# Blending Theory - PowerPoint PPT Presentation

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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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Blending Theory

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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

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