixes can be achieved with this aerospace engineered design.
  • Utilizing a patent pending labyrinth design which exploits the turbidity of air to produce a homogenous mix of Enriched Air Nitrox up to 40%;  accurate to 1/10%. 
  • Stainless steel environmentally sealed housing suitable for environments with salty humid air.
  • A cost effective solution for producing Enriched Air Nitrox.
  • All you need is your existing compressor and an oxygen cylinder. 
  • Suitable for use with compressors up to 320L/min pumping rate.
  • Complete with O2 analyzer, O2 regulator / flow meter and 3 metre permeate hose to connect to your compressor.
  • Simple to use, no maintenance required (except for O2 sensor replacement and analyser battery replacement.)
Optional Oxygen shut off solenoid valve available. Should you loose power to the compressor the shut off valve will close and stop the flow of oxygen.
45000THB + VAT
Includes Panel, Nitrox analyser and sensor, Oxygen flow meter / regulator and 3 metres permeate hose.
F.O.B Pattaya.


Methods of producing Nitrox / Trimix.

Membrane systems

Nitrogen depletion membrane for producing Enriched Air Nitrox.

Low-pressure air (100psi-300psi) is fed to the hollow membrane fibers.
All the oxygen molecules pass through the hollow fiber walls but only some of the nitrogen molecules move through resulting in up to 40% nitrox



The  Nitrox Membrane System uses a Semi-Permeable Membrane to produce oxygen-rich air (Nitrox). 

A portion of the nitrogen in air is separated out, producing a Nitrox mixture containing between 24 and 40% oxygen (O2). 

The input pressure to the Membrane System determines the %O2 produced.  The Nitrox is then delivered to a High Pressure (HP) Compressor to fill Scuba Cylinders or Storage Tanks or to a Low Pressure (LP) Compressor for delivery to surface-supply divers. 

The Membrane System requires a source of clean, pressurized, and heated air for separation.  The two most common sources are HP Air Storage Tanks (HP Supply Option) or an LP Compressor (LP Supply Option).  The air must be properly filtered to CGA Grade D or E air quality prior to entering the Membrane System so it will not damage or plug the Membrane fibres. 

Maximum allowable supply pressures are 5000 P.S.I. for HP Supply and 250 P.S.I. for LP Supply.  An Input Pressure Regulator reduces these pressures to acceptable levels for the Membrane.  The air is then heated to a temperature that provides stability over a wide range of ambient conditions and is optimal for membrane permeation.

The heated air then enters the Membrane, which is made up of thousands of miniature hollow fibres running axially through a cylindrical housing.  The walls of these fibres are semi-permeable and designed for different gases to move through them (or permeate) at different speeds.  The resulting gas mixture is known as the "permeate".  As air flows through the hollow fibres, both oxygen and nitrogen permeate through the fibre walls.  The oxygen permeates faster than the nitrogen, which produces permeate with an oxygen content greater than air. 

The gas that reaches the end of the hollow fibres without permeating is almost entirely nitrogen and is discharged.  The flow rate of this discharge establishes the %O2 of the permeate and is factory set via a fixed orifice to contain approximately 44% O2 under all operating conditions. 

The permeate is a concentrated mixture that must be diluted with additional air prior to delivery to the Nitrox Compressor.  It exits the Membrane at ambient to slightly negative pressure and travels into the Mixing Tube, where it mixes homogeneously with filtered outside air. 

The amount of dilution, and thus final %O2, is obtained by adjusting the Input Pressure Regulator.  As pressure is increased, permeate flow increases, air flow decreases, and a higher %O2 Nitrox is produced.  As pressure is decreased, permeate flow decreases, air flow increases, and a lower %O2 Nitrox is produced. 

This relationship between permeate flow and air flow exists because the total of these two flow rates will always equal the intake flow rate demanded by the Nitrox Compressor.  The resulting Nitrox mixture is analyzed for %O2 before delivery to the Nitrox Compressor and again at the point of Nitrox delivery

Membrane system layout

Positive points of a Membrane System.
  • Once initially set up very little maintenance required
  • Simple to use .
  • No high pressure oxygen required
  • Enriched Air Nitrox mix never above 40%
  • Operater does not require Gas Blender Certification
Negative points.
  • Initial costs very high compared to Continuous flow blending.
  • Either a low pressure compressor or high pressure bank is required for the membrane.
  • Cannot be used for producing mixes above 40%