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Copyright 2012 CFT GAS/1 Gas Management. Copyright 2012 CFT GAS/2 Introduction Recap – Advanced Nitrox Manual calculation prone to error Planning software.

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Presentation on theme: "Copyright 2012 CFT GAS/1 Gas Management. Copyright 2012 CFT GAS/2 Introduction Recap – Advanced Nitrox Manual calculation prone to error Planning software."— Presentation transcript:

1 Copyright 2012 CFT GAS/1 Gas Management

2 Copyright 2012 CFT GAS/2 Introduction Recap – Advanced Nitrox Manual calculation prone to error Planning software Gas required = time x breathing rate x ambient pressure

3 Copyright 2012 CFT GAS/3 Personal Gas Consumption Surface gas consumption RMV Review personal RMV Work-rate & stress Example Dive to 30m, RMV 16 litres/min 4 Bar x 16 l/min = 64 l/min

4 Copyright 2012 CFT GAS/4 Rules On dives: Deeper than 40m Involving decompression Overhead environment Rule of Thirds Gas Reserves Amount x 1.5 – decompression gas Differing RMVs and Gas Supplies

5 Copyright 2012 CFT GAS/5 Gas Management - Example Dive 47m, 30 min RMV 16 l/min (Highest RMV of buddy group) Deco Gas: EAN 39 & EAN 80 Bottom gas 1.4 Bar/5.7 Bar = EAN 24 EAD = 5.7 Bar x 0.76% N 2 = 4.33 Bar ppN Bar ppN 2 /0.79% N 2 = 5.48 Bar = 44.8m (45m)

6 Copyright 2012 CFT GAS/6 Gas Management - Example Using 50/50 Tables, EAD 45m, 30 min Mandatory Deco Stops Depth(m)Stop Time (min)Gas 151EAN EAN EAN EAN 50

7 Copyright 2012 CFT GAS/7 Deep Stops 1st Deep stop (47m + 15m) / 2 = 31m 2nd Deep stop (31m + 15m) / 2 = 23m 3rd Deep stop 23m to 15m < 10m 2 deep stops, 2 min each Leave bottom at 26 min

8 Copyright 2012 CFT GAS/8 Deco Gas EAN 39 from a depth of 31m (ppO bar) EAN 80 from a depth of 9m (ppO bar) Safety Margin Decompression Software

9 Copyright 2012 CFT GAS/9 Example – Bottom Mix Descent & Bottom Phase: Gas Required = RMV at depth x Time 47m = 5.7 Bar RMV at depth= 16 x 5.7 = 91.2 l/min Gas required= 91.2 x 26 = litres

10 Copyright 2012 CFT GAS/10 Example – Bottom Mix Ascent on Bottom Mix: RMV at depth = RMV x Pressure Average pressure = ( )/2 = 4.9 Bar RMV at depth = 16 l/min x 4.9 Bar = 78.4 l/min Time for this ascent = 1.6 min. Gas Required = 78.4 l/min x 1.6 min = litres

11 Copyright 2012 CFT GAS/11 Example – Bottom Mix Total Bottom Mix (EAN 24): 2, = 2,496 litres Rule-of-thirds Add 50% 2,496 x 1.5 = 3,744 litres If twin 10-litre cylinders, total 20 litres 3744/20 = 187 Each cylinder filled to at least 187 Bar

12 Copyright 2012 CFT GAS/12 Example – Deco Mix Ascent & Stops on EAN 39: Ascent 4.1 Bar (31m) to 1.9 Bar (9m) Average pressure = ( )/2 = 3 Bar RMV at depth = 16 l/min x 3 Bar = 48 l/min Time = 2.2 min. Gas Required = 48 l/min x 2.2 min. = litres

13 Copyright 2012 CFT GAS/13 Example – Deco Mix Deep Stops on EAN 39: 31mRMV at depth = RMV x Pressure = 16 l/min x 4.1 Bar = 65.6 l/min Time at stop = 2 minutes 65.6 x 2 = litres 23mRMV at depth = 16 l/min x 3.3 Bar = 52.8 l/min 52.8 x 2 min = litres

14 Copyright 2012 CFT GAS/14 Example – Deco Mix Deco Stops on EAN 39: 15m, 1 minRMV at depth = 16 l/min x 2.5 Bar = 40 l/min 40 x 1 min = 40 litres 12m, 4 minRMV at depth = 16 l/min x 2.2 Bar = 35.2 l/min 35.2 x 4 min = litres

15 Copyright 2012 CFT GAS/15 Example – Deco Mix EAN 39 Required: = litres Rule-of-thirds: x 1.5 = litres (785 litres) 5-litre cylinder 785/3 = 157 Bar (Fill to capacity)

16 Copyright 2012 CFT GAS/16 Example – Deco Mix Ascent & Stops on EAN 80: Ascent 1.9 Bar (9m) to 1 Bar (Surface) Average pressure = ( )/2 = 1.45 Bar RMV at depth = 16 l/min x 1.45 Bar = 23.2 l/min Time = 0.9 min. Gas Required = 23.2 l/min x 0.9 min. = litres

17 Copyright 2012 CFT GAS/17 Example – Deco Mix Deco Stops on EAN 80: 9m, 7 min RMV at depth = 16 l/min x 1.9 Bar = 30.4 l/min 30.4 x 7 min = litres m, 3 min RMV at depth = 16 l/min x 1.6 Bar = 25.6 l/min 25.6 x 3 min = 76.8 litres m, 21 min RMV at depth = 16 x 1.45 Bar = 23.2 l/min 23.2 x 21 min = litres

18 Copyright 2012 CFT GAS/18 Example – Deco Mix EAN 80 Required: = litres Rule-of-thirds: x 1.5 = 1, litres (1,197 litres) 7-litre cylinder 1197/7 = 171 Bar (Fill to capacity)

19 Copyright 2012 CFT GAS/19 Total Gas Requirements Bottom Mix: EAN 24:3,744 litres 2 x 10-litre 187 bar Deco Mix: EAN 39:785 litres 5-litre 157 bar EAN 80:1,197 litres 7-litre 171 bar

20 Copyright 2012 CFT GAS/20 Manual Calculations Laborious, Prone to Error Disastrous Consequences Desktop Software V-Planner – VPM (www.v-planner.com) Ross Hemingway, Eric Baker

21 Copyright 2012 CFT GAS/21 V-Planner Set surface interval Configure button Select the dive profile and mix Select your deco gases Use this button to enter a new depth, bottom time and bottom mix Use this button to enter a new deco gas

22 Copyright 2012 CFT GAS/22 Configure Parameters

23 Copyright 2012 CFT GAS/23 Enter Dive Details Calculate the dive profile

24 Copyright 2012 CFT GAS/24 Deco Profile & Gas Needs You must add 50% to these gas amounts to allow for Rule-of- Thirds.

25 Copyright 2012 CFT GAS/25 Rule-of-Thirds Bottom Mix: EAN 24:2,733 x 1.5 = 4,099.5 (4,100 litres) 2 x 10-litre 205 bar For 210 bar fill: Turn Pressure = 210 x 0.66 = 150 bar Deco Mix: EAN 39:500 x 1.5 = 750 litres 5-litre 150 bar EAN 80:500 x 1.5 = 750 litres 5-litre 150 bar

26 Copyright 2012 CFT GAS/26 Summary Individual gas consumption – RMV Bottom mix Deco mixes Rule-of-thirds Use of software

27 Copyright 2012 CFT GAS/27 Questions?


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