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Blending Methods. Introduction . Number of techniques Accuracy Cost Availability We will cover Real v Ideal Gases Methods of mixing Comparison. Real v Ideal. Different densities Compression easier with low density Real Gas – different density Ideal Gas – same density
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Introduction • Number of techniques • Accuracy • Cost • Availability • We will cover • Real v Ideal Gases • Methods of mixing • Comparison
Real v Ideal • Different densities • Compression easier with low density • Real Gas – different density • Ideal Gas – same density Blending methods: • Real – calculate densities • Ideal • Used for Nitrox up to 40% • In line analysing
Methods of Blending • Methods of mixing: • Partial pressure • Continuous • Weight • Separation • Premix • COMPRESSOR • Use recommended • Maintain oxygen service
Partial Pressure • Ease of use • Risk • Equipment • Based on proportion of gas • Decanting • Topping up
Decanting • Oxygen cylinder • Decanting whip • Dive cylinder • Valves – non return • Sequence of opening • Fill rate – slowly 5 – 7 bar per minute • Top off with air – good practice
Decanting Decanting Whip
Decanting Oxygen pressure gauge
Decanting Opening supply cylinder valve
Partial pressure • Equipment in oxygen service • Slow process • Hazards • Standing time • Adequate mixing of gases Automated Partial Pressure Mixing • Fully automated • Removes human error
Partial pressure Automated system and control panel
Continuous Blending • Blend before compressor • Oil free compressor • Oxygen compatible lubricants • Analyse before compression UNDER 40% ONLY • Adjust intake of oxygen • Hazards
Continuous Blending • Large quantities gas • Mixes up to 40% • Not need oxygen service equipment • Mixes >40%: • Use partial pressure + continuous blending • Observe oxygen clean & compatible
Mixing by Weight • Can be very accurate • Dependant on scales • Gases weighed • Cylinders weighed • Expensive • Hazards
Gas Separation • Separates gases in air • Produce required mix • No need for oxygen • Unlimited supplies • Methods • Removes nitrogen • Absorbs nitrogen • Expensive • Clean air
Gas Separation Membrane system
Premix • Use premixed gas to create final mix • Decant premix using whip • Top up with air • Requires large storage • No need for oxygen clean equipment • Option for large Clubs • Initial expense • Bulk purchase of gas
Summary • We covered • Real v Ideal Gases • Methods of mixing • Partial pressure • Continuous • Weight • Separation • Premix • Comparison of methods