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Blending Theory. Introduction. Requirements Basics – empty cylinder Basics – partially empty cylinder Calculations Mixing Chart. Requirements. Decide method Assemble equipment Check suitability Need to know: What have in cylinder What want in cylinder What is final mix in cylinder
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Introduction • Requirements • Basics – empty cylinder • Basics – partially empty cylinder • Calculations • Mixing Chart
Requirements • Decide method • Assemble equipment • Check suitability • Need to know: • What have in cylinder • What want in cylinder • What is final mix in cylinder ANALYSE – ANALYSE - ANALYSE
Empty Cylinder • Have: Empty Cylinder • Want: EAN32 to WP 230 bar • How much oxygen? 0.32 x 230 = 73.6 bar O2 in final mix • Top up with air (pPO2 = 0.21) • Calculate O2 content in air top up • Use formula
Formula • To account for top up: Final mix FO2 - Top up FO2 x Fill Pressure Top up FN2 0.32 - 0.21x 230 0.79 = 32 bar oxygen plus 198 bar of air
Calculation • Check calculation: 32 bar oxygen = 1.0 x 32 = 32 198 bar air = 0.21 x 198 = 41.6 Total oxygen in EAN32 @230 bar 32 + 41.6 = 73.6 bar oxygen • Use formula for any top gas • Analyse to check mix
Partially Full Cylinder • Contains air – same as empty • Contains nitrox mix – empty or analyse • Find oxygen remaining in cylinder • Subtract from required oxygen
Calculation • Have EAN34 @70 bar 0.34 x 70 = 23.8 bar O2 • Want EAN32 @ 230 bar 0.32 x 230 = 73.6 bar O2 • O2 wanted 73.6 – 23.8 = 49.8 bar • Fill pressure 230 – 70 = 160 bar • Require 49.8 bar O2 in 160 bar
Calculation • Work out FO2 - use pressure ‘T’ 49.8 = 0.311 160 • Use top up formula 0.311 - 0.21x 160 0.79 = 20.5 bar O2 • Top up with 139.5 bar air
Calculation – check • Check calculation EAN34 @ 70 bar = 23.8 Add 20.5 bar O2 = 20.5 Air @139.5 bar = 29.3 Total = 73.6 bar O2 Want EAN32 @ 230 bar = 73.6 bar O2
Mixing Chart • Mixing chart – Appendix 1 • Oxygen in mix for pPO2 and fill pressure • Use to calculate O2 needed • Use to calculate O2 left in cylinder • Accounts for O2 in air for top up • Removes errors in calculation
Summary We have covered: • Requirements • Basics – empty cylinder • Basics – partially empty cylinder • Calculations • Mixing chart